Optical coherence tomography evaluation of peripapillary and macular structure changes in pre-perimetric glaucoma, early perimetric glaucoma, and ocular hypertension: A systematic review and meta-analysis

Author: Tong Y, Wang T, Zhang X, He Y, Jiang B.

Geographical coverage: Turkey, India, China, Korea, United States of America (USA), Italy, Japan, Hungary, Poland, Germany, Greece.

Sector: Biomedical

Sub-sector: Diagnostics

Equity focus: Not reported

Study population: Patients with glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background 

Glaucoma, a leading cause of blindness, involves progressive retinal ganglion cell loss and visual‑field damage, often associated with elevated intra‑ocular pressure (IOP). Early detection is challenging because the disease is frequently asymptomatic. Optical coherence tomography (OCT) provides high‑resolution imaging to detect structural changes, such as retinal nerve‑fibre‑layer thinning, but its diagnostic value in early disease remains uncertain.

Objectives 

To clarify structural changes measured by OCT across the spectrum from ocular hypertension (OHT) to pre‑perimetric glaucoma (PPG) and early perimetric glaucoma (EPG), thereby informing early detection and intervention.

Main findings 

OCT‑derived measurements of peripapillary and macular structures can distinguish PPG from EPG and OHT.

Twenty‑three cross‑sectional studies (2 574 eyes: 1 101 PPG, 1 233 EPG and 240 OHT) were included; three were high quality and 20 medium quality.

Compared with PPG, eyes with EPG had significantly thinner average peripapillary retinal nerve‑fibre layer (pRNFL; weighted mean difference [WMD] 8.22 µm, 95 % CI 6.32–10.12), macular ganglion cell + inner plexiform layer (mGCIPL; WMD 4.83 µm, 95 % CI 3.43–6.23) and macular ganglion cell complex (mGCC; WMD 7.19 µm, 95 % CI 4.52–9.85). Sectoral analyses showed similar patterns.

PPG eyes also had thinner average pRNFL (WMD −8.57 µm, 95 % CI −9.88 to −7.27) and mGCC (WMD −3.23 µm, 95 % CI −6.03 to −0.44) than OHT eyes. Subgroup analyses confirmed these findings across OCT devices and glaucoma types.

Methodology 

PubMed, Embase and the Cochrane Library were searched to March 2021 for studies including PPG with either EPG or OHT using consistent diagnostic criteria and reporting at least one OCT‑measured parameter (pRNFL, mGCIPL or mGCC thickness).

Three reviewers independently carried out searching, data extraction and quality appraisal using the Agency for Healthcare Research and Quality checklist. Fixed‑effect models were applied when I² < 50 %; otherwise, random‑effects models were used. Subgroup and sensitivity analyses explored device type, glaucoma subtype and scan area. Publication bias was assessed with Begg’s and Egger’s tests.

Applicability / external validity 

The findings support the clinical utility of OCT for distinguishing early glaucoma stages, but longitudinal studies using clock‑hour analyses are needed to track progression.

Geographic focus 

Studies were conducted in 11 countries across Asia, Europe and North America.

Summary of quality assessment 

Bias was assessed but results were not stratified by risk level, and reference lists were not searched. Excluded studies were not listed and study authors were not contacted for additional data.