Large pupils and LASIK

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.

The FDA placed warnings on its LASIK site concerning pupil size: LASIK Surgery Checklist and When is LASIK not for me?

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 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 treatments, the important diameter to consider is the minor axis. And blend zones don't count!

The truth about pupil size and LASIK

One argument that patients hear from the LASIK industry 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 frequently state 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 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:

Pupil Size and Spherical Aberrations

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."

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:

$4 Million Award in Pupil Size Case

$3 Million Judgment in Pupil Size Case

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:

Guide to debunking defense experts, Page 1Page 2

Importance of Accurate Pupil Measurement

Watch a video of LASIK surgeons discussing the importance of accurate pupillometry.

Watch Video

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:

www.lasermyeye.org/keratoscoop/columns/lonedog/lonedog11jun2003.html

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:

Why the optical zone is smaller than intended

Patients with large pupils report night vision impairment to the FDA

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