Fred Gebhart

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Intraoperative aberrometry and newer-generation IOL formulae have signifi cantly decreased error in predictions of correction, but error still occurs. It is important to use that error as information when planning fellow eye surgery.

For cataract patients who have “normal” eyes, the error between the predicted refractive correction and the actual correction 

 for the fellow eye, and a small study has found a good correlation between prediction error in the two eyes. “Cataract surgery in today’s world is very much a refractive procedure,” said Steven Naids, MD, Advanced Vision Care in Los Angeles.

“Achieving predictable and reproducible outcomes is very important.” Dr. Naids and colleagues tested the hypothesis that error in the first eye can guide decisions in IOL selection for the fellow eye. They compared predictive error, the difference between the manifest spherical equivalent and the predicted spherical equivalent, across multiple formulae and discussed whether predictive error in the first eye can help determine the correction needed in the fellow eye.

“Intraoperative aberrometry and newer-generation IOL formulae have significantly decreased error in our predictions of correction, but error still occurs,” Dr. Naids said. “It is important to use that error as information when planning fellow eye surgery.” The retrospective study looked at 196 eyes of 98 cataract patients with average eyes and uncomplicated phacoemulsification across surgeries performed by a single surgeon. All of the eyes had average axial length, 22.5 mm to 25.0 mm. Patients with prior refractive surgery or macular pathology were excluded.

The selected IOL power was determined by ORA for all patients. The predicted spherical equivalent based on the lens power as determined by ORA was retrospectively recorded for Barrett Universal II, Hill RBF, Haigis, Olsen, and Holladay I.

The cohort was subdivided into two groups: 58 patients who had a targeted refraction outside of the parameters of the original Hill RBF formula, and 40 patients evaluated with Hill RBF included. There was no significant difference in refractive error between the groups. There were numerical differences. For a plano target, Hill RBF had the lowest mean and median absolute error in the cohort of 40 patients, 0.16, followed by ORA, 0.17, and Barrett, 0.18.

In the initial cohort of 58 patients, the mean absolute error was lowest in ORA, 0.20, and Barrett, 0.26. In the combined cohort of 98 patients, the percentage of eyes within 0.50 D of predicted was highest with Hill RBF, 92.05%, followed by ORA, 91.38%. Olsen produced the lowest percentage of eyes within 0.50 D of predicted, 81.90%, with Holladay at 85.34%, and Barrett and Haigis at 87.07%.

Most of the eyes were within 0.25 D of predicted, Dr. Naids added, a clear indication that all of the current-generation formulae are effective and can be expected to produce results that are generally satisfactory to patients.

“If you are a half-diopter off, you won’t be able to read your iPhone easily and that is not satisfactory to patients today,” he said. It is not clear why the formulae failed by as much as a diopter in a few eyes.

All of the eyes had normal axial length and keratometry. None had had any prior refractive surgery. The study found a statistically significant correlation between the prediction error and both the first and second eyes using the current formulas as well as ORA when using a linear regression model. It is possible to anticipate the directional error in the first eye using the prediction error seen in the first eye to reduce the error in the second eye.

A study group of 20 patients outside the primary cohort found the predictive error in the first eye confirmed the IOL power for the second eye in 11 patients and changed the expected 

 in six patients. Having the predictive error in the first eye did not help three. The next step is a similar study in a larger cohort to evaluate the effects of different formulae and predictive error in eyes that are more reflective of the general population and eyes that may not have standard axial length.

This article was adapted from Dr. Naids’ presentation at the 2018 meeting of the American Academy of Ophthalmology. Dr. Naids has no financial interests to disclose.

Articles

Error in first eye can guide decisions in IOL selection for fellow eye of patients

Predictable, reproducible outcomes key in cataract surgery planning

Newer lab studies reveal increased posterior chamber depth does not cause ND and that any IOL, irrespective of material or edge design, implanted in the capsule bag can result in ND, which resolves when the very same inciting lens is moved from the bag to the ciliary sulcus.

Dysphotopsia may be one of the most under recognized complications following otherwise unremarkable 

 20% of patents have negative dysphotopsia (ND), a temporal dark shadow after intraocular lens implantation. Other patients have positive dysphotopsia (PD), characterized by light streaks, arcs, central light flashing or star bursts. Some patients may have both ND and PD.

“Overall, dysphotopsia has not been studied particularly well, especially epidemiologically,” said 

, founding partner, Advanced Vision Care, and clinical professor of ophthalmology at the David Geffen School of Medicine, Stein Eye Institute, University of California, Los Angeles. “There are likely 400,000 to 500,000 new cases of chronic ND every year globally.”

