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Astigmatism: a New Standard of Care Bridging the Gap to Cataract Refractive Surgery

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Astigmatism: a New Standard of Care Bridging the Gap to Cataract Refractive Surgery A Sponsored Supplement From Astigmatism: A New Standard of Care Bridging the Gap to Cataract Refractive Surgery A high proportion of cataract patients are significantly astigmatic (1) – and this can compromise their quality of vision post-surgery (2). There are diverse methods to address astigmatism at the time of the cataract surgery, but not all are equally effective (3). Could advanced instrumentation and toric IOLs change the standard of care? The consensus at Alcon Axis Advanced Workshop, held in Barcelona, Spain, on October 26, 2018, is that it can – even in patients with only mild astigmatism. Andrzej Dmitriew, Department of Ophthalmology, Poznan University of Medical Sciences, Szpital św. Wojciecha Poznan, Poland Kjell Gunnar Gundersen, IFocus Eye Clinic AS, Haugesund, Norway Norbert Pesztenlehrer, Department of Ophthalmology, Petz Aladár County Teaching Hospital, Gyor, Hungary Humberto Carreras, Eurocanarias Oftalmologica, Las Palmas de Gran Canaria, Spain www.alcon.com 2 Sponsored Feature Part I: The “As little as 0.5D Sidebar 1. importance of post-surgical post operative astigmatism astigmatism can astigmatism correction results (1); patients significantly affect Andrzej Dmitriew, Poland implanted with patients’ non-toric IOLs Why bother correcting astigmatism in cataract surgery patients? Because as little functional vision.” Pre-operative corneal as 0.5D post-surgical astigmatism can astigmatism: significantly affect patients’ functional vision – Andrzej (2) – and toric IOLs can now address not • 78% (n=85 650) ≥0.5 D just 2D astigmatism and over, but 1D and Dmitriew • 42% (n=46 003) ≥1.0 D below (4). We can completely change our • 21% (n=22 899) ≥1.5 D attitude to mildly astigmatic patients: it is no • 11% (n=11 651) ≥2.0 D longer necessary to accept compromises worsening then the visual acuity (1). This that leave them with poor functional vision. conclusion was based on very significant Post-operative refractive And this change in at titude is well overdue: patient numbers: 110,000 pre-operative astigmatism results: consider the prevalence data, based on readings and 40,000 post-operative the real-world recent studies. Among readings. Similarly, data from the Swedish • 90% (n=35907) ≥0.5 D cataract patients, 70 percent or more Cataract Registry indicate that 60 percent • 58% (n=22886) ≥1.0 D showed ≥0.5D of corneal astigmatism and of patients remain with 0.5D of corneal • Visual acuity tended to may benefit from astigmatism correction astigmatism after surgery (Sidebar 1 (6)). worsen postoperatively (1, 5); furthermore when a non-toric IOL In Dmitriew’s opinion, therefore, it with increased astigmatism is implanted in an astigmatism patient, is misguided to apply arbitrary cut-offs (ρ=−0.44, P<0.01) the astigmatism magnitude might beneath which astigmatism is left untreated; be higher after cataract I advise all surgeons to move towards surgery than before correcting astigmatism wherever possible, even where post-operative astigmatism is predicted to be under one diopter. It really should be part of the standard of care! Sponsored Feature 3 Part II: Sidebar 3. Benefits of astigmatism Astigmatism correction with toric IOLs (3) treatment Kjell Gundersen, Norway Toric IOLs provide better postoperative UCDV- A Preoperative astigmatism is common compared to non-toric and is not reduced by cataract surgery and non-toric IOLs + and monofocal IOL implantation (1). Therefore, to improve visual outcomes, relaxing incision we must correct astigmatism when we treat cataracts. Unfortunately, many cataract surgeons simply don’t care Greater spectacle about astigmatism! But the rest of us Toric independence with do have some options (Sidebar 2). IOLs toric IOLs than non-toric, Limbal relaxing incisions will reduce combination of non-toric astigmatism in most cases, but are not as effective, precise and predictable as toric and relaxing incision IOLs (3). Laser vision correction can be useful in patients with high astigmatism, Lower postoperative astigmatism but is not universally applicable: those with stable keratoconus and 6D with toric IOLs compared astigmatism or above may be better with non-toric IOLs and served by use of toric IOLs. Furthermore, combination of non-toric IOLs remember the ocular surface (Sidebar + relaxing incision Sidebar 2. Astigmatism treatment options • Toric lens Figure 1. Benefits of astigmatism correction with toric IOLs (3) • Laser vision correction - PRK 5); most cataract patients are over 50 better functional outcomes and - LASIK years of age – either they have a dry spectacle independence – and fewer - SMILE eye problem, or the laser will create post-operative complications – than • Limbal relaxing incisions one! Leaving a mild refractive error is combinations of non-toric IOLs and - Arcuate (manual or far preferable to instigating chronic dry relaxing incisions (3). And the impact FLACS) eye disease. on workflow is minimal – it takes only - Opposite clear corneal Toric IOLs, however, give better a little more