The eye is an essential organ of the visual system. It is made up of 2 parts: the eyeball and the optic nerve which transmits visual information to the brain. To create an image, light rays cross the transparent membrane which is the cornea, then the lens which helps us move from near sight to far sight. Lastly, the image is formed on the retina, the highly vascularized nervous tissue which transmits the image to the brain via the optic nerve.
The various refractive disorders or ametropia
Refractive disorders are the most common and best-known (myopia, astigmatism, hypermetropia). They result from an anomaly in the optical system: eyes which are too long or short, misshapen corneas such as a cone shape, etc.
Myopia is a condition caused by an excessive distance between the cornea and the retina. The perceived image is therefore formed in front of the retina. Vision is perfect close-up but distant abjects appear blurry. It is corrected by wearing glasses or contact lenses with concave lenses. With these devices, the image is pushed back to the back of the retina, thus achieving clear vision.
Conversely, hypermetropia is a condition caused by an eye which is too short, resulting in blurred vision close-up and generally correct vision in the distance. Unlike myopia, this condition can be corrected and compensated by the eye. This effort does, however, lead to fatigue and headaches, in particular at the end of the day. Contrary to myopia, hypermetropia is corrected by convex lenses.
Presbyopia is a condition caused by the natural aging of the eye. Over the years, the lens loses its elasticity and the eye then struggles to form a clear image depending on the distance. Correction involves wearing multifocal lenses known as progressive lenses to create clear vision regardless of the distance. Presbyopia is common in people aged over 45.
Astigmatism creates blurred vision at all distances because the contrasts between horizontal, vertical and oblique lines are not well perceived. Astigmatism may be associated with other visual impairments such as myopia, hypermetropia or presbyopia. It may be corrected by wearing corrective tarie lenses in glasses or contact lenses. In all these cases, depending on the degree of visual impairment and discomfort, refractive laser eye surgery may be suggested should the ophthalmologist deem it necessary.
The main eye conditions
AMD or age-related macular degeneration is a chronic and progressive disease of the central retina. It leads to a gradual decline in vision in the center of the visual field which hinders reading, facial recognition, driving, etc. When diagnosed early, its progression may be slowed in patients with the so-called "wet" form of the condition with appropriate treatment. To date, there is no known treatment for "dry" AMD. The onset of the condition generally occurs after the age of 50.
A cataract is a partial or total clou ding of the lens which results in a graduai decline in vision (blurred or hazy vision). It is the leading cause of blindness worldwide. Depending on the progression of the cataract, surgical treatment may be proposed. This involves extracting the lens and replacing it with an artificial lens known as an intraocular lens implant. Cataracts are most often related to aging but unprotected eye exposure to the sun is an aggravating factor.
Glaucoma is a chronic eye disease, due to lesions on the optic nerve caused by increased pressure in the eye. The visual field is as a result gradually reduced. Treatment aims to decrease eye pressure by administering drops daily. Such treatment must be administered for lite, failing which glaucoma results in blindness. Depending on the case, surgical treatment, possibly by laser, may be necessary.
Diabetic retinopathy is a frequent, often insidious, complication of diabetes. It is a condition which affects the vascularization of the retina. Uncontrolled diabetes seriously alters the nerves and blood vessels which may result in retinal detachment. Macular edema, which may cause a significant and partly irreversible drop in visual acuity, and a hemorrhage in the eye, which may bring about a sudden loss of vision, are the main symptoms of diabetic retinopathy.
How can visual disorders and eye conditions be prevented?
Preventing eye disorders and conditions involves simple principles that should be applied from a very early age in order to avoid or slow certain processes which may prove to be dangerous over the long term.
1 - Protect your eyes from the sun
Exposure to sunlight may damage the cornea, the lens and the retina temporarily though this damage is sometimes permanent. It is therefore advisable to wear anti-UV and anti-infrared sunglasses and a sunhat or cap.
2 - Adopt a healthy and balanced lifestyle
Avoid alcohol and tobacco, risk factors which irritate the eyes. Consumption of high levels of alcohol not only affects vision in the short term, but also in the long term due to its drying effect. It favors the development of cataracts and age-related macular degeneration (AMD).
3 - Avoid prolonged exposure to screens (computers and tablets)
and in particular to blue light. Continued viewing of screens dries the eyes and causes muscular fatigue in the eye. One rule is to look at a screen for no longer than 20 minutes. Take regular breaks by looking away and blinking. You can also change the height of your computer screen so that your eyes are in line with the top of the screen when you look ahead. Less eye fatigue is caused by looking down than by looking up.
4 - Go for regular check-ups with an ophtalmologist
particularly if you are aware of any family history of eye conditions. Consider ta king children for a preventive check-up a round the age of two or three. For adults, a check-up is necessary every three years, and every year from the age of 45.
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