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Cautery of Bowman's Membrane
CAUTERY O F BOWMAN'S MEMBRANE R. LINSY FARRIS, M.D.,
TAKEO IWAI IOTO, M.D.,
AND A. G. DEVOE,
M.D.
New York, New York The initial symptoms of corneal edema are blurring of vision and foreign body sensa tion. If endothelial decompensation becomes more severe, the edema worsens with further decrease in vision and pain due to the forma tion and rupture of epithelial blisters. Lowered intraocular pressure or topically applied osmotic agents may clear the cornea partially and permit the disappearance of subepithelial bullae. In many cases, however, such measures are not helpful, and the pa tient continues to have severe corneal edema with painful bullous keratopathy. One of us (A.G.D.) introduced electrocautery of Bowman's membrane in this country for relief of painful bullous kerato pathy in the fall of 1964 after observing Salleras's use of this technique in Argentina. 1 Results of the initial 20 cases were later re ported.2 A total of 118 procedures on 108 eyes have been done at the Edward S. Harkness Eye Institute by 27 different surgeons from Nov. 10, 1964, until March 15, 1973. Eight surgeons did four or more procedures, including 46 procedures by one of us (A.G.D.), and 19 surgeons did one to three procedures. One hundred eyes after cautery of Bowman's membrane were evaluated by means of a review of the medical record. Average follow-up time was two years, four months, with a range of one month to 5y~> years. Eight eyes are not reported either due to an inadequate follow-up, i.e., less than one month, or due to unavailability of the medi cal records. From the Edward S. Harkness Eye Institute, Columbia-Presbyterian Medical Center, New York, New York. This study was supported by Public Health Service research grant EY-00190-17 from the National Eye Institute. Reprint requests to R. Linsy Farris, M.D., Ed ward S. Harkness Eye Institute, 635 W. 165th St., New York, NY 10032.
SUBJECTS AND METHODS
Patients were selected for cautery of Bow man's membrane because of painful bullous keratopathy. Relief of pain and a quiet uninflamed eye were the goals of therapy. Pa tients understood that no improvement in vi sion could be expected and that poorer vision was more likely. In some cases, corneal trans plants were done later to improve vision. Corneas that appeared soft, with ulceration or thinning, were avoided and not treated by cautery of Bowman's membrane. In the operating room, the patient was sedated and cocaine was applied topically. Scraping with a No. 15 Bard-Parker blade removed the epithelium from the cornea. After removal of the epithelium, electrodiathermy applications were applied from the periphery of the cornea in a circular fashion until the entire surface of the cornea had been covered. The average size cornea required approximately 700 applications. The Bovie electrosurgical unit was used for diathermy applications with the selector switch set to diathermy and the power controls set to 0. We used a blunt tip diathermy probe and no grounding plate. The activating pedal was continuously depressed and diathermy was made by lightly touching the tip to Bowman's membrane, producing a splintering effect in superficial stroma. Slight sparking occurred as the tip touched Bowman's membrane and a thin coagulum formed. In two cases, sufficient shrinkage of the cornea occurred so that intra ocular pressure increased, necessitating a paracentesis to relieve intraocular pressure at the end of the procedure. After the diathermy applications, Neo-Cortef ointment and mon ocular dressings were applied to the eyelids. Histologic material was obtained after keratoplasty when corneal buttons were re-
VOL. 77, NO. 4
CAUTERY OF BOWMAN'S MEMBRANE
moved from patients previously treated for painful bullous keratopathy with cautery of Bowman's membrane. The corneal buttons were preserved in glutaraldehyde solution (3.5 to 4%)—one half prepared for electron microscopy and one half sent to Eye Pathol ogy for staining with hematoxvlin and eosin, Masson's trichrome, toluidine blue, alcian blue, and PAS reaction. A fresh eye-bank eye from a 16-year-old boy who died of sepsis was treated with electrocautery of Bowman's membrane and pre served immediately in 10% formalin solution for light microscopy. Cautery of Bowman's membrane in the eye-bank eye was performed with Bovie, Cameron-Miller, and Medical In strument Research Associates, Inc. (MIRA) electrocautery maahines.
