Progression of Ganglion Cell-Inner Plexiform Layer Thinning Assessed by Optical Coherence Tomography Guided Progression Analysis

Abstract

Purpose : To examine the performance of Guided Progression Analysis (GPA) in spectral-domain optical coherence tomography (OCT) to detect ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) progression.

Methods : A total of 85 eyes of 49 glaucoma patients with a mean follow-up time 5.2 years were included. Macular GCIPL thickness and circumpapillary RNFL thickness were measured at least four times by CIRRUS™ HD-OCT 4000 (ZEISS, Dublin, CA) and visual field (VF) SITA Standard 24-2 tests were performed at the same visits. CIRRUS GPA can perform event analysis and trend analysis for RNFL and GCIPL thicknesses. Event analysis assesses change from baseline compared to expected variability. If change is outside the range of expected variability, it is identified as progression. Trend analysis looks at the rate of change over time, using linear regression to determine rate of change. Glaucomatous eyes were classified as either early (50 eyes) or advanced (35 eyes) according to VF severity (Mean Deviation better or worse than -6 dB). Reference standard of glaucoma progression was determined by expert assessment of VF tests. Sensitivity and specificity of GCIPL and RNFL GPA, and agreement between OCT GPA findings and reference standard were estimated.

Results : A total of 37 (43.5%) and 23 (27.1%) eyes were identified as progression by GCIPL and RNFL GPA, respectively, and 26 (30.6%) eyes showed progression by reference standard (see Fig. 1). The sensitivity and specificity of GCIPL GPA for detecting glaucoma progression were 84.6% and 74.6%, while those of RNFL GPA were 50.0% and 83.1%. Agreement between GCIPL or RNFL GPA and reference standard was moderate (κ=0.465 and 0.503, respectively) in early stage glaucoma. However, GCIPL GPA (κ=0.625) showed better agreement with reference standard than RNFL GPA (κ=0.045) in advanced stage glaucoma. An example is shown in Fig 2.

Conclusions : GCIPL GPA provides a new approach to evaluate glaucoma progression. It may be useful for detecting progression in advanced stage of glaucoma.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig. 1. Venn diagram showing detection of progression by GCIPL GPA, RNFL GPA, and reference standard.

 

Fig. 2. Representative case of GCIPL progression in advanced glaucoma. Due to the ‘floor effect’, no further structural change can be detected in RNFL GPA. However, GCIPL GPA can detect structural progression corresponding with VF change.