All About Cataracts

An innovative light-adjustable intraocular lens (IOL) may be the answer to correcting residual refractive errors after cataract surgery, based on the findings of a new study.

Researchers in California and Tijuana, Mexico, conducted a prospective study of 14 subjects who had unilateral cataract surgery with implantation of a proprietary light-adjustable IOL.

The light-adjustable lens (LAL), based on technology developed by researchers at the University of California, San Francisco and California Institute of Technology, is made of photosensitive silicone that enables the shape of the lens to be altered in a predictable manner when exposed to a special beam of light. This adjustment can take place days or weeks after cataract surgery when the eye has healed.

By adjusting the shape of the LAL after surgery, the cataract surgeon can reduce or eliminate residual refractive errors such as nearsightedness and farsightedness that may remain after the cataract procedure.

In the study, LALs were implanted during cataract surgery in a manner to intentionally produce up to -1.50 diopters (D) of residual myopia after the procedure. The lenses were then treated with light produced by a digital light delivery device to correct the residual myopia and lock-in the correction.

Analysis of the study data revealed:

• The day after adjusting the LAL and locking in the correction, 13 eyes (92.9 percent) were within 0.25 D of the target refraction.
• Up to 9 months after treatment, 14 eyes (100 percent) remained within 0.50 D of the target refraction.
• During the 9 month follow-up period, no eye had more than a 0.25 D change in refraction.

The researchers concluded that residual myopia up to -1.50 D can be successfully treated (resulting in significant improvement in uncorrected visual acuity) using the light-adjustable lens technology, thereby reducing the need for prescription eyeglasses after cataract surgery.

The full report of the study (“Correction of myopia after cataract surgery with a light-adjustable lens”) is published in the August 2009 issue of Ophthalmology.

Note: The LAL technology evaluated in this study is not yet FDA-approved for use in cataract surgery performed in the United States.

German company S&V Technologies has created custom-made intraocular lenses (IOLs) for animals with cataracts. The acrylic IOLs are implanted in the animals’ eyes during a procedure essentially the same as cataract surgery for humans.

Human cataract surgery is the most frequently performed surgery in the United States, and more than 90 percent of patients achieve good vision. For animals, cataracts usually mean blindness, according to Indgeborg Fromberg, head of the company’s veterinary division. Treating cataracts can improve the quality of life for animals, which have relatively short life spans, Fromberg says.

The company’s lenses have generated interest from around the world, including Sea World in San Diego for a sea lion that performs tricks, an Australian nature park for a blind kangaroo and a Romanian zoo for a visually impaired lioness. Additionally, the World Wildlife Fund has paid for cataract surgery with the lens implants for brown bears in a China nature reserve.

The company’s IOLs have also been used to restore vision for racehorses, circus animals, guide dogs and domestic pets.

Although the surgery is pricey, Fromberg says that many people consider their pets to be part of their family and are willing to pay the cost to restore the vision of their beloved furry friends.

Cataract surgery does not cause a progression of early age-related macular degeneration (AMD) to a more sight-threatening stage of the disease, according to a new study.

Researchers in Australia performed cataract surgery on 27 eyes of 27 patients with early macular degeneration to see if removal of their cataracts would improve the patients’ vision and quality of life without increasing their risk of AMD progression and vision loss from choroidal neovascularization (CNV).

CNV is the growth of fragile new blood vessels in the choroid layer of the eye underlying the retina. In macular degeneration, these blood vessels can leak into the retina, causing “wet” macular degeneration and severe vision loss.

Prior to the phacoemulsification cataract surgery performed in the study, all patients underwent a test called fundus fluorescein angiography (FFA) to make sure no eyes had pre-existing CNV.

Data gathered 6 months after surgery revealed a 2.8-line mean improvement in visual acuity (measured with a standard eye chart) and a 2.1-fold average gain in quality of life scores (measured by a patient survey) after cataract removal. One eye (3.7 percent) developed CNV within 6 months of surgery.

The researchers concluded that there was no significant increase in short-term risk of progression from dry AMD to CNV following uncomplicated phacoemulsification cataract surgery, and that there are distinct benefits of cataract surgery in people with early macular degeneration.

Source: Cataract surgery in high-risk age-related macular degeneration: A randomized controlled trial. Clinical & Experimental Ophthalmology. Published online June 22, 2009.

German researchers have found that visual performance — specifically reading speed — with multifocal intraocular lenses after cataract surgery improves with time, suggesting the brain adapts to multifocal IOLs as time goes by.

“When analyzing multifocal lens performance, it is important to follow patients over time and to remember that there is a brain behind the eyes,” said Manfred R. Tetz, MD, of the University of Berlin at the 2009 annual meeting of the American Society of Cataract and Refractive Surgery held recently in San Francisco.

Dr. Tetz and colleagues evaluated the visual performance of 25 patients who had one of two brands of multifocal IOLs (Tecnis Multifocal IOL, Abbott Medical Optics; AcrySof ReSTOR, Alcon Laboratories) implanted bilaterally after cataract removal. All patients were examined for a period of six to 18 months after surgery.

Both multifocal IOLs provided good uncorrected visual acuity (UCVA) at all distances. Mean UCVA at intermediate (arm’s length) was approximately 20/40 for both groups. 

When evaluating reading speed as a measure of visual performance, the researchers found that the patients were capable of significantly faster reading speeds than patients who received bilateral multifocal IOL implants and were followed for only three months.

“This indicates there is a neural adaptation by the patient over time,” said Dr. Tetz.

Although reading speed for both groups slowed with smaller font sizes, patients in the AcrySof ReSTOR multifocal IOL group could read small fonts faster than those in the Tecnis Multifocal IOL group.

Source:  Faster reading speeds over time indicates brain adapts to multifocal IOLs. Ophthalmology Times. Meeting E-News, April 4, 2009.