Keratoconus is a condition that affects the cornea of young adults. The cornea is the front window of the eye which is transparent and focuses light under the centre of the back of the eye to give you clear vision. In Keratoconus there is bulging of the cornea and the shape of the cornea changes from the shape of a football to a rugby ball. This causes distortion of the cornea and thinning of the cornea causing a huge decrease in vision. This condition usually affects both eyes but maybe asymmetric, meaning this affects one eye earlier than the other and most patients have one eye worse than the other.
The cause of this condition is weakness in the layers of the cornea. There are some families where this may be hereditary, but there is no strong direction association. Many patients have atropic conditions as in allergic eye disease such as eczema, asthma and hay-fever. These patients tend to rub their eyes which has a direct link to rapid progression of keratoconus.
The most common treatment for this condition involves wearing glasses when the condition is mild, or use of rigid gas permeable (RGP) contact lenses when symptoms are worse. Only 10% of patients will progress to a level where other things do not work and hence need a corneal transplant. Those patients are intolerant to contact lenses but can be helped by a procedure called Intacs or KeraRings. These are intrastromal corneal ring segments which flatten the curvature of the cornea. This can be combined with other procedures such as corneal collagen cross-linkage.
Within the last decade, there is an option to stop the progression of keratoconus. In the past, treatment was more to improve vision but not to help progression. Corneal collagen cross-linkage is a procedure which stops progression of keratoconus and is effective in 95-98% of patients. The procedure is done under topical anaesthetic where the epithelium, which is the surface layer of the cornea, is removed first. This is then followed by administering riboflavin eyedrops. Once the cornea is soaked in riboflavin, it is exposed to ultraviolet A (UVA) light which increases the validity and strengthens the structure of the cornea. As the cornea becomes stronger, it is more resistant to any forces that would bulge the cornea.
As there is more awareness of keratoconus, more and more patients are being referred by the opticians at a very young age with keratoconus detected. These patients are then put through a procedure called corneal collagen cross-linkage; they avoid any future effects on vision due to progression. The Stoneygate Eye Hospital is a premium eye hospital which offers all varieties of treatment for keratoconus, not only to stop progression but also to remarkably improve vision of patients. Some patients can also benefit from intraocular lenses, which help the astigmatism induced by keratoconus. Astigmatism is distortion of vision due to change in curvature of the cornea. In very few patients where the cornea is very thin and cross-linkage cannot be carried out, these patients can undergo a surgery called intracorneal ring segments. This is carried out under a local anaesthetic and involves plastic ring segments being placed in the body of the cornea to flatten the central curvature and hence improve vision.
As cross-linkage becomes more common, very few patients go on to require a corneal transplant – especially those who have a corneal scar or severe thinning and bulging of the cornea. However, for those still having a corneal transplant, there are two main procedures relating to this condition, one as a full thickness corneal transplant called penetrating keratoplasty, whilst the other is deep anterior lamellar keratoplasty where all the layers of the cornea except the posterior cell layer are replaced. The advantage of both procedures is that there is less risk of rejection and post-operative recovery is faster.
The other procedure available is a topography guided PRK, which is relatively a new procedure and involves use of exothermal laser to mould the shape of the cornea to improve vision. This is undertaken along with cross-linkage, as cross-linkage stops the progression and surface laser improves irregularities of the cornea, improving vision. This procedure is relatively new and is offered by The Stoneygate eye hospital.
To summarise, the main treatment options available for patient suffering from keratoconus:
1) Glasses and RGP contact lenses
2) Intracorneal ring segments
3) Corneal collagen cross-linkage to help progression
4) Corneal transplant
5) Topography guided PRK