Retinal Ganglion Cell Count Estimates in Primary Angle Closure

Abstract

 

Purpose

 

To compare the retinal ganglion cell (RGC) count estimates, which combines structural and functional measures, in subjects categorized as, primary angle closure (PAC), primary angle closure glaucoma (PACG) and healthy controls.

 

Methods

 

Angle closure subjects were recruited from glaucoma clinics and healthy normal controls were recruited from the general population. Standard automated perimetry sensitivity thresholds (Swedish Interactive Threshold Algorithm Standard 24-2 strategy) and average retinal nerve fiber layer (RNFL) thickness with spectral domain optical coherence tomography (SD-OCT, Cirrus HD-OCT, Carl Zeiss Meditec Inc,. Dublin, CA) were measured from all the eyes. The estimates of RGC counts were obtained according to a model developed by Medeiros et al based on empirical formulas derived by Harwerth et al, utilizing information from both structural and functional tests . We used analyses of covariance (ANCOVA) to estimate mean RGC counts in the groups adjusted for gender, intraocular pressure, anterior chamber depth and axial length. Area under receiver operating characteristic curves (AUCs) was used to assess the ability of RGC count and SD-OCT RNFL thicknesses to discriminate PACG and PAC from healthy controls. Only one eye was selected from each subject.

 

Results

 

We included 41 eyes of PAC, 55 eyes of PACG, and 464 healthy eyes in the analysis. The adjusted mean (standard error) RGC counts were 1000.3 (7.50), 632.0 (26.2) and 452.2 (22.9) (x1000 cells) in healthy, PAC and PACG eyes, respectively. The RGC count showed a significant reduction across the groups (p-trend<0.001) (Figure 1). Compared with the healthy controls, the PAC and PACG eyes had significant lesser RGC counts (all p<0.001). PACG eyes had significant lesser RGC counts (all p<0.001) than PAC eyes. The RGC counts performed better in the ability to discriminate PACG (AUC 0.98 vs. 0.89, p<0.001) and PAC (AUC 0.91 vs. 0.66, p<0.001) from healthy eyes, compared with average RNFL thickness.

 

Conclusions

 

A significant reduction of RGCs loss were observed in PAC and PACG eyes, compared with healthy eyes. The recent method to estimate RGC counts on the basis of a combination of structural and functional tests are useful to assess RGC loss in primary angle closure.

 

 

The retinal ganglion cell (RGC) count estimates, which combines structural and functional measures, show significant reduction across the groups.

 

Keywords: 550 imaging/image analysis: clinical • 758 visual fields • 531 ganglion cells