Automated gonioscopy photography for iridocorneal angle grading

Abstract

Purpose: The aim of this study is to assess the agreement between manual and automated gonioscopy for iridocorneal angle opening. Methods: The research is a cross-sectional observational study. Manual and automated gonioscopy were performed to consecutive patients in a glaucoma clinic. Iridocorneal angle opening grading was performed according to Shaffer’s classification. Automated gonioscopy was performed with NGS-1 automated gonioscope (NIDEK Co., Gamagori, Japan). The automated gonio-photos were graded by two independent observers. Agreement between automated and manual gonioscopy and also among raters was ascertained by Fleiss’ kappa statistic and comparison of area under curve. Results: In total, 88 eyes of 47 subjects were analysed. Mean age was 63 ± 10 years. Twenty eyes (22.7%) were excluded from grading due to poor quality images. Angle closure was detected in 23.4% with dynamic gonioscopy in comparison with 4.3% using automated image grading. The agreement for angle closure diagnosis between dynamic and automated gonioscopy was low (κ = 0.09 ± 0.10; p = 0.18). The area under curve for detecting eyes with angle closure showed poor accuracy between automated and manual methods (area under curve: 0.53 ± 0.05, 95% confidence interval: 0.44–0.62). There was modest inter-rater agreement for angle opening assessment of automated images with Fleiss’ kappa of 0.17 (95% confidence interval: 0.035–0.238). Conclusion: Manual and automated gonioscopy showed only slight agreement for the assessment of iridocorneal angle opening status. Further improvements of the NGS-1 automated gonioscopy and technique are desired for widespread use in a real-life setting.

Anterior Chamber Angle Assessment Techniques: A Review

“…It enables the visualization of angle structures, through a lens or a prism. The angle structures seen with gonioscopy from posterior to anterior are: the iris root, the ciliary body band (CB), the scleral spur (SS), the pigmented and non-pigmented TM and the Schwalbe's line (SL) [3] (Figure 2).…”

“…Angle closure was detected in 23.4% and in 4.3% of the 88 eyes analyzed, by manual and automated gonioscopy, respectively. Since the agreement between the two techniques was poor, the authors concluded that automated gonioscopy needs further improvements for routine clinical use [3].…”

“…Examination of the eye, including manual focusing time, takes about 1 min, thus requiring good fixation and reasonable patient cooperation. A previous study reported that 28 of the 336 sections (8.33%) acquired with NGS-1 had to be excluded, due to poor image quality after manual selection [59], whereas low quality images have been reported up to 22.5% of cases [3]. Angle closure was detected in 4.3% and in 23.4% of the eyes with NGS-1 automated gonioscopy and dynamic gonioscopy, respectively, in a study by Teixeira et al These results demonstrate that the instrument may have low sensitivity in comparison with gonioscopy [3].…”

“…A previous study reported that 28 of the 336 sections (8.33%) acquired with NGS-1 had to be excluded, due to poor image quality after manual selection [59], whereas low quality images have been reported up to 22.5% of cases [3]. Angle closure was detected in 4.3% and in 23.4% of the eyes with NGS-1 automated gonioscopy and dynamic gonioscopy, respectively, in a study by Teixeira et al These results demonstrate that the instrument may have low sensitivity in comparison with gonioscopy [3]. The inter-rater reliability of standard and automated gonioscopy for angle closure detection is modest, with a Fleiss'kappa of 0.17 (95% confidence interval: 0.035-0.238) [3].…”

“…In patients with glaucoma or glaucoma suspicion, a careful assessment of the ACA should always be performed, allowing direct visualization of the main structures cause of the aqueous humor drainage, directly affecting intraocular pressure [1,2]. Several findings may be associated with an impaired aqueous humor outflow, among them abnormal iris insertion, abnormal pigmentation of the trabecular meshwork (TM), presence of synechiae, blood in the Schlemm's canal (SC), angle recession, abnormal blood vessels in the angle, evidence of anterior segment dysgenesis, and other abnormalities [3].…”