Despite ongoing fine-tuning of the formulas for the optical power of IOLs, errors are still possible, often related to keratometry, prediction of effective lens position, and optical biometry.

Reviewed by Jack T. Holladay, MD, MSEE, FACS

Even after decades of making periodic adjustments and updates to formulas for the 

to improve accuracy, choosing the correct power can still be challenging, said Jack T. Holladay, MD, MSEE, FACS.

Formulas for the calculation of IOL power have been around since S.N. Fedorov’s original publication of “Estimation of Optical Power of the Intraocular Lens” in 1967. 

 is prone to three pitfalls following corneal refractive surgery or keratoconus: inaccuracies related to keratometry, 

After keratometry or corneal refractive surgery, the only relevant part of the cornea is the 4.5-mm lenticle, explained Dr. Holladay, clinical professor of ophthalmology, Baylor College of Medicine, Houston. Keratometry measures the front-surface ring of the lenticle-ranging from 2 mm to 3.2 mm depending on the keratometer-using a back radius of 4, 6, or 28 points and presuming a back radius of 82.2% of the front radius.

However, for irregular corneas (e.g., post-refractive keratoconus, post-penetrating keratoplasty, and scars), keratometry is inaccurate due to sample size and should be replaced with zonal topography or tomography.

Topography measures the entire front surface of the lenticle, with about 14,000 points, whereas tomography measures the front/back surfaces, using about 40,000 points, Dr. Holladay said.

“What we want is the power of that lenticle, and since the sample size is much better, in both of these conditions (keratoconus and refractive surgery) you should always get topography or tomography,” Dr. Holladay said.

After keratoconus, the cornea becomes a simultaneous bifocal. A bifocal “cap” is formed with 2 to 5 D more power than the paracentral power within the pupil. “What you want is the paracentral power that’s in the pupil,” he said.

“The cap gives you reading power, just like a bifocal intraocular lens. Patients don’t look through the average, and that’s what the keratometer is going to give you. You have to move that mouse around in the paracentral area to get an average value and avoid the cone, because that’s for reading; it’s not for distance vision.”

However, in post-refractive surgery, the cornea is not a bifocal. It is flattest in the center of the cornea following myopic surgery and steepest in the center after hyperopic surgery. If it was centered on the pupil it will be decentered relative to the visual axis. The pupil size is critical, and the key is to find the power within the zone. If the pupil is smaller than average, the power has to be customized.

Another pitfall is that the prediction of effective lens position is inaccurate if using keratometry; neither the cap power nor the flattened cornea after myopic refractive surgery will size the eye correctly, Dr. Holladay said.

Rather, the “double K method” is more reliable. Use keratometry before refractive surgery or the paracentral power in keratoconus to estimate the size of the anterior segment, then use the refractive vergence power measured with zonal power.

A third source of errors is optical biometry. It can yield imprecise results in long eyes (>25 mm), which are common in refractive surgery and keratoconus, thus the axial length must be shortened with all formulas. The error resulted more than a decade ago from calibrations made for OCT that included eyes up to 26 mm long; calibrations were then extrapolated from 26 to 36 mm.

“If you extrapolate you overestimate the length of the eye, and the eyes are progressively shorter,” he said. “In fact, for a 36-mm eye, it’s really 34.”

A linear regression model to compensate for long eyes was published in 2011 by Wang and Koch, and further axial length adjustment formulas were published in the

 Journal of Cataract and Refractive Surgery

This article was adapted from Dr. Holladay’s presentation during Refractive Surgery Subspecialty Day at the 2018 meeting of the American Academy of Ophthalmology. Dr. Holladay did not report any relevant disclosures.

Articles

Pearls for overcoming pitfalls related to keratometry, prediction of effective lens position, optical biometry

Valuing power of the lenticle

 that uses corneal allogenic intrastromal ring segments (CAIRS) was simple, safe, and effective in a small pilot study, said Soosan Jacob, MS, FRCS, DNB, director and chief, Dr. Agarwal’s Refractive and Cornea Foundation, and senior consultant, Cataract and Glaucoma Services, Dr. Agarwal’s Group of Eye Hospitals, Chennai, India.

Dr. Jacob developed the technique because the use of synthetic ring segments often has led to complications such as extrusion, migration, melt, corneal necrosis, and even infections necessitating corneal transplantation, she said. She wanted to find a way to decrease the incidence of these complications.

