Question

A patient came with nyctalopia. Fundus image given below, what will be the diagnosis?

• A. Retinitis pigmentosa
• B. Vit A deficiency
• C. Retinal detachment
• D. Diabetic retinopathy

Hint:

Night blindness plus bony-spicule pigment, thin vessels and a waxy disc on fundus = a hereditary rod-cone dystrophy.

Answer 1

The Correct Option is A

Step 1: Identify the key symptom. Nyctalopia means night blindness, i.e. defective vision in dim light. It arises when the rod photoreceptors (responsible for scotopic/low-light vision) are damaged or dysfunctional.

Step 2: Read the fundus picture. The fundus shows the classic triad of retinitis pigmentosa: (i) bony-spicule pigmentation in the mid-peripheral retina, (ii) attenuated (thin) retinal arterioles, and (iii) a waxy pale optic disc. These features, together with lifelong progressive night blindness, point to retinitis pigmentosa.

Step 3: Confirm the correct option. Retinitis pigmentosa is a hereditary, progressive rod-cone dystrophy. Rods degenerate first, producing early nyctalopia and ring (tubular/tunnel) field loss, followed later by central vision loss. The fundus appearance matches option A.

Step 4: Exclude the distractors. Vitamin A deficiency also causes nyctalopia, but its ocular signs are conjunctival xerosis, Bitot spots and corneal xerosis/keratomalacia - not bony-spicule retinal pigment; so B is wrong. Retinal detachment shows an elevated, billowing grey retina and sudden curtain-like field loss, not symmetrical pigment spicules; C is wrong. Diabetic retinopathy shows microaneurysms, dot-blot haemorrhages, hard exudates and neovascularisation, and presents with blurring rather than isolated night blindness; D is wrong.

Final answer: Option A - Retinitis pigmentosa.