over-minused contacts

Lurking in alt.lasik-eyes I read the term "over-minused". The reason
for it is over my head but sounds like what was done with my contacts.
One eye sees well for distance but not for reading. The other eye
sees well for reading but not for distance. My reason for RGP
contacts is a poor LASIK outcome. I can't see well enough to drive
after dark unless I'm wearing the contacts. The problem is large
starbursts emanating from every headlight, reflecting off chrome or
even off water in the street. The over-minus contact controls the
starbursts better than the "under-minused" lens. Since I have two
pairs of contacts I wear the over-minused in each eye. That makes
driving easier but means I need reading glasses to follow a map.

I've been told the reason is the lasered area is smaller than the
nighttime pupil. If that is so, why would contacts help? The pupil
is the same regardless of which contacts I wear. The contacts are
11.5mm diameter.

 

Too-strong contacts mean your eyes have to focus a bit more (accommodate) to
see; accommodation is linked with pupil size (more accommodation = smaller
pupil size, to give a greater depth of field); therefore the stronger
contacts give you slightly smaller pupils. Also, the RGP contacts create a
new optical surface which tends to "iron out" any irregularities in your own
post-lasik corneas which might be contributing to your problems.

Dom

 

"Over minused" means that your glasses or contact lenses have more minus
power or less plus power than your cycloplegic refraction. A person who is
over minused may see well at both far and near. It is important in LASIK
because the surgeon wants to correct the cycloplegic refraction, not the
habitual overminused refraction

The situation you describe is called monovision, used for presbyopes wherein
one eye is given the correct distance correction and the other eye is over
plussed (less minus, more plus than needed) to allow for reading. I am
guessing you are over age 40. If both your contacts were set to the correct
distance refraction, you would need reading glasses over them to read.

http://www.mayoclinic.com/invoke.cfm?id=HQ00123

My reason for RGP

Likely neither lens is over minus. I'm guessing that after LASIK you were
left with mild myopia, ie the surgery did not fully correct your myopia.
During the day, when your pupil is small, depth of focus effects make your
vision acceptable without glasses. At night, when the pupil is larger you
lose your depth of focus and then need your myopia correction. Uncorrected
myopia will cause starbursts etc.

That makes

As stated earlier, if over age 40, you will need reading glasses when your
distance vision is fully corrected.

The unlasered area still has your original myopic refractive error and the
contacts contain myopia correction.

Dr Judy