Laser Placement in Noncontact Nd:YAG Cyclophotocoagulation Brent M. Crymes, M.D., and Ronald L. Gross, M.D.
We treated 40 eyes of 40 patients by using noncontact transscleral Nd:YAG cyclophotocoagulation to determine whether treatment 1.5 or 3.0 mm posterior to the corneoscleral limbus was preferable. Patients were randomly assigned to one of the treatment groups, and all other variables, including power, number, and distribution of laser applications, were kept constant. Six months postoperatively, those treated 1.5 mm posterior to the corneoscleral limbus had a lower intraocular pressure (P = .0047) than those treated 3.0 mm from the corneoscleral limbus. The 1.5-mm group also required fewer retreatments (P = .017) and had a slightly lower occurrence of visual acuity loss after this procedure. We believe it may be advantageous to locate the laser application approximately 1.5 mm posterior to the corneosclerallimbus, rather than further posteriorly, when performing noncontact transscleral Nd:YAG cyclophotocoagulation.
T HE TREATMENT OF REFRACTORY GLAUCOMA with laser ciliary body ablation was originally reported by Beckman and associates.P That procedure was not feasible for general use because of the unavailability of the ruby laser. Beckman and Sugar" then reported cycloablation by the more widely available Nd:YAG laser. In 1986, Fankhauser and associates" reported an autopsy study of human eyes using the Nd:YAG laser to perform cyclophotocoagulation. Since that time, noncontact thermal-mode
Nd:YAG laser cyclophotocoagulation has been shown to be effective in decreasing intraocular pressure in rabbit'" and human eyes that are refractory to medical or traditional surgical therapy.?" In many of these studies, application of laser energy 3.0 to 3.5 mm posterior to the surgical corneoscleral limbus was effective in decreasing intraocular pressure. Schubert and Federrnann" postulated that the effect of Nd:YAG laser cyclophotocoagulation is secondary to the inflammatory process caused by absorption of energy remote from the pars plicata. Recent histopathologic evidence in human eyes demonstrated that placing the laser lesion 1.0 to 1.5 mm from the surgical corneoscleral limbus preferentially destroyed the pars plicata and ciliary processes.l'" Because of the absence of a significant inflammatory response or evidence of necrosis or hemorrhage within the ciliary muscle in these studies, it seems reasonable that intraocular pressure reduction is caused by ablation of the pigmented and nonpigmented ciliary epithelium. Because of the controversy surrounding the exact mechanism of action of Nd:YAG cyclophotocoagulation and the subsequent indecision as to the appropriate placement of laser lesions, we studied whether there is any difference in decreasing intraocular pressure or complication rates after transscleral Nd:YAG cyclophotocoagulation by using 1.5- or 3.0-mm distance from the surgical corneoscleral limbus as the site of treatment.
Patients and Methods Accepted for publication Aug. 28, 1990. From the Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas. Reprint requests to Ronald L. Gross, M.D., Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, 6501 Fannin, NC200, Houston, TX 77030.
670
Forty patients (40 eyes) were selected who met the following criteria for cycloablation: glaucoma refractory to medical therapy, previous failed surgical glaucoma treatment, aphakia or pseudophakia, and intraocular pressure
©AMERICAN JOURNAL OF OPHTHALMOLOGY
110:670-673,
DECEMBER,
1990
Noncontact Nd:YAG Cyclophotocoagulation
Vol. 110, No.6
greater than 25 mm Hg. Phakic eyes and patients who had previous cyclodestructive procedures were excluded from this study. No patients were excluded on the basis of vision or diagnosis. The patients were randomly assigned into one of two treatment groups: those treated 1.5 mm from the surgical corneosclerallimbus and those treated 3.0 mm from the surgical corneoscleral limbus. Patients received retrobulbar anesthesia consisting of a 50:50 mixture of 0.5% bupivacaine hydrochloride and 2% lidocaine hydrochloride without hyaluronidase or epinephrine. Complete anesthesia in all quadrants was then tested and assured. The patients were then placed at the Nd:YAG laser set on thermal mode (20 milliseconds high). Variables for treatment included the following: maximum posterior focus offset (nine), single pulse, and power of 5.5 to 6.5 J. A wire eyelid speculum was placed in the eye. No contact lens was used. Each eye received 40 applications (ten per quadrant), placed 360 degrees circumlimbal 1.5 or 3.0 mm from the surgical corneoscleral limbus. The distance of laser application was measured with calipers with the eye maintained in the frontal plane. Postoperatively patients were given prednisolone acetate 1% every two hours while awake and atropine 1% four times a day for two weeks. Glaucoma medications, except for miotics. were continued until the intraocular pressure was controlled and were stopped as warranted by the clinical situation. Patients were given oral analgesics to be used as needed. Data were collected at one day, one week, one month, three months, six months, and one year postoperatively. Retreatment was performed using identical treatment variables if intraocular pressure was inadequately controlled and the patient again met the criteria for cycloablation. A minimum of three months was necessary after the previous treatment before retreatment was considered. Data at each time point from the initial treatment were analyzed with subsequent retreatment included. Statistical analyses were performed by using the normal deviate and Mann Whitney tests.
