NEW YORK (Reuters Health) - People who were diagnosed with type 1 diabetes in more-recent decades may be less likely to suffer vision loss than their predecessors.
In a study of nearly 1,000 Wisconsin residents with type 1 diabetes, researchers found that visual impairment was less common among those diagnosed in the 1970s compared with those diagnosed in earlier decades.
The findings, the researchers say, suggest that better blood sugar control and improved treatment of diabetes-related eye disorders are preventing more cases of visual impairment than in years past.
Type 1 diabetes is an autoimmune disease that kills off or disables the pancreatic cells that produce the hormone insulin, which controls blood sugar. It is usually diagnosed by young adulthood.
People with visual impairment have abnormal vision even with corrective lenses. In diabetes, impaired vision is largely the result of an eye disease called diabetic retinopathy -- a long-term complication caused by damage to the tiny blood vessels supplying the retina.
In the new study, Dr. Ronald Klein and colleagues at the University of Wisconsin-Madison looked at data on 955 people who had taken part in a larger study of long-term diabetes complications, which included vision exams sometime between 1980 and 2007. All had been diagnosed with type 1 diabetes before the age of 30.
The researchers found that, overall, patients diagnosed in the 1970s were less likely to develop vision loss than those diagnosed before 1960 -- even after accounting for age, high blood pressure and other factors that affect diabetes patients' risk of impaired vision.
Among people who had had diabetes for 30 to 34 years, 16 percent of those diagnosed before 1960 showed visual impairment at the time of their eye exam, versus 9 percent of those diagnosed between 1970 and 1974.
The patterns were similar for people who had had diabetes for fewer years. Among those who had had diabetes for 15 to 19 years, for example, 13 percent of patients diagnosed in the 1960s had impaired vision at the time of their exam.
That figure was 4 percent among those diagnosed in the late 1970s, according to a report of the study published in the journal Ophthalmology.
The study "implies that better glycemic (blood sugar) and blood pressure control has resulted in the reduction of the progression of diabetic retinopathy to its severe vision-threatening stages," Klein told Reuters Health in an email.
It also suggests, he added, that more-timely detection and treatment of retinopathy have made a difference.
Laser surgery can treat more-advanced stages of diabetic retinopathy, as well as macular edema -- a swelling of the retina commonly seen in people with advanced retinopathy. The treatment became available in the 1960s, but came into wider use after studies in the 1970s and 1980s proved its effectiveness.
Similarly, clinical trials in recent decades have pointed to the importance of tight blood sugar control in cutting the risk of advanced retinopathy.
"I think the implication is that the translation of findings from clinical trials over the past 20 years...into clinical care has resulted in reduction of vision loss," Klein said.
That also suggests, he added, that future generations of people diagnosed with type 1 diabetes will continue to benefit.
Experts recommend that people with diabetes have an eye exam at least once per year to detect diabetic retinopathy and other eye disorders early, so that progression can be prevented or delayed.
SOURCE: Ophthalmology, October 2009.