Critical Review of Cataractogenesis and Lens Contouring in Radiation Oncology

The objective is to comprehensively review radiation-induced cataractogenesis and recommend lens contouring guidelines to unify and improve dose reporting that informs future lens constraints.

A thorough literature review was conducted to examine the anatomic, physiological, and pathologic aspects of the lens. Studies on radiation-induced cataracts, including thresholds for cataractogenesis, latency periods, and classification systems, were reviewed. Standardized lens contouring guidelines were developed for use in radiation therapy treatment planning and dose reporting.

The lens is a transparent, avascular structure responsible for refraction and accommodation. It is highly radiosensitive, and radiation-induced cataractogenesis most often presents as posterior subcapsular cataracts, although cortical and nuclear sclerotic changes can also occur. Key risk factors include total dose, fractionation, and dose rate. Cataracts are a well-described late effect after ocular-directed radiation therapy and other treatments that deliver clinically meaningful lens dose (eg, ocular radiation therapy/brachytherapy and total body irradiation), with incidence varying by lens dose, fractionation, patient age, and duration of follow-up. Standard assessment tools-slit-lamp examination and the Lens Opacities Classification System III-are limited by interobserver variability. Scheimpflug tomography offers a promising, objective, quantitative alternative. We present a step-by-step guide to improve consistency in lens delineation for radiation therapy planning, facilitate avoidance when feasible, and standardize lens dose reporting for future studies.

Radiation-induced cataracts are a significant late complication of ocular, brain, total body, and head and neck radiation therapy. Standardized lens contouring guidelines and multidisciplinary collaboration with ophthalmology can improve lens-sparing and enhance detection and management of cataracts. Further research is needed to refine dose thresholds, improve assessment methods, and develop strategies to mitigate cataractogenesis.