Keratophakia is an operation in which a lens shaped implant is placed into the cornea. The implant may be made from synthetic material e.g. hydrogel, similar to that used in soft contact lens manufacture, or alternatively it may be made from donated human corneal tissue. The implant or lenticule causes a change in the corneal surface profile, which alters the cornea's refractive power.

Indications

Keratophakia was originally conceived over fifty years ago by Dr José Barraquer as a treatment for the correction of hypermetropia (long-sightedness). It has also been used as a treatment for myopia, and more recently for the management of keratoconus and corneal ectasia. In these latter conditions, the lenticule may be designed primarily to restore the corneal thickness to normal, rather than to change the corneal surface profile.

Anaesthesia

Because the surgery is entirely within the cornea, the operation can be carried out with topical anaesthesia (eye drops) alone. However, if the patient wishes, it can be carried out with a regional anaesthetic injection, or alternatively under general anaesthesia.

Surgery

A microkeratome similar to that used for LASIK surgery is used to cut a thin flap across the surface of the cornea. The flap is lifted up and the lenticule is placed in the centre of the cornea. The flap is then laid down on top of the lenticule, and sutured in place.

In the treatment of keratoconus or corneal ectasia, the keratophakia procedure may be combined with insertion of Intacs intra-corneal implants.

Corneal tissue lenticules

When the keratophakia implant is made from donated human corneal tissue, the surgery is a type of corneal transplant operation. All donors of corneal grafts are screened to exclude transmissible diseases such as hepatitis, syphilis, and HIV. However because of the very small risk of onward disease transmission, any patient who has had a corneal graft is no longer acceptable as a blood or tissue donor themselves.

When the donor corneal tissue is processed into a lenticule for keratophakia, it may be cryo-lathed or freeze-dried. Both of these processes kill the cells in the tissue, which means that there is no longer any risk that the tissue can be rejected. When the tissue is implanted in the patient's cornea, it becomes repopulated by the patient's own cells, and thus becomes unrecognisable from their own tissue.

Complications

The long-term bio-stability of synthetic keratophakia lenticules is unknown, and there may be tissue reaction and stromal opacification around the lenticule. Interface debris may cause corneal inflammation, and epithelial cells trapped at the interface may require surgical removal if persistent. Keratophakia surgery is however potentially reversible and the lenticule may be simply removed if necessary.

Post-operative

The operation is generally carried out as a day-case, and does not require overnight stay in hospital. Antibiotic and anti-inflammatory eye drops are used for a month or two to settle the eye down. There is generally little pain or restriction of activity as a result of the surgery, but it is important not to rub the eye, and a protective shield should be worn at night for a few weeks. The corneal sutures are removed under topical anaesthetic during a routine follow-up visit a few weeks after the surgery.

Visual recovery

The speed of visual recovery will vary depending on the type of keratophakia being performed. The refraction of the eye may take some months to stabilise. If there is irregularity in the corneal shape, or significant residual optical defect, further surgery such as LASIK may be required to fine-tune the outcome.

Although keratophakia has been performed for many years, current techniques and implantational devices are still in a state of experimental evolution.