In the study, which was published in the 

 CAIRS trephined from donor cornea were then implanted into femtosecond laser-dissected channels in the cornea in 24 eyes (20 patients) with keratoconus. The CAIRS were used in the 6.5-mm optic zone. Dr. Jacob initially used ring segments (Intacs, Addition Technology) not as an implant but as an instrument to help get the CAIRS in, but later she found that the CAIRS pushed right in.

 or contact lens-assisted CXL (another approach developed by Dr. Jacob, for crosslinking thin corneas) was performed.

The choice was made depending on each patient’s minimum corneal thickness. With contact lens-assisted CXL, a riboflavin-soaked bandage contact lens is placed on the eye to help increase the corneal thickness. The contact lens used is ultraviolet barrier-free.

The results in patients having accelerated 

 or contact lens-assisted CXL were similar in the study, Dr. Jacob said. Significant improvement occurred both for uncorrected distance visual acuity (mean, 2.79 ± 2.65 lines; range: 0 to 8 lines) and corrected visual acuity (mean, 1.29 ± 1.33 lines; range: 0 to 5 lines).

There also were significant improvements in spherical equivalent, simulated maximum keratometry, steepest keratometry, topographic astigmatism, anterior and posterior best fit spheres, mean power in the 3- and 5-mm zones, as well as other areas. No eye had any progression during the follow-up, which ranged from 6 to 18 months. All segments remained in position, and no segment-induced complications occurred.

“There is basically no disadvantage [with CAIRS],” Dr. Jacob said. “It’s biocompatible, easily available, effective, stable, safe, reversible, and adjustable.”

She looks forward to the creation of nomograms for CAIRS, femtosecond-cut CAIRS, eye bank-prepared segments, modified segments, and increased storage abilities.

This article was adapted from Dr. Jacob’s presentation at Refractive Surgery Subspecialty Day at the 2018 meeting of the American Academy of Ophthalmology. Dr. Jacob has a patent pending for shaped corneal segments and the devices and processes used to manufacture them.

1. Jacob S, et al. Corneal Allogenic Intrastromal Ring Segments (CAIRS) combined with corneal crosslinking for keratoconus. 

Novel technique could help surgeons treating keratoconus, ectasia

CAIRS may eliminate complications from synthetic ring segments

Follow-up that includes data from 264 eyes seen at 7 years after surgery show that small-incision lenticule extraction (SMILE, Carl Zeiss Meditec) is safe, effective, and provides stable correction for eyes with up to –14.0 D of myopia and up to –6.0 D of astigmatism.

Results from long-term follow-up show that small-incision lenticule extraction (SMILE, Carl Zeiss Meditec) 

provides safe, effective, and stable correction

 of low to high myopia with astigmatism, said Osama Ibrahim, MD, PhD.

“We have been doing SMILE for more than 10 years, and there are still some challenges that need to be addressed, but SMILE is here to stay,” said Dr. Ibrahim, professor of ophthalmology, Alexandria University, Alexandria, Egypt. His comments were based on data from 5,263 eyes, of which 264 were seen after 7 years.

Because of access to research software, the amounts of sphere and cylinder corrections exceeded those available commercially. Preoperatively, manifest refraction spherical equivalent (MRSE) for the entire cohort averaged –5.92 D ± 2.13 D and ranged from –1.25 to –14.00 D; MR cylinder averaged –1.26 D ± 1.04 D and ranged up to –6 D. and we get very good results.

At 1 week after surgery, mean MRSE was –0.15 D ±0.51 D (range, +2.00 to –3.50 D) and mean MR cylinder was –0.12 ±0.38 D (range, 0.00 to –2.75 D).

“Some cases were initially undercorrected intentionally, and we had some overcorrections that occurred because there was no software adjustment at the time of the procedure,” Dr. Ibrahim said.

Data from follow-up at 1 year was available for 3,876 eyes, 587 eyes were seen at 2 years, and 264 eyes were seen at 7 years. Results from manifest refraction were generally stable over time except for a slight increase MRSE in later years.

“Many of the patients were treated when they were just 19 or 20 years old, and the late change in MRSE is explained by an increase in axial length over time,” Dr. Ibrahim said. “The MR cylinder, however, was unchanged.”

Refractive predictability was excellent for the overall cohort and across all subgroups when eyes were divided by degree of myopia into mild-moderate (MRSE <–6.0 D), high (MRSE ≥–6.0 to <–10.0 D) and very high (MRSE ≥–10.0 D). At different follow-up intervals, achieved MRSE was ±0.25 D of target in about 80% of eyes.

