End Aberration Aggravation
Enable higher-order aberration patients to achieve optimum vision.
Gina M. Wesley O.D., M.S., F.A.A.O., Medina, Minn.
“That patient” is in your chair. You know, the one who drives you crazy because the refraction takes an inordinate amount of time. You’re frustrated. The patient is frustrated. Results are a shaky 20/20 OU at best. This is puzzling, as his actual prescription is nothing out of the ordinary ranges, and you have many patients within this degree of ametropia who do quite well with the refraction and their resulting eyewear corrections.
So, why does this patient struggle so much with clarity? Perhaps the answer is aberrations. This is a good educated guess, but can you be sure that’s what’s causing your patient to experience reduced clarity and crispness and say, “I can see that, but I wish I could see it more clearly”? The answer is “Yes.” Through aberration-measuring technology, you, the practitioner, can verify the patient’s degree of higher-order aberrations. Further, you can offer him custom ophthalmic lenses that can correct these aberrations, with the potential outcome a happy patient, increased practice profitability and a way to stand out from the competition.
Here, I discuss aberrations, the available technology to measure and correct them and the impact of employing this technology on one’s practice.
Aberrations: a review
Lower-order aberrations (spherical and cylindrical imperfections) comprise 80%-to-85% of a patient’s overall vision correction. The remaining 15% to 20% is made up of higher-order aberrations. These aberrations are distortions in vision acquired by a wavefront of light when it passes through an eye that has irregularities in its refractive components, such as the tear film, cornea, aqueous humor, crystalline lens and vitreous humor.1 Serious higher-order aberrations, that result in the most reduced quality of vision, can occur from anterior segment ocular scarring after surgery, trauma, including blunt or penetrating injuries to the ocular surface or globe, or any number of diseases, such as cataracts, corneal dystrophies/degenerations and even dry eye.
Think of a wavefront as a bundle of light rays. Each light ray has its own point, and one creates a wavefront map by drawing lines perpendicular to this point. A perfect wavefront from an eye that has no aberrations would be a flat plane (also referred to as “piston.”) (Incidentally, there is no such thing as an aberration-free eye.) The measurement of a patient’s actual wavefront in comparison to this “perfect” plane represents the patient’s amount of both lower- and higher-order aberrations.
Keep in mind that point spread function can also play a role in a patient’s everyday visual experience and possibly add to the complexities of higher-order aberrations. Traditionally, point spread functions describe the two-dimensional distribution of light in a telescope’s focal plane for astronomical point sources. This relates to modern optics for our patients in that we want a reduction of the point spread function to eliminate the defocus, or blur, which is associated with it. Patients who have larger-than-average pupil sizes typically suffer from vision-quality problems due to the enhancement of defocus caused by the point spread function, in addition to higher-order aberrations.
The typical patient has higher-order aberrations, and they exist largely independent to the degree of ametropia. In other words, a very myopic patient may have very little higher-order aberrations, while a patient who is mildly hyperopic may have a high degree of higher-order aberrations.
Because of the ocular variables associated with each patient and the degree and cause of their aberrations, it is difficult to correlate a specific symptom with a specific type of aberration. That said, the symptoms these patients may mention are diplopia/ghosting, overall lack of crispness, the presence of haloes, starbursts, loss of contrast in low-to-medium contrast situations and poor night vision.1
The only way to verify exactly what level of aberrations or point spread imperfections a patient has is to incorporate aberrometers in the practice testing.
Options to correct aberrations
Wavefront-based excimer laser surgery for correcting higher-order aberrations can be successful. The drawbacks: the inability to predict the pattern of changes in aberrations through time, variations in patient healing and tissue mechanics and the potential loss of best-corrected acuity with glasses.2
Wavefront Spectacle Systems*
SYSTEM: i.Profilerplus and i.Scription technology, by Zeiss
How it Works: Aberrations measured by the i.Profilerplus three-in-one device combine with the patient’s subjective refraction for the final prescription.
iProfileplus, by Zeiss
Degree of Refraction: 0.01D
Lenses: Zeiss Customized with i.Scription
Notable: Zeiss customized lenses with i.Scription are designed to provide better night vision, contrast and color perception. They use the wavefront aberrometry information from the i.Profilerplus over a range of pupil sizes together with a subjective refraction to optimize a prescription for all lighting conditions. i.Scription is available on Zeiss customized lenses, including Zeiss Individual, which is additionally customized for panto, wrap, fitting heights, frame wrap and vertex distance.
SYSTEM: Z-View Aberrometer, by Ophthonix, Inc.
How it Works: Wavefront Aberrations measured with the Z-View aberrometer wavefront sensor results in each patient’s own “iPrint” and final wavefront prescription. To achieve the final prescription, you combine the results from the Z-View Aberrometer with the traditional refraction.
The Z-View Aberrometer, by Ophthonix
Degree of Refraction: typically rounded to 0.12D (capable of 0.01D)
Lenses: iZon lenses, available in both multiple layer (highest level of aberration correction) and single layer options. Available in single vision, progressive addition lens, computer lens and bifocal. All lenses automatically come with premium AR in 1.60, 1.67 or polycarbonate material.
