Journal of Refractive Surgery

Brief Reports 

Phototherapeutic Keratectomy With Excimer Laser for Reis-Bückler's Corneal Dystrophy

Peter J McDonnell, MD; Theo Seiler, MD, PHD

Abstract

ABSTRACT

Two patients with decreased visual acuity and recurrent epithelial erosions due to Reís-Bückler's corneal dystrophy underwent phototherapeutic keratectomy with the 193-nanometer excimer laser. Because the epithelial surface was relatively smooth prior to surgery, ablations were performed through an intact epithelium. Postoperatively, visual acuity was improved and symptoms of erosion decreased in both patients. Although no refractive shift was intended with the phototherapeutic procedure, both patients were hyperopic following surgery. Superficial keratectomy with the 193nanometer excimer laser thus provides an alternative to conventional surgical keratectomy. [Refract Corneal Surg 1992;8:306-310.)

Abstract

ABSTRACT

Two patients with decreased visual acuity and recurrent epithelial erosions due to Reís-Bückler's corneal dystrophy underwent phototherapeutic keratectomy with the 193-nanometer excimer laser. Because the epithelial surface was relatively smooth prior to surgery, ablations were performed through an intact epithelium. Postoperatively, visual acuity was improved and symptoms of erosion decreased in both patients. Although no refractive shift was intended with the phototherapeutic procedure, both patients were hyperopic following surgery. Superficial keratectomy with the 193nanometer excimer laser thus provides an alternative to conventional surgical keratectomy. [Refract Corneal Surg 1992;8:306-310.)

Reis-Bückler's corneal dystrophy is an autosomal dominantly inherited disorder characterized by a grey-white, reticular subepithelial opacity that reduces visual acuity and results in recurrent epithelial erosions.1·2 Histopathologic studies have revealed this opacity to represent mounds of subepithelial fibrous tissue anterior to and replacing Bowman's membrane.3,4 Immunofluorescent and ultrastructural studies suggest that this material is of epithelial orìgin.5 This dystrophy may be confused with other conditions, such as annular and honeycomb dystrophy (Thiel-Behnke), but Weidle6 has demonstrated that Reis-Bückler's dystrophy has a characteristic maplike pattern of opacity and distinct histologic features.

Although lamellar and penetrating keratoplasties have been advocated for treating this dystrophy,7"9 Wood and colleagues3 described successful surgical removal of the subepithelial fibrous membrane by blunt surgical dissection. Schwartz and Taylor4 used this technique also, and concluded that superficial keratectomy is "the most appropriate surgical procedure for .... Reis-Bückler's corneal dystrophy." Superficial keratectomy with the 193-nanometer excimer laser has been used more recently to remove anterior corneal stromal opacities and to smooth irregular corneal surfaces.10 In this report, we describe successful management of Reis-Bückler's corneal dystrophy in two patients by phototherapeutic keratectomy with the 193-nanometer excimer laser.

CASE REPORTS

Case 1. The patient was a 43-year-old male with a 38-year history of decreased visual acuity and recurrent corneal epithelium erosions. A long family history of corneal dystrophy was obtained, with documented involvement of family members spanning five generations (Fig 1).

Refraction of - 3.00 - 1.50 × 160° in the right eye and -3.75 - 1.75 × 25° in the left eye produced best-corrected visual acuities of 20/10O + 2 and 20/80^sup -2^ in the right and left eyes, respectively. Slit-lamp microscopy revealed a smooth anterior epithelial surface and an irregular grey-white reticular opacity at the level of Bowman's membrane, with sawtoothlike elevations extending anteriorly into the basal layer of the epithelium resembling corneal dystrophy (Thiel-Behnke) (Fig 2). With an optical pachometer, the thickness of the opacity, including the overlying epithelium, was measured to be approximately 180 µ.

FIGURE 1: Pedigree of patient no. 1 with documented corneal disease involving five generations.

