Patients with large pupils are not good candidates for LASIK. After LASIK, patients with large pupils may suffer permanent, debilitating visual aberrations (starbursts, halos, multiples images) and loss of contrast sensitivity (inability to see fine detail) at night. The LASIK industry uses the term "glare" to describe starbursts seen by LASIK patients as shown in the upper right image. Generally, the greater the mismatch between the laser optical zone or the effective optical zone and the maximum dark-adapted pupil diameter, the more severe the night vision disturbances. Patients who experience night vision problems after LASIK should file a MedWatch report with the FDA.
LASIK and large pupils: Case report #1
This photo was taken in the dark with the patient holding a millimeter (mm) ruler to her lower lid. Photo-editing software was used to drag the ruler over the pupil and create the inset image, which confirms that her pupils are 8 mm in the dark. She was treated with a 6 mm optical zone using a VISX S2 (no blend) laser for -4.25 diopters. The ruler in the image was used in creating the red area which represents the 6 mm optical zone. At night, light passes through 8 mm of her cornea, 44% of which is completely untreated. This patient is visually disabled at night by massive starbursts, halos, multiple images, blurry vision, and loss of contrast sensitivity, which is not correctable with glasses.
LASIK and large pupils: Case report #2
This patient's pupil diameter was measured as over 8 mm in the dark. She was treated for -6.5 -1.75 (moderate myopia with astigmatism) with a VISX S4 using a 5.5 x 6 mm optical zone plus a blend to 8 mm. This image was created with photo-editing software using a scanned image of the patient's corneal topography. The topography was resized to scale using the topography grid lines and the ruler in the photo. The topography was then cropped and pasted over the pupil. This image demonstrates corneal refractive power changes across the patient's pupil diameter, which results in night vision problems such as halos, starbursts, double vision, and loss of contrast sensitvity.
There is abundant evidence in the medical literature demonstrating the importance of pupil size in refractive surgery. Some key medical studies which document the importance of pupil size in LASIK can be found at this link: Role of pupil size in LASIK
The American Academy of Ophthalmology (AAO), American Society of Cataract and Refractive Surgery (ASCRS), Federal Trade Commission (FTC), Food and Drug Administration (FDA), and Ophthalmic Mutual Insurance Company (OMIC) have issued statements regarding pupil size in refractive surgery. Industry & Regulatory Guidance on Pupil Size
The Mayo Clinic website warns that patients with large pupils may experience debilitating symptoms such as glare, halos, star bursts and ghost images after LASIK. Mayo Clinic article
Prominent LASIK surgeon talks about importance of pupil size in LASIK screening
LASIK patient Steve Post talks about his pupil-size lawsuit (beginning at 3:53)
How large is large?
We are often asked the question, "how large is large?" Size is relative. When considering pupil size in the practice of LASIK, a pupil is considered to be large if the dim light pupil diameter exceeds the diameter of the laser optical zone. For example, a 6.0 mm pupil is large in relation to a laser optical zone of 5.0 mm, but not in relation to a 6.5 mm optical zone. In modern LASIK with an optical zone of 6.5 mm, a pupil diameter greater than 6.5 mm is considered "large". In astigmatic patients, the important diameter to consider is the minor axis of the treatment. AND BLEND ZONES DON'T COUNT!
Routinely LASIK patients are falsely told that they received a large "treatment zone". We've heard from many LASIK patients who believe they received a 7 mm or 7.5 mm (or even larger) LASIK optical zone. Most optical zones with modern LASIK are 6 mm or 6.5 mm. The full treatment diameter includes a blend zone. (Some early generation excimer lasers did not have blend zones). An 8 mm blend zone is common. But the blend zone does not receive the refractive correction. The purpose of a blend zone is to taper the laser treatment to reduce the sharp transition from the optical zone to the untreated area of the cornea. Only the optical zone is intended to receive the full correction. If the pupil dilates beyond the optical zone into the blend zone or beyond, the patient will see aberrations such as starbursts, halos, and ghost images, and contrast sensitivity will be reduced.
