IOL COMPLICATIONS

With 473 lenses implanted over nine years, Ivan Ossma MD, MPH reports excellent visual outcomes and low complication rates with the dual-optic Synchrony (AMO, Santa Ana, California, US) accommodating intraocular lens (IOL). But careful management of residual myopia and YAG capsulotomies for the few who develop posterior capsular opacification (PCO) further improve outcomes, he told the ASCRS annual symposium. While the dual-optic lens provides a functional range of vision with very low incidence of unwanted optical phenomenon and low PCO rates, patient expectations should be managed, Dr Ossma said.

Patients should be counselled that they may require a refractive enhancement for residual myopia and induced cylinder, may need spectacles for near vision, and may experience transient myopia after surgery. The current Synchrony lens is a one-piece silicone design with a 5.5mm 32 D anterior optic connected by spring haptics to a 6.0mm negative posterior optic of various powers, producing net power ranging from 16.0 D to 28.0 D. The lens is implanted completely in the capsular bag and is designed to move with contraction of the ciliary muscles, theoretically producing 3.5 D accommodation with 1.5mm of anterior lens movement. To avoid complications with the lens, the capsulorrhexis must be well-centred and 4.5mm in diameter, Dr Ossma said.

For the lens to move, the edge of the anterior lens must be covered by the remaining capsule. Also, the underside of the capsular bag should be polished to remove cells and minimise any fibrotic changes that would reduce the flexibility or clarity of the bag. However, transient myopia in the early postoperative and occasional myopic surprises are seen, Dr Ossma said. In his most recent 151 patients, mean myopia at one week was -0.56 D with some close to -1.5 D. “Over the past nine years the lesson I have learned is that in the first six weeks post-op, expect -0.5 to -1.25 D myopia.†For patients with more than -1.25 D at six weeks, Dr Ossma counsels them, and prescribes spectacles if necessary and reassesses at 12 weeks. If the patient is more than -0.75 D and unhappy, he offers a laser enhancement of myopia and any induced astigmatism targeting a spherical equivalent of -0.25 D.

Patients undergoing laser enhancements achieve the same range of visual outcome as those who receive the lens only, he noted. For those patients prescribed spectacles, he counsels wearing them for all activities to help the patient learn to accommodate in the first two months after surgery, rather than using myopia for close work. Over the first three months, the myopia tends to abate, ending up in Dr Ossma’s patients at about -0.3 to -0.4 D, he said. In his last 151 patients, followed for four years, Dr Ossma found five required posterior YAG capsulotomies for PCO, a rate of 3.3 per cent. Mean time to YAG was 833 days +/- 186 days, ranging from 584 to 1023. “This lens has the lowest PCO rate of any I have seen.†Still, some surgeons are concerned that a YAG capsulotomy could interfere with the Synchrony lens’ movement in the eye. Dr Ossma’s experience suggests otherwise.

“We do a low energy, small diameter, continuous, rounded YAG,†Dr Ossma said. The procedure significantly improved best corrected distance visual acuity, from logMAR 0.12 to logMAR -0.04, or from about 20/25 to better than 20/20. At the latest visit, visual acuity at all ranges was not statistically different between the five eyes that underwent YAG and the 146 that did not, suggesting that the procedure does not adversely affect the functional outcome of the Synchrony lens. Dr Ossma emphasised the need for low energy and a small posterior capsulotomy. His usually run from 2.5mm to 3.5mm.

Improved design

Dr Ossma also presented six-month outcomes data for the next-generation dual-optic lens, called the Synchrony Vu. It is designed to improve near vision by enhancing the depth of focus without compromising the monofocal optical quality of the lens. The new lens’s front optic incorporates an aspheric central blended zone that mimics the increase in negative spherical aberration that comes with natural accommodation, Dr Ossma said.

The design takes advantage of pupil constriction during near viewing to maximise near visual benefit, but maintain optical quality under mesopic conditions. The lens was implanted in 87 eyes of 45 patients in two sites by three surgeons. Mean age at the time of surgery was 62 +/- 8.62 years. At six months, monocular measurements were made including manifest refraction, intermediate (80cm) and near (40cm) visual acuity without and with distance refractive corrections, mesopic contrast sensitivity measurements without and with glare, and visual acuity were also measured binocularly. Out of 81 eyes available for analysis, 91.4 per cent were within 1.0 D of spherical refraction and 88.9 per cent were within 1.0 D of astigmatism. Intermediate visual acuity of 20/25 or better was achieved by 95.3 per cent of eyes uncorrected and 93.8 per cent with distance correction. Near visual acuity of 20/40 or better was achieved by 97.4 per cent eyes uncorrected and 92.1 per cent with distance correction. Binocularly, 90 per cent or more subjects achieved 20/25 intermediate and 20/40 near visual acuity. This represents an improvement of about 15 per cent for near vision over the previous Synchrony design. Mesopic contrast sensitivity with or without glare was not statistically different from patients implanted with the parent Synchrony lens. As for spectacle use, about 12 per cent reported using them at least occasionally for near vision, with three per cent always using them for near, while just three per cent reported using spectacles occasionally for distance, with none using them always or most of the time for distance.

“The next generation Synchrony IOL with enhanced optic shape offers very good visual outcomes without any compromise to retinal image quality,†Dr Ossma said. However, he still emphasised the need to appropriately manage patient expectations, particularly with regard to transient myopia and the possibility of need for a refractive enhancement.