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Phototherapeutic Keratectomy (PTK)
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This is a therapeutic application of Excimer laser in the management of anterior corneal diseases and is a new technique of Keratectomy for removing the scar tissue from the cornea. The excimer laser may provide a novel modality in the treatment of a number of superficial corneal disorders. This treatment is known as Phototherapeutic Keratectomy. The indications include a variety of corneal degenerations and dystrophies, corneal irregularities, and superficial scars. While some of these conditions, could be treated by mechanical superficial Keratectomy techniques, PTK may minimise tissue removal and surgical trauma. The smooth stromal surface achieved by the excimer laser procedure may improve surface quality of the cornea, improve postoperative corneal clarity and decrease postoperative scarring and facilitate subsequent epithelial adhesion. Moreover superficial corneal disorders, which in some cases would otherwise require corneal transplant, may be amenable to treatment with the PTK procedure. Thus PTK has a dual approach in pain management and improving the visual acuity (removing scars).

Unlike LASEK or LASIK technique for correction of refractive errors, PTK treatments will vary with different corneal disorders and the clinical goals of the procedure may likewise vary depending upon the patient's symptoms.

Background of PTK

Historically anterior corneal diseases were managed medically by means of lubrication, bandage contact lenses or surgically by performing anterior stromal micropunctures, epithelial debridement or automated lamellar/penetrating keratoplasty. During the last 10 years the advent of the excimer laser has become a useful tool for therapeutic reasons, although is principally focussed on refractive surgery.

PTK Technique

The technique dependes upon the type and distribution of the pathology.

  • Large area photoablation
  • Focal Ablation
  • Smoothening Technique
  • Transepithelial
  • Basement Membrane Ablation
  • Manual Superficial Keratectomy combined with large area PTK
  • PTK with masking fluids
  • PTK with PRK

Post-PTK management

  • Bandage Contact Lens
  • Antibiotic eye drops
  • Analgesia
  • Sedation
  • Dark glasses

Complications

Following laser most patients will experience some amount of pain/discomfort for two to three days. Photophobia (light sensitivity) may continue for a couple of weeks.

Occasionally there will be a delayed healing up to 7 to 10 days.

There is always very small risk of infection.

In deeper ablations there will be some amount of Corneal haze which may persist for a few months.

There is a tendency for patients to go longsighted/shortsighted after treatment.

Sometimes dystrophic conditions may recur.

Clinical Outcomes of Phototherapeutic Keratectomy

Bristol Eye Hospital, Bristol, U.K.
Mundasad, M.V., Ross, A.H., Tole, D.M.

Abstract

To evaluate the outcome of Phototherapeutic keratectomy (PTK) in the management of anterior corneal diseases.

Setting Bristol Eye Hospital, Bristol/Optimax Laser Eye Clinic

Methods A retrospective review of all patients who underwent PTK between March 2001 until November 2003 for anterior corneal diseases. Patients were assessed as to whether the indication for PTK was for visual improvement or for ocular surface improvement, and hence divided into a Visual group and Non-Visual Group.Further data including pre and postoperative unaided VA, BCVA, ablation depth, spherical equivalent and complications were collected. In addition, patients within the Non-Visual Group were contacted recalled to determine whether they had further symptoms.

Results A total of 39 eyes of 29 patients underwent PTK for various corneal disorders. In the visual group, there were 19 eyes of 14 patients and in the non-visual group 20 eyes of 15 patients.Within the visual group, the BCVA remained stable or improved in 100% of the group. 10 eyes had stable post-operative refractions, 6 developed a hyperopic shift and 3 had a myopic shift. Of the eyes in the non-visual group, 80% had significant improvement in symptoms.

Conclusions Phototherapeutic keratectomy is a valuable technique in treating recalcitrant anterior corneal disease for both visual improvement as well as symptomatic relief.

Introduction

The advent of the excimer laser has brought about a new method in the treatment of anterior corneal diseases and smoothing surface irregularities. Apart from various types of keratoplasty, existing treatment modalities for anterior corneal diseases include lubricants, bandage contact lenses, stromal micropuncture as well as epithelial debridement.1
Here, we describe the results of our experience in Phototherapeutic Keratectomy (PTK) for the treatment of a diverse range of anterior corneal pathology.

Patients & Methods

Thirty-nine eyes of 29 patients who had Phototherapeutic Keratectomy (PTK) for various anterior corneal diseases (Table 1) in Bristol between March 2001 and November 2003 were analyzed. The patients had been refractory to other forms of treatment. All had attempted use of ocular lubricants, 16 had tried a bandage contact lens, 3 had micropuncture, 3 had epithelial debridement and 2 had received a corneal graft prior to PTK.
All procedures were performed by a single surgeon (MV Mundasad). Patients were assessed as to whether the indication for PTK was for visual rehabilitation (Visual Group) or to alleviate symptoms such as pain and discomfort (Non-Visual Group).
The preoperative and postoperative examinations included uncorrected and best corrected visual acuity, spherical equivalent, as well as subjective symptoms within the Non-Visual Group. Laser ablation depth, complications as well as number of clinic visits pre- and postoperatively were also noted.
Subjective symptoms were assessed via an initial letter as well as a follow-up telephone questionnaire.
All treatments were performed with a NIDEC EC5000 laser, using an optical zone of 6.5mm and a transition zone varying between 7.5 to 9.0mm.
Postoperative management consisted of an eye pad, topical antibiotics, sedatives and NSAIDs.
Treatment was carried out on an outpatient basis and there was a minimum clinic follow up of 3 months.

