Optical coherence tomography (OCT), and visual field (VF) tests used in combination can potentially make evidence-gathering more straightforward, according to a report published in Ophthalmology Glaucoma. The tests included 24-2 and 10-2 guided progression analysis (GPA) and a custom OCT progression report (P-report) as the reference standard to evaluate the effectiveness of 24-2 GPA alone for detecting glaucomatous change.
Researchers examined 70 eyes of 70 patients who were suspected for glaucoma or diagnosed with early open-angle disease, and 29 healthy control individuals. Participants were part of the overall population in the Macular Damage in Early Glaucoma and Progression Study (ClinicalTrials.gov Identifier: NCT02547740). Early disease was defined as 24-2 mean deviation more than -6 dB.
The investigation found that 24-2 GPA examinations conducted alone missed progression that were evident in structural imaging. In fact, the single assessment using default settings missed 60% of eyes recognized as advancing by the combined reference standard tests — a sensitivity of 40%. OCT b-scans revealed thinning of circumpapillary (cp) retinal nerve fiber layer (RNFL), or local damage in the ganglion cell layer of missed progressors. Worsening was also detected by 10-2 VF in 5 of 6 false negatives. Further, all 10 eyes described as progressors by the reference standard exhibited macular involvement.
Specificity of the 24-2 GPA was 93%; 2 eyes it identified as progressors were control individuals, therefore false positives. Nine other eyes labeled as possible or likely progressors by 24-2 GPA were also considered false positives, but if they were actually true positives, damage was minimal due to the cpRNFL appearing healthy in b-scans. “In addition, other studies have suggested that when a mild VF defect is present, the OCT RNFL thickness measures may be more helpful in discerning glaucomatous progression than the 24-2 GPA,” the analysis explains.
Previous studies have found specificity of 24-2 GPA at 83% to 95%, and sensitivity from 75% to 96%. The current investigators speculate this large difference in sensitivity is due to a topographically-oriented reference standard in their design, and inclusion of eyes with exclusively early disease.
During a 4-month initial study period, baseline OCT and VF assessments were performed. All participants had best-corrected visual acuity of at least 20/40. Follow-ups took place 4 to 6 months apart for up to 5 years. Since there is no standard for discerning glaucomatous progression, this study is limited by a qualitative element in its reference standard. Also, 24-2 may perform better in moderate or advanced cases. Investigators speculate that 24-2 GPA should be used together with OCT, and at times 10-2 VF, as well. They suggest that 10-2 GPA may be more effective than 24-2 GPA when a 10-2 glaucoma change probability (GCP) map is offered commercially, and add that the OCT P-report could become a “standalone method for detecting progression.”
Disclosures: Two of the study authors declared affiliations with the biotech, and/or medical device companies. Please see the original reference for a full list of authors’ disclosures.
Hood DC, La Bruna S, Tsamis E, et al. The 24-2 visual field Guided Progression Analysis can miss progression of glaucomatous damage of the macula seen with OCT. Ophthalmol Glaucoma. Published online on March 28, 2022. doi:10.1016/j.ogla.2022.03.007