Help with contact lenses!!!

[stephanie]

I am studying for the NCLE and am having some trouble with converting mm to Diopters. Are there any tips someone out there can give me. I thought the Abo was hard it has nothing on the NCLE! Also does anyone know of anywhere on the internet some of this stuff might be that might break it down for us slower folks!! LOL!!
Thanks for all help in advance!!
Steph

[chip anderson]

Stephanie:

Almost anyone but me, (My first job in the CL mfg. business was making base curves and I memorized all the common ones) uses a chart. Almost all CL catalogues include same but here is some help.

1) As dioptric value increases the base curve becomes shorter in mm. ex: 40.00 dio is flatter than 46.00 dio.
2) Common ones: 45.00 = 7.50 mm. 43.00=7.85 mm. 42.00=8.04 mm 44.00=7.67 mm. 46.00=7.34 mm.
3) Now in the mid-range 42.00 to 47.00 1/4 dio= .04 mm. In the flatter curves approx. .05 mm = 1/4 dio. and in the very steep ones, .03 = 1/4 dio.
4) What all this means is that if you will memorize only those mentioned in 2) and add .02 mm for every 1/8 dio. flatter or subtract .02 for every 1/8 dio. you can easily calculate almost anything you need.
5) For very steep curves (over 47.50) or very flat ones (below 40.00) consult a chart like the rest of us.

Chip

[Maria]

As I understand it, and bearing in mind my contact lens component isn't until 4th year, a dioptre is 1/metre, so if you have 20 cm focal length, 1/0.20 = 5 dioptres. And obviously it is fairly simple to convert cm into mm.
Do not believe this until someone more credible (EG anyone) has backed it up, though.

------------------
Maria "no amusing quote" K

[Shwing]

Actually there is a very easy formula to convert from radii to diopters, and vice versa. The funny part is that it is not in any text I have come across.

337.5

The index of refraction of the cornea is 1.3375

This is basis for the formula.

Formula: 337.5

That is, 337.5 divided by EITHER you dioptric measurement, OR your millimetres of radius, will instantly convert to the other corresponding mesurement.

Charts are for wussies.

Shwing;-}

[stephanie]

Thanks so much everyone. I just knew I could count on you guys to make more sense out of it.

Have a great day!!! I am going to go try my new found info.
Steph

[stephanie]

Yippie!! It works Shwing!! I tried it every which way and it absolutely does indeed work!! Thank you so much you have saved me so much aggravation!! Now if I can only remember how to do long division on the test without a calculator. HMMMMM....Anyway thanks everyone all info was very helpful.
Have a great day!!
Steph

[Shwing]

Stop, you're making me blush...

Just send beer...

You are welcome.

Shwing;-}

[stephanie]

Just send beer huh??? Sorry not old enough to buy it!! HAHAHAHAHA!!! I do appreciate the help.

Steph

[ashish]

Hi . I have this simple chart with diopter to mm conversion in the range of 39.00D to 50.00D. Give me your e mail I will mail it to you.

[Optom]

Hello Ashish,
Tell me something about optometry in India.
You said you hold degree in optometry from AIIMS,is this degree in Optometry Technology?
Is the profession of optometry a regulated profession in India?
What is Delhi Optical Association,is their qualification a recognised one?
I want to know about optometry practises in India.I am on international committe of Asia Pacific Optometry Congress 2003.Your information will help.You may email me information on: eye.sight@usa.net
Thanks
Shabbir