Optic Disc Pit
● Congenital defects arising from failure of fetal fissure closure in embryogenesis
● Mostly unilateral. 10-15% bilateral
Pathophysiology:
● Occur due to incomplete closure of the optic fissure resulting in a micro-communication between the subarachnoid space and the pit.
● Communication of optic pits and Cerebral Spinal Fluid (CSF) is controversial. Beta-2 Transferrin levels (found in CSF) of submacular fluid associated with optic pits has been variable.
● Histologically, there is herniation of a dysplastic retina into the subarachnoid space through a defect in the lamina cribrosa at the pit.
Symptoms:
● Usually asymptomatic.
● Patients may complain of metamorphopsia, micropsia, blurred or decreased vision, or a
blind spot if the optic pit is associated with a serous detachment.
Signs:
● Usually found inferotemporally within the nerve, 1⁄3 are central
● Round or oval depression that differs in colour from the surrounding disc
(grey, yellow or black)
● Colour variation depends on the amount and location of glial tissue in the pit
● Size can vary from 0.1-0.7 disc diameters and depth from 0.3-0.5 diopters
● Associated macular edema, serous macular detachment; schisis or pigmentary changes in
the macula
● Shallow serous macular detachments can be seen in upto 3⁄4 eyes with inferotemporal pits
Investigations:
● OCT: to determine if trace amounts of subretinal fluid is seen, can show schisis-like separation between inner and outer retina.
● Visual fields – Enlarged blind spot, arcuate scotomas .
● Amsler grid can be used to monitor the onset of macular involvement of an optic pit with serous detachment.
Management:
● No medical therapy indicated unless it is associated with optic disc maculopathy
More on optic disc maculopathy in the next
post!
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