Photometry in the workplace: the rationale for a new method.

OBJECTIVES: The assessment of lighting conditions in workplaces has traditionally focused on the measurement of illuminance. The rationale for a new method for the detailed evaluation of natural and artificial light in 'near work' situations, involving the assessment of luminance, is described. METHODS: The procedure comprises four successive phases: (1) identify object/images observed during work tasks; (2) outline the area of the operator's visual field where gaze is predominantly directed; (3) measure luminances in the visual field, pin-pointing all sources of primary and secondary luminance, and constructing iso-luminance maps; and (4) compare luminance ratios. RESULTS: The procedure was illustrated using the common example of near work in an office environment. Illuminance was found to be inadequate to evaluate the effects of natural and artificial environmental light in the workplace. This is due to the fact that the luxmeter is designed to integrate the light detected over a large angle, whereas in near work the operator's retina is mainly stimulated by light originating from objects/images placed in the occupational visual field. CONCLUSIONS: A detailed measurement of luminance within the occupational visual field is consistent with ocular anatomy and physiology, and can be used as part of a risk assessment for visual disturbances and to rationalize lighting at workstations.

[Occupational ophthalmology and ergoophthalmology: a developing field]. / Oftalmologia occupazionale ed ergoftalmologia: un percorso in evoluzione.

In 1979 it was decided to activate, within the Institute of Occupational Health of the Milan "Università degli Studi", a new Unit of Ergophthalmology. This decision was taken owing to the progressive diffusion of "optical instruments", particularly computer-based equipment, in the world of work and to the relevance that this topic assumed among Italian occupational physicians. Since its beginning, one of the main characteristics of the Ergophthalmology Unit was an interdisciplinary approach, where occupational physicians, ophthalmologists, occupational hygienists and lighting engineers were collaborating on a daily basis. Research activities, which developed over many years and in several phases, were concerned with four main topics: 1. analysis and quantification of "near work load"; initially the investigations were mainly aimed at the evaluation of the observation distance in different tasks, followed by the development of a method which, by means of specifically designed electronic equipment, allows quantification of the accommodation and convergence required by the task; 2. development of a new method aimed at evaluating, by a photometric procedure, the luminance ratios in the "occupational visual field"; this research was carried out, both in the laboratory and during on-site investigations, in collaboration with the Dept. of Electrotechnics of Milan Polytechnic; 3. studies on the relationships between indoor microbial pollution and Computer Assisted Design work, considering that ocular conjunctiva and cornea, due to their external position, can be easily inoculated by micro-organisms present on periocular tissue and hands; this research showed that bacteria and fungi pathogenic for the eye (Staphylococcus aureus, Candida sp., Aspergillus sp.) are present on desk, keyboard and mouse, as well as in the conjunctival sac of the exposed operators; 4. studies on "blue light" and its effects on the Pigmented Retinal Epithelium (PRE) in workers exposed to halide lamps, like electricians, installers, maintenance staff, polymerization operators, etc.; the laboratory and on-site investigation that was carried out in cooperation with the Health Physics Dept. of the Milan ICP Hospital, showed that long-term exposure to low levels of irradiation could constitute an eye risk for these working populations.

Observation distance and blinking rate measurement during on-site investigation: new electronic equipment.

Modern work activities often require an intense and prolonged visual effort on near objects. At the same time, occupational asthenopia caused by accommodation and binocularity overloading is a very common complaint in these working populations. Moreover, blinking rate seems to be a sensitive parameter with 'indoor-near-work operators', possibly increased by both chemical and physical environmental agents and decreased by cognitive effort. In this paper, a new piece of electronic equipment used to measure the observation distance and blinking rate is described.

Viewing distance variation and related ophthalmological changes in office activities with and without VDUs.

This experimental study was conducted on 14 volunteer female clerks to measure viewing distance variation and related ophthalmological changes in office activities with (session 1) and without (session 2) VDU. A video camera connected to an electronic elaborator was used to determine eye-screen distance of the VDU operators during the task. Before and after each of the two work sessions far refraction, far phorias, near point of accommodation (APP), and fusional convergence were measured. Blinking rate of each subject was measured by a transducer only during the "VDU session'. The objective measurements of the eye-screen distance, whose range was between 48.42 and 65.33 cm, allowed a precise quantification of the occupational visual load during session 1. The accommodation was about 1.5-2D on average and the fusional convergence 10-13 delta on average. The symptomatology shows a number of disturbances in session 1 (71.4%) clearly higher than in session 2 (35.7%). The study of refraction before and after the task has shown a slight excess of accommodation compared to the theoretical value in both sessions, more marked in session 1. The APP shows no statistical significative variation. A tendency to exophoria was registered at the beginning and at the end of the trial and the fusional convergence clearly decreased, especially in the first session.