Sir,

X-linked retinoschisis (XLR) is a leading cause of macular degeneration in male children. Stellate foveal schisis is pathognomonic, with a peripheral retinoschisis in half the cases. However, a high degree of clinical variability is observed.1 We report a rare case of full-thickness macular hole secondary to foveal schisis in XLR.

Case report

A 10-year-old male child presented with congenitally poor vision OU. He had a male maternal cousin with similar complaints. The best-corrected visual acuity (BCVA) was 6/18 OD, and 6/60 OS. Anterior segment was unremarkable bilaterally. Fundus examination revealed bilateral vitreous veils and generalized retinal pigment epithelial (RPE) degeneration. Right eye demonstrated a subtle foveal schisis (Figure 1a). Left eye showed a large macular hole, with a faint vertical retinal fold at its nasal margin (Figure 1b). Electroretinogram revealed selectively reduced b-wave amplitude. Optical coherence tomography (OCT) showed macular schitic cavities lined by vertical columns OU (Figure 2); the left eye additionally had a large full-thickness macular hole. Retina around the hole was atrophic, especially temporally. There was no vitreomacular traction (Figure 2b). Examination of the cousin's eyes revealed bilateral foveal schisis typical of XLR; with a similar b-wave suppression on electroretinogram. BCVA was 6/18 bilaterally.

Figure 1
figure 1

(a) Red-free fundus photograph of the right eye shows a subtle foveal schisis and vitreous veils. (b) Left eye shows a large macular hole (horizontal diameter: 1450 μm). Note a vertical fold of retina at the nasal border of the hole, and lustreless, atrophic appearance of the temporal retina with pigment mottling.

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Figure 2
figure 2

Horizontal optical coherence tomographic scans through foveal centre: (a) The right eye showing microcystic cavities with bridging vertical septae in the outer retinal layers. (b) The left eye has a full-thickness macular hole with perifoveal cystic spaces in both outer and inner retinal layers, and thinning of the temporal retina. Note the elevated nasal edge of the hole, caused by the vertical retinal fold.

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As the hole was detected incidentally, and vision was stable, the patient was followed up without intervention. A year later, he showed no change in the clinical/electrophysiological status.

Comment

Gass suggested a key role of ‘Muller-cell cone’ in the pathogenesis of age-related macular hole as well as congenital XLR. Muller cell cone is the site for foveal splitting and cyst formation in both the pathologies.2 Inner-retinal degenerative cystic changes and vitreoretinal traction act in tandem to cause an idiopathic macular hole.3 In XLR, accumulation of defective retinoschisin protein within and around Muller cells results in cystic spaces in multiple retinal layers.1, 4 Further, cortical vitreous is strongly adherent to the internal limiting membrane in some cases of XLR, and exerts a tangential traction on the macula, dragging it nasally, particularly when vitreous veils create temporal redundancy.5, 6 Similar traction probably resulted in vertical pleating of retina at the macular hole's nasal rim in our patient. It is possible that a full-thickness foveal cyst, formed by coalescence of multilayered microcysts, was de-roofed by a strong nasal vitreous traction. A macular hole is, however, extremely rare in XLR. Vitreomacular traction is not very strong in most cases; and splitting of the inner retinal layers might slacken the vertical vector of vitreous traction.7 We could find only one additional report of a macular hole in XLR. Unlike our case, the previous report demonstrated definite anteroposterior vitreomacular traction causing the hole, with localized retinal detachment.7 Probably due to pre-existing degenerative changes, our patient experienced no further visual deterioration attributable to macular hole, and was conservatively managed.