Mechanisms Behind Common Eye Disorders
1.Anatomy of the eye
The eye primarily consists of: the pupil, lens, vitreous body, and retina. The lens is a transparent, colorless structure located behind the pupil, which is convex on both the front and back surfaces, functioning like a magnifying glass with significant refractive power. Due to its inherent elasticity and ability to change shape, the lens can alter its thickness with the help of surrounding muscles and ligaments, allowing for adjustments in its refractive power, a feature known as accommodation. When we look at distant objects, accommodation relaxes (the lens flattens, reducing refractive power); when we look at near objects, accommodation is strengthened (the lens thickens, increasing refractive power). By adjusting the thickness of the lens, images can be focused on the retina, allowing us to see clearly.
2.Common eye disorders
Common eye disorders can generally be categorized into three types: myopia (nearsightedness), hyperopia (farsightedness), and presbyopia (age-related farsightedness).
- Myopia occurs when parallel light entering the eye focuses before reaching the retina, resulting in unclear images of distant objects while near objects remain clear to the patient.
- Hyperopia refers to a refractive condition in which parallel light rays focus behind the retina without using the accommodation function after being refracted through the eye’s optical system. Consequently, to see distant objects clearly, individuals with hyperopia must use their accommodation to increase their refractive power, and even more accommodation is needed to see near objects clearly. The main symptoms include blurred vision at a distance and even more blurred vision up close, along with visual fatigue. Hyperopia often develops in childhood.
- Throughout a person's life, the lens gradually enlarges and hardens, which affects its ability to accommodate. By around the age of 40, this reduction in accommodation becomes significant, leading to a decline in near vision. As a result, individuals may need to move objects farther away to see them more clearly, which is known as presbyopia.
3.Corrective Glasses
Many adolescents experience declining vision due to intense study, excessive digital device viewing, or playing video games. In such cases, the condition may be pseudomyopia (false myopia) or true myopia. If it is pseudomyopia, there is no need for glasses; resting the eyes for a period can alleviate symptoms. However, once someone with pseudomyopia starts wearing glasses, it can develop into true myopia, making recovery difficult. To avoid misdiagnosis, it's best to consult a doctor for an examination after dilating the pupils to determine the need for glasses. For children diagnosed with amblyopia or strabismus, proper treatment should be followed, and one should not blindly wear or avoid glasses.
Whether it’s myopia, hyperopia, or astigmatism, if vision is significantly impaired, affecting learning, work, and daily life, or leading to noticeable symptoms like eye fatigue, dizziness, or headaches, an eye exam and glasses fitting is necessary. Children under six are often hyperopic, while young people mostly suffer from myopia, and older adults commonly experience presbyopia or a mix of myopia, hyperopia, or astigmatism.
Corrective glasses come in three types: myopia glasses, hyperopia glasses, and presbyopia glasses, while protective glasses include sunglasses and Plano glasses.
Myopia glasses
These are concave lenses that help myopic patients see distant objects clearly. Some individuals fear that wearing glasses for long periods will worsen their myopia, leading them to avoid necessary eyewear, which ultimately increases the strain on their eyes, forcing them to squint to see their surroundings. This can increase intraocular pressure and exacerbate myopia.
Hyperopia glasses
These are convex lenses, and not all hyperopes need to wear glasses. The decision should be based on factors such as age, degree of hyperopia, vision quality, eye fatigue, and eye alignment. Mild hyperopia in young children is often physiological, so glasses may not be needed. However, if hyperopia leads to reduced vision, eye fatigue, or esotropia, an eye exam and glasses fitting should be done as soon as possible.
Presbyopia glasses
The prescription for presbyopia varies with age, so one should undergo a proper eye exam and glasses fitting rather than purchasing a cheap pair of reading glasses from a stall.
Sunglasses
Wearing high-quality sunglasses outdoors not only blocks certain light from entering the eyes, reducing fatigue, but also effectively minimizes harmful light (primarily UV rays) that can damage the eyes.
In terms of lenses material, it can be categorized into glass resin , and PC
(polycarbonate) lenses. Glass lenses have stable refractive indices, are highly scratch-resistant, and offer consistent optical performance but are relatively heavy and prone to breaking. Resin lenses are lightweight, safe, have high light transmission, and are less likely to shatter, although they are more susceptible to surface scratches. PC lenses, also known as space lenses, have high refractive indices and excellent durability, but they might also scratch easily. Additionally, various coatings can be applied to lenses, such as anti-reflective coatings, anti-radiation coatings, and waterproof coatings, each serving different functions. For instance, anti-reflective coatings improve light transmission through the lens, making objects appear clearer, while anti-radiation coatings filter out harmful radiation (primarily UV rays) to protect the eyes.
Plano glasses
These are glasses without any refractive power, meaning they do not correct for myopia or hyperopia. When not myopic, wearing plano glasses outdoors can help protect the eyes from wind and dust, preventing bacteria in fine dust from infecting the eyes. Additionally, wearing plano glasses with anti-radiation or anti-blue features while looking at a computer screen can reduce exposure to computer radiation.
