Bernt Ralph Chou

Verified

Bernt verified their affiliation via an institutional email.

Learn more

Verified

Bernt verified their affiliation via an institutional email.

Learn more

• BSc(Hons), MSc, OD
• Professor Emeritus at University of Waterloo

Globally, hundreds of millions of outdoor workers are exposed to solar radiation (SR) for the majority of their working life. Such occupational exposure is known to induce various adverse health effects to the eyes, mainly related to its ultraviolet (UV) component. The present work is a call-to-action aimed at raising the awareness on the need of h...

We present spectral transmittance curves over the waveband 200 to 2500 nm for 47 non-prescription sunglass lenses. All appear to provide adequate protection from ultraviolet radiation, especially those which have been advertised as such. Other criteria for choosing the "right" sunglass are discussed briefly.

Tinted spectacle lenses are used for a variety of reasons including comfort, reduction of glare, enhanced vision under certain conditions, cosme­sis, status for the wearer, and protection from radiation and/or impact. The selection of tints for protection from hazardous levels of optical radiation in industry and other work environments is well doc...

We investigated the compliance of 43 commercially available solar filters (eclipse glasses) with the ISO 12312-2:2015 standard by measuring their spectral transmittances (280–2000 nm) and calculating their luminous, solar ultraviolet A, ultraviolet B, and infrared (IR) transmittances. We also evaluated the filters for usability by observing the ful...

Background: The World Health Organization (WHO) and the International Labour Organization (ILO) are developing a joint methodology for estimating the national and global work-related burden of disease and injury (WHO/ILO joint methodology), with contributions from a large network of experts. Here, we present the protocol for two systematic reviews...

Background: H.J. Haase developed a set of tests for measuring associated phoria and stereopsis using a variety of different targets for each. This study investigates the test-retest repeatability of the distance and near stereopsis tests for the MKH-Haase charts. Methods: MKH-Haase contour (Line Test) and randomdot (Steps Test) stereopsis tests wer...

Background: The most commonly identified reason for requiring or using occupational eye and face protection is for protection against flying objects. Standards vary on what risk may require protection of the eyes alone and what requires protection for the whole face. Information on the minimum energy transfer for face damage to occur is not well-e...

Background: The Pola Test measures associated phoria at distance and near using a variety of different targets. This testing method and interpretation is referred to as the MKH-Haase method. The aim of this study is to compare the associated phoria values measured using the MKH-Haase chart results with other associated phoria tests.

Purpose: To investigate the effect of ultraviolet radiation (UVR) on the impact resistance of organic ophthalmic lens materials. Methods: Plano power CR39, Phoenix, Trilogy, and polycarbonate lenses with various scratch-resistant (SR) and/or antireflection (AR) coatings were obtained in batches of 40 units. All lenses had a nominal thickness of...

H.J. Haase developed a set of tests for measuring associated phoria and stereopsis using a variety of different targets for each. This testing method is known as the MKH-Haase method and it is used commonly in Germany. The aim of this study was to investigate the test-retest repeatability of the distance and near associated phoria tests for the MKH...

Scratches and other surface abrasions on protective eyewear can shorten their life cycle by scattering light from the image, which will compromise visual performance. Although scratch and abrasion resistance testing is well developed, there is little information available regarding visual acuity through lenses scratched in an actual work environmen...

This paper presents an anatomically-correct eye model for the ground squirrel, a diurnal, highly-developed mammal with high visual acuity. This model can assist in understanding the relationship between ocular structural development and its corresponding function. The eye model is constructed based on anatomical measurements of thicknesses and indi...

The aim was to assess the impact resistance of coated and uncoated mid-index spectacle lens materials using the ballistic impact test. Nominally plano lenses of each material in three thicknesses were obtained. The lenses were flat edged to a 50 mm diameter. Each lens was impacted by a 6.35 mm steel ball. Impact velocities were selected using the Z...

Purpose: Tolerances required for ophthalmic lenses are set down in national and international standards. It appears that the compliance of manufactured lenses has not been reported previously. Assembling a statistical quantity of lenses of a single prescription is usually an expensive process. It was, secondary to a lens impact study, possible to...

Direct spectral transmittance data over the wave band 200–2500 nm were obtained for the ocular media of the thirteen-lined ground squirrel (Spermophilus tridecemlineatus) using a Zeiss (Oberkochen) DMR-21 dual-beam recording spectrophotometer. These data were used to calculate cumulative transmittance curves for each of the interfaces between optic...

Spectral transmittance of goldfish (n = 10) ocular media was measured in the 320- to 750-nm range with a spectrophotometer modified to eliminate problems associated with chromatic aberration and beam scattering. Absolute transmittance in the visible range was 0.8 at 400 nm and 0.95 at 750 nm. Transmittance below 400 nm dropped off to 0.3 at 340 nm...

