Stereopsis in bilaterally multifocal pseudophakic patients.

BACKGROUND

The purpose of this study was to evaluate stereoacuity in patients with bilateral implantation of an aspheric bifocal intraocular lens (IOL).

METHODS

Thirty patients scheduled for cataract surgery were implanted with the aspheric bifocal AcrySof ReSTOR IOL. Stereoacuity was measured using the vectographic Titmus and Random dot stereotests (fixed disparity) and the Howard–Dolman apparatus (threshold disparity) under photopic conditions (85 cd/m2) after phacoemulsification for cataract surgery in 30 patients with low astigmatism (≤1D). Visual acuity at distance and near was also examined. All patients were examined at 1-year follow-up.

RESULTS

Mean stereoacuity with the Titmus and the Random dot sterereotests was 44.55 ± 1.08 sec arc (range, from 40 to 80) and 41.25 ± 1.12 sec arc (range, from 20 to 70) respectively. The Howard–Dolman method showed a mean value of 18.42 ± 6.10 sec arc, ranging from 11 to 30 sec arc. No statistically significant differences were found between the Titmus and the Random dot sterereotests values (P = 0.189). However, these values differ significantly from that found using the Howard-Dolman method (P = 0.005). Visual acuity at distance and near was 0.04 ± 0.05 and 0.04 ± 0.04 logMAR (about 20/20) respectively.

CONCLUSIONS

Despite simultaneous images on the retina after bifocal IOL implantation, patients showed useful stereoacuity. This study confirms that retinal image blur associated with multifocality does not deteriorate stereoacuity. Stereoscopic threshold measurement with a Howard–Dolman apparatus is more accurate than vectographic tests when assessing stereoacuity after IOL surgery.