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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 32  |  Issue : 2  |  Page : 655-659

Choroidal change assessment with enhanced depth imaging optical coherence tomography in myopic choroidal neovascularization


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

Date of Submission04-Sep-2017
Date of Acceptance19-Nov-2017
Date of Web Publication25-Jun-2019

Correspondence Address:
Hend AM Elabshihy
Alghrbia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_604_17

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  Abstract 

Objectives
The aim was to evaluate the importance of choroidal changes as measured by enhanced depth imaging optical coherence tomography (OCT) in patient with myopic choroidal neovascularization (mCNV) and to assess the correlation between choroidal thickness (CT) and other parameters such as age, sex, refraction, and staphyloma.
Background
High myopia is associated with profound changes in the choroid, which are important in the pathogenesis of many important visually significant abnormalities such as choroidal atrophy, CNV, and lattice degeneration. Therefore, it is called pathologic myopia.
Patients and methods
This prospective study was conducted from June 2016 to January 2017. Two groups of eyes were included: mCNV eyes (31 eyes) and eyes without CNV (19 eyes). CT was measured using the spectralis spectral domain OCT (specralis software version 4.0) in the Ophthalmology Department of the Menoufia University Hospital.
Results
It was found that CT was significantly decreased in the mCNV eyes compared with normal eyes, as the mean subfoveal CT in eyes with CNV was 103.10 ± 41.09. The mean subfoveal CT in eyes without CNV was 193.28 ± 17.38 (P < 0.001).
Conclusion
The ability of enhanced depth imaging OCT to visualize the ocular structure provides a more in-depth understanding of the various ocular pathologies. We found that in patients, CT decreased with the presence of mCNV, as compared with controls.

Keywords: choroidal thickness, enhanced depth imaging, myopic choroidal neovascularization, optical coherence tomography


How to cite this article:
Khairy HA, Zaky MA, Elabshihy HA. Choroidal change assessment with enhanced depth imaging optical coherence tomography in myopic choroidal neovascularization. Menoufia Med J 2019;32:655-9

How to cite this URL:
Khairy HA, Zaky MA, Elabshihy HA. Choroidal change assessment with enhanced depth imaging optical coherence tomography in myopic choroidal neovascularization. Menoufia Med J [serial online] 2019 [cited 2019 Sep 21];32:655-9. Available from: http://www.mmj.eg.net/text.asp?2019/32/2/655/260903




  Introduction Top


Myopic choroidal neovascularization (mCNV) is one of the leading causes of visual impairment worldwide. The clinical and socioeconomic effect of mCNV is particularly significant owing to rising trend in the prevalence and severity of pathological myopia. There is paucity of information with respect to incidence and risk factors for mCNV from prospective studies[1].

Furthermore, there are no recognized measures that may prevent or delay the development of CNV in eyes with pathological myopia. Advancements have been made in the diagnosis and characterization of mCNV over the years. Furthermore, the risk of developing chorioretinal atrophy remains a key factor in determining the final visual outcome[2].

In pathological myopia, excessive axial elongation of globe can cause biomechanical stretching and thinning of choroidal and retinal pigmented epithelium layers, leading to increased risk of chorioretinal complications such as CNV, posterior staphyloma, lacquer cracks in Bruch's membrane, and myopic foveoschisis, which may lead to visual loss[3],[4].

As some of the earliest changes in pathological myopia begin in the choroid, choroidal thickness (CT) could be an important parameter to study the pathogenesis of macular vision loss in high myopia. The thickness of the choroid can be measured by enhanced depth imaging (EDI)[5],[6],[7].

Recently, new imaging technologies have been suggested that quantify choroidal thinning and staphyloma height, which may be additional risk factors for CNV[8],[9]. Following the introduction of a new imaging technique, referred as EDI optical coherence tomography (OCT), choroid imaging with standard commercially available spectral domain optical coherence tomography (SD-OCT) was made possible[10].

EDI using OCT is obtained by positioning the SD-OCT device close enough to the eye to acquire an enhanced signal of the choroidal layer. Choroidal depth will be measured as the distance between the outer reflective retinal pigment epithelium (RPE) layer and the inner sclera border[11].

Optical coherence tomography angiography is a novel, noninvasive imaging technique that allows visualization of retinal microvasculature. It is an 'en-face' OCT-derived technique that detects intravascular blood flow using a split spectrum amplitude correlation angiography algorithm[12].

