86

abstracts Edited by C. William Simcoe, M.D.

Acta Ophthalmologica

Bergea B: Repeated argon laser trabeculoplasty. Acta Ophthalmol 64:246-250, 1986

Laser trabeculoplasty was repeated in 20 eyes of 18 patients with simple or capsular glaucoma in which a first full-circumference argon laser trabeculoplasty resulted in early or late failure. In 12 eyes the second trabeculoplasty was clinically successful. At an aver­age follow-up time of 30 months after second trabeculoplasty, the treatment was still successful in six patients. Early failure after the first treatment seems to be unfavorable for the outcome of second­ary treatment. No correlation was found between the accumulated dose of laser energy delivered into the trabecular meshwork and the degree of in traocu­lar pressure reduction after the second trabeculo­plasty in this retrospective study.

Rouhiainen H, Tedisvirta M: The laser power needed for optimum results in argon laser tra­beculoplasty. Acta Ophthalmol 64:254-257, 1986

Ninety-five successive argon laser trabeculoplasties to as many patients were followed six to 18 (mean eight) months. Forty-eight eyes had capsular glau­coma and 35 simple glaucoma. The power used ranged from 100 m W to 1,000 m Wand the total energy from 1.0 J to 5.0 J. The success rates between groups were tested with a X2 test. With laser power of more than 500 m Wand energy level more than 3.0 J, the success rates were maximal (77% and 75%). It is somewhat surprising that it does not seem important whether there is a visible bubble effect in the anterior chamber angle. This might be due to the fact that whenever energy is delivered to the pigmented trabecular band a destruction in the tissue, leading to scar formation, occurs.

Naeser K, Thim K, Hansen TE, Degn T, et al: Intraocular pressure in the first days after implanta­tion of posterior chamber lenses with the use of sodium hyaluronate (Healon®). Acta Ophthalmol 64:330-337, 1986

Intraocular pressure (lOP) was measured before and 6, 24, 48 and 72 hours after extracapsular cataract extraction with implantation of a posterior chamber lens in three groups of patients. In group I (30 patients), sodium hyaluronate (Healon®) was used during anterior capsulotomy and lens implantation and was aspirated at the end of surgery. In group II (22 patients), Healon® was used as in Group I with 500 mg acetazolamide at the end of surgery. In group III (17 patients), balanced salt solution and/or air was used instead of Healon® during surgery. In all groups, statistically significant rises in lOP after six hours were followed by significant falls in the

J CATARACT REFRACT SURG-VOL 13, JANUARY 1987

remaining postoperative period. The rise and subse­quent fall in lOP was significantly greater in group I than in group III. Acetazolamide in group II 'did not prevent excessive rises in lOP. Aspiration probably shortens the period of Healon®-induced hyperten­sion. The authors recommend a meticulous aspira­tion of Healon® at the end of surgery. It appears that postoperative iritis was more prevalent in patients treated with Healon®. This may have been caused by degradation products of Healon® still present in the anterior chamber.

Krause U, Alanko HI: Dislocated intraocular lens after biodegradation of fixation loops; a case report. Acta Ophthalmol 64:338-343, 1986

A three-year-old boy had a Worst Medallion intra­ocular lens with loops made of 6.0 nylon implanted in his right eye after aspiration of a traumatic cataract. Postoperatively, the eye was irritated and showed increased tendency to secondary membrane formation. The patient was lost to follow-up three months postoperatively. He returned five years later because of four days of pain and redness in his right eye. On examination, the optic part of the in traocu­lar lens was seen to lie free in the anterior chamber. The loops were broken near their insertions in the lens body. The distal ends of the broken loops could not be detected in the pupillary region. No traces of the iris fixation suture were seen. The lens was removed and subjected to scanning electron micros­copy, which revealed extensive biodegradative changes in three loop stumps, the fourth being totally dissolved. The young age of the patient and the chronic inflammation may have had an accelerat­ing effect on the nylon degradation. Children with eyes implanted with nylon loop lenses should re­main under regular ophthalmological control.

