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Bjerrum's Area
Bjerrum's area is the central 25° of the visual field from the fixation point, popularized scientifically by the Danish ophthalmologist Jannik Petersen Bjerrum. Bjerrum believed that this central portion of the visual field was of far more often use than the perimeter of the visual field, since he had observed 90% of the early glaucomatous changes were within these 25°. Multiple types of scotomas form inside Bjerrum's area, typically in patients with open-angle glaucoma. Of particular note is the arcuate scotoma (also known as the Bjerrums scotoma). It starts at the blind spot, arching over the macular area, and ends as a horizontal line nasally. The arcuate scotoma does not cross the horizontal divide of the visual field The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a point .... Ref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Field
The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments". Or simply, visual field can be defined as the entire area that can be seen when an eye is fixed straight at a point. The equivalent concept for optical instruments and image sensors is the field of view (FOV). In optometry, ophthalmology, and neurology, a visual field test is used to determine whether the visual field is affected by diseases that cause local scotoma or a more extensive loss of vision or a reduction in sensitivity (increase in threshold). Normal limits The normal (monocular) human visual field extends to approximately 60 degrees nasally (toward the nose, or inward) from the vertical meridian in each eye, to 107 degrees temporally (away from the nose, or outwards) from the vertical meridian, and approximately 70 degrees above and 80 below the horizontal meridian. The binocular visual field is the superimposition of the two monocular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophthalmology
Ophthalmology ( ) is a surgical subspecialty within medicine that deals with the diagnosis and treatment of eye disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a medical degree, a doctor specialising in ophthalmology must pursue additional postgraduate residency training specific to that field. This may include a one-year integrated internship that involves more general medical training in other fields such as internal medicine or general surgery. Following residency, additional specialty training (or fellowship) may be sought in a particular aspect of eye pathology. Ophthalmologists prescribe medications to treat eye diseases, implement laser therapy, and perform surgery when needed. Ophthalmologists provide both primary and specialty eye care - medical and surgical. Most ophthalmologists participate in academic research on eye diseases at some point in their training and many include research as part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jannik Petersen Bjerrum
Jannik Petersen Bjerrum (26 December 1851 – 2 July 1920) was a Danish ophthalmologist who was a native of Skærbæk, a town in the southernmost part of Jutland. In 1864 Skærbæk became part of Germany due to consequences of the Second Schleswig War. In 1876 he received his medical doctorate from the University of Copenhagen, and in 1879 became an assistant to Edmund Hansen Grut (1831-1907) at the Havnegade eye clinic. After Grut's retirement in 1896, he became director of the clinic, as well as being the second professor of ophthalmology at the University of Copenhagen, a position he would maintain until his retirement in 1910. Bjerrum made contributions regarding pathogenetic research of glaucoma, and performed extensive investigations involving campimetry. He was interested in the correlation between visual perception of form and the resolving power in localized regions of the retina. He was particularly focused on the subtleties of the central 30° of the visual field ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glaucoma
Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye remains open, with less common types including closed-angle (narrow angle, acute congestive) glaucoma and normal-tension glaucoma. Open-angle glaucoma develops slowly over time and there is no pain. Peripheral vision may begin to decrease, followed by central vision, resulting in blindness if not treated. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from glaucoma, once it has occurred, is permanent. Eyes affected by glaucoma are referred to as being glaucomatous. Risk factors for glaucoma include increasing age, high pressure in the eye, a family history of glaucoma, and use of steroid medication. F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scotoma
A scotoma is an area of partial alteration in the field of vision consisting of a partially diminished or entirely degenerated visual acuity that is surrounded by a field of normal – or relatively well-preserved – vision. Every normal mammalian eye has a scotoma in its field of vision, usually termed its blind spot. This is a location with no photoreceptor cells, where the retinal ganglion cell axons that compose the optic nerve exit the retina. This location is called the optic disc. There is no direct conscious awareness of visual scotomas. They are simply regions of reduced information within the visual field. Rather than recognizing an incomplete image, patients with scotomas report that things "disappear" on them. The presence of the blind spot scotoma can be demonstrated subjectively by covering one eye, carefully holding fixation with the open eye, and placing an object (such as one's thumb) in the lateral and horizontal visual field, about 15 degrees from fix ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blind Spot (vision)
A blind spot, scotoma, is an obscuration of the visual field. A particular blind spot known as the ''physiological blind spot'', "blind point", or ''punctum caecum'' in medical literature, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through the optic disc.Gregory, R., & Cavanagh, P. (2011)"The Blind Spot" Scholarpedia. Retrieved on 2011-05-21. Because there are no cells to detect light on the optic disc, the corresponding part of the field of vision is invisible. Processes in the brain interpolate the blind spot based on surrounding detail and information from the other eye, so it is not normally perceived. Although all vertebrates have this blind spot, cephalopod eyes, which are only superficially similar, do not. In them, the optic nerve approaches the receptors from behind, so it does not create a break in the retina. The first documented observation of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
