Surgeons: Keep abreast of advancing technology, research

Technology is evolving rapidly, but experts agree unanswered questions leave holes in knowledge.

For cataract surgeons seeking fast, efficient and safe methods to remove cataracts, along with optimum IOL designs and materials, there is no substitute for cutting-edge information.

The field is changing so rapidly, physicians must keep vigilant watch for the latest surgical developments. For this reason, some of the field’s top surgeons pooled their expertise at a special symposium, titled “Unsolved problems in cataract surgery.”

Participants covered various topics, including macular edema, aberrations in the pseudophakic eye, choosing the right IOL and acute postoperative endophthalmitis.

Managing macular edema

Jose Cunha-Vaz, MD, PhD, of Coimbra, Portugal, said much remains to be learned about the long-term consequences on visual acuity of postoperative macular edema.

One goal for surgeons should be to better identify patients at risk of developing this complication to prevent macular alterations, he said. He also said surgeons must pay more attention to previously diseased macula and devote more attention to postop follow-up.

Macular edema after cataract surgery is common, he added. While the short-term effects on visual acuity are minimal, the long-term consequences are unknown, he said.

There are two types of macular edema: vasogenic and cytotoxic. The vasogenic variety can be further divided into focal, diffuse and tractional, while the cytotoxic variety can be classified as direct cell damage or ischemic, Dr. Cunha-Vaz explained.

He cited data pertaining to 32 patients who had uneventful cataract surgery by small incision, phacoemulsification and IOL implants. These patients were examined 3, 6, 12 and 30 weeks after surgery for indications of retinal leakage and leakage.

The study employed a retinal leakage analyzer (RLA) to measure leakage across the blood-retinal barrier (BRB). This device produces a reading of fluorescein penetration into the vitreous across the BRB based on a confocal scanning laser ophthalmoscope.

To measure the increase in retinal thickness, Dr. Cunha-Vaz and colleagues used optical coherence tomography, which relies on the same principles as an ultrasound, combined with the imaging capabilities of a microscope.

The study sought to determine the precise percentage of increase of leakage and thickness in these cataract patients over the normal reference population.

The RLA established that patients experienced a roughly 81% increase in fluorescein leakage at 3 weeks after surgery. This proportion rose to 88% after 6 weeks, stayed at 88% at 12 weeks and dropped to 69% after 30 weeks.

In terms of an increase in retinal thickness, the study revealed that patients experience a roughly 28% increase in retinal thickness by 3 weeks after surgery. This increase rose slightly to 35% at 6 weeks, but dropped back to 28% at 12 weeks and remained stable at 30 weeks.

Visual acuity was almost perfect in 84% of the patients at 3 weeks after surgery, with that proportion rising to 96% at 30 weeks, Dr. Cunha-Vaz said.

Noting that the long-term significance of these findings is still unknown, he encouraged his colleagues to consider the problem of macular edema more carefully, to identify the population at risk and to pay closer attention to surgical procedure and follow-up to avoid complications.

Reducing postop aberrations

Turning to the question of reducing optical aberrations in the pseudophakic eye, one presenter suggested that new IOL materials and designs could play a central role in correcting various problems.

Roberto Bellucci, MD, of the University Hospital in Verona, Italy, said current IOL designs do not fight the optical aberrations of the cornea experienced by aphakic patients.

Designed to provide the eye with optimal spherocylindrical refraction, most conventional lenses lack the design features to reduce higher-order aberrations, most of which originate from the anterior corneal surface, he said.

On the whole, existing IOLs induce aberrations when loop compression modifies the optic, which occurs in IOLs with stiff loops and weak optics, he said. These aberrations are not currently correctable with spherocylindrical spectacle lenses and can be a serious problem for patients with large pupils, he added.

“These patients have decreased contrast sensitivity and reduced functional vision,” Dr. Bellucci said.

Optical aberrations in the pseudo-phakic eye can be corrected, and some solutions to the problem are already in development, he noted. Research is moving toward customized IOLs and new IOL materials that could allow for modification of the lens after implantation.

This could help eyes with previous refractive corneal surgery that need customized IOLs, as well as eyes with “normal” corneas, Dr. Bellucci said.

