Application Of Retinal Thickness Analyzer In Assessment Of Retinal Thickness In Diabetic Retinopathy

AimMultiple pathological changes result from diabetic mellitus might affect eye tissues, the important one of which is diabetic retinopathy (DRP). Diabetic macular edema (DME) is one of the leading causes of visual impairment among patients with diabetes. Early detection and diagnosis are important to successfully treat diabetic macular edema. The scanning retinal thickness analyzer (RTA), a novel instrument developed for non-invasive, multiple optical cross sectional retinal visualizations, provides objective and quantitative measurements of retinal thickness. The higher resolution ability made it possible to detect subtle changes of retinal thickness. The purpose of this study is to evaluate the RTA examination, as an objective test, in diagnosing and quantitatively measurement of central macular and posterior polar retinal thickness of diabetic retinopathy. We also investigate the effects of some relative factors on RTA examination, such as age, refractive error, clarity of the lens, contact lens wearing and blood glucose. Clinical data are to be provided to facilitate the application of RTA in early diagnose of diabetic retinopathy.Materials and MethodsThe Retinal Thickness Analyzer (RTA; Talia Technology Ltd., Neve-Ilan, Israel, software Version: 4.10 ) was used to analysis 147 eyes of 107 individuals of diabetes mellitus in our study. Main parameters included PMAT (Posterior-Pole Maximum Thickness), PFMT(Per-Foveal Maximum Thickness), PPAT(Posterior-Pole Average Thickness), PFAT (Per-Foveal Average Thickness), FAT (Foveal Average Thickness), PPNTC (Posterior-Pole Number of thickCluster). Subjects were divided into groups according to the Diabetic Retinopathy Disease Severity Scale (2003) and Diabetic Macular Edema Disease Severity Scale (2003). 38 normal eyes were involved as age matched control. Investigation on normal subjects was conducted on relative factors that might influence retinal thickness examination, which included age, sex, refractive error, contact lens and cloudy of the lens. Repeated measures analysis of variance (ANOVA), two-tailed Student's t-test and Spearman's correlation coefficient were used to determine any significant interaction between the variability of RTA thickness values. Lens opacities classification system (LCOSIII) was used to classify the degree of clarity of the lens: N (clarity of nuclear); NC (color of nuclear); C (clarity of cortex); P(clarity of posterior capsular). Results1. Normal eyes and related factorsNo difference of retinal thickness was observed between different age groups (f?0.05). In cases that could obtain clearly retinal cross optic images, the lens status according to LCOSIII degree system were as follows: N: 0.1-2.0; NC: 0.1-2.5; C: 0.1-2.1; P:0.1-l. FAT, PFAT and PPAT in eyes of refractive error more than -6.00D were slightly lower than that of less than -6.00D eyes (p>0.05). Contact lens wearing brought PFMT, PPAT, PFAT, FAT and PPNTC lower than that obtained from naked eyes (t-test, p<0.05).2. Retinal thickness changes in DRP(1) RTA results in different DRP scale: Every interclass parameter had significant difference in groups of DPR scales (p<0.01) and DME scales (p<0.05).1). PPMT: Statistically significant differences in DRP groups were presented in: stage 3 comparing with normal, stage 1and stage 2; stage 4 comparing with normal, stage land stage 2; and stage 2 comparing with stage 3and stage 4.(p<0.01)2). PFMT: Statistically significant differences in DRP groups were presented in: stage 4 comparing with normal, stage 1 and stage 2; stage 3 comparing with normal (p<0.01).3). PPAT: Statistically significant differences in DRP groups were presented in: normal comparing with stage 1, 2, 3, 4; stage 1 comparing with stage 3and stage 4(p<0.01).4). PFAT: Statistically significant differences in DRP groups were presented in: normal comparing with stage 1, 2, 3, 4 (p<0.01); stage 1 comparing with stage 3 (p<0.05).5). FAT: Statistically significant differences in DRP groups were presented in: normal comparing with stage 2, 3, 4 (p<0.01); stage 1 comparing with stage 3 and stage 4 (p<0.05).6). PPNTC: Statistically significant differences in DRP groups were presented in: normal comparing with stage 3, and stage 4 (p<0.01); stage 4 comparing with stage 1 and stage 2 (p<0.05).7). Analysis of parameters correlation with DRP scales: FAT (r=0.371, p=0.000), PPAT (r=0.308,p=0.000), and PFAT (r=0.340,p=0.000).(2) RTA results in different DME scale: Every interclass parameter had significant difference in groups of DME scales (p<0.01)1). PPMT and PFMT: Statistically significant differences in DME groups were presented in: severe DME comparing with normal, No DME and Mild DME (p<0.01); Moderate DME comparing with normal (p<0.01).2). PPAT and PFAT: Statistically significant differences in DME groups were presented between normal and other 4 groups (p<0.01).3). FAT: Statistically significant differences in DME groups were presentedin: severe DME comparing with normal, No DME and Mild DME; Moderate DME comparing with normal (p<0.01).4). PPNTC: Statistically significant differences in DME groups were presented in: severe DME comparing with normal, No DME and Mild DME (p<0.01); severe DME comparing with Mild DME (p<0.05).5). Analysis of parameters correlation with DME scales: PFAT (r=0.315, p=0.000) and PPMT (r=0.308,p=0.000).(3) Correlation of duration of PDR and blood glucose with retinal thickness: FAT correlated with duration of PDR (p=0.012, r=0.204); Retinal thickness correlated with concentration of blood glucose (p=0.044, r=0.164).Conclusion1. Related factors involving in RTA examination might influence the outcomes, which need to be avoided and corrected.(1) Aging has no effects on retinal thickness;(2) Opaque optic media might disturb the procedure of acquiring clear section images. An obligation of lens clarity using LOCS III for individuals should be as follows: N: 0.1-2.0; NC: 0.1-2.5; C: 0.1-2.1; P: 0.1 — 1.(3) Contact lens wearing made the results lower than that obtained from naked eyes.2. This study suggests that RTA could detect early changes of retinal thickness in condition of sub-clinical onset of DRP and DME. Changes of posterior pole retinal thickness follow an outside-in order, and involve forveal eventually. Massive edema occurs in early stages, and local change takes place in later.3. Duration of PDR and blood glucose might cause retinal thickness changes.