Results In the 1.5-mm group, the average age of the patients was 64.2 years. Ten patients were male
671
and ten patients were female. Eleven patients were black, six were white, and three were hispanic. Of the 20 affected eyes, 11 were right eyes and nine were left eyes. Angle-closure glaucoma was diagnosed in 14 patients; primary open-angle glaucoma was diagnosed in five patients; and neovascular glaucoma was diagnosed in one patient. In the 3.0-mm group, the average age of the patients was 66.1 years. Seven patients were male and 13 patients were female. Ten patients were black, eight were white, and two were hispanic. Of the 20 affected eyes, ten were right eyes and ten were left eyes. Angle-closure glaucoma was diagnosed in 11 patients; primary open-angle glaucoma was diagnosed in seven patients; and neovascular glaucoma was diagnosed in two patients. There was no significant difference in the demographic data between the two treatment groups. The diagnosis distribution was similar for both groups with most of the patients having secondary angle-closure glaucoma. Only a small number of patients had neovascular glaucoma. The mean number of patients who had had previous glaucoma operations was 2.25 in the 1.5-mm group and 2.3 in the 3.0-mm group. The mean number of glaucoma medications taken by patients was 2.25 in the 1.5-mm group and 2.7 in the 3.0-mm group. The average intraocular pressure was 41.9 mm Hg in the 1.5-mm group and 38.1 mm Hg in the 3.0-mm group. The postoperative mean intraocular pressure curves (Figure) exhibit an immediate reduction of intraocular pressure after the procedure on the first postoperative day, which continued through the first week postoperatively and was similar for the two treatment groups. Mean intraocular pressures were stable from one to three months in both groups. By six months, the 1.5-mm group showed continued reduction of intraocular pressure within an acceptable range, whereas the 3.0-mm group showed a gradual increase of mean intraocular pressure with time. Conversely, with regard to change in intraocular pressure, the 3.0-mm group showed an increase in intraocular pressure with time, which was statistically significant at six months postoperatively (P = .0047, Mann Whitney test). This difference was also noted at the one-year interval but was not statistically significant because of a smaller sample size,
672
AMERICAN JOURNAL OF OPHTHALMOLOGY
December, 1990
IntraoclJar Pressure (nvn Hg) 50,------------------------, ~
1.5mm
n = 2lI
-,A- a.Onvn
Figure (Crymes and Gross). Comparison of mean intraocular pressure after Nd:YAG cyclophotocoagulation in eyes treated 1.5 mm and 3.0 mm posterior to the corneoscleral limbus with power, number, and distribution of applications equivalent.
