Stereoacuity and foveal fusion in adults with long-standing surgical monovision.
OBJECTIVE
Although binocular vision deficits occur in children who have a constant esotropia onset following significant maturation of stereopsis, it is uncertain whether adults are susceptible to changes to binocular vision. We examined binocular vision in adults with longstanding surgical monovision (> or =6 month's duration) to determine whether the binocular visual system remains susceptible to change.


METHODS
Participants included 32 adults with longstanding monovision through laser-assisted in situ keratectomy or photorefractive keratectomy and 20 age-matched control subjects. After full binocular correction, binocular function was measured by using the Randot Stereoacuity Test, the Randot Preschool Stereoacuity Test, and the Worth 4-dot test at near and distance. Monovision patients were grouped as having low anisometropia (<1.5 spherical D) or moderate anisometropia (> or =1.5 spherical D).


RESULTS
Non-parametric analysis of variance revealed a significant difference between group median stereoacuity (H = 16.062; P <.001). Pairwise multiple comparisons indicated both groups with monovision had significantly worse stereoacuity compared with control subjects (P <.05). Median stereoacuity values were 100 seconds of arc for patients with low anisometropia, 150 seconds of arc for patients with moderate anisometropia, and 40 seconds of arc for control subjects. A larger proportion of patients with moderate anisometropia failed the Worth-4 dot test at distance than control subjects (z = 2.619; P =.009).


CONCLUSIONS
Reduced stereoacuity and an absence of foveal fusion in adults with longstanding surgical monovision suggest continued susceptibility of the binocular visual system to anomalous binocular experience.
Fawcett
S L
SL
Retina Foundation of the Southwest, Dallas, Texas 75231, USA. fawcett@retinafoundation.org
Herman
W K
WK
Alfieri
C D
CD
Castleberry
K A
KA
Parks
M M
MM
Birch
E E
EE
D000328:Adult; D015858:Anisometropia / Q000503:physiopathology*; D003867:Depth Perception / Q000502:physiology*; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D008875:Middle Aged; D018903:Photorefractive Keratectomy; D011305:Presbyopia / Q000601:surgery; D015348:Vision, Binocular / Q000502:physiology; D015349:Vision, Monocular / Q000502:physiology*