Laser thermal keratoplasty (LTK) is a surgical technique that treats farsightedness by reshaping the cornea using a holmium-YAG laser. The goal is to reduce the need for corrective lenses, glasses, or reading glasses. It is a non-invasive procedure that doesn’t involve any cutting or tissue removal. Instead, the surgeon shrinks the collagen fibers (on the outer part of the cornea) to steepen the cornea using the laser beam in a predetermined manner. This action alters the focal point of the eye. Because it's a 'no-touch' procedure, it has little chance of resulting in complications like infection or vision loss.
LTK is not suitable for individuals who have refractive instability. Such individuals include the diabetics, pregnant women, lactating mothers, those under age 18, and those on medications such as steroids. Some diseases such as rheumatoid arthritis, diabetes, and HIV may interfere with wound healing; therefore, individuals affected by such should not undergo LTK. Certain eye diseases such as keratoconus and other diseases like herpes simplex and glaucoma may affect the outcome of LTK. These conditions should be corrected first, if possible, before LTK can be performed.
Sportspeople who participate in sports like martial arts, wrestling, and boxing may not be good candidates for LTK due to the possibility of blows to the eyes and face. Those already with eye injuries should also avoid LTK until they are healed.
Before the Procedure
The procedure will be performed in an ordinary exam room. The entire process should take approximately 30 minutes.
A full preoperative evaluation is necessary to consider the suitability of the procedure for the patient. The potential risks and benefits are explained so that the patient can provide informed consent. A full medical and ophthalmic history of the patient is taken. For instance, it's essential to disclose whether previous refractive surgery was performed on the patient. In this case, the surgeon may see no need for additional surgical intervention.
The patient also undergoes a complete eye examination. Ocular measurements include:
- Corneal thickness to detect keratoconus
- Eye movements, assessment of the tear film, and measuring the pupils' size
- Corneal topography to measure the curvature of the front eye surface to detect keratoconus
Patients who wear rigid gas permeable contact lenses should stop putting them on for several weeks before the eye examination. The patient is advised not to wear soft contact lenses for some days or weeks before surgery.
In the procedure:
- The patient’s eye will be numbed with anesthetic drops at least 10 minutes before treatment
- To prevent blinking, the eye is kept open by use of an eyelid holder
- The surgeon allows the tear film to dry for three minutes
- S/he will apply the laser beam for less than three seconds per eye. The number of laser pulses administered will depend on the condition being treated. The surgeon uses two rings of eight spots around the eye's optical zone, thus shrinking the corneal collagen.
- Places a bandage contact lens on the eye
Risks & Complications
LTK presents with rare severe complications. However, there are a few sight-threatening complications that may arise, including irregular astigmatism and visual aberrations like loss of contrast sensitivity, glare, halos, and decreased night vision. Others are epithelial cell loss and significant corneal scarring. A severe risk may arise if refractive surgery is performed on a very thin cornea because it may lead to blindness.
Most of the complications are usually mild and will eventually resolve on their own or be treated. However, some like photophobia (sensitivity to light), halos, and glare may be permanent.
Side effects and complications may also include:
- Double vision
- Visual acuity loss
- Corneal infiltration
- Irregular astigmatism
- A worsened dry eye condition
- Regression of correction requiring re-treatment
- Under or over-correction depending on how much tissue was shrunk
- Problems with fitting contact lenses should additional correction be required
Aftercare & Recovery
A protective shield is placed over the eye. The bandage soft contact lens placed soon after the laser application is removed after 24 hours. The patient may experience irritation in the first few days following the procedure. The specialist will prescribe antibiotics, and nonsteroidal anti-inflammatory eye drops to be taken four times daily until healing of the epithelium has taken place. The expected recovery time for a patient is 24 to 72 hours.
LTK is usually successful in steepening the cornea, correcting refractive error, and reducing the need for contact lenses or eyeglasses. Most patients will attain 20/40 vision or more. A lower percentage of LTK patients will need an additional procedure. Some will still require eyeglasses or contact lenses to make up for under correction or overcorrection.