ASCRS 1999 maps new refractive frontiers

Speakers previewed a world where phacorefractive surgery, phakic IOLs and accommodating IOLs are standard practice and presbyopia has been conquered.

---Harold Ridley, MD, FRCS, FRS, (second from left) is honored at a special session commemorating the 50th anniversary of his invention of the intraocular lens. With him on the podium are (left to right) incoming ASCRS president Robert Sinskey, MD, outgoing president Spencer Thornton, MD, (partially visible), ASCRS program committee chairman Manus Kraff, MD, D. Peter Choyoe, FRCS, Eric Arnott, FRCS, and David Apple, MD.

SEATTLE — It was apropos that the 25th anniversary meeting of the American Society of Cataract and Refractive Surgery (ASCRS) — which included a tribute to Harold Ridley, MD, FRCS, FRS, on the 50th anniversary of his invention of the intraocular lens — was highlighted by presentations on a new generation of lens implants and refractive corneal and lens surgery.

Phacorefractive surgery

Although surgeons have been reluctant to remove a clear lens for strictly refractive purposes, the advantages for high myopes and contact lens intolerant patients warrant the procedure, said Dennis L. Williams, MD, of Tarpon Springs, U.S.A.

“We have to appreciate all the problems that a 22 D myope has,” Dr. Williams said. Several reasons have deterred surgeons from performing lens extraction for refractive correction, including fear of retinal detachment, a lack of supply of high powered IOLs, problems with lens power calculations, and the likelihood of iatrogenic astigmatism inducement.

However, today’s cataract surgical techniques have reduced complication rates, lens power calculations are very accurate, and high-power IOLs are readily available, Dr. Williams said.

Most patients in whom Robert J. Mitchell, MD, of Calgary, Canada, performed refractive lens extraction were presbyopic. He found that monovision gave patients satisfactory vision and that fine adjustments of the refractive correction can be performed postoperatively.

Reducing PCO

David J. Apple, MD, of the Medical University of South Carolina, presented a report on his database of 15,000 explanted IOLs and autopsy globes.

Dr. Apple said enhanced hydrodissection and cortical clean-up, in-the-bag IOL fixation, a small capsulorrhexis overlapping the IOL optic, biocompatible IOL material, adhesion between the posterior IOL surface and the posterior capsule and the use of IOLs with square-edged optics are the six essential ingredients in the prevention of posterior capsule opacification (PCO). He reported that rates of PCO are decreasing in the United States. Within a few years he expects the U.S. incidence of PCO to fall below 10%.

The prevention of PCO also was the subject of a presentation by Jochen Kammen, MD, of Dortmund, Germany. Dr. Kammen unveiled a bipolar cautery spatula he uses to remove lens epithelial debris from the capsular bag following phacoemulsification. The system sends an electric current of about 1.5 W through a spatula tip that eradicates debris as the instrument is swept across the capsule. Dr. Kammen reported that capsules rarely are damaged with the new procedure, but he said that a highly viscous viscoelastic is recommended and that the procedure is contraindicated in small pupil cases.

Presbyopia correction

Accommodation can be restored after the onset of presbyopia, according to several surgeons who spoke here. Spencer Thornton, MD, Hideharu Fukasaku, MD, and Robert H. Marmer, MD, presented two surgical methods to alleviate presbyopia.

Dr. Thornton, of Nashville, U.S.A., presented his results with the anterior ciliary sclerotomy (ACS) technique to overcome presbyopia.

In this technique, the conjunctiva is incised in four quadrants and paired radial incisions are made in the sclera, starting at the limbus and extended outward. Each incision is 3 mm long and 600 µm deep. The incisions are manually spread apart and checked for depth. The conjunctiva is closed over the incisions to prevent infection.

Dr. Fukasaku, of Yokohama, Japan, presented results of a 12-patient study of ACS. Pre- and postoperative accommodative amplitude were measured, and anterior movement of the lens was verified postoperatively by ultrasound biomicroscopy.

Patients increased their accommodative ability by an average of 1.9 D postoperatively, which enabled them to perform most daily tasks.

Dr. Fukasaku also discussed his method of ACS, in which three incisions are created in each quadrant to provide even more accommodation.

Dr. Marmer, of Atlanta, presented another technique based on an alternative theory of the cause of presbyopia. This theory postulates that the lens continues to grow throughout life, crowding the ciliary muscles and preventing them from providing accommodation.

Dr. Marmer presented the results of a technique in which four PMMA segments are inserted into partial thickness scleral pockets placed in the four quadrants of the globe, each about 2.5 mm away from the limbus. This allows the sclera to expand outward and thus re-establishes zonular tension.

LTK results promising

Douglas Koch, MD, of Houston, medical director of Sunrise Technologies, presented results of the phase 3 study of the Sunrise LTK system to treat hyperopia.

He presented data on 345 eyes followed for 6 months. Patients all were age 40 years or older, with a range of hyperopia of 0.75 D to 2.5 D.

The Sunrise laser creates two concentric circles of eight laser spots at 6 mm and 7 mm optical zones.

Uncorrected postoperative visual acuity was 20/40 or better in 85% of eyes and 20/25 or better in 58%. In the study, 65% of patients fell within 0.5 D of their target refraction and 89% fell within 1 D of their target refraction.

In the study, two cases had induced cylinder more than 2 D.

Accommodating IOL?

