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Automated anterior chamber angle pigmentation analyses using 360° gonioscopy
  1. Masato Matsuo1,
  2. Simone Pajaro2,
  3. Andrea De Giusti2,
  4. Masaki Tanito1
  1. 1 Ophthalmology, Shimane University Faculty of Medicine, Izumo, Japan
  2. 2 Nidek Technologies Srl, Albignasego (PD), Italy
  1. Correspondence to Dr Masato Matsuo, Ophthalmology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan; mmpeaceful{at}


Purpose To assess the pigmentation distribution in the iridocorneal angle using an established algorithm with gonioscopically obtained images.

Methods Manual and automatically modified Scheie’s pigmentation grading (ie, 0/I=0, II=1 and III/IV=2) of trabecular meshwork was performed using an established algorithm on the 75 open-angle eyes of 75 subjects obtained by automated gonioscopy. All images were collected at the Matsue Red Cross Hospital in 2016. The differences in the pigmentation density were compared statistically between the automated and manual techniques and among the four sectors (ie, inferior, superior, temporal and nasal) and the four quadrants.

Results There was substantial agreement between both grading methods (kappa value=0.70). There was no significant difference between the automated and manual grading in any sectors except for the superior (p=0.0004). The automated pigmentation grade was significantly (p<0.05) higher in the inferior sector (mean grade, 1.43) than in the others (mean grade, 0.48~0.76), and it was also significantly (p<0.05) higher in the inferior quadrant (mean grade, 3.56) than in the others (mean grade, 1.64~2.24). The findings were similar for manual grading.

Conclusions The entire distribution of the pigmentation in the anterior chamber angle was classified successfully using the algorithm, and the automated versus manual grading comparison showed good agreement. The automated pigmentation grading scores in the inferior sector and inferior quadrant were significantly higher than in the others as previously reported. Similar findings also were seen for manual grading.

  • glaucoma
  • angle
  • anterior chamber
  • imaging
  • diagnostic tests/investigation

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  • Contributors MT conceived and designed the trial. MM and MT were the chief investigators and oversaw the trial throughout. ADG and SP mainly established the algorithm and performed the automatic pigmentation grading. MM monitored the data and performed analyses. All authors contributed to the interpretation of data, drafting of the report and decided on its content. All authors approved the final version.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests MT (F, lease of prototypic gonioscope from Nidek Co., Ltd.), ADG (C, Nidek Technologies Srl; E, Nidek Technologies Srl) and SP (C, Nidek Technologies Srl; E, Nidek Technologies Srl).

  • Patient consent for publication Obtained.

  • Ethics approval The institutional review board of the Matsue Red Cross Hospital reviewed and approved the research. All research adhered to the tenets of the Declaration of Helsinki.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon request.