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[Eye injuries caused by lasers in military and industrial environment. Apropos of 13 cases].

PURPOSE: The aim of this study was to analyse the nature of wavelengths used by military forces, evaluate their clinical consequences in terms of ocular risk, and determine the therapeutic implications and specific preventative measures which should be implemented both in peace- and war-time-settings. MATERIAL AND METHODS: We analyzed retrospectively 13 cases of laser injury (12 patients) treated in our unit over the past 10 years. We recorded the characteristics of the responsible lasers, effects on visual acuity and visual filed, initial ophthalmoscopic and angiographic aspects, treatment undertaken and patient follow-up. RESULTS: Wavelengths were know in only 10 cases. In 9 cases a NdYag laser operating at 1063 nm was involved. The tenth case was an Argon Coirorint laser accident. In three cases the wavelength could not be ascertained because it was confidential information or had been emitted by the enemy and had not been identified. Ocular injury was bilateral in 1 case and unilateral in 12. Retinal lesions were foveolar in 8 cases with an initial visual acuity varying from 1/10 to 10/10. Visual loss depended on the extent of the burn and did not tend to improve despite vasoprotector and corticosteroid treatments. In 2 cases the injury progressed without formation of an epimacular membrane. Retinal lesions were extra-foveolar in 5 cases and in 1 case vitreous hemorrhage required vitrectomy. CONCLUSION: With the widespread use of Yag lasers and the soon to be employed tuneable lasers, there in major risk of serious ocular injury resulting from foveolar burns or peripheral retina trauma with vitreous hemorrhage. In a war situation, a large number of laser casualties producing peripheral vitreous hemorrhage would create an important logistics problem for vitrectomy. The accent must therefore be focused on prevention. Personnel must be informed of the danger and instructed in wearing filter glasses adapted to the wavelengths being used, if known, or a universal photoactivated protective device, as yet a hypothetical possibility.

Accidents, Occupational↗

[Protective effect on the corneal endothelium and remaining effect at the anterior chamber for three different kinds of viscoelastic devices].

PURPOSE: The present study was performed to evaluate the corneal endothelium protection and anterior chamber stagnation abilities of three different types of viscoelastic substances (Healon, Viscoat, HealonV). METHODS: Viscoelastic substances were selected at random for 120 eyes with cataracts, and the postoperative reduction rates of the corneal endothelium cells were compared. The residual viscoelastic substances after filling of the anterior chamber of pig eyes and aspiration with a handpiece were measured by an anterior eye segment image analysis system. The same procedures were performed in rabbit eyes and the residual levels of viscoelastic substances on the corneal endothelium were photographed histologically. RESULTS: The reduction rate of endothelium corneal cells tended to decrease with Viscoat three months after surgery. The results obtained with the anterior eye segment image analysis system showed that the residual level in the anterior chamber was higher with Healon. Histological analyses demonstrated residual Viscoat at the center of the corneal endothelium after perfusion. CONCLUSION: HealonV was superior in terms of spatial retention and Viscoat had corneal endothelium protection potential.

Aged↗

Conjunctival vaccination of the brushtail possum (Trichosurus vulpecula) with bacille Calmette-Guérin.

