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Study Vision
| Term | Definition |
|---|---|
| Sclera | The external, opaque coat of the eye. It provides attachment points for extraocular muscles and protects the inner structures. It is susceptible to infection and thins/becomes more translucent in children, and yellows with age. |
| Iris | The colored, contractile diaphragm located between the cornea and the lens. It regulates the amount of light entering the eye. |
| Pupil | The opening at the center of the iris. Its size, controlled by the dilator and sphincter muscles of the iris, determines the amount of light entering the eye. |
| Cornea | Transparent, dome-shaped front window of the eye with no blood supply. Highly sensitive and provides about two-thirds of focusing power. Its curvature influences myopia, hyperopia, and astigmatism. It has five layers and is about 0.5 mm thick. |
| Lens | Transparent, flexible structure behind the iris and in front of the vitreous. Held by zonal fibers and lacks blood supply. Changes shape to focus at different distances. Loss of transparency results in cataracts |
| Retina | The light-sensitive layer of tissue at the back of the eye. It contains photoreceptors (rods and cones) that convert light into electrical signals. |
| Choroid | The vascular layer between the retina and sclera. It nourishes the back of the eye. |
| Ciliary Body | Located just behind the iris. It produces aqueous humor and controls accommodation by changing the shape of the lens via zonal fibers. |
| Macula | Located in the center of the retina, temporal to the optic nerve. It is responsible for detailed central vision and color vision. The fovea, the very center of the macula, has the highest concentration of cones. |
| Aqueous Humor | Thin, watery fluid filling the anterior chamber between cornea and iris. Nourishes cornea and lens and helps maintain eye shape. Continuously produced by the ciliary body and drained through the canal of Schlemm. Excess or poor drainage can cause glaucoma |
| Vitreous Humor | Thick, clear, jelly-like substance filling the eye behind the lens, making up two-thirds of its volume. It transmits light, supports the lens, helps hold the retina in place, and maintains eye shape. It is 99% water and is not replaced |
| Superior Rectus | Elevates the eye. |
| Inferior Rectus | Depresses the eye. |
| Medial Rectus | Adducts the eye. |
| Lateral Rectus | Abducts the eye. |
| Superior Oblique: | Rotates the eye (intorsion) during angled viewing. |
| Inferior Oblique | Rotates the eye (extorsion) during angled viewing. |
| RECTUS | RECTUS muscles control UP, DOWN, and SIDE-TO-SIDE eye movements. |
| OBLIQUE | OBLIQUE muscles control ROTATION of the eye during angled viewing. |
| Rods | 125 million. Spread throughout the peripheral retina. Responsible for peripheral and night vision (dim lighting). Do not detect color. The fovea does NOT contain rods. |
| Cones | 6.5-7 million. Highest concentration of cones in the macula. Most densely packed within the fovea (ONLY cones in fovea). Sensitive to bright light and color. |
| The Anterior Visual System (AVS) | Cornea, iris, pupil, lens, aqueous humor, vitreous humor, retina, and optic nerve work together in the AVS, whose goal is to deliver clear, accurate input. |
| The Posterior Visual System (PVS) | Visual signals pass: optic chiasm → optic tracts → LGN → superior/inferior colliculi → occipital cortex for AVS→PVS processing. Left field→right cortex. Temporal fibers remain ipsilateral; nasal fibers cross. |
| Visual Cortex | Information FIRST arrives at the Primary Visual Cortex (V1), also known as Broadmann Area 17. Two routes then carry information from the occipital lobe: Superior route & Inferior route |
| Superior route | Magnocellular pathway, Dorsal route ("Where"). Projects to the Parietal Lobe. |
| Inferior route | Parvocellular pathway, Ventral route ("What"). Projects to the Inferior Temporal Cortex |
| Cranial Nerve II (Optic Nerve) | Vision |
| Cranial Nerves III, IV, VI | Responsible for extraocular movements, gaze stabilization, and postural control. Impaired nerves will result in diplopia, strabismus, and impaired scanning. |