FIGURE 1: Pedigree of patient no. 1 with documented corneal disease involving five generations.

The patient was informed of the investigational nature of the 193-nanometer excimer laser, and the procedure, known risks, and alternatives weTe reviewed; after being fully informed, he elected to participate in the clinical trial of phototherapeutic keratectomy. Surgery was performed in the right eye by anesthetizing the eye with topical proparacaine and placing the patient in a supine position under the laser. A commercially-available medical excimer laser was used (Excimed UV200, Summit Technology, Waltham, Mass), that emitted laser light at a wavelength of 193 nm with a radiant exposure at the cornea of 180 mJ/cm2. Prior to treatment, the fluence and beam homogeneity were measured externally using a Gentec ED-500 joulemeter and gelatin filter. The internal repetition rate of the laser was 10 Hz. The computer was then set to perform a therapeutic ablation of 100-micrometer depth with an ablation rate of 0.26 µ per pulse. An ablation diameter of 5 mm was used. The patient was instructed to fixate on a coaxial fixation light. The plane of operation was defined by placing two crossed helium neon laser beams at the same point of focus. The eye was not grasped with a ring, and gas was not blown across the corneal surface during the ablation. Toward the end of the therapeutic ablation procedure, the patient's head was moved in a circular fashion by the surgeon so as to make the margin of ablation less sharply demarcated, and hopefully thereby minimize any induced corneal flattening. In addition, a 4.00-diopter myopic ablation was then performed to address the refractive error. A combination antibiotic (gentamicin 0.3%) and corticosteroid (dexamethasone 0.1% and homatropine 1%) ointment and a semi-pressure patch were placed on the eye at the conclusion of the procedure.

Postoperatively, the patient experienced moderate-to-severe pain for the first 24 hours, then complained of foreign body sensation until the cornea was reepithelialized at 48 hours after surgery. FoIlowing closure of the epithelial defect, the patient was instructed to apply fluorometholone 0.1% solution topically every 2 hours for 1 week, then four times daily. The corneal opacity was almost completely absent, and central corneal flattening was apparent with the slit-lamp microscope (Fig 3). The patient's vision gradually improved as the epithelial surface became more regular, but again the refraction demonstrated a hyperopic shift (Table). Because of the induced hyperopia, the patient has been fitted with a soft contact lens, which he wears successfully and which provides him with 20/30 acuity.

FlGURE 2: (A) SIrt-lamp microscope of patient 1 demonstrating anterior corneal opacity with broad beam Illumination. (B) High power demonstrates reticular pattern of the opacity.

FlGURE 2: (A) SIrt-lamp microscope of patient 1 demonstrating anterior corneal opacity with broad beam Illumination. (B) High power demonstrates reticular pattern of the opacity.

Case 2. The patient is a 37-year-old man with a family history of Reis-Bückler's corneal dystrophy. His mother had undergone bilateral penetrating keratoplasties for this condition 25 years previously. The patient reported progressive vision loss and occasional epithelial erosions, usually occurring during the night or upon awakening. This problem was improved, but not eradicated, by the use of hypertonic saline ointment at bedtime and therapeutic soft contact lenses.

FIGURE 3: (A,B) Slit-lamp microscope photographs of patient 1, 1 week after surgery, demonstrate improvement in corneal clarity and (C) central corneal flattening.FIGURE 4: Sit-lamp microscope photograph of patient 2 demonstrating reticular pattern of anterior corneal opacity preoperatively.TableRefractive Errors and Visual Acuities After Excimer Laser Phototherapeutic Keratectomy

FIGURE 3: (A,B) Slit-lamp microscope photographs of patient 1, 1 week after surgery, demonstrate improvement in corneal clarity and (C) central corneal flattening.

FIGURE 4: Sit-lamp microscope photograph of patient 2 demonstrating reticular pattern of anterior corneal opacity preoperatively.

