BENEFITS OF LENS

Early results of a large multicentre trial suggest that a new extended-range-of-vision intraocular lens (Symfony, AMO) provides good functional vision and spectacle independence across a wide range of distances for most patients, with better intermediate vision than many competing bifocal multifocal IOLs, Béatrice Cochener MD, PhD told the XXXIII Congress of the ESCRS in Barcelona, Spain.

She reviewed the results of 229 patients bilaterally implanted with the Tecnis Symfony lens and followed them for four to six months after surgery. The sample includes 60 patients targeting micro-monovision. Overall, the ongoing study involves 481 patients treated at 42 European centres, said Dr Cochener, who is an active research consultant for the Abbott-sponsored trial.

Nearly 95 per cent of patients reported never or only occasionally needing spectacles for distance vision, while 93 per cent reported spectacle independence for intermediate and 75 per cent for near, said Dr Cochener, Professor and Chairman of the Department of Ophthalmology at Brest University Hospital, France.

Postoperative mean uncorrected visual acuity was decimal 0.95 for distance, 0.79 intermediate and 0.7 near. A subset of patients targeted for micro-monovision, or -0.25 to -0.75 dioptre in the non-dominant eye, had slightly worse mean uncorrected distance vision at 0.92, but better intermediate at 0.85 and near at 0.8.

ELONGATED FOCUS

Compared with a similar aspheric monofocal lens, the Symfony lens’ diffractive echelette optic elongates its focal point by about 1.0D, improving visual acuity continuously across the entire defocus curve, Dr Cochener explained. Combined with the eye’s approximately 0.5D of natural pseudoaccommodation, this yields binocular functional vision over about 2.5D of defocus – which translates to 20/40 or better from 40cm to infinity. Micro-monovision can further extend this range.

The arrangement eliminates the intermediate distance defocus dip typically seen with multifocal designs, which split incoming light into two or three discrete focal points. However, it also weakens near vision performance compared with most multifocal lenses.

The functional advantage of targeting micro-monovision with the Symfony lens is reflected in lower near vision spectacle use. Nearly 25 per cent of all patients said they needed glasses for near vision half the time or frequently, compared with less than 17 per cent of the micro-monovision subgroup, Dr Cochener reported.

Micro-monovision was associated with a gain of about one line of vision. The micro-monovision subgroup also ended up slightly more myopic than all patients, with a post-op mean spherical equivalent of -0.55 +/- 0.52 compared with -0.36 +/- 1.27.

The Symfony optic also corrects for chromatic aberration, reducing image blur resulting from the approximately two-dioptre difference in refraction between the shortest and longest visible wavelengths. This improves modulation transfer function, in turn improving contrast sensitivity, which is comparable to a monofocal lens and superior to most multifocal designs.

Photic phenomena were also less common with the Symfony IOL than typically observed with conventional multifocals. Most often reported were halos at 10 per cent of all patients, with 6.1 per cent moderate and 3.9 per cent severe. Moderate and severe glare was reported by 3.3 and 2.2 per cent respectively; starbursts by 1.3 and 0.4 per cent; and “other” by 2.4 and 0.2 per cent. The micro-monovision subgroup reported halo and “other” slightly more often and glare slightly less often.

Patients were also very satisfied, Dr Cochener said. On a zero to 10 point scale with 10 best, mean satisfaction with distance vision was 8.92, intermediate 8.83 and near 7.9 for all patients. At a mean 8.57, micro-monovision patients were slightly more satisfied with near vision, but slightly less satisfied with distance at 8.33.

Overall satisfaction of surgeon performance was also high, with a mean of 8.76 for mini-monovision and 8.89 for all patients. Nearly 95 per cent of all patients would recommend Symfony to friends or family, while 96 per cent would choose the same lens again.

Béatrice Cochener:
beatrice.cochener@ophtalmologie-chu29.fr