Choroidal thickness in school children: The Gobi Desert Children Eye Study

Morphological and Morphometric Analysis of Canine Choroidal Layers Using Spectral Domain Optical Coherence Tomography

The choroid, a multifunctional tissue, has been the focus of research interest for many scientists. Its morphology and morphometry facilitate an understanding of pathological processes within both the choroid and retina. This study aimed to determine the choroidal layer thicknesses in healthy, mixed-breed mesocephalic dogs, both male (M) and female (F), using spectral domain optical coherence tomography (SD-OCT) with radial, cross-sectional, and linear scans. The dogs were divided into two groups based on age: middle-aged (MA) and senior (SN). Thicknesses of choroidal layers, namely RPE-Bruch's membrane-choriocapillaris complex (RPE-BmCc) with tapetum lucidum in the tapetal fundus, the medium-sized vessel layer (MSVL), and the large vessel layer with lamina suprachoroidea (LVLS), as well as whole choroidal thickness (WCT), were measured manually using the caliper function integrated into the OCT software. Measurement was performed dorsally and ventrally at a distance of 5000-6000 μm temporally and nasally at a distance of 4000-7000 μm to the optic disc on enhanced depth scans. The measurements were conducted temporally and nasally in both the tapetal (temporal tapetal: TempT, nasal tapetal: NasT) and nontapetal (temporal nontapetal: TempNT, nasal nontapetal: NasNT) fundus. The ratio of the MSVL thickness to the LVLS thickness for each region was calculated. In all examined dogs, the RPE-BmCc in the dorsal (D) region and MSVL in the Tt region were significantly thicker than those in the other regions. The MSVL was thinner in the ventral (V) region than in the D, TempT, TempNT and NasT regions. The MSVL was significantly thinner in the NasNT region than in the D region. LVLS thickness and WCT were significantly greater in the D and TempT regions than those in the other regions and significantly lesser in the V region than those in the other regions. The MSVL-to-LVLS thickness ratio did not differ between the age groups. Our results reveal that the choroidal thickness profile does not depend on age. Our findings can be used to document the emergence and development of various choroidal diseases in dogs in the future.

The influence of the choroid on the onset and development of myopia: from perspectives of choroidal thickness and blood flow

Myopia is the most common type of refractive errors characterized by excessive elongation of the ocular globe. With the increasing prevalence of myopia, improved knowledge of factors involved in myopia development is of particular importance. There are growing evidence suggesting that the choroid plays an important role in the regulation of eye growth and the development of myopia. Studies have demonstrated that thinning choroid is a structural feature of myopia, with a negative correlation between choroidal thickness and axial length, suggesting that the change in choroidal thickness may be a predictive biomarker for long-term changes in ocular elongation. Given the fact that the choroid is primarily a vascular structure capable of rapidly changing blood flow, variations of choroidal thickness might be primarily caused by changes in choroidal blood flow. Considering that hypoxia is associated with myopia and choroidal blood flow is the main source of oxygen and nourishment supply, apart from the effect on myopia possibly by changing choroidal thickness, decreasing choroidal blood flow may contribute to scleral ischaemia and hypoxia, resulting in alterations in the scleral structure and thus leading to myopia. This review aims to provide an overview of recent work exploring the influence of the choroid on myopia from perspectives of choroidal thickness and blood flow, which may present new predictive indicators for the onset of myopia and new targets for the development of novel therapeutic approaches for myopia.

Morphometrical analysis of the canine choroid in relation to age and sex using spectral domain optical coherence tomography

This study determined the choroidal thickness of senior (SN, n = 24) and middle-aged (MA, n = 17) healthy, mixed-breed mesocephalic dogs, both males (M) and females (F), using spectral domain optical coherence tomography (SD-OCT). The dogs were divided into two groups for examination: MA dogs (4-7 years old; 6 M, 11 F) and SN dogs (8-13 years old; 12 M, 12 F). Choroidal thickness of the dogs was investigated using SD-OCT radial and linear scans. The software of the device allowed determination of the exact measurement location on the choroid. Measurements of the choroid were taken manually using the SD-OCT calliper function at distances of 5,000-6,000 μm (dorsal and ventral) and 4,000-7,000 μm (nasal and temporal) from the optic disc. Mean (µm ± SD) (MA, SN) dorsal (188 ± 28, 184 ± 33), ventral (116 ± 23, 111 ± 16), temporal (152 ± 31, 151 ± 26), and nasal (135 ± 27, 132 ± 18) choroidal thicknesses demonstrated significant differences (P < 0.02-0.001) between all areas within each group. The choroid was thickest in the dorsal region and thinnest in the ventral region. There were no significant differences based on age. Mean (µm ± SD) (M, F) dorsal (181 ± 32, 190 ± 30), ventral (117 ± 16, 11 ± 21), temporal (150 ± 26, 153 ± 30), and nasal (128 ± 20, 138 ± 23) choroidal thicknesses demonstrated significant differences (P < 0.05) between dorsal and nasal regions. The choroidal thickness in dogs depends on the area assessed independently of their age and sex.

