Visual system dysfunction 1 handouts.pdf

DPT 6340 Visual System Dysfunction With Thanks to Dr. Christine Baker for the majority of these slides Objectives Identify clinical presentation and pathology of common visual dysfunctions Identify strategies for managing patients with visual impairments Introduction—U.S. impact A majority of person...

DPT 6340 Visual System Dysfunction With Thanks to Dr. Christine Baker for the majority of these slides Objectives Identify clinical presentation and pathology of common visual dysfunctions Identify strategies for managing patients with visual impairments Introduction—U.S. impact A majority of persons with VI are elderly; half the blind population in the US is over 65 years of age. Every 7 minutes someone in U.S. becomes permanently blind or partially sighted/low vision. Nearly 1 in every 1,000 children in U.S. has low vision or is legally blind. Definitions Medical/Legal: Blind – central visual acuity of 20/200 or < in better eye with best correction, or field of vision limited to < 20 degrees. Partially sighted/low vision – visual acuity better than 20/200 but < 20/70 in better eye with best correction Educational: Blind – learns through tactile or auditory materials Partially sighted/low vision – learns through enlarged print or with use of optical aids (i.e. magnifying glass or lens) Common Diseases/Disorders: AIDS and vision loss---- 35-75% of persons with AIDS (PWA) develop visual problems ranging up to total blindness; as earlier diagnosis and improved treatment prolong life, more PWA are surviving to the stage of vision loss; vision loss appears to be a late complication of AIDS; different causes of vision loss in PWA: AIDS retinitis; AIDS CNS infections; AIDS toxoplasmosis retinitis; AIDS Kaposi's sarcoma Common Diseases/Disorders: Anopsia-- lack of vision in an eye due to interruption of an optic nerve Common Diseases/Disorders:  Cortical visual impairment (aka cortical blindness)-- results from damage to visual cortex  extent of visual loss depends on complexity of damage to visual cortex;  eye usually shows no pathology but neurological damage hinders stimulation from reaching brain and/or hinders organization or decoding of information once it reaches the brain.  May be able to gain some degree of functional vision if vision stimulation is provided (brain plasticity). Common Diseases/Disorders:  Diabetic retinopathy-- proliferation of blood vessels may cause hemorrhaging into vitreous or scar formation of retina  may result in blurred vision or total loss of vision;  both juvenile and adult onset diabetics can develop this; usually develop problems about 20 years after onset of diabetes;  incidence and severity increase with duration of diabetes, and may be worse if diabetes is poorly controlled;  accounts for about 1/4 of persons with VI in western world. Example of Diabetic Retinopathy Common Diseases/Disorders:  Glaucoma-- often caused by increased pressure in the eye; may be due to faulty drainage system of eye  If pressure continues, decreased blood supply so peripheral retinal cells may die and eventually can damage optic nerve;  In adults, symptoms may be poor night vision, halos around lights, and photophobia (‘fear’ of light, aka light sensitivity), subtle loss of contrast; in kids, may see tearing, photophobia, and spasms of eyelids.  Gradual onset, but can be controlled with medications or surgery. Can result in total blindness if not treated. May be exacerbated by fatigue or stress. Example of Glaucoma Example of Glaucoma Common Diseases/Disorders:  Hemianopia (also known as homonymous hemianopsia)— interruption of an optic track resulting in lack of vision on 1 side of the visual field in both eyes; images from only one half of each eye reach the brain, thus there is only reception of half-fields for each eye; more commonly seen in persons with CVA;  no treatment except to try to alleviate the cause (i.e. tumor or hemorrhage); visual field losses may be improved with prism glasses, but success depends on user's motivation and perceptual ability; may need orientation and mobility instruction. Common Diseases/Disorders In hemianopia, half of the field is blanked out on both eyes. The most common defect, right homonymous hemianopia, occurs in corresponding halves of the right field of vision. It can also occur in corresponding halves of the left field of vision (left homonymous hemianopia), in the upper half of the field (superior hemianopia), the lower half (inferior hemianopia), or both outer halves of the field (bitemporal hemianopia). Explanation of Hemianopia Example of Hemianopia Example of Hemianopia This is the ‘normal’ view of Paris Example of Hemianopia This is what would be seen by a person with bitemporal hemianopia. Vision after Stroke Brain stem strokes: Ocular motility issues, diplopia, oscillopsia, visual distortions, paralysis of conjugate gaze Visual field defects: homonymous hemianopsia is common need to differentiate from neglect