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Going Under-the-Flap to Treat Early Ectasia with Hyperopic Refractive Error

In aircraft, flaps are a type of high-lift device used to increase the lift of an airplane wing. They provide the additional lift needed to get the aircraft off the ground. 

Just like an aircraft, patients want to get up and go following LASIK surgery. After the treatment, they expect to have improved vision and to be able to go back to their daily routine. They don’t want to be held down by postoperative complications. In this regard, surgeons need to help them find their flaps, so to speak.

While a recent systematic review of patient-reported outcome of satisfaction after LASIK concluded that majority of patients were satisfied with the result of their LASIK surgery1, a small subset of patients develop postoperative complications; some of which may have significant impacts on vision and quality of life.

Although rare, post-LASIK ectasia is a sight-threatening complication2 (occurring in 0.004 to 0.6% of post-LASIK patients), in which surgical weakening of the cornea induces thinning and an outward bulging. The bulging is a result of significant alterations in the mechanical structure of the cornea. The result is a cornea that cannot withhold intraocular pressure, and cone formation ensures. Functionally, patients may either experience a myopic or hyperopic shift in spherical equivalence.

In a bid to restore emmetropia in patients with post hyperopic LASIK ectasia, several treatment options have been tried, and there is a shifting interest in the field toward early treatment.3

Dr. Elias Jarade and his colleagues at the Beirut Eye Specialist Hospital in Lebanon have discovered a new way of working ‘under the flap’ to restore emmetropia and corneal stability in hyperopic post-LASIK ectasia. In a retrospective study, they assessed the safety, efficacy, and early results of a new combinational treatment for early corneal ectasia with hyperopic refractive error. Their findings were recently published in the Journal of Ophthalmology in a paper entitled “Under-the-Flap Crosslinking and LASIK in Early Ectasia with Hyperopic Refractive Error”.4

In this study, the authors included cases with early corneal ectasia plus a major hyperopic component of refractive error (hyperopia, hyperopic astigmatism, and mixed astigmatism), a good corrected distance visual acuity (CDVA), and a clear cornea in a relatively good condition. They also included patients with keratoconus, diagnosed by a combination of computed slit-scanning video-keratography of the anterior and posterior corneal surface, keratometric readings, and corneal pachymetry. A total of seven eyes of four consecutive patients (median age 21.5 years: all male) were included in the study. 

According to Dr. Jarade, “myopic refractive errors in early and moderated keratoconus cases are often addressed by combining photorefractive keratectomy (PRK) with corneal collagen crosslinking (CXL) or by intra-corneal ring segment implantation (ICRS), with or without CXL. These two treatment modalities are not applicable in case of hyperopic refractive errors (peripheral ablation with PRK often leads to regression and corneal scar, and ICRS leads to more hyperopic shift). As such, hyperopic refractive errors in keratoconus can solely be addressed either by eyeglasses-contact lenses or by phakic intraocular lens, which are not much desired in case of relatively low refractive errors and relatively shallow anterior chamber in hyperopic cases.”

The study results were remarkable. In all eyes treated, ectasia showed no progression over the follow-up period, which ranged from six to 15 months (mean 11.25 months), and uncorrected distance visual acuity (UDVA) improved substantially, changing significantly from 0.35 ± 0.18 logMAR to 0.05 ± 0.07 logMAR (p = 0.017), while CDVA remained relatively stable.

What are the major implications of this study within the current landscape of treating post-LASIK ectasia with hyperopic shifts? Dr. Jarade and colleagues proposed a novel approach toward treatment of mild to moderate hyperopic refractive errors in early stage of keratoconus. “Formerly, such a condition was only to be corrected with eyeglasses or contact lenses, often limiting the patient in his daily life – for example, certain occupations require the individual to be free of eyeglasses and contact lenses, and mainly, if the patient is intolerant to contact lenses.” 