AIM: To determine the efficacy of conjunctival vaccination of captive brushtail possums (Trichosurus vulpecula) with bacille Calmette-Guérin (BCG), as measured by immunological responses to vaccination and response to intratracheal challenge with Mycobacterium bovis. METHODS: Nine adult male brushtail possums were vaccinated by the instillation of a suspension of BCG strain Pasteur 1173P2 into the conjunctival sac of each eye. Each drop contained approximately 2.5 x 105 colony forming units (cfu). At 8 weeks post-vaccination (pv) the vaccinated possums and 10 unvaccinated possums were challenged by intratracheal instillation of approximately 100 cfu of M. bovis. Cellular immune responses to bovine purified protein derivative (PPD) antigen were measured using the lymphocyte proliferation assay (LPA). Possums surviving to 50-51 days after challenge were euthanised and subjected to detailed post-mortem examination, including histopathology, to assess protection against tuberculosis. Sections of lung and spleen were cultured for M. bovis. RESULTS: No conjunctival inflammation or other adverse reactions to the administration of the vaccine were evident macroscopically. The vaccinated group showed a systemic cellular immune response to bovine PPD antigen at 4 and 8 weeks pv, and the response at 8 weeks was significantly greater than at 4 weeks (p<0.05). Conjunctival vaccination induced significant levels of protective immunity, measured as less mass of tuberculous lesions in lung (p<0.05) and less dissemination of disease in vaccinated compared with unvaccinated possums (p<0.05). CONCLUSIONS: Conjunctival vaccination with BCG induced a significant level of protective immunity against M. bovis infection in possums. This route of vaccination, together with intranasal aerosol vaccination, could be utilised in the delivery of an aerosolised vaccine using a device that sprays the vaccine suspension into the eyes and nose of possums.

Animals↗

[Light-induced damage to the eye].

The following review outlines the mechanisms of phototoxicity that are known so far, how they develop, which risk factors are involved, and what the consequences are for ophthalmology. It is necessary to differentiate between photochemical and thermal damage as they differ with regard to etiology and course. Photochemical damage in the lens originates from the absorption of UV-A light; damage caused by oxidation can cause nuclear cataract. Photochemical damage of the retina occurs typically after a longer interval and is mainly due to short-wavelength visible light ("blue light damage"); it entails destruction of membranes of the photoreceptor outer segments and finally photoreceptor death. There are indications that age-related macular degeneration can be accelerated by photochemical light damage. Lipofuscin, photo-sensitizing drugs and prolonged exposure, as well as aphakia and pseudophakia, can increase the risk. Thermal injury is caused mainly by absorption of longer-wavelength light by the retinal pigment epithelium; the effects are usually immediate. The amount of light that can cause threshold damage by common light sources and ophthalmological instruments is given in relation to wavelength, area, and the period of exposure. This information provides the criteria for optimal light-protection glasses. Phototoxic damage can be avoided by awareness, measurement and corresponding action, including the development of better industrial standards for sunglasses and light-emitting devices.

Eye↗

Helmet-mounted displays and facial injury in US Army AH-64A Apache accidents.

There is concern that the helmet display unit (HDU) used by AH-64 Apache helicopter pilots might contribute to facial injury in a crash. The US Army accident database was searched for HDU-related injuries in survivable Apache accidents 1985-1995. Four aviators in three crashes sustained HDU-related injury. These involved three periorbital contusions and two minor eye injuries. There were no sequelae. This equates to an incidence of 0.57 injured individuals per 100,000 flying hours or 8.0 injured aviators per 100 survivable Class A-C accidents in which the HDU was worn. Applying these data to the projected UK Army Apache flying hour programme suggests that one HDU-related injury might be encountered approximately every 10.1 years. This estimate should be interpreted with caution. Serious injury remains a possibility due to the proximity of the HDU to the eye and face.

Accidents, Aviation↗

Encapsulated cell-based intraocular delivery of ciliary neurotrophic factor in normal rabbit: dose-dependent effects on ERG and retinal histology.

PURPOSE: ERG and histologic changes were investigated in normal rabbits after intravitreal implantation of encapsulated cell technology (ECT) devices releasing ciliary neurotrophic factor (CNTF). METHODS: Fifteen adult New Zealand White albino rabbits had ECT devices secreting CNTF at 22, 5, or 0 ng/d implanted in the superior temporal quadrant of the left eye. The low dose has been shown to produce substantial rescue of photoreceptors in the rcd1 canine model of retinal degeneration. Right eyes were untreated. Ganzfeld dark- and light-adapted ERGs and clinical observations were performed at 5, 15, and 25 days after implantation. Rod a-waves and rod and cone b-waves and outer nuclear layer (ONL) morphology were evaluated at 25 days. RESULTS: Clinical examination showed minimal changes in a few CNTF-treated eyes, including vitreous membranes and engorgement of iris vessels at day 25. Retinas appeared normal. CNTF did not significantly affect the rod a- or b-waves, although the b-wave amplitude tended to be larger in CNTF-treated retinas at low flash intensities. The cone b-wave amplitude was significantly reduced in high-dose eyes at some flash intensities. The ONL area in high-dose eyes was significantly greater because of increased thickness than in fellow retinas. ONL cell size was significantly increased, and staining density decreased in CNTF-treated retinas. CONCLUSIONS: CNTF, given by intravitreal ECT device at doses that protect photoreceptors in a canine model of retinal degeneration (5 ng/d), did not adversely affect either rod or cone ERG function of normal rabbit retina. The cone ERG was more sensitive to suppression being reduced, at low flash intensities, by 22 ng/d. Dose-related changes in the ONL and photoreceptor cell nuclei did not represent a toxic effect, because they were not associated with deficits in the rod ERG over a broad range of intensities.

