Microperimetry Sensitivity Correlates to Structural Macular Changes in Adolescents with Achromatopsia Unlike Other Visual Function Tests

Abstract

Objectives: Achromatopsia (ACHM) is a rare autosomal, recessively inherited disease that is characterized by cone dysfunction, for which several gene therapies are currently on trial. The aim of this study was to find correlations between the morphological macular changes identified using optical coherence tomography (OCT) and some visual functional parameters. Visual acuity (VA), contrast sensitivity (CS), and macular sensitivity obtained by means of microperimetry were assessed. Methods: Adolescents with ACHM underwent macular microperimetry (S-MAIA device) in mesopic condition, macular OCT, best corrected visual acuity (BCVA), low luminance visual acuity (LLVA), near vision acuity (NVA), and CS measurement. Results: Eight patients (15 eyes) with ACHM were analyzed. The mean age was 17 ± 2.7 years, and genetic variants involved the CNGA3 gene (37.5%) and CNGB3 gene (62.5%). OCT staging significantly correlated with microperimetry sensitivity parameters, namely the sensitivity of the central foveal point (p = 0.0286) and of the first and second perifoveal rings (p = 0.0008 and p = 0.0014, respectively). No correlations were found between OCT staging and VA measurements, nor with CS value. Conclusions: Among the extensive evaluated visual function tests, only microperimetry sensitivity showed a correlation with morphological macular changes identified at OCT. Microperimetry sensitivity may thus represent a useful visual function tool in natural ACHM history studies considering the upcoming research on gene therapies for the treatment of ACHM.

Keywords: achromatopsia; best corrected visual acuity; cone dystrophy; contrast sensitivity; low luminance visual acuity; microperimetry; optical coherence tomography; retinal inherited disease.

Figure 1

(A) Microperimetry of the right eye of a patient with achromatopsia (ACHM) performed with the S-MAIA device (CenterVue Spa, Padova, Italy). A customized grid with 57 points centered on the fovea was used, with the following distribution: one central point; 8 points in a first ring at 1° from the center (R1); and 12 points in each of the other four rings localized, respectively, at 2° (R2), 4° (R3), 8° (R4), and 12° (R5) from the center. The sensitivity of the single tested points is expressed in decibel (dB), ranging from 0 to 36 dB, with the 0 dB stimulus of maximum intensity. Microperimetry color guide—red from 0 to 23 dB, yellow from 23 to 25 dB, and green from 25 to 36 dB. (B) Linear B-scan optical coherence tomography (OCT) of the same eye with stage 1, according to the OCT staging proposed by Greenberg et al. [11].