CONTRAST SENSITIVITY AFTER IMPLANTATION OF DIFFRACTIVE BIFOCAL AND MONOFOCAL INTRAOCULAR LENSES

Purpose: To compare contrast sensitivity (CS) after implantation of a diffractive bifocal intraocular lens (IOL) and a monofocal IOL of simi lar design. Setting: Seven European centers. Methods: In this randomiz ed, prospective study, CS was tested 5 months after cataract and IOL i mplantation surgery in 115 patients with a diffractive bifocal IOL and 106 patients with a monofocal IOL. It was also tested in a subgroup o f 38 patients who had bilateral implantation of a diffractive bifocal IOL. Contrast sensitivity was tested using the Vision Contrast Test Sy stem (VCTS). Results: In patients with a best corrected visual acuity (BCVA) of 1.0 or better, the CS at all spatial frequencies (1.5 to 18 cycles/degree), both at distance and near, was slightly lower in the b ifocal IOL group than in the monofocal group. Mean values were within the normal range. In patients with a BCVA of less than 1.0, the CS was lower and the difference between the bifocal and monofocal groups was less. In patients with bilateral bifocal IOLs, CS was better when tes ted bilaterally than when testing the better eye alone. ,Pupil size af fected the results to a small degree. Contrast sensitivity appeared to improve over time after implantation of a diffractive Conclusions: In patients with cataract and no other eye pathology, the diffractive bi focal IOL will slightly reduce the CS at ail spatial frequencies. In t hose with reduced visual acuity after cataract surgery, CS will be red uced accordingly In this situation, the reduction from the diffractive bifocal optic would be minor.