The mean change in BCVA from baseline to month 6 was +6.6 letters ( 95 % confidence interval [ CI ] , 4.9-8 .3 ) , and after institution of bimonthly treatment the mean change in BCVA at month 12 was +4.8 letters ( 95 % CI , 2.9-6 .7 ; P < 0.001 ) and +6.5 letters ( 95 % CI , 4.2-8 .8 ) at month 18 .