Visual Task Analysis (Dentist) PDF

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Summary

Summary for the VTA of a Dentist....

Description

Visual Task Analysis (Dentist) Aims: • •

To introduce you to the objectives of visual task analysis. To perform visual task analysis of dentist occupation.

Objectives: 1. 2. 3. 4.

VTA produces “visual specification’ for a particular task. VTA helps to avoid accidents caused by “compromised” vision. VTA helps to avoid expensive training of potential workers with inadequate visual capabilities. VTA leads to the realization of modest changes in the visual task, such as lighting, contrast, or the provision of optical aids, which could reduce the visual load and improve efficiency. 5. VTA helps in the design of training procedures for new personnel. 6. VTA assists in the prescription of optimal aids for the activities of prime interest to the patient involved. 7. VTA considers also non-visual factors. Fatigue associated with a particular task originates from non-visual factors such as seating, temperature, ventilation, work breaks and work station design.

Factors determining Visual Efficiency 1. Adaptation effects (light / dark / glare) 2. Time taken to respond 3. Flicker (strobe effect) 4. Position in visual field 5. Viewing distance a) accommodation b) convergence 6. Visual subtense of task detail (size/acuity) 7. Motion of task

8. Contrast of task detail 9. Colour of task 10. Clarity of task detail 11. Stereopsis requirements 12. Visual field requirements

13. Hazards 14. Training requirements

1. Adaptation effects (light / dark) adaptation Light adaptation is an important factor. Subjects who have poor light adaptation will operate inefficiently in this environment. (Condition that will affect poor light adaptation: Photophobia – caused by being an albino.) Glare can cause reduced efficiency.

1. Adaptation effects (glare) Glare is light in the wrong place: The discomfort or impairment of vision experiences when parts of the visual field are excessively bright in relation to the general surroundings. Classified into 2 main types: Disability glare:

Discomfort glare:

This prevents the detection of important details and causes serious loss of visual efficiency (plus discomfort). This is most likely to occur when there is an area of high luminance close to the line of sight.

This is the commonest type of glare, and causes annoyance, but no serious loss of visual efficiency. It is often only apparent after prolonged exposure.

Problem: • Reduces contrast ➔ Causing a washout – the whole scene looks grey Like discomfort, the disability glare is often reduced by increasing the light level. Think about a car’s headlights on full during the day; there’s lots more light, and as a result, the car’s headlights are less of a problem.

When a portion of the visual field has a much higher luminance than its surround, a feeling of discomfort around the eyes and brow may occur. This increases with an increase in the luminance of the glare source, and with an increase in the angular size of the glare source at the eye, and decreases with an increase in the luminance of the background with an increase in the angular position of the source relative to the line of sight.

Direct glare – when the origin is a bright source. Reflected glare – when light is reflected from specular or mirror-like surfaces. Adaptive glare – the range of luminance in the visual field is too great to be acceptable to the eye at any one level of adaptation. Successive glare – occurs as the subject moves from relative darkness to brightness or vice versa. The visual system takes time to adapt to its new conditions. Veiling glare – reflections are superimposed on the object of regard. 2. Time taken to respond Space scotoma does not exist → The dentist is operating at very close distances in a static environment. 3. Flicker Tools rotate at very high speeds and stroboscopic effects are likely to be slight. 4. Position in visual field / visual field size The work requires exclusively foveal vision (parvocellular pathway). Good oculomotor control is required.

5. Viewing distance a) Accommodation Dentist works predominantly with near vision. The dentist may require a near addition in the presbyope to provide the necessary range of vision. Viewing distance - 30cm (from behind to look at upper teeth) & 40cm (infront of patient for lower teeth) b) Convergence Due to the large amount of time spent with near vision, a large bifocal or trifocal segment may be required. This should be wide, and set quite high. If the dentist suspends his x-ray photographs from the operating lamp, and intermediate near addition in the upper part of the lens may be of use. Because of the very close working distance for the top teeth, a good convergence amplitude is required. 6. Visual subtense of task detail (size/acuity) The dentist must have good acuity in order to see the fine details of teeth, and good visuomotor control to use small instruments in a small space. 7. Motion of task There is little or no motion involved in the task that the dentist is performing. 8. Contrast of task detail Contrast of task detail might be slow – esp when looking for subtle changes in tooth or gum colour. 9. Colour of task Important for selecting the correct formulation of material to match the filling / crown to the natural colour of the patient’s teeth. Illumination from the lamp should have a high colour rendering index. Ultra-violet used, if viewed directly, can cause distortions in the dentist’s colour perception for subsequent patients. 10. Clarity of task detail The task detail should be sharp. Clarity of task detail can be impaired during drilling by the fine mist of water vapour and fragments of material that are produced from the teeth. 11. Stereopsis requirements Stereopsis is very important for a dentist, who is operating on small objects in three dimensions and in a restricted space. Excellent oculo-motor control is needed. 12. Visual field requirements The area that the dentist uses in his normal work is restricted. Therefore there is no special requirement for extensive visual field.

13. Hazards ➔ from flying particles during drilling and buffing of teeth. Ocular protection (plastic safety lenses or goggles) is advisable. ➔ Ultra-violet light (potential radiation hazard to the eye) Should use yellow shields, plastic safety lenses or goggles to absorb ultra-violet light. Areas of dental care to take note: 1. Cavity removal 2. Curing, or hardening bonding materials 3. Whitening teeth 4. Periodontal care 14. Training requirements The training of a dentist is very extensive and must help him/her in the performance of his/visual tasks....