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{{Glaucoma}}
{{Glaucoma}}
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==Overview==
==Overview==
[[Glaucoma]] is a group of diseases affecting the [[optic nerve]] that results in [[vision loss]] and is frequently characterized by raised [[intraocular pressure]] (IOP). There are many glaucoma [[surgery|surgeries]], and variations or combinations of those [[surgery|surgeries]], that facilitate the escape of excess [[aqueous humor]] from the eye to lower [[intraocular pressure]], and a few that lower [[IOP]] by decreasing the production of [[aqueous humor|aqueous]].
[[Glaucoma]] is a group of diseases affecting the [[optic nerve]] that results in [[vision loss]] and is frequently characterized by raised [[intraocular pressure]] (IOP). There are many glaucoma [[surgery|surgeries]], and variations or combinations of those [[surgery|surgeries]], that facilitate the escape of excess [[aqueous humor]] from the eye to lower [[intraocular pressure]], and a few that lower [[IOP]] by decreasing the production of [[aqueous humor|aqueous]].
==Surgery==
==Surgery==
===Procedures that Facilitate Outflow of Aqueous Humor===
*Surgery therapy of glaucoma is undertaken when:
====Laser Trabeculoplasty====
:#medical therapy is not appropriate, not tolerated, not effective, or not properly utilized by a particular patient
A ''trabeculoplasty'' is a modification of the [[trabecular meshwork]]. ''[[Laser]] trabeculoplasty'' (LTP) is the application of a [[laser]] beam to burn areas of the trabecular meshwork, located near the base of the [[iris]], to increase fluid outflow. LTP is used in the treatment of various open-angle glaucomas. The two types of [[laser]] trabeculoplasty are ''[[argon]] [[laser]] trabeculoplasty'' (ALT) and ''selective [[laser]] trabeculoplasty'' (SLT). As its name suggests, [[argon]] [[laser]] trabeculoplasty uses an [[argon]] [[laser]] to create tiny burns on the trabecular meshwork. Selective [[laser]] trabeculoplasty is newer technology that uses a [[Nd:YAG laser]] to target specific cells within the trabecular meshwork and create less thermal damage than ALT. SLT shows promise as a long term treatment. In SLT a [[laser]] is used to selectively target the [[melanocyte]]s in the trabecular meshwork. Though the mechanism by which SLT functions is not well understood, it has been shown in trials to be as effective as the older [[Argon]] [[Laser]] Trabeculoplasty. However, because SLT is performed using a much lower power [[laser]], it does not appear to affect the structure of the trabecular meshwork (based on [[electron microscopy]]) to the same extent, so retreatment may be possible if the effects from the original treatment should begin wear off, although this has not been proven in clinical studies. ALT is repeatable to some extent with measurable results possible.
:#the glaucoma remains uncontrolled with either documented progressivedamage or a very high risk of further damage.
*Surgery is usually the primary approach for infantile and pupillary-blockglaucoma.
*When surgery is indicated, the clinical setting must guide the selection of the appropriate procedure.
:#[[trabeculectomy]] and its variations
:#non-penetrating filtration procedures
:#glaucoma drainage tube implants
:#angle surgery for congenital glaucoma
:#ciliary body ablation.
:#iridectomy
:#gonioplasty
===Surgery For Open Angle Glaucoma===
*Surgery is indicated when [[Intraocular pressure|IOP]] cannot be maintained by nonsurgical therapies at a level considered low enough to prevent further pressure-related damage to theoptic nerve or visual field loss. Surgery has traditionally been considered only
when medical therapy has failed and is associated with long-term risks of blebassociated problems, cataracts, and infection.
*The glaucoma may be uncontrolled for various reasons:
:#Maximal medical therapy fails to adequately reduce IOP
:#The amount of medical therapy necessary to control IOP is not well tolerance or places the patient at unacceptable risk
:#Optic nerve cupping or visual field loss is progressing despite apparent “adequate” reduction of IOP with medical therapy.
:#The patient cannot comply with the necessary medical regimen
====Laser Trabeculoplasty (LTP)<ref name="GeffenAssia2017">{{cite journal|last1=Geffen|first1=Noa|last2=Assia|first2=Ehud I.|last3=Melamed|first3=Shlomo|title=Laser-Assisted Techniques for Penetrating and Nonpenetrating Glaucoma Surgery|volume=59|year=2017|pages=100–112|issn=0250-3751|doi=10.1159/000458490}}</ref>====  
*'''Mechanism of action'''
:*LTP stimulates the growth of trabecular meshwork endothelial cells → restorestrabecular meshwork function → improves the outflow facility
*'''Indications'''
:#Patients with glaucoma on maximum tolerated medical therapy who require lower IOP and in whom the angle is open on gonioscopy.
:#LTP effectively reduces IOP in patients with [[Open-angle glaucoma|POAG]], pigmentary glaucoma, and exfoliation syndrome. Aphakic and pseudophakic eyes may respond less favorably than phakic eyes; therefore, LTP may be more effective before than after cataract surgery.
:#The role of initial LTP in POAG is at least as effective as medications for the first 2 years. LTP may postpone the need for conventional surgery or additional medications. When effective, LTP is expected to lower IOP 20%-25%.
*'''Relative contraindications'''
:#Inflammatory glaucoma
:#Membrane in the angle
:#Young patients who have developmental defects.
:#The lack of effect in the fellow eye
*'''Preoperative evaluation'''
:#Optic nerve evaluation
:#Visual field examination
:#Gonioscopy to check that the angle must be open. The amount of pigment in the angle will help determine the laser settings for argon laser; a more pigmented angleresponds to lower laser energy
*'''Argon laser procedure'''
:#Set at 300-1000 mW, 50 um, and 0.1 second.Laser beam is focused through a gonio lens at the junction of the anterior unpigmented and the posterior pigmented edge of the trabecular meshwork.
:#Laser energy was applied to the entire circumference (360°) of the trabecular meshwork. End point: blanching of the trabecular meshwork or production of a tiny bubble. If a large bubble appears, the power is reduced.
:#Application to the posterior trabecular meshwork tends to produce inflammation, pigment dispersion, prolonged elevation of IOP, and PAS.
:#Diode laser procedure: is similar; set at 600-1000 mW, 75 um, and 0.02second.
*'''Complications'''
:#Transient rise in IOP (occurs in 20% of patients), usually evident within thefirst 2-4 hours after treatment. Topical medications shown to blunt the IOPspikes include alpha2-agonists, beta blockers, pilocarpine, and topical CAIs. Hyperosmotic agents, oral CAIs, and ice packs may be helpful in eyes with IOP spikes not responsible to topical medication.
:#Low-grade iritis
:#Persistent elevation of IOP requiring filtering surgery
:#Hyphema
:#Formation of PAS
:#Re-treatment of an angle that has been fully treated has a lower success rate and a higher complication rate than does primary treatment. If initial LTP fails tobring IOP under control, a trabeculectomy should be considered.


