Choroidal Thickness and Associated Factors among Adult Myopia: A Baseline Report from a Medical University Student Cohort

Animal models as windows into the pathogenesis of myopia: Illuminating new directions for vision health

The incidence of myopia, particularly high myopia, is increasing annually. Myopia has gradually become one of the leading causes of global blindness and is a considerable public-health concern. However, the pathogenesis of myopia remains unclear, and exploring the mechanism underlying myopia has become an urgent scientific priority. Creating animal models of myopia is important for studying the pathogenesis of refractive errors. This approach allows researchers to study and analyze the pathogenesis of myopia from aspects such as changes in refractive development, pathological changes in eye tissue, and molecular pathways related to myopia. This review summarizes the examples of animal models, methods of inducing myopia experimentally, and molecular signaling pathways involved in developing myopia-induced animal models. This review provides solid literature for researchers in the field of myopia prevention and control. It offers guidance in selecting appropriate animal models and research methods to fit their research objectives. By providing new insights and a theoretical basis for studying mechanisms of myopia, we detail how elucidated molecular pathways can be exploited to translate into safe and effective measures for myopia prevention and control.

Structural, blood flow and functional changes in the macular area and the expression of aqueous humor factors in myopia

Objective

To compare the macular area parameters and aqueous humor factors between myopia and emmetropia.

Methods

Convenience sampling was used to select patients who visited the Changzhi Aier Eye Hospital's department of ophthalmology from December 2018 to December 2022 as the study participants. They were divided into three groups according to whether they were diagnosed as mild myopia myopic, highly myopic or not as follows: the mild myopia group (60 cases, 108 eyes), the high myopia group (46 cases, 78 eyes) and the healthy emmetropia group (40 cases, 65 eyes). The differences in the macular integrity (MI) assessment, optical coherence tomography and optical coherence tomography angiography parameters and aqueous humor factors were compared between the three groups.

Results

AL in high myopia group was the highest, and that in emmetropia group was the lowest. The BCVA of mild myopia group was the highest. The RS in the high myopia group were significantly lowest in the three groups (26.42 ± 1.04 vs. 28.34 ± 0.76 vs. 31.92 ± 0.77) (F = 5.374, p = 0.013). The 63% BCEA, 95% BCEA and MI in the high myopia group were significantly highest (p < 0.05). The mean RPE thickness, mean CT and mean RT in the high myopia group were lowest (p < 0.05). The blood flow density were lowest in the superficial fovea, paracentral fovea and different subdivisions of the paracentral fovea in the high myopia group (p < 0.05). The VEGF concentration in the aqueous humor of the high myopia group was lowest (25.62 ± 17.43 vs. 32.45 ± 24.67 vs. 64.37 ± 21.14) (F = 9.237, p < 0.001). The MMP-2 concentration was highest (483 ± 201.48 vs. 410 ± 142.37 vs. 386 ± 154.34) (F = 5.542, p = 0.018). The VEGF concentration in the aqueous humor factor was negatively correlated with the AL in the myopia group (r = -0.438, p = 0.002), the MMP-2 concentration was positively correlated with the AL (r = 0.484, p = 0.010).

Conclusion

Patients with high myopia showed decreased retinal light sensitivity, fixation stability, superficial blood flow density and retinal thickness compared with people with emmetropia. A decreased VEGF concentration and increased MMP-2 concentration in the aqueous humor factor have potential associations with the development of high myopia.

Comparison of manual and artificial intelligence-automated choroidal thickness segmentation of optical coherence tomography imaging in myopic adults

BACKGROUND

Myopia affects 1.4 billion individuals worldwide. Notably, there is increasing evidence that choroidal thickness plays an important role in myopia and risk of developing myopia-related conditions. With the advancements in artificial intelligence (AI), choroidal thickness segmentation can now be automated, offering inherent advantages such as better repeatability, reduced grader variability, and less reliance for manpower. Hence, we aimed to evaluate the agreement between AI-automated and manual segmented measurements of subfoveal choroidal thickness (SFCT) using two swept-source optical coherence tomography (OCT) systems.