Animals↗

Radiation exposure to the surgeon during fluoroscopically assisted percutaneous vertebroplasty: a prospective study.

STUDY DESIGN: A prospective case control study design was conducted. OBJECTIVES: The purpose of the current study was to determine the intraoperative radiation hazard to spine surgeons by occupational radiation exposure during percutaneous vertebroplasty and possible consequences with respect to radiation protection. SUMMARY OF BACKGROUND DATA: The development of minimally invasive surgery techniques has led to an increasing number of fluoroscopically guided procedures being done percutaneously such as vertebroplasty, which is the percutaneous cement augmentation of vertebral bodies. METHODS: Three months of occupational dose data for two spine surgeons was evaluated measuring the radiation doses to the thyroid gland, the upper extremities, and the eyes during vertebroplasty. RESULTS: The annual risk of developing a fatal cancer of the thyroid is 0.0025%, which means a very small to small risk. The annual morbidity (the risk of developing a cancer including nonfatal ones) is 0.025%, which already means a small to medium risk. The dose for the eye lens was about 8% of the threshold dose to develop a radiation induced cataract (150 mSv); therefore, the risk is very low but not negligible. The doses measured for the skin are 10% of the annual effective dose limit (500 mSv) recommended by the ICRP (International Commission on Radiologic Protection); therefore, the annual risk for developing a fatal skin cancer is very low. CONCLUSION: While performing percutaneous vertebroplasty, the surgeon is exposed to a significant amount of radiation. Proper surgical technique and shielding devices to decrease potentially high morbidity are mandatory. Training in radiation protection should be an integral part of the education for all surgeons using minimally invasive radiologic-guided interventional techniques.

Aged↗

Standardization of occupational dose to patient DAP enables reliable assessment of radiation-protection devices in invasive cardiology.

PURPOSE: With the aim of assessing the effectiveness of radiation-protection devices in invasive cardiology, the goal of this study was to validate relative parameters for operator occupational exposure, standardized to the patient's primary dose. MATERIAL AND METHODS: One of these parameters was the local dose, measured in air at the operator's position per dose area product (DAP), applied to a male anthropomorphic Alderson-Rando phantom for simulation of coronary angiography. The second parameter was personal occupational dose to the operator per DAP, measured by thermoluminescence dosimeter stripes during 121 procedures in routine clinical work. RESULTS: The local and personal doses per unit DAP - using typical 0.5-mm lead overcouch and undercouch protection - were comparable (left eye 180 vs. 360, thyroid 260 vs. 260, left shoulder 280 vs. 150, chest 400 vs. 500, hands 400 vs. 550, waist 900 vs. 400 nSv/Gy x cm (2)). The results, however, were far lower than typically reported values. Our findings therefore disclose a typically inadequate use or acceptance by individual operators of available table-attached lead protection devices, and of ceiling-attached lead-glass screens. The additional use of individual 1.0-mm lead-equivalent garments reduced local doses to levels between 1. 10 %. CONCLUSIONS: DAP-standardized dose parameters - determined experimentally (phantom measurements), or in routine clinical work - are not appreciably influenced by the equipment age and type, or by the image-intensifier entrance dose rate of the respective catheterization system. They are consequently best suited for obtaining eloquent comparisons of various radiation-protection devices, and for reliable estimation of local scatter radiation exposure by simple documentation of intervention DAP.

