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CLINICAL LOW VISION
Midterm Quiz 1
| Question | Answer |
|---|---|
| Common Causes of Low Vision | • Cataracts • Albinism • Diabetic retinopathy • Corneal scarring • HIV related disease • Optic nerve head disease • Trauma • Retinitis pigmentosa • Glaucoma • Microphthalmos • Macular degeneration • Cortical blindness • Aniridia |
| Symptoms of Low Vision | • Distorted VA • Restricted VF • Deprived night vision • Defected colour vision • Severely reduced contrast sensitivity • Difficlty performing ADL independently • Differing light levels needed |
| Categories of Vision Loss | 1. Reduced visual acuity 2. Reduced contrast sensitivity 3. Reduced visual field |
| Probably one of the most common symptoms of eye disease causing low vision and may occur as a result of several ocular pathologies | REDUCED VISUAL ACUITY |
| What are several ocular pathologies that may result in reduced VA | - Cataracts - Keratoconus - Microcornea - Corneal degeneration/dystrophy - Failed corneal graft - Dislocated lens - Aniridia - Albinism |
| Having a reduced VA, it may affect everyday activities like: | - Reading - Writing - Driving |
| Behavioral Manifestation of Reduced Distance Visual Acuity | • Recognizing details (faces) • Learning by imitation • Orientation and mobility • Reading road signs • Driving |
| Behavioral Manifestation of Reduced Distance Visual Acuity (cont.) | • Difficulty in reading and writing • Difficulty in grooming/self care • Preparing food and eating • Difficulty in using computers • Difficulty in signing documents • Difficulty with arts and crafts |
| What are the behavioral manifestations as a result of a secondary reduction in contrast sensitivity | • Bumping into objects like door frames or furniture • Seeing time on a watch can be difficult • Identifying coins and currency may be problematic |
| What are the behavioral manifestations as a result of a secondary reduction in contrast sensitivity (cont.) | • Difficulty in walking down steps • Difficulty in driving and mobility in a dimly lit area • Difficulty in reading poor contrast materials like the newspaper |
| Management of Reduced Visual Acuity | • Spectacles • Telescopes • Magnifiers (hand and/or stand) and microscopes for near tasks • LVAs supplemented with environmental modifications and the use of colour to enhance the effects of disease conditions on contrast sensitivity. |
| May occur early in disease conditions when visual acuity may not be or minimally affected. | REDUCED CONTRAST SENSITIVITY |
| Conditions resulting in a reduction of contrast sensitivity | - media opacities - cataracts, corneal scars, vitreous abnormalities - diabetic retinopathy, glaucoma |
| Patients having reduced contrast sensitivity is sensitive to | lighting and glare |
| Behavioural manifestations that may accompany a reduction in contrast sensitivity include | • Bumping into objects • Difficulty seeing time on a watch • Difficulty identify coins • Difficulty in mobility • Difficulty in seeing curbs and negotiating stairs |
| Management of reduced contrast sensitivity | • Filters • Environmental modifications to enhance contrast either by adding colour contrast or lighting adjustments • Lighting modifications to avoid glare • Closed-circuit televisions |
| May be either central or peripheral field loss | REDUCED VISUAL FIELD |
| Ocular conditions resulting in central field loss include: | • Age-related macular degeneration • Best's disease • Stargardt's macular dystrophy • Macular hole • Macular coloboma • Myopic degeneration • Inflammation - chorioretinitis or macular |
| Produces inability to perceive objects or people in direct line of sight | Central visual field loss |
| Behavioural manifestations that may occur as a result of central field loss | • Not talking directly to people • Unusual head position • Lack of eye contact • Diminishing ability to recognize people in front of them • The secondary reduction in VA may produce difficulties in reading and writing |
| Behavioural manifestations of poor colour vision | • Inability to identify colour of objects • Uncoordinated clothing • Sorting fruits and vegetables difficult • Issues identifying medicines • Identifying food on plate difficult |
| Management of central field loss | • Training eccentric viewing • Low powered magnifiers • Low powered magnifiers • Line guides |
| Affects the individual’s ability to perceive people or objects to the sides | Peripheral Field Loss |
| Ocular conditions producing peripheral field loss | • Retinitis pigmentosa • Glaucoma • Leber’s congenital amaurosis • Optic atrophy • Intracranial lesions • Lasered diabetic retinopathy • Retinopathy of prematurity • Stroke, brain injury, brain tumour • Multiple sclerosis • Retinal detachment |
| Behavioural manifestations in response to peripheral field loss | • Unusual head movements • Difficulty in reading • Uncertainty in mobility • Inability to find lost objects |
| Behavioural manifestations in Partial Blurred Vision | • Difficulty in reading and writing • Difficulty in recognizing details like facial features and facial expressions • Difficulty in reading road signs • Difficulty in orientation and mobility |
