[The influence of ocular dominance on monovision--the interaction between binocular visual functions and the state of dominant eye's correction].

PURPOSE: To examine the interaction between binocular visual functions and the correction of the dominant eye, i.e., for far vs. near vision in monovision. SUBJECTS AND METHODS: Ten healthy subjects without any ophthalmological disease were examined. After cycloplegia, the eyes of the subjects were corrected by soft contact lenses (difference in lens power between the lenses: 2.5 D) with an artificial pupil(diameter: 3.0 mm). Visual acuity at various distances, contrast sensitivity, and near stereoacuity were measured while the dominant eye determined by the hole-in-card test (sighting dominance) was corrected for far and near vision. RESULTS: Binocular visual acuity was better than 1.0(20/20) at all distances. When the dominant eye was corrected for distance, the binocular visual acuity at 0.7 m was better than the monocular visual acuity; contrast sensitivity was better within the spatial frequency range of 0.5-4.0 cycles per degree, and near stereoacuity by Titmus stereo tests improved. CONCLUSION: These results suggest that dominant eyes should be corrected for far vision for better binocular summation at middle distances, and near stereoacuity.

[The influence of ocular dominance on monovision--the influence of strength of ocular dominance on visual functions].

PURPOSE: Monovision is a method of correction for presbyopia. We have reported the advantage of conventional monovision (the dominant eye is corrected for distance). In this study, we investigated the influence of interocular imbalance of dominancy on the visual function. SUBJECTS AND METHODS: Ten healthy subjects without any ophthalmologic disease participated. After cycloplegia, the eyes of the subjects were corrected by soft contact lenses with an artificial pupil (diameter: 3.0mm). The dominant eye was corrected for distance, and the difference in lens power between the lenses was 2.5 D. The subjects were classified into two groups by strength of the imbalance of sensory dominance, which was determined by using binocular rivalry. Binocular visual functions (visual acuity at various distances, contrast sensitivity, near stereoacuity) were compared between the two groups. RESULTS: Subjects with strong imbalance of sensory dominance showed decreased near visual acuity as well as decreased binocular summation of contrast sensitivity at low spatial frequencies. On the other hand, near stereoacuity was not affected by the imbalance of sensory dominance. CONCLUSION: These results suggest that strong imbalance of sensory dominance interferes with binocular visual functions in monovision. Thus, the evaluation of ocular dominance is crucial for clinical applications of monovision.

Quantitative measurement of ocular dominance using binocular rivalry induced by retinometers.

PURPOSE: To develop a new method using binocular rivalry and retinometers to quantitatively examine ocular dominance and to investigate the magnitude of ocular dominance in cataract patients preoperatively and postoperatively. SETTING: Eye Clinic, Kitasato University School of Medicine Hospital, Sagamihara, Kanagawa, Japan. METHODS: The duration of exclusive visibility of the dominant and nondominant eye target in binocular rivalry were measured in 60 healthy volunteers (study 1) and preoperatively and postoperatively in 10 cataract patients (study 2). Rivalry targets were presented directly to the retina of each eye using 2 retinometers. Subjects reported the exclusive visibility of 1 eye target, and the total duration of exclusive visibility for each eye in dominant and nondominant eye trials was evaluated. RESULTS: In study 1, the magnitude of ocular dominance was quantitatively assessed with 4 grades based on differences in total duration of exclusive visibility between dominant and nondominant eyes. In study 2, magnitude of ocular dominance could be evaluated in all cataract patients regardless of refractive and cataract conditions. Magnitude of ocular dominance displayed significant correlations between preoperative and postoperative conditions (simple regression, P<.001). CONCLUSIONS: Ocular dominance can be quantitatively evaluated using this new method based on binocular rivalry and retinometers, particularly in cataract patients. Magnitude of ocular dominance may indicate preoperatively whether a patient with cataracts will have sufficient ocular dominance to adjust to monovision correction.

Ocular dominance and patient satisfaction after monovision induced by intraocular lens implantation.

PURPOSE: To elucidate the relationship between ocular dominance and patient satisfaction with monovision induced by intraocular lens implantation. SETTING: Eye Clinic, Kitasato University School of Medicine Hospital, Sagamihara, Kanagawa, Japan. METHODS: The durations of exclusive visibility of dominant- and nondominant-eye targets were measured in 16 patients with successful monovision and 4 patients with unsuccessful monovision to determine the characteristics of ocular dominance. The dominant eye was determined using the hole-in-card test (sighting dominance). The contrast of target in nondominant eye was fixed at 100%; the contrast of target in the dominant eye varied (ie, 100% to 80% to 60% to 40% to 20%) using rectangular gratings of 2 cycles per degree that were 4 degrees in size. RESULTS: In the successful monovision group, the reversal thresholds (ie, exclusive visibility of the nondominant eye crosses over that of the dominant eye) were displayed only at low decreasing contrast (80% and 60%). However, in the unsuccessful monovision group, the reversal thresholds were at high decreasing contrast (20%) or not at all. The reversal thresholds in patients with unsuccessful monovision were at a significantly lower contrast than in patients with successful monovision (P<.05). CONCLUSIONS: Success and patient satisfaction in monovision patients were significantly influenced by the magnitude of ocular dominance. The balance technique seems to be a good method to evaluate the quantity of ocular dominance and prospectively evaluate the monovision technique.