METHODS

Subjects aged ≥ 16 years, with myopia of ≥ 0.50 diopters in both eyes, were recruited from the Prospective Myopia Cohort Study in Singapore (PROMYSE). OCT scans were acquired using Triton DRI-OCT and PLEX Elite 9000. OCT images were segmented both automatically with an established SA-Net architecture and manually using a standard technique with adjudication by two independent graders. SFCT was subsequently determined based on the segmentation. The Bland-Altman plot and intraclass correlation coefficient (ICC) were used to evaluate the agreement.

RESULTS

A total of 229 subjects (456 eyes) with mean [± standard deviation (SD)] age of 34.1 (10.4) years were included. The overall SFCT (mean ± SD) based on manual segmentation was 216.9 ± 82.7 µm with Triton DRI-OCT and 239.3 ± 84.3 µm with PLEX Elite 9000. ICC values demonstrated excellent agreement between AI-automated and manual segmented SFCT measurements (PLEX Elite 9000: ICC = 0.937, 95% CI: 0.922 to 0.949, P < 0.001; Triton DRI-OCT: ICC = 0.887, 95% CI: 0.608 to 0.950, P < 0.001). For PLEX Elite 9000, manual segmented measurements were generally thicker when compared to AI-automated segmented measurements, with a fixed bias of 6.3 µm (95% CI: 3.8 to 8.9, P < 0.001) and proportional bias of 0.120 (P < 0.001). On the other hand, manual segmented measurements were comparatively thinner than AI-automated segmented measurements for Triton DRI-OCT, with a fixed bias of - 26.7 µm (95% CI: - 29.7 to - 23.7, P < 0.001) and proportional bias of - 0.090 (P < 0.001).

CONCLUSION

We observed an excellent agreement in choroidal segmentation measurements when comparing manual with AI-automated techniques, using images from two SS-OCT systems. Given its edge over manual segmentation, automated segmentation may potentially emerge as the primary method of choroidal thickness measurement in the future.

Peripapillary atrophy area predicts the decrease of macular choroidal thickness in young adults during myopia progression

OBJECTIVE

This study aimed to investigate the influence of peripapillary atrophy (PPA) area and axial elongation on the longitudinal changes in macular choroidal thickness (ChT) in young individuals with myopia.

METHODS AND ANALYSIS

In this longitudinal investigation, 431 eyes-342 categorised as non-high myopia (non-HM) and 89 as HM-were examined for 2 years. Participants were examined with swept-source optical coherence tomography. The macular ChT, PPA area and axial length (AL) were measured at baseline and follow-up visits. Multiple regression analysis was performed to identify factors associated with ChT changes. The areas under the receiver operating characteristic curves were analysed to ascertain the predictive capacity of the PPA area and axial elongation for the reduction in macular ChT.

RESULTS

Initial measurements revealed that the average macular ChT was 240.35±56.15 µm in the non-HM group and 198.43±50.27 µm in the HM group (p<0.001). It was observed that the HM group experienced a significantly greater reduction in average macular ChT (-7.35±11.70 µm) than the non-HM group (-1.85±16.95 µm, p=0.004). Multivariate regression analysis showed that a greater reduction of ChT was associated with baseline PPA area (β=-26.646, p<0.001) and the change in AL (β=-35.230, p<0.001). The combination of the baseline PPA area with the change in AL was found to be effective in predicting the decrease in macular ChT, with an area under the curve of 0.741 (95% CI 0.694 to 0.787).

CONCLUSION

Over 2 years, eyes with HM exhibit a more significant decrease in ChT than those without HM. Combining the baseline PPA area with the change in AL could be used to predict the decrease of macular ChT.

Correlation between refractive errors and ocular biometric parameters in children and adolescents: a systematic review and meta-analysis

BACKGROUND

Refractive errors are one of the most common ocular conditions among children and adolescents, with myopia showing an increasing prevalence and early onset in this population. Recent studies have identified a correlation between refractive errors and ocular biometric parameters.

METHODS

A systematic search was conducted in electronic databases including PubMed, EMBASE, Cochrane Library, Web of Science, and Medline from January 1, 2012, to May 1, 2023. Various ocular biometric parameters were summarized under different refractive states, including axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), corneal curvature (CC), Corneal curvature radius (CR),axial length-to-corneal radius ratio (AL/CR ratio), choroidal thickness (ChT), retinal thickness (RT), retinal nerve fiber layer thickness (RNFL), and retinal blood density (VD). The differences in these parameters among different refractive states were analyzed using Stata software with fixed or random-effects models, taking into account the assessed heterogeneity level.

