Abstract
Purpose: :
The leading cause of vision loss in patients with diabetic retinopathy is diabetic macular edema (DME), and the predominant therapy has been laser photocoagulation. It is well known that better systemic glucose control, as measured by hemoglobin A1c (HbA1c), is associated with a reduced risk of developing DME. However, the potential role of HbA1c level in treatment outcomes has never been explored.
Methods: :
Participants underwent laser photocoagulation for DME at the Veterans Affairs Medical Center (VAMC) in West Haven, CT between October 2004 and October 2008. Patients were stratified into 3 categories based on their most recent HbA1c level (within 3 months of laser treatment): good control (HbA1c <7.0%), moderate control (HbA1c= 7.0-9.0%), and poor control (HbA1c >9.0%). These HbA1c categories were based on the former Diabetes Control and Complications Trial. Each treatment session was considered an independent outcome. Visual acuity (VA) was assessed prior to and then 2-3 months after treatment, with change in VA defined as the difference in lines of vision on a Snellen chart. VA was converted to a decimal for calculation purposes then re-converted to standard Snellen notation. All statistical analysis was performed using SAS 9.2. Statistical significance was defined as P <0.05.
Results: :
A total of 282 focal/grid laser therapies were provided to 171 eyes in 125 patients. The average age at the time of treatment was 65.4 ±8.6 years. There were an average of 1.6 treatments per eye (range 1-7), with a majority of eyes undergoing just one treatment (n=110). The overall mean change in VA 2-3 months after treatment was -0.003 ±0.1659 lines, or worsening by 20/7326 ±20/121. There was no VA change for many treatment sessions (n=97). Change in VA was directly correlated with patient age at the time of treatment with a correlation coefficient of 0.162 (P=0.0067).128 treatment sessions were associated with moderate glycemic control, 83 with good control, and 57 with poor control. HbA1c level and change in VA were found to be inversely related. The average VA change in the group with good glycemic control was 0.0126 ±0.16 lines, moderate control was 0.0021 ±0.17 lines, and poor control was -0.0358 ±0.16 lines. The difference in VA change between good versus poor glycemic control reached near statistical significance (P=0.0904). However, treating VA change as a categorical variable showed no significant difference in VA change among the three glycemic control groups based on Chi-square analysis (P=0.2188).
Conclusions: :
Although there was no statistically significant difference in VA change 2-3 months after laser treatment among patients with DME in the three glycemic control groups, there was a trend of improved VA in patients with a lower HbA1c level.
Keywords: diabetic retinopathy • diabetes • laser