CONSULTATION SECTION
1935
The editor mentioned the absence of other risk factors, such as age, RSB thickness, low refractive error, and preoperative corneal thickness. These factors are based on the concept that every LASIK procedure is performed using an average flap of 120 mm. Careful observation of the time-domain OCT image shows that the flap was thicker than 150 mm or more, with some areas reaching 192 mm. In general, people accept the idea that ectasia starts at a single point; however, the size of the area necessary to trigger biomechanical failure of the corneal structure is not known. I address these cases very aggressively once the diagnosis is made based on the fact that the natural course of ectasia after LASIK is not well established. If the patient retains good CDVA (20/30 or better), I would perform CXL using intrastromal loading of riboflavin at the interface level, preserving an intact epithelium. The LASIK flap is opened at the periphery, a pocket is created at the initial keratectomy cut plane, and the riboflavin is injected twice, 10 minutes apart, to fill in the pocket. After the patient is checked at the slitlamp, the ultraviolet (UV) light application starts at routine dosing. Reloading riboflavin is necessary at selected times depending on the potency of the UV light used. If the patient presents with reduced CDVA, I would perform combined implantation of a single ICRS implanted along the ectatic region and under the flap interface followed by CXL as described above (institutional review board–approved study protocol). Mauro Campos, MD S~ao Paulo, Brazil
planar flaps characteristic of femtosecond lasers. A mechanical microkeratome with an intended flap thickness of 130 mm was used in this case. The patient is contact lens intolerant; therefore, surgical options are appropriate to pursue. It would be important to carefully discuss and document realistic postoperative goals as well as nonsurgical and surgical options, which may include lamellar or full-thickness keratoplasty in the future. Because progression is already documented, the goals in this case are 2-fold; that is, to slow or halt the ectatic progression by biomechanically stabilizing the cornea and to attempt to visually rehabilitate the patient. To do this, we would recommend a combination of corneal CXL and limited topography-guided transepithelial PRK. Ideally, the Athens protocol would be used to sequentially perform a small optical zone topography ablation limited to 50 mm to debulk the irregular astigmatism. This would be followed by same-day sequential (epithelial-off [epi-off]) corneal CXL. Due to regulatory constraints, we would have to refer the patient outside the United States for this combined procedure. If this patient desired treatment in the US, we would offer corneal CXL alone following the Dresden epi-off protocol due to the aggressive nature of this case. Early reports of apical conductive keratoplasty combined with CXL have shown favorable results, and this patient would likely benefit from this combined procedure. George O. Waring IV, MD Charleston, South Carolina, USA F. Faria-Correia, MD Porto, Portugal
- Although ectasia can occur naturally, with a reported incidence of approximately 1 in 2000, this case of ectasia after LASIK is likely related to a thicker-than-intended nonplanar flap. The anterior and peripheral collagen lamella are major contributors to the biomechanical integrity of the cornea; therefore, a thick meniscus flap has a more profound biomechanical impact on the cornea than a thin planar flap. Although no obvious risk factors were present for the development of iatrogenic ectasia preoperatively, the postoperative OCT provides clues about the potential etiology of the ectasia development. Specifically, the OCT shows a thicker-than-intended flap and a semi-meniscus flap profile measuring 192 mm at the periphery. Furthermore, the RSB measures 274 mm, which may be due to a combination of ectatic thinning of the relatively weak posterior cornea in addition to the thicker-than-intended flap. Thick meniscus flaps are more likely to result from the use of older mechanical microkeratomes, in contradistinction to the thin
- Although we strive to identify preoperative risk factors for the development of post-LASIK ectasia, cases of ectasia have occurred in patients without preoperative risk factors who experienced intraoperative issues, such as the creation of a deeper-than-expected flap with a metal microkeratome, as occurred in this case. Metal microkeratomes have a labeled depth; however, studies have determined that there can be significant variability in flap thicknesses. Intraoperative measurement of the RSB after flap creation can be implemented to ensure the flap is not too thick before the excimer laser treatment is initiated.1,2 In this case, the LASIK flap was in all likelihood over 200 mm centrally at the time of surgery. The current finding of a central LASIK flap thickness of 177 mm is misleading because the epithelium over the ectatic central cornea typically thins considerably as the cornea begins to bulge forward with post-LASIK ectasia. Thankfully, this patient is eligible for treatment with epithelial-on (epi-on) corneal CXL, which will not only
J CATARACT REFRACT SURG - VOL 39, DECEMBER 2013
