Subjective perception versus objective outcome after intravitreal ranibizumab for exudative AMD

Abstract

The efficacy of ranibizumab in preserving visual acuity in exudative age-related macular degeneration (AMD) has been widely demonstrated. However, statistically significant improvements in outcome measures such as best-corrected visual acuity (BCVA) may not necessarily be clinically relevant. Clinical relevance can be assumed when the treatment success is perceivable for the patient. We therefore investigated the relation between subjective perception of the treatment success and the objective outcome after intravitreal ranibizumab treatment. In this prospective interventional case series, patients received three monthly ranibizumab injections for exudative AMD. To assess the subjective study outcome (SSO) 4weeks after the third injection, patients had to grade the overall trend of visual quality in the treated eye since baseline. Objective changes of functional (BCVA measured with ETDRS reading charts; reading visual acuity (RVA) and reading speed measured with Radner reading charts) and morphological parameters (central retinal thickness measured with OCT) were evaluated. Agreement between SSO and objective parameters was assessed with nonparametric statistical tests. Seventy-four eyes of 74 patients were analyzed. Mean BCVA increased from 55 (SD ±13) ETDRS letters by +3.16 letters (SD ±11.99, p = 0.03). Mean RVA (measured as logRAD score) increased by -0.067 (SD ±0.294, p = 0.052). Fifty patients (68%) perceived a subjective improvement, 16 (21%) no change, and eight (11%) a worsening in the study eye (SSO). SSO was independent of whether treating the better- or worse-seeing eye (p = 0.83). SSO was significantly correlated with BCVA, RVA, and reading speed (as assessed using the critical print size (CPS)) changes (p = 0.002, p < 0.001, and p = 0.002), but showed no correlation to central retinal thickness changes (p = 0.783). Patients gaining ≥ +5 ETDRS letters had a significantly better SSO (p = 0.001). The rate of subjective improvement increased distinctly to >80% among patients gaining ≥ +7 letters. In this study, 2/3 of patients reported a subjective improvement from ranibizumab injections. Patients' perception was significantly correlated with objective changes in BCVA and reading visual acuity. Our data indicate that the mean threshold for perceived improvement is a +5 to +7 letter gain, which might accordingly be considered clinically meaningful and relevant. Patients' perception was independent of whether the better- or worse-seeing eye was treated.