Intraocular Pressure Changes After Nd:YAG Laser Application

SHORT REPORTS Intraocular Pressure Changes After Nd:YAG Laser Application AHMET H. BILGE, EROL YILDIRIM, GUNGOR SOBACI and AHMET ERGIN Goz Klinigi, Etlik, Ankara, Turkey

Intraocular pressure (lOP) changes after Nd:YAG laser applications were studied to determine the effect of prophylactic antiglaucoma therapy, and the causes of high lOPs. In this prospective study lOPs were measured at 1, 2, 3, 5, 24,48 hours and 1 week after Nd:YAG treatment in our out-patient clinic. In three patient groups, 181 eyes (111 capsulotomy and 70 iridotomy) matched for age and ocular status (aphakia, pseudophakia and iridotomies) were studied. The group which received no medication showed significant lOP elevations within the first 3 hours, and in all groups the aphakics had higher lOP levels than the pseudophakics. The lOP changes were lowest in the iridotomy cases. Variables such as pulse energy, number of pulses, and total energy used during the laser applications, or the differences in the pupillary diameter could not explain the increased lOP values recorded. In this study, antiglaucoma therapy, either with timolol or acetazolomide were found to be effective. Extensive peripheral anterior synechiae and released dense lens material were observed in the cases with lOPs over 20 mmHg. Keywords: Nd:YAG laser capsulotomy; Nd:YAG laser iridotomy; Tonography; Intraocular · pressure elevation; Timolol maleate; Acetazolamide INTRODUCTION

The Nd:YAG laser is an uninvasive instrument used for anterior segment treatment applications. Although it is widely used for :rltany treatments some complications have been reported. The cause of the most frequently seen complication, lOP elevation, has been reported to be the result of shock wave damage [1-6]. Other causes, such as the clogging of trabecular meshwork by released lens material [6Correspondence to: Dr Ahmet H. Bilge. Giilhane Tip Fakiiltesi, Goz Klinigi, Etlik, Ankara, Turkey. 0955-3681/92/020115+08 $03.00/0 © 1992 Bailliere Tindall

8], traveculitis and neovascular mechanisms [7], angle closure by swelling of iris root and ciliary body [5] and pupillary block [1, 9] have also been described. This study was designed to evaluate the reasons for lOP elevation and other changes in three different treatment groups undergoing Nd: YAG laser posterior capsulotomy and iridotomy. SUBJECTS AND METHODS

One hundred and eighty-one eyes of 146 adult patients undergoing Nd:YAG posterior capsulotomy and iridotomy at The Eye Clinic of Gulhane Faculty of Medicine, Ankara, were studied. Patients with lOPs out of the range of 10-20mmHg and those allergic to timolol and acetazolamide were not included, and no medication was given unless lOP was over 30 mmHg. Informed consents were obtained, and each patient was assigned to one of groups A, B or C to give a homogeneous distribution of the ocular status (aphakia, pseudophakia) and iridotomies (for therapeutic reasons in angle closure glaucoma cases and prophylactic reasons in the other eye). Capsulotomies were performed on pseudophakes with visual acuities of 20/100 to 20/400 within 2-22 months (mean 8 months) postoperatively. Group A included 65 eyes of 53 cases receiving no medication before or after the laser treatment. Group B included 60 eyes of 48 cases administered 250 mg acetazolamide orally 3 hours prior to the treatment, and group C included 56 eyes of 45 cases given timolol (0.5%) 5 and 30 minutes after the laser treatment. Gonioscopic, tonographic and routine examinations were performed; the amount of tyndalization and the peripheral anterior synechiae (PAS) were graded as + 1 to +4. A Q-Switched Nd:YAG (Visulas YAG) laser was used. The pulse energy, number of pulses, total energy applied, and the lOP changes 1, 2, 3, 5, 24,48 hours and 1 week after treatment were recorded as the mean ± SEM; the results were analysed by using the group and paired 't' -tests and multiple regression analysis; the value was 0.05. RESULTS

The mean age was 47.8 ± 1.9-age was not significantly different for the three groups: A (51 ± 3), B (49 ± 2) and C (43 ± 2). The age distribution in 46 Eur J Implant Ref Surg, Vol4, June 1992

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aphakic (53 ± 2 years), 65 pseudoaphakic (48 ± 3); and 35 therapeutic and 35 prophylactic iridotomy (41 ± 2 years) cases were also similar. All eyes except three have had improved vision; these three cases had cystoid macular oedema (CME). No correlation was found between the lOP elevation and variables used during the laser application (pulse energy, number of pulses, total energy) and the tonographic C values. In group A, higher lOP values were observed at 1, 2 and 3 hours (P < 0.01), but the C values were not in correlation. In all groups, the aphakics always had higher lOPs within the first 3 hours (P < 0.001) (Figs 1-3).

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Fig. 3 Change in mean intraocular pressure (lOP) elevation in group C

Slitlamp examination of the 18 patients with lOP levels over 30 mmHg, showed that 15 of them had both +4 tyndalization and extensive PAS formation along the chamber angle covering more than one quadrant; two had only PAS; and one had pseudophakic pupillary block.

