Phototherapeutic Keratectomy (PTK) is the surgical treatment of corneal surface diseases or diseases arising from corneal injury. The procedure uses an excimer laser to remove a small outer corneal layer to treat corneal dystrophies like granular dystrophy, recurrent epithelial erosion syndrome, corneal infections, corneal degeneration, and corneal scars. Previously, patients needed a corneal transplantation. PTK is often used for therapeutic reasons when more traditional treatments have failed. It can be used in combination with photorefractive keratectomy (PRK) to address scarring and correct a refractive error.
PTK differs from LASIK in that the latter is a vision correction technique whose goal is to eliminate the patient’s need for contact lenses or glasses.
Preparation & Expectation Before Surgery
Planning for PTK involves proper diagnosis using refractive error amounts, slit lamp examination, and clinical judgment. Preoperatively, the patient will have a complete eye examination with dilation. The doctor measures visual acuity, visual potential, and refraction. S/he also measures corneal sensation, pupil size, and corneal thickness.
Corneal topography is measured because once the patient goes under the laser, it is difficult to assess the cause and nature of the disease accurately. Corneal topography is also essential in following up on the patient after the procedure. It reduces irregular astigmatism and improves visual acuity since it helps to correct refractive error.
Since the success of PTK depends on the proper selection of a case, the doctor must conduct a thorough examination of systemic diseases. These diseases include persistent diabetes and others like rheumatoid arthritis and systemic lupus erythematosus. The problem with these diseases is that they can cause delayed epithelial healing.
Types, Purpose & Procedure
In the procedure:
- The surgeon carefully positions the patient under the laser with the head stabilized and at a proper level. The patient should be comfortable.
- The patient is put under topical anesthesia (Xylocaine or Proparacaine) unless PTK is combined with a procedure requiring local or general anesthesia.
- S/he sterilizes the skin's surface and puts a lid speculum in place, followed by manual debridement (removal of dead or infected tissue) of the epithelium (first corneal layer) using an excimer laser (transepithelial) or a hockey stick knife.
- The surgeon focuses the microscope at high magnification with the patient requested to look at the green fixation light to determine the corneal surface’s plane. The laser can also be centered manually in a peripheral lesion where the surgeon rotates the patient’s head or eye by hand to achieve targeted ablation (destruction of tissue).
- The surgeon removes the epithelium using an alcohol solution and applies an excimer laser (193 nm) by breaking the molecules' bonds to remove corneal tissue. A masking agent is used to smooth the cornea if the surface turns out rough. The patient needs to be examined at the slit lamp to ensure the target ablation has been reached.
- The surgeon puts in place a contact lens bandage to aid with healing and reduce pain
Risks, Side Effects & Complications
Bacterial infection can result from PTK. It is often mild and resolves on its own over time.
Complications arising from the procedure may include:
- Delay in epithelial healing
- Herpes simplex virus may get reactivated
- Recurrence of primary disease pathology
- Corneal haze (cloudy or opaque appearance) and scarring
After Care, Recovery & Results
Antibiotics, steroid eye drops, and moisturizing eye drops are prescribed. Patients are advised to strictly use the medications to help relieve any discomfort and help with healing. In case of pain, topical NSAIDs like Diclofenac sodium can help, and they carry the advantage of not interfering with epithelial healing. Patients are advised to avoid touching or rubbing the eye and should take things easy. They should also wear a plastic shield.
A patient’s eyesight appears hazy or blurry in the first week following surgery but settles down after one month. Full improvement should occur between three to six months after surgery. If only the top corneal layer was involved, then vision returns rapidly.
The epithelium’s delay in healing can result in infection and haze formation. If this happens, the eye can be patched, or a silicone hydrogel lens can be used to facilitate healing. The surgeon will prescribe antibiotic eye drops to be used until the epithelium is healed, and the silicone hydrogel lens is removed. Antibiotic ointment is instilled two times a day in case a patch has been used. Once the epithelium has healed, the patient must take topical corticosteroids four times daily for one month. The patient also takes topical lubricants four to six times per day for a month.
Research indicates that PTK is effective in over 90% of the cases with long-term results since it is minimally invasive. Some patients may require subsequent PTK (s) for better visual acuity.