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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 4  |  Page : 1213-1217

The effect of changes in intraocular pressure on choroidal thickness by optical coherence tomography


1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Ophthalmology, Ophthalmology Hospital, Menoufia University, Menoufia, Egypt

Date of Submission14-May-2020
Date of Decision06-Jun-2020
Date of Acceptance15-Jun-2020
Date of Web Publication24-Dec-2020

Correspondence Address:
Shymaa F Saad
MBBCh, Shebin El-Kom, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_161_20

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  Abstract 


Objective
The aim was to compare the choroid thickness (CT) in eyes with newly discovered glaucoma with the eyes of healthy controls.
Background
Glaucoma is characterized by progressive damage to retinal ganglion cells, leading to optic nerve head morphological changes, thinning of the retinal nerve fiber layer (RNFL), and loss of visual field.
Materials and methods
A total of 100 patients (100 eyes) with newly discovered glaucoma and 50 age-matched normal participants underwent macular CT scanning using enhanced-depth imaging-optical coherence tomography (EDI-OCT). The average subfoveal choroid thickness (SFCT) of the glaucoma eyes was compared with that of normal eyes.
Results
The CT, RNFL, and intraocular pressure (IOP) were found to have significant changes between glaucomatous and normal eyes. The mean CT under the fovea (SFCT) was 277.3 ± 37.78 μm in the glaucomatous eyes, which was found to be thicker than in normal eyes (259.8 ± 24.92 μm) (P < 0.05). Mean RNFL was thinner in glaucomatous eyes (91.39 ± 12.47) than in normal eyes (110.9 ± 7.40) (P < 0.05). Mean IOP was 26.16 ± 3.0 in glaucomatous eyes and 19.50 ± 2.59 in normal eyes. The correlation between IOP and both RNFL and CT was not significant, with P = 0.825 and 0.230, respectively.
Conclusion
The CT is higher in patients with glaucoma than in normal group based on EDI-OCT measurements.

Keywords: choroid thickness, enhanced-depth image-optical coherence tomography, glaucoma, intraocular pressure, retinal


How to cite this article:
Nassar MK, Ibrahim AM, Saad SF. The effect of changes in intraocular pressure on choroidal thickness by optical coherence tomography. Menoufia Med J 2020;33:1213-7

How to cite this URL:
Nassar MK, Ibrahim AM, Saad SF. The effect of changes in intraocular pressure on choroidal thickness by optical coherence tomography. Menoufia Med J [serial online] 2020 [cited 2021 Apr 19];33:1213-7. Available from: http://www.mmj.eg.net/text.asp?2020/33/4/1213/304486




  Introduction Top


Glaucoma is characterized by progressive damage to retinal ganglion cells, leading to optic nerve head (ONH) morphological changes, thinning of the retinal nerve fiber layer (RNFL), and loss of visual field. The underlying mechanism of damage is incompletely understood but is likely multifactorial. Raised intraocular pressure (IOP) is a major risk factor. It also has been proposed that the microcirculation and vascular perfusion can contribute to the health of the optic nerve. As choroid drive vasculature perfuse the ONH, there is interest in the role of the choroid in the pathogenesis of glaucoma[1].

Glaucoma is associated with changes in the deep retinal layers and the choroid. The deep retinal layers and the choroid may be of interest for the diagnosis of glaucoma, as deep retinal changes show different pattern in the psychophysical examination such as perimeter and color vision testing. Also glaucoma-related changes in the deep retinal layers and the choroid could be visualized and analyzed by ocular coherent tomography (OCT)[2].

It is now possible to obtain in-vivo images of the choroid using enhanced-depth imaging optical coherence tomography (EDI-OCT), a modified version of spectral domain OCT (SD-OCT). Enhanced-depth imaging has been used to examine macular choroid thickness (CT) in healthy and glaucomatous eyes, and as enhanced-depth imaging allows visualization of the choroid, the assessment of CT has often relied on manual measurements at localized points to detect the difference in CT in healthy and glaucomatous eyes[3].

The aim of this work was to compare the CT in eyes with newly discovered glaucoma and the eyes of healthy controls in an attempt to study the effect of changes in IOP between glaucoma and normal persons on the CT to see if we can depend on it for diagnosis and follow-up of glaucoma.

We used EDI-OCT as an accurate method for measuring the CT.


  Materials and methods Top


This prospective observational study involved 100 patients with glaucoma and 53 healthy participants. The study was done at Shebin El-Kom, Teaching Hospital, Shebin El-kom, Menoufia, in the period from May 2019 to March 2020.

Before the beginning of the study and in accordance with the local regulations, the protocol and all corresponding documents were declared for ethical purposes and were approved by the Ophthalmology Department, Menoufia University.