549
RESULTS
Numerous depressions were observed in the corneas of patients after electrocautery applications with the Bovie machine. A thin eschar was present, which disappeared with in the first 24 hours. Complete healing with epithelialization of the cornea and freedom from staining with fluorescein required two to three weeks. Small multiple subepithelial white opacities at the points of diathermy application were visible during the first two to three months after treatment; however, these became progressively less apparent. Figure 1 shows the structure of the eyebank eye after electrocautery applications with different cautery units. The Bovie unit produced the depressions through Bowman's membrane and superficial stroma (Fig. 1,
Fig. 1 (Farris, Iwamoto, and DeVoe). Light micrographs of fresh human cornea from eye-bank eye after cautery of Bowman's membrane with Bovie (top) and M I R A (bottom) electrosurgical machines. The Bovie unit produced depressions through Bowman's membrane and superficial stroma (top, a r r o w ) . The high frequency electrodiathermy units of Cameron-Miller and M I R A did not produce breaks (bottom, arrow) (X148).
SSO
AMERICAN JOURNAL OF OPHTHALMOLOGY
top, a r r o w ) . The high-frequency electrodiathermy units of Cameron-Miller and M I R A did not produce breaks through Bowman's membrane (Fig. 1, bottom, a r r o w ) . Light and electron microscopy of the corneal buttons removed at keratoplasy from two patients who had previously undergone cautery of Bowman's membrane revealed that in both corneas, an extensive subepithelial connective tissue of varying thickness was formed between the epithelium and the Bow man's membrane, over almost the entire cor neal regions studied (Figs. 2 and 3 ) . P r o b ably due to the effect of cautery, the Bow man's membrane (or layer) was often dis rupted, and its gaps were filled with an ex tension of stromal connective tissue, which was further continuous anteriorly with the subepithelial connective tissue (Figs. 2, and 3, t o p ) .
APRIL, 1974
Of 100 eyes treated with cautery of Bow man's membrane, 75 had complete relief of pain with one treatment and eight had com plete relief of pain when another treatment was done for a few remaining bullae. Fifteen eyes had marked relief of pain with one treatment but continued to complain of slight discomfort manifested as tearing or mild foreign body sensation. There were two complications—a per forated cornea, noted at the end of the pro cedure when the last few applications were made centrally, and a descemetocele forming in the postoperative course. Both of these eyes had severe glaucoma, and one patient had refused to have enucleation. Eighteen of the 100 eyes studied had glau coma and elevation of intraocular pressure prior to cautery of Bowman's membrane. Of the eyes with bullous keratopathy and glau coma, nine had complete relief of pain with one treatment, and two eyes had a similar result after the treatment was repeated. Five eyes continued to have slight discomfort after one treatment and the two complications of perforation and descemetocele formation were in this group of eyes with glaucoma and elevated intraocular pressure.
The newly formed subepithelial connective tissue was composed of many active fibroblasts and collagen fibrils of various diame ters, ranging from 10 to 40 nm (Figs. 2, and 3, bottom). While the fibrils with approxi mately 30 nm in diameter, slightly larger than those of normal corneal stroma (20 to 25 nm in diameter), predominated, there was also a considerable number of thin fibrils (approxi DISCUSSION mately 10 nm in diameter) (Fig. 3, bottom). T h e interfibrillar spaces were usually wider Various treatments have been suggested than those in the stroma, and contained fine for relieving the pain associated with bul filamentous elements (Fig. 3, bottom). This lous keratopathy. A conjunctival flap as pro was typically observed in one case in which posed by Gundersen was probably one of the the corneal epithelium appeared normal (non- earliest forms of therapy. 3 Scarification uti edematous) over the wide central regions lizing trichloroacetic acid has also been rec 1 studied, indicating a successful result of cau ommended. More recently, replacement of tery procedure in these areas. Histochemical the epithelium with a glued-on hard contact staining of the other half specimen showed lens offered the possibility of improved vi 7 that the corresponding subepithelial connec sion as well as relief of pain/'" However, tive tissue was stained more intensively than epithelium eventually grew under these the stroma with P A S (Fig. 3, middle) and lenses, which then came off. In some cases alcian blue, although toluidine blue demon osmotic agents can provide improvements in strated no clear metachromasia. These sug vision as well as relief from pain, and in gested a considerable amount of mucopoly- ■cases of moderately elevated intraocular pres saccharides present within the widened inter sure, antiglaucoma agents lower the intra fibrillar spaces of the subepithelial connective ocular pressure sufficiently to improve vision. However, a number of patients have such tissue.
