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Early Complications Following Q-switched Neodymium:YAG Laser Posterior Capsulotomy
Early Complications Following Q-switched Neodymium: Y AG Laser Posterior Capsulotomy MICHAEL J. FLOHR, MD, ALAN L. ROBIN, MD, JAMES S. KELLEY, MD
Abstract: A prospective evaluation was conducted of Q-switched neodymium: YAG laser capsulotomy in 53 eyes followed for one postoperative month. The first 31 eyes were seen at two-hour intervals for the first eight hours, and the remaining eyes were checked only at the second postoperative hour during that day. Eighty-nine percent of eyes required a pulse setting of less than 1.7 mJ to successfully penetrate the posterior capsule. Visual acuity was improved in 91 % of eyes. A transient immediate postoperative intraocular pressure (lOP) elevation was seen in over 75% of treated eyes, and one-third had an lOP elevation greater than 10 mmHg over the preoperative lOP. This elevation was most common in glaucomatous eyes and occurred in almost one-half of the treated eyes by the second postoperative hour. This lOP change did not correlate with the degree of inflammation, bleeding , anterior chamber debris, or total energy delivered. Minimal iris bleeding occurred in 9% of treated eyes and was associated with iridocapsular adhesions. Eighty-one percent of eyes with posterior chamber implants developed some degree of lens damage. [Key words: cataract, capsulotomy, glaucoma, hyphema, intraocular lens, neodymium:YAG laser.] Ophthalmology 92:360-363, 1985
The increasing trend towards extracapsular cataract extraction is well established. A 25 to 50% rate of significant posterior capsule opacification following this procedure has been reported. 1- 5 Until recently, intraocular surgery was the only available method of opening an opacified posterior capsule to restore vision. Because of the intraocular nature of this procedure, it is associated with rare complications such as endophthalmitis. The neodymium (Nd):Y AG laser presents an alternative method of performing a posterior capsulotomy without opening the eye, therefore eliminating some of these
complications. However, the short- and long-term effects of laser surgery are only now beginning to be explored. Recent reports have demonstrated a significant incidence of immediate postoperative intraocular pressure (lOP) elevation following Nd:YAG posterior capsulotomy.6-7 Confirmation and further analysis of the incidence, rate of onset, duration, and severity of these complications is warranted. Therefore, we conducted a prospective analysis of patients undergoing Nd:YAG laser posterior capsulotomies and report our short-term results.
MATERIALS AND METHODS From the Departments of Ophthalmology, Greater Baltimore Medical Center; and the Glaucoma Service, Wilmer Institute, Johns Hopkins Hospital, Baltimore. Reprint requests to Alan L. Robin, MD, the Wilmer Institute, Maumenee Building Room B·117, The Johns Hopkins Hospital, 600 N. Wolfe St., Baltimore, MD 21205.
360
The criteria for entry into our study was decreased visual acuity or visual symptoms due to posterior capsular opacification, or wrinkling in patients following extracapsular cataract extraction. All patients were aware of the investigational nature of this technique and gave
FLOHR, el aI
•
LASER CAPSULOTOMIES
Mean Intraocular Pressure After YAG Capsulotomy
A Comparison of Preoperative and Postoperotive Visual Acuities
•
hand mo,ions counl finoers
6/120 6/60
•
6/30
•
6/24
6/21
.~ "0 a;
"o
d:"
6/18 6115
•
•
•
•
•
'lit
"" • • •
••
.
•••
•
26
• •
24
•
6/12 6/9
c;. 22 I
E E a. 20 Q
~r......"n.53
18
6/7.5 6/6
16
L -_ _ _ _L-____L-____~____~~,~~~/~
PreOp
2 hrs
4hrs
6hrs Time
8hrs
Iwk
lmon
Fig 1. Preoperative (vertical axis) and one-month postoperative (horizontal axis) visual acuities following neodymium:YAG laser capsulotomies. Note visual improvement in 91 % of eyes.
