OPTIC PIT

SIGNS AND SYMPTOMS
Congenital pits of the optic nerve vary in size, shape, depth and location. They often appear as small, hypopigmented, yellow or whitish, oval or round excavated defects, most often within the inferior temporal portion of the optic cup. Approximately 20 to 33 percent are found centrally, with an average size of 500µm (one-third disc diameter).

Typically, optic pits occur unilaterally (85 percent). The optic disc in these patients appears larger than normal, and 60 percent of discs with optic pits also have cilioretinal arteries. These patients have a greater propensity to develop normal-tension glaucoma.

Most patients are unaware of the presence of an optic pit. Although as many as 60 to 70 percent of patients with optic pits possess some arcuate scotoma corresponding to the loss of retinal ganglion cells, their acuity is rarely affected. Patients may notice visual distortions, metamorphopsia or blurred vision. Those with temporal pits have the greatest risk for developing serous maculopathy.

PATHOPHYSIOLOGY
The origin of optic pits remains unclear. Optic pits have been associated with colobomatous lesions, suggesting that they result from incomplete closure of the fetal fissure. Others propose that they result from abnormal differentiation of primitive epithelia papilla. Arcuate visual field defects are the result of corresponding loss of retinal ganglion cells or secondary atrophy of attenuated nerve fibers.

Some 40 to 60 percent of patients with optic pits develop non-rhegmatogenous serous macular detachments. These fluid-filled cystic maculopathies can develop into lamellar macular holes. The origin of the fluid is unknown. There is a high incidence of posterior vitreous detachment associated with these serous maculopathies.

Previous theories concerning the origin of the subretinal fluid seen in optic pit-related serous macular detachment include liquefied vitreous penetration and leaking vessels within the pit. New findings strongly suggest that serous macular detachments secondary to optic pits develop due to pre-existing schisis-like lesions which connect the macula to the optic disc. Fluid, predominantly from the outer plexiform layer, enters an already edematous retina through the optic pit via the retinal stroma, producing a macular detachment.

MANAGEMENT
Begin the management of asymptomatic optic pit with a comprehensive eye examination, including threshold visual fields. Semi-annual intraocular pressure checks and dilated evaluations with drawings or photos are appropriate. Use home acuity assessment and home Amsler grid testing to monitor for the onset of maculopathy. Educate patients about the signs and symptoms of macular complications (e.g. blurred vision, visual distortions, metamorphopsia).

Treatment for optic pit-related macular detachment varies. Periodic monitoring, prophylactic laser photocoagulation, therapeutic laser photocoagulation after maculopathy has formed, oral steroids and vitrectomy have all been tried. The current trend is laser photocoagulation following the onset of maculopathy.

CLINICAL PEARLS

Differential diagnosis includes optic disc anomalies that mimic optic pit: choroidal and scleral crescent, tilted disc syndrome, circumpapillary staphyloma, hypoplastic disc and glaucomatous optic neuropathy. Idiopathic central serous retinopathy and subretinal neovascular membrane are alternative considerations for serous macular detachment.
Any change in appearance of the optic pit over time suggests that the lesion may be an acquired notch of the neuroretinal rim secondary to glaucomatous processes.