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ORIGINAL ARTICLE
Year : 2020  |  Volume : 23  |  Issue : 9  |  Page : 1243-1247

Evaluation of choroidal thickness before and after strabismus surgery in paediatric patients by spectral-domain optical coherence tomography


1 Adıyaman University, School of Medicine, Department of Ophthalmology, Adıyaman, Turkey
2 Harran University, School of Medicine, Department of Ophthalmology, Harran, Turkey

Date of Submission18-Sep-2019
Date of Acceptance07-Apr-2020
Date of Web Publication10-Sep-2020

Correspondence Address:
Dr. A Simsek
Harran University, School of Medicine, Department of Ophthalmology, Harran - 63000
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_500_19

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   Abstract 


Aim: This study aimed to determine the effects of strabismus surgery on choroidal thickness in paediatric patients with Spectral Domain-Optical Coherence Tomography (SD-OCT). Material and Methods: Sixty eyes of 60 children with esotropia were included. The mean age was 9.5 ± 3.1 years. The choroidal thickness was measured using SD-OCT, which was performed before the surgery and 1 week, 1 month and 3 months postoperatively. At the same time, the patients' visual acuity was evaluated. Results: There were no statistically significant differences between the preoperative and postoperative values in terms of the visual acuity (P > 0.05). When compared to the preoperative values, decreases were found in the choroidal thicknesses in all of the areas measured during the first week evaluation (P < 0.05). In the postoperative first month, significant decreases were also found in the choroidal thicknesses in all the areas measured (P < 0.05); however, in the postoperative third month, there were no changes in any of the areas (P > 0.05).
Conclusions: We observed that there was a significant decrease in the choroidal thickness during the early postoperative period and no significant change in the late postoperative period in paediatric patients of double horizontal muscle surgery. Moreover, these early changes in the choroid in paediatric patients show that it does not cause a functional loss.

Keywords: Choroid, paediatric, strabismus


How to cite this article:
Yetkin A A, Simsek A. Evaluation of choroidal thickness before and after strabismus surgery in paediatric patients by spectral-domain optical coherence tomography. Niger J Clin Pract 2020;23:1243-7

How to cite this URL:
Yetkin A A, Simsek A. Evaluation of choroidal thickness before and after strabismus surgery in paediatric patients by spectral-domain optical coherence tomography. Niger J Clin Pract [serial online] 2020 [cited 2020 Sep 24];23:1243-7. Available from: http://www.njcponline.com/text.asp?2020/23/9/1243/294683




   Introduction Top


Strabismus surgery has a variety of applications and most of all, recession and resection is applied.[1] The purpose of strabismus surgery is to ensure properly aligned eyes, prevent amblyopia and create binocular single vision.[2] All surgeries carry risks of complications, and there is no way to avoid ever having a complication. Strabismus surgery is no different in this regard.[3] Surgery on an adjacent vertical and horizontal rectus muscle is more likely to lead to an observable effect on anterior segment circulation.[3] One of the possible effects is anterior segment ischemia. Anterior segment ischemia is a complication that is rarely seen after strabismus surgery. Strabismus surgery is known to disrupt choroidal blood flow.[4]

The choroid is a vascular layer extending between the sclera and the retina in the eye. It is one of the most vascularized tissues in our body[1] and a vascular structure supplying the outer retina with nutrients and oxygen. It also functions in thermoregulation and plays a role in the growth of the sclera and eye, thus regulating emmetropization.[5] The choroid must have a healthy bloodstream to perform these functions.[5] The choroidal blood flow is delivered by siliceous arteries, which are branches of the ophthalmic artery.[6] Choroid thickness was correlated with thechoroid blood flow.[6]

Spectral Domain-Optic Coherence Tomography (SD-OCT) has been shown to provide advanced imaging to evaluate the three-dimensional anatomy of the choroid layers and retinal pigment epithelium.[7],[8] SD-OCT is the most commonly used imaging technique for macular examination since it represents the only imaging modality allowing direct visualization of the layered retinal structures.[9] SD-OCT can be used to examine the choroidal tissue which is a vascular structure that carries micronutrient and oxygen to the retinal tissues.[10] SD-OCT technology has provided a repeatable and reliable method to evaluate choroidal thickness.

In the literature, we could not find a study on the effect of strabismus surgery on choroidal tissue in paediatric patients. In this prospective study, we aimed to investigate the influence of strabismus surgery on the choroidal thickness in paediatric patients with SD-OCT.


   Materıal and Methods Top


This prospective study was performed in the Department of Ophthalmology at Adiyaman University Hospital between January 2015 and May 2017 by the Declaration of Helsinki. Adiyaman University Institutional Ethics Committee approval and written informed consent from all of the parents of the participants was obtained before the study.

Sixty paediatric patients were enrolled in this study. Those patients with histories of glaucoma, diabetic retinopathy, keratoconus, contact lens use, ocular surgery or ocular trauma, chronic systemic disease, and vascular abnormalities detected during ophthalmological examinations were excluded from the study. The patients with myopic, hypermetropic and astigmatic refractive errors greater than ±1.0D were excluded. In addition, the patients who could not perform SD-OCT were excluded from the study.

