An optic nerve pit is a depression on the optic disc that is formed from an abnormality in the development of the eyes. The defect causes a small amount of tissue from the retina to protrude backward. Wiethe initially described the condition in 1882. His description resulted from an observation of two optic disc depressions in a 62-year-old female patient. The condition is mostly unilateral, meaning it occurs in one eye. 15% of the cases have, however, been bilateral.
Abnormalities that can be seen with the pits are an enlarged optic nerve head and nerve head coloboma. Posterior vitreous detachments (PVD) and retinal detachments are closely related to optic nerve pits.
Also Known As
- Optic disc pits
- Optic holes
- Optic pits
Causes & Risk Factors
Optic nerve pit is an inborn condition that is thought to be caused by the superior edge of the embryonic fissure failing to close correctly.
Optic nerve pits are rare and occur in only about one out of 10,000 people. Its risk factors are unknown since it is congenital, but there have been suggestions that it may be an inherited condition with an autosomal dominant pattern.
Signs & Symptoms
Most patients do not show any symptoms, especially when the optic nerve pit is not affecting vision. However, when the optic pit is associated with vitreous or serous retinal detachment, the patient may complain of vision defects. Optic disc pit maculopathy is the term used for macular detachment in the optic disc pit.
The vision defects include arcuate scotomas and enlarged blind spot vision. Visual acuity usually is not affected, but it may reduce when serous macular detachment occurs. The symptoms are mostly present in the 3rd or 4th decade of life.
Since patients are mostly asymptomatic, diagnosis is clinical. The optic pit is often discovered during a routine examination from a fundus exam using a slit lamp or an indirect ophthalmoscope. The optic pit appears round or oval with a grey-white pigmentation. Its size also varies from 0.1 to 0.7 disc diameter.
The observation is usually one pit per disc, but there have been reported cases of two to three pits. The pit is located on the optic disc's temporal side, but it may also be at the center or along its margin.
Other techniques used for diagnosis are:
- A spectral-domain optical coherence tomography (SD-OCT) - When subretinal fluid is not easily visible on examination, SD-OCT is used to see if there are traces of the fluid.
- Fluorescein angiography - It is not useful in optic pits diagnosis but is used to rule out other diseases to differentiate them from serous detachment.
- Amsler grid - It is used to track the initial phase of macular involvement of an optic disc with serous detachment.
- Visual field tests - The tests show enlarged blind spots and central scotoma.
- Electrophysiological testing - A patient with poor electroretinogram(ERG) response is unlikely to have an improved visual acuity after macular reattachment.
Treatment for the optic pit is not necessary, and there is no prevention for fluid accumulation. However, treatment can be done to repair serous detachment. The techniques that can be used are:
- Laser photocoagulation - Studies have shown that this procedure results in a successful resolution of the serous detachment, but this does not necessarily improve the final visual outcome.
- Pars plana vitrectomy (PPV) with a posterior vitreous detachment and gas tamponade. A vitrectomy is used to reattach the macular, possibly leading to an improvement in the central vision. The purpose of the vitrectomy is to induce posterior vitreous detachment, and this relieves vitreous traction.
- Macular buckling - It is less common, but it prevents lens changes associated with PPV. It is also considered for younger phakic patients.
Prognosis & Long-Term Outlook
The number of optic discs that develop serous detachments is still not clear. A patient's vision recovery from a serous detachment depends on the detachment's severity and how successful reattachment was. If it is left untreated, it may result in vision impairment.
The patient's vision begins to deteriorate at 20-30 years of age. It is not common for children to experience visual defects. In some cases, the serous collections may disappear without treatment. The patient will need to have regular visits and also limit his/ her activities for monitoring purposes.
Prevention & Follow Up
Asymptomatic patients are recommended to have regular monitoring to check for any macular involvement. The monitoring procedures should include dilated retinal evaluations and threshold visual fields. It is also vital for parents to know and understand the signs and symptoms of their child's optic disc pit maculopathy to seek treatment early.