Visual acuity in children with coloboma: clinical features and a new phenotypic classification system

The aims of this study were to describe the clinical features and biometric findings in the eyes of children with coloboma and to develop a classification of coloboma that correlates with visual function.

Retrospective observational case series.

One hundred thirteen children and young adults (48 female, 65 male) aged 0 to 20 years with 196 eyes having coloboma.

Children with coloboma were recruited from schools for the blind, integrated education programs, schools for the mentally handicapped, community-based rehabilitation services, and hospital clinics in Andhra Pradesh, India, between January 1998 and January 1999. Visual function was assessed, including distance and near visual acuity (VA), and navigational vision. The corneal diameter and axial length of eyes were measured wherever possible.

Anatomic site of coloboma, association with microcornea and/or microphthalmos, VA, presence of navigational vision and reading vision.

Of 196 eyes with colobomatous malformations, 11 had microphthalmos with cyst, and 185 eyes had coloboma (associated with microcornea in 155 eyes and with a normal corneal diameter in 30). Microphthalmos was present in 72 of the 185 eyes with coloboma, of which 71 of 72 also had microcornea. The prognosis for vision depended on the phenotype of the better eye. Microphthalmos with cyst had the worst prognosis (VA < 3/60, 100%; reading and navigational vision, 0%). Microcornea with microphthalmos had a worse prognosis than microcornea without microphthalmos (VA < 3/60: 66.7% vs. 23.3%; unable to read N10: 66.7% vs. 34.1 %; no navigational vision: 30.6% vs. 6.73%). Simple coloboma (no microcornea or microphthalmos) had the best prognosis (VA < 3/60: 6.7%; able to read N10: 93.3%; navigational vision: 100%). A corneal diameter <6 mm had a poor visual prognosis, whereas a corneal diameter >10 mm had a good prognosis.

A phenotypic classification of coloboma is proposed, which in this study showed a good correlation with visual acuity, reading, and navigational vision. Microphthalmos with cyst had the worst prognosis, coloboma with microcornea and microphthalmos a poor prognosis, coloboma with only microcornea had an intermediate prognosis, and simple coloboma had the best prognosis.