Mar 30 2010
If my contact lens prescription is almost the same, would my glasses prescription have changed?
My glasses prescription last year was -4.25 and -4.00 with moderate astigmatism in both eyes.
And my contact lens prescription last year was -4.25 and -4.25
This year my contact lens prescription has not changed. Does that mean my glasses prescription has not changed either? Also this is the first time it hasn’t changed. Does this mean my vision is finally stabalising? I’m 24, had glasses since I was 6/7.
Since your contact lens prescription was -4.25 in both eyes then it is a certainty that your astigmatism correction must have been just around -1.00 diopter. The reason for that is that once your prescription hits the power of 4 either as a myope (near sighted) or a hypermetrope (far sighted) a small correction needs to be made to compensate for what is called the vertex distance or the distance between your cornea and the lens of the machine that the eye doctor uses to examine you. So normally your contact prescription should have been -4.00 & -3.75 once corrected for vertex. However in your case the eye doctor elected to compensate for your astigmatism using a sphere equivalent so that he/she can keep your costs down and use a regular spherical lens to provide you with an acceptable vision result. The classic method with the sphere equivalent calculation is that you take 50% of the astigmatism and add it to the overall contact lens power. And so you have the final prescription that you are wearing.
on 30 Mar 2010 at 10:47 pm
I’m no optometrist, but I reckon if your contact lens prescription hasn’t changed your glasses prescription wouldn’t change either.
Why not ring your optometrist and ask?
References :
on 30 Mar 2010 at 11:13 pm
The eyeglass prescription is usually more precise than the contact lens prescription which is frequently a compromise. Sometimes the contact lens prescription stays the same, but a slight refinement can be made in the eyeglass prescription. So you never know.
At 24 you can assume your eyes are finally stabilizing, but again you never know.
References :
Consultant to: http://www.coloredcontacts.com/bigcolor.htm
on 30 Mar 2010 at 11:31 pm
Since your contact lens prescription was -4.25 in both eyes then it is a certainty that your astigmatism correction must have been just around -1.00 diopter. The reason for that is that once your prescription hits the power of 4 either as a myope (near sighted) or a hypermetrope (far sighted) a small correction needs to be made to compensate for what is called the vertex distance or the distance between your cornea and the lens of the machine that the eye doctor uses to examine you. So normally your contact prescription should have been -4.00 & -3.75 once corrected for vertex. However in your case the eye doctor elected to compensate for your astigmatism using a sphere equivalent so that he/she can keep your costs down and use a regular spherical lens to provide you with an acceptable vision result. The classic method with the sphere equivalent calculation is that you take 50% of the astigmatism and add it to the overall contact lens power. And so you have the final prescription that you are wearing.
References :
http://www.contactlensking.com/eyehealth.aspx