RESULTS

This meta-analysis included a total of 69 studies involving 128,178 eyes, including 48,795 emmetropic eyes, 60,691 myopic eyes, 13,983 hyperopic eyes, 2,040 low myopic eyes, 1,201 moderate myopic eyes, and 1,468 high myopic eyes. The results of our study demonstrated that, compared to the control group (emmetropic group), the myopic group and low, moderate, and high myopic groups showed significant increases in AL, AL/CR ratio, and ACD, while the hyperopic group exhibited significant decreases. Compared to the control group, the myopic group had a significantly increase for CC, while CR, CCT, perifoveal RT, subfoveal ChT, foveal ChT, parafoveal ChT, perifoveal (except nasal) ChT, and pRNFL (except temporal) significantly decreased. Compared to the control group, the hyperopic group had a significantly increase for subfoveal ChT, foveal ChT, parafoveal ChT, perifoveal ChT, and nasal pRNFL. Compared to the control group, the low and moderate myopic groups had a significantly decreases for the CCT, parafoveal RT (except nasal), perifoveal RT (except nasal), and pRNFL (except superior and temporal). Compared to the control group, the high myopic group had a significantly increase for CR, while LT, perifoveal ChT (except nasal), parafoveal RT, perifoveal RT, and pRNFL (except temporal) had significant decreased.

CONCLUSION

The changes of ocular biometric parameters in children and adolescents are closely related to refractive errors. Ocular biometric parameters devices, as effective non-invasive techniques, provide objective biological markers for monitoring refractive errors such as myopia.

Pattern of choroidal thickness in early-onset high myopia

Purpose

To explore the etiology and choroidal thickness (ChT) pattern in children with early-onset high myopia (eoHM).

Methods

Sixty children with eoHM and 20 healthy controls were enrolled in this study between January 2019 and December 2021. All children underwent comprehensive ophthalmologic examinations including swept-source optical coherence tomography. ChT was measured in the subfoveal region and at 1000 μm and 2,500 μm nasal, temporal, superior, and inferior to the fovea.

Results

Overall, 120 eyes of 60 children with eoHM were examined (mean spherical equivalent, -8.88 ± 3.05 D; mean axial length, 26.07 ± 1.59 mm). Simple high myopia (SHM), familial exudative vitreoretinopathy (FEVR), and Stickler syndrome (STL) were the most frequent etiologies of eoHM and were included in further ChT analysis. Adjusted the effect of SE, multivariate regression analysis showed that children with SHM had thinnest ChT at N2500 and I2500 among the subgroups (p = 0.039, p = 0.013). FEVR group showed thinner ChT at T2500 (p = 0.023), while STL patients exhibited thin ChT at all locations.

Conclusion

This study revealed that SHM, STL and FEVR was the most frequent etiology, and showed a distinctive pattern of ChT. Asymmetric nasal ChT thinning is a distinctive biomarker for SHM, asymmetric temporal ChT thinning might serve as a biomarker for FEVR, and symmetric diffuse thinning is more common in STL. These ChT patterns may provide a convenient, fast, and noninvasive strategy to differentiate the potential etiology of eoHM.

Correlation between spherical equivalent and biometry parameters in adult Cynomolgus macaque

PURPOSE

To characterize the distribution of refractive and ocular biometry parameters and analyze the effect factors of the refractive status in cynomolgus monkey colonies.

METHODS

A Population-based cross-sectional study was conducted in adult cynomolgus macaque colonies. Animals were anesthetized with Zoletil 50. Intraocular pressure was measured using the Icare tonometer. Cycloplegic refraction (three drops of 1% tropicamide) and corneal radius of curvature (CRC) were measured using an autorefractor. The spherical equivalent (SE) was calculated. Biometric measurements, including the anterior chamber depth (ACD), lens thickness (LT), and axial length (AL), were obtained by A-scan ultrasonography. The AL-to-CR ratio (AL/CRC) was calculated. Central corneal thickness (CCT) and choroidal thickness (ChT) were measured using the Heidelberg Spectralis HRA OCT. Multiple regression analysis was performed to explore the association between refraction and ocular biometry.

