LINK >>> https://urlgoal.com/2t8kaA
Purpose: Dementia is associated with various alterations of the eye and visual function. Over 60% of cases are attributable to Alzheimer's disease, a significant proportion of the remainder to vascular dementia or dementia with Lewy bodies, while frontotemporal dementia, and Parkinson's disease dementia are less common. This review describes the oculo-visual problems of these five dementias and the pathological changes which may explain these symptoms. It further discusses clinical considerations to help the clinician care for older patients affected by dementia.
Recent findings: Visual problems in dementia include loss of visual acuity, defects in colour vision and visual masking tests, changes in pupillary response to mydriatics, defects in fixation and smooth and saccadic eye movements, changes in contrast sensitivity function and visual evoked potentials, and disturbance of complex visual functions such as in reading ability, visuospatial function, and the naming and identification of objects. Pathological changes have also been reported affecting the crystalline lens, retina, optic nerve, and visual cortex. Clinically, issues such as cataract surgery, correcting the refractive error, quality of life, falls, visual impairment and eye care for dementia have been addressed.
Summary: Many visual changes occur across dementias, are controversial, often based on limited patient numbers, and no single feature can be regarded as diagnostic of any specific dementia. Nevertheless, visual hallucinations may be more characteristic of dementia with Lewy bodies and Parkinson's disease dementia than Alzheimer's disease or frontotemporal dementia. Differences in saccadic eye movement dysfunction may also help to distinguish Alzheimer's disease from frontotemporal dementia and Parkinson's disease dementia from dementia with Lewy bodies. Eye care professionals need to keep informed of the growing literature in vision/dementia, be attentive to signs and symptoms suggestive of cognitive impairment, and be able to adapt their practice and clinical interventions to best serve patients with dementia.
Visual disturbances interfere with normal sight. Several conditions and disorders may cause the various types of visual disturbances. Some are temporary and can be relieved with treatment. However, some can be permanent.
If any visual disturbances begin suddenly and unexpectedly, see a doctor immediately. Although the visual disturbance may be the result of a minor problem, vision disturbances can be the first symptom of other serious conditions, such as:
For example, blurry vision caused by a headache will usually resolve when the headache recedes. Your doctor may prescribe medication to prevent future headaches. They may choose to prescribe medicine that you can take when a headache that causes visual complications begins.
If you experience a visual disturbance that begins suddenly and unexpectedly, see a doctor immediately. While some visual disturbances may be permanent, some can be temporary and relieved with treatment.
Visual disturbance is when you experience a short spell of flashing or shimmering of light in your sight. The symptoms normally last around twenty minutes before your sight returns to normal. Usually, there is no headache during the visual disturbance. A visual disturbance should not be confused with a retinal or ocular migraine where there is a partial or total loss of vision in one eye, normally with a headache.
Firstly, do not panic; visual disturbances can be frightening, but in most cases are short lived. If you are driving or operating machinery, stop what you are doing and wait for the symptoms to go away. Make a note of your symptoms, how long they lasted and what you were doing just before they began. In most cases, there is a common trigger and keeping a diary of symptoms can help work out what the trigger is. Simply avoiding the trigger, where possible, may be all you need to do.
Children, particularly bright, inquisitive, and highly observant ones, may present to the ophthalmologist with visual complaints not readily explained by objective examination. Unlike their parents, these children often are not distressed about the phenomena. The vast majority of these symptoms reflect benign entities, but could also signal migraine or a more ominous psychiatric disease or intracranial pathology. It is useful, when approaching the pediatric patient with a history of visual changes, to have an understanding of natural, entopic phenomena. The precocious child will often recognize these visual phenomena and describe what he or she sees to one or both parents. With a good understanding of normal, physiologic phenomena, the parents can be reassured that no pathologic process is involved in the visual changes the child is describing.2
Some authorities classify photopsias as larger and longer-lasting flashes of light than phosphenes. Photopsias are generated in other parts of the visual system outside the globe itself. However, most of the literature uses the two terms interchangeably. Photopsias are most commonly associated with vitreous detachment, retinal detachment, migraine with aura, migraine aura without headache, and occipital lobe disease.