o
L - l_ _---'---_ _- ' - - - - _ - - ' -
Pre-op
1d
1w
1m
---L-_ _' - - _ - - - - ' - - - - '
3m
8m
12m
TIme
caused by the loss of some patients to followup. Additionally, the patients in the 3.0-mm treatment group required significantly more retreatments (seven of 20 patients) than the 1.5mm treatment group (one of 20 patients) because of poorly controlled intraocular pressure (P = .017, normal deviate). In those eyes retreated, four were treated three months and three were treated six months after the initial cyclophotocoagulation. The mean number of medications required postoperatively at the last follow-up period was reduced for both groups in an equivalent fashion, with the average number of medications for the 1.5-mm treatment group being 1.15 compared with 1.4 for the 3.0-mm treatment group. All of the patients had some inflammation and pain postoperatively. In almost all patients, the inflammation and pain resolved within one week with cycloplegics, topical corticosteroids, and oral analgesics. Only three of the 40 patients had mild inflammation one month postoperatively and none had pain after one week. There was no difference between the two groups in this respect. None of the patients developed phthisis bulbi, vitreous hemorrhage, hypopyon, or choroidal effusions. Although there were several patients in each group with intraocular pressure of less than 5 mm Hg, none of these patients had a worsening of vision from the
preoperative level that could be attributed to hypotony. Severe visual loss (defined as a loss of greater than four lines of visual acuity, visual acuity loss to counting fingers from better than 20/ 400, or visual acuity of no light perception) occurred in three patients. Visual acuity in one patient in the 1.5-mm group progressed to no light perception from a preoperative level of bare light perception without projection. This was believed to be secondary to severe neovascular glaucoma that could not be controlled with repeated attempts at Nd:YAG cyclophotocoagulation and cyclocryotherapy. Two patients in the 3.0-mm treatment group had visual acuity of less than 20/400. In all three patients, the visual loss was believed to be associated with uncontrolled intraocular pressures. Overall, 12 of 40 patients (30%) lost at least one line of Snellen visual acuity. The 3.0-mm group had 40% (eight of 20 patients) visual acuity loss, which was greater than the 20% (four of 20 patients) in the 1.5-mm group, but this was not statistically significant. There were instances of substantial improvement of vision (four lines of visual acuity improvement or at least 20/400 visual acuity from counting fingers or worse) in both groups, although this was more frequent in the 1.5-mm treated group (30% [six of 20 patients] compared with 10% [two of 20 patients]). In most
Vol. 110, No.6
Noncontact Nd:YAG Cyclophotocoagulation
673
patients this was attributable to clearing of corneal edema.
References
Discussion
1. Beckman, H., Kinoshita, A., Rota, A. N., and Sugar, H. S.: Transscleral ruby laser irradiation of the ciliary body in the treatment of intractable glaucoma. Trans. Am. Acad. Ophthalmol. Otolaryngol.
Laser cyclophotocoagulation with the Nd:YAG laser has become an accepted mode of treatment for patients with refractory glaucoma. Controversy exists in published reports regarding the mechanism of action and appropriate location of lesion placement of Nd:YAG cyclophotocoagulation. If cyclophotocoagulation acts by destroying ciliary body epithelium with a resultant direct reduction of aqueous humor formation, then based on histologic evidence,":" 1.0 to 1.5 mm from the surgical corneosclerallimbus should be the preferred location of treatment. If this treatment is effective through an indirect effect on an inflammatory response, reduction in vascular supply to the ciliary body epithelium, or increased uveal sclera outflow, however, then treatment further posterior to the corneoscleral limbus may be more advantageous." We demonstrated that placing the laser lesion closer to the surgical corneosclerallimbus at 1.5 mm results in a greater reduction of intraocular pressure with less frequent need of retreatment for glaucoma control in the initial six months postoperatively. The contrast in effectiveness of the two treatment groups is even more dramatic because a significant difference in intraocular pressure reduction was noted despite a higher percentage of retreatments in the 3.0-mm group, which suggests that the differences may actually be greater. In our study, severe complications, such as severe visual loss, vitreous hemorrhage, or phthisis, were infrequent. However, in other studies, all of these potential serious complications have occurred with this treatment. Nd:YAG cyclophotocoagulation is a ciliary body-destructive technique that carries inherent risks and should not be used indiscriminately.
76:423,1972. 2. Beckman, H.: Transscleral photocoagulation of
the ciliary body. In Wilensky, ]. T.: Laser Therapy in Glaucoma. Norwalk, Appleton-Century-Crofts, 1984, pp. 117-122. 3. Beckman, H., and Sugar, H. S.: Neodymium laser cyclocoagulation. Arch. Ophthalmol. 90:27, 1973.
