Dr. Sarang Lambat, L12235, Dr. Priyanka Pardhi, Dr. Tuhina Kunwar, Dr. Nangia Vinay Kumar B
Introduction:
The choroid is primarily or secondarily involved in the pathogenesis of many diseases of the posterior segment of the eye, such as age-related macular degeneration, polypoidal choroidal vasculopathy, central serous chorioretinopathy, and myopic retinopathy. Microscopic details of the choroid have been known since many years, but these were done in autopsy eyes. Because of its localization between the overlying pigmented RPE and the underlying opaque and rigid fibrous sclera, the choroid is difficult to visualise. Methods using light reflection or fluorescence generation are impeded by the pigment in the RPE and choroid. Conventional optical coherence tomography (OCT) is affected by the effects of melanin and also the scattering properties of the blood and blood vessels, and lesser wavelength of light used for imaging leading to lesser penetration beyond the RPE. Use of new OCT modalities, including enhanced depth imaging OCT, image averaging, and swept-source OCT, have led to increased visualisation of the choroid.
Enhanced-depth imaging optical coherence tomography (EDI OCT) technologies permit deeper penetration through RPE and a better visualization of the choroid. Studies in healthy individuals and in patients with age-related macular degeneration (AMD), central serous chorioretinopathy (CSC), high myopia, and glaucoma that investigated the choroidal thickness were performed by using EDI OCT technologies. Thusthe choroid is an important vascular layer and may have significant implications in retinal diseases. It was the purpose to study the foveal choroidal thickness (FCT) in a cohort of myopic eyes and to determine their correlations.
Methods:
Prior approval from the Institutional Review Board of the institute was taken, and informed consent was obtained from each subject. This study was conducted in accordance with the tenets of the Declaration of Helsinki. Myopic patients reporting to our outpatient department who gave consent for participation in the study were included. Patients having obvious macular pathology were excluded. Finally 230 eyes of 115 subjects were enrolled for the study.
All participants underwent a comprehensive ophthalmic examination including visual acuity testing using, slit‑lamp biomicroscopy, intraocular pressure measurement using Goldmannapplanation tonometer and dilated funduscopic examination. AXL measurement was performed usingocular biometry (IOL Master; Carl Zeiss Meditec, Jena, Germany).
Refraction, axial length (AXL) measurement, anterior chamber, and fundus examinations were performed. OCT was done on Spectral Domain OCT machine (Spectralis, Heidelberg Engineering, Germany). Macular line scans, Detailed scans, RNFL scans and Enhanced Depth Imaging of the choroid was done for all the patients. All the scans were analysed by 2 Retina Experts for checking proper assessment of measurements and quality of scans. All the data was entered in SPSS version 19 for analysis. P value of less than 0.05 was considered to be significant
Results:
Of the 115 patients 47.8 percent were males. The mean age was 26.28+-11.038 years (Range 8-60 years). The spherical equivalent was -6.15+-3.9 diopters (Range -20.0 – -0.50) and the mean axial length was 25.69+-1.89 mm(Range 22-35.57). The mean VA in Decimal units was 0.77+-0.27. The mean anterior chamber depth was 3.7036 +- 0.31381 mm and the mean intraocular pressure was 15.20+- 2.659 mmHg.
The FCT was 262.71 +- 105.7 u. It was significantly negatively correlated with age (P=0.001,r=-0.239), with female gender (P =0.005;r=0.198), it decreases with increasing axial length (P<0.001,r= -0.581) and increases with better visual acuity (P<0.001, r=0.478).
It did not correlate with the anterior chamber depth, Intraocular pressure, and disc area.
Conclusions:
The FCT was maximum at the fovea and it reduced as we go away from the fovea towards the temporal and nasal side. Macula having a high vascular needs, we expected FCT to be thicker at the fovea even in Myopic patients. The FCT was significantly affected by age, and with increasing axial length. It has a significant correlation also with the visual acuity. Increasing age and axial length have a direct impact on reduction in the thickness of the choroid hence making them important parameters while assessing choroid in these patients.