Glaucoma Diagnostic Capability of Circumpapillary Retinal Nerve Fiber Layer Thickness in Circular Scans with Different Diameters

Abstract

 

Purpose

 

To compare the diagnostic capability of circumpapillary retinal nerve fiber layer thickness (RNFLT) for glaucoma among circular scans with different diameters.

 

Methods

 

Circumpapillary RNFLT was measured using spectral-domain optical coherence tomography (OCT) (Spectralis; Heidelberg Engineering, GmbH, Dossenheim, Germany) in one randomly selected eye of normal subjects and glaucoma patients. Three circular scans with diameters of 3.5 mm, 4.1 mm, and 4.7 mm were used. The Spectralis OCT software provided 7 RNFLT parameters: mean global (G) RNFLT and mean RNFLT for the temporal-inferior (TI), nasal-inferior (NI), temporal-superior (TS), nasal-superior (NS), nasal (N), and temporal (T) sectors. Receiver operating characteristic curves assessed the ability of each parameter to detect glaucomatous changes. The areas under the receiver operating characteristic curve (AUCs) were compared among different RNFLT parameters.

 

Results

 

60 normal eyes (60 subjects) and 66 glaucomatous eyes (66 patients; visual field mean deviation = -7.33±6.73 dB) were included. Mean age was 57±19 and 60±15 years, respectively (p = 0.10). In all 3 circular scans, mean TI RNFLT had the greatest AUC (0.975-0.986), followed by mean G RNFLT (0.954-0.956), among 7 parameters (Table 1). The AUC of mean TI RNFLT in the 4.1-mm scan (0.986) was greater than the AUCs of mean TI RNFLTs in the 4.7- (0.982) and 3.5-mm (0.975) scans, although statistically insignificant (p = 0.403 and 0.062, respectively). The AUC of mean G RNFLT in the 4.1-mm scan (0.956) was greater than the AUCs of mean G RNFLTs in the 4.7- (0.954) and 3.5-mm (0.954) scans, although statistically insignificant (p = 0.718 and 0.695, respectively). The AUC of mean TI RNFLT in the 4.1-mm scan (0.986) was significantly greater than the AUCs of mean G RNFLTs in the 3.5- (0.954), 4.1- (0.956), and 4.7-mm (0.954) scans (p = 0.011, 0.012, and 0.014, respectively). In 2 eyes (1 normal eye and 1 glaucomatous eye) with large parapapillary atrophy, RNFL segmentation error was noted in the 3.5-mm scan, but not in the 4.1- or 4.7-mm scan (Figure 1).

 

Conclusions

 

In general, 4.1-mm scan parameters had greater AUCs than the other scan parameters. Mean TI RNFLT in the 4.1-mm scan had the best diagnostic performance to detect glaucoma. OCT RNFL scan artifacts caused by parapapillary atrophy may be reduced by using larger diameter scans.