Visual acuity standards for Beach Lifeguards

TitleVisual acuity standards for Beach Lifeguards
Publication TypeConference Paper
Year of Publication2007
AuthorsTipton, MJ, Scarpello, E, Dr. Reilly, T, McGill, J
Conference NameWorld Conference on Drowning Prevention
Date Published09/2007
PublisherInternational Life Saving Federation
Conference LocationPorto, Portugal
Other Numbers03-26
Abstract

­Context: We have determined the visual acuity required by beach lifeguards (BLG) in order to identify a human head at the outer edge of a patrolled area of 300m out to sea. The required visual acuity as determined by the angle subtended by a human head at this distance would be 6/17, but due to location and detection factors we hypothesised that it would have to be better than this.

Methods: The experiment received ethical approval and twenty-one BLG (16 male, 15 female, all under 35 years) gave their consent to participate. Following eye tests to ensure normal vision (mean [range] visual acuity 6/4.8 [6/3.8-6/5]), they undertook a series of tests on two beaches in the UK, during which their vision was blurred (to 6/70 using spherical lenses) to a visual acuity at which they could not identify human heads or equivalent sized buoys. The subjects looked out to sea or across a wet beach and their visual acuity was improved every minute by reducing the refractive blur in 0.25 dioptre increments until they could identify the target to the point at which they would investigate it further using binoculars. The tests were performed on the same day, in good weather, uniform lighting conditions and a sea state of 0-1 (calm).

Results:
Table 1. Results from Bournemouth (B) and Westward Ho! (W)

Condition
LogMARMean (SD)
Snellen

(i) B: locate and identify a human head within a 300m radius out to sea (volunteer immersed to neck)
0.11(0.06)
6/8

(ii) W: locate and identify a human head within a 300m radius out to sea (volunteer immersed to neck)
0.06 (0.17)
6/7

(ii) B: identify an arm waving at 300m in the sea (volunteer immersed to neck)
0.33 (0.16)
6/13

(iii) B: identify a human immersed to the waist at 300m in the sea
0.74 (0.15)
6/33

(iv) B: locate and identify a human head within a 100m radius out to sea (volunteer immersed to neck)
0.86 (0.23)
6/43

(ii) W: identify a buoy at 200m out to sea (n=8)
0.28 (0.18)
6/11

(iii) W: identify a buoy at 100m out to sea (n=8)
0.78 (0.25)
6/36

(iv) W: identify a buoy on the wet beach at 300m
0.23 (0.19)
6/10

(v) W: identify a buoy on the wet beach at 200m
0.48 (0.13)
6/18

(vi) W: identify a buoy on the wet beach at 100m
0.87 (0.15)
6/44

Discussion: The differing ability of individuals to adjust to the lenses, and the central processing required to search, see and identify a head in the sea probably explains why the visual acuity required to see a human head at 300m in the sea was 6/7, rather than the theoretical figure of 6/17. We therefore accept the hypothesis. It is recommended that a BLG should have visual acuity of 6/7 or better. As this will exclude some individuals, consideration could be given to allowing BLG to wear glasses. As the visual acuity required to maintain sight of a casualty is less than that required to locate/detect them in the first place, it is reasonable to require a BLG to have uncorrected vision, in their worst eye, that is at least equivalent to that required to see a head from 200m-300m distance, or an arm waving from 300m. The average for these activities is 6/14. In terms of the Snellen chart, we recommend that the corrected vision for BLG be 6/9 best eye, 6/18 worst eye, and the unaided acuity be no worse than 6/18 in either eye.

Learning Outcomes
  1. Because the incidence of spinal injury is relatively low and the effect of insufficient treatment severe, frequent training is required
  2. Governments should supply lifesaving organizations with oxygen (equipment). An immediate start with the oxygen treatment will improve survival
  3. Research is needed to determine whether survival improves when lifeguards use an airway device like the laryngeal tube or the combitube
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