Estimating Lead Time Gained by Optical Coherence Tomography in Detecting Glaucoma before Development of Visual Field Defects

Abstract

Purpose To estimate the diagnostic accuracy and lead time gained by retinal nerve fiber layer (RNFL) thickness measurements from optical coherence tomography (OCT) for detecting glaucoma before the development of visual field defects. Design Observational cohort study. Participants The study group included 75 eyes of 75 patients suspected of glaucoma followed as part of the Diagnostic Innovations in Glaucoma (DIGS) study. These eyes had normal standard automated perimetry (SAP) visual fields at baseline and developed repeatable (3 consecutive) abnormal tests during a median follow-up of 6.3 years. A control group of 75 eyes of 75 healthy subjects matched by age and number of OCT tests during follow-up was included. Methods RNFL thickness measurements were obtained at the time of development of the earliest SAP defect (Time 0) and also at times −1, −2, −3, etc., corresponding to one year, two years, three years, etc., before the development of field loss. OCT measurements at corresponding time intervals were analyzed for controls. Time-dependent receiver operating characteristic (ROC) curves were used to evaluate diagnostic accuracy of OCT. Main Outcome Measures ROC curve areas and sensitivities at fixed specificities at different times before development of field loss. Results At the date of conversion to the earliest visual field defect (Time 0), mean ± SD average RNFL thickness was 75.0 ± 9.8µm in glaucomatous eyes and 90.6 ± 8.0µm for controls (P<0.001). Significant differences were seen up to 8 years before development of visual field defects (86.3 ± 8.2µm versus 91.4 ± 7.6µm, respectively; P=0.021). ROC curve areas decreased with increasing times before detection of field defects. At times 0, −4 and −8 years, ROC curve areas were 0.87, 0.77 and 0.65, respectively. At 95% specificity, up to 35% of eyes had abnormal average RNFL thickness 4 years before development of visual field loss, and 19% of eyes had abnormal results 8 years before field loss. Conclusion Assessment of RNFL thickness with OCT was able to detect glaucomatous damage before the appearance of visual field defects on SAP. In many subjects, significantly large lead times were seen when applying OCT as an ancillary diagnostic tool.

Adaptive optics optical coherence tomography in glaucoma

“…Currently, diagnosis of glaucoma is confirmed based on the presence of typical VF defects on standard automated perimetry (SAP) and corresponding signs of glaucomatous ONH and retinal damage; and thus the diagnosis of moderate to severe cases of glaucoma is relatively straightforward. However, it is often thought that glaucomatous structural damage precedes vision loss (Artes and Chauhan, 2005; Kuang et al, 2015; Medeiros et al, 2009a; Quigley et al, 1992; Sommer et al, 1991; Strouthidis et al, 2006; Wollstein et al, 2005) with the disease frequently remaining asymptomatic in its early stages. It is worth noting that observed pre-perimetric structural losses could be an artifact of the testing method.…”

Comparison of Glaucoma Progression Detection by Optical Coherence Tomography and Visual Field

“…34 OCT on the other hand is generally regarded as being more sensitive in detecting progression in the earlier stages of the disease. 6,35–37 Since OCT measurements have good repeatability and reproducibility, 17 it may be clinically advantageous to monitor glaucoma progression using objective OCT structural measurements, compared to VF, a subjective test that may have problems with reliability in some patients.…”

Association between Intraocular Pressure and Rates of Retinal Nerve Fiber Layer Loss Measured by Optical Coherence Tomography

“…However, there is evidence that many patients can progress by structural tests while not showing detectable change by functional measures. 4, 8, 9 In addition, these structural changes have been shown to be predictive of future functional losses and decrease in quality of life in glaucoma patients. 8–12 …”