====Iridotomy====
====Selective Laser Trabeculoplasty<ref name="Schlote2017">{{cite journal|last1=Schlote|first1=Torsten|title=Stellenwert der selektiven Lasertrabekuloplastik (SLT)|journal=Klinische Monatsblätter für Augenheilkunde|year=2017|issn=0023-2165|doi=10.1055/s-0043-102946}}</ref>====
An ''[[iridotomy]]'' involves making puncture-like openings through the [[iris (anatomy)|iris]] without the removal of [[iris]] tissue. Performed either with standard [[surgery|surgical]] instruments or a [[laser]], it is typically used to decrease [[IOP|intraocular pressure]] in patients with angle-closure glaucoma. A ''[[laser]] peripheral [[iridotomy]]'' (LPI) is the application of a [[laser]] beam to selectively burn a hole through the [[iris]] near its base. LPI may be performed with either an [[argon]] [[laser]] or [[Nd:YAG laser]].
:*Q-switched 532 nm Nd:YAG laser trabeculoplasty,the laser targets intracellular melanin.


====Iridectomy====
====Incisional Surgery for Open Angle Glaucoma====
:#The goal of filtering surgery (fistulizing procedure) is to create a new pathway(fistula) for the bulk flow of aqueous humor from the anterior chamber throughthe surgical defect in the sclera into the subconjunctival and sub-Tenon’s space.
:#The filtering procedure most commonly used is guarded trabeculectomy.
*'''Indications''': a patient with glaucoma on maximum tolerable medical therapy (MTMT) who has had maximal laser benefit and whose optic nerve function is failing or is likely to fail.The physician can determine that the patient is at MTMT only by advancing therapy beyond the tolerated level and documenting intolerance. An alternative concept is core therapy, in which treatment consists of those medications likelyto work well in combination.
*'''Relative contraindications'''
:#Blind eye → ciliary body ablation is a better alternative for lowering IOP
:#Active anterior segment neovascularization (rubeosis iridis) or active iritis → the underlying problem should be addressed first, or a surgical alternativesuch as tube implant surgery should be considered.
:#Sustained extensive conjunctival injury or extremely thin sclera fromextensive prior surgery or necrotizing scleritis.
:#Younger or aphakic/pseudophakic patients.
:#Black patients.
:#Patients with uveitic glaucoma or with previously failed filtration procedures
*'''Preoperative evaluation'''
:#The patient must be medically stable for an invasive ocular procedure under local anesthesia.
:#Control of preoperative inflammation with corticosteroids helps to reducepostoperative iritis and scarring of the filtering bleb.
:#Anticholinesterase agents should be discontinued if possible and replacedtemporarily by alternative medications at least 2-3 weeks before surgery toreduce bleeding and iridocyclitis.
:#IOP should be reduced as close as possible to normal levels before surgery isperformed, to minimize the risk of expulsive choroidal hemorrhage.
:#Antiplatelet medications should be discontinued.
:#Systemic hypertension should be controlled.
:#Patient should be informed :
:::*The purpose and expectations of surgery: to arrest or delay progressive visual loss caused by their glaucoma.
:::*Glaucoma surgery alone rarely improves vision.
:::*Glaucoma medications may still be required postoperatively
:::*Surgery may fail completely
:::*Vision could be lost as a result of surgery
:::*Glaucoma may progress despite successful surgery
:::*Patients with far advanced visual field loss or field loss that is impinging on fixation are at risk for total loss of central acuity following a surgical procedure. The possible mechanism of this phenomenon include:
::::*Cystoid macular edema
::::*Early postoperative IOP spiking
::::*Shifting of the lamina, further compromising remaining axons
::::*Optic nerve ischemia, possibly related to regional anesthesia
====Trabeculectomy====
:*A guarded partial-thickness filtering procedure performed by removing ablock of limbal tissue beneath a scleral flap. The scleral flap providesresistance and limits the outflow of aqueous, thereby reducing the complications associated with early hypotony (such as flat anterior chamber, cataract, serous and hemorrhagic choroidal effusion, macular edema, and optic nerve edema)
:*The use of antifibrotic agents (such as mitomycin-C and 5-fluorouracil),combined with techniques of releasable sutures or laser suture lysis, enhancesthe longevity of guarded procedures.
:*Succesful trabeculectomy surgery:
:#Involves reducing IOP and avoiding or managing complications
:#Depends on appropriate and timely postoperative intervention to influencethe functioning of the filter.
:#Complete healing of the epithelial and conjunctival wound with incompletehealing of the scleral wound is the goal of this procedure.
:*'''Trabeculectomy procedure''' :
::* Preoperative evaluation
::* Exposure.
:::* A corneal traction suture or superior rectus bridle suture can rotate the globe down, giving excellent exposure of the superior sulcus and limbus.
::* Conjunctival wound.
:::*Fornix-based conjunctival flap → provides better exposure at the limbus; more difficult to achieve a water-tight closure.
:::*Limbal-based conjunctival flap → technically more challenging but allows for a secure closure well away from the limbus.
::* Scleral flap (3-4 mm trapezoidal or rectangular flap).
:::*The flap is dissected anteriorly into clear cornea.
::*Paracentesis
:::*To control the anterior chamber through instillation of BSS or viscoelastic
:::*Allows for gradual lowering of IOP
:::*Intraoperative testing of the patency of the filtration site as well as of the integrity of the conjunctival closure.
::*Sclerotomy (with a punch or with sharp dissection).
:::* The size of the ostomy is determined by the scleral flap and the amount of overlap desired by the surgeon.
:::*A small amount of tissue should remain at the edges of the ostomy to allow for resistance to outflow from the flap.
::* Iridectomy
:::*To lessen the risk of iris occluding the ostomy
:::*To reduce the risk of pupillary block
::*Closure of scleral flap
:::*With the advent of laser suture lysis and releasable sutures, many surgeons close the flap relatively tightly to avoid early shallow chambers. After a few days, flap sutures are released to promote filtration.
:::*Flow should be tested around the flap before closing the conjunctiva.
:::*Leakage around the flap may be adjusted intraoperatively by the placement of additional sutures, removal of sutures, or application of cautery to shrink the wound edges.
::* Closure of conjunctiva
:::*Fornix-based flap → conjunctiva is secured at the limbus
:::*Limbal-based  flap  →  conjunctiva  and  Tenon’s  capsule  are  closed separately or in a single layer.
::* Postoperative management
:::*Topical antibiotics and corticosteroids
:::* Topical cycloplegic agents or mydriatics
:::*Sub-Tenon’s corticosteroids or a short course of systemic corticosteroids
::* Antifibrotic agents
:::* 5-fluorouracil (5-FU), a pyrimidine analogue
::::*5-FU  →  deoxynucleotide  5-fluoro-2’-deoxyuridine  5’-monophosphate (FdUMP) → interferes with DNA synthesis through its action on thymidylate synthetase
::::* Inhibits fibroblast proliferation; reduces scarring after filtering surgery.
::::*50 mg/ml on a surgical sponge is used intraoperatively.
::::*A total of 5 mg in 0.1-0.5 cc can be injected postoperatively.
:::* Mitomycin-C (MMC), derived from Streptomyces caespitosus
::::* Acts as an alkylating agent after enzyme activation resulting in DNA crosslinking.
::::*  Most commonly administered intraoperatively by placing a surgical sponge soaked in MMC within the subconjunctival space in contact with sclera at the planned trabeculectomy site.
::::* Concentrations are typically between 0.2 and 0.4 mg/ml with a duration of application from 1 to 4 minutes
:::* They should be used with caution in primary trabeculectomies on young myopic patients because of an increased risk of hypotony.
:::* Techniques allowing tighter initial wound closure of the scleral flap help toprevent early postoperative hypotony.
::::* The use of releasable flap sutures
::::*The placement of additional sutures that can be cut postoperatively.
::::* Laser suture lysis
:*'''Early complications''':
::#Infection
::#Hypotony
::#Flat anterior chamber
::#Aqueous misdirection
::#Hyphema
::#Formation or acceleration of cataract
