About Refractive Errors

What are Refractive Errors?

Refractive error is a phenomenon that occurs when the eye is unable to focus light from an object onto the plane of the retina, resulting in blurred images. Refractive errors affect the lives of people, both children and adults, leading to difficulty performing daily tasks, vision loss, and eventually blindness. Both genetic and environmental factors have been implicated in their development. Myopia (near-sightedness), hyperopia (long-sightedness), and astigmatism (the eye does not have a single focus) are three types of refractive defects. The World Health Organization (WHO) estimates that 285 million people worldwide are visually impaired, of which 246 million have low vision and 39 million are blind. Among them, the global myopia rate is rising sharply.

What is Myopia?

Myopia is the most common eye disorder worldwide, yet it is often mistaken for simply a refractive error that can be corrected simply with glasses, contact lenses, or refractive surgery. In fact, high myopia is often associated with an increased risk of a range of serious eye complications, which can lead to irreversible vision loss. The World Health Organization (WHO) defines "high myopia" as -5 diopters (D) or more, which is associated with an increased risk of blindness. Highly myopic eyes with degenerative changes in the macula, optic nerve, and peripheral retina are considered pathologically myopic and are at high risk of potentially blinding complications such as retinal detachment, myopic choroidal neovascularization (CNV), and myopic macular degeneration.

Treatment of Myopia

Several anti-myopia drugs are well known and have been studied extensively in animal models, but human trials remain unclear due to their potential side effects and adverse events in dosage, frequency, and duration of studies. The US FDA only allows three anti-myopia drugs, atropine, pirenzepine, and 7-MX, to conduct clinical trials, but has not yet approved prescriptions. Off-label use of topical atropine is the only treatment currently used to slow myopia progression. Higher concentrations of atropine (eg, 1% or 0.5%) have been shown to be very effective in slowing myopia progression, but with a high incidence of photophobic side effects (up to 100%). In addition, there are concerns about potential long-term systemic or ocular side effects and rebound effects after drug discontinuation.

Although upregulation and downregulation of retinal and scleral muscarinic receptors have been postulated to have an effect on the scleral stroma, the exact mechanism of topical atropine remains unclear. In addition, atropine inhibits myopia induction in mammalian and avian eyes. Unlike the eyes of mammals, the eyes of birds contain striated ciliary muscles innervated by nicotinic rather than muscarinic receptors. Therefore, atropine may act at relatively low doses through the M1/M4 receptors in the retina rather than through the regulatory system. On the other hand, the nonmuscarinic and direct effects of atropine on scleral fibroblasts may also contribute to this effect.

Overall, despite extensive research on myopia control worldwide, the exact etiology and mechanisms of myopia progression have not been fully identified and understood. Questions about how the drug delays myopia progression, its pharmacodynamics, and pharmacokinetics remain unanswered. Currently, although dozens of myopia control trials are underway, no treatment is considered 100% effective. As myopia control has become mainstream clinical practice, the global research goal is not limited to developing mitigation measures but trying to find an anti-myopia drug with minimal or no side effects but maximum efficacy or therapy to prevent the development of myopia.

One-Stop Preclinical Retinal Detachment Studies Solutions

As an industry-leading comprehensive contract research organization (CRO), Ace Therapeutics focuses on the health of ocular diseases and improves ocular diseases by helping customers provide drug discovery and preclinical research solutions. Our support staff averages decades of experience in preclinical ophthalmology research for pharmaceutical companies, biotech companies, and large CROs, who help customers around the world deal with each stage of preclinical drug development. Our one-stop solutions cover the development of ocular disease models, in vivo ocular pharmacodynamic studies, ocular tolerance and safety studies, early pilot studies, and proof-of-concept and bioanalytical levels. All of our projects are customizable and flexible, which allows us to fully understand our clients' needs and how to meet them.

At Ace Therapeutics, our team of experts is dedicated to supporting your preclinical retinal detachment research. We provide a rodent model of sodium hyaluronate-induced retinal detachment to help global customers test the effect of therapeutic drugs in promoting retinal reattachment and/or reducing detachment. Additionally, we offer minipig models of PVR to help our clients explore the molecular mechanisms of PVR pathophysiology and evaluate potential therapeutic agents or long-term interventions. Our service scope covers the whole process from the discovery of lead compounds to the implementation of preclinical GLP projects. We promise to support you in the development and mechanism exploration of upcoming ophthalmic therapies with the highest quality service.

References

1. Yam JC, Zhang XJ, Zhang Y, et al. Effect of Low-Concentration Atropine Eyedrops vs Placebo on Myopia Incidence in Children: The LAMP2 Randomized Clinical Trial. JAMA. 2023, 329(6):472–481.
2. Wu PC, Chuang MN, Choi J, et al. Update in myopia and treatment strategy of atropine use in myopia control. Eye (Lond). 2019, 33(1):3-13.

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