“SMILE is not a procedure for treating a specific level of myopia,” Dr. Ibrahim said. “Rather, it can treat a broad range.”

Analyses of changes from baseline BSCVA provided assurance about the safety of the procedure. The percentage of eyes losing 2 or more lines from preoperative BSCVA was ≤1% at any follow-up; BSCVA was unchanged or improved in 89% to 95% of eyes across the different follow-up intervals, and the percentage of eyes that gained 1 or more lines of BSCVA increased over time.

“Safety was our main concern when we started with SMILE because we were still refining the techniques and technology,” Dr. Ibrahim said. “Luckily, we found in our follow-up that some early losses of BSCVA were transient.”

He pointed out that gains in BSCVA after SMILE may be explained not just by loss of minification but by the flattening response that occurs after SMILE. Topographic maps show a 6.0- or 6.5-mm diameter area of flattening following removal of a 6.0-mm lenticule whereas after LASIK, the area of flattening is smaller in diameter than the ablation zone.

“The cornea responds differently to tissue removal than it does to ablation,” Dr. Ibrahim said. “The peripheral cornea relaxes after SMILE, and we believe that is why we can use SMILE to correct higher amounts of myopia and obtain better quality of vision compared with LASIK.”

 has been done with LASIK and PRK, but ongoing research is investigating enhancement by performing SMILE in the cap or in the residual bed. So far, the latter techniques have been associated with encouraging results.

Other techniques under development include customization (wavefront guidance), cyclotorsion adjustment, and treatment of hyperopia. In addition, 

 to prove that SMILE has an advantage over LASIK when it comes to preserving corneal biomechanical integrity and to corroborate its long-term stability.

“Some people still need to be convinced that we are not getting regression after SMILE,” Dr. Ibrahim said. “Looking at eyes in our series that had residual error later during the follow-up we found that they had the same error from the beginning.”

This article was adapted from Dr. Ibrahim’s presentation during Refractive Surgery Subspecialty Day at the 2018 meeting of the American Academy of Ophthalmology. He is a consultant to Carl Zeiss Meditec.

Follow-up at 7 years shows procedure safe, effective, provides stable correction

Long-term data establish SMILE role in myopic treatment armamentarium

Hydrophilicity refractive index shaping has potential to alter the refractive qualities of the cornea without changing its shape.

Reviewed by George O. Waring IV, MD, FACS

Developing femtosecond laser technology can change the refractive qualities of an IOL after it has been implanted.

The same technology, hydrophilicity refractive index shaping (RIS), has the potential to alter the refractive qualities of the cornea without changing its physical shape.

“This is a new paradigm and is potentially huge in refractive surgery,” said George O. Waring IV, MD, FACS, founder of Waring Vision Institute, Mount Pleasant, SC, and adjunct assistant professor of bioengineering, Clemson University. “It could change the ways we approach refractive surgery, either at the IOL plane or at the corneal plane.”

Dr. Waring described the current state of refractive index shaping as applied to acrylic IOLs. He is a consultant to Perfect Lens LLC, one of several companies developing RIS platforms and applications.

“What is being done is utilizing a femtosecond laser to selectively change the refractive index of the target material, which changes the optical properties of how a refractive material performs,” Dr. Waring said.

“You can essentially create a shape with a material plane, create a three-dimensional structure within an existing physical space without changing or disrupting the surface of the material or the tissue where the effect is aimed,” he said. “You can create a lens within a lens without disrupting the surface of the material, in this case an IOL.”

The femtosecond laser very precisely affects the hydrophilicity of the target material to alter its refractive characteristics in a limited area, Dr. Waring continued. The technology also exploits Fresnel optics to produce an effect called phase wrapping.

“Phase wrapping allows you to effect a large optical change efficiently in a small physical space,” he said. “This allows for larger treatments within an IOL. This could potentially offer numerous benefits in a clinical setting, in the laser suite, because the entire process is minimally invasive.”

Benchtop testing promises a wide variety of clinical applications. The technology allows the ophthalmologist to take control of most optical properties and qualities 

that affect both additive and subtractive measures

, including spherical aberration, asphericity, toricity and multifocality.

The femtosecond laser that alters the optical qualities of the IOL is a proprietary application using a dedicated device, Dr. Waring said, but the laser form factor and liquid optic interface are intuitive and familiar to anyone who is used to docking or utilizing the femtosecond laser instruments now in clinical use.