The spectral transmittance of bluegill (Lepomis macrochirus) ocular media (n = 10 eyes) was measured over the wave band 310 to 750 nm, using a specially modified spectrophotometer. Transmittance was approximately uniform at 0.92 between 450 and 750 nm, fell to < 0.5 by 400 nm, and to 0.01 by 370 nm. The ocular media minimize exposure of the retina...

The David Dunlap Observatory (DDO) and the Royal Astronomical Society of Canada (RASC) are described. Included are a history of the observatory and the society, a description of the facility, and other important related events and notes.

This work involves the evaluation of UV blocking efficiency of commercially available intraocular lens (IOL) materials using a retinal cell culture and a biological in vitro model that was developed in a previous study, as an effort to examine the sensitivity of this in vitro approach for evaluating toxicity of UV radiation on the retinal pigment e...

The present study demonstrates narrowband short-wavelengths radiation- (400, 420, and 435.8 nm) induced cellular damage of cultured human retinal pigment epithelial cells using in vitro biological assays to determine wavelengths that are responsible for photochemical lesions of the retina. This work involved the exposure of retinal pigment epitheli...

To investigate how the impact resistance of Hoya Phoenix spectacle lenses is affected by centre thickness and the application of a multilayer antireflection (MAR) coating. Four groups of plano lenses were tested: dress thickness with scratch resistant (SR) coating on both surfaces, dress thickness with SR and MAR, industrial thickness with SR and i...

Previous work has shown that the impact resistance to blunt missiles is affected by coatings applied to either CR-39 or polycarbonate lenses. We investigated the effects of multiple antireflection (minimum angle of resolution [MAR]) coatings on the resistance of polycarbonate lenses to puncture on impact by sharp, high-speed missiles. Four groups o...

We discuss the design rationale and technological aspects of successfully commercially implemented development of high-precision extremely narrowband filters for solar and atmospheric applications and their use with telescopic instrumentation. The advantage of etalon-based filter technologies over other conventional approaches-such as interference...

To study the effect of coatings on the resistance of CR-39 industrial plano lenses to ballistic impacts and abrasion from fine particles. Twelve groups of CR-39 lenses with various scratch-resistant (SR) or combinations of scratch-resistant and antireflective (SR-AR) coatings were mounted in metal industrial spectacle frames. The ZEST protocol was...

Cell biology, as monitored with the fluorescent indicator dyes Alamar Blue and 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM), and lens optical quality, as measured with an in vitro scanning laser system, have been used to evaluate in vitro the condition of porcine lenses after being placed in a culture medium. The measurements, begin...

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. 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...

An attempt was made to provide on-line empirical real-time access to the local UV Index level and also to supplement it with answers to frequently asked eye and health related questions. Surveys revealed that individuals who are aware of and consult the UV Index tend to adopt recommended protective strategies.

The effect of coatings on resistance of CR39 industrial plano lenses to ballistic impacts and to abrasion from fine particles was studied. Abrasion resistance was ranked by the degree of haze observed by three independent observers.

We show that space-mirror experiments reflecting sunlight to Earth can produce resolved images having surface-brightness sufficient to damage human eyes looking through telescopes or binoculars.

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. We carried out radiometric measurements, and questionnaire survey in 4 university glassblowing laboratories, and 3 private studios. Th...

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...

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-glass...

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 pr...

Safe eclipse viewing is a continuing problem for both astronomers and eyecare providers. Too often, the astronomer's enthusiasm for encouraging the public to observe an eclipse is countered by health care providers who consider that even the most minimal risk of eye damage is unacceptable. The challenge is to dispel misconceptions which are commonl...

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...

There appears to be a measure of agreement about the reliability of corneal reflection pupillometers. However, we have not encountered any publication about the accuracy of these instruments. This is what we set out to investigate. For this purpose we fixed two ball bearings at distances varying from 55 to 70 mm, in 5 mm steps. Ten measurements of...

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...

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...

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...

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 brok...

Many lost-time industrial eye injuries are due to small highspeed particles striking the cornea. To investigate whether contact lenses would complicate such injuries, we exposed porcine eyes fitted in vitro with rigid, hydrogel, or no contact lens to iron filings suspended in a high-speed air jet. Postexposure evaluations of 11 control eyes and 23...

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...

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...

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 anoth...

To assess the effect of systemically administered photosensitizing drugs on the ocular tissues, one must consider the spectral transmittance of the ocular media, the site of drug uptake in the eye, the absorption spectrum of the photosensitizer, and the time required for metabolization or elimination of the drug. In this paper we will consider ocul...

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 chlor...

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 Cibaso...

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 Cibaso...

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. On...

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...

Spectral transmittance data over the waveband 200 to 2500 nm are presented for a selection of tinted ophthalmic lenses. Criteria for the prescription of tinted lenses are briefly discussed.

A case report on the Steele-Richardson-Olszewski syndrome is presented in this paper. The clinical findings are shown to be due to the physiological changes arising from progression of the disease. The low-vision aspects of this case and its disposition are also discussed.

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 i...