British Journal of Ophthalmology

Marshall J, Trokel S, Rothery S, Krueger RR: A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radia­tions from an excimer laser. Br ] Ophthalmol 70:482-501, 1986

This paper reviews the potential role of excimer lasers in corneal surgery. The morphology of inci­sions induced by two wavelengths of excimer laser radiation, 193 nm and 248 nm, are compared with the morphology of incisions produced by diamond and steel knives. Analysis suggests that ablation induced by excimer laser results from highly lo­calized photochemical reactions and that 193 nm is the optimal wavelength for surgery. The only signifi­cant complication of laser surgery is loss of endo-

thelial cells when incisions are within 40 J-lm of Descemet's membrane. Current observations based on the geometry and dimensions of the area of cell loss suggest that these cells are compromised by mechanical (shock or acoustic) waves dissipating their energy at an interface of mismatch of acoustic impedance. This concept is supported by the au­thors' observations that endothelial cell damage is greater at 248 nm and occurs at this wavelength when erosion depths are farther from Descemet's membrane than when troughs are created by 193 nm radiation. This finding is significant because at the longer wavelength more tissue is eroded per pulse and the resultant mechanical waves are larger. The authors do not consider the fluorescence induced by absorption of ultraviolet radiation within the abla­tion zone to have a significant role in endothelial cell loss.

Bulletin de la Societe BeIge D Ophtalmologie (Ghent)

Leys M, Dejong PTVM, Pameijer JH: Intra ocular pressure drop after Q-switched neodymium YAG laser posterior caps ulotomy. Bull Soc Beige Ophtalmol 213:119-126, 1986

A 50% intraocular pressure (lOP) rise two hours after a Nd:YAG laser capsulotomy has been de­scribed by many authors. It is considered to be due to the accumulation of debris in the trabecular meshwork. Also, prostaglandin-mediated changes in the blood-aqueous barrier might influence the lOP. This increase after two hours is reduced when prostaglandin inhibitors are given prior to the caps ulotomy. A tonographic examination before and two hours following capsulotomy showed that an lOP increase of 50% matches with a decrease of 50% of the outflow facility. The intraocular lens was found to have a protective effect on the pressure rise; this effect is best seen in the posterior chamber lenses but it might also exist for iridocapsular and anterior chamber lenses. The maximum lOP rise in the pseudophakic eye probably comes later than in the aphakic eye. Some authors postulate that the shock effect of the laser wave disturbs the trabecular function. Electron microscopic examination of the trabeculum failed to show any structural changes by indirect contusion. The normalization of the lOP two months after the discission could be the result of a normalization of the outflow facility. A tonographic study might be useful to prove it. In addition it might be due to a recovery of the trabecular meshwork from the functional disturbance by the shock wave, to restitution of the blood-aqueous

J CATARACT REFRACT SURG-VOL 13, JANUARY 1987 87

barrier, or to disappearance of prostaglandin (pre­cursors) and fibrin from the anterior chamber. The authors only speculate why the lOP became lower than the precapsulotomy values. It might be due to a rebound mechanism after the lOP rise or due to a destructive effect of the shock wave on the ciliary body epithelium. Unfortunately, the pressure of the fellow eye had not been taken before and after capsulotomy in all cases so the authors could not compare the treated with the untreated eyes. Simi­lar unexplained lOP lowering has been described after cataract extraction with and without lens implanation and after photocoagulation of diabetic eyes.

Fortschritte der Ophthalmologie (Munchen)

Schrems W, Haigis W, Zeuss R: The effect of YAG­laser posterior caps ulotomy on the corneal endo­thelium. Fortschr Ophthalmol 83:433-435, 1986 (in German)

In a prospective, clinical study, corneal endothelium cell density was measured by means of contact specular microscopy prior and 2, 4, and 12 weeks following Nd:YAG laser treatment. The Nd:YAG laser was used in Q-switched mode (nanosecond range) to perform post-cataract membrane dissec­tion in 24 eyes and posterior caps ulotomy in another 24 pseudophakic eyes (22 patients each). The mor­phometric study of the corneal endothelium re­vealed a variable increase of cell sizes, occasional cell loss, and an increase in polymorphism after Nd:YAG laser treatment. The slight decrease of endothelial cell density was statistically significant (P= 0.01) for the aphakic group and for the pseudophakic group.