All of the patients underwent detailed ophthalmological examinations, including refractive error, visual acuity, slit lamp and dilated fundus examinations. The best visual acuity values (obtained from the Snellen chart) of each patient were recorded using a specific statistical program. The following information was recorded for each patient: Preoperative and postoperative head position, eye movements in nine cardinal positions, presence or absence of additional extraocular muscle movements or weakness, alternating prism cover test results in compatible cases (The Krimsky or Hirschberg test was used in the incompatible cases), alternation presence and grade.

All of our patients were operated on using the same techniques and the same surgeon, and the surgeries were performed under general anaesthesia. A limbal conjunctival incision was used to reach the muscles during surgery, and our patients had Double horizontal muscle surgery (MR recession + LR resecton). The muscle was sutured using 6-0 and 8-0 vicryl sutures were used for the conjunctival, closure. Postoperatively, topical antibiotics were prescribed for 1 week and topical steroid eyedrops were prescribed for 2 weeks.

The choroid images were recorded with undilated pupils, using the choroidal mode of the SD-OCT system (RTVue 100°CT, software version 6.3; Optovue, Inc., Fremont, CA, USA). Two experienced ophthalmologists recorded the images, and two sets of measurements were obtained and averaged. The differences between the masked physicians' readings were determined to be within 10% of the mean, and those images with signal strength indexes > 60 were included. Patients were examined between 1:00 pm and 3:00 pm to exclude diurnal variations, and for the statistical analysis, the right eye measurements were recorded. The measurements of both the right and left eyes in the patients and controls were obtained to assess the reproducibility of the OCT machine measurements. The distance from the outer retinal epithelial line to the hyper-reflective line behind the large vessel layers of the scleral interface was defined as choroidal thickness and measured manually in all subjects. The measurement of choroidal thickness was performed at 7 points: At the foveal centre and within the horizontal nasal and temporal quadrants at 500 μm intervals, to a distance of 1500 μm from the foveal centre [Figure 1]. All these measurements were made before and after the surgery and at the 1-week, 1-month and 3-month follow-ups.
Figure 1: Choroidal thickness measurement from 7 points

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Statistics

The version SPSS 15.0 was used for the statistical analysis (Statistical Package for the Social Sciences Inc., Chicago, IL, USA). Kolmogorov-Smirnov test was used to assess the normality of continuous data. The categorical variables included in the study were shown as the mean ± standard deviation (SD). The choroidal thickness differences between the measurements were assessed with the Wilcoxon test, while the choroidal thickness differences between the groups were evaluated by the paired samples t test. A P value of <0.05 was considered to be statistically significant.


   Results Top


A total of 74 patients were evaluated during the study period. Fourteen patients were excluded from the study as follows: Five patients were uncooperative, six had secondary strabismus surgery and three had image quality problems. After these exclusions, 60 patients were remained as the study participants. Of these 60 patients, 30 (50%) were males and 30 (50%) were females. The mean age was 9.5 ± 3.1 years. In all cases, there was a satisfactory correction of the eye deviation. A total of 95.3% of our cases were within 20 primary deviations (PD) three months after the surgery. No significant complications developed during or after the surgery, and postoperative visual acuity and refractive errors were not detected. There was no statistically significant difference between the preoperative and postoperative values in terms of the visual acuity (P > 0.05, [Table 1]).
Table 1: Preoperative and postoperative visual acuities

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The preoperative and postoperative 1-week, 1-month and 3-month choroidal thicknesses were compared separately. The postoperative 1-week and 1-month choroidal thicknesses were significantly decreased at all points when compared to the preoperative choroidal thickness (P < 0.05), but the postoperative 3-month choroidal thickness was not significantly changed when compared to the preoperative choroidal thickness (P > 0.05). The preoperative and postoperative thickness measurements are shown in [Table 2].
Table 2: Comparisons of choroidal thicknesses in the study

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   Discussion Top


In our study, we found that choroidal thickness was significantly decreased in paediatric patients who had strabismus surgery in the early period compared to the preoperative period. The choroidal thickness was thinner in the entire quadrant. However, we observed that the choroidal thickness returned to the ordinary in the third postoperative month.

The choroid takes up about 95% of the ocular blood fflow.[11] It plays an important role in regulating the metabolic activity and temperature of the retina, and the degradation of the choroidal blood flow is important in the pathogenesis of various retinal diseases.[11] Until recently, the choroid was evaluated via the use of indocyanine green angiography, laser flowmetry, and ultrasonography; however, these techniques only show the choroidal vessel abnormalities and blood flow changes. Recently, SD-OCT was introduced as a means to appraise the three-dimensional anatomy of the choroid and retina layers.[12] In some studies using SD-OCT, the choroidal thickness measurements were reported to be decreased in patients who had myopia and diabetic retinopathy as well as found to be increased in patients with hypothyroidism and central serous chorioretinopathy.[13],[14] In addition, Karalezli et al.[15] reported that the mean choroidal thickness was thinner in patients with obstructive sleep apnoea syndrome due to hypoxia and reperfusion attacks. Moreover, Mathew et al.[16] suggested that sickle cell disease may decrease choroidal thickness to ischemia and the slower blood flow.