Fig 2. Mean intraocular pressures at all observed time intervals. Note the transient intraocular pressure increase which returns to normal by the !irst postoperative week.
informed consent. We treated 53 eyes of 52 patients. All patients were white. There were 32 women and 20 men. The mean age at treatment was 69 ± 11 years of age (range, 32-89 years). Three patients had had surgery for congenital cataracts between 30 and 576 months previously. The remaining patients had adult onset cataracts and were 26 ± 17 months (range, 3-106 months) postoperative. Twenty-eight (54%) had planned extracapsular cataract surgery (nuclear expression), 22 (42%) had phacoemulsification, and two (4%) had unplanned extracapsular cataract extraction (attempted intracapsular cataract surgery). Thirty-six (68%) eyes had posterior chamber lenses, four (7%) had anterior chamber intraocular lenses, and one (2%) had an iris fixated lens. Twelve (23%) eyes did not have an intraocular lens. . All capsulotomies were done using the Storz 1040 Q-switched Nd:Y AG laser with a single helium neon aiming beam without a burst mode. All capsulotomies were attempted at energy levels of 0.9 to 1.0 mJ. If this was unsuccessful in adequately perforating the posterior capsule, energy was increased in O.2-mJ steps ' until an adequate response was noted. An Abraham YAG contact lens (Ocular Instruments, Bellvue Washington) was used in 8 (15%) eyes. Forty-two (79%) eyes were done without dilation. The remaining 11 eyes were dilated with tropicamide 1 %prior to capsulotomy. All patients had comprehensive preoperative and follow-up ophthalmic evaluations including Snellen visual acuity, applanation tonometry, biomicroscopy, and fundus examination (when possible). All eyes were examined at the following postoperative time intervals: two hours, one week, and one month. The first 31 treated eyes were also examined at two-hour intervals for the first eight postoperative hours. No patients were routinely treated with corticosteroids or lOP lowering medications. Six patients did have medically controlled open-angle glaucoma prior to study entry. If a postoperative lOP
greater than 30 mmHg was detected in any eye of the last 22 treated patients, therapy with timolol maleate 0.5% and acetazolamide 250 mg was instituted. These eyes with lOP elevations were then examined two hours later. All values are expressed as the mean ± one standard deviation. Statistical analysis was conducted using the Student's t-test and chi-squared analysis. P values of less than 0.05 were considered significant.
RESULTS The energy settings required to perform an adequate capsulotomy ranged from 0.9 to 3.2 mJ. The distribution was as follows: 0.9 mJ, 16 (30%) eyes; 1.0 to 1.2 mJ, 16 (30%) eyes; 1.3 to 1.6 mJ, 15 (28%) eyes; 1.8 to 2.2 mJ, 5 (9%) eyes; and 2.4 to 3.2 mJ, 2 (3%) eyes. The mean total energy delivered (the total number of pulses at each power setting) was 83 ± 76 mJ (range, 6.4-400 mJ). The initial Snellen visual acuity ranged from 6/7.5 to light perception with a mean of 6/24 ± 3 lines. The onemonth postoperative visual acuity ranged from 6/6 to count fingers (mean, 6/12 ± 3 Snellen lines). The distribution of preoperative and postoperative visual acuities can be seen in Figure 1. Thirty (57%) eyes improved at least 3 lines of visual acuity while only 2 (4%) eyes lost 1 line. The mean initial intraocular pressure (lOP) was 17 ± 3 mmHg (range, 4-24 mmHg). The mean lOPs during the first eight postoperative hours are seen in Figure 2. In Figure 3 we find that during the first eight postoperative hours 24 (77%) eyes had some immediate postoperative lOP elevation and 5 (16%) eyes had an lOP elevation of at least 20 mmHg over the preoperative level. Fifteen (48%) eyes had lOPs greater than 21 mmHg and 3 (10%) had lOPs greater than 30 at the eighth postoperative hour. Of the eyes followed at twohour intervals for eight hours after therapy, the largest 361
OPHTHALMOLOGY
•
MARCH 1985
Greatest Net tOP Change Within 8 Hours After YAG Copsulotomy
14 12 10
~ 8
ILl
'0
d z 6
4 2 0
>30
>20
>/0 lOP Change (mm Hg)
~O
<0
Fig 3. Greatest net intraocular pressure change seen in the first 31 treated eyes during the first eight postoperative hours. Note that onethird of treated eyes demonstrate an intraocular pressure increase of at least 10 mmHg over the preoperative measurements.