Fluorescein angiography is still considered the gold standard for the identification of myopic CNV, owing to the early filling of the lesion, followed by late leakage. OCT scanning can provide useful information about variations of the central foveal thickness, the presence of fluid, and the integrity of the outer retinal layers. However, it is not always possible to achieve a perfect correspondence between the two imaging procedures in both the diagnostic phase and during the monitoring of the therapy. In particular, the exact correlation between the onset and cessation of the leakage, on the one hand, and the relative changes in the retinal morphology, on the other, remains unclear[13].

The aim of this work was to evaluate the importance of choroidal changes as measured by EDI-OCT in patient with myopic CNV and to assess the correlation between CT and other parameters such as age, sex, refraction, and staphyloma.


  Patients and Methods Top


This was a prospective study conducted at the Ophthalmology Clinic at the Menoufia University Hospital from June 2015 to January 2017.

The study was approved by the Ethical Committee of Menoufia Medical School. The study protocol was explained to the patients, and all patients provided a written informed consent.

This study was conducted on 50 eyes of 25 patients, with 14 females and 11 males. CNV was bilateral in six patients. A total of 31 eyes had myopic CNV. The other normal eyes were used as non-CNV group (19 eyes).

Inclusion and exclusion criteria were applied only on these cases.

Inclusion criteria

  1. High myopia with spherical equivalent − 6 D or more
  2. Axial length greater than 26.0 mm
  3. Myopic CNV documented by fundus fluorescein angiography and OCT.


Exclusion criteria

The following patients were excluded from the study:

  1. CNV owing to causes other than myopia
  2. Retinoschisis or myopic traction maculopathy
  3. History of intravitreal injection of antivascular endothelial growth factors
  4. Glaucomatous patients
  5. Media opacity that prevent OCT imaging capture
  6. Other macular pathologies like central serous retinopathy or diabetic retinopathy.


Examination

All patients were subjected to the following.

History taking

Age, sex, past ocular and medical history, medications, allergies, and family history of ocular diseases along with symptoms of rapid decrease in the vision with or without metamorphopsia and central scotoma were recorded.

Visual acuity

It was measured using uncorrected visual acuity and best-corrected visual acuity (BCVA) with decimal scale.

Slit lamp examination of anterior segment

It was done to exclude presence of media opacity that may prevent OCT capture like corneal opacity or dense cataract.

Intraocular pressure measurement

It was done using Goldman applanation tonometry.

Gonioscopy

It was performed with three-mirror Gonio contact lens.

Dilated fundus examination

It was performed with +78 D volk lens to confirm clinical diagnosis of myopic CNV. CNV appears as subretinal greyish lesion with or without surrounding hemorrhage.

A scan and B scan ultrasound

It was used to detect posterior staphyloma and axial length measurement.

Fundus fluorescein angiography

It was done to ensure CNV activity characterized by 'classic' appearance with the presence of hyperfluorescence in early phases, corresponding to the filling of neovascular tissue, followed subsequently by leakage in the late phases of angiogram.

Moreover, it was used to detect other features of myopic maculopathy such as lacquer cracks.

Optical coherence tomography

The subfoveal choroidal thickness (SFCT) was obtained using spectralis SD-OCT with EDI 'enhanced depth imaging' modality (Heidelberg Engineering, Heidelberg, Germany).

Statistical analysis

Statistical presentation and analysis of this study was conducted using mean ± SD, Mann–Whitney test, and linear correlation coefficient tests using SPSS v. 20 (SPSS Inc., Chicago, Illinois, USA). P value less than 0.05 was considered statistically significant.


  Results Top


The mean SFCT was more than the mean temporal CT, which was more than the mean nasal CT. [Table 1]. This means that when temporal CT increases, nasal CT increases. In this study, there was no statistically significant deference between sex and CT [Table 2]. This study show statistically significant positive correlation between BCVA with SFCT and temporal CT (P < 0.001) [Table 3]. Moreover, it shows statistically significant deference between age and CT, when P value was less than 0.01* [Table 3]. This study shows highly statistically significant deference between cases with myopic CNV and nonmyopic CNV regarding CT (P < 0.001) [Table 4].
Table 1: The mean values, range, and SD of subfoveal, temporal and nasal thickness

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Table 2: Relation between sex and choroidal thickness