XS'^.'.jft'
Fig. 2 (Farris, Iwamoto, and DeVoe). Electron micrographs of corneal buttons removed from two pa tients previously treated with cautery of Bowman's membrane showing subepithelial connective tissue ( S C T ) associated with superficial stroma through breaks (arrow) of Bowman's membrane ( B m ) . E indicates epithelium, and f, active fibroblasts with well-developed rough-surfaced endoplasmic reticulum (top, x3,000; bottom, x 10,000.)
552
AMERICAN JOURNAL OF OPHTHALMOLOGY
,:^ac.-r*T_;
APRIL, 1974
:'*««B!fe
Fig. 3 (Farris, Iwamoto, and DeVoe). Same corneas as in Figure 2, bottom; the patient had been treated with cautery of Bowman's membrane. Top, Light micrograph of Masson's trichrome-stained section. A thick subepithelial connective tissue ( S C T ) seems to arise from stroma ( S T ) through breaks of Bow man's membrane (arrows) (X148). Middle, Light micrograph of PAS-stained section. Subepithelial connective tissue ( S C T ) is stained more intensively than the stroma ( S T ) ( X l 4 8 ) . Bottom, Electron micrograph of subepithelial connective tissue, showing thick (c) and thin (t) collagen fibrils. InterfibriUar spaces are relatively large, and often contain fine filamentous elements (arrows) (X37,000).
VOL. 77, NO. 4
CAUTERY OF BOWMAN'S MEMBRANE
severe stromal changes that vision is not im proved even though use of these agents pre vents the formation of bullae. In these cases, the primary consideration is relief of pain and overcoming the inflammation associated with rupturing of the epithelial bullae. Pene trating keratoplasty may not be indicated in some of these cases because of previous nerve damage due to glaucoma, macular de generation, or good vision in the opposite eye. In some such severely damaged, painful eyes, the patient may refuse enucleation. Cautery of Bowman's membrane provides a simple, direct method of eliminating the painful epithelial bullae and can improve the condition of the cornea for later penetrating keratoplasty when it is indicated. Also, cos metic scleral shells can be used once the cornea is well healed and no longer painful. The superficial scarring or subepithelial connective tissue produced by cautery of Bowman's membrane provides a barrier to the passage of fluid beneath the epithelium. The histologic section revealed perforation of stromal connective tissue through the breaks in Bowman's membrane with spread ing of connective tissue over the broken seg ments of the Bowman's membrane. Of some interest is the fact that the interfibrillar space in the newly formed connective tissue is ac tually greater than that seen in the normal corneal stroma. Thus, the increased resistance of fluid flow in the tissue must be explained on the basis of changes in the ground sub stance, which are also indicated by the modi fied staining pattern of this layer seen in pathologic specimens after cautery of Bow man's membrane. The spark-gap generated current of the Bovie electrocautery unit produced breaks through Bowman's membrane in the fresh eye-bank eye only. Although the constant, crystal-controlled high-frequency currents are preferred for diathermy applications in retinal detachment surgery,8 the increased tissue destructiveness of the lower, mixed frequencies of the monoterminal spark-gap generated current was necessary to produce
553
breaks in Bowman's membrane and superfi cial stromal destruction. Previous clinical studies have also confirmed this inadequate tissue destruction with higher frequency electrodiathermy machines. Ninety-eight percent of the patients bene fited from cautery of Bowman's membrane in terms of pain relief. There were complica tions in two patients ( 2 % ) . Repeat treat ments seemed necessary only when the cau tery applications were too widely spaced or covered an inadequate area. Localized cau tery of epithelial blister formation necessi tated extension of the treatment a millimeter beyond the area of epithelial edema. The two complications occurred in eyes that were probably too edematous for this type of treatment. Both had severe glaucoma and the corneas were considered quite edematous, even "mushy" or waterlogged. As a result, excessive deep stromal destruction took place rather than being confined to Bowman's membrane and superficial stroma as occurs in the usual cases of bullous keratopathy with mild to moderate edema of the corneal stroma. Glaucomatous eyes appeared to respond less favorably to cautery of Bowman's mem brane compared to normotensive eyes. A smaller proportion of these eyes had com plete relief of pain with one treatment, and the two complications occurred in this group. Better control of the intraocular pressure prior to cautery of Bowman's membrane would no doubt decrease stromal edema and limit the extent of tissue necrosis to the superficial layers. Reepithelialization occurred slowly after cautery of Bowman's membrane, sometimes requiring as long as six weeks. Patching en couraged complete covering by epithelium. Collagenase inhibitors may prevent ulceration during this time but were not required in these cases. SUMMARY
One hundred eyes with painful bullous keratopathy treated with cautery of Bow-
554
AMERICAN JOURNAL OF OPHTHALMOLOGY
man's membrane had marked to complete re lief of pain in 98% of the group. There were two failures, which were also the two complications—perforated cornea and a descemetocele, both in edematous corneas of severely glaucomatous eyes. Light and elec tron microscopy demonstrated an extensive subepithelial connective tissue, probably formed by an extension of stromal con nective tissue through the breaks in Bow man's membrane, and suggested the ground substance in this new tissue to be responsible for increased resistance to edema fluid and prevention of subepithelial bullae. REFERENCES
1. Salleras, A.: Bullous keratopathy. In King, J. H., Jr., and McTigue, J. W. (eds.) : The Cornea. World Congress. Washington, Buttersworths, 1965, p. 292.