| LR6 SO4 AO3 | Lateral Rectus = Cranial Nerve VI (Abducens) Superior Oblique = Cranial Nerve IV (Trochlear) All Others = Cranial Nerve III (Oculomotor) |
| Cranial Nerve VI - Abducens | Lateral rectus: 6th nerve palsy from vascular disease, trauma, or high intracranial pressure limits abduction. Causes horizontal distance diplopia and difficulty watching TV, seeing a clock, or with mobility. Most common palsy |
| Cranial Nerve IV - Trochlear | Superior oblique: 4th nerve palsy from trauma or vascular issues causes the eye to drift upward and limits downward gaze. Leads to vertical diplopia, trouble with near and far tasks, and difficulty converging when looking down (e.g., using bifocals) |
| Cranial Nerve III - Oculomotor Nerve | Superior, Inferior, Medial Recti; Inferior Oblique 3rd nerve palsy: Ptosis Involvement of this nerve will result in: Horizontal diplopia |
| Optometrist (OD) | Specializes in diseases of the visual system and related systemic conditions. Optometrists are trained in visual rehabilitation, including vision therapy, lenses, and low-vision care, though only some provide it. Often requires added residency or exams. |
| Ophthalmologist (MD) | Medical doctor specializing in diseases of the eye and eye surgery. |
| Occupational Therapist (OT) | Purpose is not to diagnose, but potentially detect unrecognized visual deficits, identify visual strengths which can aid in independent functioning and determine appropriate treatment intervention. |
| Vision Rehabilitation Therapist (CVRT) | Certified to provide specific vision rehabilitation services to blind or visually impaired clients. Focus on compensatory skills and assistive technology for vocational opportunities and independent living. |
| Certified Low Vision Therapist (CLVT) | Uses functional vision evaluations to assess acuity, visual fields, contrast, perception, and visual motor skills as they relate to vision impairment and disability. Instructs in use of prescribed low vision devices, ADL, and IADL performance. |
| Orientation and Mobility Specialist | Teaches individuals to travel safely in their environment. Provides instructional techniques using problem-solving strategies and methods for non-visual and visual techniques using remaining vision. |
| Teacher of the Visually Impaired (TVI) | Focuses on adaptive techniques such as braille, adaptive devices, and collaboration with educators. |
| Academy for Certification of Vision Rehabilitation and Education Professionals (ACVREP) | Private organization offering certifications for those working with people with visual impairment, regardless of discipline. Certifications include CLVT, COMS, CVRT, CATIS, and CDBIS. |
| Model of Care for Vision Rehabilitation in Medical Settings | In medical settings where vision isn’t the primary focus, OT screens, completes a functional vision eval, refers to optometry/ophthalmology or vision rehab, and provides generalist OT interventions while awaiting specialist care |
| The Inter-relationship Model | Illustrates the collaborative relationship between: Vision Rehabilitation Therapist Occupational Therapist Optometrist Orientation and Mobility Specialist Teachers of Vision Impairment |
| Accrediting Bodies | AAO and COVD are major optometry organizations. NORA focuses on neurologically affected individuals and supports vision therapy and neuro-optometric rehabilitation |
| Three Component Model of Vision | Visual Integrity Visual Efficiency Visual Information Processing |
| Visual Integrity | Visual acuity Refraction Eye health Visual fields |
| Visual Efficiency | Accommodation Binocular vision Eye movements |
| Visual Information Processing | Visual spatial skills Visual analysis skills Visual motor integration skills |
| Visual Hierarchy | Made by Mary Warren. Adaptation through vision relies on a hierarchical structure: 1. Visual acuity 2. Visual fields 3. Oculomotor control 4. Attention = alert and attending 5. Scanning 6. Pattern recognition 7. Visual memory 8. Visual cognition |
| Refractive Disorders | Refraction Emmetropic Eye Myopia (Nearsightedness) Hyperopia (Farsightedness) Astigmatism Anisometropia |