::#Transient IOP elevation
::#Cystoid Macular Edema
::#Hypotony maculopathy
::#Choroidal effusion
::#Suprachoroidal hemorrhage
::#Persistent uveitis
::#Dellen formation
::#Loss of vision
:*'''Late complications''':
::#Leakage or failure of the filtering bleb
::#Cataract
::#Blebitis,
::#Endophthalmitis (bleb infection)
::#Symptomatic bleb (dysesthetic bleb)
::#Bleb migration
::#Hypotony
*'''Full Thickness Sclerotomy'''
:#A block of limbal tissue is removed with a punch, trephine, laser or cautery.
:#Advantages: IOP can be lowered and maintained at a lower level for long periods of time.
:#Disadvantages: higher incidence of postoperative flat anterior chamber, cataract, hypotony, choroidal effusion, leakage of filtering blebs, and endophthalmitis.
*'''Combined Cataract & Filtering Surgery'''
:*Indications
::#Glaucoma that is uncontrollable either medically or after laser trabeculoplasty when visual function is significantly impaired by a cataract
::#Cataract requiring extraction in a glaucoma patient who has advanced visual field loss
::#Cataract requiring extraction in a glaucoma patient requiring medications to control IOP in whom medical therapy is poorly tolerated
::#Cataract requiring extraction in a glaucoma patient who requires multiple medications to control IOP
:*Contraindications
::#Glaucoma that requires a very low target IOP
::#Advanced glaucoma with uncontrolled IOP and immediate need for successful reduction of IOP, thus Glaucoma surgery alone is preferred.
===Surgery for Angle Closure Glaucoma===
*The first clinical decision point following the diagnosis of ACG is to distinguish between angle closure based on a pupillary block mechanism and angle closure based on another mechanism.
*The treatment of pupillary-block glaucoma, whether primary or secondary, is a laser or an incisional iridectomy
*For eyes with secondary angle closure not caused by pupillary block, an attempt should be made to identify and treat underlying conditions.
====Laser Iridectomy====
*Indications
:#The presence of pupillary block
:#The need to determine the presence of pupillary block
:#To prevent pupillary block in an eye considered at risk, as determined by gonioscopic evaluation or because of an angle-closure attack in the fellow eye:#This procedure provides an alternative route for aqueous trapped in the posterior chamber to enter the anterior chamber, allowing the iris to recede from its occlusion of the trabecular meshwork.
:*Contraindications: active rubeosis iridis, systemic anticoagulants consumption, angle closure not caused by a pupillary block mechanism
:*Preoperative consideration
::#The glaucoma attack should be attempted medically, then proceed to surgery.
::#Care should be taken to keep the iridectomy peripheral and covered by eyelid, if possible, to avoid monocular diplopia.
::#Pilocarpine may be helpful by stretching and thinning the iris
::#Apraclonidine or other agents can help blunt IOP spikes
:*Technique
::#Set the argon laser at 800-1000 mW, 50 um, 0.02-0.1 second, using a condensing contact lens. There are a number of variations in technique, and iris color dictates which technique is chosen. Complications include localized lens opacity, acute rise in IOP, transient or persistent iritis, early closure of the iridectomy, and corneal and retinal burns
::#Q-switched Nd:YAG laser generally requires fewer pulses and less energy. The effectiveness of this laser is not affected by iris color. With a condensing contact lens, the typical initial laser setting is 2-8 mJ. Complications include corneal burns, disruption of the anterior lens capsule or corneal endothelium, bleeding, postoperative IOP spike, inflammation, and delayed closure of the iridectomy.
:*Postoperative care
::#Bleeding → particularly with Nd:YAG laser; compression of the eye with the laser lens will tamponade the vessel, or argon laser can be used to coagulate the vessel.
::#IOP spikes → can be treated as described in the section on LTP
::#Inflammation → topical corticosteroids
:*Complications
::#Focal lens damage. It can be avoided by ceasing the procedure as soon as the iris is penetrated
::#Retinal detachment is very rare, associated with Nd:YAG laser.
::#Bleeding and IOP spike
====Laser Gonioplasty or Peripheral Iridioplasty====
:*Indications
::#ACG resulting from plateau iris syndrome and nanophthalmos.
::#To open the angle temporarily, in anticipation of a more definitive laser or incisional iridectomy.
:*Contraindications: active rubeosis iridis, systemic anticoagulants consumption, angle closure not caused by a pupillary block mechanism
:*Technique
::#Set the argon laser at 200-500 mW, 200-500 um, 0.1-0.5 second
::#Stromal burns are created in the peripheral iris to cause contraction and flattening.
====Incisional Surgery for Angle Closure====
:*Peripheral iridectomy may be required if a patent iridectomy cannot beachieved with a laser (cloudy cornea, flat anterior chamber, insufficient patient
cooperation)
:*Cataract extraction might be considered when pupillary block is associated with a visually significant cataract.
:*Chamber deepening and goniosynechialysis may break PAS.
====Glaucoma Tube Shunt====
:*Types of glaucoma drainage devices
::#Resistance (valved) or flow-restricted devices: Krupin, Ahmed
::#Nonresistance (nonvalved) devices: Molteno, Baelveldt
::#Anterior chamber tube shunt to an encircling band (ACTSEB) – Schocket procedure
:*Indications
::#Trabeculectomy failure
::#Failed trabeculectomy with antifibrotics
::# Active uveitis
::#Neovascular glaucoma
::#Inadequate conjunctiva
::#Impending need for penetrating keratoplasty
::#Others: poor candidate for trabeculectomy, potential for visual acuity, need for lower IOP
:*Contraindications
::#Eyes with very poor visual potential
::#Patients unable to comply with self-care in the postoperative period.
::# Borderline corneal endothelial function
:*Preoperative considerations
::#The status of the conjunctiva
::#The health of the sclera at the anticipated tube and external reservoir sites
::#The location of vitreous in the eye
:*Technique for implantation:
::#The superotemporal quadrant is preferred.
::# The extraocular plate or valve mechanism is sutured between the vertical and horizontal rectus muscles posterior to the muscle insertions.
::#The tube is routed anteriorly to enter in the chamber angle or through the pars plana for posterior implantation in eyes that have had a vitrectomy.
::#The tube is covered with tissue such as sclera, pericardium, or dura to help prevent erosion.
:*Postoperative management: topical steroids, antibiotics, and cycloplegics; IOP monitoring
:*Complications: tube-corneal touch, flat chamber and hypotony, tube occlusion, tube migration, valve malfunction, tube or plate exposure or erosion
====Ciliary Body Ablation Procedures=====
:*Procedures: cyclocryotherapy, diathermy, therapeutic ultrasound, thermal lasers (continuous Nd:YAG, argon, diode)
:*Goal: To reduce aqueous secretion by destroying a portion of the cilary body.
:* Indications
::# Eyes that have poor visual potential or are poor candidates for incisional surgery → generally reserved for eyes that have been or are likely to be unresponsive to other modes of therapy.
:*Contraindications: eyes with good vision
:*Preoperative evaluation: same as for incisional glaucoma surgery
:* Postoperative management: analgesics, narcotics
:*Complications: prolonged hypotony, pain, inflammation, cystoid macular edema, hemorrhage, phthisis bulbi
====Cyclodialysis====
:*Indications: aphakic patients who have not responses to filtering surgery.
:*Techniques
:#A small scleral incision is made approximately 4 mm from the limbus.
:# A fine spatula is passed under the sclera into the anterior chamber.
:# This spatula disinserts a portion of the ciliary muscle from the scleral spur and creates a cleft in the angle, providing direct communication between the anterior chamber and the suprachoroidal space.
:*Complications: bleeding, inflammation, cataract, stripping of Descemet’s membrane, profound hypotony.
====Non Penetrating Procedures====
:#Deep sclerectomy with collagen implant
:# Deep sclerectomy with injection of viscoelastic into Schlemm’s canal (viscocanalostomy)
:# Involve creation of a superficial scleral flap and a deeper scleral dissection underneath to leave behind only a thin layer of sclera and Descemet’s membrane.


