M.Phil. / Tinted spectacle lenses have long been worn to provide ocular protection from harmful electromagnetic radiation during recreational activities. Controversy exists surrounding the colour of the spectacle tints and the environmental conditions under which these tints are worn. There is little scientific evidence to substantiate the many opinions of authors on the effects of tinted spectacle lenses on visual skills and, ultimately, on overall performance in recreational situations. This study serves to provide scientific data concerning the effects of tinted lenses on static visual acuity, contrast sensitivity, colour vision, stereopsis and visual evoked potential (VEP). These results are related to the visible spectrum transmission curve for each experimental lens. recommendations are then made concerning the environmental conditions under which each lens tint should be worn. The HOYA ULT-2000 Light Transmission Metre was used to establish the percentage of visible light being transmitted through each of the experimental lenses. The DMS 80/90 Visible Spectrophotometer was used to generate a visible spectrum transmission curve for each of the 8 experimental lenses used in this study. 30 subjects (Group A) were randomly selected from the RAU student population for the assessment of the effects of tinted lenses static visual acuity, contrast sensitivity, colour vision and stereopsis. 10 students (Group B) were then randomly selected from the RAU student population for the assessment of the effects of tinted experimental lenses on visual evoked potential (VEP). The ametropic subjects in Groups A and B all wore their habitual spectacle or contact lens corrections throughout the testing procedure. The following lens tint colours were used: clear, black, grey, yellow, green, blue, red and pink. The subjects were evaluated binocularly without any tinted lens being worn, then through each of the 8 tinted experimental lenses (randomly presented). Results of the visual skills and VEP testing were analysed as follows: Group A: An average score was calculated for the results achieved on the static visual acuity, contrast sensitivity, colour vision and stereopsis tests when no experimental lenses were worn. This average was then compared to the average static visual acuity, contrast sensitivity, colour vision and stereopsis scores for each of the 8 experimental lenses. Group B: An average score was calculated for each of the amplitude and latency components of the VEP waveforms generated when no experimental lenses are worn. This average was then compared to the average amplitude and latency components generated when each of the 8 experimental lenses (as for Group A) are worn. Static visual acuity was assessed using a Snellen visual acuity letter chart at 6m. Contrast sensitivity was assessed using a Vistech VCTS 6500 Contrast Sensitivity Chart at 3m. Colour vision assessment was performed using the lshihara Colour Vision Test and the City University Colour Vision Test. The Random Dot Near Stereo Test was used to assess stereopsis. The Nicolet Pathfinder II was used to assess visual evoked potentials (VEPs). The results of this study show that the black, grey, yellow, green, blue, red and pink tinted lenses have a statistically significant influence on visual efficiency only when subjective methods (i.e. static visual acuity, contrast sensitivity, colour -vision and stereopsis) of visual efficiency assessment are used. The tinted lenses had little effect on visual efficiency when an objective means (i.e. VEP) of assessment was used, as there were no statistically significant differences between the lenses. The results of this research project indicate that the colour of the lens tint has little real effect on visual efficiency, when measured objectively. The effect of the lens tint is shown to be highly subjective. Tinted lens selection would therefore be based on personal preference and the amount of protection that the lens provides from harmful electromagnetic radiation. It can be concluded that no single lens tint is therefore suitable for all individuals under the same environmental conditions.

A study was undertaken to examine the major eye injury problems in industry, to determine the hazards that caused them, and to develop methods for improving industrial eye protection programs so as to reduce the incidence of eye injuries. The study was conducted in Alberta through the Occupational Health and Safety Division of Alberta Labour and the Alberta Workers' Compensation Board. A review of literature was performed to determine the status of eye protection programs, current epidemiological investigations and modes of protection, and to search for historical, legislative and cost benefit information. The project consisted of seven studies which were designed and carried out independently but, together, would provide a wide perspective concerning eye protection in industry. These studies were: a) A Review of W.C.B. Statistical Master File Data - which was concerned with a cumulative review of every eye injury claim received by the Workers' Compensation Board over the years 1974, 1975 and 1976. This included a review of Permanent disability claims, claims for lost work time and claims where only medical aid was required. b) A Review of Selected W.C.B. Personal Medical Files - which was concerned with the detailed review of eye injury claims from fifteen high eye injury risk industry classes. Each medical file was examined individually, paying particular attention to prevention-oriented information. c) A Survey of Occupational Health and Safety Officers - where thirty-one occupational health and safety officers (inspection personnel) were given an in-depth interview to obtain their perceptions and informed opinions on the nature of eye injury hazards, compliance factors, and the status of eye protection programs in industry. d) A Survey of Occupational Health and Safety Personnel - where questionnaires were sent to over six hundred persons in Alberta, identified as being involved in the provision of occupational health and safety services in industry. This included physicians, nurses, safety personnel, and persons in government. Questions were similar to those in Section c. e) A Review of the Minutes of Selected Joint Work Site Committees in Alberta - where the minutes of selected meetings concerning health and safety on the work site between management, the worker, and government, were analyzed to determine the extent of the unsolicited concern for eye injury prevention in companies which were known to have incurred a large number of eye injuries. f) A Review of Anecdotal Data - where several interviews were held with union and management representatives to determine the concern and need for eye injury prevention, and the development of eye protection programs at a policy level in industry. The comments and concerns of many other persons were also considered. g) A Review of Selected Site Visits to Industries in Alberta -where the researcher made six plant visits to better understand the conditions which lead to eye injuries and the problems in implementing preventive programs. It was found that industries involved in the manufacture or use of metal products, chemicals or construction materials were at high risk. More specifically, however, it was determined that certain occupational groups such as machinists, plumbers and pipefitters, welders, and mechanics were also at high eye injury risk. It was concluded that occupational classification and eye injury hazards should be treated as a basis to eye injury prevention. Injuries were found generally to occur most frequently among the young and inexperienced workers, while grinding and welding operations were found to be the most prevalent source of injury. Injuries occurred most often at certain times of the day, and there was some question of the effects of boredom and fatigue. It was found that there is a lack of knowledge and education concerning standards of eye protection and in the proper selection of the protector for the hazard. The physical strength of the protector was minor, however, in comparison to the need for better protector design and fitting of the device to the face of the worker. It was concluded that companies must be encouraged to develop eye protection policies as a basis to the provision of eye protection programs. A plan was recommended for the improvement of eye protection programs in industry. This included the presentation of a comprehensive eye protection program formulated through a review of literature on the subject, and the elucidation of a system of occupational vision care involving the interaction of all groups concerned with eye injury prevention in industry. / Medicine, Faculty of / Population and Public Health (SPPH), School of / Graduate