The effect of topical administration of cyclopentolate on ocular biometry: An analysis for mouse and human models

Effect of Cycloplegia on Anterior Segment Structures and Scleral Thickness in Emmetropic Eyes

Purpose: To evaluate the effects of topical cyclopentolate hydrochloride-induced cycloplegia on anterior segment biomechanics in emmetropic eyes using anterior segment-optical coherence tomography (AS-OCT). Methods: Twenty-five emmetropic eyes of 25 volunteers were included. All underwent central corneal thickness (CCT) and anterior chamber depth (ACD) measurements. Anterior scleral thickness (AST) was measured at the level of the scleral spur (SS)(AST-0), 1,000 μm posterior of the SS (AST-1), and 2,000 μm posterior of the SS (AST-2) in the nasal and temporal quadrants using AS-OCT. All measurements were repeated after cycloplegia. Results: The mean age was 30.6 ± 12.4 (8-45) years. The mean CCT did not significantly change after cycloplegia (P = 0.7). The mean ACD was significantly increased [3.3 ± 0.2 (2.7-3.9) to 3.7 ± 0.3 (3-4.2) μm; P = 0.001]. In the nasal quadrant, the mean AST-1 and AST-2 were 512.3 ± 34.4 (433-570) and 529.6 ± 34.2 (449-599); decreased to 478 ± 26.8 (423-530) and 486.2 ± 28.3 (422-544) μm, respectively, after cycloplegia (P = 0.00; P = 0.00). In the temporal quadrant, the mean AST-1 and AST-2 were 522.5 ± 24.7 (473-578) and 527.2 ± 39.9 (450-604); decreased to 481.1 ± 33.7 (421-550) and 484.6 ± 26.6 (433-528) μm, respectively (P = 0.00; P = 0.00). There was no significant difference in AST-0 after cycloplegia in both quadrants [from 697.5 ± 46 (605-785) to 709.5 ± 64.7 (565-785) for nasal and from 718.4 ± 40.1 (632-796) to 722.9 ± 60.6 (596-838) for temporal; P = 0.2; P = 0.3, respectively]. Conclusion: After cycloplegia, there was a significant thinning of ASTs posterior to SS and a slight increase in AST in the SS level. ACD deepened after cycloplegia, and there was no significant change in CCT. Cycloplegic agents temporarily inhibit ciliary muscle contraction and may affect anterior segment parameters and sclera. Inhibition of forward-inward movement of the ciliary body by cycloplegia affects ASTs and ACD by causing a change in the mechanical force of the ciliary muscle on the sclera.

Two-year longitudinal change in choroidal and retinal thickness in school-aged myopic children: exploratory analysis of clinical trials for myopia progression

Background

With increasing axial length and myopia progression, the micro-structure of the retina and choroid gradually changes. Our study describes the longitudinal changes in retinal and choroidal thickness in school-aged children with myopia and explores the relationship between changes in choroidal thickness and myopia progression.

Methods

An exploratory analysis of a randomized trial was performed. Children (n = 168, aged 7 to 12 years) with myopia from − 0.75 dioptre (D) to − 4.00 D were enrolled in this prospective longitudinal study. Cycloplegic refraction, axial length (AL), retinal and choroidal thicknesses were measured at baseline and at 1- and 2-year follow-ups. “Rapid progression myopia” was defined as increasing in myopia > 1.00 D and “stable progression myopia” was ≤ 1.00 D during the 2-year follow-up. Factors affecting the changes in choroidal thickness were analysed using linear mixed models.

Results

AL significantly increased by 0.67 ± 0.24 mm with a myopic shift of − 1.50 ± 0.64 D over the 2 years. The overall retinal thickness increased from 251.12 ± 15.91 µm at baseline to 253.47 ± 15.74 µm at the 2-year follow-up (F = 23.785, P < 0.001). The subfoveal choroidal thickness decreased from 231.03 ± 54.04 µm at baseline to 206.53 ± 59.71 µm at the 2-year follow-up (F = 73.358, P < 0.001). Choroidal thinning was significantly associated with AL elongation (β =  − 43.579 μm/mm, P = 0.002) and sex (β =  − 17.258, P = 0.001). Choroidal thickness continued to decrease in subjects with rapid progression (F = 92.06, P < 0.001) but not in those with steady progression (F = 2.23, P = 0.119).

Conclusion

Significant choroidal thinning was observed and was associated with rapid progression and sex. These findings indicate a need to understand the role of the choroid in eye growth and myopia development.

Synopsis/Precis

The macular choroidal thickness of myopic children is relevant to different degrees of myopic progression in this 2-year longitudinal study. These findings suggest that control of choroidal thickness might work to regulate human ocular growth.

