wavefront
Wavefront: The New Standard for Vision and General Eye Care?
Wavefront is becoming part of the standard of care for refractive surgery. Is it possible to mix this technology into the standard of routine primary eye care as well?
BY LOUIS J. CATANIA, O.D., F.A.A.O. AND JENNIFER HENSON, O.D., Jacksonville, Fla.

The rapid advancement of wavefront technology has been a dramatic byproduct of the refractive surgery evolution over the past four to five years. The application of adaptive optics to measure human vision now allows us to assess aberrations in the human vision system down to thousandths of a diopter.

This progress is already being applied to laser vision correction in the form of wavefront-guided custom ablation. The technology will rapidly become the minimum standard of care for corneal refractive surgery. But of even more significance to optometry is wavefront's potential applications in vision care and general, primary eye care.

Just think about it

So just how far can wavefront analysis go as a diagnostic tool? How fast will eyecare practitioners appreciate its diagnostic applications? And indeed, will wavefront aberrometry become the new standard for diagnostic and corrective vision care?

Currently, our refractive care for patients measures only lower- order (first and second) aberrations (prism, sphere ["defocus"] and cylinder), which represent about 80% of the human visual system. At this level, a 20/20 Snellen acuity has been an acceptable goal for many years.

Now, thanks to brilliant researchers such as David Williams, Ray Applegate, et al., we can use adaptive optics in wavefront aberrometry to measure the higher-order aberrations (HOAs) of the Zernike Pyramid. With this capability we can measure the remaining 20% of the human visual system and seek the full 100% potential of a patient's visual system. That potential acuity can reach as high as 20/8 with maximum retinal and cortical function.

And then we have the many diagnostic uses of wavefront analysis beyond refraction.

Using wavefront to diagnose

Every week we seem to find yet another diagnostic use for wavefront. We can compare distance to near aberrometry to measure changes in HOAs, particularly astigmatism in a dynamic accommodative state. The simple addition of plus for near in presbyopia may eventually be further refined by static to dynamic vision comparisons to effect a more precise near correction.

The combination of topography and wavefront analysis gives us the ability to measure residual crystalline lens aberrations through the subtraction of corneal aberrations obtained from topography deducted from the eye's total aberrations obtained from wavefront. With this information, you can determine the best treatment for your patient, whether it be a corneal-based refractive procedure, a lens-based refractive procedure ("refractive lens exchange" for clear or cataractous lenses) or a spectacle or contact lens correction. This capability can also provide a precise assessment of aging effects in the lens long before cataract formation.

Wavefront technology lets us accurately assess clinical variables with pseudophakic and even the evolving pseudoaccommodative intraocular lenses (IOLs). Your early diagnosis of problems such as lens tilt, decentration and posterior capsule opacification will help solve the patient's visual symptoms and provide earlier corrective interventions.

Surveying the options

Beyond its obvious pre- and post-procedure diagnostic values in refractive surgery, wavefront analysis lets us diagnose other surgically related problems as well as ocular surface abnormalities in general, and even contact lens considerations. We can use wavefront analysis to postoperatively monitor corneal surgeries, intraocular surgeries (including cataract extractions, glaucoma procedures, retinal surgeries, etc.) and oculoplastic procedures such as tarsorrhaphy and blepharoplasty.

Additionally, wavefront analysis can also aid your definitive diagnoses of many ocular surface abnormalities when they're having distinct qualitative and quantitative effects on vision. Such abnormalities include anterior-basement membrane disorders, corneal dystrophies and degenerations, and tear dysfunctions such as dry eye syndrome.

Adding higher-order correcting optics to diagnostic devices will soon create a new generation of ophthalmic instrumentation. Clinicians will use these instruments in at least common day-to-day exam procedures such as biomicroscopy and ophthalmology. In the near future, we'll be examining external ocular tissues and structures with slit lamp biomicroscopes equipped with adaptive optics. Internally, we'll use adaptive optics ophthalmoscopes as well. Such viewing capabilities will provide potential observation of micron-level structures and abnormalities. This degree of clinical accuracy will enhance diagnostic precision relative to the degree, location, intensity and progress of pathological and physiological tissue change.

Corrective potential as well

Regarding our use of wavefront aberrometry as vision care specialists, our ultimate goal will be not only to measure and diagnose a patient's vision but also to correct it to its fullest potential. Such corrective therapies, beyond surgery and perhaps superior to refractive surgeries, are just around the corner.

Numerous forms of higher-order correcting spectacles and contact lenses, which will be discussed in upcoming papers, are already in development and some are even in advanced clinical testing. We'll use our wavefront measurements to prescribe these forms of correction. Such exciting new technologies will become commercially available over the coming months and years. And as with any evolving technology, marketing claims and promises will grow rampant and we'll have to consider them in assessing and determining what's best for our patients.

Thus, we must begin now to understand, master and incorporate wavefront technology and aberrometry into our routine diagnostic assessments of patients' vision and for any ocular abnormalities that might affect vision. This diagnostic goal in vision care is as important to us as eventual wavefront-generated vision correction itself.

Practice proud

We must maintain the highest level of diagnostic vision care to retain our role as patient advocate, counselor and the vision care specialist of the health care system. To appreciate the need and importance for maintaining the highest level of diagnosis in primary care, we have to look no farther than the past 20 years of our profession's history. The analogy we can look at is the evolution of threshold, static perimetry and its replacement during the 1980s of the long held standard, yet inferior dynamic perimetry.

We should feel proud of our rapid adoption of threshold perimetry instrumentation based "solely" on its marked improvement over its predecessor technology, dynamic perimetry. (I say solely because during our adoption of threshold perimetry we were still fighting for the right to treat and manage glaucoma.) In fact, our goal in incorporating a better technology into our care, notwithstanding its substantial cost to our practices, was strictly to improve our diagnostic abilities and to enhance the level of care we were providing our patients.

Does the provision of vision care by optometry deserve anything less than the adoption of the highest level of diagnostic vision technology? Not if we're to remain the vision care specialists of the healthcare system and the primary eyecare experts our patients and other healthcare professionals view us as.

Prepare for future care

Indeed, corrective therapies prescribed with wavefront aberrometry may be just around the corner and certainly will eventually become the standard for all vision correction. But for optometry, we must define our standard for diagnostic vision and primary eye care by the highest levels of technology available today. That level includes wavefront aberrometry.

Will wavefront aberrometry be the standard for vision care in the future? Absolutely! But we should be thinking about, if not adopting it, now.

Dr. Catania is an internationally acclaimed clinical educator, author and recognized expert in anterior segment care, refractive surgery and new eyecare technologies.

Dr. Henson is a graduate of the Southern College of Optometry and is an associate at Nicolitz Eye Consultants.