RESULTS

Among 263 cynomolgus monkeys (aged 5-26 years), which consisted of 520 eyes, 29.42% had hyperopia, 27.12% had emmetropia, 33.27% had mild-to-moderate myopia and 10.19% had high myopia. The mean SE was -1.27 ± 3.44 Diopters (D). The mean CRC, CCT, AL, and ChT was 5.70 ± 0.22 mm, 454.30 ± 32.40 μm, 18.76 ± 0.89 mm and 188.96 ± 38.19 μm, respectively. The LT was the thickest in the hyperopic eyes. CRC was the lowest, and CCT was the thickest in high myopic eyes. AL increased, while ChT decreased as SE decreased. For the SE variance, AL alone explained 40.5%; age, AL, and CRC together explained 57.5%.

CONCLUSIONS

The refractive characteristics and biometry parameters of cynomolgus monkeys are highly comparable to those of humans. AL, CRC, and ChT showed the similar variation tendency in cynomolguses when compared to humans. Cynomolgus monkeys with naturally-occurring refractive errors may be a good animal model for refractive studies.

SubFoveal Choroidal Imaging in High Myopic Nepalese Cohort

Purpose

Evidence suggests that choroid is thinner in myopes as compared to nonmyopes. However, choroidal thickness varies with the refractive error, age, axial length, and ethnicity. The purpose of this study was to determine the subfoveal choroidal thickness (SFCT) in high myopic Nepalese subjects and to investigate its association with the mean spherical equivalent refractive error (MSE), axial length, and age.

Methods

Ninety-two eyes of 92 high myopic subjects (MSE ≤ -6 diopters) and 83 eyes of 83 emmetropic subjects (MSE: 0.00 Diopters) were included in the study. SFCT was assessed using spectral domain optical coherence tomography, and the axial length was measured using partial coherence interferometry. SFCT was measured manually using the inbuilt tool within the imaging software.

Results

SFCT in the high myopic subjects was significantly thinner (mean ± SD: 224.17 ± 68.91 μm) as compared to the emmetropic subjects (353.24 ± 65.63 μm) (mean difference, 127.76 ± 130.80 μm, and p < 0.001). In high myopic subjects, there was a significant negative correlation of choroidal thickness with the axial length (rho = -0.75; p < 0.001) and MSE (rho = -0.404; p < 0.01). Regression analysis demonstrated a decrease of choroidal thickness by 40.32 μm (p < 0.001) for every 1 millimeter increase in the axial length and by 11.65 μm (p < 0.001) for every 1 diopter increase in the MSE.

Conclusion

High myopic Nepalese subjects had significantly thinner choroid as compared to emmetropes. The MSE and axial length were inversely correlated with the SFCT. Age had no effect on SFCT in this study. These findings may have implications in interpreting choroidal thickness values in clinical and epidemiological studies in myopes, especially in the south Asian population.

The Incidence and Severity of Myopia in the Population of Medical Students and Its Dependence on Various Demographic Factors and Vision Hygiene Habits

(1) Background: Myopia is one of the leading causes of visual impairment. Visual work and usage of electronic devices are known risk factors of myopia. Many education systems were forced to apply online and hybrid teaching methods, to reduce the number of new cases of COVID-19. Medical students are a population well-known for intense visual work in the form of learning; (2) Methods: Visual acuity and refractive error were measured in the population of medical students. Participants also filled out the survey that included their population characteristic and their habits related to the hygiene of vision; (3) Results: We found a correlation between the age of the first diagnosis of myopia and current values of refractive error. The majority of participants believe that the COVID-19 pandemic had an impact on the health of their vision. Among methods of studying, usage of the computer screen was less preferred by myopic students; (4) Conclusions: In the population of medical school students in Eastern Poland, visual acuity was lower than 1.0 in 232 (52.97%) in the right eye and 234 (53.42%) in the left eye. Early recognition of refractive error has influenced its current values. Among methods of studying, usage of the computer screen was less preferred by myopic students. More population-based studies should focus on the impact of the COVID-19 pandemic on the health of vision.

Macular Choroidal Thickness and Choriocapillaris Vessel Density Alterations in Type 2 Diabetics with High Myopia

INTRODUCTION

The purpose of this study was to investigate the change in macular choroidal thickness and choriocapillaris vessel density in type 2 diabetic (T2D) with high myopia.

