Hospital Lighting: General and Medical Aspects

Abstract

The modern planning of hospital wards is contrasted with the old' Nightingale' pattern, and the main lighting requirements in hospitals are outlined. The problem of colour-rendering is presented, and details are given of tests made to determine the suitability of different light sources, for clinical observations, from which a specification for the chromaticity and colour-rendering requirements for a suitable lamp are derived.

The specification of color limits in eye protection lenses for use when color‐contingent clinical observations are made

“…The Crawford Figure of merit (a numerical value) and Crawford Class (a classification in the range A (perfect) to G 20–22 and the Ferguson–Crawford sum of excesses 25 were calculated by comparison with the reference P4000 K.…”

“…11 R 9 has become an unofficial measure of lighting for clinical observation and R 13 is specified in AS/NZS 1765, so these two values were also calculated. 30 The value of DC was compared with the limit set by the CIE. 11 The Crawford Figure of merit (a numerical value) and Crawford Class (a classification in the range A (perfect) to G [20][21][22] and the Ferguson-Crawford sum of excesses 25 were calculated by comparison with the reference P4000 K.…”

“…This was later redefined as an R a ≥ 85 23,24 in the CIE system, first introduced in 1965 11 . The MRC recommendation was tentative for jaundice and a member of the study panel later reanalyzed the data to make a more stringent recommendation that, in effect, included only the upper levels of Crawford Category B, thus implying greater effects of lighting on the recognition of jaundice than other conditions 25 . No more recent publications on hospital lighting have been found to address the issue of the recognition of jaundice in detail.…”

“…26 It would be logical to assume that the irradiance in the region of 475 nm would have an important influence on the visual ability to detect jaundice but only one study, which uses an outdated metric, gives any numerical clue to limits to be placed on the spectral irradiance of the light source or colorimetric measures. 25 In addition, it is evident that the color in cyanosis changes almost entirely in colorfulness [27][28][29] while in jaundice, it changes primarily in hue and less so in colorfulness. 27 It is possible that one of these dimensions is more sensitive to changes in the light source or tinted eyewear.…”

“…Consequently, there is little consistency in the acceptance of lighting for clinical observation. The primary differences being between those nominating a CCT around 4000 K (with the interpretation of "around" being quite variable) and the ANSI/IES recommendation that would exclude anything < 4000 K. Similarly, the color rendering index recommendations vary from R a ≥85 (dating back to the MRC study [19][20][21][22]24,25 ), ≥ 80 in general areas (as proposed by Lovett et al 27,32,33 ) and ≥ 90 in special areas. It is worth noting that the specification of a fixed reference CCT at 4000 K, as happens in the Crawford method, rather than comparing the sources with the reference of the same CCT, as happens in the CIE method, places indirect and greater constraints on the range of CCTs permitted.…”