Graefes Archive for Clinical and Experimental Ophthalmology

(Berlin)

Bleckmann H, Vogt R: Experimental endothelial lesions by means of an ultrasound phacoemulsificator. Graefes Arch Clin Exp Ophthalmol 224:457-462, 1986

This study deals with experimental use of an ultra­sound generator for phacoemulsification and its effect on bovine corneal endothelium. There was no corneal disease. The results demonstrated that the corneal endothelium was vulnerable to the effects of phacoemulsification, and duration of exposure as well as distance of the phacotip from the endo­thelium correlated with the extent of endothelial cell damage. The total volume of fluid was considerably more than the normal volume of aqueous humor in the anterior chamber. Although a slight increase in

temperature is theoretically possible in the present study, thermal damage to the endothelium was un­likely. Addition of sodium hyaluronate (Healon®) to the irrigation fluid clearly reduced endothelial cell defects when all other parameters remained un­changed. Although viscoelastic substances have been used primarily in the implantation of intraocu­lar lenses and though the value of hyaluronic acid has been demonstrated conclusively in experimental studies, the efficacy of these substances in irrigation fluid for protection of the endothelium has yet to be proven in clinical studies. As an alternative, Healon® might be introduced into the anterior chamber be­fore the operation. The substance would be removed to a certain extent by irrigation and aspiration, but a thin protective layer would still remain on the endo­thelium during the surgical procedure. Patients at high risk of corneal damage due to severely de­creased endothelial cell thickness or cornea guttata might benefit from prophylactic use of Healon® for prevention of irreversible corneal edema.

International Ophthalmology

Ngui MSH, Lim ASM, Chong AB: Posterior chamber intraocular lenses in diabetics; review of 63 patients. Int Ophthalmol 8:257-259, 1985

This is a study of 63 cases of posterior chamber intraocular lenses implanted in diabetics, with and without retinopathy, undertaken in 1984. Fifty­three (84%) of the 63 eyes obtained 20/40 or better visual acuity. Excluding pre-existing disease, 52 (95%) of 55 obtained 20/40 or better acuity. Argon laser therapy was performed postoperatively in 11 patients with no difficulties. These results are comparable to the visual results published for intraocular lens implantation in nondiabetics and in agreement with those previous studies. There were no specific surgical problems encountered and no major hindrance to photocoagulation. However, a longer follow-up is necessary. The study seems to demonstrate that diabetics need not be automat­ically excluded from receiving an intraocular im­plant and the benefits that come with it. However, surgeons inserting implants in diabetics should do so cautiously. They must review the retina regularly and be prepared to manage the retinopathy with photocoagulation if necessary.

Klinische Monatsblatter fur Augenheilkunde (Stuttgart)

Sponagel LD, Gloor B: Does implantation of posterior chamber lenses lower intraocular pressure? Klin Monatsbl Augenheilkd 188:495-499, 1986 (in German)

88 J CATARACT REFRACT SURG-VOL 13, JANUARY 1987

In a retrospective study, intraocular pressure (lOP) following extracapsular cataract extraction and pos­terior chamber lens implantation was analyzed. The population examined included a virtually random selection of 97 preoperatively normotensive cases from a total of 403 eyes on which a posterior chamber operation was performed in the authors' clinic in 1983. The entire population showed a statistically significant average lOP decrease of 1.95 mm Hg or 12.8% when compared with the preoperative pres­sure of 15.27 mm Hg for all sampling intervals except the last (547-728 days). The postoperative lOP differences among the individual time intervals

did not vary significantly from one to another. How­ever, the whole population as well as each popula­tion group showed a tendency to revert to increasing lOP in the later time intervals. The preoperative level influenced the postoperative behavior in that the higher the preoperative lOP, the greater the lOP drop immediately postoperatively; on the other hand, in cases of high initial lOP, the reversion to increasing lOP was more pronounced in the course of two years. Furthermore, diabetics and those suffering from hypertension also showed a tendency toward pronounced reversion of lOP, while sex and age seemed to have no influence on this parameter.

J CATARACT REFRACT SURG-VOL 13, JANUARY 1987 89