1934
CONSULTATION SECTION
What would be the best way to approach this case? Would it be best to simply observe? Or would you perform corneal collagen crosslinking (CXL) only, CXL associated with topography-guided photorefractive keratectomy (PRK) or intrastromal corneal ring segment (ICRS) implantation, or ICRS implantation alone. Would you approach this patient at the time of the diagnosis of ectasia or wait for documented progression? What is the role of the percentage of tissue altered (combination of the flap thickness and the amount of tissue ablated) in the ectasia, which occurred despite normal preoperative parameters? - Despite the low risk for corneal ectasia, which would have indicated the preoperative parameters for this patient, the postoperative flap thickness of 177 mm in the right eye (which was probably thicker when created because there is prolonged flap thinning with time) should be considered the main reason for the post-LASIK corneal ectasia. At the time of the referral examination, the patient reported progressive decreased visual acuity in the right eye after LASIK. In addition, the refraction data 1 month, 3 years, and 7 years postoperatively show an increase in astigmatism and indicate progression of the corneal ectasia. The patient does not tolerate contact lenses, which is crucial when deciding how to proceed, and the CDVA in the right eye is 20/50 1. The corneal thickness at the thinnest point in the right eye (458 mm) is too thin to decrease the corneal irregularity with combined topographyguided PRK followed by CXL. Based on the above, I would consider combined ICRS implantation and corneal CXL in a 2-step procedure. I would prefer to perform ICRS implantation first to reshape the cornea and improve the patient's refraction and visual acuity, mainly the CDVA. Combined topography-guided PRK followed by CXL could not be a first option because of the patient's high ametropia, corneal irregularity, contact lens intolerance, and thin cornea. The patient data after ICRS implantation would define the next step of my approach. I would not proceed to CXL treatment immediately; the patient is 48 years old, so there is a possibility that ICRS would eliminate the progression of the corneal ectasia. Rather, I would prefer to closely evaluate the patient and proceed to CXL (combined transepithelial phototherapeutic keratectomy during CXL; Cretan protocol1) 6 months after ICRS implantation unless there were documented progression of the corneal ectatic disorder during this 6-month period. The main goal of these approaches (ICRS with or without adjuvant
CXL) would be stabilization of the corneal ectasia and improvement in the CDVA because the patient does not tolerate contact lenses. When the corneal ectatic disorder stabilizes (with or without adjuvant CXL) and the corneal irregularity and CDVA improve, implantation of a phakic or pseudophakic toric intraocular lens (IOL) could be another adjuvant treatment option to correct patient's refractive error given the patient's contact lens intolerance and spectacle intolerance due to anisometropia. Some may say that all these interventions are not needed; however, I prefer them over corneal transplantation (even deep anterior lamellar keratoplasty). Finally, although the data given for the patient's left eye are limited and it seems as though there was no corneal ectasia at the time of the examination, I would closely observe the left eye and recommend the patient for close evaluation in the future. George D. Kymionis, MD, PhD Heraklion, Crete, Greece REFERENCE 1. Kymionis GD, Grentzelos MA, Kounis GA, Diakonis VF, Limnopoulou AN, Panagopoulou SI. Combined transepithelial phototherapeutic keratectomy and corneal collagen cross-linking for progressive keratoconus. Ophthalmology 2012; 119:1777– 1784
- This clinical case presents several considerations that should be based on careful literature analysis. First is the topography map. As we know, the relationship among all structural components of the cornea and tear-film coating influence the Placido image obtained from every eye examined. Placido-based topographic evaluation of the cornea has been used for decades with great success to select refractive surgery candidates. However, this examination does not entirely reflect material performance, such as the resistance for intraocular pressure, lid apposition, and eye rubbing. Considering this, when one uses a Placido instrument for screening, it is better to be mistaken by a false-positive diagnosis of high-risk corneas than the opposite. We train our residents and fellows to learn axial topographic maps based not only on a 0.5 D scale but also to look for corneal asphericity with extra care. In the case presented, the 1.5 D scale was used and masks the increased asphericity this patient appears to have. Also, the front surface presents a significant amount of astigmatism that did not appear in the clinical refraction. The absence of the map from the left eye decreases the chance of detecting risk factors for refractive surgery in this patient. I would feel much more comfortable performing surgery in patients with similar images of both eyes.
