The College of Optometrists

Hi,Im due to resit my cdm exam in a few weeks and would like some advise to the following scenerio(which is what I had in my actual exam) px age 44,suffers from retinitis pigmentosa and is struggling with newspaper print. DVA re-6/24 le HM NVA bin N14 RX -7.00 R and L Normally for a presbyobic px I start with a +4.00 add at 25cm to give a unit mag and then work out the relative mag required for the optical aid.However, since the px is a high myope then I would have advised taking spex off and holding newspaper closer with no magnifier or since he could see N14 with spex(assuming at 25cm) should I have advised keeping the spex on if using a hand magnifier( approx x2mag since N14 /N8 )and taking them off when using a stand mag(approx x2mag)due to the emergent light from the mag.

please help!!!

the patient would need to hold the print at about 12cm for optimum focus without their spectacles, giving crude magnification of about x2, this is not enough for acuity reserve. You would need to give additional magnification for comfortable reading of at least x2. Theoretically you are correct on the vergences but practically I would suggest if the patient is comfortable using hand and stand magnifiers without spectacles.

if you didn't appreciate the extra magnification required for acuity reserve that might be where you came adrift on this one.

hi tim, was wondering if you can explain this in a bit more details how you got these values and also why using the myopic rx getting N14 and then adding another mag of x2 or even say x3 (N5)to give it that extra reserve cannot work. sorry am a bit weak on lv:-( thanks xx

how about something more simple like large print newspaper