Enhancement questions

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Enhancement questions

Postby poolmaniac6 » Fri Jan 19, 2007 11:17 pm

5 months post Epi-Lasik and I continue to have issues at night and indoors. It seems that my pupils are getting bigger than both the optical and ablation zones. If I remember correctly I was given an Orbscan??? during my initial consulation that among other things was used to size my pupils - which was 5.5mm. During subsequent visits to my doctor's office in addition to the orbscans I was measured using a pupilometer????? device which has shown all three times that my pupils measure between 7mm - 8.5mm. My first question is why was I not tested with the pupilometer the first visit and is this something that all Lasik surgeons should do?? It sure would have been nice to have been given the information on risks at night because the starburst that I see are HUGE!!!!!!!!!. Second and more important question - would an enhancement that increases my optical and total ablation zones help and be worth the risks? I see 20/20 during the day with my left eye. Right eye is a little worse during day and horrible indoors and at night. I have been using Alphagan drops occasionally and these seem to help a little. But it really is not pleasant having to choose what 3 or 4 nights per week I get to see properly. I have only been using them 3 or 4 times per week because I have read that the pupil shrinking effects could wear off. I have also tried the Pilocarpine drops and would only use these again as a last resort - they really stung my eyes on top of making my vision blurry for about an hour. I am really frustrated with my surgeon about lack of pupil testing before surgery but I realize I have to continue working with them to help resolve yhese unkind side effects. Any info on possible enhancement would be greatly appreciated.
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Postby LasikExpert » Sat Jan 20, 2007 3:33 am

For those who are not knowledgeable about these issues, we have an article about Lasik pupil size issues.

An Orbscan is really not the best tool for measuring pupil size. The pupilometer measures the size of the pupil in a totally dark environment by using infrared light. Because the environment is totally dark the pupil measurement with an infrared pupilometer tends to be about 1.0mm larger than would occur in normal low light environments where you would be expected to be able to see.

Some doctors are not terribly concerned about pupil size if you present at examination with normal sized pupils and if you are either a low myope (nearsighted, shortsighted) or just about any amount of hyperope (farsighted, longsighted) because pupil size alone is a very poor predictor of who will develop night vision problems. That does not mean that pupil size is unimportant - very large pupil size with a high myopic refractive error can be very important - it just means that pupil size alone is a poor predictor of night vision problems. If you read the referenced article above you will see a rather conservative explanation about this issue.

When you actually have night vision problems, the reduction of the size of the pupil with Alphagan P or pilocarpine can be very helpful for two primary reasons. One is the pinhole effect. Small pupils give a pinhole effect that increases the depth of focus and reduces the amount of light that passes through areas of the cornea that may be aberrated or a bit off focus. Your effect with small pupils may not totally be caused by an ablation zone too small. There may be other factors at play, but your doctor can better advise you on this than I.

Another reason a small pupil can help night vision problems is due to a higher order aberration (HOA) called Spherical Aberration (SA). SA simply means that the center of the visual axis has a different refractive error than the edge. A wavefront diagnostic will measure your SA, but it needs to also be done with the pupils naturally dilated. An increase in HOA and SA with larger pupils is normal with or without surgery, but your doctor can determine if yours are unusually elevated. My bet is that your SA is significantly higher than normal, but if it is not then your assumptions about pupil size may be partially incorrect.

You are assuming that you are more myopic at the edge of your corneas than in the center due to a treatment zone smaller than your pupils. That is a reasonable assumption based upon your symptoms, but that may not be the whole story.

You mention that your vision is poor in daylight. That indicates either an aberrated cornea (dry eye, rough laser ablation, striae) or simple refractive error. Even 0.50 diopters off target can provide poor vision quality and that quality will exponentially reduce as the pupils get larger.

It is possible that Lasik enhancement surgery to enlarge your optical treatment zone will help your problem, but I think it would be wise to first verify how much of the problem is just refractive error. This can probably be best tested with contact lenses. Contacts will give a reasonably good indication of what improvement (if any) you could expect for Lasik enhancement. Widening the treatment zone would probably provide a bit more improvement than just contacts.

I cannot possibly tell you if the potential benefit is worth the potential risk, but at least with a pair of contacts you would get a rough idea of what the benefit may be.
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Postby DemEyes » Sun Jan 21, 2007 11:10 pm

Contact lenses sound like a good option for you.
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Postby poolmaniac6 » Thu Feb 15, 2007 12:06 am

Would this likely have to be hard contacts?
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Postby LasikExpert » Thu Feb 15, 2007 5:35 pm

Commonly soft contact lenses would be tried first to see if they are able to provide the needed vision improvement. If they do, there would be no need to progress to the more expensive and sometimes less comfortable rigid gas permeable (RGP) contact lenses. If the soft lenses don't provide the needed improvement, then RGPs would be the next step.

There is a new hybrid contact lens that is RGP in the center and soft on the outer edge. If the soft lens does not work well, you may want to discuss with your doctor if this lens would be appropriate.
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Postby carmen123 » Tue Apr 03, 2007 2:36 pm

Because my left eye is measuring at a -1.75, I'm scheduled for an enhancement.

My right eye, however, is measuring at -.25, but I still have bad night and dim light vision.

Would a wavefront diagnostic to measure SA be appropriate for my right eye? I would like to determine if my bad vision is due to a small treatment zone, or something else. If my vision problems are due to SA or treatment zone, would an enhancement help this?
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Postby LasikExpert » Tue Apr 03, 2007 4:34 pm

If your right eye is healthy in all other aspects, then a wavefront diagnostic may be usefull in determining the cause of the poor vision quality. If the poor vision quality is due to dry eye, allergies, inflammation, or other ocular health related issue, a wavefront diagnosis will provide inaccurate optics data.

Enlargement of the optical ablation zone has been helpful for some patients who have poor night vision problems. Whether or not it would be helpful for you and whether or not wavefront-guided enhancement would be appropriate could only be determined by a surgeon.
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I am not a doctor.
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