Managing diabetic retinopathy in primary care

Medical Tribune January 2009 P14-15

Diabetic retinopathy is a leading cause of visual loss in Asia and one of the major chronic eye diseases handled by GPs. Left untreated, it can result in permanent blindness from neovascular glaucoma or tractional retinal detachment arising from proliferative diabetic retinopathy.

The condition is expected to become more common as the prevalence of diabetes continues to rise in Asia.

A recent study found that 38.1 percent of diabetics who were referred for retinal assessment as part of a nationwide screening program in Singapore had retinopathy. [Ann Acad Med Singapore 2008 Sep;37(9):753-9] The Singapore Malay Eye Study, meanwhile, demonstrated a retinopathy prevalence of 35 percent among diabetics of Malay ethnicity, of whom 9 percent had vision-threatening retinopathy. [Ophthalmology 2008 Nov:115(11):1869-1875]. This high rate of diabetics suffering from retinopathy is consistent worldwide. The proportion of type 2 diabetics having retinopathy has been reported to be 40.3 percent in the US, 35 percent in Taiwan and 10.5 – 26.2 percent in India.

Pathogenesis

Diabetic retinopathy is a highly specific microvascular complication of both type 1 and type 2 diabetes mellitus, resulting from progressive damage to the retinal blood vessels caused by hyperglycemia in the blood. The condition is caused by increased vascular permeability at onset, leading to fluid accumulation in the retina. With time, there is vascular shutdown, causing ischemia of the retina. This leads to retinal neovascularization at the disc or elsewhere, vitreous hemorrhages, fibro-proliferative changes and retinal detachment. Neovascular glaucoma can also develop. The prevalence is strongly related to the duration of diabetes mellitus, and most diabetic patients will develop retinopathy with time.

See the sidebar for a classification of the different disease stages.

Screening

As patients with sight-threatening retinopathy may not show any symptoms, fundal screening of diabetic patients is crucial in helping to identify those at risk of developing complications that will impact on their vision and quality of life. The importance of regular screening for diabetics, therefore, cannot be understated.

All diabetic patients should be screened for retinopathy on an annual basis at the very least, beginning from the point of diagnosis. Those who are at high risk for developing retinopathy need to be monitored more closely and should be screened at least twice yearly. The major risk factors to consider are hypertension, high cholesterol, smoking, patient’s age, duration of diabetes and a history of poor glycemic control. The Singapore Malay Eye Study also found that a history of stroke, cardiovascular disease or chronic kidney disease was associated with vision-threatening retinopathy.

Female diabetics who are planning to conceive should be screened prior to conception and again in the first trimester. The regularity of follow-up should then be determined based on the results of the first trimester examination.

For patients with established retinopathy, the timing of follow up examinations depends on their disease status.

Physicians who are involved in providing diabetic care have a pivotal role in ensuring that patients are screened. This can be performed via fundal photography, indirect fundoscopy or direct ophthalmoscopy through a dilated pupil.

While the need for regular screening is well accepted by the medical community, it is an unfortunate reality that patients are often not screened as frequently as they should be. Many patients do not understand the progressive nature of the disease process, mistakenly believing that if there is nothing wrong with their vision, then they do not need to see an eye doctor. Many appointments are missed as a result, and the early signs of diabetic retinopathy can often go undetected. Accessibility can also be a problem, particularly in rural areas, and can also contribute to the missing of screening appointments.

We must educate patients on the importance of these check-ups, and help them to understand that by the time they discover they have developed visual problems, it may already be too late to treat them. GPs can also help patients to attend their screening appointments by checking regularly whether they are compliant with their schedules, reminding them about upcoming
visits and making sure that they are referred to the most appropriate and convenient center.

Practice guidelines

The most widely-used guidelines on diabetic retinopathy come from the American Academy of
Ophthalmology. These have been incorporated into clinical practice guidelines on the management of diabetic retinopathy from Singapore’s Ministry of Health, published in January 2004, which help GPs plan their management and screening schedules for their patients. Diabetic retinopathy guidelines are also available from the Academy of Medicine of Malaysia.

Treatment

Laser treatment is the major therapy for diabetic retinopathy but can lead to long-term side effects such as a reduced field of vision.

There is now a considerable weight of data showing the benefits of good glycemic control on
retinopathy outcomes. The Diabetes Control and Complications Trial (DCCT) found that an intensive strategy reduced the risk of developing retinopathy by 76 percent and slowed disease progression by 54 percent. [N Engl J Med 1993 Sep 30;329(14):977-86] Recent data from the United Kingdom Prospective Diabetes Study (UKPDS) show that the benefits of intensive glucose control extended long beyond the trial intervention, with a 24 percent risk reduction for microvascular disease noted 10 years after the conclusion of the study. [N Engl J Med 2008 Oct 9;359(15):1577-89]

Tight blood pressure control is also important. The original UKPDS data demonstrated a 47 percent reduction in the risk of having decreased vision in both eyes, after 9 years of follow up. [BMJ 1998 Sep 12;317(7160):703-13] The 2008 data showed that the benefits disappeared once treatment was withdrawn, suggesting that blood pressure control needs to be maintained in order to continue to derive the maximum benefits. [N Engl J Med 2008 Oct 9;359(15):1565-76]

Medication adherence is often a major obstacle in achieving these targets. GPs should continue to ensure that patients are well-educated on the importance of taking their drugs, making them aware that failure to do so increases their risk of retinopathy. Regular HbA1c and blood pressure tests should be carried out to monitor progress, and medication adjusted accordingly.

Disease management tools

In October 2006, the Ministry of Health in Singapore launched the Chronic Disease Management Program, focusing initially on diabetes and then on hypertension, dyslipidemia
and stroke. The plan is to transform management of these diseases by forming an effective
partnership among GPs, medical specialists and patients through effective information flow within the partnership throughout the healthcare continuum. The program aims to equip GPs with a better understanding of patients’ medical histories through up-to-date electronic records and, in turn, reduce medical costs and enable the provision of quality healthcare services customized to individual requirements.

This integrated clinic management system provides GPs with a complete system to manage their patients and clinic operations. Critical clinical indicators are stored, enabling GPs to use this data to track the progress of their patients. Clinical decision support tools are also built into the system to help GPs plan effectively and communicate care plans to their patients. In this way, schedules for retinopathy screening can be built into the patients’ management plan, helping doctors keep to the intended schedules.

Conclusion

Regular screening is the cornerstone of detecting, monitoring and managing diabetic retinopathy and should be arranged from the very point of diagnosis. Patients should be educated about the importance of screening and followed up at all stages to ensure compliance to their schedules. Good glycemic and blood pressure control are also of vital importance in preventing the development and progression of this potentially sight-threatening condition. It is strongly recommended that the organization of retinopathy screening be primarily the responsibility of the GPs, who will then refer all patients with retinopathy or media opacity to an ophthalmologist for more specialized treatment.

Online Resources:

The American Academy of Ophthalmology guidelines:

www.guideline.gov/summary/summary.aspx?doc_id=4350