Action spectrum and recovery for in vitro UV-induced cataract using whole lenses.

PURPOSE: To establish the in vitro action spectrum for acute UV cataractogenesis using whole cultured lenses. The recovery pattern of the induced cataract was also investigated. METHODS: Aseptically dissected porcine lenses were cultured in glass chambers. At 1 week, lenses were exposed to a predetermined UV energy (J/cm(2)) at specific wavebands ranging from 270 to 370 nm at 5- and 10-nm intervals. The UV energy was generated by a PRA integrated arc lamp system using a water-cooled 1000 W, high-pressure xenon lamp. The lamp output was limited using a deionized water filter, a monochromator, and secondary optics. An electronic shutter was used to control the exposure time. The median effective dose, ED(50) (i.e., UV energy threshold) for each waveband was statistically determined using probit analysis. Irradiated spots (3.06 mm(2)) on the lenses were monitored every 6 to 12 hours up to 48 hours postirradiation for any UV-induced opacity with a dissecting microscope and photomicrography. The ED(50)s were plotted against wavelengths to obtain the action spectrum. RESULTS: The threshold values for 270, 300, and 365 nm were 0.057, 0.069, and 137.19 J/cm(2), respectively. Permanent UV-induced cataract was obtained at twice the threshold values for UVB and UVA. CONCLUSIONS: An action spectrum for in vitro UV-induced cataract using whole cultured lens is established. These data are comparable to published in vitro (with isolated lens epithelial cells) and in vivo action spectra. The recovery pattern appears to be similar to the in vivo situation.

Eye exposure to optical radiation in the glassblowing industry: an investigation in southern Ontario.

OBJECTIVE: To investigate if the levels of optical radiation hazards in glassblowing are well classified according to the hazard types defined in the Canadian Standards Association (CSA) standard for industrial eye protectors. METHODS: We carried out radiometric measurements, and questionnaire survey in 4 university glassblowing laboratories, and 3 private studios. RESULTS: There is exposure to low levels of UV and IR radiation in all glassblowing operations. A supra-threshold IR radiation level exists in the craft glassblowing. The use of eye protectors is based on past experience regardless of the level of ocular exposure. CONCLUSIONS: Optical radiation hazards exist in both craft and scientific glassblowing. There seems to be an inadequate understanding about radiation types encountered by glassblowers.

A study of the accuracy of corneal reflection pupillometers.

We studied the accuracy of nine corneal reflection pupillometers made by three manufacturers, because, at the time of investigation, we could not find any information about their accuracy. For this purpose two steel balls separated by spacer bars, were positioned to simulate nominal inter-pupillary distance (PD) measurements of 55, 60, 65 and 70 mm. Ten measurements of each 'PD' for distance vision, were made by two experienced observers, with each instrument. We found that interobserver differences in measurement were clinically insignificant most of the time, although some data sets were significantly different statistically. The most consistent and accurate measurements of PD were achieved with PD 65 mm. The average error in mean value of the measurements for all PD's, was 2.3 mm, and the average of the standard deviation in our measurements, was 0.26 mm. Significant sources of error were poor eye relief in all instruments evaluated, as well as friction in the scale adjustment mechanism in some instruments. Our findings show that while a given pupillometer may be relied upon to give consistent readings (within the limits of clinically acceptable error), its accuracy should be checked periodically, especially for very small and very large PD measurements.

Glassblowers' ocular health and safety: optical radiation hazards and eye protection assessment.

The aims of this study were to investigate the levels of optical radiation exposure in glassblowing and to determine type(s) of protective eyewear commonly used. Radiometric measurements of radiant emissions from different molten glass materials and heating systems were carried out in six installations. Spectral transmittance curves of available protective lenses used at the locations were obtained. Significant variation (P = 0.0001) in ocular irradiation was obtained. All operations produced irradiances higher than the threshold limit values (TLVs) for the visible spectrum (400 to 700 nm). In craft glassblowing which employs furnace systems, irradiance levels exceeding the TLVs for near infrared (760 1o 1100 nm) were obtained. Molten soda-lime and quartz glasses emitted substantial subthreshold near UV radiation. This study shows that variation exists in glassblowing ocular radiation exposure due to different glass materials and heating systems, therefore selection of appropriate eye protector should be on an individual basis.

Occupational exposure to optical radiation and the ocular health status of glassblowers.

The occupational radiation exposure levels and the ocular health status of a sample of glassblowers in southern Ontario were evaluated. The form of ocular protection was also assessed. Measurements of radiant emissions from different molten glass materials were carried out. A total of six glassblowing installations, 15 glassblowers and 42 non-glassblowers participated in the study. The spectral transmittances of samples of the protective lenses were obtained. Tonometry, biomicroscopy, ophthalmoscopy, pachometry, Schirmer tear test, endothelial photography were completed on all the volunteering subjects. The glassblowers' ocular findings were compared to those of non-glassblowers. No indication of cataract was observed among this group of glassblowers. Although, a preponderance of grade 2 polymegethism among the glassblowers (47% compared to 11% in non-glassblowers) was found, there was no significant difference in their ocular health. Variation in the corneal irradiance from occupational exposure was obtained, and in addition, the use of protective lenses was found to be inappropriate. In order to prevent against any long-term chronic pathologic effect, the use of appropriate ocular protection is advised.

