Optic Pits (also known as optic nerve pits, optic disc pits, or less commonly optic holes) are congenital defects presumably arising from the failure of fetal fissure closure in embryogenesis.
Wiethe first described the clinical presentation of two optic disc depressions in a 62-year-old female patient in 1882.
Congenital optic pits are thought to result from an imperfect closure of the superior edge of the embryonic fissure.
Optic pits are rare, occuring in about 1 in 10,000 people with no gender prediliction. They can be diagnosed in children or adults. There are no known risk factors though genetic linkage has been investigated.
Closed optic nerve pits can be associated with meningeal cysts. The communication of Optic Pits and Cerebral Spinal Fluid (CSF) is controversial and Beta-2 Transferrin the levels (used for CSF detection in leaks from skull fractures) of submacular fluid associated with optic pits has been variable.
Optic pit formation occurs in utero and there is no known primary prevention.
The diagnosis of an optic pit is based on morphology of the nerve and is observed via clinical examination. They are usually unilateral though 10-15% are bilateral.
Patients are generally asymptomatic and findings are usually incidental concurrent with a routine exam. However a patient may complain a of distortion of lines or images (metamophopsia), distortion in the size of images (micropsia), blurred or decreased vision, or a blind spot if the optic pit is associated with a serous detachment.
Optic pits are generally found temporally within the nerve though up to one-third are central. They appear as a round depression that differs in color from the surrounding disc (grey, yellow or black).
A pit can be seen with direct or indirect ophthalmoscopy or using slit-lamp lenses (78, 90, 60 diopter lenses among others).
Pits are often asymptomatic though they can be associated with vision loss from a secondary serous retinal detachment (sometimes referred to as Optic Disc Pit Maculopathy). In other cases visual field deficits can be detected on perimetry.
Spectral-domain optical coherence tomography (SD-OCT) can be used to determine if trace amounts of subretinal fluid exists when it is not apparent clinically. OCT of an optic pit may show a schisis-like separation between the inner and outer retina.
Visual filed testing can show an enlarged blind spot as well as a relative cental scotoma in the presence of a serous detachment.
Fluorescein Angiography (IVFA) is not particularly useful in diagnosing optic pits though it may be helpful in eliminating other diseases in the differential of serous detachement.
Finally a patient (or physician) can use an Amsler grid to monitor the onset of macular involvement of an optic pit.
The diagnosis of an optic pit is clinical. Though no laboratory test exisits there are studies in progress looking at genetic markers.
The disease in the differential diagnosis of an optic pit incluude: optic nerve coloboma, choroidal and scleral crescent, tilted disc syndrome, circumpapillary staphyloma, hypoplastic disc, and glaucomatous optic neuropathy (which may also lead to an aquired pit or pseudopit). Idiopathic central serous retinopathy and subretinal neovascular membrane are among alternative considerations for serous retinal detachment involving the macula.
No treatment is required for an isolated optic pit.
There is no medical therapy that is indicated for this structural defect.
Laser and surgical therapy
It may be possible to repair a serous detachment when associated with a pit. Technniques include laser photocoagulation, which can be applied to the temporal margin of the optic disc in the effort to disrupt the communication between the source (the optic pit) and the collection of fluid under the macula.
Pars plana vitrectomy (PPV) with or without gas tamponade (using gases such as C3F8 or SF6) may be used to treat serous detachemtn associated with an optic pit. Successful macular reattachment leading to possible improved central vision can be achieved using vitrectomy. The purpose of this is to induce a posterior vitreous detachment (PVD) and help remove vitreous traction. Peeling of the internal limiting membrane may also be employed in addition to removing the vitreous for relieving all tractional components.
Another surgical technique is macular buckling. This type of posterior scleral buckle is placed when the pathology only involves macula. Though less commonly used it is an option for repair that may obviate the lens changes associated with pars plana vitrectomy, which may be an attractive benefit in younger, phakic patients.
Given the proximity to the optic nerve and macula, great care must be taken during application of photocoaguation.
Isolated optic pits have an excellent prognosis and usually have no sequelae. It is unclear how many optic pits develop serous detachments as these instances are sympotomatic and therefore seek out the care of an ophthalmologist more frequently than those asymptomoatic (reports of up to 50% of cases are from retrosepctive reviews and most likey subject to selection bias). The visual recovery of a serous detachment from an opitc pit is dependent on the chronicity of the detachment and sucess of the repair. Some serous collections, when associated with traction, may resolve without treatment if the traction resolves (for example with formation of a complete, spontaneous PVD).
American Academy of Ophthalmology http://www.aao.org
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