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Radial keratotomy in a patient with keratoconus
techniques and case reports Radial keratotomy in a patient with keratoconus William Ellis, M.D. ABSTRACT A 30-year-old white male with keratoconus had uneventful radial keratotomy in his right eye. Although a. good initial response was obtained with total correction of myopia and astigmatism, by 18 months postoperatively the entire result had regressed and thepatient de~onsttated reformation of the cone and regression to high myopi~ Scarring occurred in the three· inferior cuts overlying the con.e•. Cuts ontbe horizontal axis, and superiorly.(above the cone), had a normal appearance with normal wound 4~aling. Because of the nature of the wound healing overlying the portion of the cornea affected by the keratoconus and because of the total regression of effect,radial keratotomy in patients with keratoconus does not appear to be an effective modality, Key Words: keratoconus, radial keratotomy
Keratoconus is a corneal thinning disorder without inflammation characterized by an apical thinning of the cornea, usually inferiorly, with the protrusion of a steep cone. Cone size may vary, as may its location, though it is usually inferior. As keratoconus progresses it is characterized by the development of high myopia and irregular astigmatism associated with the conical deformation. Contact lens correction becomes difficult and spectacle lens correction is usually impossible because of the irregular astigmatism and anisometropia created by the disorder. 1 This report details an attempt to obtain binocular vision by reducing anisometropia and astigmatism in the eye with the more pronounced cone. The patient could no longer tolerate contact lenses and was unhappy with his visual situation. An uneventful eightcut radial keratotomy was performed with good depth and there were no complications at the time of surgery. Transverse astigmatic incisions were also placed; these reduced the toricity and resulted in a spherical flattened cornea postoperatively. However, over an IB-month postoperative period, the
cone reformed and resultant corneal curvatures over its apex were greater than prior to surgery. CASE REPORT A 30-year-old male presented complaining of difficulty wearing a contact lens in the right eye. Refraction in the eye was -9.25 +3.00 X 160 with a best corrected visual acuity of 20/40. Refraction in the left eye was -4.75 + 1.50 X 30 with a best corrected visual acuity of 20/30. Keratometry in the right eye showed the mires were slightly distorted. Readings were 46.25 X 50 by 4B.00 X 160. In the left eye keratometry readings were 44.25 X 110 by 45.75 X 20. Best corrected visual acuity could not be improved with refraction. The patient found his contact lenses uncomfortable. He had difficulty keeping them in place, especially in the right eye, and desired to return to glasses. Corneoscopic photographs of both eyes revealed inferior steepening bilaterally with the presence of moderate keratoconus, worse in the right eye than
Repril1.t requests to William Ellis, M.D., Eye Center of Northern California, 6500 Fairmount Avenue, Suite 2, El Cerrito, California 94530. 406
J CATARACT REFRACT SURG-VOL 18, JULY 1992
Table 1. Preoperative topogometric measurements in the right eye. Location
Table 2. Topogometric measurements in the right eye 18 months following astigmatic radial keratotomy.
Measurement
Location
Measurement
Superior temporal
40.75 D
Superior temporal
35.50 D
Superior
38.50 D
Superior
36.00 D
Superior nasal
38.25 D
Temporal Central
43.00 D 46.25 D X 90 by 48.00 D X 180
40.50 D
Superior nasal Temporal Central
50.00 D 50.00 D X 90 by 52.00 D X 180
Nasal
40.50 D
Nasal
38.50 D
Inferior temporal
46.00 D
Inferior temporal
48.00 D
Inferior
50.75 D
Inferior
60.00 D
Inferior nasal
60.00 D
45.25 D Inferior nasal Keratometric measurements taken along radial meridians. Central readings taken over visual axis. Peripheral readings 20 degrees (4 mm) from visual axis.