net change in lOP was seen at two hours in 14 (45%) eyes, four hours in 5 (16%) eyes, six hours in 6 (19%) eyes and eight hours in 6 (19%) eyes. The lOP elevation did not correlate with the amount of inflammation, number of pulses, iris bleeding, or total energy delivered. One factor that did correlate with lOP elevation was the presence of preexisting glaucoma. Two of the three patients with ·IOPs greater than 31 mmHg at the eighth postoperative hour had preexisting glaucoma. Five (9%) eyes had iris bleeding resulting in a less than 5% hyphema. These occurred in eyes without posterior chamber lenses or where posterior synechiae were present. The iris bleeding occurred at the sites of irido-capsular adhesion. The laser energy did not directly hit these sites. Intraocular lens markings occurred in 15/20 (80%) posterior chamber lenses in the first 31 patients and in 10/17 (59%) in the remainder. These consisted of minor psterior surface pits. A rare deeper pit with a stellate dendritic fracture was seen with energy levels greater than 2.0 mJ. There were no signs of damage to the corneal endothelium or retina.
DISCUSSION Our short-term prospective study demonstrates the effectiveness of the Q-switched Nd:YAG laser in restoring visual acuity in eyes with opacified posterior capsules. This was done in all eyes without the necessity of intraocular surgical intervention with a mean energy setting of 1.3 mJ per pulse. Indeed, 89% of our patients needed less than 1.7 mJ per pulse to create a satisfactory capsular opening. Laser therapy did not decrease the visual acuity in any eye. In only five eyes (9%), visual acuity was not improved or worsened slightly after laser 362
•
VOLUME 92
•
NUMBER 3
capsulotomy. In all cases, this was related to preexisting retinal pathology. As our study was designed to examine short-term complications, we cannot comment on the incidence of chronic problems, such as retinal detachment or cystoid macular edema following laser capsulotomy. A frequent short-term complication was a transient immediate postoperative lOP elevation. Three-quarters of our patients experienced some immediate lOP elevation, one-third had an lOP elevation greater than 10 mmHg and onesixth had an lOP elevation greater than 20 mmHg. This incidence and distribution of postoperative lOP spikes is similar to that reported for other procedures involving laser applications to the anterior segment (ie. laser iridotomy,8,9 and argon laser trabeculoplasty. 10,1 I This type of postoperative lOP elevation does not, therefore, appear to be specific to the Nd: Y AG laser or posterior capsular surgery. This lOP elevation in laser capsulotomy, laser trabecular surgery, and laser iridotomy does not appear related to particulate debris, gross anterior segment inflammation, or bleeding. Our work was not designed to evaluate the mechanism of this lOP rise, but has documented the frequency and degree of its occurrence. Further work is presently underway in both humans and nonhuman primates which may determine the pathogenic mechanism of this complication. The clinical significance of this lOP elevation is uncertain. If significant glaucomatous damage has previously occurred, one might expect to find either increased optic nerve cupping or visual field loss. We were unable to evaluate these parameters (because of hazey preoperative media) in most eyes. Transient lOP elevations 20 mmHg over baseline could certainly cause detectable damage in glaucomatous patients with advanced optic neuropathy. Since this lOP elevation is more common in glaucomatous eyes, one should use this procedure with caution in these eyes and follow their lOPs carefully in the immediate postoperative period. It also appears prudent to evaluate all patients' lOPs at least once, two hours following capsulotomy, so that appropriate therapy, if necessary, can be initiated. Iris bleeding was associated with Nd: YAG laser capsulotomy in 9% of treated eyes. This was not due to direct laser contact in any eye. This bleeding may be due to the Nd:YAG lasers shock wave disrupting adjacent iris blood vessels in areas of iridocapsularadhesion. Although this did not appear to be a severe problem, it might be advisable to use the minimal effective energy, avoiding unnecessarily large shock waves. Pitting or fracturing of implants was seen in 81 % of eyes with posterior chamber lenses. This complication's high incidence appears due, in part,to the novelty of this procedure. Implant pitting was inversely related to the surgeon's experience with this technique. Perhaps this could be partially attributed to the Storz laser's fundamental mode and its relatively crude aiming system. It is important that we detected no apparent retinal or corneal damage from Nd:YAG laser capsulotomy. Although the potential for these complications exists,
FLOHR, et al
•
LASER CAPSULOTOMIES
careful focussing and the use of low energy pulses l2 appears to eliminate these problems. We have made no comparisons between surgical and Nd:YAG laser capsulotomy. The primary advantage of laser capsulotomy is the elimination of endophthalmitis, a rare complication following surgical capsulotomy. The rate of visual recovery and the complications of lOP elevation, iris bleeding, and intraocular lens markings might be similar with surgical capsulotomy. A prospective randomized comparison of surgical and Nd:YAG laser capsulotomy is necessary to establish the relative safety and advantages of each technique.