4. Fankhauser, F., van der Zypen, E., Kwasniewska, S., Ro, P., and England, c.: Transscleral cyclophotocoagulation using a neodymium:YAG laser. Ophthalmic Surg. 17:94, 1986. 5. Wilensky,]. T., Welch, D., and Mirolovich, M.: Transscleral cyclocoagulation using a neodymium:YAG laser. Ophthalmic Surg. 16:95, 1985. 6. Gross, R. L., Smith,]. A., and Font, R. L.: Transscleral Nd:YAG laser cycloablation in rabbits. ARVO abstracts. Supplement to Invest. Ophthalmol. Vis. Sci. Philadelphia,]. B. Lippincott, 1986, p. 253. 7. Schwartz, L. W., and Moster, M. R.: Neodymium:YAG laser transscleral cyclodiathermy. Ophthalmic Laser Ther. 1:135, 1986. 8. Devenyi, R. G., Trope, G. E., and Hunter, W. H.: Neodymium:YAG transscleral cyclocoagulation in human eyes. Ophthalmology 94:1519,1987. 9. Klapper, R. M., Wandel, T., Donnenfeld, E., and Perry, H. D.: Transscleral neodymium:YAG thermal cyclophotocoagulation in refractory glaucoma. A preliminary report. Ophthalmology 95:719,1988. 10. Schubert, H. D., and Federmann, ]. L.: Inflammation in CW Nd:YAG contact transscleral photocoagulation and cryopexy. Invest. Ophthalmol. Vis. Sci. 30:3, 1989. 11. Hampton, c., and Shields, M. B.: Transscleral neodymium:YAG cyclophotocoagulation. A histologic study in human autopsy eyes. Arch. Ophthalmol. 108:1121,1988. 12. Shields, S. M., Stevens, ]. L., Kass, M. A., and
Smith, M. E.: Histopathologic findings after Nd:YAG transscleral cyclophotocoagulation. Am. ]. Ophthalmol. 106:100, 1988. 13. Blasini, M., Simmons, R., and Shields, M. B.: Early tissue response to transscleral Nd:YAG CPC. Invest. Ophthaimoi. Vis. Sci. 31:6, 1990.
We treated 40 eyes of 40 patients by using noncontact transscleral Nd:YAG cyclophotocoagulation to determine whether treatment 1.5 or 3.0 mm posterior to the corneoscleral limbus was preferable. Patients were randomly assigned to one of the treatment groups, and all other variables, including power, number, and distribution of laser applications, were kept constant. Six months postoperatively, those treated 1.5 mm posterior to the corneoscleral limbus had a lower intraocular pressure (P = .0047) than those treated 3.0 mm from the corneoscleral limbus. The 1.5-mm group also required fewer retreatments (P = .017) and had a slightly lower occurrence of visual acuity loss after this procedure. We believe it may be advantageous to locate the laser application approximately 1.5 mm posterior to the corneosclerallimbus, rather than further posteriorly, when performing noncontact transscleral Nd:YAG cyclophotocoagulation.
T HE TREATMENT OF REFRACTORY GLAUCOMA with laser ciliary body ablation was originally reported by Beckman and associates.P That procedure was not feasible for general use because of the unavailability of the ruby laser. Beckman and Sugar" then reported cycloablation by the more widely available Nd:YAG laser. In 1986, Fankhauser and associates" reported an autopsy study of human eyes using the Nd:YAG laser to perform cyclophotocoagulation. Since that time, noncontact thermal-mode
Nd:YAG laser cyclophotocoagulation has been shown to be effective in decreasing intraocular pressure in rabbit'" and human eyes that are refractory to medical or traditional surgical therapy.?" In many of these studies, application of laser energy 3.0 to 3.5 mm posterior to the surgical corneoscleral limbus was effective in decreasing intraocular pressure. Schubert and Federrnann" postulated that the effect of Nd:YAG laser cyclophotocoagulation is secondary to the inflammatory process caused by absorption of energy remote from the pars plicata. Recent histopathologic evidence in human eyes demonstrated that placing the laser lesion 1.0 to 1.5 mm from the surgical corneoscleral limbus preferentially destroyed the pars plicata and ciliary processes.l'" Because of the absence of a significant inflammatory response or evidence of necrosis or hemorrhage within the ciliary muscle in these studies, it seems reasonable that intraocular pressure reduction is caused by ablation of the pigmented and nonpigmented ciliary epithelium. Because of the controversy surrounding the exact mechanism of action of Nd:YAG cyclophotocoagulation and the subsequent indecision as to the appropriate placement of laser lesions, we studied whether there is any difference in decreasing intraocular pressure or complication rates after transscleral Nd:YAG cyclophotocoagulation by using 1.5- or 3.0-mm distance from the surgical corneoscleral limbus as the site of treatment.
