Paul G. Rehkopf

Orbital fine needle aspiration biopsy with B-scan guidance.

In three patients we used B-scan ultrasonography to guide the placement of an aspirating needle, which allowed rapid and accurate cytologic diagnosis of retrobulbar orbital neoplasms. This technique spares the patient the greater costs, inconvenience, and morbidity of more invasive procedures.

Corneal topography using computer analyzed rasterstereographic images.

This paper describes a new method for determining corneal surface detail utilizing a modified Zeiss photo slit lamp. This system projects a grid onto the cornea through a cobalt blue filter. The tear film is stained with fluorescein, causing the projected grid pattern to be visible on the corneal surface. A video image of the grid is then digitized by an image processor which calculates surface detail by evaluating the distortion of the grid lines. Information on curvature and surface detail is obtained across the full corneal surface, both the central optical axis and peripherally beyond the limbus.

Use of directly acquired digital fundus and fluorescein angiographic images in the diagnosis of retinal disease.

Direct on-line acquisition of digital fundus and fluorescein images is a useful alternative to conventional fundus photography. Immediately after acquisition, digital images may be electronically reassembled, manipulated, and displayed, avoiding the delays inherent in film development. Digital fundus images, conventional photographs, and fluorescein angiograms were obtained at the same sitting in 50 consecutive patients with retinal disease. Digital studies were displayed on a video monitor and diagnoses were made directly from the screen. The interpretations based on digital images alone were virtually identical to those made from photographs, although the resolution of digital images was not equal to that of the photographic images. Despite this disadvantage, the system proved extremely versatile, and for this reason, digital image acquisition was used to routinely document the retinal findings in the majority of the clinical patients. RETINA 7:246–251, 1987.

Corneal Topography Using Rasterstereography

Rasterstereography is a new method of determining the topography of the cornea. Unlike Placido disc types of systems it does not depend on the reflectivity of the corneal surface, and it can provide information about the entire corneal, limbal and interpalpebral conjunctival surfaces. Since a smooth reflective surface is not required, images can be obtained with epithelial irregularity or defects, sutures, or stromal ulceration. A grid of horizontal and vertical bars of light is projected onto the cornea, and the pattern of the grid on the ocular surface is determined by its topography. The image is obtained by a video camera, and digitized, stored, and analyzed by an image processor. A three dimensional image of the corneal surface, contour maps of corneal elevation, and corneal curvature can be displayed.

Efficient reactivation of latent herpes simplex virus type 1 infection by excimer laser keratectomy in the experimental rabbit ocular model

PURPOSE To investigate the role of excimer laser keratectomy as a trigger for the reactivation of latent HSV type 1 (HSV-1) in the New Zealand rabbit ocular model. There are conflicting reports in the current literature about reactivation of HSV-1 after excimer laser photoablation. METHODS New Zealand rabbits were inoculated topically with HSV-1 McKrae or W strain in each eye, and culture-positive dendritic keratitis was documented on day 7. After the establishment of latency (21+ days), animals were divided into three groups: group I animals underwent excimer laser photoablation in each eye; group II animals received intrastromal injections of sterile water to act as positive controls (a standard method); and group III animals received no treatment and represented spontaneous shedders. All eyes were swabbed daily from days 1 through 10 and plated on A549 cells. Recovery of HSV-1 on days 1 through 10 postinduction was analyzed to compare the efficiency of the different methods of viral reactivation. RESULTS Reactivation of latent HSV-1 after excimer treatment was observed in nine (45%) of 20 eyes and was equivalent to the rate of reactivation seen in the positive control animals (eight [44.4%] of 18 eyes) (P=.99). Both of these rates were significantly greater than those of the untreated animals (one [5.6%] of 18 eyes) (P=.018). CONCLUSION Excimer laser keratectomy appears to be an efficient trigger for the reactivation of latent HSV-1 in the New Zealand rabbit ocular model.