surgeon time to implant incision (pay attention outcomes than relaxing incisions or laser a toric as opposed to a non-toric lens. to nomogram) surgery (3), and better uncorrected In my opinion, therefore, the toric distance vision. Even at very low values lens is unquestionably the best option of astigmatism, toric IOLs provide (Sidebar 3). www.alcon.com 4 Sponsored Feature Andrzej Dmitriew, Poland an incision’s effect on a specific axis. Cornea, astigmatic correction and visual outcomes... however, is a living biomechanical structure; Failure to account for posterior corneal But how exactly should we manage cataract it does not react to incisions as if it were a astigmatism in toric IOL calculations can patients with astigmatism? First, we should simple monofocal lens, and therefore older lead to overcorrection in eyes that have WTR appreciate that predictable results require a formulas cannot always predict its behavior. anterior corneal astigmatism and under stable platform. A history of over 100 million Barrett toric calculator utilizes centroid vector correction in eyes that have ATR anterior procedures provides abundant evidence for calculations for improved SIA accuracy. corneal astigmatism.” (13) the rotational stability of the AcrySof® IQ Therefore, I strongly recommend the Accounting for PCA is also assisted by Toric IOL: mean Acrysof rotation is 2.72 new Alcon Online Toric Calculator, not advances in instrumentation. But what degrees, versus 3.79 degrees for TECNIS® least because it is based on the Barrett option should we choose? I believe that Toric (7). Similarly, 91.9 percent of AcrySof ® algorithm, which is superior to ray- the best keratometry tool is the one IQ Toric implantations rotate by 5 degrees tracing software and other formulae that works best for you. I use VERIONTM or less versus 82.8 percent for TECNIS® (Figure 2, Table 2 (8, 9)). for measuring axis and astigmatism Toric (Table 1 (7)). “Because SIA is a vector, it has both magnitude, and a Scheimpflug camera Second, we should be aware of new magnitude and angular direction, and and Pentacam as a control approach. This concepts in astigmatism treatment – not both vector components must be included approach helps avoid significant surprises; least, work on posterior corneal astigmatism when calculating the median or mean for example, by identifying patients with (PCA). The large difference between with- SIA in a group of cases... It is critical to posterior keratoconus or other corneal the-rule (WTR) and against-the-rule (ATR) account for posterior corneal astigmatism pathology that could cause deviation from patients, in terms of refractive outcomes, in cataract patients to achieve optimal pre-operative predictions. Feel free to is due to PCA. Ignoring posterior corneal post-operative outcomes.” (11) use any biometer for K values, but you astigmatism may yield incorrect estimation “It is important to consider posterior must always remember to optimize lens of total corneal astigmatism. Failure to corneal astigmatism in toric calculations constants for each device separately – that’s account for it in toric IOL calculations may as the posterior cornea acts as a minus very important. result in significant residual astigmatism lens ... Both the anterior and posterior Accurate location of the principal due to overcorrection in eyes with WTR corneal surfaces contribute to the total meridian is very important in irregular astigmatism and undercorrection in those corneal astigmatism.” (12) corneas, and is the main reason to with ATR astigmatism. Using the devices “Posterior corneal astigmatism can impact use topography, but you can also use that calculate total corneal astigmatism based on anterior corneal measurements AcrySof® IQ Toric TECNIS® Toric only, WTR astigmatism was overestimated by 0.5 to 0.6 D and ATR astigmatism was IOL rotation, degrees (95 percent CI) 2.72 (2.35-3.08)* 3.79 (3.36-4.22)* underestimated by 0.2 to 0.3 D (8). The old Alcon calculator didn’t allow Rotation ≤5 degrees 91.9 percent* 81.8 percent* for PCA, and therefore wasn’t ideally predictive; The new Barrett calculator Rotation ≤10 degrees 97.8 percent* 93.2 percent* theoretically accounts for PCA in WTR and ATR eyes (9), axial length and anterior Rotation ≤15 degrees 98.6 percent* 96.4 percent* chamber depth in ELP estimates permitting more precise astigmatic prediction (10). Rotation ≤20 degrees 98.9 percent 97.4 percent Based on the Douglas D. Koch and Li Wang ≤ theory, Surgically Induced Astigmatism (SIA) Rotation 30 degrees 99.5 percent 99.4 percent is a vector, it has both magnitude and angular Rotation >30 degrees 0.50 percent 0.60 percent direction, and both vector components must be included when calculating the median or CI = confidence interval; IOL = intraocular lens mean SIA in a group of cases (11). Previous approaches to SIA calculation were based *P < 0.05. only on the numerical average for a specific meridian or axis, and hence only accounted for Table 1. Toric intraocular lens rotation: percentage of eyes demonstrating rotational stability (7). Sponsored Feature 5 topography to distinguish between regular • Consider refining your outcomes by within cataract surgery, but not and symmetrical astigmatism.
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