LV: Quick Guide to Prescribing LVAs

DISTANCE (Snellen or Decimal)

BVA = starting point and TA = target acuity

M=BVA/TA

eg Px needs to see 6/12 but can only see 6/60
M = 60/12 = 5x mag required

Available LVAs

• Telescopes
• Monoc
• Binoc
• Fixed focus
• Variable focus
• Autofocus

NEAR

eg Px can see N24 at 25cm with +4.00D add and needs to see N12
M=24/12 so 2x magnification needed

Choice of magnifier

• Keep it as simple as poss
• Start with lower mag if poss as it allows a bigger FOV and a longer working distance which makes it easier to use
• Consider illumination
• Consider the task, the age of the patient (also physical infirmities) and the cost

Magnifiers available

• Brightfield/Paperweight
• Illuminated stand
• Stand
• Illuminated hand
• Hand
• Spec mounted - binocular or monocular