A novel iris transillumination grading scale allowing flexible assessment with quantitative image analysis and visual matching

ABSTRACT

Purpose: To develop a sensitive scale of iris transillumination suitable for clinical and research use, with the capability of either quantitative analysis or visual matching of images.

Methods: Iris transillumination photographic images were used from 70 study subjects with ocular or oculocutaneous albinism. Subjects represented a broad range of ocular pigmentation. A subset of images was subjected to image analysis and ranking by both expert and nonexpert reviewers. Quantitative ordering of images was compared with ordering by visual inspection. Images were binned to establish an 8-point scale. Ranking consistency was evaluated using the Kendall rank correlation coefficient (Kendall’s tau). Visual ranking results were assessed using Kendall’s coefficient of concordance (Kendall’s W) analysis.

Results: There was a high degree of correlation among the image analysis, expert-based and non-expert-based image rankings. Pairwise comparisons of the quantitative ranking with each reviewer generated an average Kendall’s tau of 0.83 ± 0.04 (SD). Inter-rater correlation was also high with Kendall’s W of 0.96, 0.95, and 0.95 for nonexpert, expert, and all reviewers, respectively.

Conclusions: The current standard for assessing iris transillumination is expert assessment of clinical exam findings. We adapted an image-analysis technique to generate quantitative transillumination values. Quantitative ranking was shown to be highly similar to a ranking produced by both expert and nonexpert reviewers. This finding suggests that the image characteristics used to quantify iris transillumination do not require expert interpretation. Inter-rater rankings were also highly similar, suggesting that varied methods of transillumination ranking are robust in terms of producing reproducible results.

KEYWORDS:

• Albinism
• iris transillumination
• ocular pigmentation
• oculocutaneous pigmentation

Acknowledgments

We would like to acknowledge Professor Benedetto Falsini, Università Cattolica del Sacro Cuore, for helping to grade images and for other useful conversations related to this project.

Supplemental data

Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/13816810.2017.1342134.

Funding

This work was supported by the Intramural Research Programs of the National Eye Institute and National Human Genome Research Institute. MGA and AHB are supported by EY017673.

Additional information

Funding

This work was supported by the Intramural Research Programs of the National Eye Institute and National Human Genome Research Institute. MGA and AHB are supported by EY017673.