Structure-Function Relationship Evaluated with Standard Automated Perimetry and Time/Spectral Domain OCT in Normal and Glaucomatous Eyes

Abstract

Purpose: : To compare the relationship between retinal mean sensitivity (MS) measured with standard automated perimetry (SAP) and retinal nerve fiber layer (RNFL) thickness analyzed with time- (TD) and spectral-domain (SD) OCT in normal and glaucomatous eyes.

Methods: : Cross-sectional study on 30 POAG patients (30 eyes) (15 M, 15 F, mean age 72±9.2 years) and 22 normal subjects (22 eyes) (10 M, 12 F, mean age 64.2±13.5 years). All subjects underwent: complete examination, SAP (Humphrey, prog.24-2 SITA standard), SD (Spectralis HRA+OCT) and TD (Stratus) OCT imaging of RNFL. Paired Student t-test and Pearson’s correlation coefficient (r) were used for statistical analysis of data obtained with TD and SD-OCT. Spearman’s rank correlation coefficient (r_s) was used to assess the relationship between total and sectoral RNFL thickness measured in 6 peripapillary sectors (T, ST, SN, N, IN, IT) and MS in matching areas and MD (SAP).

Results: : The difference between POAGs and controls was significant with all evaluated parameters (SAP p<0.001 for MD, MS and all 6 considered areas; TD-OCT p<0.001 for mean total RNFL thickness and 5 sectors except T: p=0.008; SD-OCT T: p=0.56, N: p=0.002, IN: p=0.01, p<0.001 for mean total RNFL thickness and other sectors). In POAGs TD-OCT values were significantly inferior to the SD-OCT measured ones only in T and ST (p<0.05), in normal eyes were significantly greater in all sectors except for T and ST. In POAGs TD and SD-OCT showed a good correlation (N: p=0.01, p<0.001 for mean total RNFL thickness and all other sectors). In controls a mild correlation was found (ST: p=0.01, SN: p=0.08, N: p=0.024, IT: p=0.013, p<0.001 only for mean total RNFL thickness and other sectors). In POAGs TD-OCT parameters showed a correlation with SAP: good in IN and IT (p<0.001); mild in ST (p=0.044), IN (p=0.028), mean total RNFL thickness (p=0.05 vs MS, p=0.016 vs MD). SD-OCT showed a correlation with SAP: good in IT (p<0.001), mild in IN (p=0.059) and ST (p=0.037). In normal eyes TD-OCT showed a good correlation with SAP only in IT (p=0.016), whereas no correlation with SD-OCT was found.

Conclusions: : In glaucomatous eyes TD and SD-OCT findings showed a correlation to the matching SAP areas, greater in the inferior RNFL sectors, where the damage precedes the functional defect earlier than in other regions.

Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • visual fields