The entire process is image guided and has been tested across multiple brands of acrylic IOPs with a high degree of precision across brands.

While the technology still needs further testing and clinical trials, benchtop test results are dramatic.

 can be reduced, or increased, up to six diopters. And once changed, the power can be changed and adjusted at least multiple times without significantly affecting the modulation transfer function of the lens.

Spherical aberration can be adjusted to customize an off the shelf IOL to the patient’s own optics. Starting with a non-toric monofocal lens, RIS makes it possible to create a spherical and/or astigmatic pattern a treatment 

For patients implanted with a monofocal lens who later wish they had opted for a multifocal implant, RIS may offer a solution. Benchtop tests show a monofocal lens can be converted into a multifocal lens, and vice versa. The most important optical change when converting from monofocal to multifocal functionality is a reduction in modulation transfer function because light is now being redistributed across multiple foci.

“It appears that we may also be able to reverse multifocality for people who have struggled with this technology,” Dr. Waring said. “And when going from multi- to monofocal, we see increased modulation transfer function because we are reassigning light to the same focal point.”

Changes in modulation transfer function also make it possible to adjust the amount of light allocated to different focal points within a multifocal lens. That opens the door to customized light levels for near, intermediate, and far vision, depending on patient preference and visual need, he noted. It could also be possible to change the light allocation to the different focal points sequentially to allow for neuroadaptation over several weeks or months to improve the patient’s perception of visual quality.

“The most common opportunities for the refractive types of enhancements that are currently done, small enhancements with laser vision correction, piggyback IOLs or IOL exchange, these can all be done in minimally invasive fashion using laser light in the clinic with this technology,” Dr. Waring said.

“Sequential treatments appear to be possible, so power and other qualities could be changed over one’s lifetime or until the patient is happy with the result,” he added. “And because acrylics can be optimized for this technology, it is entirely conceivable that we could be customizing lenses even before they go into patients’ eyes and then tweaking each lens as needed after implantation.”


	P: 843/592-3955
	E: GeorgeWaring@me.com
	

This article was adapted from Dr. Waring’s presentation during Refractive Surgery Day at the 2018 meeting of the American Academy of Ophthalmology. He did not indicate financial interest in the subject matter.

Laser technology has potential to modify IOL refractive index without change to lens shape

Hydrophilicity RIS setting stage as new paradigm for refractive surgery

Refractive surgeons must understand the arsenal of diagnostic technology available to them as well as how and when to use it for their patients, according to Renato AmbrÃ³sio Jr., MD, PhD.

Reviewed by Renato AmbrÃ³sio Jr., MD, PhD

Careful preoperative evaluation can help ophthalmologists boost patient satisfaction by 

 and avoiding many of the potential complications of refractive surgery. Preoperative assessment must include understanding and proper counseling of patients as well as provide a comprehensive evaluation for planning the procedure and screening for potential complications, said Renato AmbrÃ³sio Jr., MD, PhD.

“Listen to patients’ needs, motivations, and expectations to understand why they have come to refractive surgery, and what they expect from it,” said Dr. AmbrÃ³sio, adjunct professor of ophthalmology, Federal University of the State of Rio de Janeiro (UNIRIO), and director of refractive surgery, VisareRIO, Rio de Janeiro, Brazil.

“In addition, imaging has revolutionized our ability to screen, plan, and evaluate the results of refractive procedures, gaining fundamental relevance in the preoperative workup,” he said.

, starting from classic slit lamp biomicroscopy with digital documentation, central corneal thickness, and Placido’s disk-based topography.

Scheimpflug tomography provides a three-dimensional picture of the cornea, an imaging technique distinct from front-surface topography as well as from segmental tomography by OCT. Very high-frequency ultrasound provides epithelial thickness mapping. Proper nomenclature is essential to distinguish technologies.

In addition, ocular wavefront, ocular scattering evaluation, novel ocular surface imaging with meibomiography, IOP, corneal biomechanical assessment, confocal, and specular microscopy are available. Molecular biology and genetics are moving toward practical applications for patient evaluation.

Every refractive surgeon must understand this arsenal as well as how and when to use it for patients, he noted.