in the left. Mapping of the corneal curvatures with a topogometerconfirmed the diagnosis (Table 1). Various therapeutic options were considered including corneal transplantation, epikeratophakia, or refitting a new contact lens to the right eye, which the patient did not desire. After being informed of potential risks and complications, he decided to have radial keratotomy only on the right eye in an effort to reduce the anisometropia and correct the astigmatism. An eight-cut radial keratotomy was performed with a 2.75 mm optical zone at 500 Jlm. Midperipheral redeepening to 560 Jlm was performed in all eight incisions. Two transverse astigmatic incisions were made perpendicular to the 160 degree axis at an optical zone of 5.5 mm and 6.5 mm, respectively. Both transverse incisions were made above the horizontal axis to avoid the area of the cone inferiorly. The patient was maintained on gentamicin ophthalmic drops four times a day and 1 % prednisolone acetate four times a day for three weeks. Two weeks after surgery, the refraction in the right eye was +4.25 +0.25 X 55 with best corrected visual acuity of 20/80+ 2 . Two months following surgery, refraction was +2.25 +0.25 X 130 with best corrected visual acuity of 20/60- 1 . Central keratometry showed readings of 37.87 X 10 by 37.75 X 110. The cornea did not demonstrate hydrops during the postoperative observation period nor when seen later. Eighteen months following the initial surgery the patient returned complaining that his visual acuity had decreased in the right eye. The refraction was -4.75 + 1. 75 X 170 in the right eye and best corrected visual acuity was counting fingers. Visual
Keratometric measurements taken along radial meridians. Central readings taken over visual axis. Peripheral readings 20 degrees (4 mm) from visual axis.
acuity could not be improved with refraction. In the left eye, refraction was -6.00 +2.75 X 10 and visual acuity was 20/20. Central keratometry was performed in the right eye with a reading of 51.75 X 15 by 52.50 X 105. Corneal mapping was done using a topogometer (Table 2). Superiorly, 4 mm above the optical zone, corneal curvature decreased to 37 diopters (D) and inferiorly, 4 mm below the optical zone, the curvature of the cone apex increased to greater than 60 D. Photokeratoscopy demonstrated a well-developed keratoconus inferiorly in the right eye. Slitlamp examination of the cornea showed the radial incisions on or above the horizontal axis had healed normally. However, the three radial incisions located inferiorly over the apex of the cone showed severe scarring and distortion (Figures 1 and 2). The remaining examination findings were within normal limits except for mild to moderate cortical lens changes of equal extent bilaterally. DISCUSSION Keratoconus may be characterized clinically by many findings including Fleischer's ring, an iron ring of ferritin deposited in the epithelial layer encircling the base of the cone. Vogt's stria which represent vertical folds in Descemet's membrane paralleling the steep axis of the cone may also occur. In addition, small dislocations in Bowman's membrane occur frequently and are associated with delicate, subepithelial, anterior stromal scars thought to be caused by repair of these dislocations. The earliest clinical diagnosis may be made with the streak retinoscope and later with the corneoscope. 2 Characteristically there is a steepening of the cor-
J CATARACT REFRACT SURG-VOL 18, JULY 1992
407
Fig. 1.
(Ellis) Slitlamp photograph of the superior cornea in the right eye 18 months postoperatively. Note the normal appearance of the healed keratotomy incisions superiorly.
neal rings inferiorly over the apex of the cone. Most patients with keratoconus present under the age of 20. In the early stages of keratoconus, classic slitlamp findings may not yet be present. One should, therefore, be suspicious oflatent keratoconus in any young patient with progressive myopia, especially with keratometry readings above 48 D or with progressive myopic astigmatism. The earliest clinical finding may be a scissors reflex with streak retinoscopy. The earliest keratoscopic finding is the classic "egg-shaped" appearance of the central mire related to inferotemporal steepening. With progression of the disease the more peripheral corneoscope mires are affected and other quadrants of the cornea also change. The progression of the disorder may be variable and may not be symmetrical. Histologically the earliest changes appear to be a fibrillar degeneration in Bowman's membrane, followed by breaks and dislocations. 3 The characteristic corneal scarring seems to be an effort to repair these breaks with connective tissue formation secondary to fibroblastic activation of the keratocytes. 4 These activated keratocytes and epithelial cells characteristically project into the dislocations in Bowman's membrane. s Keratocytes in unaffected areas of the cornea appear normal. The disease process seems to be caused by a decrease in the number of corneal lamellae. The remaining corneal lamellae are of normal thickness. 6 408
Fig. 2.
(Ellis) Slitlamp photograph of the inferior cornea of the right eye 18 months postoperatively. Note the cicatricial formations in the keratotomy incisions inferiorly over the apex of the cone.