CT was measured with spectral domain optical coherence tomography (SD-OCT) enhanced-depth image. CT was obtained at subfoveal area. IOP with applanation tonometry, RNFL thickness with OCT, and cup/disc ratio (C/D ratio) with slit lamp 90 volk lens were measured.

Inclusion criteria

Patients with age between 15 and 75 years, including both sexes, with clear media, and nonocular or systemic diseases were included. The normal control group had an IOP less than 22 mmHg, no history of increased IOP, normal disc appearance, and a normal visual field. Absence of the glaucomatous disc appearance was characterized as an intact neuroretinal rim without cupping, notches, or localized pallor. The glaucoma group had IOP greater than 22 mmHg, glaucomatous field defect; glaucomatous disc changes such as cupping, pallor, and disc hemorrhage; and nasal shifting.

Exclusion criteria

The following were the exclusion criteria: old patients with glaucoma on medical treatment; eyes with previous laser or surgical treatment; corneal conditions; lens; vitreous opacities that prevent optic nerve and choroid structure examination; history or diagnosis of ischemic optic neuropathy, vascular occlusive diseases, or other permanent neurological disease; diabetic retinopathy; uveitis or other retinal diseases; media opacities such as cataract; patients taking intravitreal steroids or antiantigenic drugs for treatment of any retinal problem; and refractive error more than 3D.

Each participant underwent full ophthalmoscopic examination, including best-corrected visual acuity examined by Snellen chart after correction of all other visual problems as refractive errors then converted to logMAR in all participants; anterior segment examination for depth, clarity, pupil size. and reaction; angle of anterior chamber size by gonioscopy; IOP (Goldman applanation tonometry); 90 D lens fundoscopy to examine disc and rim size and Haag-Streit UK Edinburgh Way Harlow Essex CM20 2TT shape; and spectral-domain optical coherent tomography scans.

Examination of patients

All patients were examined with Spectralis spectral domain optical coherence tomography (Heidelberg Engineering, Heidelberg, Germany) (Spectralis software Version 4.0) after pupillodilation with tropicamide 1%.

Measurement of choroid thickness

Macular line raster scan was used to evaluate the CT. It enables good quality depth penetration with so averaged B scans. The CT was measured as the perpendicular distance between hyper refractive outer border of the retinal pigment epithelium brush membrane layer automatically detected by SD-OCT device and the sclera-choroid interface manually drawn by two experiences examiners. The CT was measured at the subfoveal area.

Optical coherence tomography (OCT) is a noninvasive technique for cross-sectional tissue imaging. It typically uses light in the near-infrared spectral range which has a penetration depth of several hundred microns in tissue. The backscattered light is measured with an interferometry setup to reconstruct the depth profile of the sample at the selected location. A scanning OCT beam allows for acquisition of cross-sectional images of the tissue structure. To prepare for examination, we put pupillodilation with tropicamide 1% to the case and then take the scans for the choroid[4].

Statistical analysis

All data were analyzed with statistical analysis software (SPSS, version 18; SPSS Inc., Chicago, Illinois, USA). Difference in thickness values between groups were analyzed for statistical significance with one-way analysis of variance. Univariate and multivariate linear regressions were used to assess the relation between CT and age, IOP, sex, RNFL, best-corrected visual acuity as logMAR, diagnostic group (normal, newly discovered glaucoma). Specifically, these variables were initially fitted in a univariate model and then entered in a multivariate analysis to determine independence of effects. Mean CT was regressed against age to verify the hypothesis that choroid RNFL thickness varies as a function of age. Intraobserver and introbserver agreements were evaluated with interclass correlation coefficient and Pearson's correlation coefficient, respectively. For all analyses, P less than0.05 was considered statically significant.


  Results Top


The study was conducted on 150 eyes of 67 male and 73 female persons with age range from 15 to 75 years old. A total of 100 participants were newly discovered glaucoma without previous treatment or surgery and 50 of them are normal healthy persons. The glaucoma group was with mean C/D ratio of 0.15 ± 0.61 and of normal group was 0.07 ± 0.29. The mean of logMAR of best corrected visual acuity (BCVA) of the glaucoma group was 0.23 ± 0.39 and in normal group was 0.11 ± 0.09 [Table 1].
Table 1: Comparison between two studied groups according to demographic data

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The mean RNFL in patients with glaucoma was 12.47 ± 91.39, whereas in normal participants was 7.40 ± 110.9, which means significant thinning in RNFL in glaucoma group than in normal group, with P less than 0.001 [Table 2].
Table 2: Comparison between two studied groups according to retinal nerve fiber layer

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With EDI-OCT, the mean CT in patients with glaucoma was 37.78 ± 277.3, whereas in normal participants was 24.92 ± 259.8, which means significant thickening in CT in glaucoma group than in normal group, with P less than 0.001 [Table 3].
Table 3: Comparison between two studied groups according to CT

