|Year : 2018 | Volume
| Issue : 2 | Page : 111-116
Correlation between peripapillary choroidal thickness and nerve fiber layer thickness in primary open-angle glaucoma
Haitham Y Al-Nashar, Ahmad M.B Awad
Department of Ophthalmology, Faculty of Medicine, Zagazig University, Zagazig, Egypt
|Date of Submission||06-Oct-2017|
|Date of Acceptance||11-Dec-2017|
|Date of Web Publication||7-Jun-2018|
Haitham Y Al-Nashar
Department of Ophthalmology, Faculty of Medicine, Zagazig University, Zagazig 44519
Source of Support: None, Conflict of Interest: None
Purpose The purpose of this study was to evaluate the peripapillary choroidal thickness (PPCT) and its correlation with nerve fiber layer thickness (NFLT) in eyes with primary open-angle glaucoma (POAG).
Patients and methods Eighty eyes were included in this study. They were divided into two groups: group I (38 eyes) of normal individuals and group II (42 eyes) with POAG. All eyes underwent complete ophthalmic examination with visual field testing using Humphery visual field analyzer. NFLT was measured in all eyes using Heidelberg Spectralis-optical coherence tomography with a circle of 3.4-mm diameter around the optic disc. PPCT was measured using enhanced deep imaging (EDI) technique of Heidelberg Spectralis-optical coherence tomography.
Results The mean age was 51.74±4.27 years in group I and 53.7±3.7 years in group II. Global NFLT in group I was 103.6±6.3 μm and in group II it was 76.9±8.5 μm with a significant difference between the two groups (P<0.001). The global PPCT was 175.1±8.4 and 129.5±10.1 μm in group I and II, respectively, with a significant difference (P<0.001). The correlation between PPCT and NFLT in group I was 0.84 (P<0.001) and in group II it was 0.9 (P<0.001).
Conclusion The PPCT was decreased in eyes with POAG, and there was a significant correlation between it and NFLT in these eyes.
Keywords: choroidal thickness, enhanced deep imaging, nerve fiber layer thickness, optical coherence tomography, open-angle glaucoma
|How to cite this article:|
Al-Nashar HY, Awad AM. Correlation between peripapillary choroidal thickness and nerve fiber layer thickness in primary open-angle glaucoma. Delta J Ophthalmol 2018;19:111-6
|How to cite this URL:|
Al-Nashar HY, Awad AM. Correlation between peripapillary choroidal thickness and nerve fiber layer thickness in primary open-angle glaucoma. Delta J Ophthalmol [serial online] 2018 [cited 2018 Sep 20];19:111-6. Available from: http://www.djo.eg.net/text.asp?2018/19/2/111/233935
| Introduction|| |
Glaucoma is an optic neuropathy in which increased intraocular pressure (IOP) is a risk factor. Decreased nerve fiber layer thickness (NFLT) occurs in open-angle glaucoma (OAG) with permanent loss of vision owing to visual field loss ,.
Different mechanisms are involved in the pathogenesis of the nerve fiber layer; elevated IOP acts directly on the lamina cribrosa with subsequent loss of retinal nerve fiber layer (RNFL) . Compromised optic nerve blood perfusion plays an important role in the pathogenesis of OAG owing to changes in optic nerve microcirculation with subsequent ischemia and damage of nerve fiber layer ,.
Recent studies investigated the peripapillary retinal blood flow and detected that the retinal perfusion in the peripapillary area is impaired in eyes with OAG. They concluded that the vascular elements are essential in the pathogenesis and development of glaucomatous changes ,.
Peripapillary choroidal vasculature is essential for optic nerve head blood supply. As the choroidal blood vessels around the optic nerve head are the main blood supply to the nerve fiber layer in this area, any choroidal blood flow impairment may affect the nerve fiber layer with subsequent damage and decreased thickness ,.
RNFL thickness can be measured and evaluated by using optical coherence tomography (OCT). With the development of the spectral domain-OCT (SD-OCT), the resolution and accuracy of RNFL thickness measurement were increased . However, the evaluation of the choroid is difficult as it lies under the retinal pigment epithelium, which may interfere with the good imaging of the choroid. The development of enhanced depth imaging (EDI) technique in SD-OCT made the examination of choroid with measurement of its thickness possible ,.
The aim of this study was to find whether there was a correlation between the NFLT and the peripapillary choroidal thickness (PPCT) in patients with primary open-angle glaucoma (POAG).
| Patients and methods|| |
Eighty eyes were included in this prospective study. They were divided into two groups; group I included 38 eyes of 19 normal individuals (normal group) and group II included 42 eyes of 25 patients diagnosed with POAG (OAG group).