A new method for assessment of changes in retinal blood flow

This study validates the use of residence time distribution (RTD) functions in human subjects to assess changes in retinal flow by using the widely recognized model of flow changes due to oxygen breathing. Changes in retinal blood flow may provide important information for clinical decision-making in several populations, including those with diabetic retinopathy, sickle cell disease and retinitis pigmentosa. Normal volunteer subjects were studied before and after oxygen breathing. After i.v. injection, relative fluorescence was obtained using scanning laser ophthalmoscopy/image processing in all vessel branches (average, 17). For each experiment, 64 frames (2/s) were digitized and were normalized using the RTD method. Vessel diameters were measured using densitometry techniques on fundus photos, where the diameter data made it possible to weight each vessel according to relative cross-sectional area to obtain a true mean circulation time (MCT). MCT increased for the group of subjects when breathing oxygen compared to normal air (P = 0.001), representing a decrease in retinal blood flow. Average MCT increased 2.82 +/- 2.51 s for all subjects, with an increase of 2.93 +/- 2.26 s in repeat trials for one subject. The proposed method uses information from all retinal vessels and allows the assessment of overall, as well as selected, regional retinal flow. It is more comprehensive than previous methods analysing single vessel flow. This method will be potentially useful for assessing hemodynamic changes in the retina associated with a wide range of eye disease.

Temporal changes in posterior capsulotomy dimensions following neodymium YAG laser discission

ABSTRACT We prospectively evaluated 20 eyes of 19 consecutive patients to determine the nature of temporal changes in posterior capsulotomy size, shape, and contour six weeks following neodymium:YAG laser posterior capsular disruption. Mean capsulotomy area increased by 32% (range 0 to 134%, P < .05, Student t‐test), although mean capsulotomy perimeter did not change appreciably. Capsular enlargement tended toward sphericity over time, with smoothing of edge contour from capsular tag retraction. Remodeling of opening size, shape, and contour was most likely to occur with preoperative evidence of capsular traction, and highly irregular capsulotomy borders immediately post‐discission.

The resistance to carbon dioxide laser ignition of a new endotracheal tube: Xomed laser-shield II

STUDY OBJECTIVE To assess the resistance of a new endotracheal tube to penetration and ignition by a carbon dioxide (CO2) laser at a clinically relevant power setting. DESIGN An unblinded, in vitro trial simulating clinical conditions. SETTING The operating room at a university medical center. PATIENTS None. INTERVENTIONS A CO2 laser at 20W with a beam diameter of 1 mm was directed onto the Xomed Laser-Shield II at several points: both perpendicular and tangential to the portion of the tube covered by the protective wrap, to the unwrapped silicone tubing just proximal to the cuff, to the cuff filled with saline and methylene blue, and to the unwrapped silicone tubing distal to the cuff. Trials were performed with or without supplemental oxygen (O2) blown onto the study site and with a 6 L/min flow through the tube containing one of four concentrations of O2 in O2-air admixtures: 21%, 30%, 40%, and 100%. MEASUREMENTS AND MAIN RESULTS Under all conditions, the laser did not penetrate the protective wrap, but the overlying polytetrafluoroethylene (Teflon) sheet was vaporized to an area equal to the size of beam application. The cuff was penetrated by the laser within 5 seconds. The unprotected silicone protein of the tube was penetrated by the laser in approximately 5 seconds, and time to formation of a blowtorch phenomenon shortened with increasing the percentage of O2 flowing through the tube. CONCLUSIONS The protective coating of the Xomed Laser-Shield II is laser-resistant, but the unprotected silicone proximal and distal to the cuff is laser-vulnerable and can, under certain conditions, promote a blowtorch phenomenon. This tube would be acceptable for use in oral and pharyngeal laser surgery, but we recommend its use only in well-ventilated areas, out of concern for exposure to the products of the pyrolysis of Teflon, specifically the development of polymer-fume fever.

Corneal Topography Using a Projected Grid

This chapter describes a new rasterstereographic method that can utilize either a modified slit lamp or operating room microscope. A grid is projected onto the cornea through a cobalt blue filter, and the tear film is stained with sodium fluorescein. The fluorescein is excited by the blue light, causing a grid pattern to become visible on the surface of the cornea. This corneal surface grid pattern is imaged by a video camera attached to the slit-lamp operating microscope. The video image is digitized by a digital image processor that utilizes the grid pattern to calculate the corneal topography. Unlike methods based on the Placedo disk, this system provides information across the full corneal diameter, including the optical axis, and extending onto the sclera, and this method is not affected by corneal surface or stromal defects.

System For Acquisition, Analysis, And Archiving Of Ophthalmic Images (IS-2000)

The IS-2000 permits image acquisition with a color TV camera, analysis in digital format, and archival storage in analog format on an optical disk. The IS-2000 was designed from a system model of a consulting ophthalmic practice. We describe the model and the resulting system, pointing out similarities to (and differences from) radiology.