Retinal thickness analysis (RTA) - An objective method to assess and quantify the retinal thickness in healthy controls and in diabetics without diabetic retinopathy

Background: Since it has been shown that photocoagulation is indicated in patients with diabetic macular edema, quantitative and objective assessment of retinal thickness is of clinical importance. Methods: A laser slit beam was projected on the retina and scanned across a 2 x 2 mm retinal area in 200 msec. Nine type 1 and 2 diabetic patients without funduscopically and photographically visible diabetic retinopathy and 10 healthy controls were scanned with the RTA. The intraindividual and interindividual variabilities of the RTA were determined. Results: The intraindividual and interindividual variability was 5 mum and 15 mum, respectively. The mean value of the mean foveal thickness (MFT) and perifoveal retinal thickness (PFT) in the 10 healthy controls was 152 +/- 15 mum and 175 +/- 14 mum, respectively, and 181 +/- 26 mum and 191 +/- 27 mum, respectively, in the group of nine diabetics without signs of diabetic retinopathy. The MFT in the group of diabetic patients was significantly (P < 0.001) larger than in the control groups. Conclusion: Retinal thickness in diabetic patients without diabetic retinopathy was increased in all measurements in comparison with the findings in healthy subjects. Retinal thickness measurements with the RTA could possibly detect early signs of diabetic retinopathy before funduscopic and photographic signs are visible and may be helpful in guiding treatment.