Ocular Focusing Behavior of the One-Eyed Child

Abstract

Purpose 

To compare the accommodative gain and pupil miosis of children with only one functional eye with the binocular and monocular accommodative and pupil responses of typically developing age-matched controls.

Methods 

Forty-one uniocular cases and 43 controls (3–14 years for both cohorts) watched a cartoon movie on an LCD screen that ramped between 90 and 30 cm, with a stable period of 4 seconds at both viewing distances. Cases performed the task with their only functional eye whereas controls performed the task binocularly and monocularly. A subset of subjects also repeated the task while reading 20/40-sized letters on the LCD screen. Accommodative and pupil responses were recorded using the Plusoptix PowerRef3 photorefractor.

Results 

Accommodative gain of cases [median (25th–75th IQR): 0.73 (0.60–0.85)] was larger than the monocular gain of controls [0.56 (0.47–0.79)] (P = .03). Both responses were lower than the binocular gain of controls [0.95 (0.81–1.11)] (P < .001). Uniocular pupil miosis of cases [0.14 mm (0.06–0.24 mm)] were similar to monocular [0.12 mm (0.05–0.29 mm)] (P = .69) and smaller than binocular [0.23 mm (0.14–0.34 mm)] (P < .001) responses of controls. The increase in accommodative gain from movie watching to reading was significant only for controls (P = .02) but not for cases (P = .15). Age and time of visual deficit were poorly correlated with accommodative gain and pupil miosis of cases (r ≤ 0.25; P ≥ .1 for all). Age was also poorly correlated with the binocular and monocular accommodative and pupil performance of controls (r ≤ −0.3; P = .33).

Conclusions 

The accommodative gain of children with permanent loss of binocularity is in between the binocular and monocular gains of typically developing children. Their accommodative gains do not show any significant increase with a cognitively demanding task even while such a behavior is observed in controls. Pupil responses of uniocular children are similar to the monocular responses of age-matched controls.