LASIK, PRK and other corneal refractive surgery have been shown to increase higher-order aberrations in the eye that can affect visual clarity. Even customized, wavefront-guided LASIK typically increases these aberrations to some extent.

Researchers in France, however, have found that within 3 months after LASIK surgery, the human eye appears to be able to compensate to some degree for aberrations in the cornea caused by LASIK, thereby reducing the total aberrations of the eye.

The investigators studied 57 eyes of 57 patients who underwent conventional LASIK surgery for the correction of myopia. All eyes were measured before and 3 months after surgery to compare corneal aberrations and total eye aberrations, using an OPD-Scan aberrometer (NIDEK Co Ltd.)

Measurements taken 3 months after LASIK surgery revealed that although total corneal higher-order aberrations (HOA) increased by a factor of 2.47 after LASIK, total eye HOA increased by a factor of 1.77.

For a specific type of HOA called spherical aberration, corneal spherical aberration (SA) increased by a factor of 2.64 after LASIK, while total eye SA increased by a factor of 1.46.

The lower magnitude of total eye aberrations compared with corneal aberrations after LASIK suggest some degree of compensation by the internal optics of the eye to reduce the affect of the corneal aberrations, according to the study authors.

The researchers concluded that the human eye appears to have an adaptive ability that enables it to partially compensate for corneal aberrations caused by LASIK performed for the correction of myopia.

A full report of the study appears in the May 2010 issue of Journal of Refractive Surgery.

Researchers in San Diego compared changes in simulated night driving performance among patients moderate to high myopia and astigmatism after treatment with either surgical implantation of a toric Visian Implantable Collamer Lens (STAAR Surgical; Monrovia, Calif.) or conventional PRK surgery.

A total of 43 eyes (20 bilateral cases) were treated with the Visian Toric Implantable Collamer Lens (TICL), and 45 eyes were treated with PRK surgery.

Prior to surgery, subjects participating in the study had -6.00 to -20.00 diopters (D) of myopia and 1.00 to 4.00 D of astigmatism.

Before and 6 months following treatment, 27 eyes of 14 TICL patients and 41 eyes of 21 PRK patients underwent a simulated night driving test.  The test required the subjects to detect and identify common road signs and hazards with and without the presence of a glare source.

Examples of a glare source during real-world night driving are the headlights of approaching vehicles.

The results of the night driving simulator testing revealed:

• Without the introduction of a glare source, patients in the TICL group could identify road signs and pedestrian hazards significantly faster than patients in the PRK group.
• With introduction of a glare source, patients in the TICL group could identify pedestrian hazards (but not road signs) significantly faster than patients in the PRK group.
• There was no significant difference in how quickly subjects in the two treatment groups could detect (but not identify) road signs and pedestrian hazards, with and without a glare source.

The researchers concluded that the Visian Toric Implantable Collamer Lens performed better than conventional PRK surgery in the pre- to post-surgical simulated night driving visual performance testing, with and without a glare source present.

A full report of the study appears in the May 2010 issue of Journal of Refractive Surgery.

That’s the finding of researchers in France and Spain who conducted a study of 304 patients with an average age of 65.6 years who underwent bilateral implantation of the multifocal lens. The surgery was performed to treat cataracts or to reduce the need for eyeglasses via refractive lens exchange.

The researchers had three goals:

1. To determine how many patients would be glasses-free 18 months after surgery.
2. To determine the degree of satisfaction patients had with the multifocal IOL.
3. To identify psychological factors most likely to predict independence from glasses after surgery.

At 18 months after surgery, the researchers found:

• Uncorrected distance visual acuity was 20/25 or better for 88.6 percent of patients.
• Uncorrected near visual acuity was 20/25 or better for 93.3 percent of patients.
• 87.2 percent of patients reported being glasses-free throughout the day.
• 88.2 percent of patients said their vision had improved and 78.0 percent considered their sight problems to be resolved.

In addition, the researchers found that patients who said that wearing glasses was bothersome and also said they preferred their appearance without glasses were three times more likely not to wear glasses after the ReSTOR surgery.

The researchers concluded that bilateral implantation of ReSTOR multifocal IOLs provides patients with good vision at distance and near without glasses, a high rate of spectacle independence and a high degree of satisfaction with their vision after surgery.