Surgical intervention in keratoconus is indicated when the patient no longer achieves good visual acuity from correction with either spectacles or contact lenses. As the corneal thinning progresses, tears may develop in Descemet's membrane with subsequent disruption of the corneal endothelial barrier leading to stromal edema and acute corneal decompensation. Terrien 7 observed that resolution of this edema often occurs spontaneously over several months, leaving a residual scar. Often the process is accompanied by flattening of the cone and improvement in visual acuity, especially if the scarring occurs away from the visual axis. In 1939 Sat0 8 •9 first attempted to induce acute hydrops to treat keratoconus by placing surgical incisions in Descemet's membrane over the apex of the cone. Many of these cones flattened spontaneously following resolution of the hydrops. A subsequent diminution of myopia and astigmatism was also noted. Using these observations of keratoconus, Sato developed his posterior keratotomy incision for myopia. 10 - 12 However, subsequent study demonstrated that irreversible damage caused by surgical incision of the endothelial layers led to a high complication rate using this procedure. 13 Radial keratotomy for keratoconus has not been attempted because of its poor record, as evidenced by the results in Sato's cases. In addition, penetrating keratoplasty has been highly successful in most series of cases. Over 80% of patients having pene-
J CATARACT REFRACT SURG-VOL IS, JULY 1992
trating keratoplasty for keratoconus obtain a visual acuity of 20/40 or better. 14 - 16 In my patient I attempted to delay corneal transplantation by correcting the visually disturbing anisometropia and astigmatism with anterior radial keratotomy incisions. I hoped that anterior incisions would not be associated with the debilitating side effects originally described by Sato who performed the procedure posteriorly. This, however, was not the case. Cicatricial formation in the three inferior incisions located over the apex of the cone occurred. These thickened scars may represent an abnormal healing response caused iatrogenically by the induced breaks in Bowman's membrane created by the surgery. The most interesting clinical observation is that the incisions away from the cone, the incisions in the horizontal meridian and above, healed relatively normally without prolific cicatricial formation (Figure 1). Initially the radial keratotomy produced a beneficial result with flattening of the cone and reduction of the astigmatism. In fact, in the early postoperative period there was a fairly large overcorrection. However, the result rapidly dissipated over a period of 18 months and the cone reformed accompanied by the production of a high amount of irregular astigmatism and resultant myopia. In retrospect it is not surprising that regression of effect of the radial keratotomy occurred since by definition keratoconus is a progressive thinning of the cornea and does not resolve with time. Five years ago I reported that cases of radial keratotomy characterized by prolific cicatricial formation had the largest amount of regression of effect. 1 7 This observation, which I subsequently confirmed clinically ("Reopening RK Incisions Modifies Overcorrections, Astigmatism," Ophthalmology Times, July 15, 1991,26-27) may be useful in reducing overcorrection in radial keratotomy by reopening keratotomy incisions and resuturing them to encourage cicatricial formation. Since it appears that pathologic alterations in corneas with keratoconus encourage cicatricial formation in the area of the incisions, using radial keratotomy to delay penetrating keratoplasty in cases of keratoconus does not appear to be an effective modality of treatment. Indeed, the short time in which the regression of effect progressed in the case reported indicates the instability of the resultant correction. It also should be emphasized that performing radial keratotomy in an eye with keratoconus may cause difficulty in performing a corneal transplant in an unstable, irregular recipient bed with the resultant increased astigmatism and the potential for problems with wound healing. The results of the treatment of keratoconus by
