Ocular wavefront aberrations in acute central serous chorioretinopathy

Introduction: Central serous chorioretinopathy (CSCR) is a condition of choroidal and retinal pathologies that may affect vision, so we assessed vision by the ocular wavefront in the acute


Introduction
Central serous chorioretinopathy (CSCR) is an idiopathic condition with serous macular sensory retinal detachment from the pigmented epithelium.¹ The etiology and pathophysiology mechanisms of CSCR are not precisely discovered. It is suggested that malfunctioning of the choriocapillaris, choroidal hyper-permeability, and abnormal choroidal thickness are among its primary cuased, and retinal pigment epithelium (RPE) lesions and subretinal fluid accumulation are among its secondary causes.² CSCR is more common in males between 20 and 50 years with an annual incidence rate of 9.9-10 per 100,000 in men, which is 6-7 times more frequently than in women.³⁻⁵ Visual acuity might be diminishing because it might induce a hyperopic shift. Vision consists of two forms of visual acuity and visual quality. 6 Visual quality is the most influenced by optical quality. 7,8 Optical aberrations are mentioned as the deviation of the wavefront of light.
As the light travels through the eye, it is a reason for the decreased quality of the optical system in the pathway. Ocular aberrations are divided into lower and higherorder aberrations.⁹ Adjusting corneal topography with wavefront aberrometry, the I-Trace can isolate the internal aberrations, subtracting corneal from total aberrations of the eye,⁹ some studies have investigated the role of optical aberrations on vision in retinal pathologies.¹⁰⁻¹² This study aimed to assess the ocular wavefront changes in acute CSCR to find the visual quality differences between eyes. We tried to clarify subjective comprehension of visual disturbance to objective form. Exclusion criteria were dry eye, amblyopia, history of previous CSCR, significant refractive error difference between the affected eye, and healthy fellow eye (more than 1 Diopter), any other ocular pathology, and past ocular surgery. All Patients enrolled to study when corrected distance visual acuity (BCVA) of both eyes was equal to 1 decimal notation.
Unilateral CSCR cases that had inclusion criteria entered the study and were compared with their healthy contralateral eye. Their ocular examination, without and with pupillary dilation, was performed. Visual acuity was checked by Snellen chart. Diagnosis of CSCR was determined by spectral-domain optical coherence tomography (SD-OCT, SPECTRALIS® Tracking Laser Tomography software version 6.0.9 Heidelberg engineering). Central macular thickness and Central subfoveal fluid height were measured by manually adjusting outlines. Central macular thickness is the distance between the inner limiting membrane and the outer/inner segment junction, the basement membrane of RPE and Central sub-foveal fluid height is the vertical length from the innermost to the outermost of sub-foveal fluid ( Figure  1).¹³ all patients had gone under binocular corneal imaging by I-Trace-visual function analyzer. (VFA TOPCON software version 1.0, Tracey Technologies, Houston, TX), after full pupillary dilation (1% Tropicamide eye drops). Then aberrometry details were obtained at a scan size of 5.0 mm, 2-4 times by an examiner.
I-trace aberrometry uses the near-infrared light, by the reflection to the level of the RPE and calculates retinal point spread function (PSF) and wavefront aberration. More details on keratometry, autorefraction, pupil diameter, topography, and wavefront aberrations were measured on the same axis.¹¹ The corneal topography was computed using Placidodisk technology. Ray tracing principles were applicated to ocular wavefront measurement.¹⁴ , ¹⁵ When patients focused on a distant target measurements were performed with dilated pupils at a fixed entrance pupil scan size of 5.0 mm.
The cardinal clinical record was uncorrected distance visual acuity (UCDVA) and BCVA. Optical parameters of this study were spherical equivalent, total root means square, total lower-order aberration, total higher-order aberrations, defocus, astigmatism, secondary astigmatism, coma, spherical aberration, trefoil, Strehl ratio in point spread function (PSF), the average height in modulation transfer function (MTF), evaluated by the same I-Trace visual function analyzer.
Sixth-order Zernike polynomial decomposition was utilizing to measure total wavefront aberrations. Root mean square (RMS) error was calculated from PSF. The Total HO is the RMS of HO terms (Z₃-Z₆); the total RMS is the RMS of all 25 Zernike terms.
The optical quality of ocular media were checked in two planes: the pupil plane and the retinal plane. Pupil plane aberration defines the ocular optical properties in individual Zernike polynomials. The image plane measures the wavefront error in the retinal plane.¹⁶᾽¹⁷ Image quality in the image plane is divided into PSF for point objects and MTF. The Strehl ratio is a number 0 to 1. It defines as a ratio between the peak intensity of the PSF of a patient's eye, and the PSF of an ideal eye.¹⁶᾽¹⁷ The MTF is the modulus of the Fourier transform of the PSF, and the MTF of 1 describes a perfect eye¹⁶. Root mean square (RMS) error is the difference of the wavefront from an ideal plane wavefront¹⁸; and interprets wavefront error, but not directly visual performance.  Kolmogorov-Smirnov test was used to assess the normal distribution of data. Generalized estimation equations (GEE), were used to compare means between two groups. A P value of 0.05 or less was considered statistically significant. (Table 1)