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Table 3: Correlation between age, best-corrected visual acuity, and choroidal thickness

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Table 4: Distribution of the studied groups with and without myopic choroidal neovascularization regarding choroidal thickness

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  Discussion Top


High myopia is associated with profound changes in the choroid, which are important in the pathogenesis of many important visually significant abnormalities such as choroidal atrophy, lacquer crack, Fuchs spots, CNV, macular retinoschisis, and peripheral lattice degeneration region. Therefore, it is also called pathologic myopia or degenerative myopia[14]. In recent years, the appearance of EDI-OCT has made the full-thickness choroidal imaging of living organisms possible. With the use of this technology, it was possible to discover that SFCT is relative to the perfusion pressure in eyes, which can indirectly reflect the blood perfusion status beneath the macula[15]. The CT was defined as the distance from the RPE line to the hyperrefractive line behind the large vessel layers of the choroid, presumed to be the choroid–sclera interface[16]. In the current study, the mean SFCT was more than the mean temporal CT, which was more than the mean nasal CT. This disagrees with IkunoY and Tano Y, as they stated that the mean CT was thinnest at the nasal quadrant and greatest at the temporal quadrant. CT at the fovea was significantly greater than that at the nasal quadrant, but significantly lower than that at the temporal[8]. This may be because of the activity of CNV, which causes edema of the choroid, and less number of patient. Moreover it shows highly statistically significant deference between SFCT and temporal CT and nasal CT. This study shows statistically significant deference between age and CT. This matches with Wei WB, Barteselli G, and Wei WB, who found that in patients older than 60 years, CT progressively decreases by 4 μm to 5 μm each year[17],[18]. Similarly, in the study by Ikuno and Tano, only borderline significance was detected between age and CT in simple regression analysis[8]. Another factor that influences CT is sex. In this study, there was no statistically significant deference between sex and CT. This disagrees with Wei et al.[17] and with Kim et al.[19] as they found that on average, healthy males have a 7% greater choroidal volume, which may explain the greater incidence of age-related macular degeneration among females who have thinner choroids at the outset. This study shows highly statistically significant correlation between BCVA and SFCT and temporal CT whereas nonstatistically significant deference between BCVA and nasal CT. This agrees with Chui[20], as he found that the decrease in thickness of the choroid in high myopes has, appropriately enough, been called myopic choroidal thinning. The expansion of the eye seems to cause a decrease in the packing density of the photoreceptors[20]. There is statistically significant deference in SFCT between case (eyes with myopic CNV) and control (eyes without myopic CNV). And with SFCT of control and temporal CT of cases also nasal with nasal (control). However, there was nonstatistically significant difference in others. This agrees with Cheung et al.[3] who calculated the mean CT was thinnest under the fovea in myopic CNV eyes (56.4 lm) than in the fellow eyes (73.1 lm). By averaging the measurements from all five areas (superior, inferior, nasal, temporal, and subfoveal), CT was significantly reduced in mCNV eyes compared with their fellow eyes[3]. This prospective study had some limitations. Pathological myopia is characterized by axial length elongation, as the light path courses a long distance inside the eye, which attenuates the OCT signal from the fundus. Highly myopic eyes often have a subtle cataract or corneal opacification. The measurements between two hyper-reflective lines of the RPE layer and inner scleral border are arbitrary and operator dependent. Image quality is dependent on the axial length and the patient's cooperation. Image quality decreases in elongated eyes and poorly fixating patients. To avoid selection bias by excluding highly myopic patients, the image quality of elongated eyes can be improved by adopting an extra-long option in the OCT machine, and researchers can suggest that the patient should wear his or her corrective spectacles.


  Conclusion Top


This study, through the measurement on the CT of high myopia patients with CNV. We found that the less CT the more likely CNV and the more posterior staphyloma height the more choroidal thinning.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Tan CS, Cheong KX, Sadda SR. Changes in choroidal thickness after photodynamic therapy in patients with central serous chorioretinopathy. Acta Ophthalmol 2014; 92:e79.  Back to cited text no. 1
    
2.
Neelama K, Cheungc CMG, Ohno-Matsuid K, Timothy YY, Wongb TY. Choroidal neovascularization in pathological myopia. Singapore: Singapore National Eye Center, Elsevier Ltd.; 2012.  Back to cited text no. 2
    
