Scleral Mechanisms Underlying Ocular Growth and Myopia

Metlapally, Ravi; Wildsoet, Christine F.

doi:10.1016/bs.pmbts.2015.05.005

Cited by 75 publications

(48 citation statements)

References 27 publications

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“…27 Finally, a reduction in amount of collagen in the extracellular matrix of the sclera can accelerate axial elongation and promote the progression of myopia. [61][62][63] In summary, we found that the changes in ChT and ChBP in guinea pig models of myopia are similar to those in human myopia. The choroidal circulation is critical for meeting the oxygen demands of the retina and sclera, and decreases in ChBP can lead to a relatively hypoxic environment, which in turn could induce axial elongation and myopia progression.…”

Section: Pathologic Effects Of Decreased Chbp On the Retina And Sclersupporting

confidence: 67%

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

Zhang

Zhou

et al. 2019

Invest. Ophthalmol. Vis. Sci.

150

108

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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 ¼ 7) or temporal ciliary artery transection (n ¼ 6). Changes in refraction, axial length, ChT, and ChBP were measured during spontaneous myopia (n ¼ 9), monocular form-deprivation myopia (FDM, n ¼ 13), or lens-induced myopia (LIM, n ¼ 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 6 SD ChT and ChBP decreased significantly compared with the untreated fellow eyes (ChT fellow: 76.13 6 9.34 lm versus 64.76 6 11.15 lm for FDM; ChBP fellow: 37.87 6 6.37 3 10 3 versus 30.27 6 6.06 3 10 3 for FDM) and increased after 4 days of recovery (ChT: 77.94 6 12.57 lm; ChBP: 37.41 6 6.11 3 10 3). Effects of LIM were similar to those of FDM. Interocular differences in ChT and ChBP were significantly correlated in each group (FDM: R ¼ 0.71, P < 0.001; LIM: R ¼ 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. Keywords: myopia, choroidal thickness, choroidal blood perfusion, guinea pig M yopia is commonly recognized as an ocular disorder that carries significant risks of visually blinding complications. 1,2 In recent decades, the prevalence and severity of myopia have been on the rise, and it is estimated that by 2050 there will be 4.76 billion people with myopia and 0.94 billion with high myopia. 3-6 Meanwhile, the total cost of myopia correction is also increasing, becoming a relatively large economic burden in urbanized countries. 7-9 With the drastic increase in the public health impact, as well as the socioeconomic burden of myopia, many researchers have focused on investigating the mechanisms underlying myopia development. Twenty years ago, in a seminal study, Wallman et al. found that choroidal thickness (ChT) in chicks significantly increased and decreased in response to positive and negative lens-induced defocus, causing hyperopic and myopic refractive shifts, respectively. 10 On removal of the imposed negative lens defocus, the choroid of the now myopic eye thickened, moving the retina forward toward the defocused image plane. Such bidirectional growth regulation has stimulated researchers to study the choroid as a target tissue for myopia control, and ChT has been investigated as a surrogate marker for...

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Section: Pathologic Effects Of Decreased Chbp On the Retina And Sclersupporting

confidence: 67%

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

Zhang

Zhou

et al. 2019

Invest. Ophthalmol. Vis. Sci.

150

108

View full text Add to dashboard Cite

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“…For example, the exact ocular site of action of atropine's inhibitory effect on myopia progression remains unresolved, with the sclera, choroid, and retina among possibilities; underlying cellular and pharmacological mechanisms also remain unresolved. 239,240 Until consensus is reached on the ocular tissue to be targeted, advances in drug delivery cannot been fully exploited to optimize formulations. Additional studies are also needed to establish optimal atropine dosing and treatment regimens, including how long treatment should be continued, when/how it should be stopped, and the possibility of ''prescribing'' short drug holidays to prevent tolerance with higher concentrations.…”

Section: Pharmacological Control Of Myopiamentioning

confidence: 99%

IMI – Interventions for Controlling Myopia Onset and Progression Report

Wildsoet

Chia

Cho

et al. 2019

Invest. Ophthalmol. Vis. Sci.

Self Cite

289

275

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Myopia has been predicted to affect approximately 50% of the world's population based on trending myopia prevalence figures. Critical to minimizing the associated adverse visual consequences of complicating ocular pathologies are interventions to prevent or delay the onset of myopia, slow its progression, and to address the problem of mechanical instability of highly myopic eyes. Although treatment approaches are growing in number, evidence of treatment efficacy is variable. This article reviews research behind such interventions under four categories: optical, pharmacological, environmental (behavioral), and surgical. In summarizing the evidence of efficacy, results from randomized controlled trials have been given most weight, although such data are very limited for some treatments. The overall conclusion of this review is that there are multiple avenues for intervention worthy of exploration in all categories, although in the case of optical, pharmacological, and behavioral interventions for preventing or slowing progression of myopia, treatment efficacy at an individual level appears quite variable, with no one treatment being 100% effective in all patients. Further research is critical to understanding the factors underlying such variability and underlying mechanisms, to guide recommendations for combined treatments. There is also room for research into novel treatment options.

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“…Scleral thinning has been reported in high axial myopia and pathological myopia [21][22][23]. e thickness of the posterior sclera of pathological myopic eyes has been reduced up to 31% compared to the sclera in nonmyopic eyes [24]. During the development of myopia, several structural changes occur such as an increase in collagen degrading enzymes and a reduction of the scleral component of collagen [18,25].…”

Section: Discussionmentioning

confidence: 99%

Comparison of Corneal Biomechanical Properties among Axial Myopic, Nonaxial Myopic, and Nonmyopic Eyes

Tubtimthong

Chansangpetch

Ratprasatporn

et al. 2020

BioMed Research International

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Purpose. To compare corneal deformation characteristics using ultra-high-speed Scheimpflug camera (Corvis ST) in patients with nonmyopic (NM), mild-to-moderate nonaxial myopic (MM), and high axial myopic (HM) eyes. Methods. In this cross-sectional study, normal subjects aged >40 years with no history of ocular laser/surgery were classified according to axial length (AL) and spherical equivalence (SE) into three groups: (1) NM (SE > −0.50 D and AL < 26 mm), (2) MM (SE −6.00 D to −0.50 D and AL < 26 mm), and (3) HM (SE ≤ −6.00 D and AL ≥ 26 mm). Seven parameters including corneal deformation amplitude (CDA), inward/outward corneal applanation length, inward/outward corneal velocity (ICV and OCV), peak distance, and radius were measured. Pearson correlation and linear mixed-effects model were done. Results. A total of 180 eyes were recruited. 98 eyes were NM, 30 eyes were MM, and 52 eyes were HM. There were significant correlations of OCV to the degree of refractive error (r = 0.203, p<0.001) and AL (r = −0.242, p<0.001). After adjusting for age, sex, intraocular pressure, and corneal thickness, there was significantly higher CDA (β = 0.07, p<0.001), faster OCV (β = −0.08, p<0.001), and smaller radius (β = −0.39, p=0.01) in the HM group compared to the NM group. Conclusion. The higher CDA, faster OCV, and smaller radius found in the HM may suggest that these eyes have reduced ocular stiffness and may be less stable and more prone to stress.

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Scleral Mechanisms Underlying Ocular Growth and Myopia

Cited by 75 publications

References 27 publications

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

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

IMI – Interventions for Controlling Myopia Onset and Progression Report

Comparison of Corneal Biomechanical Properties among Axial Myopic, Nonaxial Myopic, and Nonmyopic Eyes

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