AAOO Challenge

Rules of the challenge:

1. To qualify you must be practising in Australia or New Zealand and be eligible for registration into a AAOO CPD course.

2. No online or app based lens calculators may be used (they make assumptions on the lens parameters, so we can tell if you’ve been sneaking!).

3. Working must be shown in full.

4. The answers between the two techniques must match within three decimal places of one another and our answer (answers in mm for distances and thickness and cubic centimetres for volume). We were able to get our answers matched to 16 decimal places, so we know it’s possible. 🙂

5. Email answers to enquiries@aaoo.net.au 

6. The first person to get the challenge correct wins the prize. The winner will be announced on social media via the AAOO Facebook page once their submission is confirmed correct.


50% off the full registration cost of one AAOO course.

If anyone wishes to see the techniques, registrations are open for the first course now. This particular concept is covered in one of the modules. Please note that the level of this challenge is far higher than what the assessment tasks in the courses will be, so don’t worry. It is more indicative of the knowledge and skill to be attained by practitioners who wish to become experts in ophthalmic optics. 


A patient presents to your practice to update their spectacles. There has been no prescription change but due to a different sized frame, the MSU (minimum size uncut) has increased. The patient is very concerned about the weight of the new spectacles and wishes to know how much difference there will be between the old and new lenses.

We understand that there may be differences in shape between the frames so we have simplified the boundary conditions. Given only the parameters below and disregarding the frame shape (i.e. just considering the uncut blanks required for the old and new lenses), what is the increase with regard to:

1. Thickness 

2. Volume

3. Weight 

The parameters are:

F’v = +4.00DS

F1 = +6.00D

F2 = -2.105D

n = 1.498

ØOLD = 65mm

ØNEW = 70mm

While there are many ways to address these types of problem there are two methods that will give the desired result we are looking for, a geometric (Euclidean) solution and an integral solution. Both methods must be shown in your solution and relevant development of your path to the answer shown to win (in short, give enough proof in your proof!). Have fun!

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