Computer Simulation↗

Quantitative thermographic analysis of viscoelastic substances in an experimental study in rabbits.

PURPOSE: To measure the temperature parameters on the corneal surface during the delivery of standardized ultrasound energy assisted with ophthalmic viscosurgical devices (OVDs) or different temperatures of irrigating solutions in an experimental animal model. SETTING: Department of Ophthalmology and Visual Rehabilitation, Medical University of Lodz, and Central Institute for Labor Protection, National Research Institute, Warsaw, Poland. METHODS: Thirty rabbits (60 eyes) were randomly divided into 6 groups in which different OVD or balanced salt solutions (BSS) were used: group 1: Viscoat (sodium hyaluronate 3%-chondroitin sulfate); group 2: Provisc (sodium hyaluronate 1%); group 3: soft-shell technique; group 4: Celoftal (hydroxypropyl methylcellulose 2%); group 5: BSS 22 degrees C; and group 6: BSS 4 degrees C. After the nucleus and lens cortex were removed, the anterior chamber was filled with OVD or BSS and a phaco tip was introduced into the pupillary plane and switched on. The same phaco tip parameters were used in all groups. For thermographic measurements (ie, maximal temperature [MT], dynamic rise in temperature [DRT], and time when the maximal level of temperature [TMLT] was achieved), a thermocamera was used. RESULTS: Mean preoperative temperature on the rabbit corneal surface was 22.76 degrees C +/- 1.48 degrees C (SD). Working with a phaco tip increased the temperature in each group. A significantly higher MT was observed in group 5 (27.85 degrees C +/- 0.52 degrees C), followed by group 2 (27.75 degrees C +/- 0.54 degrees C), group 3 (27.74 degrees C +/- 0.46 degrees C), and group 4 (27.25 degrees C +/- 0.60 degrees C), than in group 6 (26.81 degrees C +/- 0.34 degrees C) and group 1 (26.52 degrees C +/- 0.48 degrees C) (P<.05). Significantly higher values of DRT and shorter TMLT values were observed in group 5 (1.16 degrees C/s +/- 0.42 degrees C/s, 4 seconds) and group 6 (0.91 degrees C/s +/- 0.13 degrees C/s, 5 seconds) than in groups 2, 3, 1, and 4 (0.09 degrees C/s +/- 0.07 degrees C/s, 30 seconds; 0.08 degrees C/s +/- 0.04 degrees C/s, 40 seconds; 0.07 degrees C/s +/- 0.03 degrees C/s, 45 seconds; 0.06 degrees C/s +/- 0.02 degrees C/s, 50 seconds, respectively) (P<.0001). CONCLUSIONS: Currently used OVDs potentially offer different levels of protection against the increase in temperature that occurs during phacoemulsification. Therefore, the surgeon should consider this aspect when choosing an OVD, particularly in difficult cases (ie, hard nucleus, shallow anterior chamber, endothelial abnormalities).

Animals↗

The dose-area product and assessment of the occupational dose in interventional radiology.

This study used dose-area product (DAP) data to determine the relationship between the dose received by radiologists and the DAP. The working conditions were simulated by phantom measurements. The doses of scattered radiation were measured using various scattering angles, distances and tube voltages. The calculated doses of scattered radiation were compared with the measured doses of scattered radiation. To test the validity of using such data for assessing occupational doses, the scatter dose on the radiologist or cardiologist was calculated from the DAP using the measured scatter factors. The dose to the lenses of the eyes may exceed the annual limit, and may therefore restrict the number of interventional procedures. A relation between the DAP and the occupational dose is difficult to establish, especially because staff doses are associated with the use of protective devices, positions of projections with respect to the patient, and working methods. However, the DAP may provide a good reference value for the dosimetric monitoring of staff.

Air Pollution, Radioactive↗

Occupational exposures to blood in a dental teaching environment: results of a ten-year surveillance study.