| Refraction | Light rays bend to focus on the fovea. Quality refracting surfaces allow light to pass smoothly and symmetrically. |
| Emmetropic Eye | Length is just right, and the focal point falls precisely on the fovea. |
| Myopia (Nearsightedness) | Eyeball too long; light focuses in front of retina. Clear near vision, blurred distance. Eye cannot adjust. Squinting helps. Causes blurred distance vision, needing to move closer, and reduced interest in the environment. |
| Hyperopia (Farsightedness) | Eyeball is too short. Light rays focus behind the retina. Blurred vision at near. Accommodation requires muscular effort. Effects on function: Discomfort reading, tearing, headaches, avoidance of close work. |
| Astigmatism | Vision is distorted at both distance and near. Cornea is spoon-shaped or dimpled, creating an uneven surface. Causes light rays to enter the eye at two different points (uneven refraction). |
| Anisometropia | Significant difference in refractive error between the two eyes (e.g., mild hyperopia in the right eye, high hyperopia in the left eye). Interferes with binocular vision. Difficult for the brain to merge images; cortex may suppress input from one eye. |
| Testing Refractive Disorders | Phoropter Retinoscope: Views the light reflected out of the eye; the optometrist interprets the movement of reflected light. |
| Visual Acuity | Measures the eye’s resolving power with high-contrast (black on white). 20/20 is normal. Numerator: distance patient sees letter; denominator: distance normal vision sees it. 20/100 means patient sees at 20 ft what normal sees at 100 ft. |
| Development of the Eye and Visual Acuity | Retina, optic nerve, and tract are developed at birth; myelination continues. Rapid growth occurs in first 6 months to 2 years. Newborn acuity: 20/400–20/800. Early vision issues critical due to plasticity. AOA recommends exams at 6 mo, 3 yr, 6 yr |
| Testing Acuity | Distance and Near; Contrast Sensitivity Function |
| Distance Acuity Tests | Snellen Chart, ETDRS Chart, Tumbling E, LEA Symbols Test |
| Snellen Chart | Uses optotypes (constructed with strict geometric rules). Pros: Widely used, readily available, inexpensive, easy to use and interpret. Cons: Varying number of optotypes per line, serif font, not as accurate as other charts. |
| ETDRS Chart | Gold standard for distance acuity. Uses SLOAN letters based on Landolt C rings. Standard distance: 13 ft. Pros: standardized scoring/method. Cons: expensive, mainly for low vision, large and heavy. |
| Tumbling E | For children or adults unable to read letters (aphasia, education level, language barriers). Requires pointing in the direction the "E" is pointing. Appropriate for children 5+ due to sense of direction. |
| LEA Symbols Test | Uses LEA Symbols (pediatric visual acuity test calibrated with Landolt C test). LEA Symbols optotypes are calibrated against Snellen E. Effective with children 2.5 - 6 years. Administration involves matching shapes. |
| Near Acuity Tests | Near Visual Acuity Chart, LEA Symbols Near Acuity Chart, Broken Wheel Test, Teller Acuity Cards |
| Near Visual Acuity Chart | Standard testing distance is 16 inches. |
| LEA Symbols Near Acuity Chart | 16" testing distance. |
| Broken Wheel Test | Uses Landolt C. Child points to the car with the "broken wheel." |
| Teller Acuity Cards | Infants prefer to look at patterns. Examiner observes behavior and ocular movements. Appropriate for up to 18-24 months. |
| Acuity vs. Contrast Sensitivity | Acuity: ability to see high-contrast objects. Contrast sensitivity: ability to see larger, low-contrast objects. Impacts reading, mobility, driving, face recognition, and ADLs (e.g., facial expressions, curbs, stairs, dusk driving, meal prep). |
| Testing Contrast Sensitivity | Pelli-Robson Contrast Sensitivity Chart (gold standard for research). MARS Contrast Sensitivity Chart (gold standard for clinic). LEA Symbols Contrast Sensitivity Chart. LEA Hiding Heidi. |
| Eye Health Disorders | Age-Related Macular Degeneration (AMD), Glaucoma, Cataract, Diabetic Retinopathy (DR) |