Table 1. Preoperative corneal diseases

Visual Group Number of Eyes
Band Keratopathy 8
Reis Bucklers 8
Corneal Scar 2
Lattice Dystrophy 1
Non-Visual Group Number of Eyes
Basement Membrane Epithelial Dystrophy 12
Bullous Keratopathy 6
Erosions secondary to trauma 2

For 2 eyes, Phototherapeutic Keratectomy was combined with Photorefractive Keratectomy (PRK).

Results

Thirty-nine eyes of 29 patients were treated with PTK for various anterior corneal diseases.

Visual Group

In the visual group, there were 19 eyes of 14 patients. Within the group, age ranged from 13 to 89 years with a mean age of 62 years. BCVA was improved or unchanged in 19 eyes (100%) of the visual group. Figure 1 shows the gain and loss of BCVA within the visual group at follow up.

Visual Group: Gain/Loss Sneilen BCVA
Eyes with a diagnosis of Reis Bucklers syndrome had a mean hyperopic shift of 1.5 2.5D and those with a diagnosis of Band Keratopathy had a mean hyperopic shift of 0.5 1.5D.
Out of the 19 eyes, 10 had no significant refractive change ( 1.00D), 3 had a significant myopic shift (mean -1.68) and 6 had a significant hyperopic shift (mean +2.50D). There were 2 cases of delayed epithelial healing, 1 case of mono-ocular diplopia and 5 cases of haze, all graded as 0.5 on a haze scale.

Non Visual Group

In the non-visual group, there were 20 eyes of 15 patients. Age ranged from 27 to 89 years, with a mean age of 55 years. Although, not the primary indication for PTK treatment within the non-visual group, BCVA was improved or unchanged in 16 eyes (80%) of the group. Two eyes had a loss of 1 snellen line and 1 eye lost 4 snellen lines at follow up, secondary to a branch retinal vein occlusion.
A mean ablation depth of 70 microns was used for eyes with a diagnosis of bullous keratopathy and a mean ablation depth of 12 microns was used for eyes with corneal erosion syndrome.
2 eyes with corneal erosion syndrome received photorefractive keratectomy (PRK) in combination with the PTK resulting in 6/6 snellen vision in both eyes.
80% of the non-visual group had no further symptoms of pain and discomfort at a period of 6 months to 3 years following initial treatment. 1 patient had further symptoms post laser requiring a second PTK treatment.
Out of the 20 eyes, there were 6 cases of haze at follow up, all graded as 0.5 on a haze scale.

Discussion

Within the UK, phototherapeutic keratectomy is in many respects still in the early stage of development. It is still not widely available for treatment for anterior corneal diseases in many health authorities.
A good outcome of PTK depends on careful patient selection, detailed pre-operative evaluation as well as the skills and technique of the PTK procedure itself.
The success of excimer laser corneal surgery depends on its ability to remove corneal tissue without resulting in significant collateral damage.
The main adverse effect from PTK is postoperative refractive changes.2 All types of refractive change can occur but the greatest risk is of hyperopic shift3, due to central flattening of the cornea, which is related to ablation depth.
In our study, within the visual group, we achieved an overall success rate of 100% in improving BCVA. With regard to the non-visual group, our experience suggests that PTK is an effective treatment in alleviating symptoms of pain and discomfort, with improvement of symptoms in 80% of cases. Within the latter group, it was noted that many of these patients had a measurable improvement in Snellen Visual acuity. This most likely represents a more stable corneal epithelium and decreased photophobia.
It was noted that 3 patients within the visual group had a small myopic shift. This was thought to be due to uneven laser energy distribution due to prolate shape of the cornea, effect of plume, as well as possible unreliable prelaser refraction.

On the basis of our results, we conclude that PTK is an effective procedure in treating a diverse range of recalcitrant anterior corneal diseases.4 Not only does it have the ability to improve vision but also to alleviate symptoms of pain and discomfort.
Excimer laser PTK is a safe and effective modality, providing an alternative to procedures such as lamellar or penetrating keratoplasty in certain anterior corneal diseases.

  1. Hykin PG, Foss AE, Pavesio C, Dart JKG. The natural history and management of recurrent corneal erosion: a prospective randomized trial. Eye 1994; 8:35-40
  2. Gartry D, Kerr Muir M, Marshall J. Excimer laser treatment of corneal surface pathology: a laboratory and clinical study. Br J Ophthalmology 1991; 75:258-269
  3. Dogru M, Katakami C, Yamanaka A. Refractive changes after excimer laser phototherapeutic keratectomy. J Cataract Refract Surg 2001; 27:686-692
  4. Fagerholm P, Fitzsimmons TD, Orndahl M, Ohman L, Tengroth B. Phototherapeutic keratectomy with the excimer laser: long-term follow up results in 166 treated eyes. Refractive and Corneal Surgery 1993; 9:S76-81
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Laser Eye Surgery. Excimer laser techniques to correct myopia and astigmatism.