Myopia classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2] Associate Editor(s)-in-Chief: Saumya Easaw, M.B.B.S.[3]
Classification
Classification Based Upon Etiology
Borish and Duke-Elder classified myopia by cause:
Axial Myopia
Axial myopia is attributed to an increase in the eye's axial length.[1]
Refractive Myopia
Refractory myopia is attributed to the condition of the refractive elements of the eye. Borish further subclassified refractive myopia:
- Curvature myopia is attributed to excessive, or increased, curvature of one or more of the refractive surfaces of the eye, especially the cornea.[1]In those with Cohen syndrome, myopia appears to result from high corneal and lenticular power.[2]
- Index myopia is attributed to variation in the index of refraction of one or more of the ocular media.
Classification Based Upon Clinical Entity
Various forms of myopia have been described by their clinical appearance:[3]
Simple Myopia
It is more common than other types of myopia and is characterized by an eye that is too long for its optical power (which is determined by the cornea and crystalline lens) or optically too powerful for its axial length.[4] Both genetic and environmental factors, particularly significant amounts of near work, are thought to contribute to the development of simple myopia.[4]
Degenerative Myopia
It is also known as malignant, pathological, or progressive myopia, is characterized by marked fundus changes, such as posterior staphyloma, and associated with a high refractive error and subnormal visual acuity after correction.[1] This form of myopia gets progressively worse over time. Degenerative myopia has been reported as one of the main causes of visual impairment.[5] Myopia with degenerative changes has been described as being very common in certain races and cultures, such as Chinese, Japanese, Arab, and Jewish people.[6]
Nocturnal Myopia
It is also known as night myopia or twilight myopia, is a condition in which the eye has a greater difficulty seeing in low illumination areas, even though its daytime vision is normal. Essentially, the eye's far point of an individual's focus varies with the level of light. Night myopia is believed to be caused by pupils dilating to let more light in, which adds aberrations resulting in becoming more nearsighted. A stronger prescription for myopic night drivers is often needed. Younger people are more likely to be affected by night myopia than the elderly.[7]
Pseudomyopia
It is the blurring of distance vision brought about by spasm of the ciliary muscle.[8]
Induced Myopia
It is also known as acquired myopia, results from exposure to various pharmaceuticals, increases in glucose levels, nuclear sclerosis, or other anomalous conditions.[4] The encircling bands used in the repair of retinal detachments may induce myopia by increasing the axial length of the eye.[9]
- Index myopia is attributed to variation in the index of refraction of one or more of the ocular media.[1] Cataracts may lead to index myopia.[10]
- Form deprivation myopia is a type of myopia that occurs when the eye is deprived of clear form vision.[11] Myopia is often induced this way in various animal models to study the pathogenesis and mechanism of myopia development.[11]
Classification Based Upon Degree
Myopia, which is measured in diopters by the strength or optical power of a corrective lens that focuses distant images on the retina, has also been classfied by degree or severity:
Low myopia
It usually describes myopia of −3.00 diopters or less.
Medium Myopia
It usually describes myopia between −3.00 and −6.00 diopters.[1] Those with moderate amounts of myopia are more likely to have pigment dispersion syndrome or pigmentary glaucoma.[12]
High Myopia
It usually describes myopia of −6.00 or more.[1] People with high myopia are more likely to have retinal detachments[13] and primary open angle glaucoma.[14] They are also more likely to experience floaters, shadow-like shapes which appear singly or in clusters in the field of vision. Roughly 30% of myopes have high myopia.[6]
Classification Based Upon Age of Onset
Myopia is sometimes classified by the age of onset:
Congenital Myopia
It is also known as infantile myopia, is present at birth and persists through infancy.[4]
Youth onset Myopia
It occurs prior to age 20.[4]School myopia appears during childhood, particularly the school-age years.[15] This form of myopia is attributed to the use of the eyes for close work during the school years.[1]
Adult onset Myopia
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Cline, D (1997). Dictionary of Visual Science (4th ed ed.). Boston: Butterworth-Heinemann. ISBN 0-7506-9895-0. Unknown parameter
|coauthors=ignored (help) - ↑ Summanen, P (2002). "Mechanisms of myopia in Cohen syndrome mapped to chromosome 8q22". Invest. Ophthalmol. Vis. Sci. 43 (5): 1686–1693. PMID 11980891. Unknown parameter
|coauthors=ignored (help) - ↑ Goss, DA (1988). "Myopia". In Amos, JB (ed). Diagnosis and management in vision care. Boston: Butterworths. p. 445. ISBN 0409950823. OCLC 14967262. Unknown parameter
|coauthors=ignored (help) - ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 American Optometric Association.Optometric Clinical Practice Guideline: Care of the patient with myopia. 1997.
- ↑ Li CY, Lin KK, Lin YC, Lee JS. "Low vision and methods of rehabilitation: a comparison between the past and present." Chang Gung Med J. 2002 Mar;25(3):153-61. PMID 12022735.
- ↑ 6.0 6.1 Verma A, Singh D."Myopia, Phakic IOL." eMedicine.com. August 19, 2005.
- ↑ The Eyecare Trust. Driving - The Facts. January 26, 2005.
- ↑ Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
- ↑ Vukojević, N (2005). "Axial eye length after retinal detachment surgery". Collegium antropologicum. 29 (Suppl 1): 25–27. PMID 16193671. Unknown parameter
|coauthors=ignored (help) - ↑ Metge, P (1993). "[Myopia and cataract]". La Revue du praticien (in French). 43 (14): 1784–1786. PMID 8310218. Unknown parameter
|coauthors=ignored (help) - ↑ 11.0 11.1 Shen, W (2005). "Inducing form-deprivation myopia in fish". Invest. Ophthalmol. Vis. Sci. 46 (5): 1797–1803. doi:10.1167/iovs.04-1318. PMID 15851585. Unknown parameter
|coauthors=ignored (help) - ↑ "Glaucoma." EyeMDLink.com. Retrieved August 27, 2006.
- ↑ Larkin GL."Retinal Detachment." eMedicine.com. April 11, 2006.
- ↑ "More Information on Glaucoma." AgingEye Times. Retrieved August 27, 2006.
- ↑ Morgan I, Rose K. "How genetic is school myopia?" Prog Retin Eye Res. 2005 Jan;24(1):1-38. PMID 15555525.