A binocular test of sensory eye dominance based on the Pulfrich effect

Many studies have shown inconsistent results among traditional measures of sensory ocular dominance (SED), seriously questioning the very concept of SED as a unitary aspect of the visual system (e.g., Laby & Kirschen, 2011; Mapp et al., 2003; Walls, 1951).The test outcomes may also change even if the same measure is repeated under different conditions, for example by varying the distance and eccentricity of the target (e.g., Rice et al., 2008; Kahn & Crawford, 2001).On the other hand, some authors suggest that such inconsistencies may result from uncontrolled variables. A candidate to produce confusing variables is the frequent format of these tests, often dichotomous and introspective.In this paper, we propose a possibility of measuring SED on a continuous scale and in a comparative way using a stimulus that induces a Pulfrich effect. Here a dichoptic motion stimulus, borrowed from a previous study (Reynaud & Hess, 2017), was used, which produced different degrees of 3D illusory perception strength through the variation of retinal disparity. We observed that the responses of the subjects varied according to their classical SED test outcomes and we estimated the differences in terms of the time delay of the information coming from the two eyes. In our sample, it appears that information from the dominant eye was processed 8.2±5.8 ms faster than that of the fellow eye. People with a left dominant eye showed more marked differences in processing time (6.8±2.0 ms) than people with a right dominant eye (1.8±0.9 ms). Eyes without a clear dominance did not show significant differences in processing time (1.2±1.7 ms). These results are consistent with the previous literature and could lead to the development of a new continuous-scaled SED test.

Imbalanced Sensory Eye Dominance of Surgically Aligned Late-onset Acute Acquired Concomitant Esotropes with normal stereopsis

Background: Adults with late-onset acute acquired concomitant esotropia (AACE) have chance to develop normal binocular functions including a balanced ocular dominance before the onset of esotropia. For most patients, strabismus surgery re-establishing the ocular alignment indeed effectively restore stereopsis and visual acuity to the normal level. However, it is unclear whether they have already acquired balanced two eyes.Methods: 11 surgically aligned patients with AACE (24.3 ± 1.5 years; mean ± SE) and 14 adults with normal vision (26.1±1.2 years) participated in our experiments. All patients had normal binocularity and stereopsis. Using binocular phase combination paradigm, sensory eye dominance was quantified as the interocular contrast ratio, termed balance point, at which the contribution of each eye to the perception of cyclopean grating were equal.Results: Normal controls had a mean balance point value close to unity (0.95±0.01), while AACE group exhibited evident binocular imbalance (0.76±0.05), which was significantly different from control group (t (10.45) = -3.485, p = 0.006) . The balance point value didn’t depend on the interval from AACE onset to strabismus surgery (r = -0.357, p = 0.281) or the interval from the surgery to examination of sensory eye dominance (r = -0.105, p = 0.759).Conclusions: Although strabismus surgery effectively straightened AACE patients’ ocular alignment and even conferred them normal stereopsis, late-onset AACE patients’ two eyes were still not balanced. These results indicated that binocular imbalance might be a risk factor for adult AACE.

The Modulation of Laser Refractive Surgery on Sensory Eye Dominance of Anisometropia

Purpose. To evaluate the effect of laser refractive surgery on sensory eye dominance of anisometropia. Methods. A total of 156 subjects with nonanisometropic myopia and 70 subjects with anisometropic myopia were enrolled in the first part of the study. The dichoptic motion coherence threshold technique was applied to collect the normal dataset and distribution of sensory eye dominance. The second part of the study included 40 subjects with nonanisometropic myopia and 40 subjects with anisometropic myopia who received the femtosecond laser-assisted in situ keratomileusis (Fs-LASIK). A comprehensive ophthalmologic evaluation was performed with particular attention to sensory eye dominance preoperatively and one-week and one-month postoperatively. The ocular dominance index (ODI) was applied to evaluate the subject’s overall degree of sensory ocular dominance. Visual acuity, sighting eye dominance, and stereo acuity were also accessed. Results. In experiment one, the mean ODI in the nonanisometropic group and the anisometropic group was 1.48 ± 0.63 and 1.95 ± 1.07, respectively. The ODI values of the anisometropic group were significantly higher than those of the nonanisometropic group (Mann–Whitney U test, P<0.001). The demographics information and the distribution of ODI values in both groups are summarized in tables and figures. In experiment two, all LASIK procedures were uneventful and no postoperative complications were observed during the postoperative follow-up. Preoperatively, the ODI values of the anisometropic LASIK group were significantly higher than those of the nonanisometropic LASIK group, which was consistent with the results of part 1. However, one week after operation, the mean ODI values of the anisometropic LASIK group had significantly decreased from 1.89 ± 1.09 to 1.39 ± 0.44. And, the mean ODI values slightly increased to 1.65 ± 0.61 one-month postoperatively. In the nonanisometropic LASIK group, there were no statistically significant differences of ODI changes among preoperative, post-one-week and post-one-month visits. The demographics information and the changes of ODI of both LASIK groups are summarized in tables and figures. Conclusion. Stronger sensory eye dominance is seen in the subjects with anisometropic myopia compared to subjects with nonanisometropic myopia. The strong sensory dominance of anisometropia becomes more balanced at one week of postoperation but returns to the preoperative level after one month. Laser refractive surgery had a short-term modulation of sensory eye dominance.