Currently available IOLs have a positive spherical aberration, so pseudophakic eyes also have increased positive spherical aberrations that reduce contrast sensitivity. A new lens developed by Pharmacia seeks to address this problem by introducing a negative spherical aberration, Dr. Bellucci said. The theoretical possibilities for this lens and other versions on the horizon are promising, he noted.

Balance for IOL choice

Before selecting an IOL for a cataract patient, surgeons must consider which lens – out of more than 1,300 available – balance specific properties most effectively, according to another surgeon.

Olivia Sedarevic, MD, of New York City, stressed the importance of balancing such essential properties as handling, insertion, anatomic stability, refractive stability and optical quality in relation to each patient’s functional visual requirements.

“We often really don’t understand what we are choosing and why we are choosing it,” she said.

Because technology is changing so rapidly – along with the concepts of ideal IOL characteristics – surgeons must choose existing IOLs based on an overall evaluation of how compatible they are with patients’ needs.

Dr. Serdarevic stressed that, whenever possible, an injector should provide for easy insertion via an unenlarged phaco incision to prevent corneal damage as well as endophthalmitis and induced astigmatism. An important feature of an IOL is its delivery system, she added.

The short- and long-term visual results, however, should not be compromised for ease of insertion, she said.

Another major concern regarding IOL choice is prevention of posterior capsular opacification with a sharp capsular bend. To date, hydrophobic acrylic and silicone IOLs that permit appropriate angulation, maximal posterior capsular contact and fibrosis of the anterior capsule with adhesion to the posterior capsule have the best track record for preventing PCO, she said.

Dr. Serdarevic explained that optical quality is another important consideration. Phenomena related to edge design, such as increased glare, have been well documented, although they typically affect many more younger patients with larger pupils.

She said design features such as rounding of the anterior optic edges that slope toward the sharp posterior edges help reduce internal reflections and prevent postop glare.

Even as technology continues to advance at a rapid pace, technology already exists that effectively balances many essential characteristics, Dr. Serdarevic said.

Multicenter study

Peter James Barry, MD, of the Royal Victoria Eye & Ear Hospital in Dublin, considers it amazing that there is still no clear understanding of the incidence of postop endophthalmitis. To the end of better assessing and reducing the incidence of this condition, clinical sites throughout Europe will participate in a prospective study expected to involve 40,000 patients from throughout Europe, according to Dr. Barry, a lead investigator of this study.

Centers in Austria, Belgium, England, France, Germany, Portugal and Spain will enroll patients and randomize them to one of four equal-sized groups undergoing cataract surgery.

All patients will be treated with povidone iodine preoperatively, and will receive levofloxacin 0.5% postop on days 1 through 6. Intraoperatively, patients will be randomized to receive either intracameral cefuroxime or not, and also to receive topical placebo saline drops or topical levofloxacin drops. The patient groups will consist of 10,000 participants each.

Levofloxacin was chosen because it is an intensive topical solution that has been shown to be nontoxic in 30 million doses in Japan, Dr. Barry said.

Surgeons will conduct 3-to-6 week follow-up examinations. All patients suspected to have developed endophthalmitis will be further evaluated to identify the culture-proven cases and the presumed, clinically observed cases, he said.

All results will be garnered and submitted to a central data bank, and will be constantly analyzed as they come in, Dr. Barry said.

For Your Information:

• Jose Cunha-Vaz, MD, PhD, can be reached at the Centro de Oftalmologia, Azinhaga de Santa Comba, Celas, 3000-354 Coimbra, Portugal; +(351) 239-480-220; fax: +(351) 239-480-280.
• Roberto Bellucci, MD, can be reached at Via Degli Abeti 17, 25087 Salo (BS), Italy; +(39) 347-657-5001; fax: +(39) 036-543-678.
• Olivia Serdarevic, MD, can be reached at 1036 Park Ave., New York, NY 10028 U.S.A.; +(1) 212-794-8691; fax: +(1) 212-734-2307.
• Peter James Barry, MD, can be reached at Eye Clinic, 33 Herbert Ave., Merrion Dublin 4, Ireland; +(353) 1-28-37-203.