The role of enucleation in the development of nystagmus in children with retinoblastoma.

BACKGROUND

Early enucleation has been linked to infantile nystagmus, or a pattern resembling fusion maldevelopment nystagmus syndrome (FMNS). We evaluated nystagmus characteristics and risk factors in a large cohort of children treated for retinoblastoma (RB).

METHODS

The medical records of children who underwent unilateral enucleation for RB between 2009 and 2021 were retrospectively reviewed. Nystagmus type-FMNS or infantile nystagmus syndrome (INS)-was determined clinically. Potential risk factors included age at presentation, age at enucleation, visual acuity, laterality, and genetic status.

RESULTS

Of 149 children who underwent enucleation of one eye (114 with unilateral, 35 with bilateral RB), 13 (9%) developed nystagmus over a mean follow-up of 67 months. Twelve showed INS and 1 had probable FMNS. All affected children carried a pathogenic RB1 variant, compared with 25% of those without nystagmus (P < 0.0001). Nystagmus onset occurred at a mean age of 3.75 months and was linked to earlier RB diagnosis (mean, 4.7 vs 29 months [P < 0.0001]), earlier enucleation (P < 0.0001), and poorer visual acuity (P < 0.0001). Of 11 infants enucleated before 6 months (median, 3 months), only 2 (18%) developed nystagmus despite healthy fellow foveas, with one showing FMNS features.

CONCLUSIONS

In our study cohort, nystagmus occurred in a minority of children, predominantly at presentation rather than as a consequence of enucleation, and was strongly associated with RB1 mutation and early disease onset. These findings provide reassurance for families that unilateral enucleation in infancy rarely induces nystagmus when the fellow eye is healthy.