Purpose: To perform a phase I/II safety and efficacy study in order to assess the outcome following transpupillary thermotherapy (TTT) for occult choroidal neovascularization (CNV) with no or minimally classic CNV in age-related macular degeneration.
Methods: The study comprised 113 referred patients (79 females, 34 males) aged 59-89 years (mean 77.7 years) with predominantly occult CNV. There were 49 cases of occult with no classic CNV and 64 of occult with minimally classic CNV. According to their greatest linear dimension, lesions were classified as being < 3.0 mm or > 3.0 mm. Transpupillary thermotherapy was delivered with a diode laser, emission at 810 nm, duration 60 seconds, laser power 500-800 mW. Clinical examination, ETDRS logMAR visual acuity and fluorescein angiography were carried out at baseline, and at 3, 6 and 12 months in all cases.
Results: The average baseline visual acuity was 0.20 (50.6 letters). Following TTT, it was 0.12 (42.0 letters) at 6 months and 0.12 (38.0 letters) at 12 months. Visual acuity improved in 9/113 eyes (8.0%), remained unchanged in 46 (40.7%) eyes, and deteriorated in 58 (51.3%) eyes. There was no significant difference in the proportion of eyes that had lost at least 15 letters at 12 months in the subgroup of occult with no classic CNV (18/49; 36.7%) versus those with minimally classic lesions < 3.0 mm (15/39; 38.5%). However, 13/25 (52.0%) of cases with minimally classic lesions > 3.0 mm had lost at least 15 letters at 12 months (p = 0.31). The most common complications in the 46 eyes that suffered visual loss comprised subretinal progressive fibrosis (18 eyes) and atrophy of the retinal pigment epithelium (13 eyes).
Conclusions: This study shows that TTT generally prevents moderate and severe visual loss at 12 months follow-up in occult CNV with no classic CNV. Eyes with minimally classic lesions with a greatest linear dimension of < 3.0 mm also show the same positive outcome. These results compare favourably with published data on the natural course of the disease. However, minimally classic lesions of > 3.0 mm responded poorly in this treatment setting.