Ocular hazards of industrial spot welding.

Any welding process is perceived to be a radiation hazard to the eye. Site visits were made to an automotive assembly plant to assess the levels of optical radiation and other hazards on the production line. Measurements were taken with a scanning spectro-radiometer and optical power and energy meters at operating working distances at spot welding stations where nonrobotic procedures were performed. Ultraviolet (UV) irradiance levels produced while spot welding with electrodes operating at 10 to 15 kA and 10 to 20 V were several orders of magnitude below recommended safety limits for industrial exposure. Flashes were rich in visible light and infrared (IR) radiation, but not at hazardous levels. The principal hazards in manual spot welding with high-current electrodes are high-speed droplets of molten metal produced by the process. These are easily defended against by wraparound polycarbonate eye shields.

Impact resistance of Transitions Plus spectacle lenses.

Although it has been shown that photochromic glass industrial lenses do not provide adequate occupational impact protection, they are frequently requested by outdoor workers wanting sunglasses. The recent introduction of Transitions Plus (TP), a photochromic plastic lens, may meet the needs of these workers. The impact resistance of 60 TP lenses of dress thickness was studied using a ballistic test. Lenses were edged and mounted in metal industrial frames. The completed spectacles were placed on a headform for ballistic testing using a 6.5 mm (1/4 in) steel ball propelled from an airgun. The lenses were divided into test groups that received: (1) a single impact at the geometrical center by a ball traveling at 18 m/s (59 ft/s) and (2) 50 consecutive impacts at 18 m/s, or (3) a single impact at 46.5 m/s (152 ft/s). All lenses passed the single impact test at 18 m/s. Four lenses broke under repeated impact. All lenses subjected to the high-speed impact test failed, either breaking or being dislodged from the frame. These findings show that dress thickness TP lenses provide impact protection from small blunt missiles traveling at moderate speed, and that they are durable under repeated low energy impact. However, thicker lenses must be used when the wearer has a high risk of ocular exposure to small high-speed missiles in the workplace. It can be concluded that TP lenses may be used in occupational eyewear for many outdoor workers who want photochromic sunglass lenses, provided that other needs for vision and occupational safety are also satisfied.

The absence of a photopic influence on the refractive development of the embryonic eye of the clearnose skate (Raja eglanteria).

The clearnose skate (Raja eglanteria) develops in an almost opaque eggcase and lays its eggs in pairs. One sibling from each of eight pairs of skates was removed from its eggcase during embryonic development, while the other sibling developed inside the eggcase. The refractive development of the eyes at hatching was examined to see if ambient light exposure during embryonic development could influence the refractive states of hatchlings. Measurements included refractive states, ocular dimensions and lens focal properties. The differences in measurements between the two groups were not significant, which would indicate that environmental light does not influence the refractive development of the embryonic skate eye.

A ballistic evaluation of the impact resistance of spectacle lens materials.

The impact resistance of chemically and thermally hardened glass lenses of 2.2- and 3.0-mm thicknesses was evaluated using a ballistic test. Each lens was edged and mounted into a spectacle frame, which was placed on a standard headform. A 6.5-mm steel ball was fired from an air gun at the center of the lens at increasing speeds until the lens broke. The multiple impact data were used to plot cumulative breakage curves. We found that heat-treated photochromic glass and heat-treated crown glass fail at similar missile speeds and that chemical treating considerably improves the impact resistance of crown glass but not of photochromic glass. The poorer performance of photochromic lenses indicates that they should not be prescribed when optimal impact protection is required. Plastic lenses show superior performance.

Evaluation of ocular hazards due to electric arc flash at an in-line switch.

We investigated the ocular damage resulting from operation of a solid blade pole-mounted in-line electrical switch at between 16 and 17 kV with current loads between 38 A and 340 A. Spectroradiometric data for the electric arcs produced as the switch was opened were obtained over the waveband 200 to 1500 nm. The eyes of adult pigmented rabbits were exposed to the arc flash at a distance of 2 m. The ocular tissues were assessed clinically and histologically up to 48 h postexposure. Threshold damage was clinically detectable only in eyes exposed to a 340 A arc. We conclude that at the normal current loads on a 17-kV electric power transmission line, the principal oculovisual hazards are due to molten metal fulminated from the switch by the arc, and after-images due to the bright visible light flash. At a working distance of 2 m, the ultraviolet ocular hazard is negligible. Adequate eye protection is provided by clear polycarbonate safety lenses.

Tinted lenses and the ANSI standards for traffic signal transmittances.

