The corneal epithelium is removed over the involved area by gently scraping with a dry cellulose sponge (Weck-cel) or a disposable scarifier blade (Grieshaber 681.01 or Beaver 59). After epithelial removal, the surface should be kept dry to facilitate visualization of subepithelial fibrous plaques or focal accumulations of aberrant basement membrane material. With the aid of a dry cellulose sponge, cleavage planes between the subepithelial fibrous tissue and Bowman's layer can often be located and exploited. After an edge of the subepithelial fibrous membrane is identified, the tissue can be stripped and peeled with the aid of jeweler's forceps, frequently as a continuous sheet, thereby leaving Bowman's layer unharmed. A scarifier may be used to gently scrape or dissect more firmly adherent tissue. Sharp incision or dissection should be avoided to prevent damage to the underlying Bowman's layer or stroma. The cleared corneal surface can be polished with a cellulose sponge or lightly scraped with a scarifier (Fig. 1).¹

Postoperatively, antibiotic ointment is applied and the eye is pressure-patched for 24 hours. Thereafter, antibiotic ointment is initially applied four times a day and reduced in frequency over 2 weeks. Re-epithelialization is usually complete in 5 to 7 days. Contact lens wear can be resumed after 2 weeks.

EPITHELIAL BASEMENT MEMBRANE DYSTROPHY (MAP DOT-FINGERPRINT DYSTROPHY)

Epithelial basement membrane dystrophy is the most common corneal dystrophy, affecting approximately 2% of the population.² Although most patients remain asymptomatic, about 10% experience recurrent corneal erosions as a consequence of faulty attachment complexes. These attachment complexes consist of hemidesmosomes of the basal epithelial cells, the underlying basement membrane, and the subadjacent anchoring fibrils of Bowman's layer.³ After an erosion, persistence of devitalized epithelium and fragments of basement membrane may inhibit normal re-epithelialization and formation of secure attachment complexes. Simple superficial debridement for removal of abnormal epithelium and basement membrane, thereby leaving a smooth substrate of Bowman's layer, can be performed at the slit lamp. The adjacent normal epithelium can resurface this area, allowing formation of competent attachment complexes and resulting in prompt cessation of erosive symptoms with much reduced frequency of recurrences.^4–6 This procedure can be employed if more conservative measures (i.e., lubricants, patching, bandage contact lenses) fail in halting the erosions.

A smaller subset of patients with epithelial basement membrane dystrophy experience reduction of vision and/or recurrent erosions from the extreme deposition of an abnormal basement membrane and fibrillar collagenous material between the epithelium and Bowman's layer.² This material may lead to irregular astigmatism and abnormal tear breakup. Patients typically complain of monocular visual distortion, diplopia, or “ghost images.” By performing superficial keratectomy, this abnormal material can be readily removed, leaving behind a smooth substrate of intact Bowman's layer. After re-epithelialization a smooth surface is re-established with the elimination of irregular astigmatism.

REIS-BÜCKLERS DYSTROPHY

Reis-Bücklers' dystrophy is an autosomal dominant condition characterized by the extensive accumulation of a fibrous subepithelial tissue that largely replaces Bowman's layer.² Secondarily defective epithelial attachment complexes result in severe recurrent erosions. The accumulations of fibrous tissue also cause irregular astigmatism and a reticular anterior corneal opacification with diminished vision. The anterior location of this dystrophic process makes it amenable to treatment by superficial keratectomy.^7,8 A dissection plane can frequently be developed between the fibrous tissue and the underlying normal stroma. Blunt dissection can then be used to peel the fibrous tissue until it is entirely removed (Color Plate 1: Color Fig. 1A-D). Our experience and that of others^7,8 have been very favorable with this technique in achieving cessation of the erosions and improvement of vision. The fibrous tissue may recur after some years, but the procedure can be easily repeated.

GRANULAR DYSTROPHY

Granular dystrophy is an autosomal dominant condition characterized by the subepithelial and stromal accumulation of an eosinophilic granular material. In advanced cases corneal transplantation is necessary for visual rehabilitation. A superficial variant of granular dystrophy has been described that primarily involves Bowman's layer and clinically and histologically resembles Reis-Bücklers' dystrophy. Transmission electron microscopy is necessary to identify the typical lesions of granular dystrophy in these cases. These superficial variants tend to have an earlier onset and higher frequency of erosive symptoms than typical granular dystrophy.^9,10 Fortunately, the predominantly anterior location of the lesions may allow for treatment by superficial keratectomy alone.

