WBR0149

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Biochemistry
Sub Category	SubCategory::General Principles
Prompt	[[Prompt::A 35 year old female patient presents to her ophthalmologist for decrease in vision. She has been noticing throughout the last month a deterioration of her vision especially when driving home from work at night. She denies any family history for any disease except for hypertension in her father and dyslipidemia in her mother. The review of system is insignificant except for dry skin and fine hair. What is the most likely diagnosis?]]
Answer A	AnswerA::Diabetic retinopathy
Answer A Explanation	[[AnswerAExp::Diabetic retinopathy is the most severe form of the several kinds of ocular complications causing damage to the retina, as a result of diabetes. It is an ocular manifestation of systemic disease which affects up to 80% of all diabetics who have had diabetes for 15 years or more. It is the leading cause of non traumatic blindness in adults. People with untreated diabetes are 25 times more at risk for blindness than the general population. However, this patient is young and the history does not suggest the presence of diabetes.]]
Answer B	AnswerB::Glaucoma
Answer B Explanation	[[AnswerBExp::Glaucoma is a group of diseases of the optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. Although raised intraocular pressure is a significant risk factor for developing glaucoma, there is no set threshold for intraocular pressure that causes glaucoma. One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. However, this patient is young and the history does not suggest the presence of glaucoma.]]
Answer C	AnswerC::Cataract
Answer C Explanation	[[AnswerCExp::A cataract is an opacity that develops in the crystalline lens of the eye or in its envelope. Cataract can be caused by advanced age and diabetes among other causes. However, this patient is young and the history does not suggest the presence of cataract.]]
Answer D	AnswerD::Nutritional deficiency
Answer D Explanation	[[AnswerDExp::Vitamin A deficiency is common in developing countries but rarely seen in developed countries. Approximately 250,000 to 500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A. Night blindness is one of the first signs of vitamin A deficiency. Vitamin A deficiency contributes to blindness by making the cornea very dry and damaging the retina and cornea. Vitamin A deficiency also diminishes the ability to fight infections. In countries where children are not immunized, infectious disease like measles have relatively higher fatality rates.]]
Answer E	AnswerE::Genetic disease
Answer E Explanation	AnswerEExp::Genetic diseases causing blindness occur at a younger age. In addition, there is no family history of vision problems in the family.
Right Answer	RightAnswer::D
Explanation	[[Explanation::Vitamin A deficiency is common in developing countries but rarely seen in developed countries. Night blindness is one of the first signs of vitamin A deficiency. Vitamin A deficiency is also associated with increased risk of infection, particularly measles, and with skin changes. Educational objective: Vitamin A deficiency is associated with night blindness, skin changes and increased risk of measles. Educational Objective: References: ]]
Approved	Approved::No
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