An immature cataract involves which percentage of lens volume and may allow observation of the tapetal reflex?

An immature cataract involves which percentage of lens volume and may allow observation of the tapetal reflex?

• A. More than 15% but less than 99%
• B. Less than 15%
• C. Exactly 50%
• D. 100%

Answer: (A)

The key idea is how much of the lens is opaque and how that affects light reaching the retina and the ability to see the fundal reflex. An immature cataract means the opacity involves more than a small portion of the lens but not the entire lens. Practically, this corresponds to the lens being more than about 15% opaque but less than about 99% opaque. Because there are still clear areas, light can pass through enough to view the fundus and observe the tapetal reflex. If the opacity were under 15%, it would be incipient and the reflex would typically be clearer; if the entire lens were opaque (about 100%), the reflex would be absent.

The key idea is how much of the lens is opaque and how that affects light reaching the retina and the ability to see the fundal reflex. An immature cataract means the opacity involves more than a small portion of the lens but not the entire lens. Practically, this corresponds to the lens being more than about 15% opaque but less than about 99% opaque. Because there are still clear areas, light can pass through enough to view the fundus and observe the tapetal reflex. If the opacity were under 15%, it would be incipient and the reflex would typically be clearer; if the entire lens were opaque (about 100%), the reflex would be absent.