Development of an intraluminal device for the treatment of aortic regurgitation: prototype and in vitro testing system.

OBJECTIVES: Development of an intraluminal device to reduce aortic regurgitation could provide a strategy intermediate between medical treatment and aortic valve replacement. An initial prototype and a testing system have been designed. METHODS: Aortic valves obtained from heart transplant recipients were explanted and assessed in a mock circulatory loop with resistive and capacitive elements, including pressure-flow characteristics, similar to those of a normal arterial system. Normal heart function was simulated by a pulsatile ventricular-assist device. Pressure on each side of the valve and flow through the valve were recorded, allowing the calculation of regurgitant fractions and transvalvular gradients. Six solid geometrically differing obturators were tested. RESULTS: All six designs resulted in significant reduction in aortic regurgitation (p < 0.0001), ranging from 15% to 38% improvement compared with control values. Small increases in transvalvular gradients (from 0 to 7 mm Hg) were also noted. DISCUSSION: Initial results suggest that an intraluminally placed obturator can reduce aortic regurgitation without creating clinically significant transvalvular gradients. These initial in vitro experiments demonstrate the feasibility of an intraluminal device for the treatment of aortic valve disease, and further investigation is warranted.

Confocal slit divided-aperture microscope: applications in ear research.

A confocal, scanning slit microscope that uses separate portions of the objective aperture for illumination and imaging rays achieves a high degree of optical sectioning. This capability permits visualization of individual cells within the intact inner ear in guinea pigs and cats, and it facilitates directing a laser heterodyne interferometer beam so that vibration of selected cells can be measured. A concentric singlet lens is added to the front of a long-working-distance microscope objective to increase the numerical aperture from 0.4 to 0.53 while retaining a working distance of 6 mm. The measured optical-sectioning capability is compared with the theoretical performance and with the calculated curve for a full-aperture pinhole confocal system.

Clinical microscopy of the cornea utilizing optical sectioning and a high-numerical-aperture objective.

A doublet contact element was added to a long-working-distance objective to increase the numerical aperture to 0.75 and to maintain the focus during in vivo examination of the eye. Optical sectioning by use of confocal slits permits visualization of weakly scattering structures within the cornea. With photographic film and a 1/60-s exposure time to limit the effect of eye movement, an effective optical section half-thickness of approximately 20 microns was realized. Structures observed in the cornea include epithelial cells (surface, wing, and basal cells), nerve-fiber bundles in the subepithelial region, keratocytes and inflammatory cells in the stroma, and endothelial cells.

Use of transendothelial electrical potential difference to assess the chondroitin sulfate effect in corneal preservation media.

Corneal preservation time can be prolonged using chondroitin sulfate (CS) in preservation media and recently a great deal of attention has been focused on evaluating the effectiveness of CS. So far evaluations of the effectiveness of this and other additives have been based on determining the state of the cornea at the end of the preservation period. A more informative determination of the viability of stored corneas can be made by monitoring their physiological parameters throughout the storage period. We have accomplished this by monitoring in vitro the transendothelial electrical potential difference across deepithelialized rabbit corneas. We found that corneas stored in solutions containing basal salts, glucose and CS maintained higher transendothelial potential differences than corneas stored in the same solutions without CS, thus confirming the benefits of using CS for medium-term corneal preservation. The beneficial effects of CS were optimal at the 1% concentration, and were reduced at higher and lower concentrations.

Measurement of intraocular lens decentration and tilt in vivo.

A method for measuring the tilt and decentration of intraocular lenses (IOLs) in the static eye using the Purkinje image locations is presented. The patient fixates on a target that is coaxial with the camera or is at a predetermined angle with the camera axis. A telecentric stop is introduced in the camera so the positions of the Purkinje images on the film are independent of their distance from the camera. Measurements of the image locations on the film are used with anterior chamber depth and corneal curvature measurement to calculate the tilt and decentration of the IOL. In a group of 14 randomly selected patients with posterior chamber IOLs, 13 gave Purkinje images that could be measured. The average tilt was 7.8 degrees and the average decentration was 0.7 mm.

Wide field specular microscopy of excised donor corneas.

Routine examination of the endothelium of eye bank excised corneas in the McCarey-Kaufman storage medium has been accomplished by using a new bottle cap with an optical quality window. A sterile system is maintained as the cornea remains in the bottle within which it is sent to the surgeon, without handling or manipulation of the tissue. In combination with the wide field specular microscope in the noncontact mode, endothelial cell measurements and qualitative information about the endothelial surface are now available.