Georgian Scientists/ . 5 N 4, 2023 353 Georgian Scientists Vol. 5 Issue 4, 2023 https://doi.org/10.52340/gs.2023.05.04.32 Choroidal and Retinal Thickness in myopic Children Measured by Swept-Source Optical Coherence Tomography Sofio Meskhi1; Davit Shengelia2; Bacho Shengelia2; Tinatin Kilasonia2 1Caucasus Medical Center https://orcid.org/0009-0006-6455-6413, Tbilisi state medical university, the Department of Eye Diseases Abstract PURPOSE: To investigate the choroidal and retinal thickness in myopic children by swept-source longer-wavelength optical coherence tomography. DESIGN: Cross-sectional study. METHODS: 150 schoolchildren aged 7-18 years underwent comprehensive ophthalmic examinations, including cycloplegic refraction, and swept-source optical coherence tomography measurements. The thickness of the choroid, retina and nerve fiber layer were compared among children of different age groups. The topographic variation and factors related to the thickness of the choroid and retinal layers were analyzed. RESULTS:. Compared to emmetropic subjects, those with myopia had a significantly thinner choroid in all regions (P < .01), and emetropic subjects had a thicker choroid in most regions (P < .05). The myopic retinas were thinner than those of emmetropic subjects in the superior parafoveal and all 4 perifoveal subfields. The axial length and refractive diopters were independently related to central foveal choroidal thickness, while age and intraocular pressure were independently associated with central fovea retinal thicknesses CONCLUSIONS: Choroidal thickness, correlated closely with axial length and refractive diopters in myopic children. The retinal thickness of participants with myopia were lower than in those with emmetropia in the superior parafoveal and in both the superior and inferior perifoveal subfields. Keywords: Choroidal thickness; retinal thickness; myopia; SS-OCT. MYOPIA IS A GLOBAL PUBLIC HEALTH CONCERN. IT is estimated that one third of the world’s population may be affected by myopia by the year 2050(1). The pathophysiology of myopic progression is not well understood, although both genetic and environmental factors have been implicated in this Georgian Scientists/ . 5 N 4, 2023 354 apparent dysregulation of the emmetropization process (2, 3). The choroid, which may facilitate axial growth by modulating the remodeling of the scleral extracellular matrix (4, 5) has been implicated as playing an important role in the emmetropization of the eye during development. Few studies have described retinal and choroidal thickness in children with different refractive states (17–19) but none have studied both characteristics in the same cohort. Swept-Source optical coherence tomography (SSOCT) uses a long-wavelength swept light source to probe the amplitude and phase of backscattering of light from tissue. In this cross-sectional study, we investigated several retinal and choroidal characteristics, including the thickness of the retina and choroid using SSOCT in children aged 7-16 years, to elucidate the anatomic and topographic variations of the choroidal and retinal layers among myopic children. Materials and methods: All of the children understood the study protocol, and written informed consents were provided by their parents or other guardians. They were excluded if there was a self- reported history of intraocular surgery or pathology (retinopathy of prematurity, congenital glaucoma, congenital cataract, etc); the parents were unwilling or unable to give written informed consent; or the participant was unwilling or unable to give verbal informed assent. Each participant underwent comprehensive ophthalmic examinations, including visual acuity, sensorimotor examination, slit-lamp biomicroscopy, tonometry, cycloplegic refraction, and fundus examination. This was followed by ancillary testing, including axial length, corneal curvature measurements, and SSOCT. Visual acuity was measured using a retro illuminated Early Treatment Diabetic Retinopathy Study (ETDRS) chart at a distance of 4 m. Corneal curvature and refraction were determined using a desk-mounted auto-refractor (model KR-8900; Topcon, Tokyo, Japan). Spherical equivalent refraction (SER) was used to classify refractive status. Children were divided into 3 age groups: I. 7-12 age group; II 12-14 age group; III 14-18 age group. Each of them was divided into 3 groups according to the degree of myopia: low (-0,5-3,0); moderate (3,5-6.0) and high (6,5 and more). Control groups were also divided into 3 age groups. Intraocular pressure was measured using a icare. Axial length was measured using noncontact optical biometry (IOLMaster,) SSOCT (model DRI OCT-1 Atlantis; Topcon), with a lateral resolution of 10 mm and a depth