**4. Discussion**

It is possible to enhance the colour moderately and with degradation [17]. Use of a 4000 K light source with a Duv value of zero is preferable to enhance and comfortably view colour [3]. OCT measures the volume of pigment in a layer, the thickness of varnish layers, the voids and the depth of microcracks; when applied to cultural heritage it generates spectacular images [34].

The dependence between intensity, duration, pattern, timing, light history and wavelength can change the response of the circadian system. The photopic visual system responds equally to non-visual responses with high intensities [36]. The colour quality (CQ) attributes (naturalness, colour and preference) of light were assessed in immersive environments. Preference was related to naturalness and colour, however naturalness was weakly related to colour [6]. There was a high correlation of preference with perception. White light improved colour preference, comfort and discrimination [3,31]. Other behavioural variables decreased visual acceptance, including variations in subjective alertness, mood and inter-correlations of these dependent variables. Daylight availability was one of the indicators of individual satisfaction [35].

Protans and deutans have a preference for re-coloured images with enhanced contrast. This information makes it possible to design good visualisations in these cases [29]. WGR mixes produce more attractive colour images than do other types of lights [5].

Eyestrain symptoms and ocular surface symptoms increased tiredness and sleepiness. These visual functions represent a loss of image sharpness. Binocular accommodative facility decreased [19] and focus variation is less accurate.

Among myopics, there was a greater lag in schoolchildren than in young adults. This is therefore a problem of focus among schoolchildren, preventing unintentional maintenance of attention, especially in ametropia such as myopia; this was greater under mesopic room conditions for all ages. Good photopic lighting is necessary to avoid it. Accommodative lag and accommodative fluctuations at far distance (6 m) and near distance (25 cm) were measured using the Grand Seiko WAM-5500 open-field autorefractor [20].

For polychromatic white DOFi with colour versus monochromatisms, some visual aid is essential to relax the accommodative stimulus that colour variations require [21]. Increased effects related to the IOL diopter were observed, and MTF values were found to be increased with the increase in the IOL diopter [22]. This also affects populations of people with cataract surgery or with ametropia, where the lens is replaced by IOLs. Such people are mostly over 60 years of age. For bifocals, adding power produced changes in the near image quality in terms of wavelength and pupil size [23].

Finally, there is a large population with healthy eyes and those with different visual problems due to accommodation, binocular vision, intraocular lenses or pupils, that may not see a well-lit object well in any museum.
