Clinical Analysis of the Effects of Different Types of Contact Lenses on the Correction of Myopia With Small-Angle Strabismus and Visual Function

Objective: To investigate and compare the effects of bifocal soft contact lenses, single-focus soft contact lenses, and orthokeratology lenses (OK lenses) on patients with small-angle intermittent exotropia (IXT) accompanied by myopia, providing a basis for reducing secondary surgeries in clinical practice. Methods: A prospective, randomized, controlled study was conducted on 142 patients with small-angle IXT who had undergone IXT surgery and had concomitant myopia. Patients were randomly assigned to three groups using a computer-generated random number sequence with allocation concealment: the bifocal soft contact lens group (group A), the single-focus soft contact lens group (group B), and the OK lens group (group C). During the one-year treatment period, multiple visual function parameters were measured, including best-corrected visual acuity (BCVA), contrast sensitivity, accommodative function, eye position control ability, strabismus angle, and axial length (AL). Results: There were no significant differences in BCVA among the three groups, indicating similar basic visual acuity correction effects. Compared with the other two lens types, defocus soft contact lenses led to reduced contrast sensitivity at high spatial frequencies. Orthokeratology lenses resulted in decreased accommodative amplitude, increased accommodative lag, and reduced accommodative facility compared with the other lenses. The strabismus angle decreased in all patients, with improved positive fusional convergence. Groups A and B showed better improvements in eye position control and strabismus angle reduction than group C. Defocus soft contact lenses and OK lenses were comparable in controlling AL growth. The strabismus angle positively correlated with near stereopsis acuity and eye position control scores and negatively correlated with near horizontal positive fusional convergence. Conclusion: After the initial IXT surgery, patients wearing defocus soft contact lenses with a concentric bifocal design can effectively control AL growth, enhance eye position control ability, improve visual function, and achieve good subjective visual outcomes.