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Limbal- vs Fornix-Based Conjunctival Trabeculectomy Flaps: Reply
100
January, 1988
AMERICAN JOURNAL OF OPHTHALMOLOGY
no further visual loss or optic disk change.
References 1. Posner, A., and Schlossman, A.: Syndrome of unilateral recurrent attacks of glaucoma with cyclitic symptoms. Arch. Ophthalmol. 39:517, 1948. 2. Kass, M. A., Becker, B., and Kolker, A. E.: Glaucomatocyclitic crisis and primary open-angle glaucoma. Am. J. Ophthalmol. 75:668, 1973. 3. Nagataki, S., and Mishima, S.: Aqueous humor dynamics in glaucomatocyclitic crisis. Invest. Oph thalmol. Vis. Sci. 15:365, 1976.
Correspondence Correspondence concerning recent articles or other mate rial published in THE JOURNAL should be submitted within six weeks of publication. Correspondence must be typed double-spaced, on 8V2 x 11-inch bond paper with lVi-inch margins on all four sides and should be no more than two typewritten pages in length. Every effort will be made to resolve controversies between the correspondents and the authors of the article before publication.
conjunctival flap as compared to a deeper chamber with the limbal-based flap, although both were comparable after the first week. The progressive shallowing of the anterior chamber is related to their technique in which the limbal end of the two radial incisions of the lamellar scleral flap were left unsutured. This allows the aqueous humor to drain through the radial incision at the corneoscleral limbus; spread along the front edge of the conjunctival flap, which is tightly opposed to the sclera; and leak out at the edges of the conjunctival flap through the absorbable su ture site. If the conjunctival flap is not snugly opposed to the sclera, then the aqueous humor may drain freely through the front edge of the conjunctival flap. This would cause an even higher incidence of shallow anterior chamber or even flat anterior cham ber than the authors described. When a fornix-based flap is used, the presence of a shallow anterior chamber during the week after surgery can be almost totally eliminated by suturing the limbal edge of the two radial incisions. I have found it easier to oppose directly the conjunctival flap and prevent leakage at the site of the conjunctival suture when 10-0 nylon sutures rather than absorbable sutures are used. MAURICE H. LUNTZ, M.D.
New York, New York
Limbal- vs Fornix-Based Conjunctival Trabeculectomy Flaps
Reply EDITOR:
EDITOR:
In the article "Limbal- vs fornix-based con junctival trabeculectomy flaps," by Carlo E. Traverso, Karim F. Tomey, and Sobhi Antonios (Am. J. Ophthalmol. 104:28, July 1987), the authors concentrate on the length of the surgical procedure and the overall results. They concluded that there is little difference in the results of the two procedures or the time taken to perform the surgical proce dures. I wish to comment on some aspects of trabeculectomy when using a conjunctivoTenon's flap, which I belive add to the safety of the operation. The authors report progressive shallowing of the anterior chamber with the fornix-based
Dr. Luntz's observations are most appropri ate and should be taken into consideration before switching from limbal-based to fornixbased conjunctival flaps for trabeculectomy. Indeed, additional sutures at the radial inci sions of the lamellar scleral flap help reduce postoperative hypotony. We usually tie our sutures only at the corners of the scleral flap to obtain some drainage of the aqueous humor. Should the scleral flap be left too loose, profound postoperative hypotony and a shallow or flat anterior chamber will be like ly to occur, regardless of whether the con junctival flap is limbal or fornix-based. As ap propriately pointed out by Dr. Luntz, postoperative hypotony and a shallow or flat
Vol. 105, No. 1
Correspondence
anterior chamber may be particularly evident when fornix-based conjunctival flaps are used, especially if the flap is sutured too loosely. Regarding the use of nylon vs absorbable sutures, we have been pleased with the latter, probably because we have them available mounted on tapered needles. Certainly, 10-0 nylon can be a good alternative. CARLO E. TRAVERSO, M.D. KARIM F. TOMEY, M.D. SOBHI R. ANTONIOS, M.D.
Riyadh, Saudi Arabia
Clinical Evaluation of the Oculab Tono-Pen EDITOR:
In the article "Clinical evaluation of the Oculab Tono-Pen," by D. S. Minckler, G. Baerveldt, D. Heuer, B. Quillen-Thomas, A. F. Walonker, and J. Weiner (Am. J. Ophthalmol. 104:168, August 1987), the authors conclude that the differences in intraocular pressure measured by this instrument are not "clinically troublesome." Of the 270 eyes studied, intraocular pressure in approximately 39% of the eyes measured outside an error range of ±3 mm Hg. Many of these eyes had high intraocular pressures. Because surgical decisions in glaucoma are influenced by intra ocular pressures, I believe that a qualification should be placed on the use of this instru ment in patients with glaucoma. Although the authors found no statistically significant dif ference in intraocular pressure that measured greater than 24 mm Hg (P = .30), the error in the measurement may be clinically significant for a glaucoma patient. The Tono-Pen may be a convenient and an accurate means for measuring intraocular pressure in uncooperative patients or in pa tients with irregularly shaped corneas. How ever, the impression that this instrument, with its "trivial differences" in measurement, can replace the Goldmann applanation to nometer in treating patients with high intra ocular pressure should not be given. EVE J. HIGGINBOTHAM, M.D.
