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DEFINITION OF LOW VISION (WHO- World Health Organization):

A person with low vision is one who has impairment of visual functioning even after treatment of an operation and standard refractive correction and has a visual acuity of less than 6/18 to light perception or a visual field of less than 10 degree from the point of fixation but who uses or is potentially able to use vision of the planning and execution of a task.

VISUAL IMPAIRMENT:

• PARTIAL BLIND [6/24 TO 6/60]
• LOW VISION [<6/18 TO PL ]
• SUBNORMAL [ 6/18 TO PL]

WHO(World Health Organization) CLASSIFICATION DEFINES LOW VISION AS CORRESPONDING TO:

 

1. VA of less than 6/18 but equal to or better than 3/60.
2. Corresponding VA less to less than 20 degree in the better eye with best possible correction .

LOW VISION :

The best corrected VA in the better eye less than 6/18 and the vision field less than 20 degree from the point of fixation.

VISION IMPAIRMENT:

Refers to condition with decreased VA from blindness to partial sight.

PARTIAL BLINDNESS:

THE BEST CORRECTED VISION ACUITY IN THE BETTER EYE LESS THAN 3/60 0R VISUAL FIELD LESS THAN 10 DEGREE FROM THE POINT OF FIXATION.

 COMPLETE BLINDNESS :

It is defined as no usable vision with exception of light perception.

FUNCTIONAL EFFECT OF LOW VISION:

 

• Loss of central vision.
• Loss of peripheral vision.
• Glare and contrast.

 

GRADES OF VISUAL IMPAIRMENT:

Category of visual Impairment (low vision)	Visual acuity with best possible correction (Maximum less than the)	Minimum equal to or better
0	6/6  (Normal)	6/18
1	6/18 (Visual impairment)	6/60
2	6/60 (severe visual impairment)	3/60- CF at 3m
3	3/60 – CF at 3 m (Partial blind)	1/60-CF at 1m
4	1/60 – CF at 1 m  (Blind)	Light perception(PL)
5	No PL (Total blind)	————–

MAIN CAUSES OF BLINDNESS IN 50+ POPULATIONS ARE AS FOLLOWS:

 

• CATARACT – 62.6%
• REFRACTIVE ERRORS-19.7%
• CORNEAL BLINDNESS- 0.9%
• GLAUCOMA- 5.8%
• SURGICAL COMPLICATION- 1.2%
• POSTERIOR SEGMENT DISORDERS- 4.7%
• OTHERS-5.0%

LOW VISION HISTORY:

 

• DEMOGRAPHIC DATA:

• NAME
• AGE 
• SEX
• OCCUPATION
• HOBBIES

 

• GENERAL HISTORY:

• OH (ocular history)
• FGH (family general history)
• FOH (family ocular history)
• AH (allergy history)

 

• FAMILY DATA:

• Count of family members
• Who take care the patient
• How to manage his\her daily work, who helped?
• Is there is any attender or nurse is there or not?

 

• DIAGNOSIS DISEASE.

 

• HISTORY OF DISORDER.

 

• CHIEF VISUAL COMPLAIN :

 

• DISTANCE VISION PROBLEM-

• Black board
• Seeing face
• Watching TV
• Shop name
• Outdoor – Bus number

 

• NEAR VISION PROBLEM-

• Near work \reading
• Note recognition

 

• LIGHTING ILLUMINATION :

• Dim light 
• Bright light
• Fluroscent tube
• Bulb
• Is there any problem in sunlight or not?

 

• WRITING TASK- Signature

 

• MOBILITY PROBLEM:

 

• How do able to walk? If the answer is yes -then how to walk ,how to manage his\her daily work.

And if the answer is no-then asked the patient that who helped his\her daily work.

 

• GLARE PROBLEM:

• Yes or No.

 

• COLOUR PERCEPTION:

Ask the patient the he or she is able to identified different colours or not?

 

• LIVING SKILLS:

• Food identification
• Coin and note identification
• Face identification
• Dress identication.

 

HOW TO PREVENT LOW VISION?

   Try the 20-20-20 rule:

Every 20 minutes, look away about 20 feet in front of you for 20 seconds.This short exercise can help reduce eyestrain. Clean your hands and your contact lenses-properly. To avoid the risk of infection, always wash your hands thoroughly before putting in or taking out your contact lenses.

NOTE: low vision is vision loss that cannot be corrected with glsasses , contact lens and surgery. It isn’t blindness as limited sight remains.

 

 

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PROCEDURE OF RETINOSCOPE