| Age-Related Macular Degeneration (AMD) | Degenerative disorder of macular photoreceptors, usually in those 55+. Risk factors: age, family history, smoking, female, sun exposure, high fat intake. Causes progressive, irreversible vision loss and greatly reduces visual acuity |
| Dry AMD (90%) | Gradual, progressive loss, non-neovascular, characterized by drusen. Treatment: Vitamin therapy, gene therapy, stem cell transplant/retinal transplant. |
| Wet AMD (10%) | Leaking blood (neovascular), aggressive, profound, rapid decrease in vision. Treatment: Drug injections, high levels of antioxidants and zinc. |
| AMD Testing | Amsler Grid |
| Glaucoma | High intraocular pressure causing progressive optic nerve damage and peripheral vision loss. Risk factors: age 40+, African American, family history. Treated with meds (drops, ointment, pills) to reduce or drain fluid |
| Cataract | Clouded lens from protein clumping. Causes blurry vision, night difficulty, glare sensitivity, poor contrast, double vision. Risk factors: age 65+, diabetes, family history, eye injury, sun, smoking. Treated with early mods or lens replacement surgery. |
| Diabetic Retinopathy (DR) | Common, preventable DM complication. 40% with 5+ years of DM affected. Risks: long DM duration, uncontrolled blood sugar, HTN, obesity, kidney disease. High blood sugar damages vessels. Treatment: early detection and blood sugar control |
| General Treatment for Acuity and Contrast Issues | Interventions: modify environment (large print, magnifiers, lighting, contrast, talking devices), encourage glasses use, refer to optometrist; modify tasks (pre-chopped food, larger containers); use remaining senses (hearing, touch, proprioception) |
| Visual Fields | Normal visual field extents: Upward: 50∘ Downward:70∘ Inward: 60∘ Outward: 90∘ |
| Unilateral Spatial Inattention (Neglect) | Diminished awareness of one side of the visual field. Can be present with a VF cut or alone. Severity changes based on stimuli. Hyposensitivity to the affected side and hypersensitivity to the "good side." |
| Neurological Basis | Postcentral gyrus (parietal lobe) perceives sensory stimuli. Frontal eye fields (frontal lobe) direct head/eye movement. Cingulate gyrus assesses stimulus relevance. Subcortical structures (thalamus, basal ganglia) also contribute |
| Visual Field Cut/Loss vs. Inattention/Neglect | Visual field cut: visual-only, aware, movement OK, consistent compensatory scanning, tested by confrontation/perimetry. Inattention/neglect: multi-system, unaware, resists moving into field, haphazard scanning, identified with objective tests. |
| Testing Visual Fields | Confrontation Field Testing. Vision Disk. Perimetry Testing. |
| Assessment and Treatment of Hemi-Inattention | Skilled observation during performance of tasks Catherine Bergego Scale Baking Tray Task |
| Visual Field Treatment | Focus on compensation/adaptation over restoration. Compensatory scanning therapies preferred. Prognosis for visual field restoration is guarded. Activities teach left-to-right or clockwise/counterclockwise scanning patterns |
| Visual Fields / Neglect Treatment | Use organized, dynamic scanning: predict/reflect, scan static & mobile, turn head, limb activation, tactile cues, mirror therapy, lighthouse strategy, perceptual anchors, prisms, and emerging VR, music, or TENS approaches |
| Accommodation | The ability to change the focus of the eye to see objects clearly at varying distances. |
| Types of Accommodative Disorders | Accommodative Insufficiency Accommodative Excess Accommodative Infacility Presbyopia |
| Accommodative Insufficiency | Less accommodation than expected for the individual's age. Typically affects children and young adults. |
| Accommodative Excess | Spasm of the ciliary muscle, leading to fluctuating changes in accommodation. |
| Accommodative Infacility | Reduced speed when shifting focus between near and far objects. |
| Presbyopia | Age-related decline in accommodative ability, usually starting around age 40-45, causing decreased near visual acuity. |
| Binocular Vision | The ability to fuse information from both eyes into a single image. |
