[Perspectives of laser-assisted keratoplasty: current overview and first preliminary results with the picosecond infrared laser (λ = 3 µm)]

BACKGROUND

This article provides a review of the current state of laser-assisted keratoplasty and describes a first proof of concept study to test the feasibility of a new mid-infrared (MIR) picosecond laser to perform applanation-free corneal trephination.

METHODS

The procedure is based on a specially adapted laser system (PIRL-HP2-1064 OPA-3000, Attodyne, Canada) which works with a wavelength of 3,000 ± 90 nm, a pulse duration of 300 ps and a repetition rate of 1 kHz. The picosecond infrared laser (PIRL) beam is delivered to the sample by a custom-made optics system with an implemented scanning mechanism. Corneal specimens were mounted on an artificial anterior chamber and subsequent trephination was performed with the PIRL under stable intraocular pressure conditions.

RESULTS

A defined corneal ablation pattern, e.g. circular, linear, rectangular or disc-shaped, can be selected and its specific dimensions are defined by the user. Circular and linear ablation patterns were employed for the incisions in this study. Linear and circular penetrating PIRL incisions were examined by macroscopic inspection, histology, confocal microscopy and environmental scanning electron microscopy (ESEM) for characterization of the incisional quality. Using PIRL reproducible and stable incisions could be made in human and porcine corneal samples with minimal damage to the surrounding tissue.

CONCLUSION

The PIRL laser radiation in the mid-infrared spectrum with a wavelength of 3 µm is exactly tuned to one of the dominant vibrational excitation bands of the water molecule, serves as an effective tool for applanation-free corneal incision and might broaden the armamentarium of corneal transplant surgery.

[First results of the wave-guide in CO2-laser surgical reduction of the hyperplastic nasal turbinates]

BACKGROUND

The CO2-laser-surgical reduction of the hyperplastic nasal turbinates represents a standard procedure in ENT-Surgery. In the presented paper, the authors introduce a new technique for the treatment of hyperplastic turbinates.

METHODS

The laser beam is transmitted through a 90 degrees handpiece to the mobile "infra-guide" wave guide, which contains a 1 mm ceramic tube. By application of mirrow pieces with different angles, laser surgical reduction of those parts of the nasal turbinates is possible, which normally can not be reached by conventional, tangentially to the mucosa directed laser beams. The direction of the laser beam is controlled either optically, as in endonasal sinus surgery, or monitored through a camera. A total of 36 patients (22 women, 14 men, mean age 32.7 years) with nasal turbinate hyperplasia and either impaired nasal breathing and/or retronasal drip were treated with the new method.

RESULTS

The laser wave guide represents a minimally invasive and basically complication-free method feasable on an outpatient basis. As a particular advantage, laser surgical reduction of the posterior parts of the inferior and also the middle turbinate is possible. The majority of the patients relates of an improvement of the preoperative symptoms (regarding reduction of impaired nasal breathing: 61.3 %, regarding reduction of post nasal drip 87.1 %).

CONCLUSION

The laser wave-guide represents a basically complication-free, minimally invasive supplement to the different treatment modalities of the hyperplastic nasal turbinates.

Application of a small microcomputer to cell image analysis

Solutions to three problems in using small microcomputers for interactive cell image analysis are discussed. (1) To allow interactive processing of up to 62 X 88 pixels on inexpensive screens, data can be displayed in gray levels with an approximate logarithmic grading. Each pixel is composed of 32 screen coordinates, applying the dither matrix method to avoid artificial structures. (2) To mark special regions of interest in the image, a graphic cursor, handled from the keyboard, was implemented. (3) To evaluate parts of the image, as outlined by the cursor, the program must distinguish whether a particular pixel is outside, inside or on the border of the region. The developed algorithms permit practical interactive evaluation of cell images on a small microcomputer, with no image analysis implementation. However, it is necessary that the assembly language of the microprocessor be available for some sophisticated programming and that the operating system support graphic facilities with an appropriate resolution.

[Reaction of the tympanic tensor muscle--elicited by nasally applied trigeminal stimulants]

Computerised evaluation of tensor muscle reaction was carried out by using a biosignal analysing unit triggered by nasal inhalation. The trigeminus nerve was stimulated by application of 3-molar acetylacetic acid into the nasal respiratory air, inducing a contraction of the tympanic muscle, followed by a change in impedance. This change in impedance of the tympanic membrane ossicle system was recorded and printed out on a display. In this manner evidence was obtained of a tensor muscle reaction induced by the third branch of the trigeminal nerve as efference, and demonstrated for the first time. This reflex arc had long been considered as being of negligible clinical importance before its stimulation and measurement had become possible. It is a generally accepted theory that the reflex arc of the m. tensor tympani is linked to the formatio reticularis which assesses the sensory afferences. For this reason, the reflex arc habituates rapidly, and continuous stimulation is no longer possible.

Scanning microfluorometric measurements of acriflavine-Feulgen-SITS-stained fibroblasts during G0-G1 transition

For the characterization of nonproliferating cells, scanning microfluorometric measurements of mouse fibroblasts (L-929) during G0-G1 transition were carried out. Samples were taken at different time intervals after serum stimulation. Cells were stained for DNA using the acriflavine-Feulgen method and for protein with 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS). Considering that acid hydrolysis removes basic proteins, SITS fluorescence represents acidic proteins, which within the nucleus are to a large degree located in the nucleoli. From each preparation, nuclei were scanned at a 0.5 micrometer step size, measuring DNA and protein fluorescence successively. Fluorescence data of nucleoli were evaluated. The number of nucleoli reached a maximum two hours after stimulation. Both the total nucleolar area and fluorescence were found to increase, up to 8 and 11 hours, respectively, by a factor of four to five. This indicated that these fluorescence parameters can be used to distinguish between resting and cycling cells.