Diabetic retinopathy on the rise in Pakistan

London-A population-based assessment of diabetic retinopathy among Pakistani adults found visual impairment (<6/12 in the better eye) in nearly half of the diabetic population and signs of diabetic retinopathy in one in six. With large increases in the prevalence of diabetes expected in coming years, data from this and other studies could be used to establish or improve screening and treatment programs to prevent diabetic retinopathy from becoming a significant cause of vision loss, said Shaheen P. Shah, MBBS, MRCOphth, MSc.

Dr. Shah reported these findings on behalf of the Pakistan National Eye Survey Study Group. The study was an international collaboration between the International Centre for Eye Health, London, and the Pakistan Institute of Community Ophthalmology, Kyber Medical Institute, Peshawar, Pakistan.

Because this was a national survey, it is possible to extrapolate the data to the country as a whole.

“We estimate that there are at least 90,000 to 100,000 adults in Pakistan who have sight-threatening diabetic retinopathy that requires immediate eye care, which is limited in the country at the moment,” said Dr. Shah, clinical lecturer, International Centre for Eye Health, London School of Hygiene and Tropical Medicine.

“By exploring risk factors and identifying high-prevalence areas, services can be targeted to maximize the cost-effectiveness of diabetic retinopathy programs,” Dr. Shah continued.

Pakistan is the sixth largest country in the world in terms of population, with 150 million people and a growth rate of 2.9%. Little definitive information on the prevalence and causes of blindness and visual impairment was available before the national survey was initiated in 2001, however, he said.

“Reliable estimates are needed so that services can be planned in a rational manner,” Dr. Shah said.

As a background to the survey and its findings, he noted that Pakistan and other developing countries have experienced a significant increase in diabetes, most likely due to rapid changes in lifestyle and diet. At least one-third of Pakistan’s population lives in urban areas, nearly double the rate of 50 years ago, and 25% of adults are overweight or obese.

Health-care resources in Pakistan and other developing countries appear to be inadequate, to meet the growing challenges they face, however. Many patients with diabetes are not receiving treatment, and the effectiveness of care among those who do receive it is unclear.

“Diabetes is increasing in many countries, and they face challenges in terms of prevention of diabetes and in the prevention and management of complications of diabetes,” Dr. Shah said. “Most of the morbidity that will be suffered by the diabetic population will be in developing countries due to their limited resources for health care.

“Pakistan, with its huge growth rate and large population, is a prime example of a country that will suffer from the effects of diabetes and diabetic retinopathy,” Dr. Shah said.

Methodology

The national survey was performed between 2001 and 2004 with the goal of estimating the prevalence and causes of blindness and visual impairment in adults aged 30 years or more. The number examined was 16,507-95% of those originally enumerated. Survey methodology used a stratified random cluster sampling technique to obtain a nationally representative sample. The survey included 221 clusters and covered most of the country, except for a few areas that were too dangerous to enter because of political instability.

Two groups of diabetics were identified during data analysis. Group 1 included patients with self-reported histories of diabetes obtained during survey interviews. Group 2 consisted of previously unknown patients with diabetes whose conditions were detected during the survey process; this group was then split into two categories-those whose disease was randomly detected due to elevated random blood glucose and those in whom disease was clinically detected.

In further analysis, diabetic retinopathy was classified into three non-mutually exclusive groups: nonproliferative, maculopathy, and proliferative. Grading was performed following pupil dilation and slit lamp-based indirect ophthalmoscopy by trained ophthalmologists.

Results

Approximately one in seven adults aged 40 years or more had diabetes. The proportion of undetected diabetes was 60%, which was higher than expected, according to Dr. Shah.

Prevalence data also indicated that diabetes is a disease of affluence, he continued. Rates were higher in urban than rural areas, among the literate rather than the illiterate, and among the affluent than either the poor or those with moderate incomes.

“With increasing urbanization, increasing literacy, and increasing affluence in the population, diabetes will be an increasing problem, which is unusual because in industrialized countries, diabetes is more commonly associated with deprivation rather than affluence,” Dr. Shah explained.

The rate of visual impairment in all diabetic patients was 43.8%, and one in 20 was blind (<20/400 better eye). Blindness was more prevalent in the known diabetic patients than in those who were randomly detected.

Risk factors for undetected diabetes included living in a rural or poor area, Dr. Shah said.

One in six diabetic patients had signs of retinopathy, this rate again being higher in the known group compared with the randomly detected group. Nonproliferative retinopathy was the most common type of retinopathy (40%), followed by any maculopathy (32%), and proliferative retinopathy (28%).

Investigators also compared the rates of diabetic retinopathy in diabetics in the survey with results from other population-based studies. They found that the prevalence was very similar in Pakistan and India.

Compared with those of industrialized countries such as Australia, Spain, Taiwan, the United Kingdom, and the United States, however, rates in Pakistan were much lower. This difference may be attributable to a higher mortality among diabetic patients with retinopathy in Pakistan, a cohort effect (i.e., the epidemic of diabetes began more recently, and diabetic patients have not had the condition long enough for retinopathy to develop), or simply a lower detection rate, due to a high rate of unoperated cataract precluding a view of the fundus.

Unoperated bilateral cataract was, overall, the main cause of blindness in the survey, Dr. Shah said. As the burden of blinding cataract increases in Pakistan through better detection and treatment, the rate of detection of retinopathy is likely to increase.

Limitations of this survey were that random blood sugar was not measured on the entire sample, and not all participants had a dilated fundal exam, according to Dr. Shah.

In addition, no information was available on the type and duration of diabetes. Grading of diabetic retinopathy was conducted by ophthalmologists in the field. Inter-observer agreement studies conducted in the pilot study were satisfactory, but validation by grading of fundus images has not been performed.OT