APRIL, 1974
2. DeVoe, A. G.: Electrocautery of Bowman's membrane. Trans. Am. Ophthalmol. Soc. 64:109, 1966. 3. Gundersen, T.: Conjunctival flaps in the treat ment of comeal disease with reference to a new technique of application. Arch. Ophthalmol. 60:880, 1958. 4. Gifford, S. R.: The mild form of epithelial dystrophy of the cornea. Arch. Ophthalmol. 7:18, 1932. 5. Gasset, A. R., and Kaufman, H. E.: Epikeratoprosthesis. Replacement of superficial cornea by methyl methacrylate. Am. I. Ophthalmol. 66:641, 1968. 6. Dohlman, C. H., Carroll, J. M., Ahmad, B., and Refoyo, M. F.: Replacement of the corneal epithelium with a contact lens. Trans. Am. Acad. Ophthalmol. Otolaryngol. 73:482, 1969. 7. Farris, R. L., and Willcockson, T. H.: Gluedon contact lenses. Clinical studies. In Polack, F. M. (ed.) : Corneal and External Diseases of the Eye. First Inter-American Symposium. Springfield, 111., Charles C Thomas, 1970, p. 207. 8. Pomerantzeff, O.: Photocoagulators and sur gical diathermy. Am. J. Med. Electronics 3:237, 1964.
TAKEO IWAI IOTO, M.D.,
AND A. G. DEVOE,
M.D.
New York, New York The initial symptoms of corneal edema are blurring of vision and foreign body sensa tion. If endothelial decompensation becomes more severe, the edema worsens with further decrease in vision and pain due to the forma tion and rupture of epithelial blisters. Lowered intraocular pressure or topically applied osmotic agents may clear the cornea partially and permit the disappearance of subepithelial bullae. In many cases, however, such measures are not helpful, and the pa tient continues to have severe corneal edema with painful bullous keratopathy. One of us (A.G.D.) introduced electrocautery of Bowman's membrane in this country for relief of painful bullous kerato pathy in the fall of 1964 after observing Salleras's use of this technique in Argentina. 1 Results of the initial 20 cases were later re ported.2 A total of 118 procedures on 108 eyes have been done at the Edward S. Harkness Eye Institute by 27 different surgeons from Nov. 10, 1964, until March 15, 1973. Eight surgeons did four or more procedures, including 46 procedures by one of us (A.G.D.), and 19 surgeons did one to three procedures. One hundred eyes after cautery of Bowman's membrane were evaluated by means of a review of the medical record. Average follow-up time was two years, four months, with a range of one month to 5y~> years. Eight eyes are not reported either due to an inadequate follow-up, i.e., less than one month, or due to unavailability of the medi cal records. From the Edward S. Harkness Eye Institute, Columbia-Presbyterian Medical Center, New York, New York. This study was supported by Public Health Service research grant EY-00190-17 from the National Eye Institute. Reprint requests to R. Linsy Farris, M.D., Ed ward S. Harkness Eye Institute, 635 W. 165th St., New York, NY 10032.