What about the risks associated with keratectomy? Dr. Jarade noted: “Published clinical results of combining PRK+CXL have demonstrated that the early keratoconus cornea can tolerate a significant amount of central tissue ablation (often limited up to 50 to 60 microns) once combined with CXL.” In addition, he explained that under-the-flap CXL has been proven effective in maintaining corneal biomechanical stability in case of high myopic ablation. “Hence, combining femtolaser-assisted LASIK procedure with under-the-flap CXL seemed to be a safe approach to correct hyperopic refractive errors in early hyperopic keratoconus,” he stated. 

Femtosecond-assisted flap is more homogenous than the mechanical one and can attain a regular-thin flap in most cases. Estimate central stromal ablation after femto-flap creation is around 50 microns (similar to the amount of central tissue ablation in PRK+CXL), and hyperopic ablation is a peripheral one that does not affect the central stromal thickness.

Dr. Jarade added: “Our early results in combining femto-LASIK with under-the-flap CXL to treat hyperopic refractive errors in early keratoconus were very encouraging in terms of corneal bio-mechanical stability and achieving the target refraction. However, cases of epithelial ingrowth were encountered, which most likely were attributed to hyperopic ablation and extended time of flap lifting during the under-the-flap CXL procedure.”

Dr. Jarade provided some important tips for all surgeons who would like to use this technique. He advised them to “exclusively use femtosecond laser to create the flap in order to avoid any irregular flap cut and perhaps a thick area of flap thickness that would imply a deep stromal tissue cut”. He continued, stressing that “using the ‘accelerated’ CXL technique is perhaps better than the conventional method in order to avoid extended time of flap lift to minimize the risk of epithelial ingrowth”.

An alternative approach, according to Dr. Jarade, may include repositioning the flap after thorough irrigation of the interface then applying the UV light through the flap, to minimize the risk of epithelial ingrowth and possibly decrease the effectiveness of UV light at deeper tissue under the flap. Furthermore, for surgeons who are willing to adopt this technique, 

Dr. Jarade highlighted the importance of rigorously following the limitation of central ablation and flap thickness after confirming an appropriate patient inclusion criterion as mentioned in their method section. “We further advise to remain aware of the limitation of the follow-up time. Longer follow-up times will be published soon,” he noted.

As Dr. Jarade continues his work “under-the-flap”, he remains hopeful that this new technique will improve patient care in the future. “The key clinical implication of our study for patients with early keratoconus with hyperopic component is that, if long-term results remain promising, a surgical solution for their refractive error can be proposed, leading to excellent vision without any glasses or contact lenses,” he stated.

References:

1 Solomon KD, Fernández de Castro LE, Sandoval HP, et al. LASIK World Literature Review. Quality of Life and Patient Satisfaction. Ophthalmology. 2009;116(4):691-701.  

2 Bromley JG, Randleman JB. Treatment strategies for corneal ectasia. Curr Opin Ophthalmol. 2010;21(4):255-258. 

3 Kanellopoulos AJ, Binder PS. Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: The Athens protocol. J Refract Surg. 2011;27(5)323-331.  4 El-Khoury S, Abdelmassih Y, Amro M, Chelala E, Jarade E. Under-the-Flap Crosslinking and LASIK in Early Ectasia with Hyperopic Refractive Error. J Ophthalmol. 2018;15:4342984.

Elias MD

Dr. Elias F. Jarade, M.D.

Dr. Elias F. Jarade, M.D., is the director of the Corneal, External Disease, and Refractive Surgery Services at Beirut Eye Specialist Hospital. He is a graduate of the Lebanese University Medical School and carries two certificates of fellowship in cornea and refractive surgery from the Eye Center and Eye Foundation for Research, and The Massachusetts Eye and Ear Infirmary, Harvard Medical School. Dr. Jarade is heavily involved in the practice and research of cornea, cataract, refractive surgery for the past 15 years, with main interest in keratoconus. He has more than 50 peer-reviewed scientific papers and chapters. He is also a presenter and an invited faculty in the field of cornea and refractive surgery at international meetings, as well as board member for the Journal of Refractive Surgery, International Journal of Ophthalmology, and International Advisory Board for the Saudi Journal of Ophthalmology. Email: ejarade@yahoo.com.

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