The BioMask for treatment of corneal surface irregularities with excimer laser phototherapeutic keratectomy.

PURPOSE: To assess the characteristics of BioMask as a potential masking agent for use with the excimer laser. METHOD: We addressed ablation rate, smoothness, ease of use, dioptric shift, treatment of standardized irregular topography, and ability of BioMask to induce dioptric change in vivo. RESULTS: BioMask ablates at a rate of 0.28 microm per pulse. The BioMask conforms to the base curve of a contact lens in the excimer blank, eye bank eye, and rabbit eye with a r2 of 0.9982, 0.9844, 0.9858, respectively. We are readily able to create 20 diopters of flattening or steepening (r2 = 0.9944). Standardized irregular topography generation in the rabbit eye and then removal with BioMask was successful. The central corneal topography of the rabbit cornea showed predictable changes with various contact lens base curves with the BioMask (r2 = 0.875). CONCLUSIONS: BioMask has excellent potential as an ablatable mask material in the treatment of superficial corneal scars.

Comparison of three computerized videokeratoscopy systems with keratometry.

PURPOSE: To compare the reproducibility of computerized videokeratoscopy systems by using normal eyes and calibrated objects. METHODS: We evaluated the reproducibility of three commercially available videokeratoscopes [EyeSys, TechnoMed C-Scan, and PAR Corneal Topography System (CTS)] with the manual keratometer (Bausch & Lomb) by using calibration spheres and 10 normal subjects (20 eyes). All videokeratoscopy and keratometer results were obtained by one investigator (R.M.). Each eye and calibration sphere were submitted to 10 serial examinations by using each system. The average K of all points within the central 3.0 mm of the topography systems (central 3.0 mm) was compared with the average K of the manual keratometer. RESULTS: All videokeratoscopy systems correlated well with each other and manual keratometry when accessing aspheric and spherocylinder calibration balls. EyeSys central keratometry clinical results had the strongest correlation with the average keratometry results at 35%, followed by PAR-CTS at 25% and C-Scan at 5%. Among the videokeratoscopy units, EyeSys and PAR-CTS had the strongest correlation at 65%. The correlation between the TechnoMed C-Scan and both the EyeSys and PAR-CTS systems was 25%. There was a statistically significant difference (p < 0.05) between the systems when analyzing the results obtained from clinical subjects. The average keratometry (K) difference of human eyes between videokeratoscopy systems is <0.35 diopters (D) (p < 0.05), which may be clinically significant. The average manual K reading (42.97 D) is statistically significantly flatter (p < 0.05) than each of the videokeratoscopy units (EyeSys = 43.49 D; PAR = 43.48 D; C-Scan = 43.83 D). Comparing the 10 measurements of each eye or calibration object in the same videokeratoscopy system verified that the devices give reproducible results. The average standard deviation (ASD) of the keratometer was 0.10 D. The ASD of the videokeratoscopy units was 0.05 D for the EyeSys, 0.29 D for the PAR-CTS, and 0.31 D for the C-Scan systems. CONCLUSION: Based on this study, we should not assume that the results of different topography systems can be interchanged in clinical studies.

The Tampa Trephine technique with cat corneal endothelium.

The Tampa Trephine (Martin Marietta Speciality Components, Largo, FL, U.S.A.) penetrating keratoplasty technique uses a 7.0-mm corneal donor button with six rectangular 1 x 2-mm tabs of Bowman's layer, 75 microns in thickness, which are inserted into the recipient stroma beneath Bowman's layer. We evaluated the safety of the Tampa Trephine tissue-trephination method on the cat corneal endothelium combining vital staining and scanning electron microscopy, comparing it with the standard Weck trephination technique. The Tampa Trephine tissue trephination produces a donor button with a 6.7-mm diameter central area of normal endothelium. Localized peripheral areas of cellular loss, endothelial and Descemet's tears, endothelial detachment, and folding along the border of the trephination were observed with the Tampa Trephine method, all located in an area of < or = 150 microns, adjacent to the edge of the button. Standard trephination induced a localized peripheral area of endothelial damage < 50 microns in extension from the donor edge. A theoretic maximal 8.4% peripheral endothelial cell loss is induced with the Tampa Trephine trephination method, compared with a 2.8% loss with the standard procedure. The peripheral location of the alterations after the Tampa Trephine does not hinder the viability of the corneal endothelium, as it has been clinically observed.

