The Association Between Clinical Features Seen on Fundus Photographs and Glaucomatous Damage Detected on Visual Fields and Optical Coherence Tomography Scans

Abstract

Purpose: To classify the appearance of the optic disc seen on fundus photographs of healthy subjects and patients with or suspected glaucoma whose diagnosis was based upon visual fields (VFs) and spectral-domain optical coherence tomography (sdOCT) results.

Patients and methods: One eye of 100 patients with or suspected glaucoma and 62 healthy subjects were prospectively tested with 24-2 and 10-2 VF and macular and disc sdOCT cube scans. All eyes with or suspected glaucoma had a 24-2 mean deviation better than -6.0 dB and an abnormal appearing disc on stereophotographs. The retinal ganglion cell plus inner plexiform layer (RGC+) from the macular scans and the retinal nerve fiber layer (RNFL) from the macular and disc scans were segmented and converted to probabilities plots. An eye was considered "glaucoma" if the sdOCT probability plots showed an abnormality in a region that corresponded to a defect seen on the 24-2 and/or 10-2 VF total deviation plot. Similarly, an eye was considered "suspect" only if both the sdOCT and VF plots were normal. Healthy subjects (normal VFs and sdOCT) were classified as "controls" and used as reference for comparisons. Glaucoma specialists reviewed the stereophotographs and classified eyes based on the presence of signs suggestive of glaucomatous optic neuropathy.

Results: The pattern of clinical signs of glaucomatous optic neuropathy seen on stereophotographs was statistically different between glaucoma (P<0.001) and suspects (P<0.001) vs. controls and explained up to 68% of the total variance of the diagnosis based upon sdOCT and VFs. Vertical cup-to-disc>0.6, focal neuroretinal rim thinning, focal RNFL loss, and violation of the ISNT rule had the best performance to differentiate glaucoma and suspects from controls. Compared with the suspect group, glaucoma eyes (abnormal sdOCT and VF tests) were more likely to have vertical cup-to-disc>0.6 (92% vs. 69%, P=0.003), diffuse rim (53% vs. 9%, P<0.001) and RNFL (61% vs. 26%, P<0.001) thinning, and β-zone parapapillary atrophy (68% vs. 17%, P<0.001).

Conclusions: Focal and diffuse signs of glaucoma damage seen on stereophotographs often match damage shown on VFs and sdOCT. In addition, damage shown on VFs and sdOCT is often missed during clinical evaluation. Longitudinal studies ought to differentiate focal signs of glaucoma damage seen on stereophotography from false-positives or very early loss.

Figure 1

The combined retinal ganglion cell and inner plexiform layers (RGC+) of the OCT macular scans and the retinal nerve fiber layer (RNFL) of discs scans were segmented using a computer-assisted manual segmentation technique, down-sampled into 64 pixels and converted to a thickness map and then to a probability map.

Figure 2

Examples of each group: normal (OCT and VFs normal); abnormal (both the 24-2VF and disc cube OCT and/or both 10-2VF and macula cube OCT were abnormal in the same hemifield).

Figure 2

Examples of each group: normal (OCT and VFs normal); abnormal (both the 24-2VF and disc cube OCT and/or both 10-2VF and macula cube OCT were abnormal in the same hemifield).