Eyeworld

26 | EYEWORLD | AUGUST 2019 ATARACT C 0.25 D, the meridian within 5 degrees, and the average K values are within 0.2 D of each other," Dr. Yeu said. "If these are inconsistent among devices, I carefully review the placido keratoscopic images and perform a close ocular surface examination. These patients often have ocular surface disease (i.e., corneal staining, anterior basement membrane dystrophy, rapid tear breakup time). Such patients are started on dry eye treatment and return for repeat mea- surements, especially if the patient opts to have their corneal astigmatism surgically corrected at the time of cataract surgery." Patients to avoid Dr. Raviv avoids using toric lenses in patients with ocular surface disease, epithelial basement membrane dystrophy, Salzmann's nodular de- generation, and pterygium. "In these cases, it is best to optimize or operate on the proximate cause of the astig- matism, rather than placing a toric IOL," Dr. Raviv said. Dr. Raviv uses three to four preop mea- surements of the corneal Ks. If he finds signifi- cant discrepancies among the tests, even after ocular surface optimization, he will not proceed with toric lens use. Additionally, patients who wear rigid gas permeable contact lenses and plan to continue their use are viewed as a relative contraindica- tion to use of a toric IOL, Dr. Raviv said. Dr. Yeu avoids toric lenses in severe dry eye patients whose measurements are incon- sistent; patients with pterygium; patients with anterior basement membrane dystrophy; and those with Salzmann's nodular degeneration, who are not willing to undergo either pterygi- um repair or a superficial keratectomy prior to cataract surgery. Also avoided are those with irregular astigmatism such as seen post-RK or in severe ectasia patients. "I will use toric IOLs off-label in patients with irregular astigmatism that is consistent in amount and meridian between the MRx as well as the diagnostics," Dr. Yeu said. Toric Calculator can also account for posterior corneal astigmatism in its toric IOL selection using a proprietary in-house nomogram. Dr. Patterson uses the Barrett Toric Calcu- lator and Ladas Super formula. To account for posterior corneal astigmatism, Dr. Patterson has used total K on the IOLMaster 700 (Carl Zeiss Meditec). "But I don't think this PCA measurement is knowledgeable enough yet in formulas, and therefore I am not using it currently in my toric calculations," Dr. Patterson said. Dr. Raviv said the Barrett Toric Calculator, which estimates the posterior corneal astigma- tism, has been shown to be more accurate than current direct measurement devices and is his formula of choice. Additionally, he uses a color LED topographer, which measures the poste- rior cornea and intraoperative aberrometry to give insight into the total corneal astigmatism. "I am carefully following the other pos- terior corneal measuring instruments such as Scheimpflug and swept source OCT for contin- ued improvement," Dr. Raviv said. "When using a formula that estimates for posterior cornea, it is important to use the anterior Ks, not the 'to- tal K,' which would lead to a double accounting of posterior astigmatism." Among preop testing, Dr. Gupta said it is very important to assess whether or not the corneal astigmatism is regular or irregular. "Caution should be exhibited in anyone with irregular astigmatism with respect to using a toric IOL," Dr. Gupta said. "It is also critical to look for corneal pathology that may be in- ducing astigmatism, such as pterygium, anterior basement membrane dystrophy, and dry eye. These conditions should be treated prior to cat- aract surgery as they may alleviate astigmatism." Dr. Yeu uses the LENSTAR (Haag-Streit) for quantity and meridian of astigmatism and checks against Placido topography (Atlas [Carl Zeiss Meditec] or OPD-Scan III [Nidek]) for quality and quantity of astigmatism. She evalu- ates the anterior and posterior cornea directly with an LED topographer (Cassini [Cassini Technologies]). "I make certain that among the diagnos- tics, the magnitude of astigmatism is within Financial interests Gupta: Johnson & Johnson Vision, Alcon Patterson: None Raviv: Johnson & Johnson Vision, Cassini Technologies Yeu: Johnson & Johnson Vision, Alcon, Bausch + Lomb, iOptics continued from page 24

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