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Pupil Size and Laser Eye Surgery

The size of your pupil can vary from 2mm to 8mm depending on the natural accommodative power of your eyes and whether you are in bright (2-4mm) or dim (4-8mm) light conditions.

 

While you might think the pupil is just a big black opening in the centre of your eye that gets bigger or smaller at any given time, the truth is your pupils are responsible for controlling the amount of light allowed into the eye.

 

Surrounded by the iris, which gives your eyes their colour, the pupils contract and relax depending on the intensity of outside light.

Why do pupils change size?

Your pupillary reflex is controlled by the autonomic nervous system in the body, which instructs the muscles in the iris to either constrict or relax depending on how bright or dark conditions are.

 

Dilator muscle: Shrinks the iris when in low levels of light. This makes the pupil appear larger in order to allow as much light as possible to shine on the back of the eye.

 

Sphincter muscle: Expands the iris when you find yourself in bright conditions, so the pupil contracts and less light can infiltrate your eye.

Why does pupil size matters when it comes to Laser Eye Surgery?

Pupils are normally equal in size, but there is a condition called anisocoria which is when one pupil differs in size from the other.

 

Some people naturally have larger pupils and sometimes certain medications can cause pupils to become larger, especially in dim lighting.

 

Taking an accurate measurement of a prospective Laser Eye Surgery patient is extremely important as some corrective procedures aren’t suitable.

 

During your free consultation, pupil size will be measured in dark conditions so that the pupil is fully relaxed and at its largest.

How larger pupils can react to Laser Eye Surgery

There is a greater chance of night vision being affected in patients with large pupils, which can cause glare, halos or starbursts.

 

However, advances in laser technology have adapted so that those with large pupils can undergo Laser Eye Surgery safely.

 

The WaveFront procedure in particular is ideal for larger pupils as a 3D map of the corneal surface is taken when the pupil is fully dilated.

 

Corrective treatment is then programmed to correct every error on the cornea without negatively affecting night vision ability.

 

To find out more about WaveFront or any other corrective procedure, book your free consultation on +353 1 223 8821.

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Patient Reviews

Margaret Mc Clafferty
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Margaret Mc Clafferty
August 29, 2026

I had LASIK done in Dublin after a consultation and follow up in Derry. From the very start, Elizabeth in Derry put me at ease with her approach. Such a warm, helpful way about her. Surgeon Mikhall Hernandez took the time to meet me in advance to explain the process. All the staff- Iwona, Julie, Jess, Robbie (from Donegal!) and Rachael, I really appreciated the way they supported me from start to finish

Aline Bortolotti Secco
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Aline Bortolotti Secco
July 31, 2026

I had a great LASIK experience at Optilase Carrickmines and couldn’t be happier with the results. Dr. Tom Materman is incredibly kind, attentive, and made me feel comfortable throughout the entire process. I highly recommend him, as well as the whole Optilase team! I didn’t feel anything during the procedure, which was much easier than I expected. My recovery has also been going really well—I’m only on day two, and everything has been smooth so far. Thank you to everyone at Optilase for the excellent care!

Carl Thorne
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Carl Thorne
July 28, 2026

Life changing. From the initial consultation to the aftercare, Optilase have been friendly, professional and caring every step of the way. No worry or concern was too small for a detailed discussion and helpful response. 3 months after my phakic lens surgery my vision is as good as it ever was with glasses without the hassle. Would recommend the Optilase Carrickmines team to anyone.

Colm Smith
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Colm Smith
July 28, 2026

Very happy with the operation, results and the aftercare

Gerard Mcphillips
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Gerard Mcphillips
July 24, 2026

Very professional and appointments on time

D
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D
July 24, 2026

Great team, great experience. Anyone thinking about doing it, do it. Always on the end of the phone if there was any issues. Highly recommend!

jason farrell
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jason farrell
July 23, 2026

The entire process was smooth professional and completely stress free, I couldn't be happier with my outcome

Tara Dowds
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Tara Dowds
July 22, 2026

Excellent experience in the Cork clinic. Dan O'brien explained everything so throughly. I really appreciated the consultation.

Michael Britton
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Michael Britton
July 22, 2026

Absolutely brilliant service from consultation through to surgery and aftercare. The whole team are really friendly and efficient. Would recommend to anyone thinking about getting corrective surgery.

Majella Murphy
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Majella Murphy
July 22, 2026

Excellent service and care. Laser eye surgery went well and have had no issues. Highly recommend Sinead and the team in Optilase Cork

Saidhbhe OShea
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Saidhbhe OShea
July 21, 2026

Highly recommended the team in the cork clinic. Very professional and friendly throughout the whole process.

wiktoria szmerdt
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wiktoria szmerdt
July 21, 2026

Lovely staff, very knowledgeable, made me feel calm and comfortable during my consultation

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