Granular dystrophy can recur in corneal grafts. The recurrences in grafted corneas frequently take the form of an avascular fibrous connective tissue between the normal epithelium and Bowman's layer.² The anterior location of recurrent fibrous tissue allows for easy removal from underlying Bowman's layer by superficial keratectomy.¹¹ Thus, repeat penetrating keratoplasty with its attendant risks can be avoided (Color Plate 2: Color Figs. 2A AND B; 3A and B).

KERATOCONUS

Keratoconus is an ectactic dystrophy characterized by progressive thinning of the central or paracentral cornea. Indications for corneal transplantation include corneal scarring in the visual axis causing visual reduction or intolerance of contact lenses necessary to correct irregular astigmatism. Some patients become intolerant to contact lenses owing to the formation of a raised, localized area of superficial cornea that is chronically abraded by the contact lenses. Moodaley and co-workers¹² have referred to this raised area as a “proud nebula,” and we have termed such a focal nodular scar as a “corneal callus.”¹³ Superficial keratectomy can be used to remove these focal fibrotic nodules and allow for resumption of contact lens wear. Penetrating keratoplasty can thereby be avoided in many appropriately selected cases.

Histopathologic evaluation of the excised fibrotic nodules reveals fibrillar collagen in random array with few interspersed fibrocytes. The overlying epithelium is fragmented with discontinuous, multilaminar basement membrane and diminished hemidesmosomes. The nodules are anterior to Bowman's layer, and hence, a plane of dissection can be created between the fibrous plaque and the underlying stroma, leaving stroma undisturbed (Fig. 2; Color Plate 3: Color Fig. 4A-C).

VERNAL KERATOPATHY

Vernal disease is a seasonally recurring, bilateral inflammation of the conjunctiva that occurs in children and young adults who have a history of atopy. Vernal keratopathy presents as punctate epithelial keratitis, subepithelial scarring, and large epithelial erosions with plaque formation. This plaque consists of a fibrin-like exudate that is resistant to medical therapy and can become chronic. The vernal plaque can be successfully removed by superficial keratectomy.¹⁴

SQUAMOUS CELL CARCINOMA

Corneal intraepithelial neoplasia refers to a spectrum of conditions ranging from a mild dysplastic process to carcinoma in situ. Invasive squamous cell carcinoma of the cornea is diagnosed when the dysplastic process breaks through the epithelial basement membrane. Squamous cell carcinoma of the cornea that is noninvasive can be successfully removed with superficial keratectomy. Supplemental cryotherapy has been advocated.¹⁵

OTHER CORNEAL DISORDERS

In our experience, other anterior corneal disorders that we have successfully managed with superficial keratectomy include the following: anterior corneal pannus of aniridia, calcific band keratopathy, bullous keratopathy with secondary amyloidosis (Color Plate 4: Color Fig. 5A-D), superficial pannus following chemical injury, residual scarring following pterygium removal, and Salzmann's nodular degeneration.

With this approach, anterior corneal dystrophies and scars have been successfully removed, thereby eliminating the need for penetrating keratoplasty in some patients. The excimer laser has also been used to treat intractable recurrent erosions¹⁶ as well as to smooth rough irregular corneal surfaces.^17,18 The main advantage of the excimer laser lies in its ability to remove deeper corneal opacities than are readily accessible by conventional superficial keratectomy. Its principal disadvantages relative to superficial keratectomy include induced hyperopia, high cost of instrumentation and operation, plus limited accessibility.

Although phototherapeutic keratectomy remains investigational and has shown promise in Food and Drug Administration-approved clinical trials as a comparable or potentially preferable alternative for the treatment of various conditions limited to the anterior cornea, we continue to prefer superficial keratectomy as the initial therapy of choice in these situations.

The simplicity of the procedure is most attractive. Once a dissection plane is established, the entire sheet of aberrant fibrous tissue can be peeled with forceps, thereby obviating the use of sharp instruments. Since the pathologic abnormality is frequently anterior to Bowman's layer, the difficulties with stromal scarring that can result from standard lamellar keratectomy can be avoided.

Recurrence of the pathologic process can certainly occur, and we have rarely observed this phenomenon in Reis-Bücklers' dystrophy, granular dystrophy, and keratoconus. Still, in patients who would otherwise be subjected to penetrating keratoplasty, the improvement in both vision and symptoms with less invasive procedures seems far preferable.

In summary, superficial keratectomy is a simple, extraocular, outpatient procedure with minimal risk of complications. Postoperative recovery is rapid, and the costs, patient restrictions, and potential complications of penetrating keratoplasty are avoided. There is a swift improvement of vision and decrease in erosive symptoms. Although the primary disease process may rarely recur, this minor surgical procedure can be repeated easily. Thus, we continue to recommend its use in these several degenerative and dystrophic disorders of the anterior cornea.

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