Abstract
Purpose: :
To examine the effect of panretinal photocoagulation (PRP) on the peripapillary retinal nerve fiber layer (RNFL) in patients with diabetic retinopathy.
Methods: :
For the study, patients were divided into treatment and control groups. The eyes which had any condition that could influence the RNFL were excluded. The final sample included 130 eyes (75 patients) for the treatment group and 186 eyes (93 patients) for the control group. The peripapillary RNFL thickness was measured before the PRP and 6 months after PRP in the treatment group. In the control group, It was measured at the baseline of the study, and 6 months later respectively. The peripapillary RNFL thickness was measured with optical coherence tomography (Stratus Zeiss, U.S.A.). A time interval changes of the RNFL thickness were studied on both groups. Series of ANOVA, t-test, chi-square, and correlation were conducted with using SPSS to examine the relationship between the changes in the RNFL thickness and 1) the number of laser burns, 2) level of HbA1c, and 3) duration of diabetes.
Results: :
In the treatment group, post-PRP peripapillary RNFL thickness decreased average of 15µm (pre-PRP 359µm, post-PRP 344µm. p<0.001), while average of 7µm (baseline 382µm, 6 months later 375µm. p<0.001) decrease was shown in the control group. However, the changes were not statistically different between these two groups. In addition, a relationship between numbers of laser burns and changes in RNFL thickness was not significant in the treatment group (p>0.05). In the treatment group, post-PRP vision increased average of 0.05 (pre-PRP 0.28, post-PRP 0.33. p<0.001). In control group, post-PRP vision decreased average of 0.03 (baseline 0.85, 6 months later 0.82. p<0.001). The degree of vision change among treatment and control groups were significantly different (p<0.001). A relationship between the numbers of laser burns and changes in vision was not significat in the treatment group (p>0.05). No differences was found between changes of the RNFL thickness and duration of diabetes in both groups (p>0.05). But the higher the HbA1c level was, the more the post-PRP peripapillary RNFL thickness decreased in the treatment group. The difference of RNFL thickness change between two grous was statistically significnat (p<0.001).
Conclusions: :
Although there was a decrease in the peripapillary RNFL thickness after PRP in the diabetic retinopathy in treatment group, when the group was compared to the control group, the difference was not statistically significant.However, there was a significant improvement in visual acuity after the PRP.
Keywords: diabetic retinopathy • laser