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The mean IOP measured from glaucoma group was 3.0 ± 26.16, whereas in normal group was 2.59 ± 19.50. Glaucoma group has significant higher IOP than normal group, with P less than 0.001 [Table 4].
Table 4: IOP difference between glaucoma and normal groups

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We found that no significant relation was found between both RNFL and IOP and CT, with P = 0.23 and 0.82, respectively. However, a significant relation was found between age and CT, with P = 0.012, in glaucoma group [Table 5].
Table 5: Correlation between variables (age, RNFL, IOP, and CT)

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[Figure 1] shows a 65-year-old patient with glaucoma with IOP 25, BCVA 6/12, C/D ratio 0.9, and RNFL thickness 68. By EDI-OCT, CT measurement was 318 Mm.
Figure 1: A 65-year-old patient with glaucoma with IOP 25, BCVA 6/12, C/D ratio 0.9, and RNFL thickness of 68. By EDI.OCT choroidal thickness measurement: 318 Mm. EDI-OCT, enhanced-depth imaging-optical coherence tomography; IOP, intraocular pressure; RNFL, retinal nerve fiber layer.

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  Discussion Top


The role of the choroid among the complex network of factors contributing to the pathogenesis glaucoma optic neuropathy is incompletely understood. To contribute to the understanding of the relationship between the choroid and glaucoma, studies have been carried out to measure the thickness of the choroid in glaucomatous eyes using histopathology or in-vivo imaging techniques. The conflicting results of those studies, coupled with recent advances in imaging of the ocular posterior segment, particularly with the advantage of spectral domain ocular coherent tomography (SD-OCT), was the impetus for reassessing the relationship between CT and glaucoma.

The current study was done on 100 glaucomatous eyes and 50 normal healthy eyes to evaluate the changes in mean choroid thickness (MCT) between two groups according to the change in their IOP.

In the present study, the finding we reached is that there is a statically significant difference between high IOP glaucoma group and normal IOP control group in subfoveal choroid thickness (SFCT), with P = 0.001, as MCT in glaucoma was 277.3 ± 37.78 and in normal group was 259.8 ± 24.92, with thicker choroid in group with high IOP than other group. Moreover, RNFL was found to be thinner in glaucoma group, with mean 91.39 ± 12.47, than normal IOP group, with mean 110.9 ± 7.40, with statistically significant relation (P < 0.001). The correlation between IOP and both RNFL and MCT was not significant, with P = 0.825 and 0.230, respectively.

In comparison, the study done by Arora et al.[5], with respect to CT in angle closure glaucoma, reported that CT was significantly greater in the angle closure glaucoma group than in the open-angle glaucoma group and normal participants, with no significant difference between eyes with open-angle glaucoma and normal participants.

In contrary to our study, Bron et al.[6] reported thinner SFCT in patients with POAG than normal controls in a study which involved 65 healthy eyes and 78 eyes with POAG. Moreover, a meta-analysis conducted by Lin et al.[7] demonstrated that average per papillary CT in open-angle glaucoma was significantly reduced compared with healthy individuals which was a potential support of the vascular theory of glaucoma and suggested that retrobulbar ischemia might affect the optic nerve head.

In another study on fellow eyes of 44 patients with unilateral acute primary angle closure, Zhou et al.[8] observed that the unaffected fellow eyes had thicker choroid than a group of control eyes.

Husseini et al.[9] presented a study on macular and per papillary CT in patients with perimetric glaucoma. They did not find any significant difference in SFCT between patients with open-angle glaucoma and nonglaucomatous individuals. They extended the examinations into the per papillary region, in which, except for the temporal region, CT did not differ between glaucomatous and control eyes. These findings may imply that choroid blood circulation may not be markedly involved or affected in open-angle glaucoma. However, the choroid is a highly dynamic vascular tissue, and purely anatomic measurements, such as CT, may not adequately describe altered hemodynamic physiology in various ocular diseases. Specifically, flow patterns in the per papillary choroid would be of great interest in glaucoma[9].

Mwanza et al.[10] reported their experience with in-vivo imaging of the choroid with Spectralis SD-OCT in primary open-angle and normal-tension glaucoma and normal controls. They confirmed that CT was mainly influenced by age and axial length (thinner choroid with older age and longer axial length). However, the authors did not find any significant difference among the three groups with respect to CT under the fovea center or up to 3 mm nasal or temporal to the fovea.

In another study by Mwanza et al.[11] on patients with unilateral advanced glaucoma the same findings were confirmed, suggesting a lack of association not only between CT and glaucoma but also with glaucoma severity.

