Macular subthreshold transpupillary thermotherapy does not impair macular function

Purpose: To investigate the functional effects of consecutive, superimposed subthreshold transpupillary thermotherapy (TTT) spots on macula affected by neovascular age-related maculardegeneration. Methods: 20 eyes of 20 consecutive patients affected by retinal angiomatous proliferation secondary to age-related macular degeneration were treated with subthreshold TTT. Multiple, consecutive, superimposed subthreshold TTT spots were used in each treatment session (1 to 3 spots; 1.2 and 3 mm in diameter; duration: 60 seconds each spot) . Functional outcome was assessed with visual acuity (ETDRS charts) and fundus-related perimetry ( microperimetry; MP1, Nidek Technologies, Italy). Dynamic indocyanine green and fluorescein angiography were also performed. Treated eyes were examined at: six and 24 hours, four weeks and every three months after TTT. Results: Mean follow-up was 24 months ( 12-36 months). No retina showed any bleaching after TTT. No eye was retreated. Baseline visual acuity remained stable (no change or one line variation). Fundus related perimetry showed: late improvement of fixation (from poor central to central fixation; from relatively unstable to stable fixation), and no early or late significant change of macular sensitivity ( 17.5 ± 1.8 db vs 16.9 ± 1.6 db) over treated areas. Conclusions: Multiple, consecutive , superimposed spots of real subthreshold TTT do not alter macular function in eyes affected by neovascular age-related macular degeneration. These results suggest that the human retina, as the brain, is intrinsically resistant to sublethal hyperthermia, and accurately dosaged TTT may be therapeutically effective without altering macular function.