EWAP JUNE 2022 3 EDITORIAL Graham Barrett Chief Medical Editor EyeWorld Asia-Pacific • China • Korea • India EyeWorld Asia-Pacific • June 2022 • Vol. 18 No. 2 In this issue, several contributors address the various reasons for patient dissatisfaction after cataract and implant surgery. Dry eye, dysphotopsia, and reduced contrast due to multifocals are not uncommon but perhaps not as frequent as missed refractive targets. IOL “misses” can be turned into “hits” prior to cataract surgery and selection of lens power during preoperative counseling. With modern IOL formulas, well over 80% of patients are within 0.5 D of predicted power; errors over 0.75 D are quite rare. But regardless of one’s confidence in one’s refractive prediction, it is always wise to counsel patients regarding the risks and limitations of surgery to explain that perfect prediction is not always achievable; although unlikely, spectacles may be required. Similarly, I recommend topography or tomography as well as OCT as essential to preoperative biometry. It is important to identify an irregular cornea which may not be apparent on slit lamp examination. The patient can then be counseled on the possible impact on prediction and increased likelihood of spectacle correction. Patients with extremely short axial lengths should similarly be counselled. Optimizing the corneal surface prior to measurements is another important component. Traditionally, errors in axial length were the most common contributor to refractive surprises. Modern swept-source biometers make this less likely; corneal power estimation errors are now more likely to cause surprises. The use of multiple instruments and methods to obtain a median corneal power prediction can be helpful for toric and spherical power prediction. Postoperative residual astigmatism can be minimized by careful selection of toric lens power as well as care in achieving accurate alignment. If an error occurs, the outcome in the second eye can be improved by taking the first eye’s error into account. It is important to exclude other factors such as residual viscoelastic or measurement errors by repeating biometry and refraction. Having excluded these factors, the refractive prediction can be adjusted by considering the prediction error in the first eye. The adjustment coefficient depends on the IOL formula. For traditional formulas, a value of 0.5 is appropriate, whereas for more modern formulas such as the Barrett Universal, a more modest adjustment coefficient of 0.3 is sufficient; 0.3 times the error in prediction is added to the predicted refraction of the second eye. The most accurate method of correcting an unexpected refractive error is with either PRK or LASIK. Lens options include rotation of the toric lens, a piggyback lens, and exchange. The latter is often preferred for large refractive errors though often simple rotation of a toric IOL is sufficient. The Rx formula available on the APACRS website provides solutions for all three options. An important note is that the Rx formula requires the preoperative phakic anterior chamber depth (ACD) and not the post-surgery ACD. The adjustable IOL not currently widely used in the Asia-Pacific region provides another option. I hope that the suggestions contained in this issue help in preventing and managing unexpected outcomes in your practice.
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