In a presentation on what might prove to be the first truly accommodating IOL, Stephen Slade, MD, of Houston reported early clinical experience with the AT45 (Medevec, Amsterdam) in Mexico. The AT45 is the latest design modification of the IOL designed by J. Stuart Cumming, MD.

The AT45 is designed with a hinged optic-haptic junction designed to flex in response to the ciliary muscle’s restored ability to contract after crystalline lens extraction. The IOL obtains its add power as it shifts forward with the vitreous face under ciliary muscle contraction.

Studies of the AT45 found that 1 mm of forward motion provides about 2 D of accommodation. Safety evaluations of the lens found that it was not associated with any increase in intraocular pressure, corneal edema or decentration. Most patients who received the lens achieved 20/40 or better best-corrected visual acuity and none lost any best-corrected acuity.

Endophthalmitis survey

In the Opening General Session, Samuel Masket, MD, discussed the status of the ASCRS Endophthalmitis Survey. The survey was conducted in 1996 and 1997, Dr. Masket said, but was not repeated last year.

Rather than conduct another survey, he said, it was “time to look at what we’ve learned” from the two already completed surveys.

Dr. Masket said the 1997 survey showed that when vancomycin was used prophylactically at cataract surgery, there was a “highly statistically significant” reduction in the rate of infection, from 0.0007 to 0.0003 (P=.0001).

He said controlled studies are needed to verify the conclusions of the survey, and the value of future surveys, at least on this topic, is questionable.

Phakic IOLs

David Brown, MD, a cataract specialist in St. Paul, U.S.A., presented phase 1 and 2 FDA study results of the STAAR Surgical ICL for myopia. In what he described as “remarkable” visual results, 41% of 102 patients achieved 20/20 or better and 80% were 20/40 or better best-corrected acuity.

Most patients were within 0.5 D of emmetropia, and 87% of eyes were within one line of their preoperative level. Dr. Brown reported no visual loss as a result of ICL implantation. Once phase 3 of the FDA study is fully enrolled, 278 patients will have received the ICL in clinical trials.

ASCRS practice profile study

David Leaming, MD, of Palm Springs, U.S.A., presented his annual practice profile report on ASCRS members. About 5,000 surveys were mailed; 30% of members responded. Dr. Leaming said that laser in situ keratomileusis is by far the most common refractive procedure in the United States. Volume in 1998 was up 168% over 1997, an increase that by all accounts was expected.

Microkeratome face-off

In a symposium dubbed the “Microkeratome Face-Off,” R. Doyle Stulting, MD, of Atlanta, presented results of a study of microkeratome cuts performed on tissue specimens, which were analyzed at the electron microscopy lab at Emory University. All microkeratome manufacturers were invited to participate in the face-off, but only four sent in tissue samples: Bausch & Lomb, Innovative Optics, Solan and Mastel.

The specimens were evaluated for smoothness of the microkeratome cut. Mastel was rated the smoothest, with a score of one. Bausch & Lomb and Innovative Optics both received a score of two. Solan received a 2.33 rating. Dr. Stulting posited that the smoothness of the Mastel cut could be attributed to the unit’s diamond blade.

The bad news for refractive surgeons, Dr. Stulting said, is that the Mastel microkeratome is not yet on the market. A prototype was used to create the specimen submitted for the face-off.

Dr. Stulting noted that the clinical significance of the face-off’s results have not been determined.

Sovereign phacoemulsifier

The Allergan Sovereign phaco unit seems to merge the advanced high vacuum fluidics of the AMO Prestige unit with the burst and occlusion mode programmability of the AMO Diplomax, according to presenter David F. Chang, MD. The Sovereign was used to perform phaco using both the Nagahara chopping method and the Pfeifer quick chop method on hard nuclei. The results were compared with the AMO Diplomax.

“Solid purchase of the nuclear segments with the phaco tip helps to anchor the nucleus during chopping and it helps to elevate the chopped pieces out of the tight confines of the capsular bags,” Dr. Chang said.

Solid purchase of nuclear segments was achieved through burst mode, high vacuum and rapid vacuum rise time obtainable through occlusion mode programmability. Dr. Chang said that burst mode is very useful for dense nuclei. Burst mode impales the nucleus with single burst strokes that maintain occlusion of the tip.

High vacuum settings of 350 mm Hg to 400 mm Hg increased holding power and maintained good chamber stability. The occlusion mode, originally introduced in the Diplomax, allows the flow rate to change automatically during tip occlusion. Phaco modes can be changed between burst, continuous and pulse, giving the surgeon increased flexibility.

Intralenticular hubbing phaco

Removing the center and “hubbing” a vertically rotated nucleus is a new way of emulsifying a hard cataract. According to the presenter, Keiki R. Mehta, MD, this is a simple technique that works on medium, hard and super hard cataracts with exceptional safety and reproducibility.

After capsulorrhexis, the nucleus is hydrodissected until it rotates freely. The nucleus is then viscodissected and rotated vertically until it stands on edge. Utilizing phaco from one side and support from the side-port instrument, the center of the nucleus is cored or “hubbed” out. Peripheral nucleus is removed by inserting the phaco tip obliquely with the nucleus held vertically and spun around the tip. When only a thin cortical rim remains, it is then split and aspirated.

The procedure was performed on 600 consecutive medium and hard cataracts. Endothelial cell loss was about 3.8% in medium and about 4.3% in hard cases.