An ''[[iridectomy]]'', also known as a ''corectomy'' or ''[[surgical]] [[iridectomy]]'', involves the removal of a portion of [[iris]] tissue.<ref name="Cline">Cline D; Hofstetter HW; Griffin JR. ''Dictionary of Visual Science''. 4th ed. Butterworth-Heinemann, Boston 1997. ISBN 0-7506-9895-0</ref> A basal [[iridectomy]] is the removal of [[iris]] tissue from the far periphery, near the [[iris]] root; a peripheral [[iridectomy]] is the removal of [[iris]] tissue at the periphery; and a sector [[iridectomy]] is the removal of a wedge-shaped section of [[iris]] that extends from the [[pupil]] margin to the [[iris]] root, leaving a keyhole-shaped [[pupil]].
==Surgeries for Congenital Glaucoma==


===Filtering Procedures: Penetrating vs. Non-penetrating===
====Goniotomy & Trabeculectomy====
Filtering [[surgery|surgeries]] are the mainstay of [[surgery|surgical]] treatment to control [[IOP|intraocular pressure]].<ref>Jacobi PC, Dietlein TS, Krieglstein GK. "Technique of goniocurettage: a potential treatment for advanced chronic open angle glaucoma." ''Br J Ophthalmol''. 1997 Apr;81(4):302-7. PMID 9215060.</ref> An ''[[anterior]] sclerotomy'' or ''sclerostomy'' is used to gain access to the inner layers of the eye<ref name="pmid10150851">{{cite journal| author=Berlin MS, Yoo PH, Ahn RJ| title=The role of laser sclerostomy in glaucoma surgery. | journal=Curr Opin Ophthalmol | year= 1995 | volume= 6 | issue= 2 | pages= 102-14 | pmid=10150851 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10150851  }} </ref><ref name="pmid9215060">{{cite journal| author=Jacobi PC, Dietlein TS, Krieglstein GK| title=Technique of goniocurettage: a potential treatment for advanced chronic open angle glaucoma. | journal=Br J Ophthalmol | year= 1997 | volume= 81 | issue= 4 | pages= 302-7 | pmid=9215060 | doi= | pmc=PMC1722166 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9215060  }} </ref> in order to create a drainage channel from the [[anterior chamber]] to the external surface of the eye under the [[conjunctiva]], allowing [[aqueous humor|aqueous]] to seep into a bleb from which it is slowly absorbed. Filtering procedures are typically divided into either penetrating or non-penetrating types depending upon whether an intraoperative entry into the [[anterior chamber]] occurs.
:*Indications: childhood glaucoma
 
:*Contraindications: infants with unstable health, multiple anomalies with poor prognosis and a grossly disorganized eye.
Penetrating filtering [[surgery|surgeries]] are further subdivided into guarded filtering [[procedure]]s, also known as protected, subscleral, or partial thickness filtering procedures (in which the [[surgeon]] [[suture]]s a [[sclera]]l flap over the sclerostomy site, and full thickness procedures. ''[[Trabeculectomy]]'' is a guarded filtering [[procedure]] that removes of part of the trabecular meshwork. Full thickness [[procedure]]s include sclerectomy, posterior lip sclerectomy (in which the surgeon completely [[excision|excises]] the [[sclera]] on the area of the sclerostomy, trephination, thermal sclerostomy (Scheie procedure), iridenclesis, and sclerostomy (including conventional sclerostomy and [[enzymatic]] sclerostomy).
:*Technique
 
:#The anterior chamber should be filled with viscoelastic to prevent collapse and to tamponade bleeding.
Non-penetrating filtering [[surgery|surgeries]] do not penetrate or enter the eye's [[anterior chamber]]<ref name="pmid12048520">{{cite journal| author=Hamard P, Lachkar Y| title=[Non penetrating filtering surgery, evolution and results]. | journal=J Fr Ophtalmol | year= 2002 | volume= 25 | issue= 5 | pages= 527-36 | pmid=12048520 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12048520  }} </ref><ref name="pmid11880725">{{cite journal| author=Lachkar Y, Hamard P| title=Nonpenetrating filtering surgery. | journal=Curr Opin Ophthalmol | year= 2002 | volume= 13 | issue= 2 | pages= 110-5 | pmid=11880725 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11880725  }} </ref>. There are two types of non-penetrating [[surgery|surgeries]]: Bleb-forming and viscocanalostomy. Bleb forming [[procedure]]s include ab externo [[trabeculectomy]] and deep sclerectomy. Ab externo [[trabeculectomy]] (AET) involves cutting from outside the eye inward to reach [[Schlemm's canal]], the trabecular meshwork, and the [[anterior chamber]]. Also known as non-penetrating [[trabeculectomy]] (NPT), it is an ab externo (from the outside), major [[ocular]] [[procedure]] in which [[Schlemm's canal]] is [[surgery|surgically]] exposed by making a large and very deep [[sclera]]l flap. The inner wall of [[Schlemm's canal]] is stripped off after [[surgery|surgically]] exposing the canal. Deep sclerectomy, also known as nonpenetrating deep sclerectomy (PDS) or nonpenetrating [[trabeculectomy]] is a filtering [[surgery]] where the internal wall of [[Schlemm's canal]] is [[excision|excised]], allowing sub[[conjunctiva]]l filtration without actually entering the [[anterior chamber]]<ref name="pmid15005582">{{cite journal| author=Lachkar Y, Neverauskiene J, Jeanteur-Lunel MN, Gracies H, Berkani M, Ecoffet M et al.| title=Nonpenetrating deep sclerectomy: a 6-year retrospective study. | journal=Eur J Ophthalmol | year= 2004 | volume= 14 | issue= 1 | pages= 26-36 | pmid=15005582 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15005582  }} </ref>; it is commonly performed with the Aquaflow® collagen wick. ''Viscocanalostomy'' is also an ab externo, major [[ocular]] [[procedure]] in which [[Schlemm's canal]] is [[surgery|surgically]] exposed by making a large and very deep [[sclera]]l flap. In the VC procedure, [[Schlemm's canal]] is [[cannulation|cannulated]] and [[viscoelastic]] substance [[injection|injected]] (which [[mydriasis|dilates]] [[Schlemm's canal]] and the aqueous collector channels).
:#Goniotomy A needle-knife is passed across the anterior chamber, and a superficial incision is made in the anterior aspect of the trabecular meshwork under gonioscopic control.
 