modern anterior radial keratotomy have not been well documented in the literature. The recurrence of keratoconus, and in particular the extensive scarring of the incisions located in the area of corneal thinning, is of interest. The findings in this case show scarring only over the cone itself. As the slitlamp photographs demonstrate, the incisions were relatively normal in the horizontal meridian and above. However, inferiorly extensive scarring and cicatricial formation resulted. It remains for future research to elucidate the mechanism of the cicatricial formation. REFERENCES 1. Bron AJ, Lobascher DJ, Dixon WS, et al. Fibrillary lines of the cornea. A clinical sign in keratoconus. Br J Ophthalmol 1975; 59:136-140 2. Rowsey Reynolds AE, Brown R. Corneal topography; corneascope. Arch Ophthalmol 1981; 99:10931100 3. McTigue JW. The human cornea: a light and electron microscopic study of the normal cornea and its alterations in various dystrophies. Trans Am Ophthalmol Soc 1967; 65:591-660 4. Pouliquen Y, Graf B, Hamada R, et al. Les fibrocytes dans Ie keratocone. Aspect morph~logique et modifications de I' espace extracellulaire. Etude en microscopie optique et electronique. Arch Ophtalmol (Paris) 1972; 32:571-586 5. Mcpherson SD Jr, Kiffney GT Jr. Some histologic findings in keratoconus. Arch Ophthalmol 1968; 79:669673 6. Jakus MA. Further observations on the fine structure of the cornea. Invest Ophthalmol 1962; 1: 202-225 7. Terrien F. Ectasie transitoire au cours du keratocone. Arch Ophtalmol (Paris) 1906; 26:9-12 8. Sato T. Treatment of the conical corneal incision of Descemet's membrane. Acta Soc Ophthalmol Japan 1939; 43: 541-548 9. Sato T. Posterior half-incision of cornea for astigmatism. Operative procedures and results of the improved tangent method. Am J Ophthalmol 1953; 36: 462-466 10. Sato T, Akiyama K, Shibata H. A new surgical approach to myopia. Am J Ophthalmol 1953; 36:823-829 11. Akiyama K. The surgical treatment of myopia. III report: anterior and posterior incisions. Acta Soc Ophthalmol Japan 1955; 59:797-835 12. Akiyama K. Study of the surgical treatment for myopia. Animal experiment. Acta Soc Ophthalmol Japan 1955; 59:294-312 13. Akiyama K, Tanaka M, Kanai A, Nakajima A. Problems arising from Sato's radial keratotomy procedure in Japan. CLAO J 1984; 10:179 14. Payne JW. Primary penetrating keratoplasty for keratoconus: along-term follow-up. Cornea 1982; 1:21-27 15. Arentsen Morgan B, Green WR. Changing indications for keratoplasty. Am J Ophthalmol 1976; 81: 313-318 16. Paton RT. Corneal transplantation; a review of 365 operations. Arch Ophthalmol1954; 52:871-916 17. Ellis W. A Textbook of Radial Keratotomy and Astigmatism Surgery, 2nd ed. Irvine, CA, Keith C Terry & Assoc, 1986; 126
n,
n,
J CATARACT REFRACT SURG-VOL 18, JULY 1992
409
Keratoconus is a corneal thinning disorder without inflammation characterized by an apical thinning of the cornea, usually inferiorly, with the protrusion of a steep cone. Cone size may vary, as may its location, though it is usually inferior. As keratoconus progresses it is characterized by the development of high myopia and irregular astigmatism associated with the conical deformation. Contact lens correction becomes difficult and spectacle lens correction is usually impossible because of the irregular astigmatism and anisometropia created by the disorder. 1 This report details an attempt to obtain binocular vision by reducing anisometropia and astigmatism in the eye with the more pronounced cone. The patient could no longer tolerate contact lenses and was unhappy with his visual situation. An uneventful eightcut radial keratotomy was performed with good depth and there were no complications at the time of surgery. Transverse astigmatic incisions were also placed; these reduced the toricity and resulted in a spherical flattened cornea postoperatively. However, over an IB-month postoperative period, the
cone reformed and resultant corneal curvatures over its apex were greater than prior to surgery. CASE REPORT A 30-year-old male presented complaining of difficulty wearing a contact lens in the right eye. Refraction in the eye was -9.25 +3.00 X 160 with a best corrected visual acuity of 20/40. Refraction in the left eye was -4.75 + 1.50 X 30 with a best corrected visual acuity of 20/30. Keratometry in the right eye showed the mires were slightly distorted. Readings were 46.25 X 50 by 4B.00 X 160. In the left eye keratometry readings were 44.25 X 110 by 45.75 X 20. Best corrected visual acuity could not be improved with refraction. The patient found his contact lenses uncomfortable. He had difficulty keeping them in place, especially in the right eye, and desired to return to glasses. Corneoscopic photographs of both eyes revealed inferior steepening bilaterally with the presence of moderate keratoconus, worse in the right eye than
Repril1.t requests to William Ellis, M.D., Eye Center of Northern California, 6500 Fairmount Avenue, Suite 2, El Cerrito, California 94530. 406
J CATARACT REFRACT SURG-VOL 18, JULY 1992
Table 1. Preoperative topogometric measurements in the right eye. Location
Table 2. Topogometric measurements in the right eye 18 months following astigmatic radial keratotomy.
