Abstract
Purpose: :
To establish the correlation between Visual Acuity (VA), Microperimetry (MP) and Retinal Thickness (RT) in patients with Macular Edema (ME) involving the foveal region (within the central 300µm).
Methods: :
Patients’ eyes with clinically significant diabetic macular edema (CSME) (n=12), and sub-clinical diabetic macular edema (n=12) underwent RT measurements (CIRRUS HD-OCT, Zeiss), VA assessment (BCVA using ETDRS scale) and Microperimetry (MP-1, Nidek).RT maps were created within the 300µm centered on the fovea. These maps consist of 10µm concentric rings divided in 4 quadrants, plus one central area of 50µm.A new perimetric strategy was created consisting of a grid of 1º diameter with 25 stimuli - stimuli size Goldmann III, to permit a comparison between the OCT maps and MP.RT values were compared with a control population and ME was correlated with VA and Microperimetry using Spearman correlation coefficient.
Results: :
The results showed a good and strong correlation between RT and both VA and MP (R= -0.829, p=0.001; R= -0.624, p=0.030, respectively) Data showed that when the thickness of the fovea increases, the VA and luminous sensitivity decreases.VA shows also a good correlation with MP (R= 0.799, p=0.002).With this type of retinal thickness maps, it is possible to isolate data from different areas in the central 300µm to correlate with VA. All eyes that present a mean RT <250µm (n=7) in the 4 quadrants showed a VA >80 letters, while the eyes presenting retinal edema in at least 3 quadrants with RT >250µm had a VA <77 letters. (p=0.001)
Conclusions: :
The new spectral domain OCT technique (CIRRUS HD-OCT) permits more detailed information on the thickness of the central region of the macula. High- Definition OCT, used in conjunction with VA and MP, shows good structure-function correlation even in cases of sub-clinical ME.
Keywords: edema • visual acuity • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)