I am scheduled to have lasik done this week and was just informed I have a 9 mm pupil size. The wavelight allegreto laser that will be used has a maximum treatable area of 8 mm.

I was told that the night vision problems would be no worse than what I currently experience with glasses (I have some halos currently but nothing that prevents me from driving comfortably at night). Is this typically true?

Several studies have shown that preoperative pupil size ALONE is a poor predictor of whether or not a patient will develop night vision problems, but when coupled with other issues – especially high refractive error correction - pupil has been shown to be an important point. I recommend that you read http://www.usaeyes.org/faq/subjects/lasik_pupil_size.htm

Also, be sure that the pupil size is the size of your naturally dilated pupil in a low visible light environment. Devices that take measurements in total darkness using infrared light (Colvard) actually report a pupil size that is about 1.0mm larger than would normally be achieved in lighting conditions wherein you could see.

Glenn Hagele
CRSQA
http://www.USAEyes.org

I am not a doctor.

Glenn,
I have to disagree with your statement.
First - one of the big problems that patients report is when they are driving in areas without steet lights. In this situation, pupils do get to the maximum size. So we should always carefully check the size of the pupil in pitch dark with devices like the Colvard pupillometer.
Second - there is absolutely no question that patients with larger pupils preoperatively are more likely to experience a larger size starburst postoperatively. We have shown that in our studies using the Colvard pupillometer and Larson Glarometer.
The reason that some "questionnaire" style studies do not show a difference in the risk of night vision problems after LASIK is because there are 2 major causes of night vision problems after LASIK - which each has a different treatment.
The most common reason for night vision complaints after LASIK is residual refractive error. In these patients - it is not the pupil size - but the fact that they are undercorrected or have residual astigmatism. The treatment for these patients is:
1. Enhancement
2. Glasses
3. Contact lenses
The other cause of night vision problems after LASIK is related to pupil size. In these patients - even after correcting their residual refractive error - they still have night vision complaints. The treatment for these patients is a medication to constrict the pupil. Alternatively, lasers can also expand the optical zone.

Since large pupil patients can have 2 potential causes of night vision problems (residual refractive error or pupil related night vision symtoms) - large pupil patients have a higher risk of night vision complaints. The Schallhorn study from 2003 confirmed this at 1 and 3 months postoperatively. Unfortunately - the Schallhorn paper had a 33% drop out for the one year data collection - and also startd with only 10 percent of patients with large pupils. So at one year, the difference between groups was reportedly not statistically significant.
Thankfully - Customvue guided treatments lower the risk of night vision complaitns in large pupil patients - so that is typically the way to go (wavefront or larger diameter treatments).
I hope this helps
Sorry for the long post

Bill Trattler, MD
Miami, FL

I would also like to add that I have treated a number of patients with pupil-dependent night vision disturbances with contact lenses following LASIK. In a recently published paper, I also demonstrated the relationship between optical zone size and spherical aberration. The problem with pupil constricting eyedrops like brimonidine is that they sometimes lose their effectiveness over time.

DrG

huge pupils like yours face increased risks of possible loss of night vision. This is more appearent with higher pescriptions. Its your choice if reducing dependancy on glasses is worth this risk