Patients and Methods Accepted for publication Aug. 28, 1990. From the Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas. Reprint requests to Ronald L. Gross, M.D., Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, 6501 Fannin, NC200, Houston, TX 77030.
670
Forty patients (40 eyes) were selected who met the following criteria for cycloablation: glaucoma refractory to medical therapy, previous failed surgical glaucoma treatment, aphakia or pseudophakia, and intraocular pressure
©AMERICAN JOURNAL OF OPHTHALMOLOGY
110:670-673,
DECEMBER,
1990
Noncontact Nd:YAG Cyclophotocoagulation
Vol. 110, No.6
greater than 25 mm Hg. Phakic eyes and patients who had previous cyclodestructive procedures were excluded from this study. No patients were excluded on the basis of vision or diagnosis. The patients were randomly assigned into one of two treatment groups: those treated 1.5 mm from the surgical corneosclerallimbus and those treated 3.0 mm from the surgical corneoscleral limbus. Patients received retrobulbar anesthesia consisting of a 50:50 mixture of 0.5% bupivacaine hydrochloride and 2% lidocaine hydrochloride without hyaluronidase or epinephrine. Complete anesthesia in all quadrants was then tested and assured. The patients were then placed at the Nd:YAG laser set on thermal mode (20 milliseconds high). Variables for treatment included the following: maximum posterior focus offset (nine), single pulse, and power of 5.5 to 6.5 J. A wire eyelid speculum was placed in the eye. No contact lens was used. Each eye received 40 applications (ten per quadrant), placed 360 degrees circumlimbal 1.5 or 3.0 mm from the surgical corneoscleral limbus. The distance of laser application was measured with calipers with the eye maintained in the frontal plane. Postoperatively patients were given prednisolone acetate 1% every two hours while awake and atropine 1% four times a day for two weeks. Glaucoma medications, except for miotics. were continued until the intraocular pressure was controlled and were stopped as warranted by the clinical situation. Patients were given oral analgesics to be used as needed. Data were collected at one day, one week, one month, three months, six months, and one year postoperatively. Retreatment was performed using identical treatment variables if intraocular pressure was inadequately controlled and the patient again met the criteria for cycloablation. A minimum of three months was necessary after the previous treatment before retreatment was considered. Data at each time point from the initial treatment were analyzed with subsequent retreatment included. Statistical analyses were performed by using the normal deviate and Mann Whitney tests.