A full report of the study appears Clinical Ophthalmology (Vol 4), published online February 2010.

Ed. note:  ReSTOR is one of several brands of multifocal IOLs approved by the U.S. FDA for use in cataract surgery performed in the United States. Discuss your vision correction options with your refractive surgeon during your pre-surgical consultation.

It was believed that the light-absorbing nature of these lens implants might offer advantages over clear lens implants, including providing sharper vision, better contrast sensitivity and reduced risk of macular degeneration.

But recent research has shown that blue-blocking IOLs fail to provide measureable visual or eye-protective benefits for people under going cataract surgery, according to two reports in this month’s issue of Survey of Ophthalmology. In fact, blue-blocking IOLs may perform worse than clear IOLs in some measures of visual performance.

In the first report, researchers at the University of Kansas School of Medicine say blue-blocking IOLs fail to decrease glare or improve contrast sensitivity, and the reduced light transmittance of the blue-blocking lens implants appears to reduce visual performance in dim and dark environments.

The researchers also say that most scientific evidence shows that environmental light exposure and cataract surgery are not significant risk factors for the progression of age-related macular degeneration (AMD), and that blue-blocking IOLs are unlikely to prevent or reduce one’s risk of AMD.

In the second report, researchers at Ophthalmic Consultants of Boston and Harvard Medical School reviewed the results of 56 peer-reviewed studies of blue-blocking IOLs. Eleven of these studies directly compared the visual outcomes of blue-blocking IOLs and conventional (non-blue-blocking) lens implants.

Of the 11 studies that directly compared the two types of IOLs, 10 of the studies (91 percent) concluded that blue-blocking IOLs offered no significant benefits over conventional IOLs in measures of visual performance that included visual acuity, contrast sensitivity, color perception and visual sensitivity in bright, medium and low-light conditions.

The researchers said one study suggested blue-blocking IOLs might produce worse vision than clear IOLs in low-light conditions and could possibly affect circadian rhythms and thereby cause sleep disturbances in susceptible individuals.

Also, regarding the possible protective effect of shielding the retina from blue light, the researchers said the benefits of blocking the transmittance of blue light to the retina and the relationship between light transmittance and the progression of AMD “remain unclear.”

Ed. note:  Blue-blocking IOLs are one of many types of premium refractive IOLs used in cataract surgery and refractive lens exchange. Ask your refractive surgeon to discuss your IOL options during your pre-surgical consultation.

SOURCES:
1. Blue-blocking IOLs decrease photoreception without providing significant photoprotection. Survey of Ophthalmology. May 2010.
2. Blue-blocking IOLs: A complete review of the literature. Survey of Ophthalmology. May 2010.

The researchers evaluated the effectiveness of stimulation of the brain’s visual cortex to improve vision after removal of cataracts, using a commercially available computer-based vision training program (RevitalVision, LLC; Lawrence, Kan.).

A total of 60 subjects who had undergone cataract surgery that included implantation of one of five styles of intraocular lenses participated in the vision training sessions. The mean age of the subjects was 68 years.

Uncorrected visual acuity and contrast sensitivity at both distance and near were tested at 1 month and 3 months after surgery. In the intervening weeks, subjects underwent 20 sessions of vision training using the computer-based RevitalVision Cortex Vision Training (CVT) program.

After CVT, mean improvement in uncorrected visual acuity for all subjects was 1.3 lines on a standard eye chart for distance vision and 1.0 line for near vision. Mean improvement in contrast sensitivity function was 223 percent for distance vision and 197 percent for near vision.

Subjects demonstrated gains in uncorrected visual acuity regardless of the type of intraocular lens (IOL) they received after removal of their cataracts: aspheric monofocal IOLs, accommodating IOLs or multifocal IOLs.

The research was conducted under the direction of George O. Waring IV, MD, (Emory University School of Medicine; Atlanta Ga.), John D. Hunkeler, MD, (University of Kansas Medical Center; Prairie Village, Kan.) and Richard L. Lindstrom, MD, (University of Minnesota; Minneapolis, Minn.)

About ARVO: The Association for Research in Vision and Ophthalmology is the world’s largest eye and vision research organization with more than 12, 500 members from more than 80 countries. Membership is ARVO is multidisciplinary and includes ophthalmologists, PhDs, optometrists and other vision researchers.