SUBJECTS AND METHODS
Patients were selected for cautery of Bow man's membrane because of painful bullous keratopathy. Relief of pain and a quiet uninflamed eye were the goals of therapy. Pa tients understood that no improvement in vi sion could be expected and that poorer vision was more likely. In some cases, corneal trans plants were done later to improve vision. Corneas that appeared soft, with ulceration or thinning, were avoided and not treated by cautery of Bowman's membrane. In the operating room, the patient was sedated and cocaine was applied topically. Scraping with a No. 15 Bard-Parker blade removed the epithelium from the cornea. After removal of the epithelium, electrodiathermy applications were applied from the periphery of the cornea in a circular fashion until the entire surface of the cornea had been covered. The average size cornea required approximately 700 applications. The Bovie electrosurgical unit was used for diathermy applications with the selector switch set to diathermy and the power controls set to 0. We used a blunt tip diathermy probe and no grounding plate. The activating pedal was continuously depressed and diathermy was made by lightly touching the tip to Bowman's membrane, producing a splintering effect in superficial stroma. Slight sparking occurred as the tip touched Bowman's membrane and a thin coagulum formed. In two cases, sufficient shrinkage of the cornea occurred so that intra ocular pressure increased, necessitating a paracentesis to relieve intraocular pressure at the end of the procedure. After the diathermy applications, Neo-Cortef ointment and mon ocular dressings were applied to the eyelids. Histologic material was obtained after keratoplasty when corneal buttons were re-
VOL. 77, NO. 4
CAUTERY OF BOWMAN'S MEMBRANE
moved from patients previously treated for painful bullous keratopathy with cautery of Bowman's membrane. The corneal buttons were preserved in glutaraldehyde solution (3.5 to 4%)—one half prepared for electron microscopy and one half sent to Eye Pathol ogy for staining with hematoxvlin and eosin, Masson's trichrome, toluidine blue, alcian blue, and PAS reaction. A fresh eye-bank eye from a 16-year-old boy who died of sepsis was treated with electrocautery of Bowman's membrane and pre served immediately in 10% formalin solution for light microscopy. Cautery of Bowman's membrane in the eye-bank eye was performed with Bovie, Cameron-Miller, and Medical In strument Research Associates, Inc. (MIRA) electrocautery maahines.
549
RESULTS
Numerous depressions were observed in the corneas of patients after electrocautery applications with the Bovie machine. A thin eschar was present, which disappeared with in the first 24 hours. Complete healing with epithelialization of the cornea and freedom from staining with fluorescein required two to three weeks. Small multiple subepithelial white opacities at the points of diathermy application were visible during the first two to three months after treatment; however, these became progressively less apparent. Figure 1 shows the structure of the eyebank eye after electrocautery applications with different cautery units. The Bovie unit produced the depressions through Bowman's membrane and superficial stroma (Fig. 1,
Fig. 1 (Farris, Iwamoto, and DeVoe). Light micrographs of fresh human cornea from eye-bank eye after cautery of Bowman's membrane with Bovie (top) and M I R A (bottom) electrosurgical machines. The Bovie unit produced depressions through Bowman's membrane and superficial stroma (top, a r r o w ) . The high frequency electrodiathermy units of Cameron-Miller and M I R A did not produce breaks (bottom, arrow) (X148).
SSO
AMERICAN JOURNAL OF OPHTHALMOLOGY
top, a r r o w ) . The high-frequency electrodiathermy units of Cameron-Miller and M I R A did not produce breaks through Bowman's membrane (Fig. 1, bottom, a r r o w ) . Light and electron microscopy of the corneal buttons removed at keratoplasy from two patients who had previously undergone cautery of Bowman's membrane revealed that in both corneas, an extensive subepithelial connective tissue of varying thickness was formed between the epithelium and the Bow man's membrane, over almost the entire cor neal regions studied (Figs. 2 and 3 ) . P r o b ably due to the effect of cautery, the Bow man's membrane (or layer) was often dis rupted, and its gaps were filled with an ex tension of stromal connective tissue, which was further continuous anteriorly with the subepithelial connective tissue (Figs. 2, and 3, t o p ) .
APRIL, 1974
Of 100 eyes treated with cautery of Bow man's membrane, 75 had complete relief of pain with one treatment and eight had com plete relief of pain when another treatment was done for a few remaining bullae. Fifteen eyes had marked relief of pain with one treatment but continued to complain of slight discomfort manifested as tearing or mild foreign body sensation. There were two complications—a per forated cornea, noted at the end of the pro cedure when the last few applications were made centrally, and a descemetocele forming in the postoperative course. Both of these eyes had severe glaucoma, and one patient had refused to have enucleation. Eighteen of the 100 eyes studied had glau coma and elevation of intraocular pressure prior to cautery of Bowman's membrane. Of the eyes with bullous keratopathy and glau coma, nine had complete relief of pain with one treatment, and two eyes had a similar result after the treatment was repeated. Five eyes continued to have slight discomfort after one treatment and the two complications of perforation and descemetocele formation were in this group of eyes with glaucoma and elevated intraocular pressure.
