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Biomedical subjects

W Schrems

Publications and source records attributed to W Schrems.

At least 19 recordsLinked to original sources
PubMed1990

[Biometry of the anterior chamber of the eye in Nd:YAG laser iridectomy].

In a prospective clinical study covering 41 eyes (28 patients) with narrow-angle glaucoma the central and peripheral anterior chamber depths were determined biomicroscopically before and after Nd:YAG laser iridectomy. In 29 eyes the central anterior chamber depth was also measured by ultrasonography. In contrast to the increase in central anterior chamber depth, which was only slight, the increase in the peripheral anterior chamber depth was statistically significant (P less than 0.01).

Anterior Chamber↗
PubMed1987

Visual field improvement after neodymium: YAG laser puncture of miotic cysts.

This case report describes the use of a Q-switched neodymium:YAG laser to puncture miotic cysts. Fifteen shots of 0.06 mJ were needed. The pupil dilated more widely following this procedure, resulting in an improvement in the patient's visual field. Intraocular pressure (IOP) was not able to be controlled medically, however, and filtering surgery 20 days post laser treatment was required. IOP control had been poor prior to the laser-treatment, and did not appear to be more following treatment.

Adult↗
PubMed1986

[Fluorophotometry as a method for the detection of permeability changes in the blood and aqueous humor barrier].

The increase in permeability of the blood-aqueous barrier after Nd-YAG laser iridotomy and the protective effect of locally applied indomethacin were investigated in an experimental animal study using a computerized fluorophotometer. The permeability of the blood-aqueous barrier was evaluated by three different molecules: fluorescein-sodium (molecular weight 330), fluorescein-labeled dextran 70 000 (molecular weight 70 000) and fluorescein-labeled dextran 150 000 (molecular weight 150 000). The fluorescein concentration of the anterior chamber was measured in 36 eyes (18 rabbits) as well as in a control group of 9 eyes (9 rabbits) at fixed times after intravenous dye injection. Fluorescein leakage occurred, but no leakage of fluorescein-labeled dextrans was visible in the control group. Laser iridotomy induced a time-dependent increase in anterior segment permeability to fluorescein and fluorescein-labeled dextrans. Disturbance of the blood-aqueous barrier was effectively reduced by topical pretreatment with indomethacin, which mainly inhibited the leakage of the fluorescein-labeled dextrans. The clinical relevance of the laser-induced breakdown of the blood-aqueous barrier and the protective effect of a prophylactic pharmacotherapy are discussed.

Animals↗
PubMed1986

[Effect of neodymium YAG laser treatment of glaucoma on endothelial cell density of the cornea].

In a prospective clinical study corneal endothelium cell density was measured by means of contact specular microscopy prior to and 2, 4 and 12 weeks after Nd-YAG laser treatment. Two different laser techniques were applied: 19 eyes with narrow-angle glaucoma were treated by laser iridotomy, 21 eyes with open-angle glaucoma underwent laser treatment of the trabecular meshwork. The Nd-YAG laser was driven in Q-switched mode (nanosecond range) for iridotomy and in free-running mode (millisecond range) to treat the trabecular meshwork. A mechanical effect (iridotomy) as well as a thermal effect (LTP) of the Nd-YAG laser source was used. The morphometric study of the corneal endothelium revealed a variable increase in cell size, occasional cell loss, and an increase in polymorphism after Nd-YAG laser treatment. The decrease in endothelial cell density was not statistically significant (p = 0.01) for either laser technique. Possible mechanisms and risk factors responsible for endothelial cell loss are discussed.

Cell Count↗
PubMed1986

[Is YAG laser iridotomy suitable for the prevention of glaucoma attacks?].

In a prospective clinical trial comprising 41 eyes with narrow-angle glaucoma, the patency of YAG laser iridotomy was checked using a rapidly-acting parasympatholytic drug. YAG laser iridotomy was performed after an acute attack of angle-closure glaucoma, in either the affected or the fellow eye. Tropicamide mydriasis had no effect on IOP either in the patient group or in the control group of ten normotensive eyes.

Glaucoma↗
PubMed1985

The effect of topically applied prostaglandin inhibitors on the laser-induced disruption of the blood aqueous barrier.

The therapeutic effect of topically applied prostaglandin inhibitors on the laser-induced disruption of the blood-aqueous barrier was investigated in six series of five rabbits each. One series was not coagulated and served as baseline, and in a reference group laser coagulation was performed without pretreatment with a prostaglandin inhibitor. In four series the iris laser coagulation of the left eyes was preceded by topical application of a prostaglandin inhibitor. The right eyes served as controls for the contralateral effect on the blood aqueous barrier. After laser coagulation the intraocular pressure was monitored at 10-min intervals, and the anterior chamber was tapped for analysis of the protein concentration and the lactate dehydrogenase activity. Pretreatment with dexamethasone eyedrops and indomethacin eyedrops markedly blocked the laser-induced disruption of the blood-aqueous barrier. The level of protein concentration in the aqueous humor after laser coagulation was much less after pretreatment with dexamethasone or indomethacin eyedrops. The effect was significant, both for the laser-treated eyes and for the noncoagulated fellow eyes (p less than 0.025). The subconjunctival pretreatment with dexamethasone 1 or 24 h before laser coagulation had no significant effect with respect to the protection of the blood aqueous barrier.