All individuals who participated in this study were in the age group of 40–60 years. Eyes that were diagnosed as POAG were included in this study. OAG was diagnosed in patients when IOP greater than or equal to 22 mm Hg, with the presence of open-angle and visual field changes and defect in RNFL thickness.
Individuals with age more than 60 years or less than 40 years or with refractive errors greater than ±6D were excluded from the study. Eyes with any ocular disease other than POAG (such as different retinopathies or any inflammatory disorders) were excluded from the study. Eyes with previous ocular surgery or intravitreal injection were also excluded from the study.
A full routine eye examination was done for all individuals participating in the study, including measurement of best corrected visual acuity, cycloplegic refraction, IOP measurement (using Goldman applanation tonometer), gonioscopy, slit-lamp examination, posterior segment examination, and visual field examination (Humphery Visual Field Analyzer, Carl Zeiss, Jena GmbH, Germany).
Optical coherence tomography examination
All SD-OCT examinations were performed by Heidelberg Spectralis-OCT (Heidelberg Engineering, Heidelberg, Germany). NFLT was measured using a circle of 3.4 mm diameter, which was centered on the optic disc. PPCT was measured using EDI techniques. With the same 3.4-mm circle, the OCT instrument was moved closer to the eye than the usual; therefore, the sensitivity of deep tissue layers imaging was increased.
Both NFLT and PPCT were done at seven locations around the optic disc (temporal, nasal, inferotemporal, inferonasal, superotemporal, superonasal, and global thickness).
All patients gave an informed consent and the study was approved by the Institutional Review Board and was conducted in accordance with the Declaration of Helsinki and the principles of Good Clinical Practice. The collected data were analyzed statistically using SPSS (IBM SPSS statistics 14.0; IBM, Chicago, Illinois, USA). A P value less than 0.05 was considered statistically significant.
| Results|| |
The mean age was 51.74±4.27 years in group I and 53.7±3.7 years in group II (P=0.14). No significant difference was found between the two groups in spherical equivalent and best corrected visual acuity (P=0.7 and 0.15, respectively). The mean IOP was 14.4±1.2 mmHg in the group of normal individuals and was 15.5±6.6 mmHg in the group of glaucomatous patients with no significant difference (as most of these patients in group II were controlled by medical treatment). The mean deviation (MD) was measured by visual field analysis, and there was a significant difference between both groups. These data are illustrated in [Table 1].
RNFLT was measured in both groups using SD-OCT. NFLT was evaluated in six positions in a circle of 3.4 mm around the optic nerve head with estimation of the global thickness ([Figure 1] and [Figure 2]).
|Figure 1 Normal individual (from group I). (a) Nerve fiber layer thickness measurement in 3.4 mm around the optic nerve head using spectral domain-optical coherence tomography. (b) Peripapillary choroidal thickness measurement in 3.4 mm around the optic nerve head using enhanced deep imaging technique of spectral domain-optical coherence tomography.|
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|Figure 2 Glaucomatous patient (from group II). (a) Nerve fiber layer thickness measurement in 3.4 mm around the optic nerve head using spectral domain-optical coherence tomography. (b) Peripapillary choroidal thickness measurement in 3.4 mm around the optic nerve head using enhanced deep imaging technique of spectral domain-optical coherence tomography.|
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There was a significant difference between the normal and glaucomatous groups in the thickness of nerve fiber layer measured in all positions around the optic nerve. In addition, with measurement of PPCT, a significant difference was found between the two groups in all positions around the optic nerve ([Table 2] and [Table 3], [Figure 3] and [Figure 4]).
|Table 3 Peripapillary choroidal thickness measurements (in μm) in both groups|
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|Figure 3 Nerve fiber layer thickness measured using spectral domain-optical coherence tomography in normal and glaucomatous individuals. T, temporal; N, nasal; ST, superotemporal; SN, superonasal; IT, inferotemporal; IN, inferonasal; G, global.|
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|Figure 4 Peripapillary choroidal thickness measured using enhanced deep imaging technique of spectral domain-optical coherence tomography in normal and glaucomatous individuals. T, temporal; N, nasal; ST, superotemporal; SN, superonasal; IT, inferotemporal; IN, inferonasal; G, global.|
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The correlation between the NFLT and PPCT was evaluated in the normal individuals group, and a significant correlation was found in all positions except in the superotemporal and inferonasal parts where the correlation was not significant. In group II (glaucomatous patients), a significant correlation between NFLT and PPCT was found in all parts around the optic nerve, except the superonasal and inferotemporal parts. A positive correlation was found between global NFLT and global PPCT in both normal and glaucomatous individuals (r was 0.84 and 0.9, respectively). These data were presented in [Table 4].
|Table 4 The correlation between nerve fiber layer thickness and peripapillary choroidal thickness in normal and glaucomatous groups|
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| Discussion|| |
POAG is an optic neuropathy in which IOP is a risk factor. It is characterized by progressive degeneration of retinal nerve fiber layer producing specific pattern of optic disc cupping and visual field loss with irreversible loss of vision ,.