“We have to understand if the candidate presents for elective refractive surgery, or if the case requires a therapeutic appoach

,” Dr. AmbrÃ³sio said. “If the treatment is done on the cornea, should it be a phakic IOL or crystalline lens surgery? If the patient is a candidate for corneal laser-vision correction, is it best to do LASIK, SMILE, or PRK?”

It is important to recognize the complications to be avoided and how to identify the cases at higher risk, Dr. AmbrÃ³sio added.

“We have to know our ourselves and our tests and the conditions we have to identify,” he said. Ectasia, or keratectasia, 

the innate structure and biomechanical properties of the cornea,

the impact from the surgery on the cornea, and

postoperative trauma, most often due to eye rubbing.

Key to prevention is understanding the pathophysiology of ectasia to assess the individual risk of biomechanical decompensation, he said.

“The literature recognizes forme fruste keratoconus as the major risk factor for ectasia, but the reality is that any cornea can develop ectasia,” Dr. AmbrÃ³sio said. “All it takes is the unfortunate combination of corneal structure, surgical impact, and mechanical trauma, such as eye rubbing.”

Eye rubbing alone may trigger ectasia progression, and patients should be educated about it. While there is some divergence in the literature on what is fruste, or subclinical keratoconus, we have evolved from the ability to diagnose very mild disease with normal slit lamp and good visual acuity toward the characterization of the susceptibility for ectasia development.

Dr. AmbrÃ³sio’s group recently published

 a novel tomographic assessment of ectasia risk using artificial intelligence based on Pentacam data. The resulting Pentacam Random Forest Index (PRFI) yielded ectasia diagnosis with 94.3% sensitivity and 98.8% specificity.

Integrating Scheimpflug tomography and biomechanics yielded a Tomographic and Biomechanical Index (TBI) that significantly augments sensitivity for ectasia diagnosis.

The original study found the TBI has 90.4% sensitivity with 96% specificity,

 compared with 79% sensitivity of the BAD-D, he noted. Dr. AmbrÃ³sio added that further improvements are possible along with the inclusion of extra data such as epithelial thickness from segmental or layered tomography to further enhance accuracy.

Artificial intelligence could also integrate corneal data with the impact from the procedure.

“The Enhanced Ectasia Susceptibility Score (EESS) conjugates the data from the cornea- such as tomography and biomechanics along with age and the impact from the refractive surgery-to estimate a risk,” Dr. AmbrÃ³sio said. “The risk is never zero, but should be acceptable and we have to understand it.”

Some patients may better qualify for a procedure according to the corneal impact, he noted.

“SMILE has a corneal-weakening factor which is between LASIK and PRK,” he said. “That is not to say that SMILE or any other procedure is better than the others, but we can find the best procedure for each case. This is truly customization to optimize surgical outcomes.”

Dry eye is another contribution to patient dissatisfaction. Patients asking for refractive surgery correction typically opt for surgery because they are, or have become, intolerant of contact lenses, which is commonly associated with some degree of tear dysfunction.

Ocular surface evaluation has evolved including non-invasive break-up time, meibomian gland imaging, and tear osmolarity. Patient education and ocular surface optimization should enhance chance of success for these cases.

The goal is to optimize the chance of success, which, intimately, is related to patient satisfaction and safety, he said. Refractive surgeons must be conscious of the opportunities and rationale for a proper preoperative assessment in order to minimize complications and maximize outcomes.

This article was adapted from Dr. AmbrÃ³sio’s presentation during Refractive Surgery Subspecialty Day at the 2018 meeting of the American Academy of Ophthalmology. He is a consultant to Alcon Laboratories, Carl Zeiss Meditec, and Oculus.

1. AmbrÃ³sio Jr., Renato. Therapeutic refractive surgery: why we should differentiate? 

. 2013;72:85-86. https://dx.doi. org/10.1590/S0034-72802013000200002.

2. Lopes BT, Ramos IC, SalomÃ£o MQ, Guerra FP, Schallhorn SC, Schallhorn JM, Vinciguerra R, Vinciguerra P, Price FW Jr, Price MO, Reinstein DZ, Archer TJ, Belin MW, Machado AP, AmbrÃ³sio R Jr. Enhanced tomographic assessment to detect corneal ectasia based on artificial intelligence.

. 2018;195:223-232. doi: 10.1016/j. ajo.2018.08.005. Epub 2018 Aug 9. PubMed PMID: 30098348.