Evaluation of occupational exposures can assist with practice modifications, redesign of equipment, and targeted educational efforts. The data presented in this report has been collected as part of a ten-year surveillance program of occupational exposures to blood or other potentially infectious materials in a large dental teaching institution. From 1987 to 1997, a total of 504 percutaneous/non-intact skin and mucous membrane exposures were documented. Of these, 494 (98 percent) were percutaneous, and 10 (2 percent) were mucosal, each involving a splash to the eye of the dental care worker (DCW). Among the 504 exposures, 414 (82.1 percent) occurred among dental students, 60 (11.9 percent) among staff, and 30 (6 percent) among faculty. One hundred ninety-one (37.9 percent) exposures were superficial (no bleeding), 260 (51.6 percent) were moderate (some bleeding), and 53 (10.5 percent) were deep (heavy bleeding). Regarding the circumstances of exposure, 279 (54.5 percent) of the injuries occurred post-operatively (after the use of the device), and most were related to instrument clean-up; 210 (41.0 percent) occurred intra-operatively (during the use of the device); and 23 (4.5 percent) occurred when a DCW collided with a sharp object in the dental operatory (eight cases involved more than one circumstance). The overall exposure rate for the college was 2.46+/-0.11 SD per 10,000 patient visits. The average rate for the student population was 4.02+/-0.20 SD per 100 person-years, with the highest rates being observed among junior year students. The observed rates of occupational exposures to blood and body fluids in this report are consistent with published reports from several other educational settings. Dental teaching institutions are faced with the unique challenge of protecting the student and patient populations against bloodborne infections. Educational efforts must go beyond mere teaching of universal precautions and should include the introduction of safer products and clinical procedures that can minimize the risks associated with the hands-on aspects of the students' learning process.

Blood-Borne Pathogens↗

Optical radiation safety considerations for ocular glucose monitoring.

The potential for noninvasive detection of blood glucose is an area of intense academic and commercial research and a subject of keen interest in the diabetic and healthcare communities. A number of techniques are under investigation that attempt to infer blood glucose levels from measurements of optical signals. Frequently, these techniques are based on laser sources that may, under certain circumstances, be capable of inducing ocular injury. This article provides an overview of ocular damage mechanisms and the international standards for laser exposure limits that have been developed. The application of relevant standards to specific implementations of lasers in optical glucose sensing is presented. In addition, the concept of risk versus benefit for consideration of new medical devices is also discussed.

Animals↗

Invasion and survival of Fusarium solani in the dexamethasone-treated cornea of rabbits.

Electron microscopic observations, as well as in vitro experiments, on experimental Fusarium solani keratitis of rabbits were performed to study the mode of fungal invasion into the corneal stroma, the interactions between F. solani and inflammatory cells under the influence of topical dexamethasone (DXM) treatment, and the survival mechanism of the fungi in the DXM-treated cornea. Electron microscopy showed that, while the fungus invaded into the corneal stroma, digestion of collagen fibrils occurred around the hyphae, where amorphous material was often noted. In DXM-nontreated cornea, the fungal hyphae were entrapped by pseudopodia of the neutrophils and destruction of the hyphae was noted on day 3 of infection, most hyphae having disappeared by day 7. In the DXM-treated cornea, however, neutrophils could not ingest and destroy the hyphae. In qualitative nitroblue tetrazolium (NBT)-reduction tests using rabbit peripheral blood neutrophils, DXM significantly suppressed the rate of NBT-reduction and the rate of adherence to the fungal microconidia. In the DXM-treated corneal lesions, a considerable increase in both number and size of fungal peroxisomes was noted. Furthermore, the hyphae, surrounded by neutrophils, showed double or triple cell wall formation or sometimes a hypha-in-hypha structure. Similar hypha-in-hypha structures were also observed when the organisms were treated in vitro with a fungistatic concentration of H2O2. We suggest that this special structure is a protective device produced for the survival of F. solani when subject to neutrophil attack in the DXM-treated cornea.

Animals↗