Session Title: Vascular Diseases and Diabetic Retinopathy I
Session Date/Time: Thursday 11/09/2014 | 08:00-10:00
Paper Time: 09:12
Venue: Boulevard C
First Author: : E.Kontou GREECE
Co Author(s): : A. Takis D. Panagiotidis N. Ioannou D. Papaconstaninou P. Theodossiadis
To evaluate and follow up the Retinal Nerve Fiber Layer (RNFL) thickness in patients with diabetes mellitus type II compared to normal subjects of similar age and gender, having first excluded any risk factors for glaucoma, and to investigate the correlation between the RNFL thickness with the severity of diabetic retinopathy at its primary stages and with other ocular and diabetic parameters.
“Attikon” University Hospital, 2nd Department of Ophthalmology, University of Athens, Athens, GREECE
Prospective, noninvasive, case series study of 27 diabetic patients without diabetic retinopathy, 24 diabetic patients with mild retinopathy and 25 normal age-matched subjects (control group, CG). Exclusion criteria for the study included all known predisposing factors for glaucoma. All participants underwent complete ophthalmological examination and imaging with GDx vcc-SLP (Carl Zeiss Meditec, CA, USA) for the evaluation of the RNFL. Multivariate analysis was applied in order to investigate the correlation between RNFL with diabetic parameters such as the duration of diabetes, insulinotherapy and the levels of glycosylated Haemoglobin (HbA1c), and with ocular parameters such as cup-to-disc ratio (C/D), Central Corneal Thickness (CCT) and levels of normal intraocular pressure (IOP). The follow up was 2 years for all three groups and examinations were performed at baseline, 12 and 24 months. Statistical analyses were performed with the Statistical Package for Social Sciences software (SPSS version 14; IBM Corporation, NY, USA). Analysis of variance (ANOVA) was used to assess the differences in the demographic parameters among the three groups. Multivariate factor analysis (R-mode) was performed for each group separately.
From all the results of the GDx-VCC software numerical parameters, the mean inferior average of RNFL and the Temporal – Superior – Nasal – Inferior – Temporal (TSNIT) Std deviation were statistically significantly lower in both diabetic groups compared to CG at baseline examination and during follow up. The Nerve Fiber Indicator (NFI), a value that ranges from 1-100 (1-30 normal, 31-50 borderline, >50 abnormal) based on the entire RNFL thickness map was higher in both diabetic groups compared to CG both at baseline examination and during follow up. The NFI was 21.7±11.9 and 20±8.9 for the diabetic group without retinopathy, 20.8±9.6 and 18.4±9.8 for the group with mild retinopathy and 15.3±5.4 and 14.4±6.6 for the normal subjects, at baseline and 24 months respectively (p=0.04). There was no statistically significant difference between the diabetic groups. Factor analysis showed no significant correlation between the RNFL and all previously mentioned diabetic and ocular parameters. There was no statistically significant difference among the 3 groups regarding the TSNIT average thickness. During both follow up examinations, there was no statistically significant change (reduction) of the RNFL thickness and of the GDx numerical parameters for the three groups compared to baseline examination.
Factor analysis application on ophthalmological data is a novel approach. To our knowledge this is the first time that multivariate analysis has been used to correlate medical and ocular parameters with GDx measurements. As shown by the multivariate analysis in this study, RNFL thickness is independent of CCT, normal IOP, duration of diabetes, use of insulin and HbA1c levels. Contrary to previous studies that have shown more prominent thinning of the RNFL in the superior retina in diabetics, our study shows more pronounce RNFL defect in the lower retina, which can be explained by the fact that blood flow is lower in the inferior retina and therefore it is more vulnerable to the metabolic stress of diabetes. NFI was increased in both diabetic groups even in the absence of any risk factors for glaucoma. It is still debatable whether diabetes is an independent risk factor for glaucoma. 2 years follow up showed no significant reduction of RNFL thickness in all groups, indicating that RNFL damage may occur early in diabetic patients.