7.1.7 Understands The Special Examination Requirements Of A Px With A Severe Visual Field Defect

Question 1

Steps to getting px into test room, and testing considerations

Answer 1

• may have to guide px or facilitate transfer into the test room
• remove any obstacles
• px may struggle to find test chart
• use large targets during cover test etc
• use large changes in power on subjective
• large fixation target on fields
• if px has agnosia, use landolt C
• estermann VF test to measure extent of peripheral visual field loss
• enlarged fixation target for perimetry

Question 2

Conditions causing gradual peripheral VF loss

Answer 2

• glaucoma
• retinitis pigmentosa
• choroideremia

Question 3

Conditions causing sudden peripheral field loss

Answer 3

• cerebrovascular incidents/hemianopia or quadrant defects
• brain lesions causing hemianopias can have other effects such as gemiplegia, agnostic, oculomotor problems behavioural changes

Question 4

Functional effects of a limited peripheral field

Answer 4

Distance
- poor mobility
- bumping into things
- navigation

Intermediate
- can’t view whole TV/VDU

Near
- reading, page navigation
- missing lines when reading

Question 5

Common causes of Central VF defects

Answer 5

• AMD
• macular hole
• CSR/CMO
• Macular dystrophy
• toxic maculopathy

Question 6

Functional effects of loss of central vision

Answer 6

• acuity loss
• distortion
• photo stress
• photophobia
• stereopsis
• colour vision
• Charles bonnet syndrome

Question 7

How to adapt routine to meet the needs of patients with central field loss

Answer 7

• perimeter, use peripheral spot to focus on as px will be unable to see central fixation spot
• change size and colour of fixation target for perimeter
• don’t use age matched thresholds
• use larger fixation target for ret, larger fixation target for cover test and larger 10mm red bead for confrontation
• good assessment of blind spot when doing confrontation
• compare sensitivity of red target across VF
• allow px to use CHP if they use eccentric viewing
• use large lens changes
• if also has reduced VA due to central vision loss, use larger bracketing steps during subjective refraction