The transmittance properties of 96 tinted lenses were examined to determine whether these lenses met the American National Standards Institute (ANSI) Z80.3 standards for traffic signal transmittances and color shifts. Transmission functions of the lenses were measured using a Zeiss Spectrophotometer, and the luminous transmittances and color shifts were calculated according to the ANSI guidelines. Approximately 50% of the sampled tinted lenses failed to meet at least 1 of the ANSI requirements. Lenses that failed to meet several ANSI requirements were often special purpose sun lenses. Although the special purpose tinted lenses do not have transmittance requirements for traffic signals, it is not always clear from the manufacturers' brochures that the lenses may be unsuitable for driving.

Contact lenses and acute exposure to ultraviolet radiation.

The eyes of twenty-three pigmented rabbits (weight approximately 2kg) were irradiated with a single dose of UVB (285 to 315 nm total bandpass at approximately 450 muW.cm-2 irradiance) for exposure times of 22s to 1680s. One group wore UV-transmitting soft contact lenses during exposure of one eye with the fellow eye serving as a control while another group wore a UV-absorbing lens on each eye with only one eye irradiated. UV-transmitting contact lenses did not affect the clinical response to UV exposure whereas the UV-absorbing contact lenses protected the corneas as could have been predicted by consideration of the absorption characteristics of the lenses at the experimental waveband. In no case was there any evidence of adhesion between the contact lens and the corneal epithelium.

Keratopathy with low dose chloroquine therapy.

Antimalarial drugs (4-aminoguinolines) are often used as non-steroidal anti-inflammatories and remission inducers in the treatment of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). In this paper we report on ocular signs of aminoquinolinic toxicity among 39 patients, 31 with RA and 8 with SLE. These patients received either chloroquine 250 mg q.h.s. or hydroxychloroquine 200 mg b.i.d. No maculopathy was detected, however 75% of the patients showed various degrees of keratopathy ranging from epithelial haze to dense "whorl" deposits. No correlation was found between severity of the keratopathy and the estimated total amount of aminoquinoline administered.

Tinted hydrogel lenses: an assessment of glare sensitivity reduction.

The effect of tinted flexible contact lenses on light sensitivity and photophobic response has often been questioned but never thoroughly investigated. An Alpascope was used to investigate whether tinted hydrogel contact lenses would relieve glare sensitivity in pre-adapted contact lens wearers. Various densities of sky blue and autumn amber Cibasoft hydrogel lenses were used in the study. Analysis of the Alpascope data using the t-test, one-way analysis of variance and Duncan's test showed that there was no reduction in glare sensitivity when tinted contact lenses were worn.

Tinted hydrogel lenses permanency of tint.

The spectral transmittances of a sample group of tinted hydrogel contact lenses were analyzed to assess the reproducibility of tinted lenses of a given density. Transmittance data were used to assess permanency of the tint after a 14-day cycle of daily cleaning, sterilization, and storage using a variety of cleaning and sterilization treatments. One-way analysis of variance of the transmittance data has demonstrated significant variations in the density of tint for Cibasoft lenses of a given color and density. However, these variations are smaller than the manufacturer's stated criterion for acceptable differences in tint density at a given tint level, i.e., light, medium, or dark. The Cibatint is stable when the lenses are cleaned with the Septicon and Miraflow systems. However, tinted hydrogel lenses from other manufacturers demonstrated changes of tint which were dependent upon the cleaning and sterilization methods used.

Ultraviolet-B damages corneal endothelium.

Direct in vivo observation of acute ultraviolet (UV)-induced corneal endothelial damage is not possible due to the more severe damage produced in the epithelium. In order to quantify damage and evaluate endothelial recovery an indirect method was used. Eyes of pigmented rabbits were irradiated with UV-B (290 to 320 nm) isolated from the output of a high-pressure 1000 W reflectorized Xenon arc lamp by a grating monochromator and appropriate filters. The peak wavelength of the radiation used was 305 nm, with a 18 nm bandwidth at half-maximum. Corneal thickness variations measured with a modified Zeiss (Oberkochen) pachometer were used to follow alterations in epithelial and endothelial function. Epithelial damage alone resulted in a maximum thickness increase of 13.5% within 24 hr with recovery within a further 24 hr. Greater increases in corneal thickness, in the absence of anterior uveal involvement, were taken to indicate endothelial damage, and reached maximum at 2 days, with recovery occurring in 7 days. The threshold for endothelial damage sufficient to disturb corneal deturgescence was 0.12 J X cm-2.

Retinal protection from solar photic injury.

Samples of protective filters commonly used to observed the partially eclipsed sun were obtained and subjected to spectrophotometric analysis over the wavelength interval 330 to 2500 nm. Performance of these filters was compared with criteria for adequate ocular protection which have appeared in the literature. It appears that the greatest safety is provided by those devices incorporating a monatomic metallic coating as the filtering agent.