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ORIGINAL ARTICLE
Year : 2018  |  Volume : 31  |  Issue : 4  |  Page : 1324-1328

Ocular coherence tomography study of the retinal nerve fiber layer following retinal vein occlusion


Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission08-Mar-2017
Date of Acceptance18-Apr-2017
Date of Web Publication14-Feb-2019

Correspondence Address:
Ahmed Y Abd-Elmonem
Faculty of Medicine, Menoufia University, Ashmoon, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_142_17

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  Abstract 


Objectives
The objective of this article is to analyze the changes in the retinal nerve fiber layer (RNFL) thickness in retinal vein occlusion using optical coherence tomography.
Background
Optical coherence tomography is a noninvasive test that gives high-resolution sectional images of the RNFL that are used to measure RNFL thickness in studies of glaucoma and other optic neuropathies.
Patients and methods
The study included 50 eyes (25 right and 25 left eyes) of 25 adult patients having unilateral branch retinal vein occlusion, for which optical coherence tomography was obtained.
Results
There was a statistical significant difference between normal and diseased eyes regarding retinal nerve fiber thickness (P < 0.001). The RNFL thickness is significantly lower in patient with history of diabetes mellitus than those with no history (P = 0.0321). The mean RNFL thickness was 50.10 ± 25.23 μm for diabetic patients. The nerve fiber layer thickness is significantly lower in patients with hypertension than in those with no history (P = 0.002). The mean nerve fiber layer thickness was 44.38 ± 23.2 μm for patients with hypertension. The thickness is significantly lower in patient with history of glaucoma than those with no history (P = 0.002). The mean nerve fiber layer thickness was 40.42 ± 23.15 μm for patients with glaucoma.
Conclusion
Optical coherence tomography might reflect the thinning of the RNFL after branch vein occlusion and showed that RNFL damage had a relationship with other ocular and systemic diseases.

Keywords: branch retinal vein occlusion, glaucoma, optical coherence tomography, retinal nerve fiber layer, retinal vein occlusion


How to cite this article:
Abd-Elmonem AY, Khairy H, Farahat H. Ocular coherence tomography study of the retinal nerve fiber layer following retinal vein occlusion. Menoufia Med J 2018;31:1324-8

How to cite this URL:
Abd-Elmonem AY, Khairy H, Farahat H. Ocular coherence tomography study of the retinal nerve fiber layer following retinal vein occlusion. Menoufia Med J [serial online] 2018 [cited 2024 Mar 28];31:1324-8. Available from: http://www.mmj.eg.net/text.asp?2018/31/4/1324/252022




  Introduction Top


Retinal venous occlusion is supposed to be the most common retinal vascular disorder following diabetic retinopathy. Branch retinal vein occlusion, in particular, affects ∼1% of the population older than 48 years[1].

Imaging methods used to evaluate the retinal nerve fiber layer (RNFL) include optical coherence tomography, scanning laser polarimetry, and confocal laser scanning ophthalmoscopy[2].

Optical coherence tomography is a noninvasive, noncontact evaluation method that allows quantitative measurements of retinal thickness and volume. It provides cross-sectional images of the retina, which resemble histologic sections seen with light microscopy[3].

Optical coherence tomography is an accurate tool for early diagnosis, analysis, and monitoring of diabetic retinopathy, with high repeatability and resolution. It allows not only the qualitative diagnosis of diabetic macular edema but also the quantitative assessment of diabetic macular edema[4].

Optical coherence tomography calculates retinal thickness by measuring the distance between the vitreoretinal interface and the anterior surface of the retinal pigment epithelium–choriocapillaris region. The algorithms detect the vitreoretinal interface by searching each A-scan axially from anterior to posterior for a rate of change in reflectivity above a threshold rate. From below the retinal surface, it searches posteriorly for the retinal pigment epithelium (RPE) surface. The retinal thickness algorithm searches for the highest rate of change in reflectivity and then for reflectivity above a threshold value. These algorithms take advantage of the very high-resolution capability of the optical coherence tomography, resulting in a highly refined objective measurement of retinal thickness. The processed scan image shows the boundaries in white. The algorithms include alignment, smoothing, and error correction[5].


  Patients and Methods Top


This cross-sectional study included cases of branch retinal vein occlusion. They were recruited from the Ophthalmology Clinic of Menoufia University Hospital. The study included 50 eyes (25 right and 25 left eyes) of 25 adult patients (males and females), with different ages over 18 years, having unilateral branch retinal vein occlusion, for which optical coherence tomography was obtained. The study was approved by the Ethical Committee of the Faculty. Informed consent was taken from each participant.

Inclusion criteria

Main inclusion criterion for the study group was the confirmed diagnosis of branch retinal vein occlusion.

Exclusion criteria

Previous intraocular surgery, vitreoretinal pathology other than retinal vein occlusion, tractional retinal edema, retinal surface peaking, epiretinal membrane, and focal or multifocal partial vitreomacular separation in optical coherence tomography, previous laser treatment, or intravitreal injection in the studied eye were the exclusion criteria.