3.
Cheung CM, Loh BK, Li X, Mathur R, Wong E, Lee SY, et al. Choroidal thickness and risk characteristics of eyes with myopic choroidal neovascularization. Acta Ophthalmol 2013; 91:e580–e581.  Back to cited text no. 3
    
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Jonas JB, Holbach L, Panda-Jonas S. Bruch's membrane thickness in high myopia. Acta Ophthalmol 2014; 92:470–474.  Back to cited text no. 4
    
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Kim DY, Silverman RH, Chan RV, Khanifar AA, Rondeau M, Lloyd H, et al. Measurement of choroidal perfusion and thickness following systemic sildenafil (Viagra). Acta Ophthalmol 2013; 91:183–188.  Back to cited text no. 5
    
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Hashizume K, Imamura Y, Fujiwara T, Machida S, Ishida M, Kurosaka D. Choroidal thickness in eyes with posterior recurrence of Vogt-Koyanagi-Harada disease after high-dose steroid therapy. Acta Ophthalmol 2014; 92:e490–e491.  Back to cited text no. 6
    
7.
Zhou M, Wang W, Huang W, Gao X, Li Z, Li X, Zhang X. Is increased choroidal thickness association with primary angle closure? Acta Ophthalmol 2014; 92:514–520.  Back to cited text no. 7
    
8.
Ikuno Y, Tano Y. Retinal and choroidal biometry in highly myopic eyes with spectral-domain optical coherence tomography. Invest Ophthalmol Vis Sci 2009; 50:3876–3880.  Back to cited text no. 8
    
9.
Parodi MB, Iacono P, Ravalico G. Fundus autofluorescence in subfoveal choroidal neovascularisation secondary to Pathological Myopia. Br J Ophthalmol 2009; 93:771-4.  Back to cited text no. 9
    
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Spaide RF. The chorid. In: Spaide RF, Ohno-Matsui K, Yannuzzi LA, eds. Pathologic myopia. New York: Springer, 2014. p. 113-31.  Back to cited text no. 10
    
11.
Ho M, Liu DT, Chan VC, Lam DS. Choroidal thickness measurement in myopic eyes by enhanced depth optical coherence tomography. Ophthalmology 2013; 120:1909–1914.  Back to cited text no. 11
    
12.
Jia Y, Tan O, Tokayer J, Potsaid B, Wang Y, Liu JJ, et al. Split-spectrum amplitudedecorrelation angiography with optical coherence tomography. Opt Express 2012; 20:4710–4725.  Back to cited text no. 12
    
13.
Parodi MB, Iacono P, Ravalico G. Fundus autofluorescence in subfoveal choroidal neovascularisation secondary to Pathological Myopia. Br J Ophthalmol 2009; 93:771-4.  Back to cited text no. 13
    
14.
Spaide RF. The chorid. In: Spaide RF, Ohno-Matsui K, Yannuzzi LA, eds. Pathologic myopia. New York: Springer, 2014:113-31.  Back to cited text no. 14
    
15.
Li L, Yang ZK, Dong FT. Choroidal thickness in normal subjects measured by enhanced depth imaging optical coherence tomography. Chin J Ophthalmol 2012; 48:819–823.  Back to cited text no. 15
    
16.
Margolis R, Spaide RF. A pilot study of enhanced depth imaging optical coherence tomography of the choroid in normal eyes. Am J Ophthalmol 2009; 147:811–815.  Back to cited text no. 16
    
17.
Wei WB, Xu L, Jonas JB. Subfoveal choroidal thickness: the Beijing Eye Study. Ophthalmology 2013; 120:175–180.  Back to cited text no. 17
    
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Barteselli G, Chhablani J, El-Emam S. Choroidal volume variations with age, axial length, and sex in healthy subjects: a three-dimensional analysis. Ophthalmology 2012; 119:2572–2578.  Back to cited text no. 18
    
19.
Kim M, Kim SS, Kwon HJ, Koh HJ, Lee SC. Association between choroidal thickness and ocular perfusion pressure in young, health subjects: enhanced depth imaging optical coherence tomography study. Invest Ophthalmol Vis Sci 2012; 53:7710–7717.  Back to cited text no. 19
    
20.
Chui TY, Song H, Burns SA. Individual variations in human cone photoreceptor packing density: variations with refractive error. Invest Ophthalmol Vis Sci 2008; 49:4679–4687.  Back to cited text no. 20
    



 
 
    Tables

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



 

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