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The irises of human eyes exhibit a wide spectrum of colours. Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye's iris [1] [2] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. [3]: 9
Emmetropia is the state of vision in which a faraway object at infinity is in sharp focus with the ciliary muscle [1] in a relaxed state. That condition of the normal eye is achieved when the refractive power of the cornea and eye lens and the axial length of the eye balance out, which focuses rays exactly on the retina, resulting in perfectly sharp distance vision.
A cone monochromat can have good pattern vision at normal daylight levels, but will not be able to distinguish hues. As humans typically exhibit three classes of cones, cone monochromats can hypothetically derive their photopic vision from any one of them, leading to three categories of cone monochromats: [ 4 ]
Between these extremes is the pupil diameter that is generally best for visual acuity in normal, healthy eyes; this tends to be around 3 or 4 mm. If the optics of the eye were otherwise perfect, theoretically, acuity would be limited by pupil diffraction, which would be a diffraction-limited acuity of 0.4 minutes of arc (minarc) or 6/2.6 acuity.
The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic). [3] In humans, an increase of melanin production in the eyes indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia. The term is derived from Ancient Greek: ἕτερος, héteros "different" and χρῶμα, chrôma "color ...
In normal population the dominant aberrations are the ordinary second-order spherocylindrical focus errors, which are called refractive errors. Higher order aberrations are a relatively small component, comprising about 10% of the eye's total aberrations. [ 3 ]
Turns out, your eyes speak. Skip to main content. 24/7 Help. For premium support please call: 800-290-4726 more ways to reach us. Sign in. Mail. 24/7 Help. For premium support please call: ...
Brushfield spots are small, white or greyish/brown spots on the periphery of the iris in the human eye due to aggregation of connective tissue, a normal constituent of the iris stroma. The spots are named after the physician Thomas Brushfield, who first described them in his 1924 M.D. thesis. [1]