1936
CONSULTATION SECTION
stop the progression of the post-LASIK ectasia but will also often result in improved corneal shape and improved uncorrected distance visual acuity (UDVA) and CDVA (with spectacles). I would advise the patient to seek treatment with CXL at a local center in the very near future because post-LASIK ectasia is progressive in most cases and the patient has already lost CDVA. If the patient opted to seek treatment with me, I would enroll her in our ongoing epi-on CXL clinical trial. Although some peer-reviewed articles suggest that epi-on CXL is not effective, those studies had major flaws in their technique for riboflavin loading of the cornea, specifically failure to confirm by slitlamp observation that sufficient riboflavin was present in the cornea before proceeding to the UV-light treatment. After CXL, the patient would be expected to have mild improvement in corneal shape over the first 1 to 2 years and typically would have a 1- to 2-line improvement in UDVA and CDVA. In the years to come, the patient could opt for a variety of technologies to further improve her vision. Although the patient was reported to be contact lens intolerant, we have found that many patients with so-called contact lens intolerant keratoconus or postLASIK ectasia become comfortable and achieve excellent vision with scleral contact lenses. In addition to scleral lenses, the typical improvement in corneal shape can allow the patient to consider corneal reshaping procedures, such as topography-guided PRK. Of note: As the corneal shape improves after epi-on CXL, the amount of reshaping of the cornea is often less if performed 1 to 2 years postoperatively than if topography-guided PRK is performed as an initial procedure. In summary, intraoperative pachymetry is an important step to identify cases in which deeper-thanexpected flaps were created during LASIK. In addition, epi-on CXL performed soon after the diagnosis of post-LASIK ectasia can help minimize the severity of the condition and allow the patient to become eligible for future corneal-reshaping procedures. William Trattler, MD Miami, Florida, USA REFERENCES 1. Reinstein DZ, Srivannaboon S, Archer TJ, Silverman RH, Sutton H, Coleman DJ. Probability model of the inaccuracy of residual stromal thickness prediction to reduce the risk of ectasia after LASIK. Part II: quantifying population risk. J Refract Surg 2006; 22:861–870 2. Reinstein DZ, Srivannaboon S, Archer TJ, Silverman RH, Sutton H, Coleman DJ. Probability model of the inaccuracy of residual stromal thickness prediction to reduce the risk of ectasia after LASIK. Part I: quantifying individual risk. J Refract Surg 2006; 22:851–860
- Ectasia is the most feared complication after excimer laser surgery and is even more disconcerting when it happens after uneventful surgery in an apparently good candidate, as in this case. There was not enough information in the preoperative evaluation about the corneal tomography and aberrometry; it is crucial to analyze these data before any corneal refractive surgery is performed. The best way to approach this case would be to remodel the irregular shape of the cornea with ICRS implantation and 3 months later, after adequate corneal healing, perform corneal CXL to stabilize the progressive ectasia. Even though refractive stability after ICRS implantation has been reported in postLASIK ectasia,1,2 in this case the increased refractive error with a high astigmatic defect suggests the need for additional treatment with corneal CXL. I would not recommend PRK because of the anterior weakness of the cornea caused by the thick flap cut and the thin pachymetry shown on OCT. In addition, CXL will not be safe in a thinner cornea. I have seen progression of ectasia in post-LASIK eyes despite ICRS implantation. That is why I would suggest early CXL after diagnosing the ectasia. Some studies of CXL in secondary ectasia, such as the one by Poli et al.,3 report good corneal stabilization and safety. When post-LASIK ectasia is suspected, a close follow-up (every 4 to 6 months) should be performed with clinical and tomography examinations. If corneal steepening is seen on the topographic and tomographic maps and a decrease in the visual acuity is found, early corneal CXL should be performed. Traditionally, I have used rules to protect the eyes from ectasia after LASIK. They are to leave more than 250 mm in the RSB or to leave, after the ablation, more than one half CCT for the RSB. Pallikaris et al.4 published a retrospective study that found no post-LASIK ectasia in patients with an RSB greater than 325 mm and with refractive corrections less than 8.0 D. Nowadays, everybody is willing to leave the greatest RSB, preferably more than 300 mm. In this case, the risk factors for corneal ectasia could have been a thick corneal flap, a deep-volume ablation per diopter, and a relative low RSB. Claudia Blanco, MD Cali, Colombia REFERENCES 1. Kymionis GD, Tsiklis NS, Pallikaris AI, Kounis G, Diakonis VF, Astyrakakis N, Siganos CS. Long-term follow-up of Intacs for post-LASIK corneal ectasia. Ophthalmology 2006; 113:1909– 1917 JL, Vega-Estrada A, Baviera J, Beltra n J, Cobo2. Brenner LF, Alio Soriano R. Indications for intrastromal corneal ring segments in
J CATARACT REFRACT SURG - VOL 39, DECEMBER 2013