| Binocular Vision Development | Eye alignment may be variable in the first month of life. After one month, alignment should be normal. Strabismus occurring after this point indicates a problem. |
| Binocular Vision - How it Works | Each eye’s visual info stays separate until the primary visual cortex, which processes binocularly. Left visual field → right brain; right visual field → left brain. Nasal fibers cross at optic chiasm; temporal fibers stay ipsilateral. |
| Binocular Vision Disorders | Requirements for normal ocular alignment: Equal optics in both eyes. Proper eye alignment. Hallmark symptom: Diplopia (double vision). Prevalence: 25% of children aged 6 months to 18 years. Includes both strabismic and nonstrabismic conditions. |
| Strabismus | Strabismus: misalignment of the eyes. Types—esotropia (inward), exotropia (outward), hypertropia (upward), hypotropia (downward), or combinations. Can cause double vision and possible suppression of one eye. |
| Nonstrabismic Binocular Vision Disorder | Most common: Convergence Insufficiency. Difficulty converging on a near object. Tendency for eyes to turn outward (exophoria) during near work. Can be associated with CVA and TBI. |
| Fusional Vergence | Neuromuscular effort to maintain binocular vision. Convergence is used to overcome exo-deviations. Divergence is used to overcome eso-deviations. |
| Clinical Presentation of Binocular Vision Disorders | Diplopia |
| BV Screening for Deficits | Gather information about onset, etiology, triggers, severity, duration, and associated symptoms of diplopia. Determine if the deficit is related to visual acuity, suppression, or strabismus. |
| Convergence Insufficiency Symptom Survey (CISS) | Questionnaire identifies convergence insufficiency symptoms: eye fatigue, discomfort, headaches, double vision, reading issues. Scores ≥16 (children <21) or ≥21 (adults) suggest convergence insufficiency |
| Screening for Binocular Vision | Tests: Diplopia grid, cover/uncover, Near Point of Convergence (NPC). BREAK = distance patient sees double (normal 4–6 in). RECOVERY = distance single vision returns. Failure to converge suggests strabismus |
| BV Significance for Therapy | Binocular vision disorders can lead to: Blurred vision Headaches Eyestrain Reading problems Fatigue Difficulty with ADLs and mobility (driving, reaching, pouring). |
| Diplopia Research | A 2018 national survey indicated that most OTs believe they should be able to manage binocular vision in practice, but many lack access to neuro-optometry services. Prisms and occlusion are established treatments for diplopia. |
| OT Intervention for Binocular Vision Disorders | Collaboration with optometry is essential. Generalist OTs should refer for binocular vision evaluation. Afterward, OTs adapt, modify, and compensate for deficits, adjusting activities and environments to reduce visual stress |
| Treatment for Diplopia | Optometry: acuity correction, prisms, occlusion/taping, ocular ROM/vision therapy. OT: improve visual awareness, adapt/compensate, use occlusion/prisms in daily tasks with OD/MD, selective partial occlusion (spot patch, bi-nasal). |
| Ocular Motility | Refers to the movement of the eyes. It includes fixation, saccades, and pursuits. |
| Fixation | Definition: Maintaining steady gaze on a stationary object. Normal: Ability to sustain precise fixation for 10 seconds without observable eye movement. |
| Saccades | “Saccades are rapid eye movements to shift gaze. Voluntary or reflexive. Dysfunction reduces speed/accuracy, affecting reading and attention. Direction is controlled by gaze centers; amplitude by duration of neural activity. |
| Saccades: Screening | Use fixation sticks just outside the patient's face. Observe 5 round trips between targets. Note accuracy: undershooting, overshooting, inability to locate target. Developmental Eye Movement Test (DEM) |
| Disorders of Saccades | General Prolongation, Inaccurate Saccades (Overshooting), Saccadic Latency (Time Delay), Asymmetric Saccades, Disconjugate Movements |
| General Prolongation | Unilateral spatial inattention, basal ganglia disorders. |