Table

Refractive Errors and Visual Acuities After Excimer Laser Phototherapeutic Keratectomy

Refraction of -0.50 sphere in the right eye and - 1.25 sphere in the left eye produced best-corrected visual acuities of 20/200 and 20/70 in the right and left eyes, respectively. Slit-lamp microscopy revealed a smooth anterior epithelial surface and an irregular grey-white reticular opacity at the level of Bowman's membrane (Fig 4), with nodular elevations extending anteriorly into the basal layer of the epithelium. With an optical pachometer, the thickness of the opacity, including the overlying epithelium, was measured to be 100 µ.

After being informed of the investigational nature of the 193-nanometer excimer laser, and the procedure, known risks, and alternatives, the patient elected to participate in the clinical trial of phototherapeutic keratectomy. Surgery was performed in the more severely affected right eye by anesthetizing the eye with topical proparacaine and placing the patient in the supine position under the laser. A commercially-available medical excimer laser was used for this procedure (20/20 Excimer Laser, VISX, Ine, Sunnyvale, Calif), emitting laser light at a wavelength of 193 nm with a radiant exposure at the cornea of 160 mJ/cmp 2. Prior to treatment, the laser was calibrated by performing myopic ablations on polymethylmethacrylate blocks that were then read in the lensometer to confirm the accuracy and reproducibility of the refractive change. The computer was then set to perform a therapeutic ablation of 100µ-depth with an ablation rate of 0.31 µ per pulse and a repetition rate of 5 Hz. An ablation diameter of 6 mm was used. The patient was instructed to fixate on a coaxial fixation light, the eye was fixed in position by a vacuum ring equipped with three ports to blow nitrogen gas over the surface of the cornea (to remove debris liberated during the ablation), and the laser centered over the entrance pupil of the eye. Unlike case 1, the patient's head was not moved in an attempt to smooth the transition between ablated and unablated cornea. A combination antibiotic (tobramycin 0.3%) and corticosteroid (dexamethasone 0.1%) ointment and a semi-pressure patch were placed on the eye at the conclusion of the procedure.

Postoperatively, the patient experienced moderate-to-severe pain for the first 24 hours, then complained of foreign body sensation until the cornea was reepithelialized at 72 hours after surgery. Following closure of the epithelial defect, the patient was instructed to apply fluorometholone 0.1% solution topically every 2 hours for 1 week, then four times daily. The patient's vision gradually improved as the epithelial surface became more regular, but the refraction demonstrated a hyperopic shift (Table). Despite the hyperopic shift, the patient wears spectacles successfully, with acuity corrected to 20/15, and desires surgery for the fellow eye. The cornea was substantially clearer after surgery (Fig 5).

FIGURE 5: Silt-lamp microscope photograph of patient 2, 3 months after surgery demonstrates improvement in corneal clarity.

FIGURE 5: Silt-lamp microscope photograph of patient 2, 3 months after surgery demonstrates improvement in corneal clarity.

