Eye Lesions

Question 1

What visual impairments are we assessing?

Answer 1

Visual Impairments to Assess

• Constriction CN 3
• Convergence CN3
• Depth Perception and Accommodation
• Visual Fixation (with Head Movement) = VOR
• Conjugate Eye Gaze
• Saccades CN 3, 4, 6 (change point of fixation) for rapid exploration of environment
• Visual Scanning or Visual Tracking or Smooth Pursuits of moving target across all Visual Fields
• Confrontation (coming around head)
• Acuity CN2

Question 2

What are the 5 lesion sites we are concerned with and how with the present?

Answer 2

Lesion Sites and Resultant Visual Field Deficits

• Optic Nerve on One Side
  
  • Total Blindness of Ipsilateral Eye
  • Blind in Right Eye: Lose RNH and RTH
  • Blind in Left Eye: Lose LNH and LTH
• Nasal Fibers of Optic Chiasm
  
  • Bitemporal Hemianopsia
  • Nasal Fibers Affected: Lose LNH and RNH
• One Side of Optic Tract
  
  • If Right Side: Left Homonymous Hemianopsia AKA Contralateral Homonymous Hemianopsia
  • If Left Side: Right Homonymous Hemianopsia AKA Contralateral Homonymous Hemianopsia
  • Lesion Sites and Resultant Visual Field Deficits
• Ipsilateral Nasal Hemianopsia
  
  • Left Ipsilateral Nasal Hemianopsia: Lose LTH
  • Right Ipsilateral Nasal Hemianopsia: Lose RTH
• Occipital Lobe
  
  • Contralateral Homonymous Hemianopsia
    
    • Lose: Temporal and Nasal Fibers on One Eye
    • Lose: Optic Radiation on One Side
    • Lose: Occipital Lobe Lesion on One Side

Question 3

What general considerations are we concerned with?

Answer 3

Vision Screening

General Considerations

• Observations
  
  • Position of patient to objects
  • Overuse of head or trunk motions
  • Note concomitant cognitive deficits
  • Missing details or too focused on details (I’s and H)
  • Overcompensate with tactile sense
• Functional Implications
  
  • Mobility and Safety during ADL tasks
  • Slowness in processing complex stimuli in environment
  • Negotiating different lighting conditions
• Referral Process
• Screening and referral to (neuro-) opthalmologist

Question 4

How do we test the Optic Nerve CN II?

Answer 4

CN II (Optic Nerve)

• Visual Receptive Pathway (LGN)
  
  • Visual receptors to visual cortex
  • LGN and initial visual reception
• Functions Tested
  
  • Acuity
  • Confrontation Test or Peripheral Vision Screen or Visual Field Test

Question 5

How do we test the Oculomotor nerve CN III?

Answer 5

CN III (Oculomotor Nerve)

• Pupillary Light Reflex Pathway (Pretectum)
  
  • Pretectum and pupillary reflex
• Functions Tested
  
  • Pupillary Constriction Test
  • Pupillary Consensuality Test
  • Convergence Test

Question 6

How do we test CN III (Oculomotor), CN IV (Trochlear) and CN VI (Abducens)?

Answer 6

CN III, IV, VI (Oculomotor, Trochlear and Abducens Nerves)

• Superior Colliculi and range of motion, VOR, Saccades
• Visual Motor Pathway (Superior Colliculi)
• Functions Tested
  
  • Fixation (Hold gaze)
  • Visual Scanning or Tracking (Smooth pursuits)
  • Saccades (Quick voluntary movement)

Question 7

How do we test for vision perception?

Answer 7

Vision Perception Assessment

Visual Processing

• Three Areas
  
  • Primary
  • Visual Association Area
  • Higher Order Visual Association Cortex

​Two Higher Order Visual Processing Pathways

• Dorsal stream- where
• Ventral stream- what (form, color, texture)

​Parallel Processing Visual Pathways

• Frontal Eye Fields
• Left Hemisphere- language
• Right Hemisphere- spatial awareness

Multimodal Areas of the Cortex

• PMAC- Posterior multimodal association cortex
• AMAC- Anterior multimodal association cortex