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The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors. [3]
A person's visual acuity is registered documenting the following: whether the test was for distant or near vision, the eye(s) evaluated and whether corrective lenses (i.e. glasses or contact lenses) were used: Distance from the chart D (distant) for the evaluation done at 20 feet (6 m). N (near) for the evaluation done at 15.7 inches (400 mm).
Converging lenses have positive optical power, while diverging lenses have negative power. When a lens is immersed in a refractive medium, its optical power and focal length change. For two or more thin lenses close together, the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens: P = P 1 ...
Blue light has also been blamed for eye strain and discomfort. As a result, people have been shelling out for blue light-filtering spectacles in hopes of snoozing in peace and reducing visual fatigue.
If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human (and much of animal vision) is the visual field. [2] It is defined as "the number of degrees of visual angle during stable fixation of the eyes". [3] Note that eye movements are excluded in the visual field's definition.
Eyewear is a term used to refer to all devices worn over both of a person's eyes, or occasionally a single eye, for one or more of a variety of purposes. Though historically used for vision improvement and correction, eyewear has also evolved into eye protection, for fashion and aesthetic purposes, and starting in the late 20th century ...
It's not recommended to use the massager for any longer than 20 minutes at a time — the manufacturer warns that anyone with cataracts, glaucoma, retinal conditions or has undergone eye ...
Adjustable focus lenses, like single-focus lenses, also reduce image-jump and spatial distortion in the field of view associated with traditional multi-focal lenses. Additionally, the ideal near-vision correction can be achieved with precision, because the variable lenses emulate the focusing action of the youthful (non-presbyopic) eye.