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4 Based on our findings, we now aimnow we findings, our on Based mayreadings K accurate Obtaining of results. of eyesin D -0.75 of target refractive a for keratoconusmoderate to mild with thansteeper for D -1.25 and thatunderstanding the with D, 47.00 ormyopic have may these 1). (Figure surprises hyperopic CONTACT LENSES patientskeratoconic in difficult be who wear contact lenses, whether toric gasrigid or lenses, hybrid lenses, soft dopatients These lenses. permeable contact their of out be to like not needoften they but long, very for es measurementsmultiple undergo to takecan warpage lens contact because whenOften, ameliorate. to time long a showed a hyperopic refractive predic refractive hyperopic a showed had formula Barrett the but error, tive median and mean absolute lowest the Further,errors. predictive refractive using relationship linear a was there 1Holladay the with (simK) K simulated any and D, 47.00 about to up formula rangelarger a in resulted steeper thing - - All formulasAll 4 3 2018 This past year, my colleagues and colleagues my year, past This Additionally, the anterior chambers in chambers anterior the Additionally, with often end upend often keratoconus with Eyes the effective lens position. Assumptionsposition. lens effective the eyesnormal for calculations IOL in made alet Watson eyes. these for true not are inlow was error hyperopic that showed moder and D) 48.00 < (K mild with eyes D) 48.00–55.00 = (K ate keratoconus errorsthat but , after severein unpredictable more were keratoconus. andOlsen, Barrett, the compared I ofcohort a in formulas 1 Holladay keratoconus. with eyes hyperopic after . Thissurgery. cataract after hyperopic because patients for frustrating be can myopic.previously were them of most kera irregular is factor causative One typesof variety a With (K). tometry unclearis it keratoconus, of grades and inuse to best are readings K which withPatients calculations. power IOL axial long have sometimes keratoconus contributefurther can which lengths, error.hyperopic to toproportional not often are eyes these CHALLENGES IN IOL CALCULATION CALCULATION CHALLENGES IN IOL AND PITFALLS AND MARCH

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- - - - - Keratoconus makes IOL power calculations more complicated. IOL power calculations more complicated. Keratoconus makes MD BY SUMITRA S. KHANDELWAL, and it has become appar become has it and

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eratoconus is a progressive thin progressive a is eratoconus resultsthat the of ning Recentastigmatism. irregular in prevalencea show calculations highertimes 10 to five is that As patients with continuecataracts with patients As pography. As the average simK increases, the error topography. As the average simK increases, the error Figure 1. Relationship of refractive predictive error using the Holladay 1 formula related to mean simK on Galilei (Ziemer) becomes more hyperopic. Once the keratometry is greater than 47.00 D, the values become less correlated.

