**1. Introduction**

The human eye detects light at wavelengths between 400 and 700 nm, the visible band. There are three kinds of colour-sensitive pigments for absorbing energy in this range, which allow the eyes to see [1]. There are different tests to evaluate colour fidelity indices (CIE-Ra, CQS-Qf, CRI2012, CRI-CAM02UCS, and IES-Rf). Prediction is better with CIE-Rf than with CIE-RaFew [2].

In this paper, the appearance of objects in a museum situation with different spectral power distributions was investigated [3,4]. Other studies have analysed relative attractiveness, naturalness and preference for exhibits in correlation with colourfulness. All differences were compared based on the realisation of different targets for light emitting diode (LED) blending and standard light sources [5–7].

It is easy to find different evaluations of perceptions of LED-based white-light sources in persons of different ethnicity with different objects (fresh food, packaging material or skin tone) [8–11]. The colour perception of an object is little influenced by the neutral interior of a light booth [12]. This usually involves judging brightness, colourfulness and pleasantness when lit with pre-set spectra with correlated colour temperatures (CCTs) via LED and fluorescent lights, in approximately 500 lx. The lighting choices did not differ based on individuals' selections, ranging (2850 to 14,000 K) and lying slightly below the blackbody curve [7,13]. Other attributes did, however, have an impact on perception: attraction, vividness and warmth [14].

The spectral region around 570–580 nm is deleterious to the perception of colour and brightness [15]. High-quality LEDs can improve observers' perceptions and can make the colour appearance more vivid and saturated [16]. With colour LEDs, the hue and the saturation of a target colour can be modified according to preference [17].

Smartphone and tablet use are associated with visual and ocular discomfort such as headaches, eyestrain and other symptoms; this is also reported with desktop computer use. Smartphones, tablets and similar devices differ from desktop computers in position and distance, screen size and luminance. It is important to know that accommodations decrease with handheld device use, lag increases and is induces changes in convergence [18,19]. These changes in accommodation and convergence for near items in inadequate lighting conditions are implicated in the evolution of myopia. There is greater accommodative lag in myopes than in emmetropes and in schoolchildren than in adults [20]. Longitudinal chromatic aberration is related to this accommodation and changes in the emmetropisation process and the change of the depth of field (DOFi). This state causes a dioptric change in the monochromatic accommodation response [21]

Intraocular lenses (IOLs) with more diopters are problematic in that their central thickness and aberrations reduce image quality [22]. In measuring the quality of a polychromatic image using IOLs, a model eye was constructed with diffractive optical elements. Image quality was evaluated for vergences, lengths and pupil modulation transfer functions and image quality. There was a significant modification in the near-distance balance [23].

It is possible that changes in colour are observed when pictures are viewed by one eye with any surface defects? These aberrations could be caused by opacity or trauma in any of the elements in front of the retina, although it can also be produced in the retina itself. Cone defects are directly related to colour failure. Can original colour be recovered by modifying the picture viewed by that eye? With another functional eye problem, would it be possible to visualise the original colour with adequate irradiation?