:#Trabeculotomy → A fine wirelike instrument (trabeculotome) is inserted into Schlemm’s canal from an external incision, and the trabecular meshwork is torn by rotating the trabeculotome into the anterior chamber.
===Other Surgical Procedures===
:#Goniotomy is possible only in an eye with a relatively clear cornea, whereas trabeculotomy can be performed whether the cornea is clear or cloudy.
''Goniotomy'' and ''trabeculotomy'' are similar simple and directed techniques of microsurgical dissection with mechanical disruption of the trabecular meshwork. Gonotomy [[procedure]]s include [[surgery|surgical]] goniotomy and [[laser]] goniotomy. A [[surgery|surgical]] goniotomy involves cutting the fibers of the trabecular meshwork to allow [[aqueous humor|aqueous fluid]] to flow more freely from the eye. [[Laser]] goniotomy is also known as goniophotoablation and [[laser]] trabecular ablation. In many patients suffering from [[congenital]] glaucoma, the [[cornea]] is not clear enough to visualize the [[anterior chamber]] angle. Although an [[endoscopic]] goniotomy, which employs an [[endoscope]] to view the [[anterior chamber]] angle, may be performed, a trabeculotomy which accesses the angle from the exterior surface of the eye, thereby eliminating the need for a clear [[cornea]], is usually preferred in these instances. A specially designed probe is used to tear through the trabecular meshwork to open it and allow fluid flow.
 
''Tube-shunt [[surgery]]'' or ''drainage implant [[surgery]]'' involves the placement of a tube or [[glaucoma valve]]s to facilitate [[aqueous humor|aqueous]] outflow from the [[anterior chamber]]. Trabeculopuncture uses a Q switched [[Nd:YAG laser]] to punch small holes in the trabecular meshwork with<ref name="pmid4022580">{{cite journal| author=Epstein DL, Melamed S, Puliafto CA, Steinert RF| title=Neodymium: YAG laser trabeculopuncture in open-angle glaucoma. | journal=Ophthalmology | year= 1985 | volume= 92 | issue= 7 | pages= 931-7 | pmid=4022580 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4022580  }} </ref><ref name="pmid121373">{{cite journal| author=van der Zypen E, Fankhauser F| title=The ultrastructural features of laser trabeculopuncture and cyclodialysis. Problems related to successful treatment of chronic simple glaucoma. | journal=Ophthalmologica | year= 1979 | volume= 179 | issue= 4 | pages= 189-200 | pmid=121373 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=121373  }} </ref>. ''Goniocurretage'' is an "ab interno" (from the inside) [[procedure]] that used an instrument "to scrape [[pathological]]ly altered trabecular meshwork off the [[sclera]]l [[sulcus]]"<ref name="pmid9215060">{{cite journal| author=Jacobi PC, Dietlein TS, Krieglstein GK| title=Technique of goniocurettage: a potential treatment for advanced chronic open angle glaucoma. | journal=Br J Ophthalmol | year= 1997 | volume= 81 | issue= 4 | pages= 302-7 | pmid=9215060 | doi= | pmc=PMC1722166 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9215060  }} </ref>. A [[Surgery|surgical]] ''cyclodialysis'' is a rarely used procedure that aims to separate the [[ciliary body]] from the [[sclera]] to form a communication between the suprachoroidal space and the [[anterior chamber]].<ref name="Cline"/> A ''cyclogoniotomy'' is a [[surgery|surgical]] [[procedure]] for producing a cyclodialysis, in which the [[ciliary body]] is cut from its attachment at the [[sclera]]l spur under [[gonioscopy|gonioscopic]] control.<ref name="Cline"/>
 
A ''[[ciliarotomy]]'' is a [[surgery|surgical]] division of the [[ciliary body|ciliary zone]] in the treatment of glaucoma<ref name="Cline"/>.
==== Canaloplasty ====
Canaloplasty is a nonpenetrating procedure utilizing microcatheter technology. To perform a canaloplasty, an [[incision]] in made into the eye to gain access to [[Schlemm's canal]] in a similar fashion to a viscocanalostomy. A microcatheter will circumnavigate the canal around the [[iris]], enlarging the main drainage channel and its smaller collector channels through the injection of a sterile, gel-like material called [[viscoelastic]]. The catheter is then removed and a [[suture]] is placed within the canal and tightened. By opening the canal, the [[IOP|pressure inside the eye]] may be relieved, although the reason is unclear since the [[Schlemm's canal|canal (of Schlemm)]] does not have any significant fluid resistance in glaucoma or healthy eyes. Long-term results are not available.
 
===Procedures that decrease production of aqueous humor===
Certain cells within the eye's [[ciliary body]] produce aqueous humor. A ciliary destructive or cyclodestructive procedure is one that aims to destroy those cells in order to reduce intraocular pressure [http://www.med.umich.edu/1libr/aha/aha_gfollow_oph.htm]. '''[[Cyclocryotherapy]]''', or cyclocryopexy, uses a freezing probe [http://www.wills-glaucoma.org/cyclotherapy.htm]. Cyclophotocoagulation, also known as transscleral cyclophotocoagulation, ciliary body ablation,[http://www.emedicinehealth.com/articles/38365-6.asp], cyclophotoablation [http://www.techniques-in-ophthalmology.com/pt/re/techophth/abstract.00145756-200312000-00007.htm;jsessionid=DmVgzeMPoLTnzNMAeXm4awgZWBAbDuLph511nCc1h8wF1uy4vC1l!-85436088!-949856145!9001!-1], and cyclophototherapy [http://www.emedicine.com/oph/topic317.htm], uses a laser<ref>[http://www.eyemdlink.com/EyeProcedure.asp?EyeProcedureID=48 EyeMDLink.com - Cyclophotocoagulation]</ref>{{ref|Trabeculectomy}}. '''[[Cyclodiathermy]]''' uses heat generated from a high frequency [[alternating current|alternating electric current]] passed through the tissue,<ref name="Cline"/> while '''[[cycloelectrolysis]]''' uses the chemical action caused by a low frequency [[direct current]].<ref name="Cline"/>
==Glaucoma drainage implants==
There are also several different glaucoma drainage implants. These include the original Molteno implant (1966), the Baerveldt tube shunt, or the valved implants, such as the Ahmed glaucoma valve implant and the later generation pressure ridge Molteno implants. These are indicated for glaucoma patients not responding to maximal medical therapy, with previous failed guarded filtering surgery (trabeculectomy). The flow tube is inserted into the anterior chamber of the eye and the plate is implanted underneath the conjunctiva to allow flow of aqueous fluid out of the eye into a chamber called a bleb.  The Express mini-implant is currently being used as a modification of the standard trabeculectomy technique, and is a non-valved conduit between the anterior chamber and the space under the scleral flap<ref name="express">Maris PJ, Jr., Ishida K, Netland PA. Comparison of trabeculectomy with Ex-PRESS miniature glaucoma device implanted under scleral flap. J Glaucoma 2007 January;16(1):14-9 </ref>.
 