3. AmbrÃ³sio R Jr, Lopes BT, Faria-Correia F, SalomÃ£o MQ, BuÌhren J, Roberts CJ, Elsheikh A, Vinciguerra R, Vinciguerra P. Integration of Scheimpflug-based corneal tomography and biomechanical assessments for enhancing ectasia detection.

. 2017;33:434-443. doi: 10.3928/1081597X- 20170426-02. PubMed PMID: 28681902.

4. SalomÃ£o MQ, Hofling-Lima AL, Lopes BT, Canedo ALC, Dawson DG, Carneiro-Freitas R, AmbrÃ³sio R Jr. Role of the corneal epithelium measurements in keratorefractive surgery. 

. 2017;28:326-336. doi: 10.1097/ ICU.0000000000000379. 

5. AmbrÃ³sio R Jr, Tervo T, Wilson SE. LASIKassociated dry eye and neurotrophic epitheliopathy: pathophysiology and strategies for prevention and treatment. J Refract Surg. 2008;24:396-407. doi: 10.3928/1081597X-2008040114. 

Advancements in preoperative assessment, techniques help to enhance refractive surgical outcomes

Making the most of diagnostic technology toolkit 

 in which a loss of structural integrity leads to a bulging, cone-shaped cornea-is not uncommon, with incidence rates reported up to 265 per 100,000.

Based on the results of the U.S. Multicenter Clinical Trial of Corneal Collagen Crosslinking for Keratoconus Treatment, the original Dresden protocol entailing epithelial removal followed by application of riboflavin and use of full-fluence UV-A irradiation received FDA approval in 2016 for use in progressive keratoconus and in post-refractive ectasia as well. It’s also used off-label for infectious keratitis.

Unfortunately, disease onset tends to be in early adolescence, and these younger patients are at risk for rapid progression and a lifelong visual disability, noted Uri S. Soiberman, MD, assistant professor of ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.

eligible patients have been treated with CXL protocol with great success

. Eligibility criteria included 1 D or more of progression in corneal curvature per year, minimal corneal thickness of 400 Î¼m, and best spectacle-corrected visual acuity of 20/25 or worse.

“Our results at Wilmer are consistent with those of the larger randomized, controlled U.S. trial,” he said. “We see either stabilization or improvement in corneal curvature measurements in most of our treated patients. Treating very rapidly progressive disease remains a challenge, as well as very advanced disease. Early detection is of utmost importance in keratoconus.”

Unfortunately, epi-off CXL is not appropriate for all keratoconus patients.
	Patients with very advanced disease and thin corneas will not benefit from the treatment. New approaches are being developed, such as customized treatments, and novel epi-on (transepithelial) procedures.

This article was adapted from Dr. Soiberman’s presentation at the 2018 Johns Hopkins Wilmer Eye Institute’s Current Concepts in Ophthalmology meeting in Baltimore. Dr. Soiberman has no financial interests to disclose.

Stabilization, improvement in corneal curvature measurements seen in many treated cases

2019: State of corneal crosslinking for patients with keratoconus

The decision of which laser refractive surgery procedure for myopia to use with a particular patient may be made by considering the benefits and limitations of each, as they pertain to particular patients, i.e., “bespoke” refractive surgery.

laser refractive surgery performed as LASIK, PRK, or a lenticule extraction procedure (SMILE, Carl Zeiss Meditec) can improve vision, nonvisual function, and quality of life for patients with myopia. Because of advances, each method delivers safe and effective outcomes, said Jodhbir S. Mehta, MD, PhD. Each procedure has advantages and disadvantages that may be considered in relation to patient-specific factors to guide

“We now have three great laser-based procedures to treat myopia, and that raises the question of which to choose,” said Dr. Mehta, professor and head, Corneal and External Eye Disease, Singapore National Eye Centre, Singapore. “I believe we are now in the era of what I call ‘bespoke laser refractive surgery,’ meaning that it is often patient-related factors that will determine what we do. Rather than fitting our patients to what procedure we can do, we are fitting our procedures to our patients.”

A recently published paper by Dr. Mehta and colleagues reporting findings from an 18-year prospective audit of 

 from more than 53,000 eyes clearly shows how visual acuity results have improved over time with improvements in eye tracking, laser speed, ablation profiles, and nomograms.

“Comparative studies also show improvements in refractive outcomes using advanced ablation profiles, and most studies show that patients gain lines of BCVA after LASIK so that the efficacy outcomes well exceed the FDA standards,” said Dr. Mehta.