Measurement
Location
Measurement
Superior temporal
40.75 D
Superior temporal
35.50 D
Superior
38.50 D
Superior
36.00 D
Superior nasal
38.25 D
Temporal Central
43.00 D 46.25 D X 90 by 48.00 D X 180
40.50 D
Superior nasal Temporal Central
50.00 D 50.00 D X 90 by 52.00 D X 180
Nasal
40.50 D
Nasal
38.50 D
Inferior temporal
46.00 D
Inferior temporal
48.00 D
Inferior
50.75 D
Inferior
60.00 D
Inferior nasal
60.00 D
45.25 D Inferior nasal Keratometric measurements taken along radial meridians. Central readings taken over visual axis. Peripheral readings 20 degrees (4 mm) from visual axis.
in the left. Mapping of the corneal curvatures with a topogometerconfirmed the diagnosis (Table 1). Various therapeutic options were considered including corneal transplantation, epikeratophakia, or refitting a new contact lens to the right eye, which the patient did not desire. After being informed of potential risks and complications, he decided to have radial keratotomy only on the right eye in an effort to reduce the anisometropia and correct the astigmatism. An eight-cut radial keratotomy was performed with a 2.75 mm optical zone at 500 Jlm. Midperipheral redeepening to 560 Jlm was performed in all eight incisions. Two transverse astigmatic incisions were made perpendicular to the 160 degree axis at an optical zone of 5.5 mm and 6.5 mm, respectively. Both transverse incisions were made above the horizontal axis to avoid the area of the cone inferiorly. The patient was maintained on gentamicin ophthalmic drops four times a day and 1 % prednisolone acetate four times a day for three weeks. Two weeks after surgery, the refraction in the right eye was +4.25 +0.25 X 55 with best corrected visual acuity of 20/80+ 2 . Two months following surgery, refraction was +2.25 +0.25 X 130 with best corrected visual acuity of 20/60- 1 . Central keratometry showed readings of 37.87 X 10 by 37.75 X 110. The cornea did not demonstrate hydrops during the postoperative observation period nor when seen later. Eighteen months following the initial surgery the patient returned complaining that his visual acuity had decreased in the right eye. The refraction was -4.75 + 1. 75 X 170 in the right eye and best corrected visual acuity was counting fingers. Visual
Keratometric measurements taken along radial meridians. Central readings taken over visual axis. Peripheral readings 20 degrees (4 mm) from visual axis.
acuity could not be improved with refraction. In the left eye, refraction was -6.00 +2.75 X 10 and visual acuity was 20/20. Central keratometry was performed in the right eye with a reading of 51.75 X 15 by 52.50 X 105. Corneal mapping was done using a topogometer (Table 2). Superiorly, 4 mm above the optical zone, corneal curvature decreased to 37 diopters (D) and inferiorly, 4 mm below the optical zone, the curvature of the cone apex increased to greater than 60 D. Photokeratoscopy demonstrated a well-developed keratoconus inferiorly in the right eye. Slitlamp examination of the cornea showed the radial incisions on or above the horizontal axis had healed normally. However, the three radial incisions located inferiorly over the apex of the cone showed severe scarring and distortion (Figures 1 and 2). The remaining examination findings were within normal limits except for mild to moderate cortical lens changes of equal extent bilaterally. DISCUSSION Keratoconus may be characterized clinically by many findings including Fleischer's ring, an iron ring of ferritin deposited in the epithelial layer encircling the base of the cone. Vogt's stria which represent vertical folds in Descemet's membrane paralleling the steep axis of the cone may also occur. In addition, small dislocations in Bowman's membrane occur frequently and are associated with delicate, subepithelial, anterior stromal scars thought to be caused by repair of these dislocations. The earliest clinical diagnosis may be made with the streak retinoscope and later with the corneoscope. 2 Characteristically there is a steepening of the cor-
J CATARACT REFRACT SURG-VOL 18, JULY 1992
407
Fig. 1.