* The first-generation Molteno and other non-valved implants sometimes require the ligation of the tube until the bleb formed is mildly fibrosed and water-tight<ref name="VicrylTie">
Molteno AC, Polkinghorne PJ, Bowbyes JA. The vicryl tie technique for inserting a draining implant in the treatment of secondary glaucoma. Aust N Z J Ophthalmol. 1986 Nov;14(4):343-54
[http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=3814422&dopt=Citation.]
</ref>This is done to reduce postoperative hypotony -- sudden drops in postoperative intraocular pressure (IOP).
* Valved implants such as the Ahmed glaucoma valve attempt to control postoperative hypotony by using a mechanical valve. Studies show that in severe cases of glaucoma, double plate Molteno implants are associated with lower mean IOP in the long term compared to the Ahmed glaucoma valve <ref name="AhmedCompare">
Ayyala RS, Zurakowski D et al. Comparison of double-plate Molteno and Ahmed glaucoma valve in patients with advanced uncontrolled glaucoma.
Ophthalmic Surg Lasers. 2002 Mar-Apr;33(2):94-101.[http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=11942556&dopt=Citation].
</ref>
* Second and third generation Molteno implants incorporate a biological valve and studies show considerable improvement in postoperative outcome over the older style Ahmed and Molteno implants.
 
The ongoing scarring over the conjunctival dissipation segment of the shunt may become too thick for the [[aqueous humor]] to filter through. This may require preventive measures using anti-fibrotic medication like [[5-fluorouracil]] ([[5-FU]]) or [[mitomycin-C]] (during the procedure), or additional surgery.
==See also==
*[[Eye surgery]]


==References==
==References==
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Latest revision as of 21:53, 29 July 2020

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Rohan Bir Singh, M.B.B.S.[2]

Overview

Glaucoma is a group of diseases affecting the optic nerve that results in vision loss and is frequently characterized by raised intraocular pressure (IOP). There are many glaucoma surgeries, and variations or combinations of those surgeries, that facilitate the escape of excess aqueous humor from the eye to lower intraocular pressure, and a few that lower IOP by decreasing the production of aqueous.

Surgery

  • Surgery therapy of glaucoma is undertaken when:
  1. medical therapy is not appropriate, not tolerated, not effective, or not properly utilized by a particular patient
  2. the glaucoma remains uncontrolled with either documented progressivedamage or a very high risk of further damage.
  • Surgery is usually the primary approach for infantile and pupillary-blockglaucoma.
  • When surgery is indicated, the clinical setting must guide the selection of the appropriate procedure.
  1. trabeculectomy and its variations
  2. non-penetrating filtration procedures
  3. glaucoma drainage tube implants
  4. angle surgery for congenital glaucoma
  5. ciliary body ablation.
  6. iridectomy
  7. gonioplasty

Surgery For Open Angle Glaucoma

  • Surgery is indicated when IOP cannot be maintained by nonsurgical therapies at a level considered low enough to prevent further pressure-related damage to theoptic nerve or visual field loss. Surgery has traditionally been considered only

when medical therapy has failed and is associated with long-term risks of blebassociated problems, cataracts, and infection.

  • The glaucoma may be uncontrolled for various reasons:
  1. Maximal medical therapy fails to adequately reduce IOP
  2. The amount of medical therapy necessary to control IOP is not well tolerance or places the patient at unacceptable risk
  3. Optic nerve cupping or visual field loss is progressing despite apparent “adequate” reduction of IOP with medical therapy.
  4. The patient cannot comply with the necessary medical regimen

Laser Trabeculoplasty (LTP)[1]

  • Mechanism of action
  • LTP stimulates the growth of trabecular meshwork endothelial cells → restorestrabecular meshwork function → improves the outflow facility
  • Indications
  1. Patients with glaucoma on maximum tolerated medical therapy who require lower IOP and in whom the angle is open on gonioscopy.
  2. LTP effectively reduces IOP in patients with POAG, pigmentary glaucoma, and exfoliation syndrome. Aphakic and pseudophakic eyes may respond less favorably than phakic eyes; therefore, LTP may be more effective before than after cataract surgery.
  3. The role of initial LTP in POAG is at least as effective as medications for the first 2 years. LTP may postpone the need for conventional surgery or additional medications. When effective, LTP is expected to lower IOP 20%-25%.
  • Relative contraindications
  1. Inflammatory glaucoma
  2. Membrane in the angle
  3. Young patients who have developmental defects.
  4. The lack of effect in the fellow eye
  • Preoperative evaluation
  1. Optic nerve evaluation
  2. Visual field examination
  3. Gonioscopy to check that the angle must be open. The amount of pigment in the angle will help determine the laser settings for argon laser; a more pigmented angleresponds to lower laser energy
  • Argon laser procedure
  1. Set at 300-1000 mW, 50 um, and 0.1 second.Laser beam is focused through a gonio lens at the junction of the anterior unpigmented and the posterior pigmented edge of the trabecular meshwork.
  2. Laser energy was applied to the entire circumference (360°) of the trabecular meshwork. End point: blanching of the trabecular meshwork or production of a tiny bubble. If a large bubble appears, the power is reduced.
  3. Application to the posterior trabecular meshwork tends to produce inflammation, pigment dispersion, prolonged elevation of IOP, and PAS.
  4. Diode laser procedure: is similar; set at 600-1000 mW, 75 um, and 0.02second.
  • Complications
  1. Transient rise in IOP (occurs in 20% of patients), usually evident within thefirst 2-4 hours after treatment. Topical medications shown to blunt the IOPspikes include alpha2-agonists, beta blockers, pilocarpine, and topical CAIs. Hyperosmotic agents, oral CAIs, and ice packs may be helpful in eyes with IOP spikes not responsible to topical medication.
  2. Low-grade iritis
  3. Persistent elevation of IOP requiring filtering surgery
  4. Hyphema
  5. Formation of PAS
  6. Re-treatment of an angle that has been fully treated has a lower success rate and a higher complication rate than does primary treatment. If initial LTP fails tobring IOP under control, a trabeculectomy should be considered.

Selective Laser Trabeculoplasty[2]

  • Q-switched 532 nm Nd:YAG laser trabeculoplasty,the laser targets intracellular melanin.

Incisional Surgery for Open Angle Glaucoma

  1. The goal of filtering surgery (fistulizing procedure) is to create a new pathway(fistula) for the bulk flow of aqueous humor from the anterior chamber throughthe surgical defect in the sclera into the subconjunctival and sub-Tenon’s space.
  2. The filtering procedure most commonly used is guarded trabeculectomy.
  • Indications: a patient with glaucoma on maximum tolerable medical therapy (MTMT) who has had maximal laser benefit and whose optic nerve function is failing or is likely to fail.The physician can determine that the patient is at MTMT only by advancing therapy beyond the tolerated level and documenting intolerance. An alternative concept is core therapy, in which treatment consists of those medications likelyto work well in combination.
  • Relative contraindications
  1. Blind eye → ciliary body ablation is a better alternative for lowering IOP
  2. Active anterior segment neovascularization (rubeosis iridis) or active iritis → the underlying problem should be addressed first, or a surgical alternativesuch as tube implant surgery should be considered.
  3. Sustained extensive conjunctival injury or extremely thin sclera fromextensive prior surgery or necrotizing scleritis.
  4. Younger or aphakic/pseudophakic patients.
  5. Black patients.
  6. Patients with uveitic glaucoma or with previously failed filtration procedures
  • Preoperative evaluation
  1. The patient must be medically stable for an invasive ocular procedure under local anesthesia.
  2. Control of preoperative inflammation with corticosteroids helps to reducepostoperative iritis and scarring of the filtering bleb.
  3. Anticholinesterase agents should be discontinued if possible and replacedtemporarily by alternative medications at least 2-3 weeks before surgery toreduce bleeding and iridocyclitis.
  4. IOP should be reduced as close as possible to normal levels before surgery isperformed, to minimize the risk of expulsive choroidal hemorrhage.
  5. Antiplatelet medications should be discontinued.
  6. Systemic hypertension should be controlled.
  7. Patient should be informed :
  • The purpose and expectations of surgery: to arrest or delay progressive visual loss caused by their glaucoma.
  • Glaucoma surgery alone rarely improves vision.
  • Glaucoma medications may still be required postoperatively
  • Surgery may fail completely
  • Vision could be lost as a result of surgery
  • Glaucoma may progress despite successful surgery
  • Patients with far advanced visual field loss or field loss that is impinging on fixation are at risk for total loss of central acuity following a surgical procedure. The possible mechanism of this phenomenon include:
  • Cystoid macular edema
  • Early postoperative IOP spiking
  • Shifting of the lamina, further compromising remaining axons
  • Optic nerve ischemia, possibly related to regional anesthesia

