On the relationship between visual acuity and central retinal (macular) thickness after interventions for macular oedema in diabetics: a review

Purpose The aim was to compare efficacy of treatments for diabetic macular oedema (DMO) from changes in visual acuity (VA) and central macular thickness (CMT). Methods Peer-reviewed articles from 2004 to 2014 reporting intravitreal injections of bevacizumab (IVB), ranibizumab (IVR) or triamcinolone acetonide (IVTA) or laser photocoagulation therapy (LPT) provided data on pre-treatment (baseline) and final outcome measures. Net changes and relative changes (percentage) were assessed by linear regression analyses. Results From 88 data sets the overall net change of VA was -0.10 +/- 0.12 logMAR (mean +/- standard deviation), being -0.13 +/- 0.11 logMAR for IVB, 0 +/- 0.08 logMAR for IVR and -0.12 +/- 0.08 logMAR for IVTA as compared to 0.01 +/- 0.14 logMAR for LPT. For CMT, the overall net change was -103 +/- 71 microns, being -108 +/- 64 microns for IVB, -182 +/- 73 microns for IVR, and -102 +/- 57 microns for IVTA and was -49 +/- 60 microns for LPT. Overall, modest correlations were found between the absolute central retinal (macular) thickness change and the VA change, and the relative changes in these measures (p < 0.001, r = 0.522 or 0.457). The predicted visual outcome from a 100 microns reduction in CMT was -0.083 logMAR units, an effect not substantially influenced by the CMT measurement method. Conclusions Pharmacological treatment of DMO can be expected to result in a predictable decrease in CMT with an accompanying increase in VA, with the overall outcome being better than laser treatment.