Cornea

The cornea is the transparent tissue that covers the front of your eye. It lies in front of the iris and the pupil and is dome-shaped. Because the cornea is clear, light can pass through it into the eye; because it has a curved surface, it refracts the light and helps to focus what you see.

The cornea consists of five layers of tissue and contains no blood vessels. The cornea receives oxygen and nutrients via the tear film on the outside and the aqueous humour on the inside. The outermost layer, the epithelium, is constantly renewing itself and repairs minor damage quickly. The middle layer, the stroma, makes up the bulk of the cornea’s thickness and provides structural strength. The innermost layer, the endothelium, pumps fluid out of the cornea to keep it clear and transparent.

The cornea is sensitive: it contains many nerve endings, which means you quickly notice if something gets into your eye. This is a protective mechanism. Due to its curved shape and refractive power, the cornea accounts for the majority of your eye’s total refractive power, even more so than the lens behind it.

Contact lenses and the cornea

Contact lenses rest directly on the tear film covering the cornea, or, in the case of hard lenses, float just above it. As the cornea needs oxygen to stay healthy, modern contact lenses are made from materials that allow oxygen to pass through. Soft lenses contain water and allow oxygen to pass through that water; hard, rigid lenses are thinner and allow oxygen to pass through the material itself.

When wearing contact lenses, it is important that the cornea receives sufficient oxygen and that tears continue to circulate properly. You should therefore wear your lenses in accordance with the instructions for use and replace them on time. At SMEYEL , you’ll find contact lenses and lens solution designed to keep your lenses clean and comfortable.

Abnormalities and shape

The shape of the cornea helps determine how well you see. If the cornea is regularly curved, light is refracted evenly. If the cornea is too steep or too flat, this can cause short-sightedness or long-sightedness. If the cornea is not round but oval or irregular in shape, this is known as astigmatism or a cylindrical aberration; light is then refracted differently in different directions.

Some conditions, such as keratoconus, alter the shape of the cornea. In keratoconus, the cornea becomes thinner and bulges outwards. This requires special contact lenses or, in some cases, medical intervention. If you have any concerns about your vision or suspect an abnormality in your cornea, please have it assessed by your optician, optometrist or ophthalmologist.

Damage and repair

The corneal epithelium heals quickly in the case of minor scratches or superficial damage. Deeper injuries or scarring can affect the clarity and shape of the cornea and impair your vision. Infections, such as those caused by bacteria or fungi, can cause serious damage. You should therefore never wear contact lenses for longer than prescribed and ensure good hygiene when putting them in and taking them out.

If you are unsure or experience persistent symptoms such as pain, redness, sensitivity to light or blurred vision, please contact your optician, optometrist or ophthalmologist.