Trabeculectomy

  • A guarded partial-thickness filtering procedure performed by removing ablock of limbal tissue beneath a scleral flap. The scleral flap providesresistance and limits the outflow of aqueous, thereby reducing the complications associated with early hypotony (such as flat anterior chamber, cataract, serous and hemorrhagic choroidal effusion, macular edema, and optic nerve edema)
  • The use of antifibrotic agents (such as mitomycin-C and 5-fluorouracil),combined with techniques of releasable sutures or laser suture lysis, enhancesthe longevity of guarded procedures.
  • Succesful trabeculectomy surgery:
  1. Involves reducing IOP and avoiding or managing complications
  2. Depends on appropriate and timely postoperative intervention to influencethe functioning of the filter.
  3. Complete healing of the epithelial and conjunctival wound with incompletehealing of the scleral wound is the goal of this procedure.
  • Trabeculectomy procedure :
  • Preoperative evaluation
  • Exposure.
  • A corneal traction suture or superior rectus bridle suture can rotate the globe down, giving excellent exposure of the superior sulcus and limbus.
  • Conjunctival wound.
  • Fornix-based conjunctival flap → provides better exposure at the limbus; more difficult to achieve a water-tight closure.
  • Limbal-based conjunctival flap → technically more challenging but allows for a secure closure well away from the limbus.
  • Scleral flap (3-4 mm trapezoidal or rectangular flap).
  • The flap is dissected anteriorly into clear cornea.
  • Paracentesis
  • To control the anterior chamber through instillation of BSS or viscoelastic
  • Allows for gradual lowering of IOP
  • Intraoperative testing of the patency of the filtration site as well as of the integrity of the conjunctival closure.
  • Sclerotomy (with a punch or with sharp dissection).
  • The size of the ostomy is determined by the scleral flap and the amount of overlap desired by the surgeon.
  • A small amount of tissue should remain at the edges of the ostomy to allow for resistance to outflow from the flap.
  • Iridectomy
  • To lessen the risk of iris occluding the ostomy
  • To reduce the risk of pupillary block
  • Closure of scleral flap
  • With the advent of laser suture lysis and releasable sutures, many surgeons close the flap relatively tightly to avoid early shallow chambers. After a few days, flap sutures are released to promote filtration.
  • Flow should be tested around the flap before closing the conjunctiva.
  • Leakage around the flap may be adjusted intraoperatively by the placement of additional sutures, removal of sutures, or application of cautery to shrink the wound edges.
  • Closure of conjunctiva
  • Fornix-based flap → conjunctiva is secured at the limbus
  • Limbal-based flap → conjunctiva and Tenon’s capsule are closed separately or in a single layer.
  • Postoperative management
  • Topical antibiotics and corticosteroids
  • Topical cycloplegic agents or mydriatics
  • Sub-Tenon’s corticosteroids or a short course of systemic corticosteroids
  • Antifibrotic agents
  • 5-fluorouracil (5-FU), a pyrimidine analogue
  • 5-FU → deoxynucleotide 5-fluoro-2’-deoxyuridine 5’-monophosphate (FdUMP) → interferes with DNA synthesis through its action on thymidylate synthetase
  • Inhibits fibroblast proliferation; reduces scarring after filtering surgery.
  • 50 mg/ml on a surgical sponge is used intraoperatively.
  • A total of 5 mg in 0.1-0.5 cc can be injected postoperatively.
  • Mitomycin-C (MMC), derived from Streptomyces caespitosus
  • Acts as an alkylating agent after enzyme activation resulting in DNA crosslinking.
  • Most commonly administered intraoperatively by placing a surgical sponge soaked in MMC within the subconjunctival space in contact with sclera at the planned trabeculectomy site.
  • Concentrations are typically between 0.2 and 0.4 mg/ml with a duration of application from 1 to 4 minutes
  • They should be used with caution in primary trabeculectomies on young myopic patients because of an increased risk of hypotony.
  • Techniques allowing tighter initial wound closure of the scleral flap help toprevent early postoperative hypotony.
  • The use of releasable flap sutures
  • The placement of additional sutures that can be cut postoperatively.
  • Laser suture lysis
  • Early complications:
  1. Infection
  2. Hypotony
  3. Flat anterior chamber
  4. Aqueous misdirection
  5. Hyphema
  6. Formation or acceleration of cataract
  7. Transient IOP elevation
  8. Cystoid Macular Edema
  9. Hypotony maculopathy
  10. Choroidal effusion
  11. Suprachoroidal hemorrhage
  12. Persistent uveitis
  13. Dellen formation
  14. Loss of vision
  • Late complications:
  1. Leakage or failure of the filtering bleb
  2. Cataract
  3. Blebitis,
  4. Endophthalmitis (bleb infection)
  5. Symptomatic bleb (dysesthetic bleb)
  6. Bleb migration
  7. Hypotony
  • Full Thickness Sclerotomy
  1. A block of limbal tissue is removed with a punch, trephine, laser or cautery.
  2. Advantages: IOP can be lowered and maintained at a lower level for long periods of time.
  3. Disadvantages: higher incidence of postoperative flat anterior chamber, cataract, hypotony, choroidal effusion, leakage of filtering blebs, and endophthalmitis.
  • Combined Cataract & Filtering Surgery
  • Indications
  1. Glaucoma that is uncontrollable either medically or after laser trabeculoplasty when visual function is significantly impaired by a cataract
  2. Cataract requiring extraction in a glaucoma patient who has advanced visual field loss
  3. Cataract requiring extraction in a glaucoma patient requiring medications to control IOP in whom medical therapy is poorly tolerated
  4. Cataract requiring extraction in a glaucoma patient who requires multiple medications to control IOP
  • Contraindications
  1. Glaucoma that requires a very low target IOP
  2. Advanced glaucoma with uncontrolled IOP and immediate need for successful reduction of IOP, thus Glaucoma surgery alone is preferred.

Surgery for Angle Closure Glaucoma

  • The first clinical decision point following the diagnosis of ACG is to distinguish between angle closure based on a pupillary block mechanism and angle closure based on another mechanism.
  • The treatment of pupillary-block glaucoma, whether primary or secondary, is a laser or an incisional iridectomy
  • For eyes with secondary angle closure not caused by pupillary block, an attempt should be made to identify and treat underlying conditions.