Challenges in Eye Care in the Asia-Pacific Region

The Asia-Pacific region is home to a 4.3-billion population and one of the most rapidly aging regions. Addressing the eye care needs in the region would greatly boost the progress toward achieving universal eye health. Over 20 countries/regions have actively engaged in the "VISION 2020" initiative launched since 1999, and remarkable achievements have been witnessed as demonstrated by an increase in both the number and density of ophthalmologists in almost all countries. Nevertheless, formidable and emerging challenges are to be overcome in the coming century. From 1990 to 2015, the absolute number of blind people increased by 17.9%, largely due to population growth and aging. The Asia-Pacific region, the most populous continent with a rapidly aging population, would inevitably be left to tackle this challenge. Furthermore, a high prevalence of blinding eye diseases imposes great pressure on current eye care services, with South Asia having the highest age-standardized prevalence of moderate to severe visual impairment (17.5%) and mild vision impairment (12.2%) globally, and high-income countries having the highest overall prevalence of myopia, reaching 53.4% with East Asia having the second-highest overall prevalence (51.6%). Moreover, the availability of ophthalmic resources varies greatly in the region, with the density of ophthalmologists ranging from over 114 ophthalmologists per million population in Japan to 0 in Micronesia, and a highly disproportionate urban-rural distribution. This article aims to shed light on challenges faced by the Asia-Pacific ophthalmic community and propose corresponding strategies to tackle those challenges.

Choroidal, macular and ganglion cell layer thickness assessment in Caucasian children measured with spectral domain optical coherence tomography

PURPOSE

To study the subfoveal choroidal thickness (SFCT), macular ganglion cell layer (GCL-IPL) and central macular thickness (CMT) in Caucasian children, and to analyze these optical coherence tomography (OCT) parameters depending on the spherical equivalent (SE).

METHODS

Cross-sectional study of SFCT, GCL-IPL, and CMT in Caucasian children, analyzed with spectral-domain OCT Cirrus 5000 and Enhanced-depth imaging technique. Correlation between these three OCT parameters, age, sex, and spherical equivalent was analyzed. The eyes were classified into three groups: group 1 included eyes with SE < 0, group 2 included eyes with SE between 0 and +2.00, and group 3 eyes with SE > +2.00.

RESULTS

Hundred ninety-eight eyes of 121 subjects were studied. The mean age was 9.22 years (range 3-16); 61.1% were female. The mean SFCT was 351.04 ± 84.08 µm, being 310.04 ± 82.84µm in group 1 (n = 62), 373.14 ± 83.16 µm in group 2 (n = 71) and 365.18 ± 73.16 µm in group 3 (n = 65); statistically significant differences were found between groups 2 and 3, compared with group 1. GCL-IPL thickness was significantly thinner (p < 0.001) in group 1, compared with group 3. There were no statistically significant differences between the three groups regarding CMT. Correlation with age, and sex was not found.

CONCLUSIONS

SFCT and GCL-IPL thickness were significantly thinner (p < 0.001) in myopic children when compared with a non-myopic pediatric population. However, it seems that there is not a correlation among the three OCT parameters studied, age and sex, when they are analyzed depending on refractive error.

[Choroid and optical defocus]

The review summarizes experimental and clinical data attesting to the important role the choroid plays in the development of refraction through optically oriented thickness changes and the release of growth factors. Because of its unique anatomical position, the choroid can influence the transmission of a cascade of chemical signals from the retina to the sclera and thereby affect the growth of the eye. Understanding the relationship between the optical defocus and the response of the choroid to it will help uncover the fundamental mechanisms for controlling eye growth and develop new strategies for preventing the progression of myopia.

Five-Year Change in Choroidal Thickness in Relation to Body Development and Axial Eye Elongation: The CCC2000 Eye Study

Purpose

We describe changes in choroidal thickness from age 11 to 16 years and its association with ocular biometrics and body development.

Method

In this longitudinal, population-based observational study, choroidal thickness was measured subfoveally and 1- and 3-mm temporal thereof using enhanced depth imaging spectral domain optical coherence tomography. Analyses were stratified by sex and adjusted for age and the time of day that the scan was performed.