The pathogenesis of the optic neuropathy in glaucomatous eyes has a vascular origin, and it is mainly due to insufficient blood perfusion to the optic nerve head secondary to increased IOP . The main source of blood supply to the anterior laminar and prelaminar areas of optic nerve comes from the choroidal blood vessels. Therefore, the abnormality in choroidal blood circulation may have a role in the development of optic neuropathy in glaucomatous eyes ,. However, the role of the choroid in the development of OAG is still unclear. Many studies showed that there was a relation between decreased choroidal circulation and development of OAG owing to impaired blood supply to the optic nerve head. Thus, the evaluation of PPCT in eyes with OAG may play a role in understanding glaucoma pathogenesis ,,.
In this study, the PPCT was measured in 80 eyes (38 normal eyes and 42 eyes with POAG) using the EDI technique of OCT to investigate whether POAG is associated with a change in PPCT.
The choroidal thickness is affected by age, axial length, and refractive error . Therefore, all individuals participating in this study were selected to be from the same age group and with an error of refraction less than or equal to 6 D.
The results of this study showed that there was a significant difference between the normal and glaucomatous groups in the PPCT. In addition, there was a correlation between the PPCT and NFLT in glaucomatous eyes. These results mean that the decrease in NFLT in glaucomatous eyes was associated with a decrease in PPCT.
Wang et al.  evaluated the variation in perfusion of optic nerve head in glaucomatous eyes using optical coherence tomography angiography (OCT-angio). They found that the blood flow to the optic disc was reduced in eyes with glaucoma, which is correlated with the thickness of the ganglion cell layer. Sullivan-Mee et al.  evaluated the juxtapapillary choroidal volume in eyes with POAG, ocular hypertension, and in normal eyes. Their results showed that there was a significant reduction in choroidal volume in eyes with POAG. Lee et al.  used swept-source OCT to measure the juxtapapillary choroidal thickness in eyes with normal-tension glaucoma (NTG) and in normal eyes. Their results showed that there was a decrease in the juxtapapillary choroidal thickness in eyes with NTG in the temporal part of the optic nerve. They concluded that the decrease in optic nerve head circulation is due to thinning of the juxtapapillary choroid, and this may be an important factor in the pathogenesis of NTG.
The results of these studies are similar to those of the current study. The decrease in PPCT in glaucomatous eyes is explained by the increased IOP in these eyes, which will be harmful for the NFL with associated affection of the peripapillary choroidal blood vessels and subsequent decreased choroidal vasculature in the area around the optic nerve. One of the theories in glaucomatous optic neuropathy is that structural damage leading to functional deficit is the result of impaired choroidal blood flow to the optic nerve head ,.
However, another study concluded that there was no change in PPCT in glaucomatous eyes with no correlation between it and NFLT. Li et al.  used EDI-OCT to investigate the PPCT in eyes with POAG in comparison with normal eyes. They concluded that there was no significant difference in PPCT between eyes with POAG and normal eyes.
Mwanza et al.  used EDI-OCT to measure the choroidal thickness in eyes with advanced glaucoma and compared them with the fellow eye with no or minimal glaucoma. They measured the choroidal thickness at nasal and temporal parts and at the sub-foveal area. They found that there was a significant difference in choroidal thickness between eyes with advanced glaucoma and those with minimal or nonglaucomatous changes. They concluded that there was no relation between choroidal thickness and OAG. These results differ from the results of the present study. This difference may be owing to the fact that Mwanza et al.  compared severe glaucomatous eyes with minimally affected eyes. In addition, they measured sub-foveal choroidal thickness with temporal and nasal halves only, whereas in the present study we compared glaucomatous with normal eyes, and the PPCT was measured in all quadrants around the optic nerve (six locations with global measurement).
The controversies between the different studies may be owing to the fact that the available OCT devices do not have automated segmentation for the choroid, making manual calculations subjective to the operator’s variation. Therefore, automated segmentation program for the choroid is highly needed and recommended as the choroid plays an important role in many of the retinal and optic nerve diseases.
In conclusion, this study showed that PPCT was decreased in eyes with POAG and there was a correlation between PPCT and NFLT in these eyes.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]