Laser Iridectomy

  • Indications
  1. The presence of pupillary block
  2. The need to determine the presence of pupillary block
  3. To prevent pupillary block in an eye considered at risk, as determined by gonioscopic evaluation or because of an angle-closure attack in the fellow eye:#This procedure provides an alternative route for aqueous trapped in the posterior chamber to enter the anterior chamber, allowing the iris to recede from its occlusion of the trabecular meshwork.
  • Contraindications: active rubeosis iridis, systemic anticoagulants consumption, angle closure not caused by a pupillary block mechanism
  • Preoperative consideration
  1. The glaucoma attack should be attempted medically, then proceed to surgery.
  2. Care should be taken to keep the iridectomy peripheral and covered by eyelid, if possible, to avoid monocular diplopia.
  3. Pilocarpine may be helpful by stretching and thinning the iris
  4. Apraclonidine or other agents can help blunt IOP spikes
  • Technique
  1. Set the argon laser at 800-1000 mW, 50 um, 0.02-0.1 second, using a condensing contact lens. There are a number of variations in technique, and iris color dictates which technique is chosen. Complications include localized lens opacity, acute rise in IOP, transient or persistent iritis, early closure of the iridectomy, and corneal and retinal burns
  2. Q-switched Nd:YAG laser generally requires fewer pulses and less energy. The effectiveness of this laser is not affected by iris color. With a condensing contact lens, the typical initial laser setting is 2-8 mJ. Complications include corneal burns, disruption of the anterior lens capsule or corneal endothelium, bleeding, postoperative IOP spike, inflammation, and delayed closure of the iridectomy.
  • Postoperative care
  1. Bleeding → particularly with Nd:YAG laser; compression of the eye with the laser lens will tamponade the vessel, or argon laser can be used to coagulate the vessel.
  2. IOP spikes → can be treated as described in the section on LTP
  3. Inflammation → topical corticosteroids
  • Complications
  1. Focal lens damage. It can be avoided by ceasing the procedure as soon as the iris is penetrated
  2. Retinal detachment is very rare, associated with Nd:YAG laser.
  3. Bleeding and IOP spike

Laser Gonioplasty or Peripheral Iridioplasty

  • Indications
  1. ACG resulting from plateau iris syndrome and nanophthalmos.
  2. To open the angle temporarily, in anticipation of a more definitive laser or incisional iridectomy.
  • Contraindications: active rubeosis iridis, systemic anticoagulants consumption, angle closure not caused by a pupillary block mechanism
  • Technique
  1. Set the argon laser at 200-500 mW, 200-500 um, 0.1-0.5 second
  2. Stromal burns are created in the peripheral iris to cause contraction and flattening.

Incisional Surgery for Angle Closure

  • Peripheral iridectomy may be required if a patent iridectomy cannot beachieved with a laser (cloudy cornea, flat anterior chamber, insufficient patient

cooperation)

  • Cataract extraction might be considered when pupillary block is associated with a visually significant cataract.
  • Chamber deepening and goniosynechialysis may break PAS.

Glaucoma Tube Shunt

  • Types of glaucoma drainage devices
  1. Resistance (valved) or flow-restricted devices: Krupin, Ahmed
  2. Nonresistance (nonvalved) devices: Molteno, Baelveldt
  3. Anterior chamber tube shunt to an encircling band (ACTSEB) – Schocket procedure
  • Indications
  1. Trabeculectomy failure
  2. Failed trabeculectomy with antifibrotics
  3. Active uveitis
  4. Neovascular glaucoma
  5. Inadequate conjunctiva
  6. Impending need for penetrating keratoplasty
  7. Others: poor candidate for trabeculectomy, potential for visual acuity, need for lower IOP
  • Contraindications
  1. Eyes with very poor visual potential
  2. Patients unable to comply with self-care in the postoperative period.
  3. Borderline corneal endothelial function
  • Preoperative considerations
  1. The status of the conjunctiva
  2. The health of the sclera at the anticipated tube and external reservoir sites
  3. The location of vitreous in the eye
  • Technique for implantation:
  1. The superotemporal quadrant is preferred.
  2. The extraocular plate or valve mechanism is sutured between the vertical and horizontal rectus muscles posterior to the muscle insertions.
  3. The tube is routed anteriorly to enter in the chamber angle or through the pars plana for posterior implantation in eyes that have had a vitrectomy.
  4. The tube is covered with tissue such as sclera, pericardium, or dura to help prevent erosion.
  • Postoperative management: topical steroids, antibiotics, and cycloplegics; IOP monitoring
  • Complications: tube-corneal touch, flat chamber and hypotony, tube occlusion, tube migration, valve malfunction, tube or plate exposure or erosion

Ciliary Body Ablation Procedures=

  • Procedures: cyclocryotherapy, diathermy, therapeutic ultrasound, thermal lasers (continuous Nd:YAG, argon, diode)
  • Goal: To reduce aqueous secretion by destroying a portion of the cilary body.
  • Indications
  1. Eyes that have poor visual potential or are poor candidates for incisional surgery → generally reserved for eyes that have been or are likely to be unresponsive to other modes of therapy.
  • Contraindications: eyes with good vision
  • Preoperative evaluation: same as for incisional glaucoma surgery
  • Postoperative management: analgesics, narcotics
  • Complications: prolonged hypotony, pain, inflammation, cystoid macular edema, hemorrhage, phthisis bulbi

Cyclodialysis

  • Indications: aphakic patients who have not responses to filtering surgery.
  • Techniques
  1. A small scleral incision is made approximately 4 mm from the limbus.
  2. A fine spatula is passed under the sclera into the anterior chamber.
  3. This spatula disinserts a portion of the ciliary muscle from the scleral spur and creates a cleft in the angle, providing direct communication between the anterior chamber and the suprachoroidal space.
  • Complications: bleeding, inflammation, cataract, stripping of Descemet’s membrane, profound hypotony.

Non Penetrating Procedures

  1. Deep sclerectomy with collagen implant
  2. Deep sclerectomy with injection of viscoelastic into Schlemm’s canal (viscocanalostomy)
  3. Involve creation of a superficial scleral flap and a deeper scleral dissection underneath to leave behind only a thin layer of sclera and Descemet’s membrane.

Surgeries for Congenital Glaucoma

Goniotomy & Trabeculectomy

  • Indications: childhood glaucoma
  • Contraindications: infants with unstable health, multiple anomalies with poor prognosis and a grossly disorganized eye.
  • Technique
  1. The anterior chamber should be filled with viscoelastic to prevent collapse and to tamponade bleeding.
  2. Goniotomy → A needle-knife is passed across the anterior chamber, and a superficial incision is made in the anterior aspect of the trabecular meshwork under gonioscopic control.
  3. Trabeculotomy → A fine wirelike instrument (trabeculotome) is inserted into Schlemm’s canal from an external incision, and the trabecular meshwork is torn by rotating the trabeculotome into the anterior chamber.
  4. Goniotomy is possible only in an eye with a relatively clear cornea, whereas trabeculotomy can be performed whether the cornea is clear or cloudy.

References

  1. Geffen, Noa; Assia, Ehud I.; Melamed, Shlomo (2017). "Laser-Assisted Techniques for Penetrating and Nonpenetrating Glaucoma Surgery". 59: 100–112. doi:10.1159/000458490. ISSN 0250-3751.
  2. Schlote, Torsten (2017). "Stellenwert der selektiven Lasertrabekuloplastik (SLT)". Klinische Monatsblätter für Augenheilkunde. doi:10.1055/s-0043-102946. ISSN 0023-2165.

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