Why don't they just give every patient an optical zone as large as his or her pupils? The wider the optical zone, the more corneal tissue is removed. If too much tissue is removed, the patient will likely develop post-LASIK ectasia. For this reason, patients with large pupils are not good candidates for LASIK. But instead of putting patients' best interest first and turning away patients with large pupils, LASIK surgeons engage in a cover-up and deny the importance of pupil size in order to maximize the pool of potential LASIK candidates.
How do I know the diameter of my optical zone? The following link will open up an operative report from an actual LASIK patient's records. View operative report. The data circled in red is the diameter of the laser treatment. In this example, the patient had LASIK to treat myopia and astigmatism. The term "cylinder" is used to describe astigmatism. The diameter of this patient's astigmatic correction, which is in the shape of an ellipse, is 6.5 mm x 5.00 mm with a blend to 8 mm. This patient was likely told that he/she received an 8 mm "treatment zone"; however, when the patient's pupils dilate larger than 5 mm (the minor axis of the elliptical optical zone), he/she will likely see visual aberrations.
The truth about pupil size and LASIK
One argument that patients hear from the LASIK-industrial complex is that pupil size alone does not predict who will experience night vision disturbances. There are actually two factors involved – pupil size and laser optical zone. Pupil size/optical zone mismatch, termed “negative clearance”, is a result of an effective optical zone smaller than the maximum pupil diameter at night. A patient should never consent to surgery where the fully treated area is smaller than the dark-adapted pupil. LASIK surgeons try to create confusion by stating that the cause of night vision disturbances is multifactorial. Factors involved in night vision disturbances include quality and centration of the ablation, residual refractive error, and negative clearance. High myopia results in smaller effective optical zone which creates greater negative clearance. It is well known that all corneal aberrations increase with increasing pupil size. Anyone who says that pupil size is not a factor in night vision disturbances is misinformed or disingenuous. Negative clearance is a preventable cause of night vision disturbances with proper patient screening.
LASIK providers and industry supporters have a financial incentive to coverup the importance of pupil size. If you see information that minimizes or downplays the importance of pupil size, consider the source. Is the information provided by a LASIK surgeon who has a financial interest in a patient's decision to have LASIK? Is the information published on a website that promotes LASIK or refers patients to LASIK surgeons? Do not be deceived by reckless surgeons or fake patient education sites that downplay the importance of pupil size.
Why does pupil size matter?
The pupil controls the amount of light entering the eye similar to the aperture of a camera. The diameter of the cornea that receives the full intended correction by the laser should be at least as large as the patient's pupils in dim light.
The standard optical zone for LASIK surgery is 6.0 - 6.5 millimeters. Use of larger optical zones place patients at higher risk for development of the vision-threatening complication post-LASIK ectasia. Most lasers are not FDA-approved for optical zones larger than 6.5 millimeters. The ablation zone may include an additional blend zone which should not be considered when determining the size of the effective optical zone. In 2004, Netto et al found dark-adapted pupil sizes of candidates for refractive surgery range from 4.3 to 8.9 millimeters with an average of 6.5 millimeters.
In March 2011, Bradley et al published the following chart reporting dark-adapted pupil diameter as a function of age:
In April 2008, Brown et al published the following pupil size chart by age based on three research studies:
Based on these findings, a large percentage of patients should be disqualified for LASIK.
The effective optical zone (also called "functional optical zone") is the fully corrected area of the cornea, after healing, as determined by topography. The effective optical zone of the laser treatment should cover the entire diameter of the entrance pupil in dim light. If the pupil dilates larger than the effective optical zone, unfocused light rays will pass through uncorrected cornea and the resulting image will be distorted. The greater the disparity between the effective optical zone and pupil size, the more severe the visual disturbances.
The risk for night-time visual disturbances is further increased for patients with high myopia due to smaller effective optical zones associated with deeper ablations. If the ablation zone of the laser treatment is decentered, even an adequate effective optical zone for the pupil size may not cover the entire pupil diameter.
More information about the correlation between pupil size and night vision disturbances (spherical aberrations) with diagrams can be found at the following link:
What about Stiles-Crawford effect?
The light-sensitive tissue lining the back of the eye is the retina. The retina contains photoreceptors called rods and cones. Cones work only in bright light and are less numerous in the periphery of the retina. Rods are dominant in dim light and are more numerous in the periphery of the retina.