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I tell patients that, ideally, they should correct all errors. The may SPHERICAL ABERRATION stop wearing their hard contact lenses still need or contact lenses for Even when the correct IOL power for 1 month for every year they have the best vision, but outcomes can be is determined, the should be worn them, they are reluctant to even very good. It is important to watch aware of the positive or negative sphe- undergo surgery. for progression of keratoconus after ricity of the IOL chosen. The kerato- I let these patients know that, if surgery. The risk of progression is conic cornea is unique in its sphericity. they plan to continue to wear hard thought to be lessened by use of a Most corneas have increased positive contact lenses after surgery, then we small limbal or scleral tunnel incision. spherical aberration over time, but the can ease up on this rule. I have them For patients who are happy in hard cone in the keratoconic cornea creates remove one lens at a time for 2 weeks, contact lenses or scleral lenses, be a negative spherical aberration, much take the measurements in that , cautious in placing a toric IOL. It is like a cornea after hyperopic LASIK. then repeat them 1 week later. If important to counsel these patients Because most IOLs have a slight nega- the two measurements match, then that their vision with a toric IOL is tive spherical aberration, one should I move on to surgery, knowing that never going to be as good as it is with consider choosing a true aspheric lens the patient’s cornea will change even their hard contact lenses. Further, such as the enVista IOL or the SofPort more afterward. it is hard to get good topographies AO Aspheric Lens (both Bausch + For those who wear scleral lenses, I in these patients, as they tend to be Lomb) or a positive spherical lens such am not so concerned, although I do long-term lens wearers, and the ability as the Sensar (Johnson & Johnson ask these patients to stop wearing to reverse warpage is Vision). the lenses for at least 5 days before uncertain. However, if the patient surgery. Because scleral lenses do not states that he or she is interested in CONCLUSION rub on the cornea, they do not cause being less dependent on contact lenses We will continue to see more the same amount of corneal warpage, and is willing to come in for multiple keratoconic patients in our cataract and we often see normalization of the measurements without the lenses, I evaluations. The expectations of these cornea within 24 hours. Additionally, may consider a toric lens. If, on the patients can be just as high as those these patients often go back into their other hand, patients say they want of other refractive cataract surgery scleral lenses, which provide comfort better vision, I advise them that they patients. To obtain the best outcomes and correction after surgery. may need to upgrade to a scleral or a for these patients, must per- It is important to note that if a reverse-geometry lens. form proper patient counseling, make patient may go back into contact lens- careful preoperative measurements, es after surgery, the surgeon should REFRACTIVE SURPRISES adjust the refractive target based aim for a more myopic target, as it is Our ace in the hole with unexpected on calculations made with multiple much easier to fit a myopic lens to refractive results after cataract surgery formulas, and have a plan in place to correct . is the ability to perform a corneal address refractive surprises. n refractive surgery touchup. Patients 1. Godefrooij DA, de Wit GA, Uiterwaal CS, et al. Age-specific incidence and TORIC IOLS with keratoconus, unfortunately, can- prevalence of keratoconus: a nationwide registration study. Am J Ophthalmol. The traditional thinking has been to not undergo corneal without 2017;175:169-172. 2. Thebpatiphat N, Hammersmith KM, Rapuano CJ, et al. Cataract surgery in avoid using toric IOLs in keratoconic increasing the risk of further ectasia; keratoconus. Eye Contact Lens. 2007;33:244-246. eyes because they could increase the therefore, a refractive surprise in a 3. Watson MP, Anand S, Bhogal M, et al. Cataract surgery outcome in eye with keratoconus. Br J Ophthalmol. 2014;98:361-364. eyes’ already irregular astigmatism. patient with keratoconus may result in 4. Khandelwal SS, Montes de Oca I, Weikert MP, Wang L, Koch DD. Predictive However, the availability of CXL and the need for IOL exchange. accuracy of calculation formulas in eyes with keratoconus. Paper presented at: American Society of Cataract and Refractive Surgery topography-guided PRK may allow In one study of keratoconic eyes Annual Meeting; May 5-9, 2017; Los Angeles. more patients to receive toric IOLs at undergoing refractive lens exchange 5. Hashemi H, Heidarian S, Seyedian MA, et al. Evaluation of the results of using toric IOL in the cataract surgery of keratoconus patients. Eye Contact the time of cataract surgery. to correct associated with Lens. 2015;41:354-358. If the patient’s cornea is not keratoconus, 26% of keratoconic 6. Leccisotti A. Refractive lens exchange in keratoconus. J Cataract Refract Surg. changing, due either to progression or eyes had to have immediate IOL 2006;32:742-746. regression from recent CXL, and if the exchange, and 6% of eyes required a central 3 mm on his or her topography postoperative IOL exchange due to SUMITRA S. KHANDELWAL, MD shows regular astigmatism, one can refractive surprise.6 The author rec- n Assistant Professor of , Baylor consider use of a toric lens.5 The ommended use of an intraoperative College of Medicine, Cullen Eye Institute, Houston surgeon should explain to the patient handheld autorefractor to improve n Medical Director, Lions of Texas, Houston that this is an astigmatism-debulking refractive outcomes in these types n [email protected] procedure, rather than one that will of eyes. n Financial interest: None

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