Pupil Related Studies & Articles PDF Print E-mail

Pupil measurement using the Colvard pupillometer and a standard pupil card with a cobalt blue filter penlight - To compare scotopic pupil measurements obtained with a Colvard pupillometer with measurements taken with a printed pupil gauge and penlight with a cobalt blue filter attachment in mesopic and scotopic luminance.

Influence of pupil and optical zone diameter on higher-order aberrations after wavefront-guided myopic LASIK - To investigate the influence of pupil and optical zone (OZ) diameter on higher-order aberrations (HOAs) after myopic wavefront-guided laser in situ keratomileusis (LASIK)

Pupillary Dilation

1) Pupillary dilation from 3 to 7 mm in post-refractive surgery patients found to cause 28- to 46-fold increase in aberrations! - Both photorefractive keratectomy and laser in situ keratomileusis increase the wavefront aberrations of the cornea and change the relative contribution of coma- and spherical-like aberrations.

2) Pupillary dilation from 3 to 7 mm in post - PRK patients found to cause 25-to 32-fold increase increase in aberrations! - After surgery, the same dilation resulted in a 25- to 32-fold increase in the photorefractive keratectomy group and a 28- to 46-fold increase in the laser in situ keratomileusis group.

Pupil Size

Pupil size and night vision disturbances after LASIK for myopia. - Large pupil size measured preoperatively is correlated with an increased frequency of subjectively experienced post-LASIK visual disturbances during scotopic conditions.

Large pupils lead to night vision problems, physicians suggest




November, 2005


While some studies have suggested pupil size has little to no effect on nighttime vision post-refractive surgery, some ophthalmologists point to new evidence that there is a correlation.

“If you compare patients of the same prescriptions, the larger the pupil size, the bigger the chance that they’re going to have more night vision problems,” said William B. Trattler, M.D., Center for Excellence in Eye Care, Miami.

To back up his assertion, Dr. Trattler performed his own studies, one of which included 119 myopic eyes that underwent LASEK or PRK with either a standard VISX (Advanced Medical Optics, Santa Ana, Calif.) Star S3 or S4 laser.

Using a Larson Glarometer, he found that the radius of starbursts was greater in patients with large pupils compared with those in patients with small ones. Dr. Trattler presentedthe results at the most recent ASCRS•ASOA Symposium & Congress. The Larson Glarometer does not have a corporate manufacturer yet. It was developed and is distributed by Bruce Larson, M.D., Hinsdale, Ill.

Meanwhile, James Salz, M.D., clinical professor of ophthalmology, University of Southern California, Los Angeles, also believes large pupils can lead to night vision complaints after refractive surgery.

“The larger the pupil size, the greater the aberrations will be,” said Dr. Salz.

Pupil diameter changes and reaction after posterior chamber phakic intraocular lens implantation - To compare the different aspects of pupil constriction before and after the implantation of an implantable contact lens (ICL).

Effect of pupil size on visual function under monocular and binocular conditions in LASIK and non-LASIK patients - To compare binocular and monocular vision in patients treated with laser in situ keratomileusis (LASIK) and in non-LASIK patients.

Pupil Size


"Night Glare is common in nearsighted individuals even before any refractive procedure is performed, but increases almost immediately in the healing process and is more common when only one eye is treated. Typically, 6 months after both eyes have been treated, only 2% of patients still experience significant night glare that interferes with their night driving. Severe night glare can impair vision in all reduced lighting conditions producing blurriness, ghosting, or halos. Patients with large pupils and severe myopia and/or significant astigmatism are at greater risk for night glare."






From the FDA website, "When is LASIK not for me?"


Large pupils. Make sure this evaluation is done in a dark room. Younger patients and patients on certain medications may be prone to having large pupils under dim lighting conditions. This can cause symptoms such as glare, halos, starbursts, and ghost images (double vision) after surgery. In some patients these symptoms may be debilitating. For example, a patient may no longer be able to drive a car at night or in certain weather conditions, such as fog.

From the American Academy of Ophthalmology website:


Summary Recommendations for LASIK

Issued March 28, 2002

Patient Examination

In determining suitability, a baseline eye evaluation should include:

Manifest and cycloplegic refraction

Measurement of intraocular pressure

Slit-lamp biomicroscopy

Tear film evaluation

Corneal topography

Evaluation of preoperative corneal thickness

Dilated fundoscopic examination

Measurement of scotopic pupil size

Somebody should report doctors who operates on patients with large pupils to the AAO for violating AAO guidelines.  (Not that the AAO is going to do or say anything about it!)

