Choroidal Thickness and Its Correlations With Ocular Parameters in Primary Open-angle Glaucoma

Glaucoma is one of the leading causes of blindness worldwide that is a chronic public health problem. Unfortunately, glaucoma can be diagnosed when the disease reaches a certain level in today's conditions. The aim of this study was to investigate the diagnostic methods that can diagnose glaucoma before it reaches the advanced level and to identify pathophysiological processes. In this study, choroidal thickness was investigated in primary open-angle glaucoma cases and its correlations with OCT and multifocal ERG parameters were evaluated.

In this study, patients with primary open-angle glaucoma who have recently received a new diagnosis with healthy volunteers with age-matched groups were enrolled. All data from 49 glaucoma patients and 47 healthy volunteers were recorded and the study was completed. The study was carried out at the Afyon Kocatepe University Ophthalmology Department between January 2014 and April 2015. Routine ophthalmologic examinations of all participants were performed. Medical treatment was initiated on patients diagnosed with primary open-angle glaucoma. Intraocular pressures and visual acuities of all participants were recorded at baseline, at 1-month, at 3-month, and at 6-month. All participants underwent tests of multifocal electroretinography and the measurements of optic nerve head optical coherence tomography parameters and the choroidal thickness, at the same follow-ups. Visual acuities were measured by using the Snellen chart as the best corrected visual acuity. Intraocular pressures were measured by using applanation tonometry. Choroid thicknesses were also measured and recorded using EDI-OCT mode of optical coherence tomography device (Cirrus HD 4000, Carl Zeiss Meditec AG, Germany). Choroidal thicknesses were measured in three regions: fovea, 3mm nasal and temporal distances of the fovea. The mean of these three measurements was recorded as macular choroidal thickness. The same technician performed all multifocal electroretinography tests of the participants (Metrovision Monpack 3, Metrovision, France). Multifocal electroretinography tests were carried out from a distance of 33 cm using ERG-jet electrode, ground electrode, and a reference electrode. Electrical potential responses from 103 retina regions were recorded. Results were compared statistically and correlations were analyzed (SPSS 20.0, SPSS Inc. IL, USA).

Eligibility Criteria:
Inclusion Criteria for the glaucoma group:

* the best corrected visual acuity (BCVA) of 0.6 and above
* Intraocular pressure being above 21 mmHg
* Detection of open-angle by gonioscopy
* Detection of glaucomatous optic disc pitting by fundus examination
* Visual field defect in perimetry (Carl Zeiss Meditec AG, Germany)

Exclusion Criteria for the glaucoma group:

* A secondary cause of glaucoma
* Angle-closure in gonioscopic examination
* Corneal opacity or cataract at the level that may affect imaging, vitreous pathology
* Intravitreal hemorrhage that may affect fundus appearance, retinal pathology
* Chorioretinopathy, optic neuropathy, optic disc pathology, spherical refractive error of 6D and above, cylindrical refraction error of 3D and above and systemic diseases which may affect ocular blood flow

Inclusion Criteria for the healthy group:

* The best corrected visual acuity (BCVA) of 0.8 and above

Exclusion Criteria for the healthy group:

* Presence of systemic disease that may affect choroid blood flow
* Ocular conditions that may affect test measurements