To examine changes in corneal biomechanical parametres following panretinal photocoagulation in patients with proliferative diabetic retinopathy

PURPOSE: To investigate the effect of different stages of diabetic retinopathy on corneal biomechanical parametres and central corneal thickness(CCT) and to examine changes in corneal biomechanical parameters and CCT following panretinal photocoagulation (PRP) in patients with proliferative diabetic retinopathy (PDRP) without previous history of laser treatment. MATERIAL AND METHOD: Study included 30 eyes from 30 diabetic patients without diabetic retinopathy (group 1), 35 eyes from 35 diabetic patients with non-PDRP (group 2) , 48 eyes from 30 patients with PDRP (group 3) and 63 eyes from 40 healthy volunteers. In all groups, corneal resistance factor (CRF), corneal hysteresis (CH), Goldmann correlated intraocular pressure (IOPg) and corneal compensated IOP (IOPcc) were measured by Ocular Response Analyzer; central corneal thickness (CCK) was meausured by ultrasonic pachymeter. HbA1c level was determined in all groups. Diabetic groups were compared with each other and also with control group in respect of CH, CRF, IOPg, IOPcc and CCT parameters. All patients with PDR had undergone PRP treatment. CH, CRF, IOPg, IOPcc and CCT parameters before PRP treatment were compared with those of the patients after PRP treatment at months 1, 3, and 6. RESULTS: CH, CRF, IOPcc, IOPg and CCT were not significantly different in Group 1 compared to control group. CH was significantly lower (p=0,04) and IOPcc and IOPg were significantly higher (p=0,001 and p=0,002) in Group 2 compared to control group. CH was significantly lower (p=0,028) and IOPcc, IOPg and CCT were significantly higher (p=0,007,p=0,05 and p=0,018) in Group 3 compared to control group. There were no significant differences in CH, CRF, IOPcc, IOPg and CCT before PRP treatment and after PRP treatment at any given time point in Group 3. Mean HbA1c was 5,42% in control group, 8,16% in Group 1, 8,27% in Group 2, and 8,36% in Group 3. CONCLUSION: In poorly controlled diabetics with diabetic retinopathy, CH is significantly higher compared with those of the healthy subjects and patients without diabetic retinopathy.Panretinal photocoagulation is still the gold standard for treatment of PDR and has no effect on corneal biomechanics in patients with proliferative DRP. KEY WORDS: Diabetes, panretinal photocoagulation, corneal biomechanical parameters