From the ASCRS Eye Surgery Education Counsil website, LASIK Patient Screening Guidelines:


• Measurement of pupil size in dim and room light. Pupil size is an important factor in counseling a candidate about night vision and planning the appropriate laser vision correction strategy.

Even the insurer, OMIC, requires pre-op pupil measurement.



As part of the independent evaluation, the surgeon must personally examine the patient’s eyes and ocular adnexa, perform a slit lamp exam, and carefully review topographies, pupil size, pachymetry, refractive stability, eye health history, and prior records.

Notice it said "the surgeon must personally examine the patient's eye..."

From the Federal Trade Commission website:


Take the following measurements:

The curvature of your cornea and your pupils. You may be rejected if your pupils are too large.



"Aberrometry depends on pupil diameter, as well. HOAs disturb vision increasingly with increasing pupil diameter."

FDA Ophthalmic Devices Panel meeting

August, 2002

Dr. George Pettit is speaking on behalf of ALCON for approval of it's wavefront guided platform.


DR. PETTIT: Just to follow up a little bit on an earlier question. This is George Pettit from Alcon.

I think Dr. Matoba asked the question about the pupil sizes and were the patients informed. Given this high-level expectation, it's important to note that the optical zone was 6.5mm and we informed all patients considering being in the trial that if their natural pupil was larger than 6.5mm, even with this new technology, there was a potential risk for them to have night vision symptoms. So we tried to bring their expectations more in line.



"With the cornea being 70% water, highly customized treatment is like trying to precisely sculpt Jell-O. Even when everything is done perfectly, creating the LASIK flap and the normal effects of corneal stretching, molding or healing may negate some of the precision of the planned treatment."


Brian Boxer Wachler, M.D. on pupil size:


Halos were associated with spherical aberration for the scotopic pupil size.

“I find this as well,” Dr. Boxer Wachler said. “The reason is that if you look at the very center of the topography and look towards the periphery, the corneal power gets steeper. If the steeper power transition occurs relatively close to the center of topography – as in higher myopes, and/or smaller laser optical zones – this causes more spherical aberration.”

Glare also was significantly correlated with spherical aberration and total aberration. Starburst was associated with spherical aberration and total aberration for the scotopic pupil size.


If you choose LASIK, Boxer Wachler suggests asking the surgeon if the procedure is safe with your pupil size, because people with large pupils are at greater risk for decreased night vision and halos (the glare that appears over certain objects).

Dan Durrie, MD on pupil size:


"Another possible cause of nighttime side-effects is pupil size. At night, the pupil expands to let in more light. Light coming through the peripheral cornea may be out of focus if the pupil opens beyond the laser treatment area. This is why some patients are not good candidates for LASIK if they have very large pupils."

Barrie Soloway, MD on pupil size:


"Most patients with large pupil sizes who receive laser surgery will experience varying degrees of what's referred to in the medical field as GASH (Glare, Arching, Star bursts or Haloes) during night-driving. "


"This study proved that the main reason for poor post-LASIK night vision was in fact the diameter of the laser beam being smaller than that of the pupil."

Jack Holladay, MD on pupil size:


The High Cost of Inaccurate Pupillometry

 "Accurate pupillometry is an essential part of the evaluation for refractive surgery. With reports of halos and glare following refractive surgery on many of the prime-time news shows, pupillometry has become one of the preoperative tests that patients expect. It is very clear from the published and anecdotal reports of nighttime glare and halos that a large pupil is the predominant factor leading to these problems." 

Pupil diameter study shows correlation with aberrations, contrast sensitivity after LASIK



In eyes with larger pupils who were treated with LASIK, spherical-like aberrations affect contrast sensitivity, whereas in eyes with smaller pupils coma-like aberrations are more likely to affect visual performance.

“In eyes with larger photopic pupil diameter, increases in spherical-like aberration dominantly affect contrast sensitivity, whereas in eyes with smaller pupil size, changes in coma-like aberration exert greater influence on visual performance,” said Tetsuro Oshika, MD.

Out of the 215 eyes tested in 117 patients, 105 of them had a photopic pupil diameter of 4 mm or larger while 110 were smaller than 4 mm. In the former group, there were no significant effects in third-order coma-like aberrations and, in the latter group, there were no significant effects in fourth-order spherical-like aberrations.

Conversely, the larger pupil group showed significant correlation between changes in the area under the log contrast sensitivity function (AULCSF) and a 10% change in low-contrast visual acuity. The smaller pupil group produced significant correlation between the changes in coma-like aberrations and the changes in AULCSF and a 10% change in low-contrast visual acuity.