Are cataract rates on the decline?

Feb 28 2008

Should glaucoma patients seeking alternative therapies trust what they find online? Are seatbelts still important to protect eyes in auto accidents, now that most cars have airbags? What's the connection between hearing loss and one form of glaucoma? These are among the topics explored in the March 2008 issue of Ophthalmology, the journal of the American Academy of Ophthalmology.

The population-based Beaver Dam Eye Study was designed by Barbara E. K. Klein, MD, MPH, and colleagues to determine through long-term observation whether there were differences among age cohorts regarding rates of cataract prevalence and surgery, as well as type of cataract. Five-thousand residents of Beaver Dam, Wisconsin, were examined for the three most common forms of cataract—nuclear, cortical and posterior sub-capsular---at baseline in 1990 and five, 10 and 15 years later. Results were analyzed by age group and gender for this population, which was 99 percent white. The rates of all three cataracts increased with age for all cohorts and are described in the study in detail by age cohort and gender.

An interesting decline in prevalence of nuclear cataract---the type characterized by hardening of the center of the eye's lens---was found when participants were considered in five-year age and birth cohorts (excluding the 75+ group, which had too few participants). Even after adjusting for expected higher prevalence at older ages, the study found that prevalence declined in each successive birth cohort. The authors suggested that this decline may be related to negative health habits shared by people in the older cohorts and to more positive health habits in the younger cohorts. The researchers write: “Possible protective exposures include a decrease in smoking and increase in exposure to healthy lifestyle habits.” Rates of cataract surgery also increased in the 15-year time period, as surgical techniques and outcomes improved significantly and more people elected cataract surgery at earlier points in the disease process.

Glaucoma Patients Seek Complementary and Alternative Therapies Online
About 117 million people in the United States use the internet to access conventional and complementary/alternative medical (CAM) information. Among glaucoma patients an estimated 5.4 percent use CAM therapies, and many rely on the internet to learn about and purchase services and products. A research team led by Dr. Daniel George Ezra assessed 21 high-traffic CAM-for-glaucoma web sites to determine the most prevalently recommended therapies, the factual basis of the information presented, and potential commercial bias. Only one site was approved by the Health on the Net Foundation, the United Nations-accredited guide to reliable online medical information, but the study judged 11 sites “excellent” based on a standardized rating system. Thirteen sites were found to have expressed opinions without factual substantiation, and two sites were rated “high risk” to patients because they discouraged using conventional medicine. Fourteen sites offered products and/or services for purchase.

The most frequently recommended CAM therapies were: vitamin C; the herbs forskolin and ginkgo biloba; and nutrients alpha-lipoic acid, rutin/flavinoids, and vitamin E. The authors concluded: “Medical information conveyed over the internet is of variable quality…Many sources contain advice on therapies that have no evidence base and may put patients at risk.” They encouraged ophthalmologists to become aware of CAM-for-glaucoma internet content so they can help patients make informed choices.

Seatbelts Reduce Eye Injury Risk in Auto Accidents
Although airbags in automobiles have helped reduce overall injuries and fatalities by 32 percent since they were introduced in the 1970s, airbag deployment sometimes causes eye injuries, with an estimated incidence of 5 percent. A 2007 study led by Sunil K. Rao, MD, evaluated how seatbelt use correlated with eye injuries and the recovery of visual acuity in auto accidents where airbags deployed. The study concluded that “the use of seatbelts was associated with less severe ocular injuries and better visual outcomes.” Reviewing medical records of the Rhode Island Hospitals general eye clinic January 1997 to August 2005, researchers selected 47 patients who were either the driver or front-seat passenger in an auto accident with airbag deployment, excluding accidents with rollover or ejection. Patients had been questioned by clinic staff regarding seatbelt use, eyewear use, and airbag status.

Injuries were ranked as mild, moderate, or severe using a standardized scale: 49 percent of the patients had severe injuries, 23 percent moderate, 26 percent mild, and 2 percent were not injured. Seventy-one percent of those not restrained by seatbelts had severe injuries versus 31 percent wearing seatbelts. Forty-two percent of restrained patients had only minor injuries. Visual acuity outcomes also depended on seatbelt status, with unrestrained patients significantly more likely than restrained to have 20/200 or worse vision at the three month post-accident follow-up. None of the patients was wearing eyeglasses, and none had previously had cornea transplant or refractive surgery; these variables could influence results in future studies. The patients' age, gender, accident type and alcohol status were not significantly related to injury severity.

An Eye Disease or Systemic Disorder? Hearing Loss Study Adds to the Evidence Shahin Yazdani, MD, and his research team evaluated whether patients with ocular pseudoexfoliation syndrome---the most common cause worldwide of the form of glaucoma known as “secondary open angle”---had a higher incidence of hearing loss. In ocular pseudoexfoliation (also called “exfoliation”) syndrome, fibrous white deposits aggregate on the iris, lens and other parts of the eye and can block fluid drainage; this blockage increases intraocular pressure, which can damage the optic nerve. Similar fibrillar deposits have been found in the heart, blood vessels, lung, liver, kidneys and skin of patients with ocular pseudoexfoliation. In addition, pseudoexfoliation has been associated with ischemic heart disease. systemic hypertension, aneurysms, Alzheimer's disease, and age-related macular degeneration (AMD). The researchers hypothesized that the hearing organs might also be affected after noticing hearing disability in many pseudoexfoliation patients.

The case-control study enrolled 83 patients with ocular pseudoexfoliation and 83 controls matched for age and gender. Hearing loss was significantly more prevalent in patients with pseudoexfoliation than controls ----94 percent versus 69.9 percent. Below-average hearing thresholds were also significantly more common in ears of cases versus controls, 88.4 percent and 53.6 percent respectively. As in past studies, no definitive correlation was found between glaucoma and hearing loss. The authors conclude: “The findings of the present study imply that this apparently ocular disorder may truly be a manifestation of a systemic condition that affects multiple organs throughout the body.”

Ophthalmologists are urged to consider the possibility of hearing loss in patients with ocular pseudoexfoliation syndrome and guide them to additional medical care as needed.

Eds: Full texts of the studies are available from the Academy's media relations department.

About the American Academy of Ophthalmology
The American Academy of Ophthalmology is the world's largest association of eye physicians and surgeons—Eye M.D.s—with more than 27,000 members worldwide. Eye health care is provided by the three “O's” – opticians, optometrists and ophthalmologists. It is the ophthalmologist, or Eye M.D., who can treat it all: eye diseases and injuries, and perform eye surgery. To find an Eye M.D. in your area, visit the Academy's Web site at http://www.aao.org.