Fused Cross Cylinder (FCC) Flashcards
What scenario would require FCC?
Near vision blur
Mostly during near work (excluding computer and driving)
No history of spectacle wear
42 y/o
What is the purpose of FCC?
Measure accuracy of the accommodative response (lead or lag)
Used to aid in determining near Rx
What is the illumination, target and correction required for FCC?
Dim illumination
Proper distance refraction on phoropter
+/- 0.50 cross cylinders
Set of vertical and horizontal lines on near card at 40cm
Describe the steps for FCC?
Converge phoropter
Ask patient which set of lines is clear, blacker, more distinct
What should be done is the patient reports horizontal is clearer, blacker and more distinct?
Add plus lenses binocularly until lines become equal
What should be done if the patient report vertical is clear, blacker, and more distinct?
Add +1.00 binocularly
Ask again
Vertical: add -0.25 binocular and repeat until the two lines become equal. If you return to the baseline and the patient reports vertical, record that the patient is a minus projector.
Horizontal: add +0.25 until the two lines become equal
What should be done if the patient’s results go from horizontal to vertical?
There is no real equal
Record ending point with patient’s response
What is the normal results of FCC for presbyopic and non presbyopic patients?
For non-presbyopic patients: +0.50-0.75 this corresponds to a LAG in accommodation.
Presbyopic patients, the result will be larger and can be used for a near base
How are results for FCC recorded?
Patient reports horizontal, +0.25 added OU Patient again reports horizontal, +0.25 added OU Patient now reports vertical
Result: FCC: +0.50V or +0.25H can be recorded.
Describe what minus projector and no plus acceptance means?
Minus projector- if patient accepts minus beyond +1
Plus- If patient says equal ones +1 has been removed
