A 20 year old boy complaints of sudden pain in the left eye with loss of vision. On examination, was hazy and there was a bulging of left lower eyelid on looking down . Retinoscopy shows scissoring reflex; oil drop sign was positive. diagnosis?
**Core Concept**
Retinoscopy is a technique used to determine the refractive error of the eye. In this case, the presence of a scissoring reflex and oil drop sign suggests an irregular astigmatism, which is a common cause of sudden vision loss in young individuals.
**Why the Correct Answer is Right**
The scissoring reflex is a characteristic finding in irregular astigmatism, where the light reflex splits into two distinct images that appear to be moving in opposite directions. This is due to the irregular curvature of the cornea or lens, which causes the light to be refracted in different ways. The oil drop sign is also a classic sign of irregular astigmatism, where the light reflex appears to be wavy or irregular. In this case, the presence of these signs suggests that the patient has a condition known as keratoconus, which is a progressive thinning of the cornea that can cause irregular astigmatism and vision loss.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because keratoconus is a more likely diagnosis than a simple refractive error such as myopia or hyperopia. While myopia and hyperopia can cause vision loss, they are not typically associated with the scissoring reflex and oil drop sign.
**Option B:** This option is incorrect because a cataract would typically cause a decrease in vision due to the opacity of the lens, rather than an irregular astigmatism.
**Option C:** This option is incorrect because a retinal detachment would typically cause a sudden loss of vision, but the scissoring reflex and oil drop sign are not typically associated with this condition.
**Clinical Pearl / High-Yield Fact**
The scissoring reflex and oil drop sign are classic signs of irregular astigmatism, and should prompt further investigation for conditions such as keratoconus.
**Correct Answer:** D. Keratoconus