LOW VISION

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.

 

 

Read More Article:

PROCEDURE OF RETINOSCOPE

Sonal Chaurasia

#Future optometrist😊

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