Stiles-Crawford effect, published in 1933, states that light rays entering the eye through the center of the pupil have a greater effect on vision than light rays entering through the pupil margin. This principle applies to cones (day vision), not rods (night vision).
Many LASIK surgeons misstate the Stiles-Crawford effect by falsely claiming that it minimizes night vision disturbances after LASIK.
Leo J. Maguire, MD, Mayo Clinic ophthalmologist and former FDA consultant: "The problems with pupil-related aberration are further magnified by the reality that the Stiles-Crawford effect is negated in night vision." (Source: Maguire LJ. Keratorefractive surgery, success, and the public health. Am J Ophthalmol. 1994 Mar 15;117(3):394-8.)
Editor's note: It's really absurb that the same ophthalmologists who acknowledge "night myopia" in young, unoperated eyes use the Stiles-Crawford effect to deny pupil size related night vision problems after LASIK.
Pupil Size Lawsuits
There have been several LASIK medical malpractice lawsuits based on pupil size. Unfortunately, these cases are challenging for the plantiff due to phony "expert" witnesses -- hired guns for the defense who are paid to give bogus testimony about pupil size. A true "expert" knows that pupil size is a critical factor in quality of vision after LASIK. When a pupil size case makes it to trial, and a jury sees all the evidence, these cases can be won. Here are two pupil size cases that caught the attention of the LASIK industry:
LASIK surgeons use junk science in their defense against patients with large pupils who file lawsuits. It is important to understand flaws in the methodology of medical studies published by phony expert witnesses. Read more:
Importance of Accurate Pupil Measurement
Pupils should be measured in a dark room after allowing the patient's eyes to become accustomed to the darkness. This is known as "dark-adaptation". For more about accurate pupil measurements, see:
Jack Holladay, MD: "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."
Source: Review of Ophthalmology, Vol. No: 9:03 Issue: 3/15/02, The High Cost of Inaccurate Pupillometry
Effective optical zone (EOZ), also known as functional optical zone (FOZ)
The goal of LASIK is to change the refractive power of the eye by removing corneal tissue with a laser. Due to the risk of post-LASIK ectasia, the diameter of the cornea that is fully treated by the laser (called the optical zone) is generally limited to 6 - 6.5 millimeters. If the cornea were a flat piece of plastic, a 6 millimeter LASIK treatment would be sufficient for a patient whose pupils dilate in the dark to 6 millimeters. But the cornea is not flat, and it's not made of plastic. Factors that play a role in the effective optical zone after LASIK include the healing response of the cornea and the "cosine effect" or "radial compensation function". It is important to be aware of these factors and how they relate to night vision disturbances after LASIK. Learn more:
Quote: "Another factor to consider when establishing the center for keratorefractive procedures is pupillary dilatation under mesopic or scotopic conditions. The pupil diameter might reach 6–8 mm under decreased light conditions. The optical zone in a keratorefractive procedure is defined as the area of the central cornea that bears the refractive change caused by the surgery. There is a limit to the size of the optical zone in the different keratorefractive procedures: 3.0–5.5 mm in radial keratotomy and 4.5–8.0 mm in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). As the pupil dilates beyond the edge of the optical zone, the rays of light are refracted differently in the midperipheral and the central cornea. This differential causes edge glare and haloes around objects, a phenomenon that is more pronounced at night or in cases of decentration of the optical zone. Some patients with particularly large pupils may have a mismatch between pupil size and optical zone diameter and should be warned before surgery about possible optical distortion under mesopic conditions."
Myron Yanoff, MD and Jay S. Duker, MD. Ophthalmology, Third Edition. Mosby Elsevier, 2009.
Quote: "Sophisticated pupillometry video equipment, which can determine diameters to hundredths of a millimeter, have been used in neuro-ophthalmic evaluation (36). In refractive surgery, assessment of pupil diameters is important because despite excellent visual acuity, a well-centered ablation zone, a good-looking postoperative topographical map, and the absence of significant corneal haze, widely dilating pupils at low levels of illumination are prone to halos, glare, and reduced night vision when the pupil dilates to a size larger than the ablation zone. These symptoms should be anticipated, considered, and explained to the patient before deciding to proceed with refractive surgery if the pupil size measurements in dim illumination reveal that it can dilate to a size larger than the zone of treatment. Careful measurement of scotopic pupil dilation is therefore an integral part of the preoperative evaluation of the refractive patient."
