The College of Optometrists

Hi, can anyone help with these questions i had in my first exam

1. How do you hand neutralise a lens?

2. Tell me about brittish standards? (not really sure how much info they wanted on this)

3. What are the highest ref. indices for glass and plastic lenses?

Any help at all will be greatly appreciated!

1) The lens is moved in front of a large cross. Whilst looking through the lens you are looking to see whether the part of the cross that you can see through the lens is moving WITH or AGAINST your movement. You then neutralise accordingly, ie use a plus lens for with and minus for against. For a toric lens, neutralsie each meridian in turn,

2) Not sure how much info they would have wanted, but I assume its to do with Rx tolerances - ie how mch can the axis be off on a -1.00DC for it still to be accepted by the lab as being OK

3) Highest in plastic is 1.74 and in glass is 1.9

I think you will need tollerences and also know about safety spex. I will get you a tollerences chart tomorrow - but the college library will provide you with a link to look at BS on line.

hand Neutralisation needs tons of practice - so do it as much as poss. Get into the habit of wiggling all the glasses you can to see if they are with or against

thanks for the help guys, its been so long since i hand neutralsied a lens i totally forgot

Dont forget for British Standards any rx over +/- 5.00DS needs a back Vertex Distance.