(Ellis) Slitlamp photograph of the superior cornea in the right eye 18 months postoperatively. Note the normal appearance of the healed keratotomy incisions superiorly.
neal rings inferiorly over the apex of the cone. Most patients with keratoconus present under the age of 20. In the early stages of keratoconus, classic slitlamp findings may not yet be present. One should, therefore, be suspicious oflatent keratoconus in any young patient with progressive myopia, especially with keratometry readings above 48 D or with progressive myopic astigmatism. The earliest clinical finding may be a scissors reflex with streak retinoscopy. The earliest keratoscopic finding is the classic "egg-shaped" appearance of the central mire related to inferotemporal steepening. With progression of the disease the more peripheral corneoscope mires are affected and other quadrants of the cornea also change. The progression of the disorder may be variable and may not be symmetrical. Histologically the earliest changes appear to be a fibrillar degeneration in Bowman's membrane, followed by breaks and dislocations. 3 The characteristic corneal scarring seems to be an effort to repair these breaks with connective tissue formation secondary to fibroblastic activation of the keratocytes. 4 These activated keratocytes and epithelial cells characteristically project into the dislocations in Bowman's membrane. s Keratocytes in unaffected areas of the cornea appear normal. The disease process seems to be caused by a decrease in the number of corneal lamellae. The remaining corneal lamellae are of normal thickness. 6 408
Fig. 2.
(Ellis) Slitlamp photograph of the inferior cornea of the right eye 18 months postoperatively. Note the cicatricial formations in the keratotomy incisions inferiorly over the apex of the cone.
Surgical intervention in keratoconus is indicated when the patient no longer achieves good visual acuity from correction with either spectacles or contact lenses. As the corneal thinning progresses, tears may develop in Descemet's membrane with subsequent disruption of the corneal endothelial barrier leading to stromal edema and acute corneal decompensation. Terrien 7 observed that resolution of this edema often occurs spontaneously over several months, leaving a residual scar. Often the process is accompanied by flattening of the cone and improvement in visual acuity, especially if the scarring occurs away from the visual axis. In 1939 Sat0 8 •9 first attempted to induce acute hydrops to treat keratoconus by placing surgical incisions in Descemet's membrane over the apex of the cone. Many of these cones flattened spontaneously following resolution of the hydrops. A subsequent diminution of myopia and astigmatism was also noted. Using these observations of keratoconus, Sato developed his posterior keratotomy incision for myopia. 10 - 12 However, subsequent study demonstrated that irreversible damage caused by surgical incision of the endothelial layers led to a high complication rate using this procedure. 13 Radial keratotomy for keratoconus has not been attempted because of its poor record, as evidenced by the results in Sato's cases. In addition, penetrating keratoplasty has been highly successful in most series of cases. Over 80% of patients having pene-
J CATARACT REFRACT SURG-VOL IS, JULY 1992
trating keratoplasty for keratoconus obtain a visual acuity of 20/40 or better. 14 - 16 In my patient I attempted to delay corneal transplantation by correcting the visually disturbing anisometropia and astigmatism with anterior radial keratotomy incisions. I hoped that anterior incisions would not be associated with the debilitating side effects originally described by Sato who performed the procedure posteriorly. This, however, was not the case. Cicatricial formation in the three inferior incisions located over the apex of the cone occurred. These thickened scars may represent an abnormal healing response caused iatrogenically by the induced breaks in Bowman's membrane created by the surgery. The most interesting clinical observation is that the incisions away from the cone, the incisions in the horizontal meridian and above, healed relatively normally without prolific cicatricial formation (Figure 1). Initially the radial keratotomy produced a beneficial result with flattening of the cone and reduction of the astigmatism. In fact, in the early postoperative period there was a fairly large overcorrection. However, the result rapidly dissipated over a period of 18 months and the cone reformed accompanied by the production of a high amount of irregular astigmatism and resultant myopia. In retrospect it is not surprising that regression of effect of the radial keratotomy occurred since by definition keratoconus is a progressive thinning of the cornea and does not resolve with time. Five years ago I reported that cases of radial keratotomy characterized by prolific cicatricial formation had the largest amount of regression of effect. 