REFERENCES 1. Cowan A, McDonald R. After-cataract. Arch Ophthalmol 1939; 22: 1074-8. 2. Binkhorst CD. Five hundred planned extracapsular extractions with irido-capsular and iris clip lens implantation in senile cataract. Ophthalmic Surg 1977; 8(3):37-44. 3. Sinskey RM, Cain W Jr. The posterior capsule and phacoemulsification. Am Intraocullmplant Soc J 1978; 4:206-7.
4. Kraft MC, Sanders DR, Lieberman HL. Total cataract extraction through a 3-mm incision: a report of 650 cases. Ophthalmic Surg 1979; 10(2):46-54. 5. Kratz RP. Results of phacoemulsification by Kelman and Girard techniques. In: Symposium on Cataracts; Transactions of the New Orleans Academy of Ophthalmology. St Louis: CV Mosby, 1979; 196-200. 6. Terry AC, Stark WJ, Maumenee AE, Fagadau W. Neodymium-YAG laser for posterior capsulotomy. Am J OphthalmoI1983; 96:716-20. 7. Vine AK. Ocular hypertension following Nd:YAG laser capsulotomy: a potentially blinding complication. Ophthalmic Surg 1984; 15:283-4. 8. Robin AL, Pollack IP. A comparison of neodymium:YAG and argon laser iridotomies. Ophthalmology 1984; 91:1011-6. 9. Cohen B, Krupin T, Stone RA, et al. Initial intraocular pressure response to argon laser iridectomy. ARVO Abstracts. Invest Ophthalmol Vis Sci 1984; 25(Suppl):44. 10. Weinreb RN, Ruderman J, Juster R, Zweig K. Immediate intraocular pressure response to argon laser trabeculoplasty. Am J Ophthalmol 1983; 95:279-86. 11. Hotchkiss ML, Robin AL, Pollack IP, Quigley HA. Nonsteroidal antiinflammatory agents after argon laser trabeculoplasty; a trial with flurbiprofen and indomethacin. Ophthalmology 1984; 91 :969-74. 12. Martin NF, Gaasterland DE, Cummins CE, et al. Damage thresholds for retrocorneal NdjY AG pulses. ARVO Abstracts. Invest Ophthalmol Vis Sci 1984; 25(Suppl):330.
363
Abstract: A prospective evaluation was conducted of Q-switched neodymium: YAG laser capsulotomy in 53 eyes followed for one postoperative month. The first 31 eyes were seen at two-hour intervals for the first eight hours, and the remaining eyes were checked only at the second postoperative hour during that day. Eighty-nine percent of eyes required a pulse setting of less than 1.7 mJ to successfully penetrate the posterior capsule. Visual acuity was improved in 91 % of eyes. A transient immediate postoperative intraocular pressure (lOP) elevation was seen in over 75% of treated eyes, and one-third had an lOP elevation greater than 10 mmHg over the preoperative lOP. This elevation was most common in glaucomatous eyes and occurred in almost one-half of the treated eyes by the second postoperative hour. This lOP change did not correlate with the degree of inflammation, bleeding , anterior chamber debris, or total energy delivered. Minimal iris bleeding occurred in 9% of treated eyes and was associated with iridocapsular adhesions. Eighty-one percent of eyes with posterior chamber implants developed some degree of lens damage. [Key words: cataract, capsulotomy, glaucoma, hyphema, intraocular lens, neodymium:YAG laser.] Ophthalmology 92:360-363, 1985
The increasing trend towards extracapsular cataract extraction is well established. A 25 to 50% rate of significant posterior capsule opacification following this procedure has been reported. 1- 5 Until recently, intraocular surgery was the only available method of opening an opacified posterior capsule to restore vision. Because of the intraocular nature of this procedure, it is associated with rare complications such as endophthalmitis. The neodymium (Nd):Y AG laser presents an alternative method of performing a posterior capsulotomy without opening the eye, therefore eliminating some of these
complications. However, the short- and long-term effects of laser surgery are only now beginning to be explored. Recent reports have demonstrated a significant incidence of immediate postoperative intraocular pressure (lOP) elevation following Nd:YAG posterior capsulotomy.6-7 Confirmation and further analysis of the incidence, rate of onset, duration, and severity of these complications is warranted. Therefore, we conducted a prospective analysis of patients undergoing Nd:YAG laser posterior capsulotomies and report our short-term results.