All patients were examined thoroughly, including slit-lamp microscope and fundus examination, and assessment of uncorrected visual acuity, best-corrected visual acuity, and intraocular pressure. Optical coherence tomography of the affected and the unaffected eyes was done to measure the thickness parameter (average, four quadrant, and 12-clock-hour thicknesses) of the RNFL of both eyes.

Optical coherence tomography measurements

RNFL is measured in the peripapillary region, with circular scans of 3.4-mm diameter centered around the optic nerve head were examined using spectral-domain optical coherence tomography (SD-OCT) (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany). The thickness of the RNFL around the optic disc was scanned at 256 points at one time in a 3.4-mm diameter circle using SD-OCT. The scan was repeated three times, and the results were synthesized automatically. Then, one skilled examiner measured the mean value using the fast RNFL thickness protocol giving the value in micrometers with the pupil dilated more than 5 mm. We analyzed the RNFL thickness using the 12-clock-hour map of the SD-OCT.

For branch retinal vein occlusion, the entire area was divided into the superotemporal, superonasal, inferonasal, and inferotemporal quadrants. The affected region was defined as the mean value corresponding to the area covering 120-clock or 4-clock hours, which included the area of branch retinal vein occlusion.

The differences between the occluded and healthy contralateral eye were assessed to identify the differences between the two eyes.

Statistical analysis

The collected data were analyzed using statistical package for the social science (SPSS version 20; SPSS Inc., Chicago, Illinois, USA).

χ2-Test was used to study association between two qualitative variables.

Mann–Whitney test (nonparametric test) is a test of significance used for comparison between two groups not normally distributed having quantitative variables.

Kruskal–Wallis test (nonparametric test) is a test of significance used for comparison between three or more groups not normally distributed having quantitative variables.

Post-hoc test (Tamhane test) is a test of significance used after Kruskal–Wallis test for detecting significance between the pairwise differences.

Spearman correlation coefficient (r) (nonparametric test) is a test used to measure the association between two quantitative variables not normally distributed or one quantitative and other qualitative variables.

A P value of less than 0.05 was considered statistically significant.


  Results Top


This study included 50 eyes (25 right and 25 left eyes) of 25 patients (13 males and 12 females). The mean age among the studied group of our cases was 43.88 years.

There was statistical significant different between normal and diseased eye regarding retinal nerve fiber thickness (P < 0.001) [Table 1]. The mean RNFL thickness was 73.36 ± 26.10 μm for branch retinal vein occlusion eyes, and 108.24 ± 35.46 μm for the fellow eyes.
Table 1: Retinal nerve fiber layer thickness in patients with branch retinal vein occlusion with other ocular and systemic diseases

Click here to view


The RNFL thickness in our cases is significantly lower in patient with history of diabetes mellitus than those with no history (P = 0.0321) [Table 1]. The mean RNFL thickness was 50.10 ± 25.23 μm for diabetic patients and 72.86 ± 26.10 μm for normal patients.

The RNFL thickness is significantly lower in patient with history of hypertension than those with no history (P = 0.002) [Table 1]. The mean RNFL thickness was 44.38 ± 23.2 μm for patients with hypertension, and 77.67 ± 26.42 μm for normal patients.

The RNFL thickness is significantly lower in patient with history of glaucoma than those with no history (P = 0.002) [Table 1]. The mean RNFL thickness was 40.42 ± 23.15 μm for patients with glaucoma, and 85.83 ± 33.09 μm for normal patients.

There was significant negative correlation between RNFL thickness and duration of the disease, with P value of 0.001 [Table 1].


  Discussion Top


In our study, we used optical coherence tomography for assessment of RNFL thickness. For patient with branch retinal vein occlusion, the entire area was divided into the superotemporal, superonasal, inferonasal, and inferotemporal quadrants. The affected region was defined as the mean value corresponding to the area covering 120-clock or 4-clock hours, which included the area of branch retinal vein occlusion, and then recorded and compared with the normal eye [Figure 1].
Figure 1: Inferotemporal branch retinal vein occlusion of left eye. The thickness of the retinal nerve fiber layer at the affected part is 56 μm.

Click here to view


RNFL defects in retinal vein occlusion can occur in association with systemic diseases, such as hypertension or diabetes[6].

Elevated intraocular pressure is an important factor in retinal vein occlusion, as the intraocular pressure compresses the retinal vein, causing thickening of the vascular wall; several reports have examined the associations between retinal vein occlusion and ocular hypertension and open-angle glaucoma[7].

Damage caused by retinal ischemia is a main cause of RNFL damage in retinal vein occlusion; this results from systemic diseases, including diabetes, hypertension, carotid ischemia, and hematologic disorders that induce hypercoagulation[8].

In diabetes, thinning of RNFL can occur in the absence of glaucoma and other optic nerve diseases. Increased apoptosis, glial cell reactivity, microglial, and altered glutamate mechanism are some neurodegenerative changes that have been proposed to occur in diabetic retinopathy (DR)[9].