J CATARACT REFRACT SURG - VOL 39, DECEMBER 2013
CONSULTATION SECTION
What would be the best way to approach this case? Would it be best to simply observe? Or would you perform corneal collagen crosslinking (CXL) only, CXL associated with topography-guided photorefractive keratectomy (PRK) or intrastromal corneal ring segment (ICRS) implantation, or ICRS implantation alone. Would you approach this patient at the time of the diagnosis of ectasia or wait for documented progression? What is the role of the percentage of tissue altered (combination of the flap thickness and the amount of tissue ablated) in the ectasia, which occurred despite normal preoperative parameters? - Despite the low risk for corneal ectasia, which would have indicated the preoperative parameters for this patient, the postoperative flap thickness of 177 mm in the right eye (which was probably thicker when created because there is prolonged flap thinning with time) should be considered the main reason for the post-LASIK corneal ectasia. At the time of the referral examination, the patient reported progressive decreased visual acuity in the right eye after LASIK. In addition, the refraction data 1 month, 3 years, and 7 years postoperatively show an increase in astigmatism and indicate progression of the corneal ectasia. The patient does not tolerate contact lenses, which is crucial when deciding how to proceed, and the CDVA in the right eye is 20/50 1. The corneal thickness at the thinnest point in the right eye (458 mm) is too thin to decrease the corneal irregularity with combined topographyguided PRK followed by CXL. Based on the above, I would consider combined ICRS implantation and corneal CXL in a 2-step procedure. I would prefer to perform ICRS implantation first to reshape the cornea and improve the patient's refraction and visual acuity, mainly the CDVA. Combined topography-guided PRK followed by CXL could not be a first option because of the patient's high ametropia, corneal irregularity, contact lens intolerance, and thin cornea. The patient data after ICRS implantation would define the next step of my approach. I would not proceed to CXL treatment immediately; the patient is 48 years old, so there is a possibility that ICRS would eliminate the progression of the corneal ectasia. Rather, I would prefer to closely evaluate the patient and proceed to CXL (combined transepithelial phototherapeutic keratectomy during CXL; Cretan protocol1) 6 months after ICRS implantation unless there were documented progression of the corneal ectatic disorder during this 6-month period. The main goal of these approaches (ICRS with or without adjuvant
CXL) would be stabilization of the corneal ectasia and improvement in the CDVA because the patient does not tolerate contact lenses. When the corneal ectatic disorder stabilizes (with or without adjuvant CXL) and the corneal irregularity and CDVA improve, implantation of a phakic or pseudophakic toric intraocular lens (IOL) could be another adjuvant treatment option to correct patient's refractive error given the patient's contact lens intolerance and spectacle intolerance due to anisometropia. Some may say that all these interventions are not needed; however, I prefer them over corneal transplantation (even deep anterior lamellar keratoplasty). Finally, although the data given for the patient's left eye are limited and it seems as though there was no corneal ectasia at the time of the examination, I would closely observe the left eye and recommend the patient for close evaluation in the future. George D. Kymionis, MD, PhD Heraklion, Crete, Greece REFERENCE 1. Kymionis GD, Grentzelos MA, Kounis GA, Diakonis VF, Limnopoulou AN, Panagopoulou SI. Combined transepithelial phototherapeutic keratectomy and corneal collagen cross-linking for progressive keratoconus. Ophthalmology 2012; 119:1777– 1784
- This clinical case presents several considerations that should be based on careful literature analysis. First is the topography map. As we know, the relationship among all structural components of the cornea and tear-film coating influence the Placido image obtained from every eye examined. Placido-based topographic evaluation of the cornea has been used for decades with great success to select refractive surgery candidates. However, this examination does not entirely reflect material performance, such as the resistance for intraocular pressure, lid apposition, and eye rubbing. Considering this, when one uses a Placido instrument for screening, it is better to be mistaken by a false-positive diagnosis of high-risk corneas than the opposite. We train our residents and fellows to learn axial topographic maps based not only on a 0.5 D scale but also to look for corneal asphericity with extra care. In the case presented, the 1.5 D scale was used and masks the increased asphericity this patient appears to have. Also, the front surface presents a significant amount of astigmatism that did not appear in the clinical refraction. The absence of the map from the left eye decreases the chance of detecting risk factors for refractive surgery in this patient. I would feel much more comfortable performing surgery in patients with similar images of both eyes.
J CATARACT REFRACT SURG - VOL 39, DECEMBER 2013