MATERIALS AND METHODS From the Departments of Ophthalmology, Greater Baltimore Medical Center; and the Glaucoma Service, Wilmer Institute, Johns Hopkins Hospital, Baltimore. Reprint requests to Alan L. Robin, MD, the Wilmer Institute, Maumenee Building Room B·117, The Johns Hopkins Hospital, 600 N. Wolfe St., Baltimore, MD 21205.
360
The criteria for entry into our study was decreased visual acuity or visual symptoms due to posterior capsular opacification, or wrinkling in patients following extracapsular cataract extraction. All patients were aware of the investigational nature of this technique and gave
FLOHR, el aI
•
LASER CAPSULOTOMIES
Mean Intraocular Pressure After YAG Capsulotomy
A Comparison of Preoperative and Postoperotive Visual Acuities
•
hand mo,ions counl finoers
6/120 6/60
•
6/30
•
6/24
6/21
.~ "0 a;
"o
d:"
6/18 6115
•
•
•
•
•
'lit
"" • • •
••
.
•••
•
26
• •
24
•
6/12 6/9
c;. 22 I
E E a. 20 Q
~r......"n.53
18
6/7.5 6/6
16
L -_ _ _ _L-____L-____~____~~,~~~/~
PreOp
2 hrs
4hrs
6hrs Time
8hrs
Iwk
lmon
Fig 1. Preoperative (vertical axis) and one-month postoperative (horizontal axis) visual acuities following neodymium:YAG laser capsulotomies. Note visual improvement in 91 % of eyes.
Fig 2. Mean intraocular pressures at all observed time intervals. Note the transient intraocular pressure increase which returns to normal by the !irst postoperative week.
informed consent. We treated 53 eyes of 52 patients. All patients were white. There were 32 women and 20 men. The mean age at treatment was 69 ± 11 years of age (range, 32-89 years). Three patients had had surgery for congenital cataracts between 30 and 576 months previously. The remaining patients had adult onset cataracts and were 26 ± 17 months (range, 3-106 months) postoperative. Twenty-eight (54%) had planned extracapsular cataract surgery (nuclear expression), 22 (42%) had phacoemulsification, and two (4%) had unplanned extracapsular cataract extraction (attempted intracapsular cataract surgery). Thirty-six (68%) eyes had posterior chamber lenses, four (7%) had anterior chamber intraocular lenses, and one (2%) had an iris fixated lens. Twelve (23%) eyes did not have an intraocular lens. . All capsulotomies were done using the Storz 1040 Q-switched Nd:Y AG laser with a single helium neon aiming beam without a burst mode. All capsulotomies were attempted at energy levels of 0.9 to 1.0 mJ. If this was unsuccessful in adequately perforating the posterior capsule, energy was increased in O.2-mJ steps ' until an adequate response was noted. An Abraham YAG contact lens (Ocular Instruments, Bellvue Washington) was used in 8 (15%) eyes. Forty-two (79%) eyes were done without dilation. The remaining 11 eyes were dilated with tropicamide 1 %prior to capsulotomy. All patients had comprehensive preoperative and follow-up ophthalmic evaluations including Snellen visual acuity, applanation tonometry, biomicroscopy, and fundus examination (when possible). All eyes were examined at the following postoperative time intervals: two hours, one week, and one month. The first 31 treated eyes were also examined at two-hour intervals for the first eight postoperative hours. No patients were routinely treated with corticosteroids or lOP lowering medications. Six patients did have medically controlled open-angle glaucoma prior to study entry. If a postoperative lOP
greater than 30 mmHg was detected in any eye of the last 22 treated patients, therapy with timolol maleate 0.5% and acetazolamide 250 mg was instituted. These eyes with lOP elevations were then examined two hours later. All values are expressed as the mean ± one standard deviation. Statistical analysis was conducted using the Student's t-test and chi-squared analysis. P values of less than 0.05 were considered significant.
