All About Cataracts

Carnosine, a dietary supplement available without a prescription, may be able to prevent or treat cataracts, according to a study published in the July 14 issue of the American Chemical Society journal Biochemistry.

If true, taking daily supplements of carnosine may reduce the risk of developing cataracts, decreasing the need for cataract surgery.

Carnosine is a small molecule composed of two amino acids. It is found in relatively high concentrations in several body tissues, including muscles, nerves and the brain. The exact role of carnosine in the body is not fully understood but it appears to have an antioxidant effect.

The researchers exposed tissue cultures of lenses taken from healthy rat eyes to either guanidine — a substance known to form cataracts — or a combination of guanidine and carnosine. The lens tissue exposed to guanidine became completely cloudy, while the lens tissue exposed to guanidine and carnosine developed 50 to 60 percent less cloudiness. Carnosine also restored clarity to clouded lens tissue.

Cataracts occur when the primary structural protein in the eye’s lens, alpha-crystallin, forms abnormal clumps. These clumps make the lens cloudy and impair vision. Carnosine appears to play a role in blocking the formation of these clumps and/or reversing them.

Though further research is needed, the findings of the study prompted the researchers to suggest that carnosine could potentially prevent and treat cataracts in humans.

Source: Protective effects of l- and d-carnosine on a-crystallin amyloid fbril formation: Implications for cataract disease. Biochemistry. Published online July 14, 2009.

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.

A popular medicine taken by men for benign prostatic hyperplasia, commonly known as BPH or an enlarged prostate gland, is associated with increased risk for serious complications after cataract surgery, according to a study published in the May 20, 2009 issue of the Journal of the American Medical Association (JAMA). 

Flomax (tamsulosin HCl, Boehringer Ingelheim Pharmaceuticals) is a popular prescription medication to treat male urinary symptoms due to BPH. Symptoms include the need to urinate often, waking up several times during the night to go, a weak urinary stream and frequently feeling an urgent need to urinate.

BPH is common among older men: It is estimated that more than 50 percent of men over age 60 and almost all men over age 80 have symptoms of an enlarged prostate. The condition can also affect men in their 40s and 50s.

Tamsulosin HCl, the active ingredient in Flomax, belongs to a category of drugs called alpha blockers. Alpha blockers relax certain muscles and help small blood vessels remain open. In addition to treating BPH, alpha blockers are used to treat high blood pressure.

Researchers in Canada recently conducted a retrospective study of over 96,000 men age 66 years or older who had cataract surgery between 2002 and 2007. Of these patients, 3,550 (3.7 percent) had taken tamsulosin within two weeks of their cataract procedure and 7,426 (7.7 percent) others had taken other alpha blockers within two weeks of surgery.

Adverse events following cataract surgery were significantly more common among patients with recent tamsulosin exposure (7.5 percent) than among controls (2.7 percent) matched for age, surgeon and date of cataract surgery. There was no significant increase in the risk of adverse events following cataract surgery from recent use of other alpha blockers for treatment of BPH or high blood pressure.

Serious cataract surgery complications associated with recent Flomax use include retinal detachment, dislocation of the intraocular lens and endophthalmitis (inflammation of the interior of the eye, usually caused by infection).

Take Home Message: If you are currently taking Flomax for BPH symptoms, be sure to discuss this with your cataract surgeon prior to surgery. He or she may recommend you temporarily discontinue BPH treatment or switch to a different alpha blocker for a period of time before and after your cataract procedure to reduce your risk of medication-related surgical complications.

Source:  Association between tamsulosin and serious ophthalmic adverse events in older men following cataract surgery. JAMA. May 20, 2009.

Cataracts are the leading cause of blindness globally, and three programs in the developing world seek to help people blinded by cataracts to regain their sight.

At the recent annual meeting of the American Society of Cataract and Refractive Surgery (ASCRS), eye surgeon David F. Chang, MD, described how the Aravind Eye Hospital system in southern India, the Tilganga Eye Center in Kathmandu, Nepal and Project Vision in China are seeking to restore the vision of poor and aging populations in remote and under-served areas of the world.

Acccording to Dr. Chang, a clinical professor of ophthalmology at the University of California, San Francisco, based on the World Health Organization (WHO) definition of blindness as best-corrected visual acuity (BCVA) of 20/400 or worse, more than 18 million people worldwide are blind in both eyes due to cataracts.

That number grows to 54 million when considering how many people have BCVA worse than 20/200 (frequently called “legal blindness”) and balloons to 144 million if you include people with BCVA of 20/60 or worse due to cataracts. This final category describes people with low vision, who typically cannot see well enough to obtain an unrestricted driver’s license in the United States.  

 But while cataracts affect virtually all aging populations, there are many obstacles to the surgical treatment of cataracts in developing countries. These obstacles include the expense of surgical equipment and intraocular lenses (IOLs), a shortage of ophthalmologists in these regions and a lack of training programs for cataract surgeons and surgical staff in the developing world.

Dr. Chang described three programs that are providing safe, fast and low-cost cataract surgery for the poor in under-served regions of the world:

• The Aravind Eye Hospital System in southern India has been providing charitable eye care and cataract surgery on a large scale for more than 30 years. It was founded by Govindappa Venkataswamy, MD. Patients in remote villages are screened for cataracts on a Sunday, are transported by bus to a regional Aravind eye center that same evening and have cataract surgery the following day. On a typical Monday, 300 to 400 cataract surgeries are performed. “To maximize efficiency, every step of the preparation and procedure is standardized, and doctors and staff perform their roles with military precision,” said Dr. Chang. The Aravind hospital system controls costs by manufacturing its own supplies, including IOLs. Outcome studies have demonstrated that this high-volume surgical approach is safe and effective, and of the approximately 200,000 cataract surgeries performed each year at Aravind’s five regional hospitals, 70 percent are performed at no cost to the patient.

• The Tilganga Eye Centre in Kathmandu, Nepal was founded by Sanduk Ruit, MD. Along with Geoffrey Tabin, MD, Dr. Ruit also founded the Himalayan Cataract Project (HCP) in 1995. The goal of the program is to eradicate cataract blindness in Nepal by establishing outreach eye clinics in rural villages outside Kathmandu. The HCP uses portable generators and surgical equipment and transforms places such as open-air classrooms into temporary operating rooms. IOLs for the procedures are manufactured at Tilganga Eye Centre, which also sells the IOLs to 60 countries in the developing world. The center is also opening a new wing to train cataract surgeons from other countries.

• Project Vision in China was founded by Dennis Lam, MD, chairman of ophthalmology at Chinese University of Hong Kong. The project is a collaboration between the university, private philanthropy in Hong Kong, a training center in China and the Chinese government, according to Dr. Chang. Seventy percent of China’s population, or 900 million people, live in rural villages with limited access to medical care. In addition, most of the Chinese population cannot afford cataract surgery. Project Vision provides surgical equipment and training to nine county-level hospitals throughout rural China. In exchange, the hospitals agree to lower their charges for cataract surgery to $90 (USD) per case.

Concluding his ASCRS presentation, Dr. Chang noted that these three model programs prove that “there is hope” of overcoming the formidable challenge of cataract blindness in the developing world.

Source: Three programs offer hope. Ophthalmology Times. May 1, 2009