Trial registration Chinese Clinical Trial Register (ChiCTR): ChiCTR-INR-16007722

Comparison of the Effects of Orthokeratology Lens and Cyclopentolate on Myopia Progression in Children

Purpose: To compare the effects of orthokeratology lens (Ortho‐K lens) and topical cyclopentolate on myopia progression in children. Methods: This retrospective study analyzed the medical records of 36 children who received Ortho‐K lens and 28 who received cyclopentolate (i.e., total of 64 eyes). The following data were recorded: sex, age, age at first intervention, follow‐up duration, and visual acuity and axial length (AL) at the time of first treatment and after 6, 12, and 24 months of treatment. Results: In the Ortho‐K group, the changes of AL significantly decreased by 0.3 ± 0.25 mm at 12 months and 0.52 ± 0.34 mm at 24 months (p for trend < 0.001). In the cyclopentolate group, the changes of AL significantly decreased by 0.36 ± 0.17 mm at 12 months and 0.62 ± 0.29 mm at 24 months (p for trend = 0.022). Compared to the use of cyclopentolate, the use of Ortho‐K lens resulted in smaller changes in AL during follow‐up (p = 0.038). Conclusions: In myopic children, Ortho‐K reduced myopia progression, whereas cyclopentolate significantly less affect myopia progression than Ortho‐K lens.

Increased Choroidal Blood Perfusion Can Inhibit Form Deprivation Myopia in Guinea Pigs

Purpose

In guinea pigs, choroidal thickness (ChT) and choroidal blood perfusion (ChBP) simultaneously decrease in experimental myopia, and both increase during recovery. However, the causal relationship between ChBP and myopia requires further investigation. In this study, we examined the changes of ChBP with three different antimyopia treatments. We also actively increased ChBP to examine the direct effect on myopia development in guinea pigs.

Methods

Experiment 1: Guinea pigs wore occluders on the right eye for two weeks to induce form-deprivation myopia (FDM). Simultaneously they received daily antimyopia treatments: peribulbar injections of atropine or apomorphine or exposure to intense light. Experiment 2: The vasodilator prazosin was injected daily into the form-deprivation eyes to increase ChBP during the two-week induction of FDM. Other FDM animals received appropriate control treatments. Changes in refraction, axial length, ChBP, ChT, and hypoxia-labeled pimonidazole adducts in the sclera were measured.

Results

The antimyopia treatments atropine, apomorphine, and intense light all significantly inhibited myopia development and the decrease in ChBP. The treatments also reduced scleral hypoxia, as indicated by the decrease in hypoxic signals. Furthermore, actively increasing ChBP with prazosin inhibited the progression of myopia, as well as the increase in axial length and scleral hypoxia.

Conclusions

Our data strongly indicate that increased ChBP attenuates scleral hypoxia, and thereby inhibits the development of myopia. Thus ChBP may be a promising target for myopia retardation. As such, it can serve as an immediate predictor of myopia development as well as a long-term marker of it.

IMI Accommodation and Binocular Vision in Myopia Development and Progression

The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.

Agreement Between Retinoscopy, Autorefractometry and Subjective Refraction for Determining Refractive Errors in Congolese Children

OBJECTIVE

To assess the agreement between retinoscopy and autorefractometry and between subjective refraction and both retinoscopy and autorefractometry in Congolese children.

PATIENTS AND METHODS

Fifty-four children (6-17 years old) were enrolled consecutively in this cross-sectional study. Refraction was evaluated before and after cycloplegia (1% cyclopentolate) with retinoscopy and autorefractometry. Readings were compared (paired t-test) and agreement assessed with Bland-Altman plots. Subjective refraction was compared with the two methods to determine which one provides better reference estimates for subjective refraction.

RESULTS

Under cycloplegia, the spherical power was comparable between retinoscopy and autorefractometry (1.12 ± 1.37 D vs 1.22 ± 1.06D, P = 0.70), cylinder power was significantly more myopic on retinoscopy than autorefractometry (0.80 ± 1.10D vs -0.62 ± 0.66, P = 0.019), and SE was greater on autorefractometry than retinoscopy (0.91 ± 1.10D vs 0.72 ± 1.00D, P = 0.014). Retinoscopy and autorefractometry overestimated the power of spherical (P = 0.022 and 0.002, respectively) and cylindrical components (all P < 0.001). There was an agreement between retinoscopy and autorefractometry in measuring spherical (bias: 0.09 ± 0.16D; limit of agreement, LoA: -0.40 to 0.22D) and cylindrical power (bias: -0.18 ± 0.20D; LoA: -0.57 to 0.21D). Subjective refraction agreed with cycloplegic retinoscopy for determining SE power (bias: 0.11D; LoA: -0.51 to 0.73D).

CONCLUSION

Retinoscopy and autorefractometry can be used interchangeably in children for determining the power of spherical and cylindrical components. Cycloplegic retinoscopy is better than autorefractometry to obtain SE reference values for subjective refraction in children.

Scleral HIF-1α is a prominent regulatory candidate for genetic and environmental interactions in human myopia pathogenesis

BACKGROUND

Myopia is a good model for understanding the interaction between genetics and environmental stimuli. Here we dissect the biological processes affecting myopia progression.

