Friday, October 22, 2010

ESCRS symposium on emerging lenticular options at AAO/ISRS refractive subspecialty day

Light-adjustable lenses that may be used to achieve emmetropia in post-LASIK cataract patients or increase binocular depth of field through selective manipulation of asphericity in mini-monovision were among the growing list of lenticular refractive options presented at the ESCRS symposium at the 2010 AAO annual meeting refractive subspecialty day sponsored by the International Society of Refractive surgery.

As in laser vision correction, a slight negative asphericity in the eye targeted for near in mini-monovision also has been shown to increase depth of field in pseudophakic patients, noted Jose Guell MD, Barcelona, Spain. “It can be a very useful tool for presbypoia improvement,” he said.

However, there are important limitations in applying it for IOLs, Dr Guell said. The tolerance for spherical aberration is limited to about 0.2 microns and achieving this level of precision can be difficult. For one, the degree of asphericity is related to the degree of residual astigmatism, so an accurate spherocylindrical correction is essential. The effects of lens decentration, tilt or rotation also affects asphericity and other higher order aberrations, and small lens movements could increase aberrations beyond the tolerable range.

Light-adjustable lens may be one way to address these issues, Dr Guell suggested. The power and asphericity of the lens can be adjusted after surgery. Laser corneal enhancements are another option and may be possible in conjunction with light-adjustable lenses, he added.

In a study presented by Roberto Bellucci MD, Verona, Italy, 20 eyes implanted with light-adjustable lenses were found to have higher levels of spherical aberration, resulting in their aberration-derived Strehl rations being similar to those seen in spherical monofocal lenses. He believes the increased asphericity, which averaged 0.118 +/- 0.044 microns for the eye, was most likely due to the reshaping of the lens with ultraviolet pulses after surgery. This resulted in a myopic shift of about 0.9 dioptre with an increase in pupil size from 4 mm to 6 mm.

However, and somewhat unexpectedly, the light-adjustable lenses did not result in higher levels of coma or other asymmetrical aberrations, Dr Bellucci noted. “From a clinical point of view all our patients were satisfied and reported good uncorrected vision. It can be postulated that the increased depth of focus involved with the high spherical aberration played an important role in this satisfaction.”

A study of 26 eyes implanted with the Crystalens HD accommodative IOL by Ioannis Pallikaris MD PHD, Crete, Greece, (pictured above with the other ESCRS presenters) found that the lenses produced a good range of vision even when implanted in the sulcus. Mean uncorrected distance vision improved from 0.41 +/- 0.21 to 0.70 +/- 0.19 on a decimal scale, and corrected vision improved from 0.66 to 0.87. At intermediate distances 80 per cent of patients achieved J1 and at near 70 per cent were J3 or better. The three patients with sulcus-implanted lenses also demonstrated accommodation, Prof Pallikaris said.

Joaquim Neto Murta MD, Coimba, Portugal, presented results on a new rotationally nonsymmetrical multifocal lens without Fresnel lines. The pupil independent lens has an aspheric asymmetrical distance zone combined with a sector near zone with a +3.0 add to minimize light loss and light sensations. The lenses provided adequate vision, were stable and provided good contrast sensitivity, he said.

Also presenting were Oliver Findl MD, Vienna, Austria, on add-on lenses to correct residual sphere and cylinder error and Beatrice Cochener MD, Brest, France on refinements in toric implantation. She emphasised the importance of meticulous technique, including removing all viscoelastic from the chamber, to help minimize lens rotation after surgery.