David L. Krohn

Central Anterior Chamber Depth After Laser Iridectomy

We found the true anterior chamber depth to be unaffected by successful laser iridectomy in ten eyes treated by this modality for chronic angle-closure glaucoma. The apparent general deepening seemed to be the result of peripheral chamber deepening combined with the common use of strong cycloplegic agents, reversing the shallowing effect of preoperative miotic medications.

Inhibition of Trauma-Induced Miosis by Indoxole

The relative effect of topically administered polysorbate-80 solutions of indoxole and indomethacin were compared as to inhibition of pupillary constriction induced by standard trauma, in the presence

Transcorneal Flux of Topical Pilocarpine to the Human Aqueous

Aqueous fluid was withdrawn from eyes of patients undergoing cataract extraction at various intervals after administration of two drops of 2% pilocarpine HCl in a standard manner. Determination of aqueous pilocarpine concentration was made both by spectroscopy of a ferric hydroxylamine complex and by gas-liquid chromatography. Results of both methods were consistent in indicating that concentration does not rise at any time following such topical instillation beyond 5 microgram/ml, with an average of 1.67 microgram/ml, representing a flux efficiency of 0.03%. These findings correlate well with previous investigations of transcorneal flux of pilocarpine for the rabbit in a transport chamber system, in which comparable low flux efficiency was found after simulated drop administration. This serves in some measure to validate an extrapolation of other findings in chamber experiments to the living human eye.

Relative Blue-Light Extinction in Lens Nucleus Related to Age and Cataract

The extent of visual function loss from nuclear cataractous change can be estimated by observing the extinction of blue light compared to white light as a function of sagittal lens depth in standard slit lamps. Apparent extinction (loss of transmissivity) of 50% or more of the depth of the lens in blue light of maximal intensity compared to white light at minimal intensity is associated with marked visual loss. However, this transmissivity ratio of 0.5 or less also applies if light intensity remains constant and the blue filter is simply moved in and out of the light beam. Therefore, if 50% or more of the lens appears dark to blue-filtered light, nuclear changes have significantly decreased effective visual acuity. Relative blue-light extinction associated with nuclear change that may be amenable to surgical correction can thus be distinguished from the extinction effect caused by age alone.

Anesthesia in rabbits by intrahepatic sodium pentobarbital

Abstract A reliable method for anesthesia of laboratory rabbits by intrahepatic injection of sodium pentobarbital was developed. Anatomical dissection was the basis for designation of external landmarks for injection. The advantages of the method have been simplicity, accuracy of dosage based on body weight, and an induction speed great enough for convenience but consistent with life support measures in case of respiratory collapse. No restraint was required and the injections were easily made without assistance. Supplemental block or local infiltration anesthesia was usually required for surgical procedures. In 421 anesthetic procedures, the fatality rate was 2.9% from anesthesia-related events but the rate was much less in the last 200 procedures due to refinement of technique. Liver chemistry determinations and histopathology demonstrated insignificant hepatic damage and there was no gross morbidity.