Researchers in Canada evaluated the bilateral implantation of AcrySof toric refractive IOLs (Alcon; Fort Worth, Texas) in subjects undergoing cataract surgery in both eyes. The study included 234 eyes of 117 subjects.

Prior to surgery, all subjects had cataracts and astigmatism ranging from 1.0 to 2.5 diopters (D).

At 1 day and 1, 3 and 6 months after surgery, the following measurements were taken: uncorrected visual acuity (UCVA) at distance, residual refractive error, and IOL rotational stability.

In addition, all patients completed a questionnaire administered before surgery and at 3 months and 6 months after surgery. Using a 10-point scale, the questionnaire assessed dependence on eyeglasses, visual disturbances and satisfaction with vision (1 = completely unsatisfied; 10 = completely satisfied).

Post-operative findings included:

• Binocular distance UCVA was 20/40 or better in 99 percent of patients and 20/20 or better in 63 percent of patients.
• Mean residual refractive astigmatism was reduced to 0.4 D.
• IOL alignment was within 10 degrees of the intended position in 99 percent of patients and within 5 degrees in 99 percent of patients.
• 69 percent of patients reported never needing glasses for driving and other distance vision tasks.
• Halos and glare present prior to surgery were significantly reduced after surgery.
• 94 percent of patients rated their vision a 7 or higher after surgery.

The researchers concluded that cataract surgery with bilateral implantation of toric IOLs to correct astigmatism produced “excellent and stable visual outcomes that patients rated as highly satisfactory.”

A full report of the study appears in the April 2010 issue of Journal of Cataract and Refractive Surgery.

In the April 2010 issue of EyeWorld, a panel of eye surgeons discussed the importance of the ambient humidity and temperature in the laser surgery suite and eye hydration before, during and after surgery to achieving predictable, high-quality visual results.

Among the opinions expressed:

Daniel S. Durrie, MD, (Overland Park, Kan.), Emil W. Chynn, MD, (New York, N.Y.) and Joseph Rosenshein, PhD, (Victor, N.Y.) said controlling the temperature and humidity levels in the refractive surgery operating room (OR) are important factors in ensuring consistent outcomes.

Richard L. Lindstrom, MD, (Minneapolis, Minn.) said that in addition to controlling temperature and humidity, the air in the OR should be cleaned with high efficiency particulate-absorbing filters.

Controlling the humidity in the operating room is important, but may be somewhat overstated, said Steven C. Schallhorn, MD, (San Diego, Calif.). Dr. Schallhorn noted that in a large LASIK study he recently completed, he found that the level of humidity in the laser room “did not correlate with the refractive outcome.”

Dr. Chynn, however, said a 2003 study published in the Journal of Cataract & Refractive Surgery found a zero percent LASIK enhancement rate in winter and a 50 percent enhancement rate in late summer, and that the study showed a tendency toward LASIK under-correction when humidity was high.

The surgeons agreed that more significant factors in LASIK outcomes than controlling temperature and humidity in the OR (which most LASIK surgeons do) are the patient’s behavior and environment after surgery.

For the best laser eye surgery outcomes possible, Dr. Chynn recommends that patients drink plenty of water, avoid or reduce consuming alcohol and caffeine, use a humidifier in their home and use all eye drops as directed to keep their corneas well-hydrated during the healing process.

Ambient humidity after surgery is more important for patients that undergo PRK and LASEK than it is for LASIK patients, Dr. Chynn said, because the corneal epithelium must grow back over the treated area of the eye in the former procedures, and this is easier if the corneal surface is kept moist.

The surgeons also agreed that treating a pre-existing dry eye condition prior to LASIK and other laser vision correction surgery is essential in order to achieve predictable results.

Monovision is the practice of fully correcting one eye so it sees perfectly well for distance vision, and making the other (usually non-dominant) eye mildly nearsighted so it provides acceptable near vision without reading glasses.

Monovision has been around for years, being performed with contact lenses to enable people over age 45 who have presbyopia to have functional vision at all distances without being dependent on reading glasses.

Recently, monovision also is being offered by refractive surgeons with LASIK and with refractive IOLs used in cataract surgery.