The newly formed subepithelial connective tissue was composed of many active fibroblasts and collagen fibrils of various diame ters, ranging from 10 to 40 nm (Figs. 2, and 3, bottom). While the fibrils with approxi mately 30 nm in diameter, slightly larger than those of normal corneal stroma (20 to 25 nm in diameter), predominated, there was also a considerable number of thin fibrils (approxi DISCUSSION mately 10 nm in diameter) (Fig. 3, bottom). T h e interfibrillar spaces were usually wider Various treatments have been suggested than those in the stroma, and contained fine for relieving the pain associated with bul filamentous elements (Fig. 3, bottom). This lous keratopathy. A conjunctival flap as pro was typically observed in one case in which posed by Gundersen was probably one of the the corneal epithelium appeared normal (non- earliest forms of therapy. 3 Scarification uti edematous) over the wide central regions lizing trichloroacetic acid has also been rec 1 studied, indicating a successful result of cau ommended. More recently, replacement of tery procedure in these areas. Histochemical the epithelium with a glued-on hard contact staining of the other half specimen showed lens offered the possibility of improved vi 7 that the corresponding subepithelial connec sion as well as relief of pain/'" However, tive tissue was stained more intensively than epithelium eventually grew under these the stroma with P A S (Fig. 3, middle) and lenses, which then came off. In some cases alcian blue, although toluidine blue demon osmotic agents can provide improvements in strated no clear metachromasia. These sug vision as well as relief from pain, and in gested a considerable amount of mucopoly- ■cases of moderately elevated intraocular pres saccharides present within the widened inter sure, antiglaucoma agents lower the intra fibrillar spaces of the subepithelial connective ocular pressure sufficiently to improve vision. However, a number of patients have such tissue.
XS'^.'.jft'
Fig. 2 (Farris, Iwamoto, and DeVoe). Electron micrographs of corneal buttons removed from two pa tients previously treated with cautery of Bowman's membrane showing subepithelial connective tissue ( S C T ) associated with superficial stroma through breaks (arrow) of Bowman's membrane ( B m ) . E indicates epithelium, and f, active fibroblasts with well-developed rough-surfaced endoplasmic reticulum (top, x3,000; bottom, x 10,000.)
552
AMERICAN JOURNAL OF OPHTHALMOLOGY
,:^ac.-r*T_;
APRIL, 1974
:'*««B!fe
Fig. 3 (Farris, Iwamoto, and DeVoe). Same corneas as in Figure 2, bottom; the patient had been treated with cautery of Bowman's membrane. Top, Light micrograph of Masson's trichrome-stained section. A thick subepithelial connective tissue ( S C T ) seems to arise from stroma ( S T ) through breaks of Bow man's membrane (arrows) (X148). Middle, Light micrograph of PAS-stained section. Subepithelial connective tissue ( S C T ) is stained more intensively than the stroma ( S T ) ( X l 4 8 ) . Bottom, Electron micrograph of subepithelial connective tissue, showing thick (c) and thin (t) collagen fibrils. InterfibriUar spaces are relatively large, and often contain fine filamentous elements (arrows) (X37,000).