Chicago, Illinois
101
Reply EDITOR:
We appreciate Dr. Higginbotham's concern regarding our statement that the "small un derestimation of intraocular pressure with the Tono-Pen in eyes with high intraocular pres sure . . . is not considered likely to be clini cally troublesome." That statement was based on our belief that a relatively small error (±3 mm Hg) in the majority of serial intraocular pressure measurements should not adversely affect therapy judgments in glaucoma pa tients. We do not believe that an error of this magnitude is clinically problematic because in the same pressure ranges, the error is barely more than the error associated with the stan dard Goldmann tonometer, which is at least ±2 mm Hg. Although the measurements of higher intraocular pressure may be mislead ing when associated with an error greater than ±3 mm Hg, intraocular pressure alone should never constitute the sole reason for clinical judgments. Regardless of the method used, any intraocular pressure measurement is an approximation, and should be evaluated in the whole context of the problem. At high er intraocular pressures, the error in measure ment is likely to be greater with any instru ment, including the Goldmann tonometer. We could only assume that the Goldmann meas urements were accurate as they were impossi ble to verify. Dr. Higginbotham's suggestion that the Tono-Pen may have special application for in traocular pressure measurements in compli cated cases such as uncooperative patients or patients with irregularly shaped corneas is somewhat inconsistent with her concerns about the instrument's accuracy, since no study has yet determined the Tono-Pen's error in such cases. We predict, however, that the error rate for any instrument in a complicated case would be far greater. Therefore, judg ments of therapy based on intraocular pres sure measurements would be more problemat ic in these cases. DON S. MINCKLER, M.D.
La Jolla, California GEORGE BAERVELDT, M.D. DALE K. HEUER, M.D. BETH QUILLEN-THOMAS, B.SC. A. FRANCES WALONKER, D.B.O. JOHN WEINER, DR.P.H.
Los Angeles, California
January, 1988
AMERICAN JOURNAL OF OPHTHALMOLOGY
no further visual loss or optic disk change.
References 1. Posner, A., and Schlossman, A.: Syndrome of unilateral recurrent attacks of glaucoma with cyclitic symptoms. Arch. Ophthalmol. 39:517, 1948. 2. Kass, M. A., Becker, B., and Kolker, A. E.: Glaucomatocyclitic crisis and primary open-angle glaucoma. Am. J. Ophthalmol. 75:668, 1973. 3. Nagataki, S., and Mishima, S.: Aqueous humor dynamics in glaucomatocyclitic crisis. Invest. Oph thalmol. Vis. Sci. 15:365, 1976.
Correspondence Correspondence concerning recent articles or other mate rial published in THE JOURNAL should be submitted within six weeks of publication. Correspondence must be typed double-spaced, on 8V2 x 11-inch bond paper with lVi-inch margins on all four sides and should be no more than two typewritten pages in length. Every effort will be made to resolve controversies between the correspondents and the authors of the article before publication.
conjunctival flap as compared to a deeper chamber with the limbal-based flap, although both were comparable after the first week. The progressive shallowing of the anterior chamber is related to their technique in which the limbal end of the two radial incisions of the lamellar scleral flap were left unsutured. This allows the aqueous humor to drain through the radial incision at the corneoscleral limbus; spread along the front edge of the conjunctival flap, which is tightly opposed to the sclera; and leak out at the edges of the conjunctival flap through the absorbable su ture site. If the conjunctival flap is not snugly opposed to the sclera, then the aqueous humor may drain freely through the front edge of the conjunctival flap. This would cause an even higher incidence of shallow anterior chamber or even flat anterior cham ber than the authors described. When a fornix-based flap is used, the presence of a shallow anterior chamber during the week after surgery can be almost totally eliminated by suturing the limbal edge of the two radial incisions. I have found it easier to oppose directly the conjunctival flap and prevent leakage at the site of the conjunctival suture when 10-0 nylon sutures rather than absorbable sutures are used. MAURICE H. LUNTZ, M.D.
