Vision & Visual Symptoms

VISION & VISUAL SYMPTOMS


VISION & VISUAL SYMPTOMS

VISUAL ACQUITY

  • It is a ability to discriminate b/w two points. ie. measure of the spatial resolution of the ye.
  • Visual acquity is an indication of the clarity or clearness of one’s vision.
  • It is a measurement of how well a person sees.
  • Visual acquity is most commonly measured by Snellen’s visual acquity chart.

FIELD OF VISION

  • The extent of the normal visual field is limited in an individual by anatomical features such as the brow superiorly, the nose nasally (mdially) & the cheek inferiorly.

The field for a white target extends:

  1. Upwards (superior)  →  50-60º
  2. Downwards (inferior) →  70-75º
  3. Inwards (nasally) →  60º
  4. Outwards (temporally)→  90-100º

The tests used to measure the field of vision are:

  1. Confirmation test
  2. Perimetry: Kinetic perimetry, or automated perimetry.
  • Visual field defects are best detected by Goldmann kinetic perimetry & Humphery automated threshold perimetry.

Goldman scale in perimetry

  • Projected stimuli in perimetry are usually white & of variable size & intensity.
  • There are 5 different sizes on Goldman scale designated by Roman numeral I to V.
  • The standard used in both manual & automated perimetry is Goldman III (0.05º and area of 4mm).
  • Failure to recognise target size III necessitates testing with stimulus V.

Goldman scale

Stimulus

I

¼

II

1

III

4

IV

16

V

64

LOSS OF VISION

  • Happen either suddenly (acutely/ abruptly) or gradually (chronically).
  • Vision loss may be painful or painless.

SUDDEN

Painful

Painless

  • Acute congestive (angle closure) glaucoma
  • Macular edema
  • Acute iridocyclitis (uveitis)
  • CRAO (Central retinal artery occlusion)
  • Chemical & mechanical injury to eyeball
  • CRVO (Central retinal vein occlusion)
  • Endophthalmitis
  • Central serous retinopathy
  • Optic neuritis
  • Retinal detachment
 
  • Exudative age related macular degeneration (ARMD)
 
  • Degeneration (ARMD)
 
  • Vitreous & retinal haemorrhage
 
  • Subluxation or dislocation of lens

GRADUAL

Painful Painless
  • Corneal ulceration
  • Corneal dystrophy
  • Chronic simple glaucoma
  • Corneal degeneration
  • Chronic radiocyclitis (uveitis)
  • Cataract (development & senile)
 
  • Dry type- Age related macular degeneration (ARMD)
 
  • Diabetic retinopathy
 
  • Refractive errors
 
  • Presbyopia

 Exam Important

  • Snellen’s chart is used to test Vision.
  • In the normal human right eye, the peripheral field of vision is usually least In the upward direction.
  • Perimetry is a test to assess the Visual field.
  • Standard in perimetry Goldman type III.
  • Severe pain in eye with loss of vision can be a mani­festation of Acute angle closure glaucoma.
  • Sudden painful loss of vision seen in Angle closure glaucoma, Acute uveitis, Endophthalmitis & Optic neuritis.
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