We know that strabismus surgery is likely to lead to an advers effect on anterior segment circulation.[3] As the number of rectus muscles operated increases, this risk increases.[17] The effects of strabismus on the choroid are not as clear as the anterior segment. We found choroidal thinning during the early postoperative period in paediatric patients who underwent horizontal strabismus surgery. However, we did not find differences in the choroidal thickness during the late postoperative period. This situation shows us that the choroidal circulation deteriorates in the early period but it has improved in the late period.

The surgical improvement of strabismus does not appear to influence long-term visual acuity.[18] In our study, we observed that there was no statistically significant difference between the preoperative and postoperative values in terms of the visual acuity in the paediatric patients (P > 0.05), and these results are consistent with the literature. Although there are early changes in the choroid in double muscle surgeries, it does not cause functional loss in the paediatric patients.

In the literature, only one study of the effects of strabismus surgery on the choroidal tissue was found. Inan et al.[19] reported that when a single-muscle operation was performed, the choroidal thickness of the patient was decreased on the first day and second week after surgery, and it reached the preoperative values during the first and third months. The probable mechanism is that single-muscle operations may cause vascular damage and compensatory vasoconstriction at the level of the choroid, which may lead to ischemia. In our study, we observed that there was a significant decrease in the choroidal thickness during the early postoperative period and no significant change in the late postoperative period in paediatric patients of double horizontal muscle surgery. Although our study has two muscular surgeries, the findings are similar to this study in the literature. The probable mechanism is as follows: During strabismus surgery, the anterior ciliary artery cessation, vascular injury and compensatory vasoconstriction may cause ischemia and slower blood flow during the early postoperative period. Later, the choroidal thickness returns to the preoperative values via the introduction of compensatory mechanisms in the late postoperative period. The exact mechanisms are unknown; therefore, more research is needed in these patients.

We know that the choroid is necessary for feeding the retina and if the choroidal blood flow decreases, the choroidal thickness decreases. This change may cause functional impairment in the retina. Visual acuity is one of the parameters showing the retina function. The early changes in the choroid did not cause any functional loss in the previously performed single-muscle surgeries and our performed double muscle surgery in paediatric patients. The most important difference in our study is that it shows that choroidal thickness does not change in children with double muscle surgery. I think this finding may be a guide for future studies. More large case studies are needed to say that double muscle surgery has no effect on visual acuity in the paediatric patients.

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.



 
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Kasem MA, Sabry D. Detecton of macular changes by optcal coherence tomography afer inferior oblique muscle surgery. JAAPOS 2011;15:334-7.  Back to cited text no. 4
    
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Cense B, Chen TC, Nassif N, Pierce MC, Yun SH, Park BH, et al. Ultra-high speed and ultra-high resolution spectral-domain optical coherence tomography and optical Doppler tomography in ophthalmology. Bull Soc Belge Ophtalmol 2006:123-32.  Back to cited text no. 10
    
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Sugiyama T, Araie M, Riva CE, Schmetterer L, Orgul S. Use of laser speckle flow graphy in ocular blood flow research. Acta Ophthalmol 2010;88:723-9.  Back to cited text no. 11
    
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Simsek A, Tekin M, Bilak S, Karadag AS, Konca C, Almis H. Choroidal thickness in children with beta thalassemia major. Optom Vis Sci 2016;93:600-6.  Back to cited text no. 12
    
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Read SA, Collins MJ, Vincent SJ, Alonso-Caneiro D. Choroidal thickness in myopic and nonmyopic children assessed with enhanced depth imaging optical coherence tomography. Invest Ophthalmol Vis Sci 2013;54:7578-86.  Back to cited text no. 13
    
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Ulas F, Dogan Ü, Dikbas O, Celebi S, Keles A. Investigation of the choroidal thickness in patients with hypothyroidism. Indian J Ophthalmol 2015;63:244-9.  Back to cited text no. 14
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Karalezli A, Eroglu FC, Kivanc T, Dogan R. Evaluation of choroidal thickness using spectral-domain optical coherence tomography in patients with severe obstructive sleep apnea syndrome: A comparative study. Int J Ophthalmol 2014;7:1030-4.  Back to cited text no. 15
    
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Mathew R, Bafiq R, Ramu J, Pearce E, Richardson M, Drasar E, et al. Sivaprasad S. Spectral domain optical coherence tomography in patients with sickle cell disease. Br J Ophthalmol 2015;99:967-72.  Back to cited text no. 16
    
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Brooks SE, Olitsky SE, deB Ribeiro G. Augmented hummelsheim procedure for paralytic strabismus. J Pediatr Ophthalmol Strabismus 2000;37:189-95.  Back to cited text no. 17
    
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Bothun ED, Lynn MJ, Christiansen SP, Kruger SJ, Vanderveen DK, Neely DE, et al. Infant aphakic treatment study. Strabismus surgery outcomes in the Infant aphakia treatment study (IATS) at age 5 years. J AAPOS 2016;20:501-5.  Back to cited text no. 18
    
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