1935
The editor mentioned the absence of other risk factors, such as age, RSB thickness, low refractive error, and preoperative corneal thickness. These factors are based on the concept that every LASIK procedure is performed using an average flap of 120 mm. Careful observation of the time-domain OCT image shows that the flap was thicker than 150 mm or more, with some areas reaching 192 mm. In general, people accept the idea that ectasia starts at a single point; however, the size of the area necessary to trigger biomechanical failure of the corneal structure is not known. I address these cases very aggressively once the diagnosis is made based on the fact that the natural course of ectasia after LASIK is not well established. If the patient retains good CDVA (20/30 or better), I would perform CXL using intrastromal loading of riboflavin at the interface level, preserving an intact epithelium. The LASIK flap is opened at the periphery, a pocket is created at the initial keratectomy cut plane, and the riboflavin is injected twice, 10 minutes apart, to fill in the pocket. After the patient is checked at the slitlamp, the ultraviolet (UV) light application starts at routine dosing. Reloading riboflavin is necessary at selected times depending on the potency of the UV light used. If the patient presents with reduced CDVA, I would perform combined implantation of a single ICRS implanted along the ectatic region and under the flap interface followed by CXL as described above (institutional review board–approved study protocol). Mauro Campos, MD S~ao Paulo, Brazil
planar flaps characteristic of femtosecond lasers. A mechanical microkeratome with an intended flap thickness of 130 mm was used in this case. The patient is contact lens intolerant; therefore, surgical options are appropriate to pursue. It would be important to carefully discuss and document realistic postoperative goals as well as nonsurgical and surgical options, which may include lamellar or full-thickness keratoplasty in the future. Because progression is already documented, the goals in this case are 2-fold; that is, to slow or halt the ectatic progression by biomechanically stabilizing the cornea and to attempt to visually rehabilitate the patient. To do this, we would recommend a combination of corneal CXL and limited topography-guided transepithelial PRK. Ideally, the Athens protocol would be used to sequentially perform a small optical zone topography ablation limited to 50 mm to debulk the irregular astigmatism. This would be followed by same-day sequential (epithelial-off [epi-off]) corneal CXL. Due to regulatory constraints, we would have to refer the patient outside the United States for this combined procedure. If this patient desired treatment in the US, we would offer corneal CXL alone following the Dresden epi-off protocol due to the aggressive nature of this case. Early reports of apical conductive keratoplasty combined with CXL have shown favorable results, and this patient would likely benefit from this combined procedure. George O. Waring IV, MD Charleston, South Carolina, USA F. Faria-Correia, MD Porto, Portugal
- Although ectasia can occur naturally, with a reported incidence of approximately 1 in 2000, this case of ectasia after LASIK is likely related to a thicker-than-intended nonplanar flap. The anterior and peripheral collagen lamella are major contributors to the biomechanical integrity of the cornea; therefore, a thick meniscus flap has a more profound biomechanical impact on the cornea than a thin planar flap. Although no obvious risk factors were present for the development of iatrogenic ectasia preoperatively, the postoperative OCT provides clues about the potential etiology of the ectasia development. Specifically, the OCT shows a thicker-than-intended flap and a semi-meniscus flap profile measuring 192 mm at the periphery. Furthermore, the RSB measures 274 mm, which may be due to a combination of ectatic thinning of the relatively weak posterior cornea in addition to the thicker-than-intended flap. Thick meniscus flaps are more likely to result from the use of older mechanical microkeratomes, in contradistinction to the thin
- Although we strive to identify preoperative risk factors for the development of post-LASIK ectasia, cases of ectasia have occurred in patients without preoperative risk factors who experienced intraoperative issues, such as the creation of a deeper-than-expected flap with a metal microkeratome, as occurred in this case. Metal microkeratomes have a labeled depth; however, studies have determined that there can be significant variability in flap thicknesses. Intraoperative measurement of the RSB after flap creation can be implemented to ensure the flap is not too thick before the excimer laser treatment is initiated.1,2 In this case, the LASIK flap was in all likelihood over 200 mm centrally at the time of surgery. The current finding of a central LASIK flap thickness of 177 mm is misleading because the epithelium over the ectatic central cornea typically thins considerably as the cornea begins to bulge forward with post-LASIK ectasia. Thankfully, this patient is eligible for treatment with epithelial-on (epi-on) corneal CXL, which will not only
J CATARACT REFRACT SURG - VOL 39, DECEMBER 2013
1936