This week, eye surgeon John A. Hovanesian, MD, (Laguna Hills, Calif.) discussed monovision cataract surgery in his blog on the Ocular Surgery News website.

According to Dr. Hovanesian, the monovision procedure has several advantages over the use of multifocal IOLs in cataract surgery, Including:

• A “trial run” of monovision with contact lenses prior to cataract surgery rarely is needed.
• High-quality vision at all distances can be achieved with only a mild amount of nearsightedness in the non-dominant eye, making adaptation to monovision quite easy.
• Monovision typically does not cause depth perception problems.
• Monovision can yield better contrast sensitivity than monofocal IOLs for activities like driving at night.
• Monovision allows cataract surgeons to choose from a variety of premium monofocal IOLs, including aspheric lenses designed to reduce glare.
• Monovision typically is less expensive than cataract surgery with multifocal IOLs, which can require thousands of dollars in out-of-pocket costs for patients.

For the best results with monovision, it’s important that the distance vision of the dominant eye is perfect. In some cases, this means enhancement refractive procedures (i.e. LASIK or PRK) may be required after cataract surgery.

Dr. Hovanesian said that after considering its advantages, he plans to offer surgical monovision to more of his cataract patients in the future.

Also, many refractive surgeons prefer not to perform LASIK on older patients who have or may soon have cataracts that would make the benefits of LASIK short-lived.

For these patients, many eye surgeons are turning to an elective vision correction procedure called refractive lens exchange, or RLE. In this procedure, the lens inside the eye is removed and replaced with a man-made intraocular lens (IOL) — like in cataract surgery.

In the March 2010 issue of EyeWorld, two experienced refractive surgeons discussed the advantages of RLE and the techniques they prefer when performing the procedure.

Stanley Berke, MD, associate clinical professor of ophthalmology and visual sciences at Albert Einstein College of Medicine (New York, N.Y.) says RLE is a good choice for patients who desire vision correction surgery but are poor candidates for LASIK because their corneas are too thin, they have too much nearsightedness or farsightedness or because of other risk factors.

Jason Stahl, MD, assistant clinical professor of ophthalmology at Kansas University Medical Center (Kansas City, Kan.) says that normal age-related lens changes in the eyes of people in their late 40s and 50s can cause light scatter that degrades vision, even before a cataract forms in the lens.

Replacing the aging lens with an IOL via the refractive lens exchange procedure can improve vision in these patients, he says.

Dr. Stahl says RLE offers older patients who desire vision correction surgery a number of advantages:

1. When using an accommodating IOL or a multifocal IOL, RLE can restore both distance and near vision in a person who has presbyopia.
2. RLE can eliminate the need for cataract surgery in the future.
3. RLE stabilizes the optics of the eye, reducing the risk of changes in a person’s eyeglass prescription and visual acuity because of increasing refractive errors.

Both surgeons emphasized that patient education about the RLE procedure, including risks and potential outcomes, are essential so patients have realistic expectations about what the surgery can and cannot do for them.

They also said a thorough pre-operative exam is necessary to rule out eye problems other than normal age-related lens changes that could affect visual outcomes, and post-operative care is needed to avoid unwanted complications.

In some cases, a follow-up refractive procedure such as LASIK or PRK may be needed to fine-tune the refractive result for optimal uncorrected visual acuity.

SOURCE:  Considering refractive lens exchange. EyeWorld. March 2010.

Crystalens currently is the only accommodating IOL approved by the FDA for use in cataract surgery performed in the United States. The lens is designed to restore vision at all distances after cataract removal, including near vision lost to age-related presbyopia.

Joining the celebration will be Broadway, film and television actress Florence Henderson. Best known for her role as Carol Brady in the iconic television series “The Brady Bunch,” Ms. Henderson will be at the Bausch & Lomb booth at the ASCRS meeting on Sunday, April 11 at 1 p.m. to discuss her experience as a Crystalens patient.

“I’m very pleased to have experienced such a dramatic improvement in my vision since my Crystalens surgery,” she said in a press release issued today by Bausch & Lomb.

During the Crystalens 10-year anniversary celebration, Bausch & Lomb also will honor 12 cataract surgeons who have implanted more than 1,000 Crystalens accommodating IOLs.