In another study of 38 healthy participants, Kinoshita et al.[12] used both EDI-OCT and laser speckle flowgraphy to measure the choroid area and choroid blood velocity before, immediately after, and 10 min after mild dynamic exercise. Although choroid blood velocity changed with dynamic exercise, there were no significant changes in choroid area or the mean luminal and stromal area in this study, suggesting that exercise does not induce a structural change in the choroid. Notably, in the second study, the IOP decreased from 12.9 ± 2.91 mmHg at baseline to 11.4 ± 2.45 mmHg 10 min after exercise, but this small change in IOP was not associated with any choroid structural changes. This 1.5 mmHg change in IOP may be too small to induce a measurable significant change in CT. The different responses of the choroid vessel area and choroid interstitial area to different stimuli indicate a potentially complex relationship between choroid vessel area and overall CT, as well as a possible auto-regulatory mechanism in choroid vasculature [12].

There are some limitations to our study. We did not verify the glaucoma group according to angle shape either open-angle or closed angle glaucoma. Moreover, we focused on measuring the subfoveal region in estimating the changes in mean CT. Prior studies have related CT to blood pressure, diurnal variation[13], sex, axial length, age, and myopia[14]. As patients are being compared with themselves, patient-specific variables such as sex are accounted for. However, diurnal variation was not accounted for. Another variable that could not be assessed is the potential difference in the dynamic choroid vascular change between normal participants and those with glaucoma.


  Conclusion Top


The CT is higher in patients with glaucoma than in normal group based on EDI-OCT measurements.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Banitt M. The choroid in glaucoma. Curr Opin Ophthalmol 2013; 24:125-129.  Back to cited text no. 1
    
2.
Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: a review. JAMA 2014; 311:1901-1911.  Back to cited text no. 2
    
3.
Michelessi M, Lucenteforte E, Oddone F, Brazzelli M, Parravano M, Franchi S, et al. Optic nerve head and fibre layer imaging for diagnosing glaucoma. Cochrane Database Syst Rev 2015; 11:CD008803.  Back to cited text no. 3
    
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Baran U and Wang RK. Review of optical coherence tomography based angiography in neuroscience. Neurophotonics 2016; 3:010902.  Back to cited text no. 4
    
5.
Arora KS, Jefferys JL, Maul EA, Quigley HA. The choroid is thicker in angle closure than in open angle and control eyes. Investig Ophthalmol Vis Sci 2012; 53:7813-7818.  Back to cited text no. 5
    
6.
Bron AM, Francoz A, Beynat J, Nicot F, Cattaneo A, Creuzot C. Is choroid thickness different between glaucoma patients and healthy subjects. Acta Ophthalmol (Copenh) 2011; 89:1755-1768.  Back to cited text no. 6
    
7.
Lin Z, Huang S, Xie B, Zhong Y. Peripapillary choroidal thickness and open-angle glaucoma: a meta-analysis. J Ophthalmol 2016; 2016:12.  Back to cited text no. 7
    
8.
Zhou M, Wang W, Ding X, Huang W, Chen S, Laties AM, Zhang X. Choroidal thickness in fellow eyes of patients with acute primary angle-closure measured by enhanced depth imaging spectral-domain optical coherence tomography. Investig Ophthalmol Vis Sci 2013; 54:1971-1978.  Back to cited text no. 8
    
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Hosseini H, Nilforushan N, Moghimi S, Bitrian E, Riddle J, Lee GY, et al. Peripapillary and macular choroidal thickness in glaucoma. J Ophthalm Vis Res 2014; 9:154.  Back to cited text no. 9
    
10.
Mwanza JC, Hochberg JT, Banitt MR, Feuer WJ, Budenz DL. Lack of association between glaucoma and macular choroidal thickness measured with enhanced depth-imaging optical coherence tomography. Investig Ophthalmol Vis Sci 2011; 52:3430-3435.  Back to cited text no. 10
    
11.
Mwanza J, Sayyad F and Budenz D. Choroidal thickness in unilateral advanced glaucoma. Investig Ophthalmol Vis Sci 2012; 53:6695-6701.  Back to cited text no. 11
    
12.
Kinoshita T, Mori J, Okuda N, Imaizumi H, Iwasaki M, Shimizu M, et al. Effects of exercise on the structure and circulation of choroid in normal eyes. PLoS One 2016; 11:e0168336.  Back to cited text no. 12
    
13.
Iwase T, Yamamoto K, Ra E, Murotani K, Matsui S, Terasaki H. Diurnal variations in blood flow at optic nerve head and choroid in healthy eyes: diurnal variations in blood flow. Medicine (Balt) 2015; 94:e519.  Back to cited text no. 13
    
14.
Chakraborty R, Read SA, Collins MJ. Diurnal variations in axial length, choroidal thickness, intraocular pressure, and ocular biometrics. Investig Ophthalmol Vis Sci 2011; 52:5121–5129.  Back to cited text no. 14
    


    Figures

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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