Abstract
Purpose :
Humphrey perimetry (HP) is the most widely used functional test for hydroxychloroquine toxicity screening. Microperimetry (MP) is an alternative that tests macular sensitivity and correlates functional deficits with anatomical location and has the advantage of fixation tracking. In this prospective study, we compared Humphrey 10-2 perimetry and microperimetry in normal subjects and those on hydroxychloroquine (HCQ) therapy to assess their relative sensitivity.
Methods :
Patients on chronic HCQ therapy for an autoimmune condition and normal subjects were included in this study. HP (Zeiss HFA) and MP (CenterVue MAIA) were performed in the same visit. Tests with poor reliability (greater than 10% fixation loss, false positives or negatives) and poor fixation stability were excluded. Normal HP was defined as zero depressions on the pattern deviation map. Normal MP was defined as normal sensitivity at all test points (compared to normative data provided by the manufacturer: average threshold greater than 26 dB and percent reduced thresholds less than 8%).
Results :
A total of 4 normal subjects (8 eyes) and 11 subjects on HCQ (22 eyes) were enrolled. One eye from a normal subject and 4 eyes of 3 HCQ subjects were excluded from analysis due to unreliable testing (3 eyes with poor HP reliability and 2 eyes with poor HP reliability and poor MP fixation). Qualitative analysis was carried out on 14 subjects (25 eyes). Among 7 eyes (4 subjects) studied in the normal group, only 4 eyes were normal in both HP and MP. Among 18 eyes (10 subjects) tested in the HCQ group, 5 eyes (27.8%) showed abnormality on HP only, 8 eyes (44.4%) showed abnormality on HP and MP, and 5 (27.8%) showed no abnormality with either method. Four eyes (2 subjects) were diagnosed with toxic maculopathy based on concurrent abnormality on OCT or mfERG. Among these 4 eyes diagnosed with toxic maculopathy, 3 eyes had both abnormal HP and MP and 1 eye had abnormal HP and normal MP.
Conclusions :
In this small pilot exploratory study, we note that MP with fixation tracking may provide a more reliable method of testing macular function. However, results on HP and MP may not be interchangeable as abnormalities noted with one method were not always reproduced with the other method. Further study with a larger sample is needed to determine the relative sensitivity and specificity of HP versus MP in diagnosing toxic maculopathy secondary to HCQ use.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.