1 7 This observation, which I subsequently confirmed clinically ("Reopening RK Incisions Modifies Overcorrections, Astigmatism," Ophthalmology Times, July 15, 1991,26-27) may be useful in reducing overcorrection in radial keratotomy by reopening keratotomy incisions and resuturing them to encourage cicatricial formation. Since it appears that pathologic alterations in corneas with keratoconus encourage cicatricial formation in the area of the incisions, using radial keratotomy to delay penetrating keratoplasty in cases of keratoconus does not appear to be an effective modality of treatment. Indeed, the short time in which the regression of effect progressed in the case reported indicates the instability of the resultant correction. It also should be emphasized that performing radial keratotomy in an eye with keratoconus may cause difficulty in performing a corneal transplant in an unstable, irregular recipient bed with the resultant increased astigmatism and the potential for problems with wound healing. The results of the treatment of keratoconus by
modern anterior radial keratotomy have not been well documented in the literature. The recurrence of keratoconus, and in particular the extensive scarring of the incisions located in the area of corneal thinning, is of interest. The findings in this case show scarring only over the cone itself. As the slitlamp photographs demonstrate, the incisions were relatively normal in the horizontal meridian and above. However, inferiorly extensive scarring and cicatricial formation resulted. It remains for future research to elucidate the mechanism of the cicatricial formation. REFERENCES 1. Bron AJ, Lobascher DJ, Dixon WS, et al. Fibrillary lines of the cornea. A clinical sign in keratoconus. Br J Ophthalmol 1975; 59:136-140 2. Rowsey Reynolds AE, Brown R. Corneal topography; corneascope. Arch Ophthalmol 1981; 99:10931100 3. McTigue JW. The human cornea: a light and electron microscopic study of the normal cornea and its alterations in various dystrophies. Trans Am Ophthalmol Soc 1967; 65:591-660 4. Pouliquen Y, Graf B, Hamada R, et al. Les fibrocytes dans Ie keratocone. Aspect morph~logique et modifications de I' espace extracellulaire. Etude en microscopie optique et electronique. Arch Ophtalmol (Paris) 1972; 32:571-586 5. Mcpherson SD Jr, Kiffney GT Jr. Some histologic findings in keratoconus. Arch Ophthalmol 1968; 79:669673 6. Jakus MA. Further observations on the fine structure of the cornea. Invest Ophthalmol 1962; 1: 202-225 7. Terrien F. Ectasie transitoire au cours du keratocone. Arch Ophtalmol (Paris) 1906; 26:9-12 8. Sato T. Treatment of the conical corneal incision of Descemet's membrane. Acta Soc Ophthalmol Japan 1939; 43: 541-548 9. Sato T. Posterior half-incision of cornea for astigmatism. Operative procedures and results of the improved tangent method. Am J Ophthalmol 1953; 36: 462-466 10. Sato T, Akiyama K, Shibata H. A new surgical approach to myopia. Am J Ophthalmol 1953; 36:823-829 11. Akiyama K. The surgical treatment of myopia. III report: anterior and posterior incisions. Acta Soc Ophthalmol Japan 1955; 59:797-835 12. Akiyama K. Study of the surgical treatment for myopia. Animal experiment. Acta Soc Ophthalmol Japan 1955; 59:294-312 13. Akiyama K, Tanaka M, Kanai A, Nakajima A. Problems arising from Sato's radial keratotomy procedure in Japan. CLAO J 1984; 10:179 14. Payne JW. Primary penetrating keratoplasty for keratoconus: along-term follow-up. Cornea 1982; 1:21-27 15. Arentsen Morgan B, Green WR. Changing indications for keratoplasty. Am J Ophthalmol 1976; 81: 313-318 16. Paton RT. Corneal transplantation; a review of 365 operations. Arch Ophthalmol1954; 52:871-916 17. Ellis W. A Textbook of Radial Keratotomy and Astigmatism Surgery, 2nd ed. Irvine, CA, Keith C Terry & Assoc, 1986; 126
n,
n,
J CATARACT REFRACT SURG-VOL 18, JULY 1992
409