Microperimetry can allow for accurate spatial characterization of visual function providing insightful information about disease severity and progression not reflected by BCVA in a large range of disorders both in clinical practice as well as research. The usefulness of microperimetry in evaluating retinal sensitivity of macular region is well known in CSC. Ojima et al examined macular sensitivity with resolved CSC using Microperimeter-1 (MP-1) and found that eyes of resolved CSC with reduced retinal function at focal affected areas, which were consistent with irregularity of the RPE or with defects of the outer retinal layers. Roisman and colleagues  investigated the relationship between retinal sensitivity and persistence of subretinal fluid in acute CSC by MAIA microperimetry and suggested microperimetry with a cutoff of 20 dB may be a useful test to predict the persistence of subretinal fluid. A study by Parodi et al compared retinal sensitivity obtained with MP1 and MAIA microperimeters in patients affected by retinal dystrophies and in healthy subjects, and the results showed the MAIA microperimeter was more suited to precisely characterizing scotomatous areas with low sensitivity for it had a broader range of retinal light thresholds to be detected than the MP-1. The MP-3 device, which is the successor to the MP-1, is the latest generation of microperimetry and features faster tracking, increased automation and a better structure-function relationship. Interestingly, Balasubramanian et al compared and correlated the retinal sensitivity measurements obtained with MP-3 and MAIA microperimeters among healthy subjects, and as a result, the retinal sensitivity measures higher, but luminance and contrast sensitivity measure lower for MAIA-generated values compared with the MP-3, however, the relationships appeared fairly consistent and application of a standard correction factor allowed the data to be inter-related. To date, there is still a lack of standardization for testing (test-pattern, staircase strategy, adaptation, pupil dilatation), criteria for test repetition as well as reporting standards.
In this current study, MP-3 measurement was carried out using 4–2 full-threshold staircase strategy with the standard Goldmann III stimulus size, similar to previous studies[13, 14], and we found that macular sensitivities were significantly lower in recurrent CSC than in acute disease. Although acute episodes are usually self-resolving,15% to 50% of affected eyes may later present recurrence in follow-up varied from 2 to 13 years. The initial BCVA did not differ between recurrent and nonrecurrent cases, but the final BCVA was near-significantly worse in recurrent than nonrecurrent cases. It is plausible that the number of recurrent episodes correlates with visual outcomes in CSC, for repeated episodes and prolonged serous detachment lead to irreversible photoreceptor/RPE damage, and vision loss[2, 16]. Male sex, age, and sleep disorders are risk factors for recurrent or persistent CSC in the natural history. The subfoveal choroidal thickness, nonintense fluorescein leakage at baseline, and history of shift work are independent predictors of CSC recurrence. Microperimetry may be a useful test to predict the persistence of subretinal fluid, allowing the ophthalmologist to use treatment tools earlier, preventing extracellular damage and visual impairment. Although acute CSC usually resolves spontaneously without no long-term subjective symptoms in most cases, some visual sequelae may persist after the resolution of SRD, such as decreased retinal sensitivity. With the automatic tracking system for the retina, the MP-3 microperimeter can project target lights to the retina directly, so even when there is an eye movement, they still stimulate an intended identical retinal location. Recently, Fujita et al demonstrated retinal sensitivity measured using the MP-3 microperimeter was significantly correlated to the integrity of ellipsoid zone in resolved CSC. The information of microperimetry may contribute to identify CSC patients at higher risk of recurrence, who could benefit from the most suitable treatment at optimal timing for intervention.
This current study has several limitations. Firstly, the study design was retrospective. Secondly, the sample size was small. Thirdly, the longitudinal follow-up was absent. Finally, there was not the correlation with microperimetry alterations and angiography findings. However, our findings do suggest that recurrent CSC often show worse retinal function in focal affected macular areas than acute disease. This microperimetry information can help doctors to provide an early treatment if necessary to reduce the chance of permanent vision impairment and disease chronicity. Due to the continuous progress in the field of microperimetry, it is believed that the robust tool has great potential for prediction, early detection and treatment-monitoring of macular diseases.