Occult Optic Disc Pit Maculopathy in a Glaucomatous Disc.

Optic pits are congenital defects of the optic disc. Diagnosis of optic pit maculopathy is quite challenging in the absence of a clinically visible or optical coherence tomography (OCT) proven pit. One such scenario is when there is advanced glaucomatous cupping. We present a case in which OCT helped detect optic disc pit maculopathy in a 60-year-old female.

Introduction

Optic pits are congenital defects of the optic disc. Macular schisis has been associated with some optic disc pits. What predisposes to the development of maculopathy and the pathogenesis remain elusive. Diagnosis of optic pit maculopathy is quite challenging in the absence of a clinically visible or optical coherence tomography (OCT) proven pit. Various observations have been made in the morphology of such discs associated with maculopathy. These include the presence of cavitations in the disc stroma and presence of an incomplete membrane over the disc. We present a case of optic pit maculopathy in a patient with a large cup due to advanced glaucoma. Here, diagnosis of optic nerve pit was made based on indirect evidence seen on OCT scans.

Case Report

A 60-year-female patient was incidentally noted to have a serous macular detachment in the right eye during her routine follow-up visits at the glaucoma clinic. She had primary angle closure glaucoma in both her eyes with a cup to disc ratio of 0.9 in both eyes. Furthermore, fundus evaluation showed a serous detachment of macula with the edge pointing toward the disc in the right eye [Figure 1a]. No disc pit was seen clinically, and the rest of the fundus examination was normal. Fundus examination of the left eye was normal except for the glaucomatous cupping. The patient was diagnosed to have central serous retinopathy clinically.

Figure 1

(a and b) Fundus images showing a macular detachment pointing towards the disc in the right eye (arrow). (c and d) Optical coherence tomography scans showing the presence of cavitation in the disc stroma (asterisk) and an incomplete membrane over the cup (arrow head) in the right eye. Similar changes were absent in the left eye

OCT scans through the macula showed a serous detachment of the macula with outer retinal schisis along the nasal edge of the detachment in the right eye [Figure 2]. The serous detachment narrowed down to the temporal edge of the disc with no clear continuation thereafter. Scans through the disc showed a deep nasal cup and a cavitary defect in the disc stroma. There was a thin fenestrated membrane traversing the cup [Figure 1c]. These findings were absent in the left eye [Figure 1b and d]. Fluorescein angiography of both eyes did not reveal any source of leakage. A diagnosis of right eye occult pit maculopathy in a glaucomatous disc was made.

Figure 2

Optical coherence tomography scan of the right macula showing serous macular detachment (asterisk) with outer retinal schisis along the nasal border of the detachment (arrow head)

Discussion

Maculopathy secondary to cavitary disc anomalies is still poorly understood due to the varying anatomy of the anomalous discs. Recently, OCT has given us a better understanding of the structural alterations seen in optic nerve head pits and associated macular changes. This has helped form various hypotheses regarding the pathogenesis of maculopathy.

There have been a few case reports describing typical maculopathy without a visible disc pit (clinically or on OCT).[12] Zaidi et al. observed anomalous cavitations in the stroma of the optic nerve head.[2] Anomalous cavitations at the temporal edge of the disc have been described by Hedels and Krohn.[3] In this report, the author claimed that the absence of an intact membrane over the disc could contribute to the development of a schisis like maculopathy. In the present case, OCT clearly demonstrates anomalous cavitation in the stroma of the optic nerve head pit and an incomplete membrane over the disc which were absent in the fellow eye. The presence of an incomplete membrane may allow the fluid to collect in the stromal cavitations and subsequently enter the subretinal and outer retinal spaces through microseepage. Hence, we can hypothesize that the right eye probably had a congenitally anomalous disc (possibly a disc pit). The disc pit was concealed by the progressive enlargement of the cup due to glaucoma. However, we do not have preglaucomatous disc photographs to confirm the same. Mechanism of development of maculopathy in cases with optic disc pit has long been a source of speculation. Defects in the membrane overlying the disc pit seem to allow vitreous fluid to enter the retina causing a schisis like separation of the layers. Doyle et al. postulated that an intact membrane over the optic disc prevented the development of maculopathy in the presence of optic disc pit anomaly.[4] In the present case, development of a discontinuity in the membrane could be the cause for the recent development of maculopathy.

Hence, the presence of pit-like cavitations in the disc stroma and absence of intact membranes over the cup can help diagnose optic pit maculopathy in discs with advanced glaucomatous damage. Early recognition of this OCT feature can help avoid misdiagnosis as macular edema due to other retinal or choroidal causes. This can prevent delay in treatment. Although the definitive treatment of optic disc maculopathy remains ambiguous, pars plana vitrectomy with or without gas tamponade has shown promising results.[5] Larger case series are needed to study the variations in pit morphology in glaucomatous eyes.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.