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Post-hoc analysis identifies risk factors for DME after PRP
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Post-hoc analysis of Diabetic Retinopathy Clinical Research Network Protocol S study data found specific risk factors for worse visual outcomes and development of diabetic macular edema (DME) in the group of patients treated with panretinal photocoagulation.
The same risk factors were not significant when ranibizumab intravitreal injection was used for treatment. No other risk factor was identified, and overall visual outcomes were better.
Protocol S included 305 participants with proliferative diabetic retinopathy (PDR) enrolled at 55 clinical sites and randomized to receive either prompt panretinal photocoagulation (PRP) or ranibizumab injection.
Mean visual acuity improvement at 2 years was 4.7 letters in the ranibizumab group, while the PRP group had a decrease of -0.3 letters.
Eyes with more severe retinopathy or higher hemoglobin A1c level at baseline showed less improvement in visual acuity and a greater incidence of severe center-involved diabetic macular edema (DME) over 2 years in the PRP group. Higher mean arterial pressure and cystoid abnormalities within 500 µm of the center of the macula were additional risk factors for developing DME. A secondary analysis of eyes without DME at baseline confirmed hemoglobin level and more severe retinopathy as risk factors.
No factors were associated with worse visual outcomes in the ranibizumab group, although subgroup analysis of patients without DME at baseline showed a possible association with prior DME treatment.
“Because PRP or anti-VEGF as monotherapies can be effective treatments for proliferative diabetic retinopathy, clinicians will continue to consider both in the care of patients,” the authors wrote. They said to be aware, however, that their findings might change some of the common views regarding prognosis after deciding which treatment to administer.
“When PRP is the primary treatment method for PDR, eyes of persons with poor glycemic control or more severe diabetic retinopathy may be more apt to lose visual acuity and develop vision-impairing, central-involved DME than eyes of persons with lower HbA1c level or less severe diabetic retinopathy” they wrote. – by Michela Cimberle
Disclosure: Bressler receives financial support from Bayer HealthCare Pharmaceuticals, Boehringer Ingelheim Pharm, Notal Vision, Novartis, Genentech, Merck & Co. and Spark Therapeutics. Please see the study for the other authors’ financial disclosures.
Perspective
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Carlo J. Pelino, OD
The prevalence of pre-diabetes and diabetes in the U.S. is increasing and, therefore, the prevalence of diabetic retinopathy (DR) and vision-threatening DR is also expected to increase. DR is already the leading cause of visual impairment worldwide.
During our examinations we stress to patients that they should maintain near-normal glucose, cholesterol and blood pressure levels. We educate them to stop smoking, lose weight and to get checked for sleep apnea when warranted because it lowers the risk of retinopathy developing and/or progressing.
Because DR occurs over time, the longer someone has had diabetes or the poorer they control their risk factors, the higher the risk of developing proliferative DR with or without macular edema. Good control of all risk factors also extends life by reducing the risk of cardiovascular disease.
DME is an additional complication that we assess separately from the stages of retinopathy. It can be found at any DR severity level and has been known to run an independent course. Currently, diabetic eyes are classified as having no DME, noncentral-involved DME or central-involved DME.
So, when we refer a patient to an ophthalmologist with a diagnosis of proliferative DR (PDR) with or without macular edema, what should we be informing our patients about in terms of possible treatment options they may need?
For more than 40 years the gold standard of treatment for PDR has been PRP. We now know that intravitreal injections of anti-VEGF agents have been shown to be a comparable effective treatment not only for center-involving DME but also as an alternative therapy for PDR.
A post-hoc analysis of randomized multicenter clinical trial data may help us educate our patients one step further. In this recent publication in Ophthalmology, researchers found that treatment with intravitreal ranibizumab resulted in vision gain, with few patients developing central DME. In eyes treated with PRP, those with poorly controlled HbA1c or more severe retinopathy at baseline showed less improvement in visual acuity and greater risk of central DME. However, these anti-VEGF injections require consistent follow-up post-treatment as compared to PRP.
It is interesting to note, however, that researchers at the Will’s Eye Institute recently found differences in patients who returned for long term-follow up and eventually received additional treatment for their PDR. The PRP group recovered most of its vision, and the average visual acuity returned to what it was prior to their long-term follow-up. The anti-VEGF group remained at their decreased vision. Even after several treatment sessions with PRP and additional injections, they were still unable to recover their vision.
This data along with other studies will allow the ophthalmologist to modify his or her treatment plan of PDR to match the aspects of each individual patient.
Reference:
Hsu J, Obeid A. Diabetic retinopathy – The importance of follow-up care. Wills Eye Hospital. Posted September 27, 2018. Accessed December 20, 2018.
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