The good news, he continued, is that early ND symptoms tend to improve over time due to neuro-adaptation, but about 3% of cases will have chronic ND at one year after surgery. The better news is that novel IOL designs and surgical techniques can correct and prevent ND.

PD is directly related to square edge design and the index of refraction of an IOL. The higher the index of refraction, the greater the likelihood of PD after the lens is implanted. The etiology of PD is well understood.

Excellent visual outcomes achieved with novel trifocal design


	However, ND is far more complicated. It is a temporal dark arc, similar to the effect of putting blinders on a horse. Unlike PD, there is no good correlation between clinical findings and optical lab findings, Dr. Masket said.

Some researchers have suggested that square edges can cast ND shadows where rounded edges do not. And some have indicated that ND is also associated with a greater iris to IOL distance and an expanded posterior chamber depth. However, these assertions are not supported in clinical investigations.

Newer lab studies reveal increased posterior chamber depth does not cause ND and that any IOL, irrespective of material or edge design, implanted in the capsule bag can result in ND, which resolves when the very same inciting lens is moved from the bag to the ciliary sulcus.  These findings suggest a relationship between the IOL and capsule bag as central to ND.

“Historically, every intraocular lens on the market in the United States has been associated with ND,” Dr. Masket said. “Clinically, any in the bag IOL with the capsulotomy edge overlying the optic, especially on the nasal side, may be associated with ND. While ND is likely multifactorial, it is prevented, relieved or improved when the IOL optic edge overlies the nasal capsulotomy, rather than the capsulotomy overlying the optic edge.”

Considering surgical methods for late in-the-bag IOL dislocation

Dr. Masket published  reverse optic capture (ROC), either as a therapeutic or prophylactic measure for ND, in 2011. A 2018 update with ROC in 43 eyes showed very good success, he reported. Of 22 eyes with chronic ND, 21 were corrected with secondary ROC and 21/21 contralateral eyes successfully avoided ND using primary ROC.

“We have never had a failure doing primary reverse optic capture, he said. “We have also had success with bag-sulcus exchange and some success with piggyback lenses, but not with bag-bag exchanges.”

But primary ROC is not without concern. All of the eyes that underwent primary ROC placement had fibrotic PCO that required laser posterior capsulotomy within three months of the initial surgery. And long-term piggyback or sulcus placement have the potential for iris chaffing and decentration.

“I developed an anti-dysphotopic IOL that mimics reverse optic capture but leaves most of the lens in the bag to prevent fibrosis,” Dr. Masket said. “The lens has a grove on the anterior optic edge to capture the capsulotomy. That arrangement provides for optic overlying the capsule rather than the capsule overlying the optic, and the IOL becomes fixated by the anterior capsule.”

Why remove an IOL? Survey brings key trends into focus

Dr. Masket’s original lens was licensed and modified by Morcher. It has CE marking and is being developed as the model 90S. There have been no symptoms of ND in the first 175 lenses implanted, he reported, six cases of non-debilitating PD and no iris chafe.

Two other capsulotomy supported IOLs have been CE marked,  he reported, the Tassignon “BIL” (Morcher) and the Femtis (Occulentis). The Tassignon lens has had no reported ND in several thousand uses and the Femtis has had no ND in its reported series of 384 lenses, providing clear support for the theory that optic over capsule, rather than capsule over optic, will prevent ND.

In addition to the absence of ND, capsulotomy supported IOLs have a more predictable ELP, a stable toric axis, absence of capsule contraction, perfect centration when the capsulotomy is centered on the visual axis , reduced HOA and limited optic tilt.

“There is likely a future for this design concept,” Dr. Masket concluded.

Dislocation and decentration remain common reasons for IOL removal

This article was adapted from Dr. Masket’s presentation at the 2019 Congress of the European Society of Cataract and Refractive Surgeons. Dr. Masket is the patent holder for an anti-dysphotopic IOL that is being developed by Morcher GmBH

New IOL design trends avoid negative dysphotopsias

Don’t discount dysphotopsias, either positive or negative, after cataract surgery and IOL placement. The literature suggests that dysphotopsias are relatively rare, but patient reports suggest a different story.

Don’t discount dysphotopsias, either positive or negative, after 

 placement. The literature suggests that dysphotopsias are relatively rare, but patient reports suggest a different story

“If you ask patients, it can be almost 50% immediately after surgery,” said 

, professor of ophthalmology, John A. Moran Eye Center, University of Utah, Salt Lake City. “The majority of these just go away or patients get used to them. But for an important minority of patients, these are significant visual issues and they don’t improve as time goes on.”

