An Ophthalmologist Diagnosed as A ‘simple myopia with regular astigmatism’. Which of following glasses to be prescribed?
Correct Answer: -2D spherical -90deg cylindrical
Description: (B) -2D spherical -90deg cylindricalHere, the options provided in the answers are a bit confusing.The correct answer should be a cylindrical only, mentioning its axis, since the diagnosis is a simple myopic astigmatism - where power at one axis will be plane or nill and another corresponding axis to have a power.When eye-wear prescriptions are written, they can be classified into different areas depending on the power or refractive error.There are seven categories to which prescriptions can fall:1. Simple Hyperopia, the Rx will be (+) sphere2. Simple Myopia, the Rx will be (-) sphere3. Simple Myopic Astigmatism, the Rx will be piano (-)4. Simple Hyperopic Astigmatism, the Rx will be (+)5. Compound Hyperopic Astigmatism, major meridian power will be (+)(+) on both 90 and 180 degree axis.6. Compound Myopic Astigmatism, major meridian power will be (-)(-) on both 90 and 180 degree axis.7. Mixed Astigmatism, major meridian powers will be opposites (-)(+)(+)(-) on both 90 and 180 degree axis.Curvature ametropia has a special importance because it is the cause of another very troublesome error of refraction called astigmatism.In most eyes the areas of the refractive surfaces uncovered by the pupil and used in vision are very nearly spherical.When the cornea has its direction of greatest and least curvature at right angles to one another, the condition is called regular astigmatism.In the commonest form when the vertical meridian is the more curved, the condition is generally called regular astigmatism
Category:
Ophthalmology
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