Azar, D. and Koch, D. LASIK: Fundamentals, Surgical Techniques, and Complications. (2002, Marcel Dekker)
Quote: "Pupil size measurement became the standard of care in the late 1990s, when it was observed that patients with large pupils (greater than 6 mm) had poor night vision after [keratorefractive surgery]. Typical symptoms included glare, starbursts, halos, decreased contrast sensitivity, and poor overall visual quality. Night vision problems tend to occur in patients with large pupils and small treatment zones (6.0 mm or less). The algorithms used in third-generation lasers incorporate larger optical and transition zones, enabling surgeons to perform refractive procedures on patients with larger pupils. These algorithms decrease the incidence and severity of night vision problems dramatically. Many surgeons use default ablation zones during excimer procedures. The accepted standard transition zone between ablated and unablated cornea is 0.5 to 1.0 mm larger than the pupil to minimize night vision problems. Smaller optical zones are typically used in higher myopic corrections to conserve corneal tissue. In these patients, the incidence of night vision problems increases because of the mismatch between pupil size and optical zone size. Although pupil size does not impact surgical outcome as it once did, pupil size measurement continues to be the standard of care in the preoperative evaluation. Patients with extremely large pupils (8 mm or more) should be identified. Spherical aberration may be increased in these patients."
AAO. Clinical Optics. 2008-2009.
R. Vajpayee, N. Sharma, S. Melki, L. Sullivan. Step By Step LASIK Surgery. 2003, Taylor & Francis. (page 10). Click image to enlarge.
Quote: "As the pupil dilates beyond the edge of the optical zone, the rays of light are refracted differently in the midperipheral and the central cornea. This differential causes edge glare and haloes around objects, a phenomenon that is more pronounced at night or in cases of decentration of the optical zone. Some patients with particularly large pupils may have a mismatch between pupil size and optical zone diameter and should be warned before surgery about possible optical distortion under mesopic conditions."
Source: Myron Yanoff, MD and Jay S. Duker, MD. Ophthalmology, Third Edition. Mosby Elsevier, 2009.
Patients with large pupils report night vision impairment to the FDA
A patient reports that “halo effect” post lasik surgery performed over a year ago, which makes it difficult to drive at night. Patient stated that he was reassured that this effect would go away with time, but was still experiencing it. Patient was informed by his doctor that he has large pupils, a condition which the reporter feels should have been taken into consideration by the doctor before surgery. Source
Had LASIK performed at [redacted by the FDA] in [redacted by the FDA] on [redacted by the FDA] 2010. After my procedure, my night sight was very foggy, large halos, large starbursting, and degraded vision in dim lighting. Pupils were not measured pre-surgery, and I didn't find out until after I started noticing problems. My pupils after surgery were measured at 8. 5 mm and the optical zone used was 6. 5 mm, transition 1. 25 mm and blend zone out to 9 mm. Below is a letter I wrote to the medical director there. Mr. [redacted by the FDA], I am writing you today to ask for a little help. So far I still have massive starbursting, glare, loss of contrast in dim light, and ghosting just to name a few. In my pre op visit, my pupils were never measured with the colvard pupillometer like when I had them remeasure them in [redacted by the FDA]. In fact I don't ever recall them being measured. It's hard to believe that on my charts they are said to be 6 mm but when I had them remeasured in fact they were over 8 mm which explains why all my vision problems are at night and in poor lighting when my pupil dilates. Its really not rocket science to understand that. Even my regular ophthalmologist said that my pupils are really big and another ophthalmologist I just recently saw measured my pupils at 8. 