Cornea

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What is the Cornea

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The cornea is a very clear transparent window of the front of the eye.

It is approximately half a millimetre thick. It is clear the does not normally contain any blood vessels and is made up primarily of a protein called collagen.

There are five main layers of the cornea. The innermost layer, the endothelium, is a singer single layer of cells and its primary function is to keep is to prevent the rest of the cornea from becoming waterlogged and to provided with nutrients.

The endothelium rests on a then the membrane called Descemet’s membrane. The main part of the cornea is the corneal stroma which gives the cornea its rigidity.

The Bowman layer is the outermost part of the corneal stroma and is more tightly packed with collagen. Outermost layer of the cornea, the epithelium, has layers of cells that helps smooth front surface of the cornea.

What does the Cornea do?

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One of the cornea’s main role is to transmit and focus light as it enters the eye. The cornea is the main focusing lens of the iron contributes to 2/3rds of the total focusing power of the eye.

It also helps to shield the rest of the eye from germs, dust, and other harmful matter. The cornea shares this protective task with the eyelids, the tear film, and the white part of the eye (sclera).

Fuchs Dystrophy and DMEK

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Fuchs dystrophy is a condition of the corneal endothelia. It is an inherited condition that becomes apparent between the ages of 40 and 60. Symptoms commonly experienced are blurring of vision and halos around lights particularly after waking from sleep. This is caused by waterlogging of the cornea as the endothelial cells function reduces.

Currently, the best treatment for symptomatic Fuchs corneal endothelial dystrophy is a single cell layer corneal transplant called DMEK (Descemets membrane endothelial keratoplasty). This provides a like-for-like replacement of the damage cells and has a number of advantages over older techniques including faster and more complete visual recovery lee, lower risk of rejection and a reduction in and potency and frequency of steroid medication.

When performing lens replacement or cataract surgery, an intraocular lens, that is a lens placed inside the eye, can be selected that corrects the eyes natural defocus error. Lenses can be made to cover a very large range of far-sightedness from as low as +0.5 all the way up to +30 and beyond! This could enable you to enjoy good vision with minimal dependence on glasses.

After returning from my fellowship training in Rotterdam with the originator of the technique, Dr Melles, I have pioneered this technique and was the first person to carry out this procedure in the North of England in 2013. Since then, I have lead the way in using this technique for more challenging cases and have been invited to speak about it at professional meetings. For further information on the advantages of this technique


Keratoconus: Crosslinking and Kerarings

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Keratoconus is a condition which causes the cornea to become then and irregular in shape. Symptoms include blurred vision which is worseat night and distortion of imagesnthat is not fully corrected by glasses. Good vision can normally be restored by contact lenses. In younger patients keratoconus is often a progressive disease.

Cross-linking is an excellent option in patients where the cornea is becoming more out of shape. It is a relatively simple and effective treatment at halting the progression of keratoconus and there is some evidence to show that in the long-term, particularly in younger patients, there is a degree of normalisation of the corneal shape. It is a relatively simple day case procedure.

The epithelium of the cornea is removed, a B vitamin (riboflavin) is applied to the cornea for approximately 30 minutes and thereafter an ultraviolet light is applied to the cornea for approximately 10 minutes. Cross-linking is thought to strengthen the cornea by increasing the number of molecular bridges between the collagen fibres that make up the corneal stroma.

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Kerarings are a type of ICRS (intra-corneal ring segment). Their purpose is to reshape or regularise the shape of the cornea to help improve vision. They are particularly useful for patients who find contact lenses uncomfortable. A highly precise femtosecond laser is used to make a tunnel within the cornea, the segments are then placed into these tunnels. The size shape and position of the rings are specifically calculate it for each individual cornea to help optimise results.

For some patients implantable column lenses can be used to correct vision.

In cases of advanced keratoconus or where there is corneal scarring, a corneal transplant may be the best option.

Corneal Transplants

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When the cornea becomes cloudy due to scarring and insufficient light is transmitted into the eye a transplant involving the stroma may become necessary. This may be due to corneal infections traumatic damage to the cornea or advanced forms of keratoconus.

There are two main forms of transplantation that involve replacing the corneal stroma. A full thickness or penetrating keratoplasty involves transplantations of all the layers of the cornea. A DALK (deep anterior lamellar keratoplasty) involves transplantation of all the parts of the cornea apart from Descemets membrane and the endothelium.

Both these forms of transplantation require stitches or sutures to the cornea and the recovery period takes between six and 18 months.

Although not possible for all cases a DALK keeps the eyes structurally more intact and negates the risk of rejection of the fact that regression involving the endothelium.

Pterygium

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A pterygium is abnormal growth of conjunctiva across cornea.

The exact causes of this abnormal growth are not fully understood. People exposed to high levels of ultraviolet light and those that work in dry dusty environments are more prone to develop pterygia. It is not a cancerous growth and therefore small teacher do not need to be removed. A pterygium can affect vision by growing across the front of the eye or inducing astigmatism. When a pterygium is affecting vision or causing discomfort it can be removed surgically.

A very thin layer of conjunctiva is used to cover the area and is glued into position, therefore no stitches are required and healing is improved.

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Spire Elland Hospital
Elland Ln, Elland, West Yorkshire
HX5 9EB

01422 324069

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01422 324 069

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