Notable: A simulation demonstrates to each patient what he/she is possibly experiencing due to aberrations.
Cost: Z-View’s are provided free to accounts that sign a two-year purchase agreement. The contracted practices must commit to 25 lens pairs per month (75 per quarter) to offset a quarterly fee of $1,500. These practices also receive favorable pricing, promotional incentives and up to $3,000 in co-op dollars is available each quarter.
SYSTEM: Vmax PSF Refractor
How it Works: Patients undergo a series of three-to-four short subjective tests. The Vmax Vision PSF Refractor with proprietary Point Spread Function (PSF) technology provides a high level of visual acuity and refines refraction to 0.05 D.
The Vmax PSF Refractor
Degree of Refraction: 0.05D
Lenses: Encepsion Lenses use Diamond Point Technology allowing the fabrication and polishing of lenses simultaneously using computerized software and digital surfacing equipment. Encepsion Lenses are 100% free-form backside surface-designed, which produces a wider field of view, optical clarity and allows for easy patient adaptation. Encepsion Lenses are available in single vision, occupational/office, wrap and fixed and variable progressive designs all in a wide range of materials and in numerous addons such as AR coating, Transitions and Polarized.
Notable: The Vmax PSF Refractor can refract for separate night vision correction and can demonstrate to the patient how the lenses will enhance their vision at the time of their refraction.
*As prices and specifications may change, OM recommends you contact the manufacturers directly for the latest information
Non-surgical options: Several wavefront spectacle systems refract to a higher level than the traditional 0.25D step and provide this high level of refraction with custom free-form lenses. These options offer potential solutions to your patients in minimizing or eliminating these oftentimes annoying higher-order aberrations, with little-to-no risk to the patient. (See “Wavefront Spectacle Systems,” page 40.) The drawbacks of these lenses: the potential you won’t fully correct the aberration-caused errors in vision and/or patients won’t fully appreciate the improvement in vision quality. Additionally, as the eyes continue to change physiologically through time, so do the aberrations, making prescription updates necessary to maintain the high-quality correction. Something else to keep in mind: The measuring process of some of these devices takes longer — several minutes — than the traditional refraction.
In terms of patient candidacy for these systems, anyone who suffers from any degree of higher-order aberrations can benefit from the technology. That said, the most likely patient demographics for these systems are those whose changes in refractive “structures” of the eye are beginning to affect their quality of vision.
For instance, emerging cataracts is a common culprit of increased higher-order aberrations. Also, keep in mind that although refractive surgery oftentimes aims to correct higher-order aberrations, it can result in more aberrations immediately post-surgery, or even in the years following surgery, making these patients good candidates as well.
Employing a wavefront spectacle system enables the dispensing of premium lenses, which results in higher margins for you, the prescriber. In fact, some initial studies indicate an increase of $75-to-$100 per pair of glasses sold with aberration-correcting lenses.3 In addition, I’ve found having such a device creates a “wow” factor that promotes patient loyalty and referrals.
For instance, a new patient recently presented for an eye exam, seeming dejected during the process. Her standard refraction was difficult. (I employ traditional refraction before using my wavefront spectacle system.) Her best-corrected vision was 20/30+ OU with no apparent physiologic causes. The patient said her prior eye doctors have never determined why she can’t see well. I pulled forward her aberrometry results, and she had some of the largest degrees of higher-order aberrations I had ever seen. I explained what effects these had on her capabilities for excellent vision, and she started crying. The reason: She said she was relieved to finally have an answer for her poor quality of vision. She and her entire family are now regular patients at my practice.
Another example: A husband and wife in their 50s had purchased their first pair of aberration-correcting lenses at my practice. A few months later, the wife returned for a dry eye evaluation. Without me asking, she immediately said that the aberration-correcting lenses had literally improved her and her husband’s quality of life. Specifically, she explained that before wearing the lenses, she and her spouse didn’t feel safe driving at night, and, as a result, had limited their evening excursions and trips. She added that after they got these lenses, they had resumed many of their abandoned evening activities. She exclaimed she couldn’t believe a pair of glasses could accomplish such dramatic improvements in vision.
Because wavefront-correcting spectacle systems can ease encounters with “that patient,” and elevate the level of patient experience and satisfaction, while also increasing your bottom line, they are worth your consideration. OM
1. All About Vision. Higher-Order Aberrations. www.allaboutvision.com/conditions/aberrations.htm (Accessed 5/15/12’)
2. Catania L. Wavefront Diagnosis: The Future of Vision and Eyecare. Presentation at 107th Annual American Optometric Association Congress, July 22-25, 2004; Orlando, Fla.
3. Financial analysis done by Ophthonix for offices who implementation of iZon system in 2011. Ref. Scott VeDepo, Ophthonix.
|Dr. Wesley practices at Complete Eye Care of Medina, which she opened in 2008. She was honored with Minnesota’s Young Optometrist of the Year in 2011 and enjoys the practice management aspects of practicing optometry. E-mail firstname.lastname@example.org, or send comments to email@example.com.|
Optometric Management, Volume: 47 , Issue: June 2012, page(s): 37 - 42