Question

A young patient presents to the ophthalmology clinic with loss of central vision. There is no obvious family history. The electroretinogram (ERG) was observed to be normal. Which is the most probable diagnosis?

• A. Best's disease
• B. Stargardt's disease
• C. Retinitis pigmentosa
• D. Macular hole

Hint:

Macula-only disease leaves the full-field ERG normal; think of the commonest juvenile macular dystrophy.

Answer 1

The Correct Option is B

Step 1: Identify the clinical picture. A young patient with progressive loss of central vision and a normal full-field ERG points to a disorder confined to the macula rather than to the entire retina.
Step 2: Apply the ERG rule. The full-field ERG measures the summed response of the whole retina. A purely macular disease affects too few cells to alter the full-field ERG, so it stays normal early on. A widespread photoreceptor disease lowers the ERG.
Step 3: Evaluate the options. Stargardt's disease (juvenile macular dystrophy) is the most common inherited macular dystrophy in the young; it causes bilateral central vision loss, often appears sporadic because it is autosomal recessive, and the full-field ERG is characteristically normal early. This fits all three clues: young age, no obvious family history, and normal ERG.
Step 4: Exclude the rest. Best's disease (vitelliform dystrophy) classically shows an abnormal electro-oculogram (EOG) with a low Arden ratio and is autosomal dominant, so family history is usually present. Retinitis pigmentosa is a diffuse rod-cone dystrophy that markedly reduces or extinguishes the ERG. A macular hole is a structural defect usually seen in older patients, not a young one without trauma.
Conclusion: The young age, sporadic presentation, and a normal ERG make Stargardt's disease the most probable diagnosis.