Dr. Mamalis discussed the etiology and treatment of positive and negative dysphotopsias during the 

37th Congress of the European Society of Cataract and Refractive Surgeons in Paris

. Positive dysphotopsias produce visual artifacts that appear as areas of bright light, streaks and flashes central in the visual field. Negative dysphotopsias produce dark temporal shadows that mimic the effect of blinders worn by racehorses.

Both positive and negative dysphotopsias are associated with the IOL material, design and placement, he continued.

Precise alignment helps surgeons focus on best toric IOL post-op results

Positive dysphotopsias are most often characterized by persistent bright rings, flares, arcs, halos, and flashes that most often appear when light is coming into 

 the eye from the side, such as the oncoming headlights of another vehicle.  The long term incidence may be as high as 1.5% and can vary greatly by IOL type, material, and design.

Positive dysphotopsia was first reported in polymethylmethacrylate (PMMA), the material most commonly used during the early development of IOLs. Symptoms were generally minor glare and transient.

Hydrophobic acrylic lenses are more prone to positive dysphotopsia. The higher index of refraction is more likely to result in internal reflections when exposed to bright sources.

Silicone lenses are rarely associated with positive dysphotopsia, possibly because of lens design. Lenses with square edges, typically hydrophobic acrylic IOLs, are associated with an increased incidence of positive dysphotopsia. Frosted and textured edges as well as beveled designs have been used to reduce the intensity of stray reflections and reduce the incidence of positive dysphotopsia.

Research shows small-aperture IOL is bringing stability into focus

Treating positive dysphotopsias is relatively straightforward. Explanting and exchanging the original lens with an IOL that has a different material or edge 

design usually reduces or removes the problem entirely. PMMA, silicone, and hydrophilic acrylic lenses with edge designs that are not square are reported to help resolve positive dysphotopsias.

“Negative dysphotopsias are completely different,” Dr. Mamalis said. “The more often you ask about negative dysphotopsias, the more frequently patients report those dark temporal shadows, especially in the first couple of weeks.”

About 71% of negative dysphotopsias resolve in the first weeks and months after surgery, he continued. Depending on how and when patients are questioned, between 0.2% and 2.4% have persistent symptoms.

“Don’t get too excited at first and try to do something about it immediately,” he advised. “In a lot of patients, it goes away.”

Pushing the boundaries with monofocal toric IOL

The etiology of negative dysphotopsias involves the spatial relationships between the IOL, the capsular bag, and possibly the iris. IOLs implanted in the capsular bag or in the posterior chamber are more likely to produce negative dysphotopsias while IOLs implanted in the sulcus or in the anterior chamber seldom do.

Ray tracing suggests that at least part of the problem lies with internal reflections when the lens is placed in the capsular bag that can cast temporal shadows. Other potential factors include corneal curvature, anterior chamber depth, IOL power, axial length and the distance between the pupil and the implant.

“Negative dysphotopsias are seen more frequently in patients who have a square edge IOL,” Dr. Mamalis said. “It can occur with any lens material, though we see it more frequently with hydrophobic acrylic.”

Treatment typically involves IOL exchange and implantation of a new lens into the sulcus. Piggyback, or add-on, IOLs can also help alleviate negative dysphotopsias by diffusing light more effectively before it enters the eye, reducing the potential for shadow formation.

Reverse optic capture, placing the optic over the edges of the capsular bag instead of in the bag, can also help. And some surgeons perform laser anterior capsulotomy to enlarge the capsule opening.

New lens designs may reduce the problem in the future. The Masket lens, with a groove on the anterior surface, allows the lip of the optic to ride over the anterior capsule, reducing the potential for negative dysphotopsias. A bag-in-lens design serves the same purpose, putting the optic atop the bag rather than allow the bag to ride over the edge of the optic.

Another design adds peripheral concavity to the optic to better diffuse light entering the eye, reducing the potential for shadows.

“The treatment varies,” Dr. Mamalis said. “Depending on the patient, changes in IOL material, design and placement can decrease or treat these dysphotopsias when they occur.”

Dr. Mamalis is professor of ophthalmology, John A. Moran Eye Center, University of Utah, Salt Lake City. He did not indicate any proprietary interest in the subject matter.

Dealing with positive and negative dysphotopsias

Early data show generally positive outcomes following bilateral implantation of a new extended depth of focus (EDOF) intraocular lens.

A retrospective analysis of clinical and patient reported outcomes three month after bilateral implantation of the Zeiss AT Lara 829MP (

) in 293 patients found that 86.7 percent of eyes were within 0.50 diopters of emmetropia.

Most patients, 95.4 percent, were spectacle-free for distance vision and 83.6 percent were spectacle-free for near vision.

