Do bifocals reduce accommodative amplitude in convergence excess esotropia?

Randomised controlled trial of an accommodative support lens designed for computer users

PURPOSE

Accommodative support (AS) lenses are a low add progressive addition spectacle lens designed to ease symptoms in computer vision syndrome (CVS). The study aims to investigate if (1) AS lenses improve CVS symptoms; (2) binocular/accommodative functions predict a benefit from AS lenses and (3) wearing AS lenses for six months impacts on binocular/accommodative functions.

METHODS

Pre-presbyopic adults with symptoms of CVS (Computer Vision Syndrome Questionnaire, CVS-Q^© , score ≥ 6) were randomly allocated to wear AS lenses or control single vision (SV) lenses. The CVS-Q^© and a battery of optometric tests were applied at baseline and after three and six months. Participants and researchers were masked to participant group. After six months, the SV group were unmasked and changed to AS lenses and one week later asked to choose which they preferred.

RESULTS

The change in CVS-Q^© scores from baseline to six months did not differ significantly in the two groups. At the end of the one week period, when the control group wore the AS lenses, control group participants were significantly more likely to prefer AS lenses to SV lenses. No optometric functions correlated with the benefit from AS lenses. AS lenses did not have any adverse effects on binocular or accommodative function.

CONCLUSIONS

In pre-presbyopic adults, there was no greater improvement in CVS-Q^© scores in the group wearing AS lenses than in the control group. No adverse effects on optometric function (including accommodation) are associated with wearing AS lenses.

Accommodative ET-High AC/A Ratio Esotropia: The Case for Glasses

BACKGROUND AND PURPOSE

There is a continuing debate as to whether the patient optically correctable at distance to within 8 prism diopters of perfect alignment requires treatment for persisting overconvergence at near, and if treatment is indicated, what it should be.

PATIENTS AND METHODS

For the patient whose misalignment at distance is reduced to 8 or fewer prism diopters, my preference is for the full cycloplegic correction plus a bifocal in the first prescription, to discourage virtually all accommodation initially, with pull back later.

RESULTS

Review of several reports indicates a continued lack of consensus on whether this causes disuse weakening of accommodation and premature presbyopia. Recent studies found that prolonged convergence tone at near can result in anatomic and physiologic alterations in the medial rectus muscles that threaten a satisfactory distance alignment as well, despite relief of the accommodative demand. Hypoaccommodative esotropia resembles the high AC/A variety.

CONCLUSION

Spontaneously improving over-convergence at near is not likely to occur in the hypoaccommodating patient either with observation alone or with surgery. I reserve surgery for the over-convergence at near for the unusual case of an extremely high distance-near disparity, and for the teenager or adult not showing likelihood that the condition will resolve.

Distance-near disparity esotropia: can we shrink the gap?

Distance-near disparity esotropias are a group of heterogenous usually acquired strabismus disorders, where the angle of misalignment at near exceeds that at distance by 10 prism diopters or more, where the accurate correction of refractive errors and ambylopia are important early objectives. These aetiologically diverse entities respond non-uniformally to strabismus surgery and bifocals. The management challenge is one of 'shrinking' the disparity so that the affected individuals can develop and comfortably maintain binocular single vision and/or optimal alignment. Surgical procedures have continued to evolve but none of the current operative procedures are superior for all patients. Subclassifying this strabismus and highlighting publication data from more homogenous clinical series may assist with the optimisation of future management and treatment outcomes.