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RSB thickness safety limit is 300 mm. Female patients should be carefully selected for refractive surgery because should they become pregnant in the future, it could trigger post-LASIK corneal ectasia. The corneal refraction procedure that seems more suitable for the current refractive case is PRK. The high manifest refraction of the patient could contribute to intraoperative and postoperative complications (eg, myopic regression, corneal haze, overtreatment, and undertreatment). These are difficult to address in cases involving a very thin post-PRK cornea; the post-PRK residual stromal thickness should be at least 300 mm because if it were thinner, the options for retreatment would be limited. Alternatively, with this type of case I might take an intraocular treatment approach. Refractive lens exchange (using a toric IOL) could not be a solution for a myopic patient of this age because the risk for retinal detachment is high. Another possible solution is implantation of a pIOL in the posterior chamber, which has the advantage of maintaining accommodation. In the current case, the patient is not tolerating spectacles and the ACD measurements indicate that a posterior chamber pIOL (correcting myopia and astigmatism) could be implanted safely. However, the possibility of early cataract formation and the need for repeating surgery for pIOL extraction and cataract in the near future (in a 38-year-old patient) should be considered. In conclusion, in the current case I would prefer not to perform refractive surgery. The proper contact lens use seems the most preferable decision for this patient because of her age, the thin corneas, and the high attempted correction. If the patient remained highly motivated for refractive surgery, I would probably refer her to another refractive surgeon. George D. Kymionis, MD, PhD Heraklion, Crete, Greece

REFERENCES 1. Elsheikh A, Wang D, Brown M, Rama P, Campanelli M, Pye D. Assessment of corneal biomechanical properties and their variation with age. Curr Eye Res 2007; 32:11–19  JL, Vega-Estrada A, Baviera J, Beltra n J, Cobo2. Brenner LF, Alio Soriano R. Clinical grading of post-LASIK ectasia related to visual limitation and predictive factors for vision loss. J Cataract Refract Surg 2012; 38:1817–1826

- In my opinion, the best option in this case is implantation of a toric pIOL. The cornea is thin and has no existing or suspected keratoconus or other corneal ectasia, as supported by the topography, tomography, and OCT examinations. When the CCT is less than 500 mm, I

always perform PRK instead of LASIK, even when using a femtosecond laser to create a predictably thin flap. Moreover, I do not perform laser treatment if the CCT is less than 450 mm. To keep the post-LASIK risk low, I require an RSB of at least 300 mm (not 250 mm) and a total corneal thickness of at least 400 mm. I would not perform laser treatment in this case because the measurements are outside those requirements. For patients 21 to 50 years old, my inclination is to use pIOLs instead of RLE because of the increased risk for retinal damage or retinal detachment. For patients older than 50 years, I am inclined to replace the lens, and in some cases involving high myopia, monovision is a good alternative to multifocal IOLs. In this case, the ACD in the right eye is 3.38 mm and in the left eye is 3.41 mm. Both eyes are over the 3.0 mm requirement to implant safely an iris-fixated or posterior chamber pIOL. Another important condition for pIOL implantation is an endothelial cell count (ECC) of over 2000 cells/mm2; thus, an ECC should be performed before making the final decision in this case. Miguel Srur, MD Santiago, Chile EDITOR’S COMMENT This is an interesting, well-documented case that presents a thin cornea but normal results from other examinations performed using different technologies, including symmetric bow-tie pattern WTR Placido topography with normal regional relative thickness profiles obtained with tomography.1 Based on the data, some surgeons consider that this could be a normal thin cornea or a sign of pre-topographic ectatic disease. Many also consider that even if it is normal, a cornea this thin is very close to a higher risk level for the percentage of tissue altered, which has been shown to be a robust risk factor for post-LASIK ectasia.2–4 All respondents note that the risk factorsda potentially high percentage of tissue altered and a cornea more than 3 standard deviations thinner the normaldare enough to preclude LASIK, even with the more predictable flaps with modern microkeratomes and femtosecond lasers. Some respondents consider surface ablation a reasonable option, especially considering the patient's age. If the patient were younger than 30 years, even surface ablation might not be an option because this patient could still present some topographic signs of an ectatic disease.1 Other approaches discussed include small-incision lenticule extraction,5 which theoretically has less biomechanical impact, and a toric posterior

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chamber pIOL,6 which would preserve the eye's accommodation and possibly correct the myopia and astigmatism. The possibility of counseling for no surgery at all was also raised in consideration of the patient's prepresbyopic age of 38 years. In this type of case, all of the preoperative examination results and patient demographic data, including age, should be interpreted together to determine the corneal thickness and safe limits the surgeon will consider for the patient. Although a variety of options are considered here, a large majority of the respondents, including me, agree that the best approach is one that only minimally changes the anterior surface or does not involve the anterior cornea at all, such as with small-incision lenticule extraction or pIOL implantation.

Marcony R. Santhiago, MD, PhD Rio de Janiero, Brazil REFERENCES 1. Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology 2008; 115:37–50

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2. Santhiago MR, Smadja D, Gomes BF, Mello GR, Monteiro ML, Wilson SE, Randleman BJ. Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography. Am J Ophthalmol 2014; 158:87–95 3. Santhiago MR, Smadja D, Wilson SE, Krueger RR, Monteiro ML, Randleman JB. Role of percent tissue altered on ectasia after LASIK in eyes with suspicious topography. J Refract Surg 2015; 31:258–265 4. Santhiago MR, Wilson SE, Hallahan KM, Smadja D, Lin M, Ambrosio R Jr, Singh V, Roy AS, Dupps WJ Jr. Changes in custom biomechanical variables after femtosecond laser in situ keratomileusis and photorefractive keratectomy for myopia. J Cataract Refract Surg 2014; 40:918–928 5. Reinstein DZ, Archer TJ, Randleman JB. Mathematical model to compare the relative tensile strength of the cornea after PRK, LASIK, and small incision lenticule extraction. J Refract Surg 2013; 29:454–460. Available at: http:// www.choeye.co.kr/webi_board/upFile/mathematical_model_ to_compare_the_reletive_tensile_strength_of_the_cornea_ after_PRK_Lasik_Smile.pdf. Accessed May 13, 2015 6. Huang D, Schallhorn SC, Sugar A, Farjo AA, Majmudar PA, Trattler WB, Tanzer DJ. Phakic intraocular lens implantation for the correction of myopia; a report by the American Academy of Ophthalmology (Ophthalmic Technology Assessment). Ophthalmology 2009; 116:2244–2258. Available at: http://www.brightonvisioncenter.com/Research/Phakic_IOL s_for_Correction_of_Myopia_2009.pdf. Accessed May 13, 2015

J CATARACT REFRACT SURG - VOL 41, JUNE 2015

June consultation #7.

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