Animals↗
PubMed1985

[Collapse of the blood-aqueous humor barrier following laser injury--preventive pharmacotherapy with prostaglandin inhibitors].

Laser-induced collapse of the blood-aqueous barrier and the protective effect of different prostaglandin inhibitors were investigated in the animal study reported here. As a parameter of the barrier function, the protein concentration in the aqueous humor was measured using a micromethod. The anterior chamber of 90 eyes (45 rabbits) was tapped only once, 100 min after the laser procedure. The results prove that different prostaglandin inhibitors in a systemic or topical application form can effectively reduce disturbances of the blood-aqueous barrier after laser surgery. This is also of clinical relevance with regard to laser iridotomy or trabeculoplasty in glaucoma.

Animals↗
PubMed1985

[Increase in the intraocular pressure in postcataract surgery using a neodymium YAG laser].

In a prospective clinical study 54 postcataract membrane dissections (51 patients) were performed using a Q-switch Nd-YAG laser. Under standardized conditions all patients were pretreated with prostaglandin inhibitors and received topical steroids and beta-blockers in low concentrations, as well as carbonic anhydrase inhibitors orally. The changes in visual acuity and the response of IOP to total energy input were analyzed. There was no statistically significant correlation between postoperative rise in IOP and total energy input. The clinical relevance of the results is discussed.

Adult↗
PubMed1985

[Demonstration of the tonographic effect in YAG laser trabeculoplasty in chronic glaucoma].

In a pilot study comprising 16 eyes of 16 patients with chronic open-angle glaucoma the tonographic outflow facility was examined before and after Nd-YAG laser treatment of the trabecular meshwork. For evaluation of the facility effect of laser trabeculoplasty, the tonographic record between the third and seventh minute according to the tonography test of Leydhecker was used. An improvement in outflow facility was established which correlated with the postoperative fall in IOP.

Follow-Up Studies↗
PubMed1984

The effect of YAG laser iridotomy on the blood aqueous barrier in the rabbit.

The effect of YAG laser iridotomy on the blood aqueous barrier in the rabbit was investigated in 21 eyes. In seven series, each containing three pigmented rabbits, the right eye received a YAG laser iridotomy in the upper nasal quadrant of the peripheral iris under standardized conditions utilizing the Mikroruptor II (Lasag Company, Thun/Switzerland). One of the parameters describing the blood aqueous barrier effects was the intraocular pressure, which was monitored at 10 min intervals. The iridotomy caused significant pressure increases in the treated eyes which was maintained up to 90 min following the laser procedure. The measurement of the protein concentration and the lactate dehydrogenase activity was done at equal time intervals after the iridotomy, on the basis of anterior chamber tapping of the treated eyes and the untreated control eyes. Over a period of 100 min after laser surgery, a positive correlation between time and protein concentration for the treated eyes (r = + 0.86) could be established. The activity of the enzyme lactate dehydrogenase in the treated eyes was increased within 5 min of the trauma, reaching a maximum 45 min after surgery, and the increase in activity level remained 150 min after surgery. The results indicate that the disturbance of the blood aqueous barrier with the YAG laser is not essentially different from that of the argon laser, although tissue damage may be more pronounced.

Animals↗
PubMed1984

[Drug therapy of chronic glaucoma with pilocarpine gel].

In an open clinical trial including 19 patients with chronic open-angle glaucoma, the efficacy, duration of action and tolerance of pilocarpine gel were investigated over a treatment period of a 4 weeks on the basis of one application once a day. The vehicle of pilocarpine gel is a highly viscous, cross-linked, hydrophilic polyacrylic acid which renders prolonged release of pilocarpine hydrochloride 4%, and for this reason insures a prolonged duration of action. After single-dose application pilocarpine gel caused a significant lowering of IOP over at least 18 hours, with a relative potency in the range of 23% of 31% on the first day of treatment, and between 13% and 25% on the 29th day of treatment. As the time interval following the preceding pilocarpine-gel application increased, there was a slight but significant rise in the treated pressure level, although therapeutic pressure levels were not exceeded. In the course of the 4 weeks of treatment, there was a small but significant decrease in response, which can be explained by a certain type of subsensitivity caused by the prolonged release of the active drug. The tolerance of pilocarpine gel was good; side-effects were minor and reversible. These results fulfill the expectations of the glaucoma therapists with respect to both efficacy and tolerance.

Acrylic Resins↗
PubMed1984

The immediate IOP response of Nd-YAG-laser iridotomy and its prophylactic treatability.

The response of IOP in the normotensive human eye to Neodym-YAG-laser iridotomy was investigated in this study. In 2 series of 10 patients, each unilateral laser iridotomy was performed with a YAG-laser prior to cataract surgery. In one group laser iridotomy was done without pre-treatment, in the second group laser iridotomy was preceded by treatment with 1% pilocarpine. Close follow-up of IOP before and after surgery was carried out with the Non-Contact-Tonometer. Laser iridotomy caused average IOP rises of 10 mmHg, which could be identified as early as 20 min after surgery, with a maximum of response after 80 min, and a declining IOP from 100 min post-operatively onwards. Pre-treatment with pilocarpine eyedrops could be reduce the laser-mediated IOP rise to less than one fourth. These results recommend a mild miotic for routine pre-treatment for iris laser surgery in order to cope with acute pressure rise as one of the major problems in these procedures.

Cataract Extraction↗