VOL. 77, NO. 4
CAUTERY OF BOWMAN'S MEMBRANE
severe stromal changes that vision is not im proved even though use of these agents pre vents the formation of bullae. In these cases, the primary consideration is relief of pain and overcoming the inflammation associated with rupturing of the epithelial bullae. Pene trating keratoplasty may not be indicated in some of these cases because of previous nerve damage due to glaucoma, macular de generation, or good vision in the opposite eye. In some such severely damaged, painful eyes, the patient may refuse enucleation. Cautery of Bowman's membrane provides a simple, direct method of eliminating the painful epithelial bullae and can improve the condition of the cornea for later penetrating keratoplasty when it is indicated. Also, cos metic scleral shells can be used once the cornea is well healed and no longer painful. The superficial scarring or subepithelial connective tissue produced by cautery of Bowman's membrane provides a barrier to the passage of fluid beneath the epithelium. The histologic section revealed perforation of stromal connective tissue through the breaks in Bowman's membrane with spread ing of connective tissue over the broken seg ments of the Bowman's membrane. Of some interest is the fact that the interfibrillar space in the newly formed connective tissue is ac tually greater than that seen in the normal corneal stroma. Thus, the increased resistance of fluid flow in the tissue must be explained on the basis of changes in the ground sub stance, which are also indicated by the modi fied staining pattern of this layer seen in pathologic specimens after cautery of Bow man's membrane. The spark-gap generated current of the Bovie electrocautery unit produced breaks through Bowman's membrane in the fresh eye-bank eye only. Although the constant, crystal-controlled high-frequency currents are preferred for diathermy applications in retinal detachment surgery,8 the increased tissue destructiveness of the lower, mixed frequencies of the monoterminal spark-gap generated current was necessary to produce
553
breaks in Bowman's membrane and superfi cial stromal destruction. Previous clinical studies have also confirmed this inadequate tissue destruction with higher frequency electrodiathermy machines. Ninety-eight percent of the patients bene fited from cautery of Bowman's membrane in terms of pain relief. There were complica tions in two patients ( 2 % ) . Repeat treat ments seemed necessary only when the cau tery applications were too widely spaced or covered an inadequate area. Localized cau tery of epithelial blister formation necessi tated extension of the treatment a millimeter beyond the area of epithelial edema. The two complications occurred in eyes that were probably too edematous for this type of treatment. Both had severe glaucoma and the corneas were considered quite edematous, even "mushy" or waterlogged. As a result, excessive deep stromal destruction took place rather than being confined to Bowman's membrane and superficial stroma as occurs in the usual cases of bullous keratopathy with mild to moderate edema of the corneal stroma. Glaucomatous eyes appeared to respond less favorably to cautery of Bowman's mem brane compared to normotensive eyes. A smaller proportion of these eyes had com plete relief of pain with one treatment, and the two complications occurred in this group. Better control of the intraocular pressure prior to cautery of Bowman's membrane would no doubt decrease stromal edema and limit the extent of tissue necrosis to the superficial layers. Reepithelialization occurred slowly after cautery of Bowman's membrane, sometimes requiring as long as six weeks. Patching en couraged complete covering by epithelium. Collagenase inhibitors may prevent ulceration during this time but were not required in these cases. SUMMARY
One hundred eyes with painful bullous keratopathy treated with cautery of Bow-
554
AMERICAN JOURNAL OF OPHTHALMOLOGY
man's membrane had marked to complete re lief of pain in 98% of the group. There were two failures, which were also the two complications—perforated cornea and a descemetocele, both in edematous corneas of severely glaucomatous eyes. Light and elec tron microscopy demonstrated an extensive subepithelial connective tissue, probably formed by an extension of stromal con nective tissue through the breaks in Bow man's membrane, and suggested the ground substance in this new tissue to be responsible for increased resistance to edema fluid and prevention of subepithelial bullae. REFERENCES
1. Salleras, A.: Bullous keratopathy. In King, J. H., Jr., and McTigue, J. W. (eds.) : The Cornea. World Congress. Washington, Buttersworths, 1965, p. 292.
APRIL, 1974
2. DeVoe, A. G.: Electrocautery of Bowman's membrane. Trans. Am. Ophthalmol. Soc. 64:109, 1966. 3. Gundersen, T.: Conjunctival flaps in the treat ment of comeal disease with reference to a new technique of application. Arch. Ophthalmol. 60:880, 1958. 4. Gifford, S. R.: The mild form of epithelial dystrophy of the cornea. Arch. Ophthalmol. 7:18, 1932. 5. Gasset, A. R., and Kaufman, H. E.: Epikeratoprosthesis. Replacement of superficial cornea by methyl methacrylate. Am. I. Ophthalmol. 66:641, 1968. 6. Dohlman, C. H., Carroll, J. M., Ahmad, B., and Refoyo, M. F.: Replacement of the corneal epithelium with a contact lens. Trans. Am. Acad. Ophthalmol. Otolaryngol. 73:482, 1969. 7. Farris, R. L., and Willcockson, T. H.: Gluedon contact lenses. Clinical studies. In Polack, F. M. (ed.) : Corneal and External Diseases of the Eye. First Inter-American Symposium. Springfield, 111., Charles C Thomas, 1970, p. 207. 8. Pomerantzeff, O.: Photocoagulators and sur gical diathermy. Am. J. Med. Electronics 3:237, 1964.