New York, New York
Limbal- vs Fornix-Based Conjunctival Trabeculectomy Flaps
Reply EDITOR:
EDITOR:
In the article "Limbal- vs fornix-based con junctival trabeculectomy flaps," by Carlo E. Traverso, Karim F. Tomey, and Sobhi Antonios (Am. J. Ophthalmol. 104:28, July 1987), the authors concentrate on the length of the surgical procedure and the overall results. They concluded that there is little difference in the results of the two procedures or the time taken to perform the surgical proce dures. I wish to comment on some aspects of trabeculectomy when using a conjunctivoTenon's flap, which I belive add to the safety of the operation. The authors report progressive shallowing of the anterior chamber with the fornix-based
Dr. Luntz's observations are most appropri ate and should be taken into consideration before switching from limbal-based to fornixbased conjunctival flaps for trabeculectomy. Indeed, additional sutures at the radial inci sions of the lamellar scleral flap help reduce postoperative hypotony. We usually tie our sutures only at the corners of the scleral flap to obtain some drainage of the aqueous humor. Should the scleral flap be left too loose, profound postoperative hypotony and a shallow or flat anterior chamber will be like ly to occur, regardless of whether the con junctival flap is limbal or fornix-based. As ap propriately pointed out by Dr. Luntz, postoperative hypotony and a shallow or flat
Vol. 105, No. 1
Correspondence
anterior chamber may be particularly evident when fornix-based conjunctival flaps are used, especially if the flap is sutured too loosely. Regarding the use of nylon vs absorbable sutures, we have been pleased with the latter, probably because we have them available mounted on tapered needles. Certainly, 10-0 nylon can be a good alternative. CARLO E. TRAVERSO, M.D. KARIM F. TOMEY, M.D. SOBHI R. ANTONIOS, M.D.
Riyadh, Saudi Arabia
Clinical Evaluation of the Oculab Tono-Pen EDITOR:
In the article "Clinical evaluation of the Oculab Tono-Pen," by D. S. Minckler, G. Baerveldt, D. Heuer, B. Quillen-Thomas, A. F. Walonker, and J. Weiner (Am. J. Ophthalmol. 104:168, August 1987), the authors conclude that the differences in intraocular pressure measured by this instrument are not "clinically troublesome." Of the 270 eyes studied, intraocular pressure in approximately 39% of the eyes measured outside an error range of ±3 mm Hg. Many of these eyes had high intraocular pressures. Because surgical decisions in glaucoma are influenced by intra ocular pressures, I believe that a qualification should be placed on the use of this instru ment in patients with glaucoma. Although the authors found no statistically significant dif ference in intraocular pressure that measured greater than 24 mm Hg (P = .30), the error in the measurement may be clinically significant for a glaucoma patient. The Tono-Pen may be a convenient and an accurate means for measuring intraocular pressure in uncooperative patients or in pa tients with irregularly shaped corneas. How ever, the impression that this instrument, with its "trivial differences" in measurement, can replace the Goldmann applanation to nometer in treating patients with high intra ocular pressure should not be given. EVE J. HIGGINBOTHAM, M.D.
Chicago, Illinois
101
Reply EDITOR:
We appreciate Dr. Higginbotham's concern regarding our statement that the "small un derestimation of intraocular pressure with the Tono-Pen in eyes with high intraocular pres sure . . . is not considered likely to be clini cally troublesome." That statement was based on our belief that a relatively small error (±3 mm Hg) in the majority of serial intraocular pressure measurements should not adversely affect therapy judgments in glaucoma pa tients. We do not believe that an error of this magnitude is clinically problematic because in the same pressure ranges, the error is barely more than the error associated with the stan dard Goldmann tonometer, which is at least ±2 mm Hg. Although the measurements of higher intraocular pressure may be mislead ing when associated with an error greater than ±3 mm Hg, intraocular pressure alone should never constitute the sole reason for clinical judgments. Regardless of the method used, any intraocular pressure measurement is an approximation, and should be evaluated in the whole context of the problem. At high er intraocular pressures, the error in measure ment is likely to be greater with any instru ment, including the Goldmann tonometer. We could only assume that the Goldmann meas urements were accurate as they were impossi ble to verify. Dr. Higginbotham's suggestion that the Tono-Pen may have special application for in traocular pressure measurements in compli cated cases such as uncooperative patients or patients with irregularly shaped corneas is somewhat inconsistent with her concerns about the instrument's accuracy, since no study has yet determined the Tono-Pen's error in such cases. We predict, however, that the error rate for any instrument in a complicated case would be far greater. Therefore, judg ments of therapy based on intraocular pres sure measurements would be more problemat ic in these cases. DON S. MINCKLER, M.D.
La Jolla, California GEORGE BAERVELDT, M.D. DALE K. HEUER, M.D. BETH QUILLEN-THOMAS, B.SC. A. FRANCES WALONKER, D.B.O. JOHN WEINER, DR.P.H.
Los Angeles, California