Thomas Fitzsimmons

EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA; CLINICAL RESULTS IN SIGHTED EYES

PURPOSE To evaluate the refractive results of excimer laser photorefractive keratectomy (PRK) performed on normal, sighted myopic eyes; to assess the role of postoperative topical steroid treatment in patients with PRK; and to study the regression of effect. METHODS An argon fluoride 193-nm excimer laser was used. Photorefractive keratectomy was performed on 420 eyes with preoperative refraction ranging from -1.25 to -7.50 diopters (D). Minimum follow-up time was 12 months, and 194 of the eyes were followed for 15 months. Postoperative treatment generally consisted of topical dexamethasone for 3 months, but in a sub-study, some eyes were treated for only 5 weeks. RESULTS Mean refraction (spherical equivalent +/- standard deviation) at 12 months was -0.04 +/- 0.84 D and at 15 months -0.22 +/- 0.78 D. At 12 months postoperatively, 86% of the eyes were within 1.00 D of emmetropia, at 15 months 87%. At 12 months, 91% of the eyes had an uncorrected visual acuity of at least 20/40, at 15 months 87%. Eyes treated with dexamethasone for 3 months regressed significantly less than those treated for only 5 weeks (P < 0.01). Dexamethasone also was effective in reversing regression later in the postoperative course. Eyes with preoperative myopia up to 4.90 D had significantly better refractive results at 12 months than eyes with myopia ranging from 5.00 to 7.50 D (P < 0.01). CONCLUSION These data show that excimer laser PRK can correct myopia with good predictability. Results at 12 and 15 months tend to suggest stability of postoperative refraction. Regression of effect was more common in higher myopes. Topical steroids postoperatively seem to play a crucial role for the refractive result.

Phototherapeutic keratectomy: long-term results in 166 eyes.

One hundred sixty-six eyes with corneal disease were treated with the excimer laser in order to ablate opacities, irregularities, or to improve wound healing. Postoperative follow up time was 15 months (range 6 to 28 months). An individual goal was set for each patient and 84% achieved the goal. The visual acuity change is given for each subgroup. Phototherapeutic keratectomy (PTK) was shown to be an advantageous surgical method, where the success is in the careful preoperative evaluation. One problem with the technique is the induced hyperopia.

Treatment of corneal dystrophies with excimer laser

Abstract Thirty‐three eyes with different corneal dystrophies underwent phototherapeutic keratectomy to ablate corneal opacities, surface irregularities and corneal wounds. For most patients the treatment goal was to improve vision but also corneal woundhealing, glare problems and unstable refraction were indications for treatment. In 27 eyes with the treatment goal to improve vision, 23 improved 2 lines or more on the visual chart used. In none of the patients has the treatment led to a worsening of the condition. The mean follow‐up time was 9 months. Excimer laser ablation of corneal dystrophies seems to be a good treatment, which can improve visual functions considerably, heal corneal wounds and in this way postpone corneal grafting in many cases.

Steroid Treatment of Myopic Regression: Acute Refractive and Topographic Changes in Excimer Photorefractive Keratectomy Patients

We documented acute changes in corneal topography and refraction after readministration of topical steroids in five patients with myopic regression after photorefractive keratectomy (PRK). One was a high myope (-10.00 sphere); the others were moderate myopes (preoperative spherical equivalents -4.25 to -6). All patients had been off steroids for 3 to 8 months before reinstitution. The changes in refractive spherical equivalents ranged from +0.75 to +3.00 diopters, and were observed from 6 days to 4 weeks later. Refractive hyperopic shifts were accompanied by pronounced corneal flattening as measured by computer-assisted corneal topographic analysis. Two to seven months later, three patients have become even less myopic, and two patients have again become slightly more myopic. Topical steroid use can modulate refractive changes after excimer laser treatments in some patients.

REACTIVE FORMATION OF HYALURONIC ACID IN THE RABBIT CORNEAL ALKALI BURN

Abstract The presence and distribution of reactively formed hyaluronic acid (HA) was assessed in the rabbit cornea following a penetrating alkali burn. The injury was inflicted by applying a round, 5.5 mm, filter paper soaked in 1 N NaOH centrally on the cornea for 60 seconds.

Reactive formation of hyaluronic acid after small and large lens injury

Abstract The reactive production of hyaluronic acid was studied in the rabbit lens following a 4 mm in diameter anterior lens wound, and following a large lens wound (extracapsular cataract extraction). Furthermore, human post‐mortem after‐cataract specimen were also studied. The hyaluronic acid was localized histochemically using a new specific technique. Hyaluronic acid in the small wound was localized in the primary sealing plug that precedes the reepithelialization and new capsule formation. In the large wound hyaluronic acid was found around the cells proliferating on the posterior capsule. The same was true in the human after‐cataract specimen. It was concluded that the primary wound sealing and the posterior capsule cellular outgrowth constitute similar cellular responses.

Superficial keratectomy with the 193 nm excimer laser a reproducible model of corneal surface irregularities

Abstract Rough corneal surfaces may be smoothed by performing a superficial keratectomy with the 193 nm excimer laser. In order to smooth an irregular surface, a substance must be used during ablation to protect low corneal areas so that high spots are ablated preferentially. A simple, accurate, and reproducible method for modelling various corneal surface irregularities was developed. The technique uses the excimer laser to imprint the patterns of various metallic grids onto the stromal surface. The model was used to facilitate a comparison of three potential smoothing agents: 0.5% tetracaine, 2% hydroxypropylmethylcellulose, and a fluorescein‐containing hyaluronate preparation. Preliminary results indicate that tetracaine may be the most efficacious smoothing agent.

Nebulae at keratoconus - the result after excimer laser removal

Abstract. Ten patients underwent excimer laser ablation due to nebula formation at keratoconus. The nebulae interfered significantly with contact lens fit or wearing time. The mean follow‐up time in these patients was 16.5 months. Following surgery all patients could be successfully fitted with a contact lens and thereby obtain good visual acuity. Furthermore, contact lens wearing time was 8 hours or more in all cases. In 2 patients the nebulae recurred but were successfully retreated.