Case Report
A 22-year-old lady presented with poor vision in both the eyes since childhood. She had a history of squint surgery in both the eyes at the age of 7 years and corneal tear repair with lensectomy in the left eye 14 years ago. Her best-corrected visual acuity was 20/50, N6 in the right eye (+1.50ds/−1.00dc 180°) and 20/50p, N36 (+14 D contact lens) in the left eye. There was a large angle >70° constant exotropia in the left eye. The anterior segment showed heterochromic iris with coloboma in the inferonasal part [Figs. 1b and 2b]. Intraocular pressure was 14 mm of Hg in both the eyes. Fundus examination in the right eye showed a large type 5 choroidal coloboma involving complete disc, but sparing the macula [Fig. 1a]. The left eye showed type 1 choroidal coloboma sparing both disc and macula [Fig. 2a]. Both eyes showed hypopigmented albinotic fundus with prominent choroidal vasculature in the background. Optical coherence tomography (OCT) in both the eyes showed shallow foveal pit with persistence of plexiform layers along with outer nuclear layer widening and outer segment lengthening suggestive of grade 1 foveal hypoplasia [Figs. 1c and 2c]. There was incomplete posterior vitreous detachment in the left eye. OCT angiography of the macula (3 × 3 mm) in both the eyes showed the absence of foveal avascular zone (FAZ) in the superficial capillary plexus [Fig. 1d, e and 2d, e] and the presence of small area of FAZ in the deep capillary plexus [Figs. 1f and 2f]. There was no abnormality in the outer retina or choriocapillaries layer. In the area corresponding to coloboma, there was absence of any blood flow signals. A diagnosis of bilateral choroidal coloboma with ocular albinism was made. She was referred to low vision rehabilitation and contact lens clinic for further workup.
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Figure 1: (a) Color montage fundus photograph showing a large retinochoroidal coloboma involving disc with hypopigmented albinotic fundi. (b) Slit lamp retroillumination showing iris coloboma with heterochromic irides. (c) OCT of the macular area showing foveal hypoplasia with shallow foveal pit and persistence of plexiform layers. (d) A 12 × 12 mm OCT-A slab of the SCP showing absence of FAZ as well as dark hyporeflective area corresponding to coloboma. A 3 × 3 mm OCT angiography of macular area in SCP (e) showing absence of FAZ, whereas in DCP (f) a partial area of FAZ was present
Figure 2: (a) Color montage fundus photograph showing a large retinochoroidal coloboma sparing the disc and macula with hypopigmented albinotic fundi. (b) Slit lamp retroillumination showing iris coloboma with heterochromic irides and small peripheral iridectomy. (c) OCT of macular area showing incomplete vitreous detachment with foveal hypoplasia and persistence of plexiform layers. (d) A 12 × 12 mm OCT angiography slab of the SCP showing presence of distorted FAZ. A 3 × 3 mm OCT-A of macular area in SCP (e) showing distorted FAZ, whereas in DCP (f) a partial area of FAZ was present
Discussion
Congenital ocular colobomas are due to failure of a part of fetal fissure to close during 5–7 weeks of gestation. The prevalence is 1 in 2077 live births.[1] Ocular colobomas are frequently seen in association with other developmental defects such as microphthalmos and anophthalmia.[23] Oculocutaneous albinism is inherited as X-linked recessive condition mostly seen in males; however, females may get affected in case of skewed X chromosome inactivation or inheriting two mutant copies of GPR143 gene. It leads to melanin biosynthesis which is characterized by a generalized reduction in pigmentation of the hair, the skin, and the eyes. The prevalence is 1 in 17,000 per person.[4] Ocular manifestations include nystagmus, iris transillumination defects, foveal hypoplasia, high myopia, and prominent photophobia.[4]
To our understanding, only one case of oculocutaneous albinism with unilateral iridofundal coloboma is reported (PubMed, Science Direct, Google Scholar).[5] In our case, there was bilateral choroidal coloboma with ocular albinism. As both the entities are very rare and congenital in origin, any association between the two is less likely. The only common factor between the two could be PAX6 gene. The PAX6 gene, normally expressed in the developing central nervous system including the eye, is vital to eye development. Of particular interest are rare missense mutations in PAX6 which have been shown to cause optic nerve and chorioretinal coloboma[6] as well as other disorders such as hereditary keratitis, aniridia, Peter's anomaly, albinism, and foveal hypoplasia.[7]
In our case, although OCT showed a shallow foveal pit and persistence of plexiform layers, OCT angiography confirmed presence of superificial capillary plexus in foveal area with an intact foveal avascular zone in deep capillary layers; this could explain preserved visual acuity in spite of foveal dysplasia. We describe a rare combination of bilateral coloboma choroid with ocular albinism. This combination is not often reported in literature.
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
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Conflicts of interest
There are no conflicts of interest.
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