resolution of 8 mm, was used to measure the thickness of choroid and retinal layers. The machine uses a 1050- nm-wavelength light source and has a scanning speed of 100 000 A-scans per second. The 12-line radial scan pattern with a resolution of 1024 3 12 was used. Each image was an average of 4 overlapped consecutive scans, which covered an area of 12 mm 3 9 mm, centered on the fovea. Built-in software was used to segment layers and construct topographic maps. Choroidal thickness was measured as the distance between the Bruch membrane and the choroid-sclera interface; retinal thickness was measured as the distance between the internal limiting membrane and the interface between photoreceptor outer segments and retinal pigment epithelium. (Figure 1) Georgian Scientists/ . 5 N 4, 2023 355 FIGURE 1. The cross-sectional and en face segmentation of choroidal, retinal, ganglion cell layer, and nerve fiber layer thickness measurements obtained by swept-source optical coherence tomography. (Top left) Choroidal thickness, the distance between the Bruch membrane and the choroid-sclera interface. (Top right) Retinal thickness, the distance between the internal limiting membrane and the interface between photoreceptor outer segments and retinal pigment epithelium. (Middle left) Ganglion cell layer thickness, the distance from the interface between the nerve fiber layer and ganglion cell layer to the interface between the inner plexiform layer and inner nuclear layer. (Middle right) Nerve fiber layer thickness, the distance between the internal limiting membrane and the interface between nerve fiber layer and ganglion cell layer. (Bottom) The Early Treatment Diabetic Retinopathy Study (ETDRS) grid: central foveal circle (diameter [1 mm), parafoveally circle (diameter [3 mm), and perifoveal circle (diameter [6 mm). The parafoveally region and the perifoveal region were further subdivided into sup A single technician performed all the SSOCT image acquisitions between 9 AM and 11 AM, to reduce the impact of diurnal variation. Images with signal strength below 60 were rejected and the test was repeated. On the first 20 participants, the SSOCT was performed twice in order to assess measurement reproducibility STATISTICAL ANALYSES: Choroid, retina and nerve fiber layer of each subfield Average thickness was calculated by Built software. Statistical processing. The results of the research were processed Georgian Scientists/ . 5 N 4, 2023 356 Using software statistical package. In each group Age, sex, axial axis, Data were considered statistically significant at p<0.05. The results were processed by Statistical for Windows Release 19.0. RESULTS: The average age of the participants involved in the study is 9.69±0.5 years. (Table 1.) The length of the anterior-posterior axis of the eye varied from 20.0 mm to 26.6 mm, spherical equivalent - from 9.00 D to þ 5.25 D, on average 0.15 -1.60 D. of the participants 120 had myopia and 30 had emmetropia. Compared to emmetropic subjects, myopic subjects had a longer axial axis. There was not noticed Statistical difference in central retinal thickness in subjects with myopia between the groups (Table 2), there was no significant difference by gender central foveal choroidal thickness (261± 65 nm vs 269± 68 nm, P=.37) and in terms of central foveal retinal thickness. (236 ± 25 nm vs 233 ± 27 nm, P=.13). No significant correlation was observed between age and central between choroidal thickness (P=.34). In the participants of the refractive status, the following was found: choroidal thickness increased from the nasal quadrant to the temporal quadrants. Horizontally, and vertically, the choroid was thicker in the parafoveal subfield than in the perifoveal field. The layers of the retina are more thicker in the nasal quadrant compared to the temporal. Compared to emmetropic participants, myopic subjects had. Significantly thinner choroid in all segments. Superior parafoveal, as well as Retinal thickness in upper and lower perifoveal subfields with myopia subjects had less, compared to emmetropes. According to the results of the research conducted by us, the retina and choroid thickness correlates strongly between SER and choroidal thickness in all In the region including the central fovea (R2 ¼ 0.11, P<.01), the parafoveal circle (R2 ¼ 0.11, P<.01) and perifoveal circle (R2 ¼ 0.11, P<.01). Positive A correlation was found between SER and perifoveal retinal thickness regions Table1. General Characteristics of the Participants and Comparison Among Refractive Groups parameter Total N=150 Myopic N=120 Emetropic N 30 P Age 9.70 ± 1.17 10.10± 1.09 9.85± 1.19 0.18 Axial length. mm 23.38± 0.99 24.17 ± 0.96 23.25± 0.72 0.1 0.2 Intraocular pressure, mm Hg 17.65± 3.05 17.56 ±2.50 17.19± 3.27 0.1 0.15 Refractive error, D 0.15 ±1.60 2.00 ± 1.45 0.18 ±0.26 0.1 Georgian Scientists/ . 