Results
Twenty-one patients were enrolled in this study (16male, 5-female). The mean age of participants was 39.47 years (range 27 to 48 years). A total of 11-right and 10left eyes with CSCR and their contralateral healthy eyes were analyzed. The mean UCDVA in the CSCR eyes and the contralateral control eyes comparison showed a significant difference (P = 0.002). In all cases, both eyes BCVA were equal to 1 decimal notation ( Table 1). Analysis of macular OCT data of CSCR group represented macular average thickness in 1mm ETDRS circle diameter of 506.52 ± 159.22μm, central foveal thickness of 485.9 ± 165.12 μm and mean sub-foveal fluid height of 284.29 ± 165.42 μm.

Discussion
To improve the vision, the principal issue is to assess both visual acuity and optical quality.⁷ Some studies have shown that retinal changes affect the visual quality; which is influenced by aberration and scattering.²⁰ So it may be part of reduced vision in retinal disorders due to increased internal ocular aberration and scattering. The results of current study showes that CSCR reduces UCDVA, while a significant ocular wavefront change was not detected in acute CSCR.
Lee et al²⁰ used the Optical Quality Analysis System (OQAS) for changes in optical quality and intraocular scattering in central serous chorioretinopathy over 3-months. They showed that MTF decreased, while objective scattering index (OSI) meaningfully increased. They could not find statistically relevant with macular thickness and optical parameters, like our study.
Bessho et al¹¹ studied 82 eyes of 66 patients with macular disease and 85 eyes of 51 patients without retinal disease. Ray-Tracing scanned wavefront at two pupil sizes up to 6th order Zernike coefficient. Third-order aberrations in the macular disease group was statistically higher than control group in phakic eyes, and it was more obvious in the larger pupil. We also evaluated CSCR patients in the large pupil and phakic eyes, and there were no meaningful results of wavefront aberrations in CSCR eyes and fellow eyes.
Mihaltz et al achieved resut similar to the study by Bessho et alIn their prospective study, 33-eyes of patients with diabetic macular edema and 31-patients as a control group had been scanned by a ray-tracing wavefront device. Total and internal ocular aberrations were evaluated separately to find the source of the aberrations plan. There was a statistically significant difference between the two groups. They could not prove a statistically significant difference in Strehl ratio and HO root mean square between phakic and pseudophakic patients. The height of cystoid spaces had a significant relationship to the Strehl ratio and there was a significant relationship between the HO Strehl In the current study, we evaluated the optical quality including lower and higher-order aberrations. There wasn't a significant difference between the two groups in terms of lower and higher-order aberrations such as trefoil, coma, total HO, total LO, defocus, PSF, MTF, and total RMS.
Visual acuity in the CSCR group was significantly lower than the fellow eye. Astigmatism and spherical equivalent were not significantly different between groups. Significant UCDVA decrease without acceptable changes in the spherical equivalent of refractive errors and other aberrations suggests that more factors, for example, axial length difference had an impact on it. It may also be rationalized by the acute process of CSCR.
This study had several limitations. The sample size was small, and all of our patients were acute CSC, therefore chronic CSCR phase details and also treatment consequences were not evaluated. We recommend future studies with larger number of patients, including acute and chronic CSC and other types of macular diseases and deviding total aberrations to internal and corneal wavefront aberrations.

Conclusion
Central serous chorioretinopathy (CSCR) is a condition of choroidal and retinal pathologies that may affect vision. To easily understand vison features of CSCR patients we used objective materials of OCT and I Trace parameters, and we concluded that although CSCR reduced uncorrected visual acuity, it did not change total low and high order aberrations such as trefoil, coma, total HO, total LO, defocus, PSF, MTF, and total RMS while mean sub-foveal fluid height was even more than the half of central foveal thickness.