METHODS

This cross-sectional study recruited a total of 182 patients (182 eyes) in the Affiliated Hospital of Chengde Medical University between January 2018 and December 2021, including myopia + diabetes patients (40 eyes), T2D patients without myopia patients (47 eyes), myopia patients (45 eyes), and healthy volunteers (50 eyes). The choroidal thickness and choriocapillaris vessel density of macular were measured in all subjects by optical coherence tomography and optical coherence tomography angiography.

RESULTS

The choroidal thicknesses in myopic, diabetes, myopia + diabetes groups were statistically significantly lower than those in control group (p < 0.001). Further pairwise comparisons showed that the choroidal thicknesses in myopia + diabetes group were statistically significantly lower than those in diabetes group (p < 0.001). The choriocapillaris vessel densities in diabetes, myopia + diabetes groups were statistically significantly lower than those in control group (p < 0.001). Interestingly, there were no significant differences in choriocapillaris vessel density between myopia group and control group (p > 0.05). Further pairwise comparisons showed that the choriocapillaris thicknesses in myopia + diabetes group were statistically significantly lower than those in myopia group (p < 0.001), while no statistically significant differences were found between diabetes group and myopia + diabetes group (p > 0.05).

CONCLUSION

The choroidal thickness of the patients with high myopia and diabetes (without diabetic retinopathy [DR]) was significantly lower than that of normal people and diabetic patients, but the choriocapillaris vessel density was not significantly different from that of normal people, which may be one of the protective mechanisms of high myopia against DR.

Longitudinal choroidal thickness changes among Chinese young adults with various refractive errors

Purpose

To determine the characteristics of longitudinal choroidal thickness (CT) and axial length (AL) changes in a group of Chinese young adults with various refractive errors.

Methods

In this 2 year prospective cohort study, a total of 291 (314 enrolled at baseline) Chinese medical freshmen aged 18 to 22 years (mean age, 18.7 ± 0.9 years) underwent eye examinations at baseline and follow-up visits, including cycloplegic refraction, ocular biometry measurements, and swept-source optical coherence tomography. Choroidal thickness measurements were performed at nine locations in the macular area.

Results

At baseline, the CT and AL was significant differences among groups of emmetropia, mild to moderate myopia and high myopia. During a two-year period, there were significant differences found in the changes of the subfoveal CT (p < 0.001) and parafoveal CT of 7 locations between emmetropia and mild to moderate myopia, and the changes of the subfoveal CT (p = 0.002) and parafoveal CT of 6 locations between emmetropia and high myopia. But there were no differences for AL and SE (p > 0.05). The multivariable linear regression analysis showed that baseline subfoveal CT (per 1 μm) was a significant factor affecting the changes of subfoveal CT (p < 0.001), whereas age, gender, and baseline AL were not significantly associated.

Conclusion

The longitudinal change in CT varies with refractive errors in Chinese young adults aged 18 to 22 years over a two-year period. The changes of subfoveal CT were significantly associated with the baseline subfoveal CT, but not associated with baseline AL.

EFEMP1 is a potential biomarker of choroid thickness change in myopia

Purpose

To explore the possible molecular mechanism by which epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1) regulates choroid thickness (CT) in the development of myopia.

Methods

In total, 131 subjects were divided into the emmetropia (EM) group, non-high myopia (non-HM) group and high myopia (HM) group. Their age, refraction, intraocular pressure, and other ocular biometric parameters were collected. A 6 × 6 mm area centered on the optic disc was scanned by coherent optical tomography angiography (OCTA) to measure CT, and the tear concentrations of EFEMP1 were quantified using enzyme-linked immunosorbent assay (ELISA) analysis. Twenty-two guinea pigs were divided into the control group and the form-deprivation myopia (FDM) group. The right eye of the guinea pig in the FDM group was covered for 4 weeks, and the diopter and axial length of the right eye of the guinea pig were measured before and after the treatment. After the measurement, the guinea pig was euthanized, and the eyeball was removed. Quantitative reverse transcription polymerase chain reaction, western blotting assays and immunohistochemistry were used to assess the expression of EFEMP1 in the choroid.

