## 1 Introduction
These effects are related to SPD, spatial distribution in a room (light in the upper hemisphere of the FOV is more effective), and temporal distribution or photoperiod (dynamic light; the right light at the right time) [18]. The third proposal, the WELL Building Standard, offers lighting guidelines to provide appropriate photopic and scotopic light levels, minimize disruption to the body's circadian system, and support good sleep quality. Feature 54: Circadian lighting design recommends as an approximation a parameter known as equivalent melanopic lux (EML), which is one of the five \(\alpha\)-opic illuminance outputs used as criteria for \"circadian lighting design\", with reference to the equi-energy illuminant instead of D\({}_{65}\)[19]. Broadly, visual function is widely studied with common illumination systems. The emergence of light-emitting diode (LED) systems and screen devices that are widely used represents a revolution in environmental conditions. LEDs have been used as replacements for other traditional lamps, such as incandescent, fluorescent, or high-intensity discharge bulbs. The CCT, CRI, Fidelity Index (Rf), Relative Gamut Index (Rg), Local Chroma Shift (Rcs,hj(%)), and Local Color Fidelity (Rf,hj) are parameters used to quantify different objective aspects of color rendition, including average color fidelity and gamut area, as well as 16 values (j from 1 to 16) each for hue-specific chroma shift, hue shift, and color fidelity in lighting devices [20; 21]. Recently, several measuring experimental setups have been described for standardizing lighting experiments given the variability in the lighting results [22; 23; 24]; in addition, scholars have discussed the complexity of lighting design, described potential effects that should be considered by researchers [25], and reported the physiological and seasonal changes that can occur [10; 26]. To improve both visual and nonvisual effects in lighting projects, it seems that SPD optimization is required. Standards (CIE) and recommended practices (WELL) or the recent UL DG 2448022 (which is not a consensus (ANSI) document) [27] for lighting design have been developed and will play an important role in architectural projects, scientific studies, and understanding human behavior, although these methodological suggestions should be treated with caution and only standards should be recommended. It is important to be able to avail oneself of metrics and other guidance when designing projects and evaluating project performance, both with respect to visual and nonvisual effects. In this paper, we use different models to investigate the spectral optimization of LED sources in terms of SPD at corneal-level light exposure and to compare these results with those of other metrics. The research is conducted using a simple protocol that should enable even novice designers to develop lighting projects using the basic parameters related to the visual path and performance (present in current lighting standards) and the new parameters (non-visual path) referenced in recommendations based on the WELL, CIE, or Rea et al. models, all of which are normally based on irradiance (or melanopic illuminance) in the plane of the pupil of the eye. The novelty of the paper is the proposed method,in which both photopic and melanopic contributions can be easily quantified and interrelated between current metrics, applying it to a group of commercial LEDs and a lighting project. In this initial approximation, it is assumed that the materials of the luminaires and walls of the rooms do not modify the SPD of the vertical illumination that reaches the corneal plane.