Aborted bridge coloboma with scleral fistula.

A 66-year-old with best-corrected visual acuity 20/20 in both eyes was detected with retinochoroidal coloboma (RCC) [Fig. 1], 1 disc diameter (DD) inferior to disc. The coloboma could be clearly divided into two parts, the superior part showing a scleral fistula. In the central part of the coloboma, there was a bridge of retinal tissue extending from the nasal edge of the coloboma for approximately 3.5DD. The temporal part of the bridge was devoid of any retinal tissue [Figs. 1 and 2]. The remaining fundus was unremarkable. Intraocular pressure (IOP) was 8 mmHg. The axial length was 22.83 mm. “En-face” optical coherence tomography (OCT) [Fig. 3] and B-scan [Fig. 4 and Supplementary Video 1] revealed a discontinuity of the sclera in the region of the fistula. The OCT scan [Fig. 2] passing through the area of the aborted bridge of retinal tissue showed poorly differentiated retinal tissue in the nasal half and the intercalary membrane with schisis in the center of the bridge, extending toward the temporal periphery of the coloboma. The transitional zone in the temporal periphery showed subclinical retinal detachment. Partially preserved choroid with large choroidal vessels could also be seen in the region of the aborted bridge.

Figure 1

Optos image showing retinochoroidal coloboma with scleral fistula (red arrowhead) and aborted bridge (white arrowhead)

Figure 2

Structural OCT image of the aborted bridge area showing poorly differentiated retinal tissue (white star), the intercalary membrane with schisis (pink star), area of subclinical retinal detachment (pink polygon), sclera (pink arrowhead), and choroidal tissue (yellow arrowhead)

Figure 3

En face OCT and structural OCT showing fistula opening (white star)

Figure 4

Ultrasound B-scan showing the coloboma with fistula (white arrowhead)

Discussion

Ultra-wide-field image of RCC with scleral fistula has never been reported. We could find only two reports[12] of scleral fistula in RCC, both needing treatment for the closure of the fistula. The low IOP noted in this patient did not cause hypotony maculopathy noted by Gupta et al.[1] and inflammation noted by Mori et al.[2] En face OCT showed the fistulous opening that had never been described. In the region of the aborted bridge of retinal tissue, the choroidal layer could be detected on structural OCT. The temporal periphery of the RCC showed a subclinical retinal detachment, which has been described by Gopal et al.[3] B scan ultrasonography showed a well-defined area of retinochoroidal excavation inferior to the disc, with an area of absence of all three coats of the eye, suggestive of scleral fistula.

Conclusion

The use of Optos, OCT, and B-scan together can help us understand and evaluate these patients in a better way.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.