A Preoperative Phoropter Binocular Tolerance Test Predicts 96.9% Success In Laser Blended Vision

To evaluate whether a standardised preoperative phoropter-based binocular tolerance test can predict the success of laser-blended vision (LBV) in patients undergoing LASIK.

Wellington Eye Clinic, Dublin, Ireland

Retrospective analysis of consecutive patients undergoing LASIK with blended vision targeting. Preoperatively, binocular distance correction (0/0) was defined as 100% quality. Simulated anisometropia was introduced into the phoropter, and patients rated binocular quality relative to full-distance correction. Sensory dominance was established and assigned to the distance eye. Simulated blended vision ≥80% of binocular distance proceeded to surgery. The near-eye target was the maximum tolerated myopic offset, maintaining ≥80% binocular quality. Failure was defined as an enhancement converting the near eye to distance. Preoperative refractive status was classified as myopic (< −0.50 D), emmetropic (−0.50 to +0.50 D), or hyperopic (> +0.50 D)

1,341 patients (2,682 eyes) underwent LASIK with blended vision targeting. Distance correction was applied to the right eye (67.8%) and the left eye (32.2%). Preoperative refractive status was myopic in 695 patients (51.8%), hyperopic in 600 (44.7%), and emmetropic in 46 (3.4%). Induced anisometropia clustered between −1.50 D and −1.75 D, representing 62.5% of treatments and suggesting a functional range for blended vision. Failure occurred in 42 of 1,341 patients (3.1%), defined as enhancement converting the reading eye to distance. Failure rates were similar across refractive groups (3.45% myopes, 3.00% hyperopes, 0% emmetropes). Failures were not associated with greater anisometropia and most occurred within the first postoperative year.

A simple preoperative phoropter-based binocular tolerance test is a powerful predictor of successful laser-blended vision. Patients rating simulated anisometropia ≥80% of binocular distance vision achieved a 96.9% success rate without reversal. Identifying sensory dominance and selecting the highest anisometropia tolerated at this threshold allows surgeons to individualise treatment rather than rely on fixed monovision targets, improving predictability in laser-blended vision.