“This is the first cohort of patients who have had this lens implanted at Optical Express” said Julie M. Schallhorn, MD, MS, assistant professor of ophthalmology at the 

. “Especially in our younger patients, in their 50s and 60s, so much of our lives are on our phones and tablets. Having a lens that can give you that phone vision and tablet vision without sacrificing distance vision, is very, very attractive for patients.”

How to manage patient’s IOL expectations pre-operatively

The analysis includes all patients from September 2017 through September 2018 who returned for their one-week, one-month and three-month post-op visits. Dr. Schallhorn is senior author for an article published in the Journal of Refractive Surgery.

A longer term evaluation of both clinical and patient reported outcomes is currently under way. Dr. Schallhorn pointed out that while the AT Lara lens has not yet been ap-proved for use in the United States, it is currently approved for use in the European Union and other jurisdictions. It is a hydrophilic IOL with 25% water content and a hydrophobic surface.

The device has four-point haptic fixation, 6-mm optic diameter, 11-mm overall length and is available in a range of -10.00 to +32.00 D in 0.50 D increments. A toric version of the lens (AT Lara 929MP) is also available but was not used in this cohort. The AT Lara is based on a diffractive principle.

It is aspheric, aberration-neutral and chromatic aberration-correcting to provide a progressive visual field across three focal points: distance, 1.90 D for far-intermediate and 0.95 D for near-intermediate distances. All of the patients in the analysis had bilateral implantation with no prior history of refractive surgery and no ocular comorbidities other than refractive error or cataracts.

Most of the patients, 232 (79.2%) underwent implantation for refractive correction while 61 patients (20.8%) had cataracts, most often mild, with CDVA no worse than 20/32. The mean age of the cohort was 59 with a slight preponderance of men, 54 percent. The mean preop sphere was +1.50 D, mean cylinder was -0.51 D and the mean manifest spherical equivalent was +1.24 D.

IOL decisions for glaucoma patients involve multiple considerations

“With any new lens, you want to see how it performs in your average, everyday patient off the street,” Dr. Schallhorn said, “how they like it, how it is working for them. That’s why we did this retrospective evaluation.”

Three months after implantation, 86.7% of eyes were within ±0.50 D of emmentropia and 98.3% were within ±1.00 D of emmentropia. The mean MSE was -0.05 D with a coefficient of determination of 0.96. The mean prediction error, the difference between the predicted MSE and achieved MSE, as -0.07.

Most of the eyes, 90.8%, had monocular UDVA of 20/25 or better at three months and all eyes had CDVA of 20/25 or better. Just over half of eyes, 57.5%, had the same UDVA after surgery as the CDVA before surgery. Nearly all patients, 97.4%, had binocular UDVA of 20/25 or better.

Uncorrected near vision at 40cm was expectedly less than distance vision, Dr. Schallhorn said, as the EDOF lens has a near focal point of about 60cm. A solid majority of eyes, 84.6%, had monocular UNVA of 20/50 or better at three months and 91.6% had binocular UNVA of 20/50 or better.

There were no serious or unexpected adverse events associated with the lens. There were no explants during the first three post op months and no patients declined the AT Lara implant for their second eye.

Patient reported outcomes were generally very favorable. Two-thirds of patients (66.6%) completed a patient experience questionnaire at three months, down from 85% preoperatively and 69.6% at one month.

Most patients, 90.3%, said they were satisfied or very satisfied with their new vision, Dr. Schallhorn reported. Slightly more, 90.8%, said their vision at three months met or exceeded their expectations.

The most commonly reported visual symptoms during the first three months of follow up included glare, halo and starburst. There was an initial increase in severity of visual symptoms during the first month after implantation and a small but statistically significant decreases in symptoms between the one-month and three-month visits.

Experience with other EDOF lenses show that it can be difficult to accurately assess visual symptoms during the early post op months. Symptoms can be a factor of lens design but also due to post op inflammation, corneal edema, dry eye, superficial keratitis, refractive error and other causes. Longer term follow up with other EDOF implants suggest that continued improvement in visual symptoms may be expected.

“Patients like multifocal lenses,” Dr. Schallhorn said. “We have seen that in study after study. But multifocal lenses come with more symptoms We see a very good potential for this lens, but it will require careful patient selection and counseling in terms of near vision results and the potential for optical side effects.”

This article is based on Dr. Schallhorn’s presentation at the 2019 American Society of Cataract and Refractive Surgery annual meeting. Dr. Schallhorn has no financial disclosures to report.

A study reviews the results, and patient satisfaction following bilateral implantation of an extended depth of focus intraocular lens.

Author | Fred Gebhart

Articles

New IOL design trends avoid negative dysphotopsias

Dealing with positive and negative dysphotopsias

Surgeons eye letter-perfect outcomes with new extended depth of focus IOL

Predictable, reproducible outcomes key in cataract surgery planning