RESULTS The energy settings required to perform an adequate capsulotomy ranged from 0.9 to 3.2 mJ. The distribution was as follows: 0.9 mJ, 16 (30%) eyes; 1.0 to 1.2 mJ, 16 (30%) eyes; 1.3 to 1.6 mJ, 15 (28%) eyes; 1.8 to 2.2 mJ, 5 (9%) eyes; and 2.4 to 3.2 mJ, 2 (3%) eyes. The mean total energy delivered (the total number of pulses at each power setting) was 83 ± 76 mJ (range, 6.4-400 mJ). The initial Snellen visual acuity ranged from 6/7.5 to light perception with a mean of 6/24 ± 3 lines. The onemonth postoperative visual acuity ranged from 6/6 to count fingers (mean, 6/12 ± 3 Snellen lines). The distribution of preoperative and postoperative visual acuities can be seen in Figure 1. Thirty (57%) eyes improved at least 3 lines of visual acuity while only 2 (4%) eyes lost 1 line. The mean initial intraocular pressure (lOP) was 17 ± 3 mmHg (range, 4-24 mmHg). The mean lOPs during the first eight postoperative hours are seen in Figure 2. In Figure 3 we find that during the first eight postoperative hours 24 (77%) eyes had some immediate postoperative lOP elevation and 5 (16%) eyes had an lOP elevation of at least 20 mmHg over the preoperative level. Fifteen (48%) eyes had lOPs greater than 21 mmHg and 3 (10%) had lOPs greater than 30 at the eighth postoperative hour. Of the eyes followed at twohour intervals for eight hours after therapy, the largest 361
OPHTHALMOLOGY
•
MARCH 1985
Greatest Net tOP Change Within 8 Hours After YAG Copsulotomy
14 12 10
~ 8
ILl
'0
d z 6
4 2 0
>30
>20
>/0 lOP Change (mm Hg)
~O
<0
Fig 3. Greatest net intraocular pressure change seen in the first 31 treated eyes during the first eight postoperative hours. Note that onethird of treated eyes demonstrate an intraocular pressure increase of at least 10 mmHg over the preoperative measurements.
net change in lOP was seen at two hours in 14 (45%) eyes, four hours in 5 (16%) eyes, six hours in 6 (19%) eyes and eight hours in 6 (19%) eyes. The lOP elevation did not correlate with the amount of inflammation, number of pulses, iris bleeding, or total energy delivered. One factor that did correlate with lOP elevation was the presence of preexisting glaucoma. Two of the three patients with ·IOPs greater than 31 mmHg at the eighth postoperative hour had preexisting glaucoma. Five (9%) eyes had iris bleeding resulting in a less than 5% hyphema. These occurred in eyes without posterior chamber lenses or where posterior synechiae were present. The iris bleeding occurred at the sites of irido-capsular adhesion. The laser energy did not directly hit these sites. Intraocular lens markings occurred in 15/20 (80%) posterior chamber lenses in the first 31 patients and in 10/17 (59%) in the remainder. These consisted of minor psterior surface pits. A rare deeper pit with a stellate dendritic fracture was seen with energy levels greater than 2.0 mJ. There were no signs of damage to the corneal endothelium or retina.
DISCUSSION Our short-term prospective study demonstrates the effectiveness of the Q-switched Nd:YAG laser in restoring visual acuity in eyes with opacified posterior capsules. This was done in all eyes without the necessity of intraocular surgical intervention with a mean energy setting of 1.3 mJ per pulse. Indeed, 89% of our patients needed less than 1.7 mJ per pulse to create a satisfactory capsular opening. Laser therapy did not decrease the visual acuity in any eye. In only five eyes (9%), visual acuity was not improved or worsened slightly after laser 362
•
VOLUME 92
•
NUMBER 3
capsulotomy. In all cases, this was related to preexisting retinal pathology. As our study was designed to examine short-term complications, we cannot comment on the incidence of chronic problems, such as retinal detachment or cystoid macular edema following laser capsulotomy. A frequent short-term complication was a transient immediate postoperative lOP elevation. Three-quarters of our patients experienced some immediate lOP elevation, one-third had an lOP elevation greater than 10 mmHg and onesixth had an lOP elevation greater than 20 mmHg. This incidence and distribution of postoperative lOP spikes is similar to that reported for other procedures involving laser applications to the anterior segment (ie. laser iridotomy,8,9 and argon laser trabeculoplasty. 