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Fig. 1 Change in mean intraocular pressure (lOP) elevation in group A

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Since lOP elevation after Nd:YAG capsulotomy is a frequent and serious complication [8, 10, 11], in some cases leading to the loss of vision [8], prophylactic antiglaucoma therapy should be applied to prevent it. We observed that the lOP elevation in pseudophakic eyes was less than that in aphakic eyes, within the first 3 hours after the laser treatment. However, after 5 and 24 hours the pseudophakic eyes had higher lOP levels; the differences in the lOP elevations in both groups were not statistically significant. The lower lOP elevations in pseudophakic eyes can be explained by the barrier effect, and by the dampening of shock-wave damage by the IOL itself [7-12]. Richter et al. reported that lOP elevations in pseudophakics could be observed in later hours of the treatment [12]. Brown reported that 4% pilocarpine was sufficient to control the lOP elevations in Nd:YAG capsulotomy [13] and Richter et al. showed that timolol was more effective for this purpose [12]. In our study, pilocarpine was not used owing to its potential to increase the pupillary block in the aphakic patients without iridotomies. As previously reported [7, 9], no correlation was found between the post-treatment lOP elevations, and the number of pulses, the pulse energy applied Eur J Implant Ref Surg, Vol 4, June 1992

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Table 1 Groups included in the study Group A B

c

Sum

Age 51.1 49.2 47.7 49.3

± ± ± +

3 2 2 2

Number of eyes 65 60 56 181

Capsulotomies ECCE 17 15 14 46

ECCE +IOL 24 21 20 65

Iridotomies Therapeutic 12 12 11 35

Prophylactic 12 12 11 36

posterior capsule before and after the YAG Laser. Trans. or the patient's age. Pupillary dilation did not have Ophthalmol Soc. U.K., 1985; 104: 533-535. an effect on the lOP levels. 3 JD Jagger, J Marshall, AM Hamilton. Neodymium YAG With the exception of the three cases in group B Laser in ophthalmic practice principles and early experience. Trans. Ophthalmol. Soc. U.K., 1985; 104: 181-190. which had extensive PAS formation, in all groups F Kuata, T Krupin, S Sinclair, L Karp. Progressive glauco4 the iridotomies showed the fewest lOP changes. matous visual field loss after Neodymium-YAG Laser capsuReleased lens material caused more lOP elevations lotomy. Am. J. Ophthalmol., 1984; 98: 632-633. 5 CJ Macewen, GN Dutton, D Holding. Angle closure following than iris material. The results of the iridotomies Neodymium-YAG Laser capsulotomy in the aphakic Eye. Br. performed in aphakics (seven patients) supported J. Ophthalmol., 1985; 69: 795-796. this opinion, but this could not be confirmed by the 6 MD Parker, GS Clorfeine, RD Stocklin. Marked intraocular pressure rise following ND-YAG laser capsulotomy. Ophtonography. The large standard deviations observed thalmic Surg., 1984; 15: 103-104. during the measurements in both aphakics and 7 MC Kraff, DR Sanders, HL Lieberman. Intraocular pressure pseudophakics may be responsible for the uncorreand corneal endothelium after Neodymium-YAG Laser posterior capsulotomy: Relative effects of aphakia and pseudolated lOP changes within the 3 hours and the tonophakia. Arch. Ophthalmol., 1985; 103: 511-514. graphic C values. Also, the slightly decreased C 8 AK Vine. Ocular hypertension following Nd:YAG Laser capvalues of pseudophakic eyes at 5 and 24 hours was sulotomy: A potentially blinding complication. Ophthalmic Surg., 1984; 15: 283-284. not significant. 9 CJ Macewen, GN Dutton. Neodymium-YAG Laser in the In groups Band C, the lOP elevations (5 ± 0.4 and management of posterior capsular opacification-compli4 ± 0.2 mmHg) were less than that of group A (8 ± cations and current trends. Trans. Ophthalmol. Soc. U.K., 1986; 105:337-233. 1.3 mmHg) (P < 0.01). Of the 18 cases with lOPs MM Channell, H Beckman. Intraocular pressure changes 10 over 30 mmHg that needed the use of additional after Neodymium-YAG Laser posterior capsulotomy. Arch. antiglaucoma therapy, 11 were from group A. This Ophthalmol., 1984; 102: 1024-1026. indicates the necessity for prophylactic antiglau- 11 CU Richter, G Arzeno, HR Pappas et al. lnraocular pressure elevation following Nd:YAG Laser posterior capsulotomy. coma therapy, given either orally or topically in Ophthalmology, 1985; 92: 636-640. Nd:YAG applications. 12 CU Richter, G Arzeno, HR Pappas et al. Prevention of intraocular pressure elevation following Neodymium-YAG Laser No significant correlation existed between the Posterior Capsulotomy. Arch. Ophthalmol., 1985; 103: 912PAS and severity of anterior segment inflammation 915. and the increase in lOP. No angle closure or pupill- 13 SVL Brown, JV Thomas, DC Belcher et al. Effect of pilocarpine in treatment of intraocular pressure elevation following ary block due to the laser treatment was observed, Neodymium YAG-Laser posterior capsulotomy: Relative except for one pseudophakic pupillary block with effects of aphakia and pseudophakia. Arch. Ophthalmol., 1985; 103:511-514. liquefied vitreous protruding through normal capsulotomy hole. In this case, lOP exceeded over 50 mmHg and the patient did not respond to the Received September 1990 medical therapy; therefore, pars plana vitrectomy was performed to relieve the block. In conclusion, we believe that further ultrastructural studies should be conducted on the patients with extensive PAS formation and on the released lens material, to determine the pathophysiological causes of the elevated lOP levels observed after Nd:YAG laser applications.

REFERENCES 1 AD Aron-Rosa, JC Grieseman, JJ Aron. Use of a pulsed Neodymium YAG-Laser (Picosecond) to open the posterior lens capsule in traumatic cataract: a preliminary report. Ophthalmic Surg., 1981; 12: 496-499. 2 WS Harris, WK Herman, WR Fagadau. Management of the Eur J Implant Ref Surg, Vo/4, June 1992