DISCUSSION

Anterior corneal opacities appear to be amenable to removal with superficial keratectomy using the excimer laser (a procedure termed phototherapeutic keratectomy) as an alternative to penetrating keratoplasty.10 Because the opacities in Reis-Bükler's corneal dystrophy are relatively superficial, and since Wood and colleagues have subsequently demonstrated success with superficial keratectomy rather than penetrating keratoplasty, we believe that phototherapeutic keratectomy is a straightforward approach to management of this condition. In our patients we observed a hyperopic shift after surgery. Because the depth of ablation should be uniform in phototherapeutic keratectomy, this result was unintended in patient 2. In patient 1, we combined therapeutic ablation with a myopic ablation designed to correct the preexisting myopia; in retrospect, this was unnecessary and probably contributed to the postsurgical hyperopia. Since we performed surgery on our patients, Sher et al10 reported on one patient who underwent phototherapeutic ablation for Reis-Bückler's dystrophy, who experienced a 7.25-diopter increase in hyperopia at 6 months after surgery, and noted that phototherapeutic keratectomy is commonly associated with induction of hyperopia. It is possible that some induced refractive change might result simply from removal of the fibrous tissue, whether or not the excimer laser is used for this purpose. Most papers describing conventional surgical management of Reis-Bückler's dystrophy with manual superficial keratectomy do not report the pre- and postoperative refractive errors. Schwartz and Taylor,4 however, described a patient who experienced substantial refractive changes with induction of mixed astigmatism after blunt dissection of the subepithelial fibrous tissue with a cyclodialysis spatula. In one eye of their patient, refraction changed from +2.75 + 0.50 ? 165° preoperatively to -1.50 + 5.25 X 115° postoperatively (change in spherical equivalent from + 3.00 to + 1.125). In the fellow eye, surgery altered refraction from +2.75 + 0.50 x 15° preoperatively to piano +4.50 X 145° postoperatively (change in spherical equivalent from +3.00 to +2.25). It may be that substantial refractive changes are typical after surgical therapy of Reis-Bückler's dystrophy, whether the abnormal tissue is stripped manually or removed with the excimer laser.

Sher et al10 performed manual removal of epithelium prior to performing phototherapeutic keratectomy in their patient with Reis-Bückler's dystrophy. Because the anterior epithelial surface is usually smooth in these eyes, while the fibrous membrane is nodular and irregular, we recommend ablating through the intact epithelium as part of the procedure, rather than first removing the epithelium. In this fashion, we believe the epithelium can help to leave the postoperative ablated surface smooth, much as has been described with the topical administration of fluids to mask deeper tissues while exposing protruding irregularities during the ablation.11,12 If the epithelium is removed manually at the beginning of the procedure, however, we believe use of a smoothing fluid would be appropriate.

REFERENCES

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2. Bücklers M. Ueber eine weitere familiare Hornhautdystropie (Reis), min Monatsbl Augenheilkd. 1949;114:386-397.

3. Wood TO, Fleming JC, Dotsoo RS, Cotteti MS. Treatment of Reis-Bückler's corneal dystrophy by removal of subepithelial fibrous tissue. Am J Ophthalmol. 1978;85:360-362.

4. Schwartz MF, Taylor HR. Surgical management of ReisBückler's corneal dystrophy. Cornea. 1985/1986;4:100-107.

5. Lohse E, Stock EL, Jones JCR, Braude LS, O'Grady RB, Roth SI. Reis-Bückler's corneal dystrophy. Immunofluorescent and electron microscopic studies. Cornea. 1989;8:200-209.

6. Weidle EG. DifFerentialdiaguose der Hornhautdystrophien vom Typ Groenouw I, Reis-Bücklers und Thiel-Behnke. Fortschritte der Ophthalmologie. 1989;86:265-271.

7. Rice NSC1 Ashton N, Jay B, Blach RK. Reis-Bückler's dystrophy. A clinico-pathologic study. Br J Ophthalmol. 1968; 52:577-603.

8. Hall P. Reis-Bückler's dystrophy. Arch Ophthalmol. 1974;91:170-173.

9. Grayson M, Wilbrandt H. Dystrophy of the anterior limiting membrane of the cornea (Reis-Bückler's type). Am J Ophthalmol. 1966;61:345-349.

10. Sher NA, Bowers RA, Zabel RW, et al. Clinical use of the 193-nm excimer laser in the treatment of corneal scars. Arch Ophthalmol. 1991;109:491-498.

11. Berlin H, Bende T, Seiler T. Corneal resurfacing by excimer laser photoablation. Invest Ophthalmol Vis Sci. 1988;29(suppl):310.

12. Kornmehl EW, Steinert RF, Puliafito CA. A comparative study of masking fluids for excimer laser phototherapeutic keratectomy. Arch Ophthalmol. 1991;109:860-863.

10.3928/1081-597X-19920701-11

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