I’d be careful with ‘treatment zones’ and ‘optical zones’ and any other terminology when reading laser doctors’s websites. Most (all?) lasers have a primary zone where the full-prescription treatment is applied, and then a tapering zone in which there is lasering, but which does not have the full prescription applied. Only the primary area (‘optical zone’ I often hear it called) matters. And if it’s smaller than your pupil size, you will be subject to halos in certain situations.

I am not super familiar with the suite of lasers, but I did find the following after googling ‘Star S4 IR laser treatment zone’…

First, from the FDA’s website, is a document from the Star S4′s approval process (which was in 2003, so fairly old): https://www.accessdata.fda.gov/cdrh_docs/pdf/P930016S016b.pdf

It lists a 6.0mm ablation zone (presumably with a larger taper area). Pretty standard in lasers of that era.

I understand that some of the newer lasers can have larger optical zones, but I’m not familiar with them.

Second, I found this thread on reddit discussing the S4 laser. One user comments with a few suggestions of lasers with larger optical zones: https://www.reddit.com/r/lasik/comments/7eubpy/visx_star_s4_ir_treatment_zone_question/

/u/LilaLaLina: “Definitely don’t do it with that laser. Go for a treatment that uses a full 7.5mm optical zone and blends to 9.5mm. LASIK, PRK or SMILE with more modern lasers from Zeiss, Wavelight or Schwind should be able to give you a proper treatment.”

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As for halos themselves, I wrote an article which should answer a few of your questions:

http://www.isthisyourhomework.com/halos-likely-complication-prk-lasik/

Specifically with your question about fear/anger dilation, I don’t think you’ll have to worry about that much (at all?).

Halos related to pupil size are caused because the pupil expands larger than the optical zone, so some of the light entering the pupil is not corrected for your prescription. This light is shone blurry on the retina instead of in focus (like your uncorrected eye). So, you get halos of uncorrected light overlapping the in-focus light hitting your eye.

In practice however, there is quite a bit less uncorrected light entering the eye than through the corrected area of the pupil.

For example, a 7.5mm pupil only has 25% of its surface area outside the 6mm diameter inner area, while a very large 8mm pupil has 44% of its area outside the 6mm.

I suspect bright-light dilation of your pupil would rarely (if ever) get to quite that large, but even then, the light is far overpowered by the light entering the corrected area of the pupil.

And because the uncorrected light is diffused much more than the corrected light (it’s blurry and spread out), the brightness of the halo is reduced quite a bit from those 25% and 44% numbers. So, the halo-light is much dimmer than the source light, and if the ‘spillover’ halo-light overlaps other light image, it’s going to be very hard to notice.

Really the only time I’ve ever seen haloes is when driving at night on a dark road with no street lights. I’ll get halos on oncoming headlights, reflectors, and on street/road signs with high-reflective paint (never from a non-reflective surface). It’s never so bad that I cannot read a small roadsign in the dark, but I do see the halos around them.

Those are the only conditions where my pupil is larger than my optical zone (even a few orange streetlights are enough to dilate my pupil enough), and when the ‘spillover’ uncorrected light is brighter than the pure darkness outside the bright point-source of light.

I knew going into my surgery that my pupil could dilate larger than my optical zone, but I decided for the above reasons that I’d be okay with it. To be honest I didn’t notice the nighttime halos until I moved to the country. Nowhere in the city at night was it dark enough for my pupils to fully dilate while out and about. The one place I did notice halos was in my bathroom with no windows. It could get pitch-black, and I had a small green LED on a charger that would halo. If I turned my phone screen on and pointed it at my face (not even directly or all that close), that would provide enough ambient light to dilate my pupils and make the halos disappear. I had fun with it. :) “Honey, what are you doing in there?” “Playing with my pupils!”

Now that I live in the country, I see halos quite a bit when driving on very dark roads when there’s a reflector or reflective street sign. I can make them disappear by turning on one of the map-lights in my car. When I do that, I can still see outside the car very well, so the light isn’t super bright, and it’s fun to watch the halos shrink into the point-light sources as my pupil contracts. My halos are never more than an amusement to me, and I don’t feel any need to mitigate them. And I don’t really notice them, except when I’m playing around with them again. :)

Does that make a certain amount of sense?

which i put my face inside this machine and i saw full dark inside with one red circle in front of my eyes and the room lights was turned off also.

when i asked about halos , she said that i may see halos just if in total dark room as the dark in i saw in the machine.

i know that Schwind optical zone is 6 mm. so Im worried that my full dilated pupil is 7.5 .
cuz what if my pupil is dilated in other situations ? when we get happy or angry or excited our pupil also gets wider.
or do you think in these other situations the pupil doesn’t be full wide.
or I should better do my laser surgery with a clinic that uses Star S4 IR laser which i think it can have optical size up to 8 , is that right ?

I have planned for some touch up PRK due to over correction in cataract lens RX.
Best from Colorado

I don’t really have anything to add to the conversation, I just wanted to say that I’m very very happy I found your page. I am now feeling very relieved that LASIK is not an option for me, because if it was, I probably would have gone through with it! Strangely enough, I’ve been putting it off all these years because I was scared of that flap (which I’ve always known doesn’t heal). And, if this isn’t serendipity, I don’t know what is – had I done a LASIK consult several years ago when I first considered it, the damage to my cornea probably wouldn’t have been done yet, I would have been a good candidate, and I would have gone through with it, AND I’m sure I would have had a complication by now as I’m a very active person. (I kayak, I have small children, and I have a very bad eye-rubbing habit.)

Anyway, my vision prescriptions have been mostly stable (I think it changed slightly last year but not the two years before, or something like that), so I’m hoping to go through with the PRK here in the next couple of months! I’m so nervous but you’ve made me feel loads better, so thanks for that. :) Cheers!

I couldn’t say thank you enough for your post. I was on the fence about this surgery for two years and only till after reading your post, I have a much better idea of what I will get through the surgery.

Still, I have several questions please. You mentioned that there are lots of laser surgeries and I am wondering are there different types of PRK surgeries as well? If so, what are they?

Also, could you give me an idea of how long after the surgery I can use computer all day for work?

Thank you so much once again!!

Jojo

Thanks for a wonderful writeup – easily the most informative blog on refractive surgery I’ve been able to find.

I’m due for Epi-Lasik in a week and I’d like to learn more about your experience with the steroid drops regimen. How specifically was the dose/frequency adjusted based on your day-to-day recovery? I believe I won’t see my surgeon post-op until the 5th or 6th day to get the bandage removed, and I wanted to see how I can do to enhance my chances.

Many thanks for your help!
Wesley

I’m considering PRK and came across your comment. It’s been a few years but I’m curious – how are you doing now?

I would never have a corneal-flap operation.

I am also considering to undergo corrective eye surgery but I’ve been having a lot of concerns over the overall safety and which type I should choose. I went in for a consultation and the doctors never told me that the corneal flap never heals, until I read your post. That really worries me.

During the consultation, the clinic told me about a new laser treatment called IntraLase SBK. They say that “this is a hybrid procedure which combines the safety of PRK as well as the quicker recovery of LASIK.” Two lasers are used – one is to create a flap (without the blade that LASIK uses) and the other to correct the vision after the flap is opened. The doctors told me that the infra red beam creates a much thinner, tailor-made flap that’s superior in structure to a conventional LASIK flap.

I was wondering if you know any information about this third type of laser treatment – IntraLase SBK and if this would be the preferred choice over PRK and LASIK. Any information that you may have is very much appreciated. Thankyou!