Optic nerve head and fibre layer imaging for diagnosing glaucoma.

Area of Science:

• Ophthalmology and Visual Sciences
• Medical Imaging and Diagnostics
• Glaucoma Research

Background:

• Traditional glaucoma diagnosis relies on subjective assessment of optic nerve head (ONH) damage and visual field tests.
• Elevated intraocular pressure (IOP) or suspect ONH appearance often prompts diagnostic evaluations.
• Advanced imaging technologies like Optical Coherence Tomography (OCT), Heidelberg Retinal Tomography (HRT), and Scanning Laser Polarimetry (GDx) offer objective measures of ONH and retinal nerve fibre layer (RNFL) thickness.

Purpose of the Study:

• To evaluate the diagnostic accuracy of HRT, OCT, and GDx in detecting ONH and RNFL damage for diagnosing manifest glaucoma.
• To compare the performance of these imaging modalities in a meta-analysis.

Main Methods:

• A systematic review and meta-analysis of prospective and retrospective cohort and case-control studies were conducted.
• Searches were performed on multiple databases, with the most recent search on February 19, 2015.
• A hierarchical summary ROC (HSROC) model was employed for data analysis, focusing on 2x2 data at 0.95 specificity.

Main Results:

• The review included 106 studies analyzing 16,260 eyes. GDx, HRT, and OCT demonstrated remarkably similar diagnostic performance.
• At 0.70 sensitivity and 0.95 specificity, these tests could miss approximately 60 glaucoma cases per 1000 referred individuals.
• Higher sensitivity was observed in studies with more severe glaucoma (worse mean deviation).

Conclusions:

• The diagnostic accuracy of OCT, HRT, and GDx for manifest glaucoma is variable but similar across devices.
• Case-control study designs may have overestimated accuracy, highlighting a limitation in the current evidence base.
• Further diagnostic accuracy studies using consecutive patient selection and clear reporting of risk factors and thresholds are recommended.