Modeling study finds variable ciliary body anatomy may affect subliminal cyclophotocoagulation dosing in glaucoma

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medRxiv Published April 11, 2026 Medically reviewed April 25, 2026 Study authors: Szabo, A.; Arpadffy-Lovas, T.; Toth-Molnar, E. DOI ↗ By Dr. Lars van Dijk, PhD · Surgical, Procedural & Diagnostic

Key Takeaway

Consider variable ciliary body anatomy when planning cyclophotocoagulation, but await clinical validation.

This modeling study used biometric data from 24,001 eyes in a public database to estimate anatomical parameters relevant to subliminal transscleral cyclophotocoagulation (SL-TSCPC) for glaucoma. It calculated the estimated ciliary body arc length (ECBAL) and the calculated ciliary body distance (CCBD), comparing them to a standard treatment arc length of 22.0 mm. The study did not involve actual procedures or patients.

The main results showed the mean ECBAL was 23.99 ± 1.8 mm, which was positively correlated with axial length (correlation 0.723, p < 0.01) and anterior chamber depth (correlation 0.754, p < 0.01). Only 131 of 24,001 eyes (0.55%) had an ECBAL between 21.7 and 22.0 mm. The mean CCBD was 4.21 ± 0.8 mm, with 1,445 eyes (6.02%) having a CCBD of 3.8 mm. The mean fluence was 120.33 ± 9.0 J/cm². Treating a fixed 22 mm arc versus the individual ECBAL resulted in a mean fluence difference of -8.18 ± 6.9% (range -22.66% to +29.07%).

Safety and tolerability of SL-TSCPC were not reported, as this was not a clinical trial. Key limitations include its purely computational nature, lack of clinical follow-up, and absence of validation against actual surgical or histological measurements. The population source and setting were not fully described. The model suggests the ciliary body arc length is variable, and using a constant 22.0 mm treatment length could lead to under- or overdosing. However, this remains a theoretical finding until tested in clinical practice.

Study Details

EvidenceLevel 5

PublishedMar 2026

View Original Abstract ↓

Purpose:To improve determination of the treatment area for the personalization of subliminal transscleral cyclophotocoagulation (SL-TSCPC) procedures in glaucoma treatment, we designed a biometry based model of the human eye to find the estimated cilary body (CB) arc length (ECBAL) and the calculated CB distance (CCBD). Methods: We developed a rotationally symmetric modified two-sphere eye model based on axial length (AL), mean keratometry (mean K), anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WTW). ECBAL and CCBD were calculated for each eye. Fluence was calculated with standardized parameters. Results: Publicly accessible biometric measurements for 24,001 eyes were pooled for analysis. The mean ECBAL was 23.99+-1.8 mm. The correlations of ECBAL with AL and ACD were 0.723 and 0.754 respectively (p < 0.01). The number of eyes with an ECBAL 21.7-22.0 mm was 131 of 24,001 (0.55%). The mean CCBD was 4.21+-0.8 mm. The number of eyes with a CCBD of 3.8 mm was 1,445 of 24,001 (6.02%). Mean fluence was 120.33+-9.0 J/cm2. A mean difference of -8.18+-6.9%, ranging from -22.66% to +29.07% in fluence was observed with treating only the recommended 22 mm versus the ECBAL. Conclusions: This study demonstrated that use of 22.0 mm as the standard treatment arc length may under or overdose laser treatment in many eyes. Precise estimation or exact localization of the CB treatment area is required to accurately calculate fluence. Translational Relevance:The model proves that CB arc length is a variable while current guidelines consider it a constant