6 mm. He told me that LASIK should have never been performed on me because of the large pupils. So far I haven't gone out anywhere with my kids at night. I've been stuck inside my house because of the night time disturbances. My wife has to take them everywhere at night because it gets hard to drive. The alphagan p drops work sometimes but then tend to lose effectiveness over a few nights. I know that there is "research" that says that pupil size doesn't matter and all that, but most of it is "independent research" which pretty much means that it's worthless information. I was even told by staff that my pupils dilate past the treated area and it will go away when I get older. I'm not going to wait 10-15 years to play the let's wait and see game. This has directly effected my income, quality of life and mood. The staff have been nothing but nice to me so i'm not complaining about that. My next step i'm going to take to solve my issues is having a mini-scleral lens made to correct the night time issues. I've already been to an appointment with dr. [redacted by the FDA] in [redacted by the FDA] to be fitted for some contacts to wear at night at the cost of [redacted by the FDA]. I could have an enhancement for my left over prescription of -. 50 in my left eye but to take the risk of being overcorrected and then trading one problem for another one i've pretty much talked myself out of that. Would it help with my night issues? no. Unless they could enlarge the optical zone, but that's another surgery and no guarantee. Last time I checked I only have one set of eyes to work with and they are how I view the world. I've tried wearing a contact lens and glasses but they don't help with the night issues, so another surgery wouldn't help. I would like a little help on paying for these lenses that way I can get back to a normal life and enjoy night time activities, but I doubt that will happen. I can only wish. My other question I have are: if pupil size doesn't matter, why are they administering a drug that constricts pupils after refractive surgery? just in my opinion, you cannot acknowledge the reality of "night myopia", which affects unoperated eyes with large pupils, and at the same time, deny that pupil size is unimportant in LASIK. Night myopia is real, and large pupil-related night vision problems after LASIK is real. Thanks for you time. Thanks, [redacted by the FDA]. Source
I had LASIK surgery in [redacted by FDA] 2006 and I have been struggling with complications since. Before my surgery I was assured I had < 1% chance of having GASH or any other long term complications. I noted this on my consent form. Prior to the surgery I told the surgeon I have a very low tolerance for a bad outcome and GASH. He repeatedly told me "pupil size is not a good predictor of poor post LASIK night vision. " he assured me that as a "compatriot" he would take good care of me and that I "would do fine. " Immediately following surgery, I developed dry eye which is worsening. I developed all the GASH symptoms even though I was told I had < 1% chance of having any long term complications. The possibility of dry eye was never discussed with me. The only complications we discussed were GASH because I initiated. After complaining about dry eye my surgeon told me I had dry eye before surgery. I thought this was a contraindication for LASIK. Other contraindications for LASIK: pre-existing dry eye, occupation -computer programmer-, large pupils, high correction, astigmatism, medications, long term contact lens use and possibly cataracts. I have been seeing the surgeon the entire time for follow ups, GASH, dryness and cataracts with no resolution in sight. This has severely impacted my life to the point where my 3 yr relationship with my fiance ended. I am finding it very difficult to concentrate/work and I have become depressed as nothing helps and the Drs are stumped. Source
Editor's note: GASH stands for glare (or ghosting), arcing (or astigmatism), starbursts, and halos. Emphasis added.
I had LASIK twice now. The first time on [redacted] 2010. As a result of LASIK, I had the following complications: overcorrection which caused me constant strain and pain -severe loss of near sight due to overcorrection -extreme starbursts and halos at night -loss of vision in dim settings which also caused my eyes to strain -daily pain and discomfort and pressure in brow area -constant blood shot eyes. I underwent the enhancement on [redacted] 2010. While it seem to have helped with some issues, I still have: daily strain -severe starbursts and halos at night -loss of vision in dim settings. This still causes my eyes to strain and I feel daily pressure in my brow area. I also feel pain in my left eye. It is difficult to drive at dusk and night. My pupils are very large and I was never informed about pupil size. Nor were my eyes ever dilated. I know this is a problem as most of my issues are at night and in dim lighting. LASIK is not safe. Source
Went in for LASIK consultation and was cleared good to go. After having LASIK done, i noticed my vision was poor in dim lighting and had extreme starbursting around lighting. Went for my 3 month post op and found out my pupil was 8mm not the 6mm that they had on my chart after consultation. Still after 3 months, nothing has changed with my nighttime vision.
