Medical Retina and the Posterior Segment:
                              Case fifteen
 

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This 20 year-old man was referred by his family doctor because of poor nigh vision. On examination, his visual acuity was 6/9 in both eyes. Electrophysiology showed decreased a and b waves in electroretinography and there was abnormal dark adaptation. The feature of the left fundus is shown above.

a. What does the picture show?

b. What is the most likely diagnosis?

c. What is the differential diagnosis?

d. What is the visual prognosis in this patient?