A person with low vision is one who has impairment of visual function for whom full remediation is not possible by conventional spectacles, contact lenses, or medical intervention and which causes restriction in that person’s everyday life.
This definition includes, but is not limited to, those who are registered as blind and partially-sighted.
PRACTICAL DEFINITION of low vision
refers to the person’s functions; takes into account factors such as loss of contrast sensitivity, photophobia and ocular motor problems. Functional vision is a person’s ability to integrate the components vision effectively to accomplish a task.
FUNCTIONAL VISION
Other terms used interchangeably with low vision:
- visually impaired
- partially blind
- partially sighted
- visually challenged
- subnormal vision
low vision was defined as reduced visual function by disorder of the eye or visual system. This results in a level of vision which cannot be improved to within normal limits by medication, surgery or use of convectional correction.
1976 -DEFINITION OF LOW VISION
A person with low vision is one who has impairment of functioning even after treatment and/or standard refractive correction, and has a visual acuity of less than 6/18 or (20/60) to light perception or a visual field of less than 10 degrees from the point of fixation, but who uses or is potentially able to use vision for the planning and/or execution of a task.
1992 - W.H.O new definition of low vision
Functional visual impairment is a significant limitation of visual capability resulting, from disease, trauma or congenital condition which cannot be fully ameliorated by standard refractive correction, medication or surgery.
LIGHTHOUSE DEFINITION (1996)
LIGHTHOUSE DEFINITION (1996) additional manifestation definitions:
- Insufficient Visual resolution
- Inadequate Field of vision
- Reduced peak contrast sensitivity
- Insufficient visual resolution or peak contrast sensitivity at high or low luminances within a range typically encountered in everyday life
refers to anatomical changes in the visual organs caused by diseases of the eye
VISUAL DISORDER
refers to the functional loss that results from a visual disorder
VISUAL IMPAIREMENT
refers to vision-related changes in the skills and abilities of an individual. It describes the level of performance of a person based on functional vision.
VISUAL DISABILITY
refers to the psychosocial and economic consequences of visual loss, such as the loss of independence or the inability to work.
VISUAL HANDICAP
2 main population groups of LOW VISION PATIENTS:
- those having congenital eye diseases and diseases occurring early in life such as retinoblastoma, congenital cataracts and optic nerve diseases.
- those having degenerative diseases occurring later in life such as diabetic retinopathy, macular diseases, senile cataract, glaucoma and retinal vascular diseases.
definition of LEGAL BLINDNESS:
- Binocular visual acuity of 20/200 or less in the better seeing eye
- maximum Visual field is only 20 degrees or less
refers to an individuals functional visual ability in spite of loss.
Visual efficiency
Visual efficiency depends on:
- Training
- experience
- intelligence level
- personality characteristics of the individual
- other disabilities that may interfere normal function
ICD-9 Classification of VA impairments:
- Moderate impairment - Best corrected acuity less than 20/60 (6/18)
- Severe impairment or Legal Blindness - Best corrected acuity less than 20/160 (6/48) Visual field less than or equal to 20 degrees
- Profound Impairment - Best corrected acuity less than 20/400 (6/120)Visual field less than or equal to 10 degrees
- Near total impairment - best corrected acuity less than 20/1000 (6/300) or visual field less than or equal to 5 degrees
- Total impairment - NO LIGHT PERCEPTION
what does ICD stands for?
_I_NTERNATIONAL _C_LASSIFICATION OF _D_ISEASES
ICD-11 Distance vision impairments classifications:
- Mild - presenting VA worse than 6/12
- Moderate - presenting VA worse than 6/18
- Severe - presenting VA worse than 6/60
- Blindness - presenting VA worse than 3/60
ICD- 11 Near vision impairment:
Presenting near visual acuity worse than N6 or M .08 with existing correction
common Visual problems:
- contrast, glare and light
- Over-all blurring
- Central scotoma
- Hemianopsia
- Constricted Visual field
- Blindness
ICD-9 - Impairment can take the form of visual field loss as:
- Scotoma involving the central area (within 10 degrees of fixation)
- Generalized contraction or constriction
- Homonymous bilateral field defects
- Heteronymous bilateral field defects
W.H.O classification of Visual Acuity loss:
- Normal acuity: 20/25 (6/7.5) or better
- Mild vision loss: 20/32 (6/9.6) to 20/63 (6/18.9)
- Moderate vision loss: 20/80 (6/24) to 20/160 (6/48)
- Severe vision loss: 20/200 (6/60) to 20/400 (6/120)
- Profound vision loss: 20/500 (6/150) to 20/1000 (6/300)
- Near blindness: less than 20/1000 (6/300)
- Blindness: NO LIGHT PERCEPTION
conditions that may give rise to low vision:
- cataract/ uncorrected EOR (reversible)
- Xeropthalmia (preventable
- ROP
- Age related macular degeneration
- Glaucoma
- Diabetic Retinopathy
- Corneal disorders
- Retinitis pigmentosa
- other media problem/ Retinal diseases
The W.H.O estimates that approximately ____ million people or ___ of the worlds population has some kind of ______.
370 million
7%
disability
