Structure function relationships in the glaucomatous macula comparing 10-2 and 24-2 visual fields

Abstract

 

Purpose

 

To assess the relationship between 10-2 and 24-2 standard automated perimetry (SAP) sensitivities and optical coherence tomography (OCT) macular thickness measurements in healthy and glaucomatous subjects.

 

Methods

 

374 eyes from 223 subjects enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS) underwent 10-2 and 24-2 SAP and macular imaging using Cirrus OCT. The study included 76 healthy eyes, 146 glaucomatous eyes and 152 eyes with suspected glaucoma. Average SAP sensitivities were calculated for each eye for the entire 10-2 test, the entire 24-2 test, and the central 16 locations of the 24-2 test (corresponding to the central 10 degrees). The combined thickness of the macular ganglion cell layer and inner plexiform layer (mGCIPL) was obtained using Cirrus OCT and a regression model was utilized to assess the relationship between SAP sensitivity (in linear units) and mGCIPL thickness. Circumpapillary retinal nerve fiber layer (cpRNFL) thickness was also assessed.

 

Results

 

Average mGCIPL thicknesses for healthy, glaucomatous and suspect eyes were 81.0 μm, 68.9 μm, and 75.8 μm respectively. The relationships between mGCIPL thickness and SAP sensitivity were similar for the total 10-2, total 24-2, and central 24-2 test locations (R² = 0.325, 0.366 and 0.366 respectively). Eyes with more severe glaucoma (cpRNFL thickness <75μm) displayed stronger macula structure-function correlation than eyes with less severe glaucoma (cpRNFL thickness >85μm) (R² = 0.503 versus R² = 0.233 respectively for 10-2, R² = 0.294 versus R² = 0.182 for total 24-2, and R² = 0.400 versus R² = 0.262 for central 24-2). Older age was associated with decreased 10-2 and 24-2 sensitivities and a thinner mGCIPL. In healthy subjects, each decade of age corresponded to a 2.1μm thinner mGCIPL.

 

Conclusions

 

Overall there was only moderate correlation between mGCIPL thickness and SAP sensitivity, emphasizing the need to test both structural and functional domains. However, there was a stronger macula structure-function relationship in eyes with more severe disease, particularly using the 10-2 test strategy.

 

 

The relationship between 10-2 SAP sensitivities and mGCIPL average thickness

 

Keywords: 531 ganglion cells • 550 imaging/image analysis: clinical • 585 macula/fovea