A rare case of isolated foveal hypoplasia

A 13-year-old boy presented to us with complaints of low vision in the right eye noticed 2 years ago. He had no significant history of the previous systemic or ocular disease. There was no family history of genetic eye disorder or systemic pathology. His unaided visual acuity was counting fingers right eye and 20/20 left eye. The right eye's visual acuity did not improve with any refractive correction. The pupils were normal size and normally reactive. Extraocular movements were normal. Anterior segment examination was unremarkable. Dilated fundus examination of the right eye showed abnormal glistening reflexes in the perifoveal area [Fig. 1]. The optic disc and retinal periphery were normal. Fundus examination of the left eye was normal. Spectral-domain optical coherence tomography (OCT) of the right eye revealed the absence of the foveal pit and the persistence of inner retinal layers in the foveolar area [Fig. 1]. The left eye OCT was normal. Fundus fluorescein angiography (FFA) demonstrated a poorly developed foveal avascular zone (FAZ) in the right eye and normal FAZ left eye [Fig. 2]. Multifocal electroretinography (mfERG) right eye demonstrated reduced P1 amplitudes in the central rings 1, 2, and 3 [Fig. 3]. We made a diagnosis of right eye isolated unilateral foveal hypoplasia.Figure 1: Optical coherence tomography of both eyes. (a) Right eye: shallow foveal pit, the persistence of inner layers in the foveal area. (b) Left eye: normal foveal depression and the absence of inner layers in the fovea.Figure 2: Fundus fluorescein angiography demonstrates a poorly developed foveal avascular zone right eye and normal left eyeFigure 3: Multifocal electroretinogram right eye shows reduced central P1amplitudes as compared to age-matched normal controlDiscussion The normal foveal development begins at fetal week 25 and is completed 15–45 months after birth. The development of the foveal pit involves the centrifugal displacement of inner retinal layers and a centripetal displacement of cone photoreceptors.[1] Foveal hypoplasia results from the arrest of this developmental process. The majority of the cases are bilateral and associated with ocular conditions such as aniridia, oculocutaneous albinism, microphthalmos, achromatopsia, congenital nystagmus, Stickler syndrome, or retinopathy of prematurity.[1] Our case had none of these associations. Thomas et al.[2] proposed an OCT-based structural grading system for foveal hypoplasia. The present case had a shallow foveal pit, with the persistence of all inner layers and the outer plexiform layer. Outer nuclear layer widening was present, whereas outer segment lengthening was absent, which makes it grade 3 foveal hypoplasia. Previously, a few cases of isolated unilateral foveal hypoplasia have been reported.[3,4,5] Isolated foveal hypoplasia is commonly sporadic; however, PAX6 missense mutation has been reported.[6] OCT, FFA, and mfERG helped us in diagnosing this uncommon condition. 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. Acknowledgment The authors would like to thank Dr. Sangeet Mittal, Thind Eye Hospital, for conducting fundus fluorescein angiography and multifocal electroretinography for the case.