Ocular blood vessel arrangement in choroidal coloboma

Objective: To describe the ocular blood vessel arrangement in choroidal coloboma eyes.

Methods: In this retrospective, observational cross-sectional study, fundus images from 69 coloboma eyes of 45 patients were classified as per Ida Mann's classification. The arrangement and distribution of retinal, choroidal, and episcleral vessels, as well as vortex veins, were observed in non-colobomatous, colobomatous, and extra-colobomatous regions.

Results: Seventy-eight colobomas were identified. There were 12 type 1, 13 type 2, 10 type 3, 13 type 4, 11 type 5, 4 type 6 and 15 type 7 colobomas respectively. In most cases of type 1 and 2 colobomas, origin of retinal blood vessels could not be determined. In colobomas type 3-7, retinal blood vessels originated either from the optic disc centre or, rarely, from the optic disc or coloboma margin. Eyes with large and deep type 1, 2, 3 and 7 colobomas showed prominent choroidal vessels in the non-colobomatous region and around the coloboma. Small choroidal colobomas lacked prominent choroidal vessels. Similarly, prominent extraocular episcleral vessels within the coloboma bed were observed in eyes with colobomas of types 1, 2, 3 and 7. Vortex veins were visible in 70% of coloboma eyes. They were more commonly seen with small focal colobomas and less frequently with large deep colobomas.

Conclusion: Coloboma eyes have variations in the arrangement and distribution of ocular blood vessels. The position, size, and antero-posterior extent of the choroidal coloboma are the primary determinants of how these blood vessels are arranged. Future research would benefit from additional imaging with indocyanine green angiography.