Direct comparisons of the different laser-based treatments for myopia is hampered somewhat by a relative dearth of head-to-head trials with SMILE. In one network meta-analysis that included a total of 48 randomized controlled trials, LASIK seemed to provide the best refractive outcomes. Due to advancements in excimer lasers, PRK outcomes have improved, including for the treatment of moderate to higher degrees of myopia, Dr. Mehta said.

“Compared with LASIK, PRK has advantages of a lower risk of ectasia and it avoids flap-related complications,” he said. “Slower visual recovery and risk of haze, however, remain potential drawbacks of PRK.”

While off-label application of mitomycin-C (MMC) is often used to reduce the risk of haze after PRK, MMC does not adversely affect the corneal endothelium. Some patients can experience a large drop in endothelial cell count.

“Histone deacetylase (HDAC) inhibitors, which are FDA-approved for treatment of hematologic cancers, have anti-fibrotic activity. In an experimental model, we found that an HDAC inhibitor was effective for mitigating corneal haze after PRK,” he said, adding results showed it was as effective as MMC with the potential for better short- and long-term safety.

The functional results after SMILE seems comparable to those achieved with the excimer laser procedures, but the lack of automated centration remains an issue with SMILE. Maintaining centration and reducing the energy of the laser when creating the lenticule improves SMILE outcomes.

He considers several “bespoke features” when deciding which laser refractive surgery is best for a patient seeking myopia correction. Because of the long time needed to create the lenticule, he excludes SMILE if a patient seems nervous or is likely to be uncooperative.

 are preferred over LASIK in patients whose occupation exposes them to risk of eye contact. SMILE patients with moderate to high myopia find the wound healing response is less intense after the femtosecond laser procedure than after an excimer laser ablation.

Other bespoke features he considers include:

Presence of dry eye-patients at risk of dry eye preoperatively may be more suited to PRK and SMILE than LASIK

Desire for rapid visual recovery-LASIK gives the fastest visual recovery followed by SMILE and then PRK

Level of preoperative HOA-high levels of HOA can be treated with a topography-guided ablation that is currently only available with LASIK and PRK.

This article is based on a presentation given by Dr. Mehta at the 2018 Refractive Surgery Subspecialty Day meeting. He receives lecture fees and grant support from Carl Zeiss Meditec and Ziemer.

Improving vision, nonvisual function, quality of life key for customized treatment plans

Laser refractive surgery advances expand options for myopic patients

RLE is a viable and very reasonable option to offer patients across the various ranges, says John Vukich, MD.

In a study comparing monovision LASIK with refractive lens exchange (RLE) in patients age 45 to 60, 

The study included 608 patients (1,216 eyes) in the monovision LASIK group and 590 patients (1,180 eyes) in the RLE group. Patients were –10 to +3 D and comparable in terms of preoperative cylinder, dry eye, glare, halos, and difficulty with night driving, said Dr. Vukich, adjunct associate clinical professor, University of Wisconsin-Madison School of Medicine.

Patients in the RLE group received an extended depth-of-focus (EDOF) IOL in at least one eye.

Among the patients, those in the 45 to 50 range were more likely to have monofocal 

, while those age 55 to 60 were more likely to have RLE. In those between ages 49 to 54, there was about an equal distribution between the two approaches.

Overall, both groups had solid and very comparable results, Dr. Vukich said. In the laser-vision correction (LVC) group, the postoperative sphere in the near eye had a distribution around –1.5 D.

For 3-month binocular uncorrected distance visual acuity results, the only difference found was in hyperopic RLE patients, who had a better result: 84.8% were 20/20 or better compared to 77% of those who received LVC.

For binocular near vision acuity, there was no difference in outcomes among the hyperopes, plano presbyopes, and low myopes in both groups. In the LVC group, 98.7% of high myopes had J5 or better uncorrected near visual acuity.

“The take-home point we’re starting to glean is there are some trends, but RLE is a viable and very reasonable option to offer patients across the various ranges,” Dr. Vukich said.

When analyzing patient satisfaction, it was 98% or better in the moderate to high myopes who had LVC, which was a higher percentage than other groups.

“But when you look at the hyperopes, plano presbyopes, and low myopes, there was no difference in the number of patients who were satisfied or very satisfied,” Dr. Vukich said. “Again, you’re starting to see a trend that RLE with an extended depth-of-focus lens is very comparable.”

