A Case of Multiple Optic Disc Pits: 21-Year Follow-up

Optic disc pits (ODP) are an uncommon congenital abnormality. Patients remain asymptomatic unless they develop maculopathy. The use of optic coherence tomography has critical benefits in the follow-up of patients who are at the amblyogenic age. The aim of this study is to present a case of double ODP in the right eye and single ODP in the left eye in a partially accommodative esotropia patient followed for 21 years. To our knowledge, multiple ODP has never been described in a patient with partially accommodative esotropia.

Introduction

An optic disc pit (ODP) is a rare congenital defect that usually presents as an ovoid, grey-white excavation in the lamina cribrosa of the optic disc.[1] It is seen in 1 per 11,000 population and equally in both sexes, occurring singly and unilaterally in 85-90% of cases and bilaterally in 10-15% of cases.[1,2] Serous macular detachment is estimated to affect 25-75% of patients with ODP.[2] Vitreomacular traction and vitreous strands over the optic disc were reported by Theodossiadis et al.[3] in eyes with ODP-related maculopathy. However, there are very few studies showing that this rare, sight-threatening anomaly can sometimes be multiple. Only 12 cases of double ODP have been reported in the literature to date.[4,5,6]

The aim of this study was to present a case of double ODP in the right eye (RE) and single ODP in the left eye (LE) of a patient with partially accommodative esotropia who was followed-up for 21 years.

Case Report

A 25-year-old female was followed-up for partially accommodative esotropia from the age of 4 years. She underwent strabismus surgery at 6 years of age for residual esotropia at distance and near with full cycloplegic refraction. Bilateral ODP was found at her first visit. Her best-corrected visual acuity (BCVA) was 20/20 (Snellen chart) in both eyes. Anterior segment examination was unremarkable bilaterally. Intraocular pressure was 16 mmHg in both eyes. Cycloplegic refraction was +2.50 (+1.00x100) in the RE and +2.00 (+0.50x90) in the LE. Dilated fundoscopy revealed a double ODP in temporal and nasal rims of the right optic disc (Figure 1A) and single ODP in nasal rim of left optic disc (Figure 1B). The ODPs were also clearly visible in red-free fundus photography (Figure 1C, 1D).

Figure 1

Color fundus and red-free photographs of the right and left eye. A, B) Two optic disc pits located temporally (arrow) and nasally (arrowhead) in the right eye and one optic disc pit located nasally (arrowhead) in the left eye. C, D) The double optic disc pit in the right eye and single optic disc pit in the left eye are clearly observed

Spectral-domain optical coherence tomography (SD-OCT) (Heidelberg Engineering, Heidelberg, Germany) showed subfoveal deposits in the RE (Figure 2A). This accumulation probably occured after subretinal fluid resorption and spontaneously regressed (Figure 2B). The macula was stable in the LE. Swept-source OCT (Topcon Corp, Japan) through the optic disc showed two distinct hyporeflective areas in the RE suggestive of ODPs, one each in the temporal and nasal quadrants, as well as fluid accumulation under the optic nerve head and intrapapillary septum structure (Figure 2C). In the LE, a shallow ODP located nasally and associated vitreous fibers were seen (Figure 2D).

Figure 2

A) Spectral domain optical coherence tomography (SD-OCT) shows subfoveal deposits at age 19. B) Subfoveal deposits are not seen on SD-OCT at final follow-up 6 years later. C) Swept-source OCT (SS-OCT) of the right eye shows the temporal (arrowhead) and nasal (arrow) optic disc pits. Fluid under the optic nerve head appears as a hyporeflective area (star) and an intrapapillary septum structure is seen between the accumulation of fluid under the optic nerve head and the optic disc pit (circle). D) SS-OCT of the left eye shows a shallow optic disc pit (arrow) located nasally and associated vitreous fibers

The patient’s 30/2 visual field analysis (Humphrey field analyzer, Carl Zeiss Meditec, Dublin, CA) demonstrated an enlarged blind spot in the RE (Figure 3A) and no visual field defect in the LE (Figure 3B). Multifocal electroretinography (mfERG) (Vision Monitor, Monpack 3, Metrovision, France) revealed low amplitudes correlated with 2º of macula in the RE (Figure 3C) and normal results in the LE (Figure 3D). However, despite the pathological findings in the tests, the patient had no complaints. The patient was followed up annually by ophthalmic examination and OCT evaluation. Her BCVA remained stable (20/20) 21 years after the initial diagnosis.

Figure 3

A) In the visual field, blind spot enlargement is observed in the right eye. B) No visual field defect is seen in the left eye. C) Multifocal electroretinography (mfERG) revealed low amplitudes correlated with 2º of the macula in the right eye. D) mfERG is normal in the left eye

Discussion

ODPs have typically been an incidental finding on routine dilated fundus exam. To our knowledge, multiple ODP has never been described in a patient with partially accommodative esotropia.

In differential diagnosis, congenital optic disc anomalies (such as optic nerve hypoplasia, megalopapilla, morning glory syndrome, and coloboma), and acquired ODP (as in glaucoma, high myopia) should be eliminated.[7,8] In the differential diagnosis, it is easy to distinguish congenital and acquired ODP from optic disc coloboma. Optic disc coloboma typically affects the inferior nasal rim of the optic nerve while ODP most commonly affects the inferotemporal quadrant of the optic disc.[1] Patients often remain asymptomatic until macular changes are present. Interestingly, we diagnosed this case in the first decade, and the patient was asymptomatic despite findings of maculopathy in long-term follow-up. Despite attenuated amplitudes on mfERG, her BCVA was not affected. In our opinion, her BCVA may have been preserved as a result of self-healing serous retinal detachment attacks. Although spontaneous resolution with good visual acuity was reported in about 25% of cases, pediatric patients often develop maculopathy due to traction from the formed vitreous in younger eyes.[9]

Maculopathy secondary to ODP is treated with juxtapapillary laser photocoagulation (JLP), pars plana vitrectomy (PPV), or combined treatments, but there is no consensus on the optimal surgical technique. It has been reported that the combination of PPV, gas tamponade, and JLP is more effective than PPV and gas.[10] Recent studies have reported no additional benefit from JLP in long-term success rates.[11,12] Avci et al.[13] stated that PPV gives the best functional results in ODP maculopathy. They also emphasized that JLP may not be necessary for the success of PPV. Although there are studies showing that gas tamponade removes retinal and subretinal fluid from the macula,[14,15] there are also studies reporting that it does not significantly contribute to the final success rate.[10,16]

OCT is an non-invasive test to interpret the macular status, however it shows the relationship of ODP with vitreous and retina as well.[3,17] In some cases, a hyporeflective area within the optic disc excavation is visible, which may reflect accumulated fluid underneath the optic nerve head.[9] Other important OCT findings are intrapapillary cavities, intrapapillary proliferations, septum-like structures, and subretinal precipitates which can be detected as a marker for chronicity of maculopathy.[18,19] In our patient, one eye had fluid accumulation under the optic nerve head and an intrapapillary septum structure (Figure 2C).

Although macular and optic nerve head-related findings can be easily detected with OCT, the use of mfERG may be beneficial in patients who are uncooperative and at the amblyogenic age.

To the best of our knowledge, a total of 3 ODPs with bilateral involvement has never been described in association with partially accommodative esotropia. Therefore, in order to prevent amblyopia, patients should be closely followed from childhood. OCT and mfERG are useful tests for detecting retinal changes.