METHODS

Human Genetic Analyses: (1) gene set analysis (GSA) of new genome wide association study (GWAS) data for 593 individuals with high myopia (refraction ≤ -6 diopters [D]); (2) over-representation analysis (ORA) of 196 genes with de novo mutations, identified by whole genome sequencing of 45 high-myopia trio families, and (3) ORA of 284 previously reported myopia risk genes. Contributions of the enriched signaling pathways in mediating the genetic and environmental interactions during myopia development were investigated in vivo and in vitro.

RESULTS

All three genetic analyses showed significant enrichment of four KEGG signaling pathways, including amphetamine addiction, extracellular matrix (ECM) receptor interaction, neuroactive ligand-receptor interaction, and regulation of actin cytoskeleton pathways. In individuals with extremely high myopia (refraction ≤ -10 D), the GSA of GWAS data revealed significant enrichment of the HIF-1α signaling pathway. Using human scleral fibroblasts, silencing the key nodal genes within protein-protein interaction networks for the enriched pathways antagonized the hypoxia-induced increase in myofibroblast transdifferentiation. In mice, scleral HIF-1α downregulation led to hyperopia, whereas upregulation resulted in myopia. In human subjects, near work, a risk factor for myopia, significantly decreased choroidal blood perfusion, which might cause scleral hypoxia.

INTERPRETATION

Our study implicated the HIF-1α signaling pathway in promoting human myopia through mediating interactions between genetic and environmental factors.

FUNDING

National Natural Science Foundation of China grants; Natural Science Foundation of Zhejiang Province.

Changes in Choroidal Thickness and Choroidal Blood Perfusion in Guinea Pig Myopia

Purpose

The purpose of this study was to study changes in choroidal thickness (ChT) and choroidal blood perfusion (ChBP), and the correlation between them, in guinea pig myopia.

Methods

The reliability of optical coherence tomography angiography (OCTA) for measuring ChT and ChBP was verified in guinea pigs, after cervical dislocation (n = 7) or temporal ciliary artery transection (n = 6). Changes in refraction, axial length, ChT, and ChBP were measured during spontaneous myopia (n = 9), monocular form-deprivation myopia (FDM, n = 13), or lens-induced myopia (LIM, n = 14), and after 4 days of recovery from FDM and LIM.

Results

The abolition (by cervical dislocation) or reduction (by temporal ciliary artery transection) of ChBP, and of the associated changes in ChT, were verified by OCTA, thus validating the method of measurement. In the spontaneous myopia group, ChT and ChBP were reduced by 25.2% and 31.9%, respectively. In FDM eyes, mean ± SD ChT and ChBP decreased significantly compared with the untreated fellow eyes (ChT fellow: 76.13 ± 9.34 μm versus 64.76 ± 11.15 μm for FDM; ChBP fellow: 37.87 ± 6.37 × 103 versus 30.27 ± 6.06 × 103 for FDM) and increased after 4 days of recovery (ChT: 77.94 ± 12.57 μm; ChBP: 37.41 ± 6.11 × 103). Effects of LIM were similar to those of FDM. Interocular differences in ChT and ChBP were significantly correlated in each group (FDM: R = 0.71, P < 0.001; LIM: R = 0.53, P < 0.001).

Conclusions

ChT and ChBP were significantly decreased in all three models of guinea pig myopia, and they both increased during recovery. Changes in ChT were positively correlated with changes in ChBP. Therefore, it is possible that the changes of ChT are responsible for the changes of ChBP or vice versa.

Choroidal changes in human myopia: insights from optical coherence tomography imaging

The choroid is a vascular tissue which plays a range of critical roles in the normal physiology of the eye, such as supplying the outer retina with oxygen and nutrients and the regulation of intraocular pressure. There is also substantial evidence, particularly from animal studies, that the choroid plays an important role in the regulation of eye growth and the development of common refractive errors like myopia. In recent years, advances in optical coherence tomography technology have improved our ability to image and measure the choroid in the human eye. Research using this technology over the past decade has dramatically improved our knowledge of the normal choroid, and its potential role in the regulation of eye growth and refractive error development. This review aims to provide an overview of recent work examining the normal human choroid, its changes with myopia and the possible role of the choroid in the mechanism regulating eye growth. Studies have demonstrated that choroidal thinning accompanies the development and progression of myopia, and have established a close link between eye growth and choroidal thickness changes. Dramatic thinning of the choroid is seen with high myopia, and associations are also observed between choroidal thinning and reduced vision, and the development of retinal pathology associated with high myopia. In the short-term, environmental factors known to be associated with myopia development and more rapid eye growth typically lead to a thinning of the choroid, whereas factors linked to a slowing of eye growth are typically associated with short-term choroidal thickening. Collectively, these findings suggest that the choroid is an important biomarker of eye growth in the human eye, and additional research to better understand the human choroid is likely to further our knowledge of the signals and pathways regulating eye growth, myopia development and progression.