Background: The aim of this study was to analyse functional results of flexible ranibizumab treatment in exudative age-related macular degeneration (AMD), and to search for parameters with impact on outcome.
Methods: Analysis of a retrospective institutional case series (104 eyes) with a low-threshold re-treatment algorithm and monthly follow-up for 12 months.
Results: Visual acuity (VA) improved at month 3 by +6.7 letters and declined slightly until month 12 to a level of +5.0 letters. On average, eyes received 5.8 injections. A significant loss in VA occurred in the whole group between months 5 and 6 (-2.0 letters), never in the "winner" group (improvement of >5 letters at month 12), between months 5 and 6 (-3.8 letters) in the "stabilizer" group (∆ of ± 5 letters at month 12) and twice, between months 3 and 7 (-7.0 letters) and months 9 and 12 (-6.9 letters), in the "loser" group (loss of >5 letters at month 12). These major functional declines followed moderate but significant increases in average CFT (OCT-central foveal thickness) of 23 to 33 μm. Increased CFT followed periods with a low percentage of treated eyes per month in each group. The amount of regained vision was significantly related to the extent of previous functional loss. The critical limit of short-term VA decline that was associated with the possibility for full VA restoration can approximately be quantified at -4 letters. Restoration of short-term VA deterioration (last month) was significantly better than long-term VA loss (related to the end of loading phase). Restoration of VA loss stratifies mainly into two groups: a group that regained -25 to 25% and one that regained 75 to 125%. A significant correlation was found between the number of injections and functional outcome at month 12 for eyes receiving more than four injections. It was calculated that a mean of 8.4 injections per eye would have been necessary to stabilize vision within the first 12 months.
Conclusions: CFT is a sensitive and early predictor of VA deterioration. Four letters of acute VA loss seems to be a critical limit. VA loss of ≥ 4 letters appears to be associated with incomplete recovery. Eyes with <1 line of gain at the end of the loading phase should be considered for continuation of treatment at months 3 and 4. According to our calculations an average number of 8.4 injections/eye seems to be necessary to maintain stabilization of vision in the first year of treatment.