Results In the 1.5-mm group, the average age of the patients was 64.2 years. Ten patients were male
671
and ten patients were female. Eleven patients were black, six were white, and three were hispanic. Of the 20 affected eyes, 11 were right eyes and nine were left eyes. Angle-closure glaucoma was diagnosed in 14 patients; primary open-angle glaucoma was diagnosed in five patients; and neovascular glaucoma was diagnosed in one patient. In the 3.0-mm group, the average age of the patients was 66.1 years. Seven patients were male and 13 patients were female. Ten patients were black, eight were white, and two were hispanic. Of the 20 affected eyes, ten were right eyes and ten were left eyes. Angle-closure glaucoma was diagnosed in 11 patients; primary open-angle glaucoma was diagnosed in seven patients; and neovascular glaucoma was diagnosed in two patients. There was no significant difference in the demographic data between the two treatment groups. The diagnosis distribution was similar for both groups with most of the patients having secondary angle-closure glaucoma. Only a small number of patients had neovascular glaucoma. The mean number of patients who had had previous glaucoma operations was 2.25 in the 1.5-mm group and 2.3 in the 3.0-mm group. The mean number of glaucoma medications taken by patients was 2.25 in the 1.5-mm group and 2.7 in the 3.0-mm group. The average intraocular pressure was 41.9 mm Hg in the 1.5-mm group and 38.1 mm Hg in the 3.0-mm group. The postoperative mean intraocular pressure curves (Figure) exhibit an immediate reduction of intraocular pressure after the procedure on the first postoperative day, which continued through the first week postoperatively and was similar for the two treatment groups. Mean intraocular pressures were stable from one to three months in both groups. By six months, the 1.5-mm group showed continued reduction of intraocular pressure within an acceptable range, whereas the 3.0-mm group showed a gradual increase of mean intraocular pressure with time. Conversely, with regard to change in intraocular pressure, the 3.0-mm group showed an increase in intraocular pressure with time, which was statistically significant at six months postoperatively (P = .0047, Mann Whitney test). This difference was also noted at the one-year interval but was not statistically significant because of a smaller sample size,
672
AMERICAN JOURNAL OF OPHTHALMOLOGY
December, 1990
IntraoclJar Pressure (nvn Hg) 50,------------------------, ~
1.5mm
n = 2lI
-,A- a.Onvn
Figure (Crymes and Gross). Comparison of mean intraocular pressure after Nd:YAG cyclophotocoagulation in eyes treated 1.5 mm and 3.0 mm posterior to the corneoscleral limbus with power, number, and distribution of applications equivalent.
o
L - l_ _---'---_ _- ' - - - - _ - - ' -
Pre-op
1d
1w
1m
---L-_ _' - - _ - - - - ' - - - - '
3m
8m
12m
TIme
caused by the loss of some patients to followup. Additionally, the patients in the 3.0-mm treatment group required significantly more retreatments (seven of 20 patients) than the 1.5mm treatment group (one of 20 patients) because of poorly controlled intraocular pressure (P = .017, normal deviate). In those eyes retreated, four were treated three months and three were treated six months after the initial cyclophotocoagulation. The mean number of medications required postoperatively at the last follow-up period was reduced for both groups in an equivalent fashion, with the average number of medications for the 1.5-mm treatment group being 1.15 compared with 1.4 for the 3.0-mm treatment group. All of the patients had some inflammation and pain postoperatively. In almost all patients, the inflammation and pain resolved within one week with cycloplegics, topical corticosteroids, and oral analgesics. Only three of the 40 patients had mild inflammation one month postoperatively and none had pain after one week. There was no difference between the two groups in this respect. None of the patients developed phthisis bulbi, vitreous hemorrhage, hypopyon, or choroidal effusions. Although there were several patients in each group with intraocular pressure of less than 5 mm Hg, none of these patients had a worsening of vision from the
preoperative level that could be attributed to hypotony. Severe visual loss (defined as a loss of greater than four lines of visual acuity, visual acuity loss to counting fingers from better than 20/ 400, or visual acuity of no light perception) occurred in three patients. Visual acuity in one patient in the 1.5-mm group progressed to no light perception from a preoperative level of bare light perception without projection. This was believed to be secondary to severe neovascular glaucoma that could not be controlled with repeated attempts at Nd:YAG cyclophotocoagulation and cyclocryotherapy. Two patients in the 3.0-mm treatment group had visual acuity of less than 20/400. In all three patients, the visual loss was believed to be associated with uncontrolled intraocular pressures. Overall, 12 of 40 patients (30%) lost at least one line of Snellen visual acuity. The 3.0-mm group had 40% (eight of 20 patients) visual acuity loss, which was greater than the 20% (four of 20 patients) in the 1.5-mm group, but this was not statistically significant. There were instances of substantial improvement of vision (four lines of visual acuity improvement or at least 20/400 visual acuity from counting fingers or worse) in both groups, although this was more frequent in the 1.5-mm treated group (30% [six of 20 patients] compared with 10% [two of 20 patients]). In most
Vol. 110, No.6
Noncontact Nd:YAG Cyclophotocoagulation
673
patients this was attributable to clearing of corneal edema.
