Safety testing of epimacular brachytherapy with microperimetry and indocyanine green angiography: 12-month results.

PURPOSE

To determine if epimacular brachytherapy is associated with reduced retinal sensitivity or choroidal nonperfusion.

METHODS

A prospective intervention case series of 12 participants with neovascular age-related macular degeneration requiring frequent ranibizumab underwent vitrectomy and epimacular brachytherapy. The Strontium 90/Yttrium 90 source delivered a single 24-Gy dose at the center of the treatment zone. The dose attenuated with increasing distance from the source. Microperimetry and indocyanine green angiography were performed at baseline and 12 months. The main outcome measures were mean sensitivity and choroidal nonperfusion. A linear mixed model was used to assess the association between the dose of radiation and the change in mean sensitivity.

RESULTS

Mean visual acuity remained within 1 letter of baseline at 12 months (-0.33 ± 13.2 letters). There was no statistically significant change in mean sensitivity within the neovascular age-related macular degeneration lesion area (gain of 0.94 ± 3.25 dB; P = 0.339) or in neighboring unaffected retina (0.66 ± 4.14 dB; P = 0.594), defined using fluorescein angiography. Within the lesion area, mean sensitivity improved by an average of 0.23 ± 0.16 dB (P = 0.006) for every additional gray of radiation received. Indocyanine green angiography failed to demonstrate any choroidal nonperfusion or radiation damage at 12 months after the treatment.

CONCLUSION

Stable retinal sensitivity in areas not manifestly affected by neovascular age-related macular degeneration suggests that epimacular brachytherapy does not damage retinal function. The presence of a dose response suggests that the positive effect of epimacular brachytherapy relates more to beta irradiation than vitrectomy.