Impact of intraocular scatter on stereopsis

Influence of Interocular Differences and Alcohol Consumption on Binocular Visual Performance

The purpose of this study was to assess the influence of a moderate breath-alcohol content (BrAC of 0.40 mg/L) on binocular visual performance for different visual functions after inducing different levels of interocular differences with the use of filters. A total of 26 healthy young subjects were enrolled. The participants participated in two sessions: one without alcohol consumption and another after alcohol consumption. In each session and for the different filter conditions (subjects were wearing Bangerter foil of 0.8 and BPM2 fog filter on the dominant eye), monocular and binocular visual function was evaluated by measuring visual acuity, contrast sensitivity, visual discrimination capacity (and successively by calculating their corresponding binocular summations) and stereopsis (near and distance stereoacuity). In addition, interocular differences were calculated for different retinal-image quality and straylight parameters. All monocular and binocular visual functions were analyzed and stereopsis was significantly impaired by alcohol and filters (p < 0.05). Interocular differences for different ocular parameters and binocular summations for visual parameters were negatively affected by filters but not alcohol. Significant correlations (averaging all the experimental conditions analyzed) were found, highlighting: the higher the interocular differences, the lower the binocular summation and the poorer the stereopsis and, therefore, the worse the binocular visual performance.

Effect of interocular differences on binocular visual performance after inducing forward scattering

Purpose

To assess binocular visual performance by means of binocular summation on visual function after inducing monocular forward scattering, and to study the influence of interocular differences on ocular parameters.

Methods

Seven young healthy subjects were recruited. Four Bangerter foils and five fog filters were used to induce monocular forward scattering. To analyse the impact of the scatter, visual acuity, contrast sensitivity, visual discrimination capacity and distance stereoacuity were measured binocularly with the filter placed over the dominant eye. Additionally, interocular differences were calculated for four ocular parameters: the Objective Scatter Index (OSI), Strehl ratio (SR), modulation transfer function cut‐off (MTF cut off) and straylight (log[s]). Binocular summation was determined for these visual functions.

Results

A statistically significant deterioration in visual acuity, contrast sensitivity and stereoacuity was seen for all of the filter conditions with respect to the natural state (baseline), with the largest change being recorded for the Bangerter foils. Similarly, the interocular difference for the three retinal image quality parameters (OSI, SR and MTF cut‐off) and log(s) increased significantly for the Bangerter foil condition, but not for the fog filters (except log(s)). Binocular summation declined gradually with the Bangerter foils, but not for the fog filters. Statistically significant correlations were found, that is, the greater the interocular differences, the lower the binocular summation of the visual functions and the greater the distance stereoacuity.

Conclusion

Increased forward scattering in the dominant eye resulted in interocular differences, which reduced the overall binocular visual performance, including the binocular summation of several visual functions and distance stereoacuity. The results suggest that marked interocular differences in ocular parameters should be avoided in cases of ocular pathology, amblyopia and emmetropisation procedures (such as refractive surgery) or a monovision correction for presbyopia.

Stereopsis after corneal refractive surgeries: a systematic review and meta-analysis

PURPOSE

To systematically review the published manuscripts on stereopsis after corneal refractive surgery.

METHODS

The Web of Science, PubMed, Scopus, ProQuest, Clinical Key, Embase, and Cochrane Library were searched for relevant articles published until August 2020. The fixed- or random-effects models were used to estimate the Weighted mean difference (WMD) or Relative risk (RR) and 95% Confidence interval (CI) for postoperative stereopsis changes and incidence when applicable. Meta-regression was conducted for adjusting the effects of potential confounders.

RESULTS

Seven studies (1266 eyes) in adults and ten studies in pediatrics (259 eyes) were included. In adults, stereopsis improved significantly compared to the preoperative state (WMD = - 27.4, 95% CI = - 40.0, - 14.7; I² = 97.8%; P < 0.001). In pediatrics, proportion of patients with stereoacuity postoperatively was 2.18 times compared to preoperative evaluation. (RR = 2.18, 95% CI = 1.2, 3.9; I² = 68.6%, P < 0.001).

CONCLUSIONS

Stereopsis improves after corneal refractive surgery in adults and pediatrics.