References
Discussion
1. Beckman, H., Kinoshita, A., Rota, A. N., and Sugar, H. S.: Transscleral ruby laser irradiation of the ciliary body in the treatment of intractable glaucoma. Trans. Am. Acad. Ophthalmol. Otolaryngol.
Laser cyclophotocoagulation with the Nd:YAG laser has become an accepted mode of treatment for patients with refractory glaucoma. Controversy exists in published reports regarding the mechanism of action and appropriate location of lesion placement of Nd:YAG cyclophotocoagulation. If cyclophotocoagulation acts by destroying ciliary body epithelium with a resultant direct reduction of aqueous humor formation, then based on histologic evidence,":" 1.0 to 1.5 mm from the surgical corneosclerallimbus should be the preferred location of treatment. If this treatment is effective through an indirect effect on an inflammatory response, reduction in vascular supply to the ciliary body epithelium, or increased uveal sclera outflow, however, then treatment further posterior to the corneoscleral limbus may be more advantageous." We demonstrated that placing the laser lesion closer to the surgical corneosclerallimbus at 1.5 mm results in a greater reduction of intraocular pressure with less frequent need of retreatment for glaucoma control in the initial six months postoperatively. The contrast in effectiveness of the two treatment groups is even more dramatic because a significant difference in intraocular pressure reduction was noted despite a higher percentage of retreatments in the 3.0-mm group, which suggests that the differences may actually be greater. In our study, severe complications, such as severe visual loss, vitreous hemorrhage, or phthisis, were infrequent. However, in other studies, all of these potential serious complications have occurred with this treatment. Nd:YAG cyclophotocoagulation is a ciliary body-destructive technique that carries inherent risks and should not be used indiscriminately.
76:423,1972. 2. Beckman, H.: Transscleral photocoagulation of
the ciliary body. In Wilensky, ]. T.: Laser Therapy in Glaucoma. Norwalk, Appleton-Century-Crofts, 1984, pp. 117-122. 3. Beckman, H., and Sugar, H. S.: Neodymium laser cyclocoagulation. Arch. Ophthalmol. 90:27, 1973.
4. Fankhauser, F., van der Zypen, E., Kwasniewska, S., Ro, P., and England, c.: Transscleral cyclophotocoagulation using a neodymium:YAG laser. Ophthalmic Surg. 17:94, 1986. 5. Wilensky,]. T., Welch, D., and Mirolovich, M.: Transscleral cyclocoagulation using a neodymium:YAG laser. Ophthalmic Surg. 16:95, 1985. 6. Gross, R. L., Smith,]. A., and Font, R. L.: Transscleral Nd:YAG laser cycloablation in rabbits. ARVO abstracts. Supplement to Invest. Ophthalmol. Vis. Sci. Philadelphia,]. B. Lippincott, 1986, p. 253. 7. Schwartz, L. W., and Moster, M. R.: Neodymium:YAG laser transscleral cyclodiathermy. Ophthalmic Laser Ther. 1:135, 1986. 8. Devenyi, R. G., Trope, G. E., and Hunter, W. H.: Neodymium:YAG transscleral cyclocoagulation in human eyes. Ophthalmology 94:1519,1987. 9. Klapper, R. M., Wandel, T., Donnenfeld, E., and Perry, H. D.: Transscleral neodymium:YAG thermal cyclophotocoagulation in refractory glaucoma. A preliminary report. Ophthalmology 95:719,1988. 10. Schubert, H. D., and Federmann, ]. L.: Inflammation in CW Nd:YAG contact transscleral photocoagulation and cryopexy. Invest. Ophthalmol. Vis. Sci. 30:3, 1989. 11. Hampton, c., and Shields, M. B.: Transscleral neodymium:YAG cyclophotocoagulation. A histologic study in human autopsy eyes. Arch. Ophthalmol. 108:1121,1988. 12. Shields, S. M., Stevens, ]. L., Kass, M. A., and
Smith, M. E.: Histopathologic findings after Nd:YAG transscleral cyclophotocoagulation. Am. ]. Ophthalmol. 106:100, 1988. 13. Blasini, M., Simmons, R., and Shields, M. B.: Early tissue response to transscleral Nd:YAG CPC. Invest. Ophthaimoi. Vis. Sci. 31:6, 1990.
