All About Cataracts

Certain age-related cataracts may be due to problems with a specific gene, according to researchers at Case Western Reserve University School of Medicine (Cleveland, Ohio).

A gene called EPHA2 appears to be involved in maintaining the health and normal structure of proteins in the lens of the human eye. When this gene is absent or damaged, lens proteins begin to clump together and form lens opacities, or cataracts, say investigators Bing-Cheng Wang, PhD, and Sudha K. Iyengar, PhD.

Drs. Wang and Iyengar are collaborating in research with several other investigators in laboratories across the U.S. and in Australia and the U.K.

So far, the researchers have identified several mutations of the human EPHA2 gene that appear to be associated with age-related cataracts, and they continue to look for more.

By better understanding the processes by which the EphA2 gene helps maintain clarity of the human lens, they researchers may be able to find ways to prevent cataracts and possibly reverse them, perhaps reducing the need for cataract surgery.

The researchers also say other studies suggest common genes and pathways may be involved in both age-related cataracts and neurodegenerative diseases (e.g. Alzheimer’s disease) that affect the elderly.

Their report, “EPHA2 is associated with age-related cortical cataract in mice and humans,” appears in the July 2009 issue of PLoS Genetics.

People with diabetes who undergo cataract surgery have twice the risk of progression of their diabetic retinopathy, according to a new study.

Researchers at the University of Sydney (New South Wales, Australia) and the University of Melbourne (Victoria, Australia) followed 190 diabetic patients age 65 and older who underwent phacoemulsification cataract surgery between 2004 and 2006. Of the 190 patients, 169 were followed for at least 12 months after surgery.

During the 12-month follow-up period, diabetic retinopathy (DR) developed in 28.2 percent of eyes that underwent cataract surgery with intraocular lens (IOL) implantation and did not have DR prior to surgery. During the same 12-month period, diabetic retinopathy developed in 13.8 percent of eyes that did not undergo cataract surgery and did not have DR at the beginning of the study period.

In a paired-eye comparison of 45 patients with pre-existing diabetic retinopathy who had cataract surgery in one eye but not the other and were at risk of DR progression, 35.6 percent of the post-surgical eyes exhibited progression of diabetic retinopathy, compared with 20 percent of the fellow eyes that did not undergo surgery.

The researchers concluded that people with diabetes who undergo modern phacoemulsification cataract surgery appear to have twice the risk of developing diabetic retinopathy or experiencing a progression of their DR  12 months after surgery.

This added risk, however, is lower that the risk of diabetes-related cataract surgery complications that has been previously documented in diabetic patients who have undergone less advanced cataract surgery (“intracapsular” and “extracapsular” cataract surgery without phacoemulsification).

Source: Development and progression of diabetic retinopathy 12 months after phacoemulsification cataract surgery. Ophthalmology. August 2009.

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.