| Inaccurate Saccades (Overshooting) | Cerebellar lesions |
| Saccadic Latency (Time Delay) | Cortical and brainstem lesions; can be affected by acuity. |
| Asymmetric Saccades | Visual field cut, unilateral spatial inattention, parietal or parieto-occipital cortex involvement. |
| Disconjugate Movements | Multiple Sclerosis. |
| Pursuits (Smooth Pursuits) | Definition: Slower tracking movements to keep a moving object on the fovea. Function: Enable continuous clear fixation on moving objects. Control: Voluntary. |
| Pursuits: Screening | Observe during ROM of eyes together (or separately if needed). Note smoothness of movement and presence of nystagmus. Assess ROM in all directions (O and H patterns, 9 cardinal points of gaze). |
| Disorders of Smooth Pursuit | Losing target with catch-up saccades suggests cerebellar/brainstem disease or poor acuity. Moderate tracking issues occur with inattention, age, meds, or CNS disorders. Severe or absent tracking indicates significant CNS disturbance. |
| Nystagmus | Nystagmus is not explicitly part of visual efficiency skills, but it can affect eye movements. Definition: Involuntary, rhythmic oscillations of one or both eyes. |
| Physiologic Nystagmus | Normal response to optokinetic stimulation or extreme end-range eye movement. |
| Pathologic Nystagmus | Sign of nervous system abnormality. Named for the direction of the fast phase. |
| Optokinetic Nystagmus | Response when the head is stable and the environment is moving (e.g., optokinetic drum). |
| Peripheral Nystagmus | Sudden onset of disequilibrium, vertigo, nausea, vomiting. Worsened by head movement. Fast phase beats AWAY from the side of the lesion. Visual fixation dampens nystagmus. |
| Central Nystagmus | Fast phase beats TOWARD the side of the lesion. Visual fixation does not dampen nystagmus. |
| Nystagmus Key Points | Screen for binocular vision disorders due to their functional impact. Use OT-appropriate treatment techniques. Collaborate with neuro-optometry/ophthalmology and refer to optometrists specializing in vision rehabilitation |
| Brock String | Brock String trains convergence, reduces suppression, and builds fixation/binocular use. Patient fixates each bead: near bead should be single; if double, adjust. Near focus forms an ‘X’; far bead forms a ‘V |
| Visual Efficiency Interventions | Brock String, Tranaglyphs, Prisms |
| Tranaglyphs | Tranaglyphs improve fusional vergence. |
| Prisms | Prisms are wedge-shaped lenses without optical power, which can be added with corrective lenses. They bend light rays to improve eye teaming. |
| Prisms Purpose | Treat binocular vision disorders. Treat hemianopia. Decrease the demand on the neuromuscular components of the visual system. |
| How Prisms Work | Esotropia produces uncrossed diplopia. Prisms move the image to the corresponding retinal point, allowing single vision. Base out prism is used for esotropia. |
| Lens as Prism | plus lens converges light rays. Minus lens diverges light rays. |
| Prism Orientations | Base up Base down Base out Base in |
| Yoked Prism | Base of prism is on the same side for each eye. Used for hemianopia. Expands the affected visual field by about 30 degrees. Only appropriate if the patient does not have inattention. |
| Fresnel Prism | 3M Press-on Optics. Measure, cut, and stick to the lens. Good for trialing prism. Disadvantage: Loses contrast sensitivity. Available in 25, 40, and 45 diopter prisms. |
| Vision Therapy for Saccades | Saccades: Rapid eye movements between targets. Emphasize jumping of eyes between targets. Improve range of motion (ROM) of eyes. Accommodation with near and far targets. |
| Vision Therapy for Pursuits | Pursuits: Smooth eye movements following a moving target. Thumb rotations. Marsden Ball. Pie pan rotations. |
| Vision Therapy - General Information | Office-based vision therapy done by OD or trained therapist. Frequency varies: accommodative/binocular 12–16 visits; eye movements 16–24; visual processing 36–40. Home program 15 min 5×/wk. Cost ~$75–125/session; not covered by Medicaid |
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