Local Glaucomatous Defects of the Circumpapillary Retinal Nerve Fiber Layer Show a Variety of Patterns of Progression

A Pattern-Based OCT Metric for Glaucoma Detection

Purpose

To develop and test a novel optical coherence tomography (OCT) metric for the detection of glaucoma based on a logistic regression model (LRM) and known patterns of glaucomatous damage.

Methods

The six variables of the LRM were based on characteristic patterns of damage seen on the OCT thickness maps of the ganglion cell layer plus inner plexiform layer (GCL+) and retinal nerve fiber layer (RNFL). Two cohorts were used to develop the LRM. The healthy cohort consisted of 400 individuals randomly selected from a real-world reference database (RW-RDB) of OCT widefield scans from 4932 eyes/individuals obtained from 10 optometry practices. The glaucoma cohort consisted of 207 individuals from the same 10 practices but with OCT reports with evidence of optic neuropathy consistent with glaucoma (ON-G). Specificity was assessed with 396 eyes/individuals from a commercial RDB. Sensitivity was assessed with individuals with ON-G from different optometry practices.

Results

For the new LRM metric, the partial area under the reciever operating characteristic curve (AUROC) for specificity >90% was 0.92, and the sensitivity at 95% specificity was 88.8%. These values were significantly greater than those of a previously reported LRM metric (0.82 and 78.1%, respectively) and two common OCT thickness metrics: global circumpapillary RNFL (0.77 and 57.5%, respectively), and global GCL+IPL (0.72 and 47.6%, respectively).

Conclusions

The new metric outperformed other OCT metrics for detecting glaucomatous damage.

Translational Relevance

The new metric has the potential to improve the accuracy of referrals from primary care to specialist care via risk scores and calculators, as well as glaucoma definitions for clinical trials. The individual variables of this model may also aid clinical diagnosis.

A Model of Progression to Help Identify Macular Damage Due to Glaucoma

The central macula contains a thick donut shaped region of the ganglion cell layer (GCL) that surrounds the fovea. This region, which is about 12 degrees (3.5 mm) in diameter, is essential for everyday functions such as driving, reading, and face recognition. Here, we describe a model of progression of glaucomatous damage to this GCL donut. This model is based upon assumptions supported by the literature, and it predicts the patterns of glaucomatous damage to the GCL donut, as seen with optical coherence tomography (OCT). After describing the assumptions and predictions of this model, we test the model against data from our laboratory, as well as from the literature. Finally, three uses of the model are illustrated. One, it provides an aid to help clinicians focus on the essential central macula and to alert them to look for other, non-glaucomatous causes, when the GCL damage does not fit the pattern predicted by the model. Second, the patterns of progression predicted by the model suggest alternative end points for clinical trials. Finally, the model provides a heuristic for future research concerning the anatomic basis of glaucomatous damage.