Surgery for cataracts can help older drivers see the road more clearly, and may get some former drivers behind the wheel again, new research shows.

The Swedish study found that after cataract surgery, fewer drivers had vision problems during both daytime and nighttime driving. Furthermore, one-third of those who had given up driving were able to get back on the road a few months after surgery.

A cataract is a clouding of the eye’s lens that commonly arises as people age.

When symptoms, such as blurred vision and trouble seeing at night, begin to interfere with daily life, surgery may be necessary. The procedure involves removing the clouded lens and replacing it with an artificial one.

Studies have shown that cataract surgery can improve driving vision in the short term, and the new findings suggest those benefits can last for several years, said Dr. Eva Monestam, the study’s lead author.

In many cases, cataracts are age-related. They first appear in the 40s or 50s, but may not affect vision until after age 60. In other cases, cataracts may be caused by eye trauma, long-term diabetes, corticosteroid medications or radiation treatments. In infants, cataracts can be present since birth (congenital) or can occur as a result of an infection that happened during pregnancy, especially toxoplasmosis, cytomegalovirus, syphilis, rubella or herpes simplex. In infants and young children, cataracts also can be one symptom of a disease that affects how the body processes carbohydrates, amino acids, calcium or copper.

Cataracts are the world’s leading cause of blindness, accounting for about 42 percent of all cases of blindness. In the United States, most cataracts are age-related, and affect more than half of all Americans older than 65 to some degree. Although the exact cause of age-related cataracts is unknown, some scientists suspect chemical changes affecting eye proteins called a-crystallins. Current research suggests that a-crystallins prevent the abnormal clumping of other types of proteins into cataracts. What causes cataracts is the subject of active research. Prolonged exposure to bright sunlight and smoking have been identified as factors.

Monestam and her colleagues at Umea University in Sweden report the results in the British Journal of Ophthalmology.

The study included 810 men and women who underwent cataract surgery during a single year at one university clinic. They were about 75 years old, on average.

Before surgery, 55 percent of patients with a driver’s license were active drivers, although 16 percent of them did not meet Sweden’s minimum visual acuity requirement for driving. Of all patients with licenses, one-third failed to meet this requirement. After surgery, however, that figure fell to 5 percent.

In addition, among 183 licensed drivers who did not drive before surgery, 37 percent resumed driving in the months afterward. Most were still driving 5 years later.

In line with those findings, patients reported fewer roadway vision problems post-surgery. While half had difficulty seeing during daytime driving before surgery, only 5 percent reported such problems 5 years after surgery.

When it came to driving at night, 79 percent had trouble seeing before having surgery. A few months afterward, that number dropped to 34 percent - though at the 5-year mark, it was up to 44 percent.

The reason for the increase in nighttime vision problems is not clear, Monestam said, and she and her colleagues are currently studying the question.

Despite the upswing in night vision difficulties, she said, “It is nice to see that the majority of drivers have good vision.”

Whether the clearer vision necessarily translates into fewer accidents, however, is unclear. According to Monestam, studies have not looked at whether cataract surgery is associated with lower crash rates.

SOURCE: British Journal of Ophthalmology, April 2005.