Optical coherence tomography for glaucoma diagnosis: An evidence based meta-analysis

Methodological quality of the review: Low confidence

Authors: Kansal V, Armstrong JJ, Pintwala R, Hutnik C

Region: Not reported

Sector: Glaucoma

Sub-sector: Diagnosis

Equity focus: Patients aged 18 years and older

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Early detection, monitoring and understanding of changes in the retina are central to the diagnosis of glaucomatous optic neuropathy, and vital to reduce visual loss from this progressive condition.

Objectives:

To compare glaucoma diagnostic accuracy of commercially available optical coherence tomography (OCT) devices (Zeiss Stratus, Zeiss Cirrus, Heidelberg Spectralis and Optovue RTVue, and Topcon 3DOCT).

Main findings:

A total of 150 studies were included in the review. 67 (44.7%) studies were case-control studies, 73 (48.7%) were cross-sectional studies, and 10 (6.7%) were cohort studies. 34 (22.7%) used visual field as a reference standard, six (4.0%) used disc appearance, 110 (73.3%) used a combination of structural and functional criteria. 55 studies examined the Zeiss Cirrus OCT, 49 studies assessed Zeiss Stratus OCT, 23 studies evaluated Heidelberg Spectralis, 38 studies examined Optovue RTVue, and 14 studies evaluated the Topcon 3D-OCT. There were 50.0% male, and 50.0% female glaucoma patients (reported in 150 studies). Controls were 46.5% male, 53.5% female (reported in 109 studies). The mean age of glaucoma patients was 58.8 ± 11.2 and of controls was 54.1 ± 11.1.

The authors note that the overall methodological quality of all included studies was strong in terms of risk of bias and applicability to the research question. Of note, there was an unclear risk of bias in patient selection for 59 (39.3%) studies. This was largely due to inadequate reporting of patient selection methods in these manuscripts; thus, risk of bias was unable to be ascertained.

The studies included 16,104 glaucomatous and 11,543 normal control eyes. Key findings reported by the authors include: AUC-ROC of glaucoma diagnosis for retinal nerve fiber (RNFL) average for all glaucoma patients was 0.897 (0.887±0.906, n = 16,782 patient eyes), for macula ganglion cell complex (GCC) was 0.885 (0.869±0.901, n = 4841 eyes), for macula ganglion cell inner plexiform layer (GCIPL) was 0.858 (0.835±0.880, n = 4,211 eyes), and for total macular thickness was 0.795 (0.754± 0.834, n = 1,063 eyes).

Based on the findings, the authors concluded that the classification capability was similar across all five OCT devices. More diagnostically favorable AUC-ROCs were demonstrated in patients with increased glaucoma severity. Diagnostic accuracy of RNFL and segmented macular regions (GCIPL, GCC) scans were similar and higher than total macular thickness. This study provides a synthesis of contemporary evidence with features of robust inclusion criteria and large sample size.

Methodology: 

All studies that assessed the diagnostic accuracy of OCT for detection of glaucoma were considered for inclusion in this review. The authors included studies with a broad gold standard clinical practice. Patient were 18 years of age or above. Included studies assessed at least one of five devices, namely Stratus OCT (Carl Zeiss Meditec, Jena, Germany), Cirrus OCT (Carl Zeiss Meditec), Spectralis OCT (Heidelberg Engineering Inc., Heidelberg, Deutschland), RTVue (Optovue Inc., Freemont, United States), and 3D-OCT (Topcon, Tokyo, Japan).

The authors conducted a search on the following databases: MEDLINE (Ovid MEDLINE(R) Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily, Ovid MEDLINE and Versions(R)), EMBASE (Embase Classic+Embase), CINAHL, Cochrane Library1 (Wiley Library), Web of Science, and BIOSIS. Two reviewers independently screened studies for inclusion. Quality assessment of diagnostic accuracy studies used QUADAS version2.

The authors conducted a meta-analysis using MedCalc. Meta-analysis for the AUC-ROC was selected instead of other measures such as sensitivity and specificity. The authors note that AUC-ROC reflects both the sensitivity and specificity of a diagnostic test, can be compared across studies, and can be combined between similar studies when measures of uncertainty (standard error (SE) or confidence interval (CI)) are provided.

Applicability/external validity:

The authors note that as the goal of this investigation was to maximize generalizability and applicability to clinical practice, a broad gold standard was accepted for inclusion – that is, white on white automated perimetry, optic disc appearance (clinically or by photograph), or a combination thereof. Therefore, the authors note that findings may provide guidance to clinicians when navigating this rapidly evolving diagnostic area characterized by numerous options.

Geographic focus:

Not reported

Summary of quality assessment:

Overall, there is low confidence in the conclusions about the effects of this study. The authors did not conduct a thorough search of the literature to ensure that all relevant studies were included in the review. In addition, it is not clear if the authors avoided bias whilst extracting data of included studied studies, which may impact in the reliability of findings.