About Vision
The eye is an ultra-specialised organ, capable to assure an astonishing level of vision to a healthy young person. Not only it provides the sharp vision of medium and far range targets with good lighting conditions, but is able to adapt and maintain a good level of vision when drastic changes in the environment occur e.g.: too much or too little illumination (called fotokinetic adaptation), or too close a distance (called accommodation). There are a number of abnormal conditions of the eye which can alter the capacities enumerated above, called refractive conditions.
Frequent Eye conditions
Refractive Conditions
Normal vision is the result of a complex set of adjustments within the eye, having as a result the focusing of the light originated in any point in space we look at, on the retina.
Refractive conditions: Myopia, Hyperopia, Astigmatism, Presbyopia
Myopia occurs when the eye is too long or when the cornea is too steep to focus the light precisely onto the retina. Instead, the light is focused on a point in front of the retina, resulting in poor distance vision. This is also known as short-sightedness or near-sightedness.
Myopia can be treated or corrected with one or a combination of the following techniques:
- Glasses/Spectacles
- Contact lenses
- LASIK (Laser in situ keratomileusis)
- PRK (Photo refractive keratectomy)
- ICL (Intra ocular contact lens implants)
- Phakic IOL implants
- CLE (Clear Lens Extraction: extraction of the natural crystalline lens of the eye) and IOL (artificial Intra Ocular Lens) implantation
Hyperopia occurs when the eye is too short or the cornea too flat to focus the light precisely on the retina. Instead, the light is focused on a point behind the retina which results in poor distance and even poorer near-vision eg. poor reading. This is also known as long-sightedness or far-sightedness.
There are various means to correct hyperopia:
- Glasses/Spectacles
- Contact lenses
- LASIK (Laser in situ keratomileusis)
- PRK (Photo refractive keratectomy)
- ICL (Intra ocular contact lens implants)
- CLE (Clear Lens Extraction) and IOL (intra ocular lens) implants
- Phakic IOL implants
Astigmatism is caused by either an irregularly shaped cornea or at times, by an irregularly shaped lens.
In a normal eye, the cornea is shaped much like a round dome, and when light enters the eye, passes through the cornea and the lens, it is focused onto one precise spot on the retina.
In an astigmatic eye, the cornea is shaped more like an oval dome or half a rugby ball.
This shape causes the light to be focused on 2 or more spots in front of and behind the retina instead of just the one, resulting in fuzzy vision.
Astigmatism can be corrected or treated with the aid of:
- Glasses/Spectacles
- Contact lenses
- LASIK (Laser in situ keratomileusis)
- PRK (Photo refractive keratectomy)
- Toric IOL (intra ocular lens) implants
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