Results

There were significant differences in CT among the three groups (p < 0.001). CT was positively correlated with age in HM (r = -0.3613, p = 0.0021), but no significant correlation with SE (p > 0.05) was observed. Furthermore, there were increased levels of EFEMP1 in the tears of myopic patients. After 4 weeks of covering the right eye of the FDM guinea pigs, there was a significant increase in axial length and a decrease in diopter (p < 0.05). The mRNA and protein expression of EFEMP1 was significantly increased in the choroid.

Conclusion

Choroidal thickness was significantly thinner in myopic patients, and the expression level of EFEMP1 in the choroid increased during the development of FDM. Therefore, EFEMP1 may be involved in the regulation of choroidal thickness in myopia patients.

Predicting Axial Length From Choroidal Thickness on Optical Coherence Tomography Images With Machine Learning Based Algorithms

Purpose

We formulated and tested ensemble learning models to classify axial length (AXL) from choroidal thickness (CT) as indicated on fovea-centered, 2D single optical coherence tomography (OCT) images.

Design

Retrospective cross-sectional study.

Participants

We analyzed 710 OCT images from 355 eyes of 188 patients. Each eye had 2 OCT images.

Methods

The CT was estimated from 3 points of each image. We used five machine-learning base algorithms to construct the classifiers. This study trained and validated the models to classify the AXLs eyes based on binary (AXL &lt; or &gt; 26 mm) and multiclass (AXL &lt; 22 mm, between 22 and 26 mm, and &gt; 26 mm) classifications.

Results

No features were redundant or duplicated after an analysis using Pearson’s correlation coefficient, LASSO-Pattern search algorithm, and variance inflation factors. Among the positions, CT at the nasal side had the highest correlation with AXL followed by the central area. In binary classification, our classifiers obtained high accuracy, as indicated by accuracy, recall, positive predictive value (PPV), negative predictive value (NPV), F1 score, and area under ROC curve (AUC) values of 94.37, 100, 90.91, 100, 86.67, and 95.61%, respectively. In multiclass classification, our classifiers were also highly accurate, as indicated by accuracy, weighted recall, weighted PPV, weighted NPV, weighted F1 score, and macro AUC of 88.73, 88.73, 91.21, 85.83, 87.42, and 93.42%, respectively.

Conclusions

Our binary and multiclass classifiers classify AXL well from CT, as indicated on OCT images. We demonstrated the effectiveness of the proposed classifiers and provided an assistance tool for physicians.

In vivo analysis of ciliary muscle in myopic Chinese young adults using ArcScan Insight® 100

OBJECTIVE

To analyse the morphological characteristics of the ciliary muscle (CM) and to explore its relationship with different ocular biometric parameters in myopic young Chinese adults.

METHODS

This observational, cross-sectional study included 50 right eyes from 50 myopic adults. The CM area (CMA), CM thickness (CMT) and CM length (CML) were measured using the ArcScan Insight^® 100. CMT was determined at three points: 1.0 mm (CMT-1), 2.0 mm (CMT-2) and 3.0 mm (CMT-3) posterior to the scleral spur. CML was measured on the scleral (CMLs) and vitreous (CMLv) aspects. The spherical equivalent refraction (SER), axial length (AL) and subfoveal choroidal thickness (SFCT) were examined to determine their associations with CM parameters (CMA, CML and CMT).

RESULTS

The mean SER and AL were -4.39 ± 2.29 D and 25.61 ± 1.15 mm, respectively. Compared with the nasal CMA, CML and CMT (CMT-1, CMT-2 and CMT-3) findings, the temporal CM parameters (CMA, CMLs, CMLv, CMT-1, CMT-2 and CMT-3) were found to be significantly thicker (all p < 0.001, except CMLv and CMT-1; p < 0.01). The nasal CMA was associated with the average corneal curvature (r = 0.30, p = 0.03) and SER (r = -0.30, p = 0.04). Nasal and temporal CMT-2 were negatively correlated with SER (r = -0.33 and -0.32, respectively, both p < 0.05). There was no correlation between CM parameters (except nasal CMLs, r = 0.31, p = 0.03) and SFCT, or between CM parameters and either the AL or anterior chamber depth (all p > 0.05).

CONCLUSION

These results suggest that there is temporal versus nasal asymmetry of the CM. CMA, CMT or CML did not vary with axial growth of the eye. The CM is not simply stretched as the eye elongates in myopic young adults.