When asked if they would recommend their procedure to friends and relatives, the moderate to high myopes in the LVC group had the highest percentage of positive responses, although all patient groups were in the high 80s to 90s.

The moderate to high myopes in the LVC group were not as satisfied with their closeup vision as those in the RLE group.

“There’s going to be some setting of expectations with those patients,” Dr. Vukich pointed out.

However, there was no difference between LVC and RLE for distance activities. For dry eye, there were no major statistical differences, although there was a trend for more dry eye among the RLE patients.

“That’s something that we might not have predicted,” Dr. Vukich said. Overall, the percentages of patients with dry eye were low in both groups. There was no major difference in the percentage of patients with difficulty night driving between the two groups.

the patients who were satisfied or very satisfied

 were mostly –1 D or greater than –1 D. However, there was a drop in satisfaction at –2 and  2.75 D, which gives surgeons some feedback for future targeting, Dr. Vukich said. Age did not appear to be a factor in the difference in satisfaction with the monovision a patient had, he added.

Surgeons looking to use LASIK monovision should aim for –1.25 to –1.75 D and provide thorough counseling to plano presbyopia patients, Dr. Vukich advised.

Dr. Vukich is a consultant for AcuFocus, Carl Zeiss Meditec, Johnson & Johnson Vision, and STAAR Surgical. This article was adapted from Dr. Vukich’s presentation during Refractive Surgery Subspecialty Day at the 2018 meeting of the American Academy of Ophthalmology.

Comparable levels of near, distance visual acuity; high patient satisfaction marks observed

Study: RLE, monovision LASIK results similar in 45-60 age group

Refractive lens exchange is a viable and very reasonable option to offer patients across the various ranges. Corneal inlays, when implanted at an appropriately deep corneal location, provide good near vision, minimizing the impact on uncorrected distance vision.

 have been made in refractive surgery technology that provide patients with numerous options from which to choose.

“Among the options, corneal inlays are one of the newest advances that we have seen,” according to William F. Wiley, MD, medical director, Cleveland Eye Clinic, Brecksville, OH.

The most recent developments in this market include the approval of the Kamra corneal inlay technology (AcuFocus) in mid-2015; the Raindrop Near Vision Inlay (ReVision Optics), which was approved in 2016 and recently pulled from the market; and the Flexivue Microlens (Presbia), for which approval is pending.

One of the biggest problems with corneal inlays in a refractive practice is 

 for the technology. In a typical refractive surgery practice, Dr. Wiley pointed out, most patients who seek out a refractive procedure are those with myopia and hyperopia who represent the smaller part of the bell-shaped curve of possible refractive clients.

“The traditional market audience for corneal inlays lies in the meat of that bell-shaped curve and represents over 100 million patients with presbyopia,” he said. “The reality is that it is hard to get those patients into the office.”

The target market for corneal inlays includes patients between 45 and 60 years old with a prescription ranging from +0.5 to –0.75 D who have had an eye examination within the previous year, he said.

“The issue with the presbyopic patient base is that the bulk of the target audience is not coming into our offices,” Dr. Wiley said. “They are solving their presbyopic problem with over-the-counter readers.”

 can now be offered a combination approach to meet their visual needs. The typical patient considering a refractive procedure is a 50-year-old with a bilateral refractive error of –4 D.

“This is the group that is motivated to become spectacle independent for distance and near vision,” he commented.

Dr. Wiley can now satisfy that patient’s goal for distance and near vision by combining inlays with a refractive surgery. Typically, he explained, the distance eye is targeted for plano and the non-dominant eye is left with about –0.75 D of myopia. During the same surgery for LASIK, the corneal inlay is implanted into a pocket that is under the LASIK flap.

“The excimer laser is the perfect tool to prepare the eye for the ultimate refraction,” he said.

Following surgery patients have 20/20 distance vision and functional near vision that continues to improve over time.

“These results let us increase the ‘wow’ effect on the first postoperative day,” Dr. Wiley said.

The key to building the corneal inlay patient base is the recognition that almost every presbyopic patient is a candidate for corneal inlays. LASIK is the perfect tool to bring those patients to the refractive sweet spot, he pointed out. When implanting the aperture inlay, that refractive sweet spot is –0.75 to –1 D. Dr. Wiley explained that functionally the intermediate vision interacts with the aperture optic to extend the focus to both distance and near vision.

Combining LASIK, corneal inlays hits refractive ‘sweet spot’ for many patients

Ophthalmology Times, March 15 2019

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