5 N 4, 2023 357 TABLE 2. Topographic Characteristics of Choroid and Retina in Myopic and Emmetropic Subjects Subfield Layer High Myopia Moderate myopia Low Myopia Emmetropia P Central fovea Retina 234 ±22 231±22 232±23 232±23 0.18 Choroid 227±61 244±53 253±58 253±58 0.59 Parafoveal Nasal Retina 305±14 308±14 309±23 309±23 0.13 Choroid 199 ± 60 220±54 222 ± 56 222 ± 56 0.65 Parafoveal Temporal Retina 244 ±63 291±16 293±22 293±20 0.82 Choroid 242±62 244 ±63 266±56 267±57 0.49 Parafoveal Superior Retina 306 ±20 306±20 312±16 312±19 0.03 Choroid 225 6±63 228±63 250 ±55 250 ±55 0.06 Parafoveal Inferior Retina 301 - 18 301±18 304±20 298±22 0.13 Choroid 233±61 235 ±61 254 ±58 254 ±58 0.04 Perifovela Nasal Retina 285±20 285±20 291±24 296±21 <.01 Choroid 161 ± 51 165±51 177±50 177 ±50 <.01 Perifovel Temporal Retina 260 ±16 160±16 265±19 268±17 <.01 Choroid 250±54 252±55 271 ±6 52 271± 6 52 <.01 Perifoveal Superior Retina 272 ±13 272±13 280±17 281±20 <.01 Choroid 222 ± 59 224±60 249± 6 48 249 ±6 48 <.01 Perifoveal Inferior Retina 265 ±19 265±19 274±14 277±18 <.01 Choroid 224±53 226±54 244 ± 6 55 244 ±6 55 <.01 DISCUSSION OUR RESULTS INDICATED THAT MYOPIC CHILDREN HAD A thinner choroid in most areas and thinner retina in the superior quadrants and inferior perifoveal subfields. Central foveal choroidal thickness was closely correlated with axial length and refractive status. The mean central foveal choroidal thickness of myopic and emmetropic children in our study were 226 mm, 258 mm, and 272 mm, respectively, while a study of 104 Australian children (10-15 years old) reported a mean subfoveal Georgian Scientists/ . 5 N 4, 2023 358 choroidal thickness of 304 mm in myopic subjects and 360 mm in nonmyopic subjects(22). This discrepancy might be due to population differences, and is consistent with a prior report of Asians with myopia having thinner choroids than whites, Hispanics, and African Americans(23). The choroidal thickness of temporal areas is significantly thicker than that of the nasal areas, which is consistent with prior studies(24–26). Our findings indicated a close correlation between SER and choroidal thickness, and the central foveal choroidal thickness decreased with AL and SER, independently. This result was consistent with previous reports in both adult and pediatric patients.(5,17,22,24,27–33 ) The mean central foveal retinal thickness of the myopic participants in our study was 234 mm, which is very close to the 240 mm mean retinal thickness reported in a former study that was also conducted in Chinese children(35). The topography findings of retinal layers in our study I consistent with those of emmetropic and myopic adults in previous studies (12,26,36,37). Prior studies yielded conflicting data on retinal thickness in myopic subjects. While some studies have shown retinal thickness to be significantly decreased in myopic subjects,(38,39) other studies found it to be thicker in the central fovea but thinner in the parafoveal and perifoveal regions(.12,35,40,41) Moreover, some studies found no relationship between retinal thickness and SER, age, or axial lengths.(37,42) In our cohort, compared to emmetropic subjects, thinner retinal thickness was observed in myopic subjects in the superior parafoveal and perifoveal subfields and in the inferior perifoveal subfield. We found no relationship between subfoveal/parafoveal retinal thickness and either SER or AL, although subfoveal retinal thickness was seen to decrease with age and increase with IOP, which is consistent with previous studies performed in adult populations (37,38,43). The significance of these observations is unclear. While some suggested that the thickness of the ganglion cell layer and peripapillary nerve fiber layer is correlated with SER and AL in adults,44–48 others did not observe this relationship (49). In summary, our data suggest that in Chinese children, the thickness of the subfoveal choroid, but not the retina, correlates closely with SER and AL. The perifoveal retinal and ganglion cell layer thickness is less in myopic subjects than in emmetropic subjects. In the context of previous studies suggesting that choroidal changes precede scleral changes in induced ametropia, we propose that, during the early stage of myopia progression, choroid thinning occurs first. In conclusion, myopic children have a thinner choroid in all areas, and thinner retina in the superior and inferior perifoveal regions, than do their emmetropic counterparts. 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SS-OCTA DRI Triton CTARA- . , SER- AL- . , . , , , , , , . , SSOCT- , OCT . , OCT . , , . . : ; ; ; (SS-OCT).