| Management of peripheral field loss | • Orientation and mobility • Reverse telescopes • Minus lenses • Fresnel prisms • Mirrors |
| Diseases can be roughly divided into 3 groups based on the areas of the visual system mostly affected: | i.Anterior segment ii. Posterior segment iii. Visual pathways |
| clouding of the crystalline lens | CATARACT |
| Cataract may develop as a result of: | - aging - trauma - congenital - drug induced (high dose of steroids) - metabolic problems (ex. diabetes) |
| CLINICAL PRESENTATION of Cataract | Visual loss due to clouding of lens |
| OPTOMETRIC MANAGEMENT of Cataract | - UV Sunglasses - Avoid Smoking - Good diabetic control |
| Dystrophy in which structural changes within the cornea cause it to become thin and change from the normal curve to a more conical shape | KERATOCONUS |
| CLINICAL PRESENTATION of KERATOCONUS | - Refractive errors (usually myopic astigmatism) - Blurred or distorted images - Glare, Cloudy vision and reduced VA |
| OPTOMETRIC MANAGEMENT of KERATOCONUS | - Contact lenses |
| caused by an infection of the ocular surface by a bacterium (Chlamydia trachomatis serotypes A-C) | TRACHOMA |
| CLINICAL PRESENTATION of TRACHOMA | - Irritation - Photophobia - Scarring, severe dryness and opacity of the cornea |
| • Also known as river blindness • caused by filarial nematode Onchocera volvulus - worm transmitted by the Simulium black fly which breeds in rivers and stream of Africa | ONCHOCERIASIS |
| CLINICAL PRESENTATION of ONCHOCERIASIS | - Conjunctivitis - Corneal Scaring - Uveitis - Glaucoma *high risk of blindness* |
| can result in xerophthalmia (severe dryness) and lead to complication at the anterior and posterior segments of the eye | VITAMIN A DEFICIENCY |
| CLINICAL PRESENTATION of VITAMIN A DEFICIENCY | - Irritation due to dryness - Scarring of the cornea - Ulceration and Perforation(Keratomalacia) - Night blindness may occur |
| MANAGEMENT of VITAMIN A DEFICIENCY | - Vit. A supplements |
| - Most common - decreased aqueous drainage caused by a dysfunction or clogging of the trabecular meshwork resulting to elevated eye pressure | OPEN ANGLE |
| - “acute glaucoma” - occurs when angle between the cornea and iris closes abruptly. With this, fluid can’t access the drainage pathway, causing an increase of eye pressure rapidly | CLOSED ANGLE |
| CLINICAL PRESENTATION of OPEN ANGLE | may not notice any symptoms until severe visual damage has occurred |
| CLINICAL PRESENTATION of ACUTE ANGLE CLOSURE | - red, painful eye with disturbance of vision |
| blood vessels fail to transport food, waste and oxygen | ISCHEMIA |
| blood vessels leak blood or fats causing damage to the retina | LEAKAGE |
| blood vessels can cause massive hemorrhages or retinal detachment | ABNORMAL SHAPE |
| CLINICAL PRESENTATION of DIABETIC RETINOPATHY | - Asymptomatic in early stages - Fluctuating or severely reduced VA - Sensitivity to glare - Reduced contrast sensitivity - Advanced neglected stages can lead to blindness |
| • caused by degenerative changes to the central area of the retina causing gradual or sudden loss of vision • Smoking is well-known risk factor | AGE RELATED MACULAR DEGENERATION |
| CLINIC PRESENTATION of AGE RELATED MACULAR DEGENERATION | - Sudden image distortion (Wet AMD) - Absolute or relative area of no vision (scotoma) primarily in central areas - Reading and driving becomes increasingly difficult - Decrease in color recognition and contrast sensitivity |
| • most common cause of INHERITED BLINDNESS • progressive loss of photoreceptor cells • Rod photoreceptors are affect first thus night blindness is typically the first symptom | RETINITIS PIGMENTOSA |
| CLINICAL PRESENTATION of RETINITIS PIGMENTOSA | - Night and peripheral vision - go hand in hand - the more advanced, the smaller the visual field (tunnel vision) - difficult to move around safely as visual field becomes smaller and central retina becomes involved |
| • deficiency in the pigmentation of the skin and hair, as well as the iris and retina • trait inherited through autosomal recessive or sex-linked transmission | ALBINISM |
| CLINICAL PRESENTATION of ALBINISM | - decrease in VA due to macular - underdevelopment (hypoplasia) - nystagmus - associated refractive error - photophobia |
| OPTOMETRIC MANAGEMENT of ALBINISM | corrective spectacle lenses as well as absorptive lenses to reduce photophobia |
| also known as cortical blindness and this disorder is caused by damage to the parts of the brain that process vision | CORTICAL VISUAL IMPAIRMENT |
| CAUSES of CORTICAL VISUAL IMPAIRMENT | - Lack of oxygen - Developmental brain defects - Head injury - Hydrocephalus - Stroke - Infection of the central nervous system |
| CLINICAL PRESENTATION of CORTICAL VISUAL IMPAIRMENT | - Variable vision - fluctuates from min to min especially when tired - Some objects may be easier to see than other ex. difficulty recognizing faces or facial expressions but fewer problems with written materials |
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