To evaluate the effect of sparing the horizontal meridian during Pan Retinal Photocoagulation (PRP) for proliferative diabetic retinopathy (PDR) on corneal sensation, tear film parameters and to assess the pain in different retinal areas.
Design
Prospective comparative interventional study
Subjects
Patients were randomized to either Group (A): conventional PRP or Group (B): PRP with sparing of the horizontal meridian.
Main outcome
Comparing the change in central corneal sensation and the precorneal tear film parameters between the 2 groups
Methods
50 patients were divided into the two groups at random. The corneal sensation was evaluated by the Cochet Bonnet aesthesiometer & the tear film stability was evaluated by the Schirmer tests (1&2) & the Tear break up time (TBUT). The pain was recorded using a scale of 0–3 in different retinal areas.
Results
The corneal sensation decreased with a nonsignificant difference between the 2 groups through the follow up visits. Regarding the tear film stability, Schirmer test (1), (2) & TBUT decreased with a significant difference in the change from the baseline between the 2 groups (p-value for Schirmer test (1) <0.001, 0.001, 0.001, P-value of Schirmer test (2) 0.007, 0.001, 0.001, P-value of TBUT 0.03, 0.001, 0001 for 1 week, 1and 3 months respectively). Regarding the pain sensation during the PRP, the pain score was the highest in the horizontal meridian and was higher in the peripheral retina than in the central retina and in the lower retina than in the upper retina.
Conclusion
PRP performed with sparing of the horizontal meridian was found to maintain the tear film's stability with less pain increasing patient compliance with therapy.
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