Abstract
Purpose
To evaluate the effect of central serous chorioretinopathy (CSCR) on retinal function using dark adaptation in a human subject, and to follow it through resolution of the disease.
Patients
Single patient, 50 years old male patient, with acute CSCR in one eye and resolved old CSCR in the other eye.
Observations
Observational study in patient with CSCR followed through resolution of the subretinal fluid (52 days). Dark adaptation was assessed using the AdaptDx® (Maculogix Inc.) measured by Rod Intercept time (RIT) in minutes. A normal retinal locus of the same eye on the opposite side of the fovea was used as control. Retinal separation (microns) was measured using Spectralis Optical Coherence Tomography (Spectralis®, HRA + OCT, Heidelberg engineering). Change in time to dark adapt, were correlated with retinal separation measured in microns, during the course of CSCR.
The Rod Intercept time was delayed in the area of detached retina compared to the normal region (control) on presentation with retinal separation (RS) of 104 μm. The Rod Intercept time returned to normal as the retinal separation from retinal pigment epithelium decreased and eventually resolved.
Conclusions
This case shows that delay in dark adaptation is proportional to the amount of separation of neurosensory retina from retinal pigment epithelium in CSCR, this may offer a potential of using DA to characterize visual function in CSCR. The association of dark adaptation response with the state of retinal pigment epithelial function and its ability to predict the recurrence of CSCR needs further evaluation.
1
Introduction
Central serous chorioretinopathy (CSCR) is a retinal disorder characterized by serous retinal detachment with or without associated retinal pigment epithelial detachment (RPED). In most cases, the Snellen’s visual acuity is good in these patients and yet they are very symptomatic. CSCR is self-resolving; however recurrent and chronic episodes can cause decreased vision. In order to evaluate a more sensitive measure of visual function, we measured dark adaptation (DA) function in CSCR and correlated it with the separation of neurosensory retina from the retinal pigment epithelium (RPE). We found that Central Serous Chorioretinopathy leads to delayed dark adaptation, and that the proximity of the RPE and photoreceptor layer is important in dark adaptation.
2
Case report
A 50-year-old male patient, with past history of spontaneously resolved CSCR of the right eye (OD) 5 years back treated elsewhere for symptoms of mild visual distortion that resolved completely with 20/20 vision in a few weeks, presented to the Retina clinic with a three day history of noticing a round dim spot nasal to the center of vision, in his left eye (OS). Best corrected visual acuity (BCVA) was 20/20 OD and 20/25 OS, with pinhole (PH) improving to 20/20. Both eyes had normal intraocular pressure, with full confrontational visual fields and extra ocular movements. Slit lamp biomicroscopy of the anterior segment showed bilateral trace nuclear sclerosis, normal anterior chamber and vitreous. Bilateral fundus examination showed normal disc and vessels. The right macula was notable for pigment mottling with a single subretinal deposit. The left macula showed retinal elevation beginning at fovea and involving about two disc diameter circular area of temporal macula with an orange colored pigment epithelial detachment (PED).
Patient was examined and imaged about every 2 weeks until full recovery ( Fig. 1 ). The near infrared images with the optical coherence tomography (OCT) scans (Spectralis, Heidelberg Engineering. Heidelberg, Germany) were performed to measure height (in microns) of retinal separation (RS). Dark adaptation (DA) was measured periodically from the presentation to resolution of clinical signs ( Fig. 2 ) using the AdaptDx® (Maculogix, Middletown, PA) instrument, with rod-intercept time (RIT) in minutes as the DA parameter. Minimum of 30 minutes of pre-test adaptation to indoor room lighting is done in case of any immediate prior bright light exposure (e.g. Fundus photography or Autofluorescence imaging) to avoid any delaying effect on the test results. Measurements were taken in a dark room using the extended (20 minutes) protocol. Initial photo bleach exposure to a flash of 505-nm for 0.8-ms at an intensity of 1.8 × 104 scot cd/m2, equivalent to 76% bleaching level for rods was used. The flash of light passed through a square aperture sized to bleach a 6° area of the retina centered at 5° from the fovea on either side of the horizontal meridian, with the patient fixating on a light. The test target used was a 2° test stimulus light of 505 nm wavelength beginning 15 seconds after the bleaching flash. Patient was instructed to press a response button when first noticed the stimulus light and then the stimulus light intensity was gradually reduced till stimulus stops being perceived. Threshold was estimated using a 3-down/1-up modified staircase estimate procedure and continued at 30 seconds intervals till the recovery of visual sensitivity. The Rod Intercept, measured by the AdaptDx®, is the time in minutes at which the visual sensitivity recovery crosses three log units of recovery after initial bleaching, and is completely rod-mediated characterizing the visual sensitivity recovery rate, or dark adaptation speed. The machine has a central fixation target and stimulus locations at predefined eccentricities along vertical and horizontal meridian. We chose to measure at 5° eccentricity on horizontal meridian because it corresponded with the CSR spot on the retina. We obtained measurements at 5° horizontal from the fovea on either side as 5° location with 6° bleach area, and 2° spot size fell well within the CSCR location; the nasal visual field test corresponded with the area of CSCR located temporal to the fovea, while the temporal visual field test corresponding to the nasal to the fovea retinal location served as the control. DA testing spot was moved by changing the test location in the machine settings. The 5° from fovea superior or inferior location was avoided as control region since the area was very close to the CSCR region border, and considering the 6° bleach area, and 2° size of the test stimulus light, we wanted no overlap between the stimulus light location and the CSCR region in case the area of CSCR expanded after the first measurement. A single DA measurement was performed in the right eye on day 16 in the nasal visual field (region previously affected by CSCR temporal to the fovea) to measure the RIT in the eye with resolved CSCR. The test is designed in such a manner that the flash bleaches a localized predetermined area of retina with patient fixating on a fixation light, so sequential testing at different test spot on opposite side of the fovea would not affect the results. However, to avoid any probable effect, the DA testing in the CSCR and control locations on follow up visits was done by alternating the test sequence of the region tested first.
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