Visual acuity is generally stable in adults with coloboma, but these individuals are still at risk of being labeled glaucoma suspects and developing early-onset cataracts, a study from the National Eye Institute (NEI) suggests. The researchers also report that retinal complications in these patients may not be as prevalent as previously suspected.

Coloboma is a rare and potentially blinding disorder, and while comorbidities are broadly recognized in children, the condition hasn’t been explored as much for adults.

The researchers reviewed NEI electronic medical records of coloboma patients who were older than 18 at their last visit.

The study cohort included 62 patients (104 eyes) who appeared to have “isolated” coloboma, which was defined as the absence of any systemic abnormalities readily discernible on a physical exam.

Most of the patients, 68%, presented with bilateral coloboma, and 56% of eyes had involvement of both the anterior and posterior segments.

The investigators found visual acuity was stable and no other signs of a progressive disease at the follow-up visits. Forty-seven patients (76%) had at least one eye with visual acuity of more than 20/60, nine (15%) were visually impaired, and six (10%) were legally blind. Visual acuity of the eye with coloboma ranged from 20/20 to no light perception. Of the 104 eyes with coloboma, 48% had 20/40 vision or better and 23% had 20/400 vision or worse.

Most patients had myopia (55%), followed by no refractive error (34%) and hyperopia (11%).

Children with coloboma commonly have strabismus and cataracts, the latter affecting up to 16% of pediatric patients. The current study found a similar pattern in adults: 37% of adult patients had strabismus or a history of strabismus and 50% had cataracts. The researchers noted 25 out of the 31 patients with cataracts had anterior segment coloboma.

While the reason for the higher incidence of cataracts wasn’t clear, the investigators hypothesized the abnormal development of the eye may affect the lens cells’ physiology, which could diminish clarity. Cataract extraction should be approached with extra caution due to possibly associated lens coloboma and phacodonesis, the researches noted.

Looking at suspect glaucoma cases, 13 patients had pachymetry of more than 600μm in at least one eye, six of which had microcornea. The approximate endothelial cell density was within normal limits (2645cell/mm²) and there was no evidence of endothelial dropout. Intraocular pressure was borderline high (18mm Hg to 22mm Hg) in six of these patients. This, along with the finding of hypoplastic or dysplastic optic nerves (present in 81% of individuals), put patients with coloboma at risk of being tagged as glaucoma suspects and over-treated with ocular hypotensive drops.

Five patients had retinal detachment (8%), and all had coexisting ocular conditions, such as high myopia or a history of trauma. Three of these patients were not treated due to poor visual prognosis while the remaining two had their retina successfully reattached.

Other less frequent complications in the posterior segment included choroidal neovascularization, vitreous hemorrhages and subretinal fluid.

Adults appeared to have more systemic issues than children: 74% compared with 38%, respectively. Overall, there was no significant deterioration in the patients’ health over the study period, and all patients lived an independent life, including those with poor visual acuity.

This study provides the first extensive data on the visual and systemic prognosis for adult patients with ocular coloboma, the researchers said.