The most common cause of photopsias or visual disturbance in the child is migraine.3 Fifteen to 30% of children with migraine report visual symptoms. Five percent of these children only experience the aura without headache.4 As in adults, the visual symptoms are episodic visual hallucinations (not based on environmental images) that are typically unformed as colored or colorless flashes, and geometric patterns or lines. However, sometimes the hallucinations may be formed images of people, objects, or animals. In children, unlike in adults, the headache is often absent and the migraine manifests as night terrors, benign paroxysmal vertigo, cyclical vomiting, abdominal migraine, or motion sickness.
Of note, some patients report changes in size of objects, or metamorphopsia of images. Images may move forwards or backwards, or only parts of the body or scene become distorted. This has been referred to as the Alice in Wonderland phenomenon.6
Synesthesia is a condition in which stimulation of one sensory modality causes an experience in another sensory modality. Auditory-visual synesthesia is the term used for visual images, including photopsias in response to sound, usually unexpected and startling. For example, the most common form of auditory-visual synesthesia is when numbers, letters, or symbols generate a color. For example, number 7 may generate the color blue. Functional MRI has shown abnormal stimulation. Although these phenomena are traditionally associated with visual loss or intracranial pathology, they can also occur in the face of a normal ophthalmologic and neurologic examination.10
There is some difficulty in distinguishing migraine visual aura from the epileptic photopsias of a seizure disorder. Occipital lobe epilepsy is most common in the pediatric group. Visual aura of migraine typically develops over minutes and there is mix of positive and negative scotomata. These scotomata typically start small, enlarge, scintillate, and migrate. The scotomata are often linear, with jagged edges. Headache or other signs and symptoms are often present, as noted with pediatric migraines.
The visual symptoms of occipital pole (area 17) epilepsy are also typically simple, elementary, unformed hallucinations. But they lack form and depth and generally do not create a fortification scotoma. They may be colored or colorless and are circular or spherical. Seizures in the visual association areas (areas 18 and 19) tend to have more elaborate form, color, depth, and movement. Photopsias of seizures last only seconds or, rarely, minutes before onset of a seizure. Twenty-nine percent of patients with occipital lobe epilepsy experience blackout of vision.11 These visual symptoms may be followed by minimal alterations in consciousness, therefore not raising suspicion for seizure disorder, or may be associated with dramatic seizure manifestations with generalization. It is important to recognize that postictal headache is a common complaint, making differentiation from migraine sometimes difficult. Finally, occipital lobe seizures tend to occur daily, whereas migraine-associated visual hallucinations occur with longer intervals between attacks.
It is particularly important to differentiate between epilepsy and migraine in the child who harbors a tumor or arteriovenous malformation (AVM) in the occipital lobe. A lesion in the occipital lobe can irritate the surrounding brain matter, leading to seizure activity. Of note, the elementary, unformed hallucinations associated with a seizure focus tend to start more abruptly and remain stationary, contrasting with the building, growing fortification scotoma of migraine. In addition, the visual disturbances of an AVM will usually stay on the same side of the visual field (opposite the lesion).3
Some children with occipital lobe epilepsy may experience ictal cortical blindness, in which the major manifestation of the seizure is blindness. If the seizure remains isolated to the occipital lobe, the patient may not demonstrate other symptoms of seizure, and simply have episodes of complete blindness. Due to the short nature of the attacks, it may be difficult to obtain an EEG during an episode, so the diagnosis would come from history and interictal epileptiform activity.3 After a seizure, children may also develop visual loss or postictal blindness. This is typically a transient phenomenon, lasting hours to days; however, permanent visual loss after a seizure has been reported.
Finally, a major difficulty in the diagnosis of transient visual loss in children is that a large proportion of children claiming visual loss suffer from nonorganic, or psychogenic, visual loss. This should be a diagnosis of exclusion, and the onus is on the ophthalmologist to rule out organic causes of visual loss. Psychogenic visual loss is most common in prepubescent girls ages 9-11, and was termed the "amblyopic schoolgirl syndrome" by Mantyjärvi.12 There are different theories as to why this occurs, many relating to stress at school or at home. Regardless, proving the nonorganic nature of the problem is sometimes difficult. Close follow-up is warranted; many conditions such as craniopharyngioma, Stargardt macular dystrophy, or X-linked adrenoleukodystrophy are initially diagnosed with nonorganic visual loss if there is no obvious optic nerve pallor or and there are no neuro-ophthalmic signs early in the disease.3 2b1af7f3a8