Incidence of myopic shift and related factors in young Chinese adults

CLINICAL RELEVANCE

Myopia is a leading cause of visual impairment worldwide, and myopia progression in young adulthood may worsen this public health issue.

BACKGROUND

The aim was to describe the changes in myopia and various ocular biometry parameters, and to determine the incidence and related factors of myopic shift among young adults in China.

METHODS

This 2-year prospective cohort study was conducted at the Zhongshan Ophthalmic Center, Sun Yet-san University, China. A total of 291 Chinese medical freshmen (314 enrolled at baseline) were followed over 2 years. The participants underwent detailed eye examinations at baseline and follow-up visits, including cycloplegic refraction, ocular biometry measurements, and swept-source optical coherence tomography. Visual fatigue was assessed with the Convergence Insufficiency Symptom Survey (CISS) using Rasch analysis. Questionnaire on eye care habits and physical activities was administered.

RESULTS

A total of 291 study participants (baseline mean [SD] age, 18.7 [0.9] years; 132 [45.4%] male) were analysed. Seventy eight (26.8%) developed a myopic shift (defined as negative change in spherical equivalent worse than or equal to -0.50 D) over a 2-year period. The magnitude of subfoveal choroidal thinning was greater in participants with myopic shift, compared to those without. Axial length increased significantly by 0.12 mm in the group with myopic shift, compared to 0.02 mm in those without the myopic shift (p < 0.001) over 2 years. After multivariable adjustment, visual fatigue (using CISS) was found to be associated with the myopic shift (p = 0.02).

CONCLUSIONS

Approximately one in four Chinese medical students had a clinically significant myopic shift. Choroidal thinning and axial elongation were observed in young adults with myopic shift. Greater visual fatigue score at baseline was associated with myopic shift after multivariable adjustment.

Relationship between axial length and spherical equivalent refraction in Chinese children

Purpose

To evaluate the relationship between axial length (AL) and spherical equivalent refraction (SER) in Chinese children.

Methods

This hospital-based cross-sectional study included 1208 eyes (from 617 Chinese boys and 591 Chinese girls), ranging between 2 and 12 years. All subjects were divided into subgroups according to the spherical equivalent refraction (SER) (hyperopia, emmetropia, and myopia) and age (2-6 years, 7-9 years, and 10-12 years). Comparisons were made between age, sex, and SER groups. Multiple linear regression analysis was used to evaluate the correlation of AL and SER for all groups.

Results

The mean AL and SER were significantly different among the three age groups: 2-6 years group (AL: 22.24 ​± ​1.59 ​mm; SER: 0.73 ​± ​2.67 D); 7-9 years group (AL: 23.49 ​± ​1.10 ​mm; SE: -0.68 ​± ​1.97 D) and 10-12 years group (AL: 24.33 ​± ​1.02 ​mm; SER: -1.72 ​± ​1.86 D). Boys showed longer AL compared with the girls (23.66 ​± ​1.51 ​mm vs 23.05 ​± ​1.32 ​mm). However, as for SER, the girls (-0.70 ​± ​2.17 D) showed smaller SER (more myopia) compared with the boys (-0.4 ​± ​2.48 D). After adjusting for age and sex, the SER tended to decrease (became more myopic) 1.23 D (95% CI: 1.15-1.30D) with a 1 ​mm increase of AL. Among the different SER groups, the SER tended to become more myopic per mm of AL by 1.09 D (95% CI: 0.97-1.21D) for the myopia group, 1.38 D (95% CI: 1.23-1.54 D) for the hyperopia group, and 0.05 D (95% CI: 0.02-0.08 D) for the emmetropic group. In addition, an increase of 1 ​mm elongation of AL showed a decrease of SER by 1.05 D (95% CI: 0.90-1.20 D) among 2 - 6-year-olds, by 1.40 D (95% CI: 1.30-1.51 D) among 7 - 9-year-olds, and by 1.37 D (95% CI: 1.21-1.52 D) among 10-12-year-olds. As for sexual differences, the girls 1.68 D, (95% CI: 1.57-1.79 D) showed a more significant myopic shift of SER with a 1 ​mm increase of AL compared with the boys (0.94 D, 95% CI: 0.84-1.04 D).

