Binasal hemianopsia is the medical description of a type of partial

blindness Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

where vision is missing in the inner half of both the right and left visual field. It is associated with certain lesions of the eye and of the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

, such as congenital

hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased intracranial pressure, pressure inside the skull. Older people may have headaches, double vision, poor ...

Causes

In binasal hemianopsia, vision is missing in the inner (nasal or medial) half of both the right and left visual fields. Information from the nasal visual field falls on the temporal (lateral) retina. Those lateral retinal nerve fibers do not cross in the optic chiasm. Calcification of the internal carotid arteries can impinge the uncrossed, lateral retinal fibers, leading to loss of vision in the nasal field. Clinical testing of visual fields (by confrontation) can produce a false positive result, particularly in inferior nasal quadrants.

Management

Etymology

The absence of

vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain un ...

in half of a

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 ...

is described as ''

hemianopsia Hemianopsia, or hemianopia, is a loss of vision or blindness (anopsia) in half the visual field, usually on one side of the vertical midline. The most common causes of this damage are stroke, brain tumor, and trauma. This article deals only wi ...

''. The absence of visual perception in one quarter of a visual field is described as ''

quadrantanopsia Quadrantanopia, quadrantanopsia, refers to an anopia (loss of vision) affecting a quarter of the visual field. It can be associated with a lesion of an optic radiation. While quadrantanopia can be caused by lesions in the temporal and parieta ...

''. The visual field of each eye can be divided in two vertically, with the outer half being described as ''temporal'' or ''lateral'', and the inner half being described as ''nasal''. "Binasal hemianopsia" can be broken down as follows: *''bi-'': involves both left and right visual fields *''nasal'': involves the nasal visual field *''hemi-'': involves one-half of each visual field *''

anopsia An anopsia () is a defect in the visual field. If the defect is only partial, then the portion of the field with the defect can be used to isolate the underlying cause. Types of partial anopsia: * Hemianopsia ** Homonymous hemianopsia ** Heteron ...

'': blindness

References

External links

{{DEFAULTSORT:Binasal Hemianopsia Blindness Visual disturbances and blindness

Causes

Management

Etymology

See also

References

External links