Ocular straylight
Encyclopedia
Ocular straylight is the unwanted effect of light spreading as seen by human eye
s, and caused by the eye itself, not by external factors. It is most easily visualized as the radiation seen spreading from a bright light source against a dark background. The typical practical example is an opposing car with headlights on at night. The disability glare caused by such a situation was found to correspond precisely to the effect of true light. As a consequence, disability glare was subsequently defined by this true light, called "straylight".
implantation is an effective treatment.
There are however many more, but less common causes for straylight problems:
Human eye
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...
s, and caused by the eye itself, not by external factors. It is most easily visualized as the radiation seen spreading from a bright light source against a dark background. The typical practical example is an opposing car with headlights on at night. The disability glare caused by such a situation was found to correspond precisely to the effect of true light. As a consequence, disability glare was subsequently defined by this true light, called "straylight".
Individual differences
Straylight can differ considerably between individuals. With aging, the crystalline lens of the human eye causes straylight to become worse. Lens extraction and artificial lensIntraocular lens
An intraocular lens is an implanted lens in the eye, usually replacing the existing crystalline lens because it has been clouded over by a cataract, or as a form of refractive surgery to change the eye's optical power. It usually consists of a small plastic lens with plastic side struts, called...
implantation is an effective treatment.
There are however many more, but less common causes for straylight problems:
- Diseases of the corneaCorneaThe cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
, e.g. Fuchs' dystrophyFuchs' dystrophyFuchs' dystrophy, also known as Fuchs' endothelial dystrophy, is a slowly progressing corneal disease that usually affects both eyes and is slightly more common in women than in men...
. - Lack of pigmentation, e.g. albinismAlbinismAlbinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin...
. - Laser refractive surgeryPhotorefractive keratectomyPhotorefractive keratectomy and Laser-Assisted Sub-Epithelial Keratectomy are laser eye surgery procedures intended to correct a person's vision, reducing dependency on glasses or contact lenses. The first PRK procedure was performed in 1987 by Dr. Theo Seiler, then at the Free University...
, with occasional haze formation. - Excessive floaterFloaterFloaters are deposits of various size, shape, consistency, refractive index, and motility within the eye's vitreous humour, which is normally transparent. At young age the vitreous is perfectly transparent, but during life imperfections gradually develop. The common type of floater, which is...
s in the vitreous humourVitreous humourThe vitreous humour or vitreous humor is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates...
. - Contact lensContact lensA contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...
es.