CONSULTATION SECTION
stop the progression of the post-LASIK ectasia but will also often result in improved corneal shape and improved uncorrected distance visual acuity (UDVA) and CDVA (with spectacles). I would advise the patient to seek treatment with CXL at a local center in the very near future because post-LASIK ectasia is progressive in most cases and the patient has already lost CDVA. If the patient opted to seek treatment with me, I would enroll her in our ongoing epi-on CXL clinical trial. Although some peer-reviewed articles suggest that epi-on CXL is not effective, those studies had major flaws in their technique for riboflavin loading of the cornea, specifically failure to confirm by slitlamp observation that sufficient riboflavin was present in the cornea before proceeding to the UV-light treatment. After CXL, the patient would be expected to have mild improvement in corneal shape over the first 1 to 2 years and typically would have a 1- to 2-line improvement in UDVA and CDVA. In the years to come, the patient could opt for a variety of technologies to further improve her vision. Although the patient was reported to be contact lens intolerant, we have found that many patients with so-called contact lens intolerant keratoconus or postLASIK ectasia become comfortable and achieve excellent vision with scleral contact lenses. In addition to scleral lenses, the typical improvement in corneal shape can allow the patient to consider corneal reshaping procedures, such as topography-guided PRK. Of note: As the corneal shape improves after epi-on CXL, the amount of reshaping of the cornea is often less if performed 1 to 2 years postoperatively than if topography-guided PRK is performed as an initial procedure. In summary, intraoperative pachymetry is an important step to identify cases in which deeper-thanexpected flaps were created during LASIK. In addition, epi-on CXL performed soon after the diagnosis of post-LASIK ectasia can help minimize the severity of the condition and allow the patient to become eligible for future corneal-reshaping procedures. William Trattler, MD Miami, Florida, USA REFERENCES 1. Reinstein DZ, Srivannaboon S, Archer TJ, Silverman RH, Sutton H, Coleman DJ. Probability model of the inaccuracy of residual stromal thickness prediction to reduce the risk of ectasia after LASIK. Part II: quantifying population risk. J Refract Surg 2006; 22:861–870 2. Reinstein DZ, Srivannaboon S, Archer TJ, Silverman RH, Sutton H, Coleman DJ. Probability model of the inaccuracy of residual stromal thickness prediction to reduce the risk of ectasia after LASIK. Part I: quantifying individual risk. J Refract Surg 2006; 22:851–860
- Ectasia is the most feared complication after excimer laser surgery and is even more disconcerting when it happens after uneventful surgery in an apparently good candidate, as in this case. There was not enough information in the preoperative evaluation about the corneal tomography and aberrometry; it is crucial to analyze these data before any corneal refractive surgery is performed. The best way to approach this case would be to remodel the irregular shape of the cornea with ICRS implantation and 3 months later, after adequate corneal healing, perform corneal CXL to stabilize the progressive ectasia. Even though refractive stability after ICRS implantation has been reported in postLASIK ectasia,1,2 in this case the increased refractive error with a high astigmatic defect suggests the need for additional treatment with corneal CXL. I would not recommend PRK because of the anterior weakness of the cornea caused by the thick flap cut and the thin pachymetry shown on OCT. In addition, CXL will not be safe in a thinner cornea. I have seen progression of ectasia in post-LASIK eyes despite ICRS implantation. That is why I would suggest early CXL after diagnosing the ectasia. Some studies of CXL in secondary ectasia, such as the one by Poli et al.,3 report good corneal stabilization and safety. When post-LASIK ectasia is suspected, a close follow-up (every 4 to 6 months) should be performed with clinical and tomography examinations. If corneal steepening is seen on the topographic and tomographic maps and a decrease in the visual acuity is found, early corneal CXL should be performed. Traditionally, I have used rules to protect the eyes from ectasia after LASIK. They are to leave more than 250 mm in the RSB or to leave, after the ablation, more than one half CCT for the RSB. Pallikaris et al.4 published a retrospective study that found no post-LASIK ectasia in patients with an RSB greater than 325 mm and with refractive corrections less than 8.0 D. Nowadays, everybody is willing to leave the greatest RSB, preferably more than 300 mm. In this case, the risk factors for corneal ectasia could have been a thick corneal flap, a deep-volume ablation per diopter, and a relative low RSB. Claudia Blanco, MD Cali, Colombia REFERENCES 1. Kymionis GD, Tsiklis NS, Pallikaris AI, Kounis G, Diakonis VF, Astyrakakis N, Siganos CS. Long-term follow-up of Intacs for post-LASIK corneal ectasia. Ophthalmology 2006; 113:1909– 1917 JL, Vega-Estrada A, Baviera J, Beltra n J, Cobo2. Brenner LF, Alio Soriano R. Indications for intrastromal corneal ring segments in
J CATARACT REFRACT SURG - VOL 39, DECEMBER 2013