The patients with unilateral retinal vein occlusion had RNFL defects compared with the fellow eye, suggesting a causal relationship between glaucoma and retinal vein occlusion[10].

The current study revealed that there was decrease in RNFL thickness caused by the branch retinal vein occlusion itself, or by its accompanying causes of retinal vein occlusion such as glaucomatous changes or the effects of systemic diseases like diabetes, hypertension, carotid ischemia, and hematologic disorders that induce hypercoagulation, which cause retinal ischemia and subsequently cause RNFL damage.

Our study show that there was statistical significant different between normal and diseased eye regarding retinal nerve fiber thickness (P < 0.001), and there was significant negative correlation between retinal nerve fiber thickness and duration of the disease.

Our study shows that that there was significant negative correlation between diabetes mellitus and RNFL thickness among the studied group. Moreover, there was significant negative correlation between hypertension and RNFL thickness among the studied group.

Our study shows that that there was significant negative correlation between glaucoma and RNFL thickness among the studied group.

Our study shows that there was significant negative correlation between retinal nerve fiber thickness and duration of the disease, as with time, the thickness of RNFL decreases more.

In the present study, we observed that the longer the time of the disease, the more the decrease in the thickness of the RNFL.

There was significant negative correlation between RNFL thickness and duration of the disease, with P value of 0.001 and r value of 0.662.

This study has a few limitations as this study showed that the RNFL thickness initially increased because of edema after branch retinal vein occlusion but then returned to normal as the edema resolved. This may interfere with accurate measurement of RNFL thickness.

RNFL thickness may be decreased in sectors with retinal vein occlusion, which would confound any measurement of glaucomatous thinning of the RNFL. RNFL defect may develop from a retinal cotton-wool spot in a patient with diabetes mellitus and systemic hypertension. With these limitations in mind, we conducted measurements on the contralateral eyes of patients with retinal vein occlusion.

Increased thinning of the RNFL in patients aged more than 60 years, as shown in the present study, may suggest that arterial stiffness and atherosclerosis may explain both retinal vein occlusion and thinning of the RNFL.


  Conclusion Top


This study showed that in addition to glaucoma and systemic diseases, branch retinal vein occlusion itself can be a cause of RNFL defects. Moreover, the sectorial RNFL defects in patients with old branch retinal vein occlusion of uncertain history could be misregarded as glaucoma. Careful examination using angiography as well as examination of the optic disc could help determine the exact cause of the RNFL defect.

The mechanism of thinning of the RNFL after branch retinal vein occlusion is still unclear. Further studies are needed to confirm the results of our study and to determine the exact mechanism of changes in RNFL thickness.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Rehak J, Rehak M. Branch retinal vein occlusion: pathogenesis, visual prognosis, and treatment modalities. Curr Eye Res 2008; 33:111–131.  Back to cited text no. 1
    
2.
Pueyo V, Polo V, Larrosa JM, Mayoral F, Ferraras A, Honrubia FM. Reproducibility of optic nerve head and retinal nerve fiber layer thickness measurements using optical coherence tomography. Arch Soc Esp Oftalmol 2006; 81:205–212.  Back to cited text no. 2
    
3.
Hee MR, Izatt JA, Swanson EA, Huang D, Schuman JS, Lin CP, et al. Optical coherence tomography of the human retina. Arch Ophthalmol 1995; 113:325–332.  Back to cited text no. 3
    
4.
Wagdy FM, Sarhan ARE, Elmorsy OA, Galal MAZ, Nassar MK. Optical coherence tomography as a prognostic tool for visual improvement after management of diabetic macular edema. Menouf Med J 2014; 27:147–177.  Back to cited text no. 4
    
5.
Hussain A, Hussain N, Nutheti R. Comparison of mean macular thickness using optical coherence tomography and visual acuity in diabetic retinopathy. Clin Experiment Ophthalmol 2005; 33:240–245.  Back to cited text no. 5
    
6.
Jakobiec FA. Ocular anatomy, embryology, and teratology. Philadelphia, PA: Harper and Row Publishers Inc.; 1982.  Back to cited text no. 6
    
7.
Saint-Geniez M, D'Amore PA. Development and pathology of the hyaloid, choroidal and retinal vasculature. Int J Dev Biol 2004; 48:1045–1058.  Back to cited text no. 7
    
8.
Knighton RW, Jacobson SG, Kemp CM. Spectral reflectance of the retinal nerve fiber layer in macaques. Invest Ophthalmol Vis Sci 1998; 30:2392–2402.  Back to cited text no. 8
    
9.
Barber AJ. A new view of diabetic retinopathy: a neurodegenerative disease of the eye. Prog Neuropsychopharmacol Biol Psychiatry 2003; 27:283–290.  Back to cited text no. 9
    
10.
Kim MJ, Woo SJ, Park KH, Kim TW. Retinal nerve fiber layer thickness is decreased in the fellow eyes of patients with unilateral retinal vein occlusion. Ophthalmology 2011; 118:706–710.  Back to cited text no. 10
    


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