Eyeworld

66 | EYEWORLD | APRIL 2023 R EFRACTIVE by Liz Hillman Editorial Co-Director About the physicians Julie Schallhorn, MD Rose B. Williams Endowed Chair in Corneal Research University of California, San Francisco San Francisco, California George Waring IV, MD Waring Vision Institute Mt. Pleasant, South Carolina A LASIK referral, for example, will have more focus on the corneal aspects of the pa- tient's preoperative visual quality with high-res- olution aberrometers, such as the iDESIGN system (Johnson & Johnson Vision), Dr. Waring said, in addition to high-resolution tomography to assess corneal curvature, shape, and optical quality. The tear film and tear performance are also assessed. Dr. Waring noted the paper pub- lished by Gouvea et al. in 2019 that demonstrat- ed the role of the tear film on optical quality. 1 A patient who is deemed to be in the sec- ond stage of optical maturity with dysfunctional lens syndrome will get the same workup as above, but attention is also paid to internal light scatter and reduced contrast sensitivity, as well as the loss of accommodation. "We use Scheimpflug densitometry to assess the impact of lens density from the dysfunction- al lens on optical quality, and now the Pentacam AXL Wave [Oculus] has a built-in aberrometer that separates internal from external aberra- tions and allows us to understand the impact of lens density from the dysfunctional lens on op- tical quality," Dr. Waring said. "With ray tracing technology, we help validate the dysfunctional lens index with iTrace [Tracey Technologies], which helps separate the internal lens from the anterior cornea to understand internal optical dysfunction. This helps us determine the source and the opportunities for improvement. Use of advanced diagnostics helps us decide whether a patient may be best served with a lens-based procedure or a corneal-based procedure." Finally, there is the assessment of image quality preoperatively for the cataract patient. Dr. Waring said all of the above applies, but the cataract patient, "is more easily understood because we know they've gotten to the third stage of ocular maturity where internal optics have become so poor that it's objectively and subjectively affecting quality of life." He said the role of the anterior surface of the cornea is still important for image quality, and this is where high-resolution tomography comes into play. "If we see irregular astigmatism, for ex- ample, we need to understand its root cause, including but not limited to dry eye and EBMD. The role of preoperative 'IQ' continued on page 68 I mage quality (IQ) is an "emerging area of interest" in the field of ophthalmology, said George Waring IV, MD, and it all starts with what the patient's image quality is at the outset. "With the required specialized diag- nostics and interpretation of these diagnostics to understand the sources of optical dysfunction, that's part of the excitement of this. Now we're building a foundation in the peer-reviewed literature to support the clinical impact, the optical impact on potential sources of optical dysfunction," he said. "We now have ways to bring this into the office more readily, and it's slowly making its way into the normal conversa- tion and helping us understand the best way to provide the best outcomes." The construct of visual acuity in objective terms dates back to the mid-1800s with Snellen visual acuity, Dr. Waring explained, but lens and corneal refractive surgeons have learned there is more to vision than Snellen visual acuity. "The qualitative aspects of visual acuity are often as important as the quantitative aspects of visual acuity, and technologies are emerging where we're now able to have more quantita- tive aspects of quality of vision with the use of advanced diagnostics," he said. These include understanding the impact at the preop stage of static and dynamic factors of the tear film, of corneal shape of both the ante- rior and posterior surfaces, the optical quality of the cornea, the static and dynamic functions of the lens including various forms of opacity, the role of vitreous and vitreous opacities, and the role of the posterior capsule. "To understand how we're going to push the limits both in objective and subjective aspects of people's visual acuity, we have to be able to understand what we need to address and screen preoperatively to customize and plan. This might involve work on the tear film, the cornea, the lens and potentially the vitreous in certain patient populations," he said. In his practice, Dr. Waring said an in-depth, customized vision analysis is conducted based on what the patient is being referred in for, with a different workup for laser vision correction patients vs. middle aged to older patients who are on the dysfunctional lens spectrum and will be evaluated for a surgical lens-based solution.

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