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About Your Eyes



Before any eye surgery such as custom LASIK vision correction is considered, basic education about the eye tends to be helpful for our patients. Here is a quick primer on your eyes and how they work.

Custom LASIK Vision Correction Manchester

The Process of Sight

All vision is based on light. In order for you to see correctly, light must pass through various parts of your eye for your brain to interpret what you are seeing and produce an image of the object you are looking at. To see clearly, the cornea (the front of your eye) must be perfectly round. When light passes into the cornea, it passes through the iris, the pupil, and finally, the crystalline lens, located inside of the eye. Depending on the amount of light, the pupil and the iris muscles adjust to allow the proper amount of light in. After passing through the iris and the pupil, the crystalline lens focuses the light onto the retina. The retina senses different types of light and allows the optic nerve to send the information to the brain.


For proper eyesight, the cornea (the clear window in front of the eye) and the lens (behind the pupil) must properly focus or"refract" light onto the retina (at the back of the eye). If the length or shape of the eye is not ideal, the light may get focused too early (in front of the retina) or too late (behind the retina) leaving a blurred image on the eye is a very complex organ that must work precisely in order to produce correct vision. When there are problems with the shape of the cornea, the focusing ability of the crystalline lens, or with the retina, your vision can become jeopardized. Myopia (near-sightedness), hyperopia (far-sightedness), and astigmatism (distorted vision) are what are known as refractive errors. These types of errors can be corrected with corrective lenses such as contact lenses or glasses and can often be permanently corrected with LASIK.


Myopia or nearsightedness, is the ability to clearly see objects up close, but not those at a distance. Myopic patients generally have an eye that is too long, or a cornea that is too steeply curved. This causes light to focus in front of the retina, rather than directly upon it.


Astigmatism is a vision condition that occurs when the cornea (the front of your eye) is slightly irregular in shape. This irregular shape prevents light from focusing properly on the retina, or the back of your eye, and causes multiple points of light. As a result, your vision may be blurred at all distances. People with severe astigmatism will usually have blurred or distorted vision, while those with mild astigmatism may experience headaches, eye strain, fatigue or blurred vision at certain distances. Most people have some degree of astigmatism.


Hyperopia or farsightedness, is the ability to clearly see objects at a distance, but not those up close. This condition occurs when the eye is too short or the cornea is too flat, causing light to focus behind the retina. People with farsightedaness can often see objects that are farther away with much more clarity than objects that are up close.


Presbyopia is the gradual loss of the eye's ability to focus actively on nearby objects. It is a natural part of aging that usually begins to affect people after age 40. For most people, presbyopia becomes apparent when they need to hold print at arm's length in order to read it.


A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. Cataracts are very common in older people. By 75 years old, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes. It cannot spread from one eye to the other. If a cataract develops to the point that it affects your daily activities, an eye surgeon may recommend surgery. During the surgery, the eye's natural lens is removed and usually replaced with an intraocular lens (IOL). There are several types of lenses available, including AcrySof Toric IOL, Crystalens, and ReSTOR.