## 1 Introduction  
Visual function refers to the complex process by which the visual system perceives, processes, and interprets visual information from the environment. Light that reaches the corneal plane passes through all refractive media until it reaches the retina, which transforms the light into nerve impulses to convey information to the occipital lobe of the brain through the optic nerve and the posterior visual pathways. However, the fact that light reaches the retina does not guarantee good vision, as this information must be transmitted via posterior visual pathways to the occipital cortex, where it is processed and analyzed. Cognitive tasks such as pattern identification, depth perception, and recognition of shapes and colors, as well as other specific tasks related to vision, are performed there [1]. The retina is the innermost neurosensory layer of the eyeball and is nonrished by the ophthalmic artery, which divides into several branches, including the central retinal artery that supplies the inner retina and the posterior ciliary arteries, which supply the outer retina, choroid, and sclera [2]. In the central region of the retina lies the macula lutea, the area with the highest density of photoreceptors and where the highest visual acuity (VA) is achieved. Specifically, vision is at its peak in the center of the macula, where many photoreceptors responsible for detailed color vision are found in the fovea [3, 4]. Photoreceptors are responsible for converting light stimuli into nerve impulses through the process of phototransduction. There are two types of photoreceptors: rods and cones [4; 5]. Rods account for approximately 95% of all photoreceptors and are characterized by their high sensitivity to light but low spatial resolution. In contrast, cones make up the remaining 5% of photoreceptors and provide high spatial resolution at the expense of sensitivity. Importantly, between 15 and 30 rods converge onto a single bipolar cell, whereas each cone is associated with a single bipolar cell, resulting in these differences in spatial resolution. Rods are responsible for functioning under scotopic light conditions, where color vision and detail perception are greatly reduced due to the low activity of cones. Scotopic vision is considered to occur when luminance is below 0.01 cd/m\({}^{2}\)[6]. Under high levels of illumination, known as photopic conditions, above 0.3 cd/m\({}^{2}\), cones are the dominant photoreceptors, as rods become saturated by excessive light. Traditionally, two of the most important tests for evaluating visual function are VA and contrast sensitivity (CS). VA is defined as the maximum spatial resolution capacity of the visual system for high-contrast stimuli, expressed mathematically as the inverse of the angle in minutes of arc subtended by the smallest detail of the optotype used [7]. The CS is defined as the inverse of the minimum contrast necessary to see an object, i.e., the inverse of the contrast threshold. If contrast thresholds are obtained for different spatial frequencies, the CS function is obtained, which reflects the detection capability of the visual system for any spatial frequency. For a standard subject, this function has an inverted U shape with a peak between three and six cycles per degree [7]. An objective way to describe the optical quality of visual function is through wavefront aberration. Wavefront aberration is the difference between the wavefront generated by the optical system and a reference spherical wavefront [8]. When an eye is free from aberrations, i.e., a perfect eye, a spherical wavefront forms ideal images on the retina. Thus, optical aberrations are defects in an optical system that prevent a clear and exact reproduction of the fixation object [8]. There are low-order aberrations (LOAs) (orders 0, 1, and 2) and high-order aberrations (HOAs) (order 3 and higher). Alertness is defined as a state where high sensitivity to incoming stimuli is achieved and maintained [9].