We also compared the 2 groups with respect to change from baseline to 24 months in functional variables ( Humphrey photopic visual field testing using the Swedish interactive thresholding algorithm 24-2 strategy , contrast sensitivity , dark adaptation , visual acuity , and quality of life ) and anatomical variables ( diabetic retinopathy severity level , area of retinal thickening , central subfield thickness on optical coherence tomography , and macular volume on optical coherence tomography ) .