Visual acuityVisual acuity (VA) commonly refers to the clarity of vision, but technically rates a person's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye influence the sharpness of an image on its retina. Neural factors include the health and functioning of the retina, of the neural pathways to the brain, and of the interpretative faculty of the brain. The most commonly referred-to visual acuity is distance acuity or far acuity (e.g.
Visual impairmentVisual 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 corrective eyewear, assistive devices, and medical treatment– visual impairment may cause the individual difficulties with normal daily tasks including reading and walking. Low vision is a functional definition of visual impairment that is chronic, uncorrectable with treatment or conventional corrective lenses, and impacts daily living.
Systematic reviewA systematic review is a scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from published studies on the topic, then analyzes, describes, and summarizes interpretations into a refined conclusion. For example, a systematic review of randomized controlled trials is a way of summarizing and implementing evidence-based medicine.
RadiosurgeryRadiosurgery is surgery using radiation, that is, the destruction of precisely selected areas of tissue using ionizing radiation rather than excision with a blade. Like other forms of radiation therapy (also called radiotherapy), it is usually used to treat cancer. Radiosurgery was originally defined by the Swedish neurosurgeon Lars Leksell as "a single high dose fraction of radiation, stereotactically directed to an intracranial region of interest".
Visual systemThe visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the ability to detect and process visible light) as well as enabling the formation of several non-image photo response functions. It detects and interprets information from the optical spectrum perceptible to that species to "build a representation" of the surrounding environment.
Sixth nerve palsySixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI (the abducens nerve), which is responsible for causing contraction of the lateral rectus muscle to abduct (i.e., turn out) the eye. The inability of an eye to turn outward, results in a convergent strabismus or esotropia of which the primary symptom is diplopia (commonly known as double vision) in which the two images appear side-by-side. Thus, the diplopia is horizontal and worse in the distance.
Infant visual developmentInfant vision concerns the development of visual ability in human infants from birth through the first years of life. The aspects of human vision which develop following birth include visual acuity, tracking, color perception, depth perception, and object recognition. Unlike many other sensory systems, the human visual system – components from the eye to neural circuits – develops largely after birth, especially in the first few years of life. At birth, visual structures are fully present yet immature in their potentials.
Stereoscopic acuityStereoscopic acuity, also stereoacuity, is the smallest detectable depth difference that can be seen in binocular vision. Stereoacuity is most simply explained by considering one of its earliest test, a two-peg device, named Howard-Dolman test after its inventors: The observer is shown a black peg at a distance of 6m (=20 feet). A second peg, below it, can be moved back and forth until it is just detectably nearer than the fixed one. Stereoacuity is defined as the minimum angle detectable, calculated as the difference between the angles subtended by both positions, A and B.
Stereotactic surgeryStereotactic surgery is a minimally invasive form of surgical intervention that makes use of a three-dimensional coordinate system to locate small targets inside the body and to perform on them some action such as ablation, biopsy, lesion, injection, stimulation, implantation, radiosurgery (SRS), etc. In theory, any organ system inside the body can be subjected to stereotactic surgery. However, difficulties in setting up a reliable frame of reference (such as bone landmarks, which bear a constant spatial relation to soft tissues) mean that its applications have been, traditionally and until recently, limited to brain surgery.
Radiation therapyRadiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radiation therapy may be curative in a number of types of cancer if they are localized to one area of the body. It may also be used as part of adjuvant therapy, to prevent tumor recurrence after surgery to remove a primary malignant tumor (for example, early stages of breast cancer).
Visual agnosiaVisual agnosia is an impairment in recognition of visually presented objects. It is not due to a deficit in vision (acuity, visual field, and scanning), language, memory, or intellect. While cortical blindness results from lesions to primary visual cortex, visual agnosia is often due to damage to more anterior cortex such as the posterior occipital and/or temporal lobe(s) in the brain.[2] There are two types of visual agnosia: apperceptive agnosia and associative agnosia. Recognition of visual objects occurs at two primary levels.
Statistical significanceIn statistical hypothesis testing, a result has statistical significance when a result at least as "extreme" would be very infrequent if the null hypothesis were true. More precisely, a study's defined significance level, denoted by , is the probability of the study rejecting the null hypothesis, given that the null hypothesis is true; and the p-value of a result, , is the probability of obtaining a result at least as extreme, given that the null hypothesis is true. The result is statistically significant, by the standards of the study, when .
Cranial nervesCranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing. The cranial nerves emerge from the central nervous system above the level of the first vertebra of the vertebral column. Each cranial nerve is paired and is present on both sides.
PatientA patient is any recipient of health care services that are performed by healthcare professionals. The patient is most often ill or injured and in need of treatment by a physician, nurse, optometrist, dentist, veterinarian, or other health care provider. The word patient originally meant 'one who suffers'. This English noun comes from the Latin word patiens, the present participle of the deponent verb, patior, meaning 'I am suffering,' and akin to the Greek verb πάσχειν (paskhein, to suffer) and its cognate noun πάθος (pathos).
Meta-analysisA meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting measurements that are expected to have some degree of error. The aim then is to use approaches from statistics to derive a pooled estimate closest to the unknown common truth based on how this error is perceived. It is thus a basic methodology of Metascience.
Eye chartNOTOC An eye chart, or optotype, is a chart used to subjectively measure visual acuity. Eye charts are often used by health care professionals, such as optometrists, physicians or nurses, to screen persons for vision impairment. Ophthalmologists, physicians who specialize in the eye, also use eye charts to monitor the visual acuity of their patients in response to various therapies such as medications or surgery. The chart is placed at a standardized distance away from the person whose vision is being tested.
MEDLINEMEDLINE (Medical Literature Analysis and Retrieval System Online, or MEDLARS Online) is a bibliographic database of life sciences and biomedical information. It includes bibliographic information for articles from academic journals covering medicine, nursing, pharmacy, dentistry, veterinary medicine, and health care. MEDLINE also covers much of the literature in biology and biochemistry, as well as fields such as molecular evolution.
Cochrane LibraryThe Cochrane Library (named after Archie Cochrane) is a collection of databases in medicine and other healthcare specialties provided by Cochrane and other organizations. At its core is the collection of Cochrane Reviews, a database of systematic reviews and meta-analyses which summarize and interpret the results of medical research. The Cochrane Library aims to make the results of well-conducted controlled trials readily available and is a key resource in evidence-based medicine.
BrainstemThe brainstem (or brain stem) is the stalk-like part of the brain that interconnects the cerebrum and diencephalon with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch. The brainstem is very small, making up around only 2.6 percent of the brain's total weight. It has the critical roles of regulating cardiac, and respiratory function, helping to control heart rate and breathing rate.
Human brainThe human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the body, processing, integrating, and coordinating the information it receives from the sense organs, and making decisions as to the instructions sent to the rest of the body. The brain is contained in, and protected by, the skull bones of the head.