I was treated on a Visx laser with a 6mm optical zone. My pupils are 8mm. I was not warned that I was a bad candidate. Now I am visually disabled in dim light. At night, I see massive starbursts, halos, and multiple images. Nothing is crisp and clear in dim light (loss of contrast sensitivity). I can't drive at night or participate in any activity in dim light. I had also become contact lens intolerant before Lasik which I now know is a sign of dry eyes. My eyes burn constantly and I have recurrent corneal erosions. To say that Lasik has negatively affected my quality of life doesn't even begin to cover it. No one, expect other patients who have personally experienced this, can understand what life is like with visual impairment that is not correctable with glasses and non-stop burning dry eyes. I can't tolerate air conditioning, ceiling fans, wind or open a hot oven door. Now my life is all about my eyes and just getting by. The FDA should have restricted Lasik devices based on pupil size, and placed stronger warnings in the labeling about dry eyes. The FDA commissioner said that the FDA exists to serve the people, not to serve industries, but it appears to do just the opposite. Source
"...According to the dr, the healing process also went normal and i was declared to have an excellent outcome due to my low refractive error. However, in spite of this, the results of this surgery were actually disastrous. Although my post-surgical refractive error is quite low, the surgery induced a significant level of higher order aberrations, including a highly abnormal level of spherical aberration and coma due to a correction zone that is much smaller than my scotopic pupil size. I see fine in direct sunlight and natural lighting, but have difficulty seeing clearly under normal levels of indoor or artificial lighting. I can not see clearly in many indoor environments during the day, particularly on overcast days, and i have consistently poor quality of vision indoors in the evenings due to significant loss of contrast sensitivity. I frequently experience halos around indoor lighting. It is also very difficult to drive at night due to significant starbursting on all light sources, which results in a significant loss of depth perception. I can not enjoy many leisure activities such as watching movies. Watching television with lights on can be quite challenging due to poor quality of the image i see, and going out at night is difficult... I have spent a significant part of the last year trying to cope with the emotional turmoil and anxiety that have resulted from the loss of visual quality from an elective surgery that was supposed to improve my quality of life. I did not need this surgery, and based on my results, it clearly is not as safe and reliable as it was represented to be." Source
I had lasik eye surgery from dr. In 2006. It was the biggest mistake of my life. Here is a list of my concerns: - my last checkup occurred last year, and i still remained at 20/15 on my right eye and 20/20 on my left eye. This is very misleading as things over 20 feet are blurry. They're especially blurry in medium to low lighting. I had no idea that my eyesight was definitely going to be worse afterwards. I thought since 20/20 was very likely, my vision could remain perfect at far from it. My vision also fluctuates depending on how much rest i get. I believe it's because the more i rested i am, the bigger my pupils are. Bigger pupils lead to seeing more through untreated parts. -they only treated my eyes partially and did not warn me of this. The treatment zone simply did not cover my entire eye. I have big pupils. The cut did not go outside of my pupils but within it. The outer area of my pupils remains untreated. I was not warned of this. I just cannot understand how they can get away with something like this as it has severely affected my vision for the worse. -i was not warned that i was going to get a permanent scar on my eyes. I believe it plays a big part of my blurred vision. -i was not warned that my night vision was definitelly going to get worse. I was very shocked the next day to see that my night vision definitely got worse. This should not be a surprise. I was simply warned about the possibility of getting starbursts and halos. I have a severe case of both. Based on the size of my pupils, they should have told me that the likelihood was high. -dry eyes are a constant problem for me. I've experienced loss of sleep and lack of sleep, due to extreme dryness that wakes me up or severe crust formations that did not exist before surgery. I was not aware that there are tests to determine how dry your eyes are. This should be a mandatory test. I have to put several eye drops a day- probably for the rest of my life. This is very costly, embarrassing, and bothersome. - i had red eye for about one month on my left eye. I had no idea that this could happen. It was very embarrassing to have it when i wanted to prove to co-workers and friends that lasik was safe and recommendable, but was i simply showing them proof that i made a mistake. The reputation of my judgement has probably been significantly damaged. -it takes a long time focusing on different distances. If i'm reading something and look up to something, it takes seconds to focus on it. This was always instant before. I was not warned of this. -the stats provided by the media and the ads are absurd. My surgeon asked me if i was glad to have done the surgery the day after. I said i was. He may have put that on record. No one's asked my how i'm doing now. Based on my own personal survey of people having done the surgery, most have regrets. Source