Previous studies have shown that patients with diabetic macular edema (DME) with relatively good visual acuity can have slow reading speed. The aim of this study was to evaluate the structural–functional correlation in a cohort of patients with DME and to assess whether the central four retinal points on microperimetry (MP4) could be used as a potentially faster and more reliable method of assessing retinal function in patients with DME than reading speed.Methods:
The study was performed on patients with clinically significant DME. The best-corrected visual acuity (BCVA) was recorded with letter counting on a modified ETDRS chart, the maximal reading speed (MRS) was recorded with MNREAD, the retinal sensitivity (MP28 and MP4) was measured with Optos OCT/ Scanning Laser Ophthalmoscopy and the central subfield thickness was measured by Heidelberg Spectralis Spectral Domain Optical Coherent Topography.Results:
Of 100 eyes analyzed, 76 eyes were included in the study. The mean BCVA was 76.5 letters (Snellen equivalent 6/18), the mean MRS was 156.8 words per minute, the mean MP4 was 9.81 dB per point, and the mean central subfield thickness was 309.3 microns. It was found that faster MRS is correlated with younger age (P = 0.001), better BCVA (P < 0.0001), and better retinal sensitivity (P < 0.0001) for both MP28 and MP4, but not with central subfield thickness (P = 0.66). Central subfield thickness is correlated with MP28 (P = 0.05) but not with age (P = 0.812), BCVA (P = 0.113), or MP4 (P = 0.485). After correction for age and BCVA, MRS is still correlated with MP28 (P = 0.001) and MP4 (P = 0.015).Conclusion:
Patients with DME can have reduced reading speed despite good visual acuity. Maximal reading speed is often reported to be difficult to perform, inconsistent, and affected by language and educational level. However, in this study, the authors found that the central MP4 points are quick and easy to test in most of the patients, and are highly correlated with MRS. Microperimetry might therefore represent a useful additional functional test that could be considered better than BCVA or reading speed in quantifying visual function in patients with DME.