Effect of radiation dosage to vital ocular structures on visual outcomes: Re-evaluation for the future

To explore the impact of radiation dosage on vital ocular structures to identify target dosage for vision preservation in patients with uveal melanoma treated with Eye Physics plaque brachytherapy.

Retrospective study.

Patients with choroidal melanoma treated with I-125 brachytherapy between 2017 and 2021 with at least 1-year follow up.

Retrospective chart review was performed. Time-to-event analysis was used to evaluate the effect of total dosage on ophthalmic structures. Other parameters analyzed include initial visual acuity, presence or absence of radiation retinopathy, tumor thickness, and tumor proximity to the fovea and optic nerve. Evaluation was based on 2 events: final best visual acuity of ≤20/200 and visual loss ≥5 lines from baseline. Univariate and multivariate Cox proportional hazards models were used for analysis.

Visual acuity at baseline and each follow up visit.

One hundred thirty-six patients met inclusion criteria. Initial visual acuity was 20/20-20/40 in 71%, and ≤20/200 in 7% of patients. At final visit, 27% patients had 20/20-20/40 and 50% had ≤20/200. Higher total dose and average dose rate to the optic disc, fovea, lens, opposite retina and sclera were associated with worse visual outcomes. Foveal dosage <35 Gy resulted in the greatest proportion of patients maintaining useful vision followed by a dose of <27.5 Gy to the optic nerve.

<35 Gy to the fovea and <27.5 Gy to the optic disc results in >50% of patients maintaining useful vision and may represent dose target values and are important when considering neoadjuvant treatments prior to definitive plaque brachytherapy.