Sports medicine. 2. Upper extremity injuries.

This self-directed learning module highlights recent advances in this topic area. It is part of the chapter on sports medicine in the Self-Directed Medical Knowledge Program for practitioners and trainees in physical medicine and rehabilitation. In this article, shoulder and elbow problems of the throwing athlete are emphasized. Common injuries involving the wrist and hand are also covered.

Sports medicine. 1. The physiatric approach.

This self-directed learning module highlights key elements in this topic area. It is part of the chapter on sports medicine in the Self-Directed Medical Knowledge Program for practitioners and trainees in physical medicine and rehabilitation. This article covers the role of the physiatrist in sports medicine and presents an overview of the diagnosis, treatment, and prevention of sports-related injuries. We describe how the physiatrist relates to other sports medicine practitioners and detail the stepwise physical examination of an injured athlete by a physiatrist.

Sports medicine. 5. The physiatrist as team physician.

This self-directed learning module highlights important aspects of the evaluation and care of the injured athlete by a team physician. It is part of the chapter on sports medicine in the Self-Directed Medical Knowledge Program for practitioners and trainees in physical medicine and rehabilitation. This article covers the components of a preparticipation examination, the on-field evaluation of head, spine, and limb injuries, and return-to-play criteria after specific injuries. Sports medicine for the physically challenged athlete, medicolegal considerations for the team physician, and anabolic steroids are also reviewed.

Motor unit analysis. Comparison between concentric and monopolar electrodes.

Motor unit action potential (MUAP) measurement parameters are reported to be affected by the type of needle electrode. MUAP amplitude measured with monopolar electrodes has been reported to be up to twice the amplitude recorded with concentric electrodes. We hypothesized that with current technology the difference in recordings from the two needles should be minimal and of little clinical significance. The right extensor digitorum communis muscle was examined in 15 healthy volunteers with first a concentric and then a monopolar needle. The filter band-pass of the electromyograph was 20 Hz to 10 kHz. Four first-recruited MUAPs were isolated by using each electrode. A separate muscle insertion was performed to locate each potential. Amplitudes were maximized. Consecutive MUAPs were averaged and measured. The mean (+/- SD) values of the measurements were as follows: amplitude: monopolar, 1038 (+/- 369) microV; concentric, 912 (+/- 315) microV; duration: monopolar, 10.8 (+/- 2.0) ms; concentric, 9.7 (+/- 1.7) ms. No statistically or clinically significant differences exist between these measurement values.

Electrodiagnostic characteristics of acute carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) exemplifies a cumulative trauma disorder which may occur in industrial settings. Occasionally, industrial workers develop CTS acutely over the course of a few days to a few weeks. We recently performed electrodiagnostic studies on 22 workers at a midwestern automobile manufacturing plant who developed symptoms compatible with CTS. All tests were within eight weeks of symptom onset; 70% were within four weeks. The acute syndrome was manifested by a conduction block of sensory, motor, or both fiber types beneath the carpal ligament. All patients received sensory studies; nine had motor studies as well. Sensory nerve latencies were not prolonged in proportion to the symptoms, which were short in comparison to the low amplitude sensory nerve action potential evoked proximal to the carpal ligament. Sensory nerve action potential amplitude at midpalm averaged 200% of the value obtained proximally. Because of short distance and residual latency, comparison of motor latencies proximal and distal to the carpal ligament was less helpful than the difference in amplitude of the evoked potentials. Amplitude of the distal response increased an average of 32%. Prompt identification of acute CTS was followed by a recommendation for job change which, along with conservative therapy, led to resolution of symptoms in 77% of patients. The diagnosis of acute CTS leading to avoidance of inciting activities is beneficial in the industrial setting.