Keratophakia is a type of refractive keratoplasty where a patient receives donor corneal tissue that has been frozen and shaped to the desired curvature. The donor tissue is inserted between the layers of the recipient’s cornea. If it is inserted over the cornea, it is known as keratomileusis.
The goal of keratophakia is to alter the cornea’s curvature and correct optical errors like ametropia, myopia, and aphakic hyperopia. Aphakia refers to the absence of the lens of the eye. Patients with various forms of aphakia (for example, phakic eyes with higher degrees of myopia or hyperopia) and very high hypermetropia may also consider the procedure. However, it is not recommended in patients with corneal diseases, very thin corneas (keratoconus), irregularly thick corneas, steep corneas with hypermetropia, and flat corneas with myopia.
Research indicates that keratophakia presents a physiologically superior alternative to the usual alloplastic lens substitute, to correct aphakia. The procedure is mostly performed in young patients who cannot tolerate contact lenses and in older patients with aphakia as well as endothelial damage and who cannot be treated with intraocular lens insertion.
Before the Procedure
The patient will discuss the procedure with the ophthalmologist. The benefits and risks of the procedure are explained. The patient's medical and ocular history is also taken.
Specific measurements conducted via an ultrasonic device will be taken and include:
- Corneal thickness
- The anterior chamber’s depth
- The crystalline lens’ thickness when it is at rest
- The distance between the retina and the lens' posterior surface
The ophthalmologist also makes optical calculations to establish the refractive index's mean value for every eye component. All these measurements are then programmed into a computer.
The patient is put under anesthesia and then the surgeon:
- Removes the patient’s corneal epithelium.
- Uses a microkeratome to remove a lamella disc from the donor cornea, measuring 0.4 to 0.5 mm thick and with an 8mm diameter.
- Feeds the computer with the average keratometer’s readings and refractive error readings. S/he also inputs measurements concerning the thickness of the donor disc and the remains of the corneal bed, into the computer.
- Freezes and lathes the homograft disc into a lenticle as guided by the computerized specifications. The disc is ground while in its frozen state to a power calculated to correct the targeted refractive error.
- Uses a microkeratome to remove a lamellar cap (measuring about 0.3mm in thickness). S/he restructures the cap to its exact position using sutures.
- Places the lenticle under the recipient cap and sutures it to Bowman’s membrane after a new anterior curvature has been created.
Risks & Complications
The eye doctor removes the suture in six to eight weeks following the surgical procedure. The suture should not be removed too early because it can lead to complications associated with the epithelium.
Visual acuity return is usually prolonged and can vary among individuals.
Risks and complications both during the procedure and postoperatively may include:
- Corneal scarring
- Loss of the lenticle
- Infection of the wound
- Corneal opacity or clouding
- Displacement of the lenticle
- Inadequate lenticle preparation
- Dry eye or corneal surface drying
- Perforation of the recipient cornea
- Foreign bodies in the eye even during surgery
- Arterial occlusion (blood flow to the artery is cut short)
- Wound dehiscence if the sutures are removed too early
- Stromal edema which can be controlled with hypertonic tears
- Epithelial ingrowth if resuturing is delayed, necessitating a repeat keratophakia
- Technical complications involving the lenticle during the grinding and insertion process
- Monocular diplopia which can develop as a result of irregular resection with the microkeratome
Aftercare & Recovery
The eye will be patched for 48 hours. Certain medications are prescribed to assist with faster healing. They include homatropine 5%, which is instilled two times a day for a week. In the first week, the patient uses a combination of antibiotics, and steroid drops four times a day and then twice daily for the next four weeks. The patient will also use hypertonic saline several times a day to help with stromal edema. In the case of corneal drying, s/he also uses artificial tears.
Sutures are removed between three to five weeks, and the patient undergoes postoperative evaluation that consists of slit-lamp microscopy, tonometry, keratometry, specular microscopy, pachymetry, and taking of corneascope photos.
Visual outcomes are usually good for most patients despite the slow speed of visual recovery. This slow speed is often apparent to patients who have an intraocular lens in the other eye.