10,1 I This type of postoperative lOP elevation does not, therefore, appear to be specific to the Nd: Y AG laser or posterior capsular surgery. This lOP elevation in laser capsulotomy, laser trabecular surgery, and laser iridotomy does not appear related to particulate debris, gross anterior segment inflammation, or bleeding. Our work was not designed to evaluate the mechanism of this lOP rise, but has documented the frequency and degree of its occurrence. Further work is presently underway in both humans and nonhuman primates which may determine the pathogenic mechanism of this complication. The clinical significance of this lOP elevation is uncertain. If significant glaucomatous damage has previously occurred, one might expect to find either increased optic nerve cupping or visual field loss. We were unable to evaluate these parameters (because of hazey preoperative media) in most eyes. Transient lOP elevations 20 mmHg over baseline could certainly cause detectable damage in glaucomatous patients with advanced optic neuropathy. Since this lOP elevation is more common in glaucomatous eyes, one should use this procedure with caution in these eyes and follow their lOPs carefully in the immediate postoperative period. It also appears prudent to evaluate all patients' lOPs at least once, two hours following capsulotomy, so that appropriate therapy, if necessary, can be initiated. Iris bleeding was associated with Nd: YAG laser capsulotomy in 9% of treated eyes. This was not due to direct laser contact in any eye. This bleeding may be due to the Nd:YAG lasers shock wave disrupting adjacent iris blood vessels in areas of iridocapsularadhesion. Although this did not appear to be a severe problem, it might be advisable to use the minimal effective energy, avoiding unnecessarily large shock waves. Pitting or fracturing of implants was seen in 81 % of eyes with posterior chamber lenses. This complication's high incidence appears due, in part,to the novelty of this procedure. Implant pitting was inversely related to the surgeon's experience with this technique. Perhaps this could be partially attributed to the Storz laser's fundamental mode and its relatively crude aiming system. It is important that we detected no apparent retinal or corneal damage from Nd:YAG laser capsulotomy. Although the potential for these complications exists,
FLOHR, et al
•
LASER CAPSULOTOMIES
careful focussing and the use of low energy pulses l2 appears to eliminate these problems. We have made no comparisons between surgical and Nd:YAG laser capsulotomy. The primary advantage of laser capsulotomy is the elimination of endophthalmitis, a rare complication following surgical capsulotomy. The rate of visual recovery and the complications of lOP elevation, iris bleeding, and intraocular lens markings might be similar with surgical capsulotomy. A prospective randomized comparison of surgical and Nd:YAG laser capsulotomy is necessary to establish the relative safety and advantages of each technique.
REFERENCES 1. Cowan A, McDonald R. After-cataract. Arch Ophthalmol 1939; 22: 1074-8. 2. Binkhorst CD. Five hundred planned extracapsular extractions with irido-capsular and iris clip lens implantation in senile cataract. Ophthalmic Surg 1977; 8(3):37-44. 3. Sinskey RM, Cain W Jr. The posterior capsule and phacoemulsification. Am Intraocullmplant Soc J 1978; 4:206-7.
4. Kraft MC, Sanders DR, Lieberman HL. Total cataract extraction through a 3-mm incision: a report of 650 cases. Ophthalmic Surg 1979; 10(2):46-54. 5. Kratz RP. Results of phacoemulsification by Kelman and Girard techniques. In: Symposium on Cataracts; Transactions of the New Orleans Academy of Ophthalmology. St Louis: CV Mosby, 1979; 196-200. 6. Terry AC, Stark WJ, Maumenee AE, Fagadau W. Neodymium-YAG laser for posterior capsulotomy. Am J OphthalmoI1983; 96:716-20. 7. Vine AK. Ocular hypertension following Nd:YAG laser capsulotomy: a potentially blinding complication. Ophthalmic Surg 1984; 15:283-4. 8. Robin AL, Pollack IP. A comparison of neodymium:YAG and argon laser iridotomies. Ophthalmology 1984; 91:1011-6. 9. Cohen B, Krupin T, Stone RA, et al. Initial intraocular pressure response to argon laser iridectomy. ARVO Abstracts. Invest Ophthalmol Vis Sci 1984; 25(Suppl):44. 10. Weinreb RN, Ruderman J, Juster R, Zweig K. Immediate intraocular pressure response to argon laser trabeculoplasty. Am J Ophthalmol 1983; 95:279-86. 11. Hotchkiss ML, Robin AL, Pollack IP, Quigley HA. Nonsteroidal antiinflammatory agents after argon laser trabeculoplasty; a trial with flurbiprofen and indomethacin. Ophthalmology 1984; 91 :969-74. 12. Martin NF, Gaasterland DE, Cummins CE, et al. Damage thresholds for retrocorneal NdjY AG pulses. ARVO Abstracts. Invest Ophthalmol Vis Sci 1984; 25(Suppl):330.
363