Results

The study included 687 participants (304 boys). Median (interquartile range [IQR]) age was 11.5 (0.6) years at baseline and 16.6 (0.3) years at follow-up. Mean increase in choroidal thickness was 33, 27, and 11 μm at the three respective locations. The subfoveal choroid thickened less in eyes whose axial length increased more (boys, β = -85 μm/mm; 95% confidence interval [CI], -104 to -66, P < 0.0001; girls, β = -105 μm/mm; 95% CI, -121 to -89, P < 0.0001) and in eyes with a more negative refractive development (boys, 11 μm/diopters [D]; 95% CI, 4.0 to 18, P = 0.0022; girls, 22 μm/D; 95% CI, 16 to 27, P < 0.0001). Subfoveal choroidal thickness increased less in girls who underwent early puberty (Tanner stage 4 vs. 1; -39 μm' 95% CI, -72 to -5.9, P = 0.021) and who had a longer baseline axial length (β = -8.6 μm/mm; 95% CI, -15 to -2.7, P = 0.0043), and more in girls who grew taller (β = 0.9 μm/cm; 95% CI, 0.1 to 1.7, P = 0.026).

Conclusions

The choroid increased in thickness from age 11 to 16 years. The increase was greater in girls with later sexual maturation and smaller in eyes that added more axial length and had a relatively negative refractive development.

Retinal Nerve Fiber Layer Thickness in Children: The Gobi Desert Children Eye Study

Purpose

Because there is a paucity of population-based data on retinal nerve fiber layer thickness (RNFLT) for children, we measured the RNFLT and its associations in schoolchildren.

Methods

The population-based Gobi Desert Children Eye Study included all schoolchildren aged 6 to 21 years living in Ejina, Inner Mongolia. The children underwent a comprehensive ocular examination with cycloplegic refractometry and spectral-domain optical coherence tomography of the optic nerve head. The peripapillary RNFLT was measured on the optical coherence tomography images of a circular scan with a diameter of 3.4 mm.

Results

Out of 1565 participants, RNFLT data were available for 1440 (92.5%) children. The mean global RNFLT was 101.3 ± 9.2 μm in right eyes. The RNFLT was thickest in the temporal inferior sector (157.3 μm), followed by the temporal superior sector (143.8 μm), the nasal inferior sector (109.7 μm), the nasal superior sector (106.9 μm), temporal sector (85.2 μm), and the nasal sector (61.7 μm). In multivariate analysis, the RNFLT decreased with higher myopic refractive error (P < 0.001), male sex (P = 0.001), higher intraocular pressure (P = 0.002), and lower birth weight (P = 0.03). It was not significantly associated with age (P = 0.19), body mass index (P = 0.57), mean arterial blood pressure (P = 0.33), pulse rate (P = 0.28), and subfoveal choroidal thickness (P = 0.11).

Conclusions

The RNFLT in children showed a regional distribution, with the thickest part in the temporal inferior sector and the thinnest part located in the nasal sector. The overall RNLFT significantly decreased with higher myopic refractive error and male sex. In schoolchildren, in contrast to adults, the RNFLT did not decrease with older age. These findings may be considered when interpreting RNFLT data in children.

Wide-field choroidal thickness in myopes and emmetropes

There is a paucity of knowledge regarding the normal in-vivo thickness of the choroid beyond the macula (~17°). In this study, the choroidal thickness of 27 healthy young adults was examined across the macular (the central 5 mm including the fovea, parafovea, and perifovea) and extra-macular (a 5–14 mm annulus including the near-periphery and periphery) regions using wide-field optical coherence tomography, and compared between emmetropes (n = 14) and myopes (n = 13). The choroid progressively thinned beyond the parafovea (350 ± 86 µm) towards the periphery (264 ± 44 µm), and was thickest superiorly (355 ± 76 µm) and thinnest nasally (290 ± 79 µm). Choroidal thickness also varied with refractive error; myopes exhibited a thinner choroid than emmetropes in the macular region (311 ± 88 vs. 383 ± 66 µm), however, this difference diminished towards the periphery (251 ± 48 vs. 277 ± 37 µm). Meridional variations in choroidal thickness were not different between myopes and emmetropes. In conclusion, the choroid was thickest within the perifovea; thinned substantially towards the periphery, and exhibited the minimum and maximum peripheral thinning superiorly and nasally across a 55° region respectively. Choroidal thinning associated with myopia was more pronounced in the macular than extra-macular regions.