Conclusions

Our results indicated a strong linear relationship between SER and AL and an early-rising trend of myopia in Chinese children.

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.

Thickness, vessel density of retina and choroid on OCTA in young adults (18-24 years old)

PURPOSE

The purpose of this study was to quantify thickness, vessel density (VD) of retina and choroid in young adults (18-24 years old) using OCTA.

METHODS

This observational, cross-sectional study included 154 eyes from 77 young myopic adults. En-face angiogram OCTA was performed on a 3.00 × 3.00 mm region centered on the macula. Automated thickness calculations and macular maps were measured. Spherical equivalent refraction (SER) and AL were examined to determine associations with thickness, vessel density (VD) of retina and choroid.

RESULTS

A total of 148 healthy eyes from 77 young myopic adults (29 males and 48 females) with a mean age of 21.80 ± 1.32 years (range: 18-24 years) were included. The mean SER and AL were - 4.06 ± 2.26D and 25.25 ± 1.28 mm, respectively. The mean retinal thickness (RT, ILM-RPE layer) was 240.91 ± 13.36 μm, the retinal superficial (SVD) and deep vessel density (DVD) in fovea region were 18.35 ± 4.77% and 32.99 ± 6.01%, respectively. The foveal avascular zone (FAZ) area was 0.31 ± 0.10 mm². The mean subfoveal choroidal thickness (SFCT) and choriocapillaris (CC) perfusion area were 232.16 ± 56.65 μm and 2.17 ± 0.10 mm², respectively. By Pearson's correlation analysis, SER was revealed to be negatively correlated with RT (r = -0.180, p = 0.028) and DVD (r = -0.185, p = 0.025) in fovea region. SER was revealed to be positively correlated with RT in nasal (r = 0.224, p = 0.006) and inferior (r = 0.217, p = 0.008) regions. AL was revealed to be positively correlated with RT (r = 0.250, p = 0.002) and DVD (r = 0.284, p < 0.001) in fovea region. SER was revealed to be positively correlated with SFCT (r = 0.486, p < 0.001). AL was revealed to be negatively correlated with FAZ area (r = -0.232, p = 0.005) and SFCT (r = -0.407). RT was revealed to be negatively correlated with FAZ area (r = -0.645, p < 0.001). SER (r = -0.079), AL (r = 0.071) and SFCT (r = 0.089) did not correlate significantly with the CC perfusion area (all p > 0.05).

CONCLUSION

Myopic eyes present increased RT, DVD and thinned SFCT in fovea, while no significant correlation could be found between SER, AL, SFCT and CC perfusion area. It may indicate that the SFCT thinning may be secondary to ocular elongation, while the CC perfusion area may be a factor independent of AL growth.

A comparison of choroidal thicknesses between pachychoroid and normochoroid eyes acquired from wide-field swept-source OCT

PURPOSE

We investigated the wide-field choroidal thickness (CT) using swept-source optical coherence tomography (SS-OCT) and compared the characteristics of the choroidal layer between pachychoroid and normochoroid groups.

METHODS

A total of 120 eyes from 120 normal subjects were included. All subjects were divided into two groups according to the subfoveal CT (≥300 μm, pachychoroid group; <300μm, normochoroid group). All subjects underwent an HD spotlight 16 mm scan using SS-OCT. The CT was measured at the following 12 points: subfoveal, 3 points in the nasal peripapillary area, 6 points in the macular area and 2 peripheral points at 5400 and 8100 µm from the fovea. The CT measurements were compared between the two groups, and statistical analyses were performed to determine clinical factors associated with each point of the CT.

RESULTS

The CT in the pachychoroid group was thicker than that in the normochoroid group at all points (p < 0.01). The CTs of the two groups in the macular area were highly associated with the subfoveal CT. However, the CTs of the nasal peripapillary and peripheral areas showed lower associations with the subfoveal CT and lower diagnostic abilities for the pachychoroid group. The existence of pachyvessels was found to be a significant factor causing the regional variations.

CONCLUSIONS

The CTs in the peripapillary and peripheral areas showed different patterns than the subfoveal CT. Regional variations by pachyvessels were more frequent in the peripapillary and peripheral areas than in the macular area, and the subfoveal CT did not represent the whole choroidal area.