o Visual field: the perceptual space available to the fixating eye
o Purpose: to provide a gross check for any defects in the peripheral visual field
O Extinction phenomenon
Patients with right parietal lesions can exhibit a form of visual extinction. When shown two objects, one contralateral (left) and one ipsilateral (right) to the lesioned hemisphere, subject will report seeing only the one in the ipsilateral (right) field
o Riddochs phenomenon
Some patients with neurological defects suffer from stato-kinetic dissociation
Moving objects are perceived better than static ones
Defects present on automated perimetry (static) tend to be more extensive compared to those measured by manual perimetry (kinetic)
O Finger counting
Tests the patients ability to correctly identify gross targets in each of the 4 major quadrants
Procedure
Examiner and patient remove spectacles
Sit at eye level and 1m away
Have patient occlude OS with palm of their hand and fixates clinicians OS with their OD (clinicians visual field corresponds to the patients)
Place one hand in the mid-plane (50 cm) at about 45 from fixation
o Important to be exactly between you and the patient so the patients field can be compared to yours
Fingers more than 50 cm from patientà patients field will be underestimated/constricted
Fingers are less than 50 cm from patientà field will appear to be normal but you may be more likely to miss a defect/constriction
Present one, two, or four fingers in one of the four quadrants
Repeat for other 3 quadrants
Present both hands simultaneously in both superior quadrants
Present the fingers of both hands and ask patient to add together
o Do NOT use the same numbers in each hand
Repeat for OS
Record normal fields as FTFC (full to finger counting) OD, OS
o If not full, then document/draw constricted quadrant
Advantages
Sensitive to homonymous (neurologic) quadrantic and hemianopic VF defects
Fast and can be performed in any location
Can test for extinction phenomenon
Disadvantages
Results are not meaningful to the DMV
Sensitivity is not very high
Limits of the VF are not tested
O Field Limits
Compares known peripheral field limits to the patients peripheral field limits
Procedure
Patient removes spectacles and occludes OS; have patient fixate your nose
Move target (wand) from behind patient (non-seeing to seeing) toward the horizontal limit of the field
o Test slightly above and below the temporal midline
Have patient tell you when it comes into view
Do the same for the superior and inferior visual field
o Test on both sides of the superior and inferior midline
Test nasal side
o Test on either side of the nasal midline
Repeat for OS
Record limits (ALWAYS record from the patients perspective)
o Normal
Advantages
Provides a means to quantify confrontation fields
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Easier for patient to understand and/or respond
Disadvantages
Testing the limits of the VF produces variable sensitivity, therefore difficult to detect true visual field loss in the far peripheral field
Does not screen for extinction phenomenon
V Interpupillary Distance
o Distance between centers of the entrance pupils
Important for:
Alignment of optical instruments (avoids prismatic effects induced)
Spectacle design considerations
o Optical centers match PDs (if not, induces prism)
Documentation of craniofacial abnormalities
Measure monocular PDs for high powered spectacle prescriptions, PALs
o Procedure for binocular PD
Sit at eye level with patient ~40 cm away
Close your right eye and have patient look into your open left eye
Place zero at the temporal limbus of the right eye (DO NOT MOVE)
Note position that is aligned with the nasal limbus of the left eye: NEAR PD
Close left eye and have patient look into your open right eye
Note position that is aligned with the nasal limbus of the right eye: DISTANCE PD
Record distance/near
o Procedure for monocular PD
Place ruler on the patients bridge
Close your right eye and have patient look into your left eye
Align zero mark with the center of the pupil (CANNOT use pupil margin or limbus)
Note the mark centered on the bridge: OD MONOCULAR PD
Move ruler and place an easily recognized mark on the center of the bridge (use this as the zero mark)
Open your right eye, close your left, and have patient look into your right eye
Note mark centered in the patients left pupil; subtract the zero reading from the last reading: OS MONOCULAR PD
o Use Prentices rule to calculate the induced prism from decentration
P= dF
o Errors: unsteady positioning, error in parallax, patients with fixation disparities and doctors PD significantly wide (will overestimate)
V Ocular Dominance
o The preferential sighting of a target with one eye
o In monovision CLs fitting, the dominant eye is generally fit with the distance
o Useful when the subjective match in the clarity of the lines of letters cannot be achieved during binocular balance
Leave dominant with slightly clearer vision
o Do not leave the VA of the dominant eye worse than the non-dominant eye
o Place prism before the non-dominant eye
o Procedure
Instruct patient to fully extend arms and create a triangle with both hands
Patient looks through aperture at the doctors right eye
Eye aligned with the doctors is the dominant eye
Record ocular dominance
