New options for therapeutic refractive surgery

Refractive surgery (RS) has undergone a tremendous evolution over the last 40 years. Modern RS started in the late 70s, developed in the 80s and 90s, and reached maturity in the last 10 years due to the evidence supporting the use of new treatment modalities such as excimer laser surgery, custom-guided excimer laser surgery, and femtosecond lenticular intrastromal lamellar surgery Small incision lenticular excimer laser surgery (SMILE) and the evidence in favor of phakic intraocular lenses (IOLs), particularly posterior chamber ones. Having said that, today, we have a tremendous body of evidence in favor of RS as a way to improve the quality of life by improving quality of vision in patients affected by refractive errors, which is a therapeutic indication of refractive surgical procedures. However, not so much has been mentioned about the use of RS to improve visual functional diseases, that is, therapeutic RS.

While conventional RS aims to eliminate the need for glasses for the patient and, in doing so, improve the quality of life and visual function in the patient affected by refractive errors of diverse types, therapeutic use of refractive surgical tools involves their use to improve vision (monocular and binocular) in refractive disabled eyes. Such disabilities can happen due to previous corneal surgery (especially corneal graft), medical corneal problems (infectious keratitis), genetic-related diseases (keratoconus), anisometropia, amblyopia, and problems related to previous cataract surgery (aniseiconic refractive surprises). In all these cases the problems are bad quality of vision, inadequate refreactive error leading to problems in binocularity, not correctable by regular spectacles, while contact lenses are not always well accepted or even tolerated in many cases and the need to take the benefit of complex and costly procedures such as corneal graft, that end, especially in disea ses such as keratoconus, with unpredictable refractive outcomes.

Corneal RS (excimer or lenticular femtosecond surgery) has increased in popularity due to its precision, cost-effectiveness, and low frequency and severity of its complications.[1] Its use on a therapeutic basis is totally justified for treating refractive errors. However, it has limitations such as the presence of a significant amount of corneal irregularity and the consequent higher-order aberrations (only customized wavefront-guided treatment can correct them, and this is not available for lenticular femtosecond surgery),[2] while the upper limits of corneal RS are debatable. For many of us, this is up to 8 D in myopes, while for many others, it is a much lower amount in myopia and hyperopia and astigmatism. When this happens, the opportunity for phakic IOLs, adequately designed and well planned and indicated,[3,4,5] plays a role, especially in anisometropic amblyopia, where they may achieve spectacular results.[6]

Nowadays, we are in a moment in which custom-guided corneal RS is performed on a regular basis and with adequate software in particular laser platforms such as the Amaris Schwind, in which lenticular surgery is progressing toward the correction of higher levels of refraction and even corneal irregularity.[2] Phakic lenses have a well-defined role in high refractive errors and also in those intermediate ones in which the association of high astigmatism and spherical refraction makes corneal RS unpredictable or not indicated.

New phakic posterior chamber lenses[3,5] offer this opportunity as they have already undergone the test of time and have an adequate risk/benefit ratio since the development of implementations such as the central hole to prevent the problems created by low and high vault and sizing with more predictable outcomes. However, the use of phakic lenses in therapeutic RS is still limited by the lack of consistent evidence. Emerging clinical data favors the use of new lens designs such as the EyeCryl Biotech,[3,4,6] with customized dimensions, vault prediction, and a particular design in the haptic tips that support the lens to the sulcus thanks to a hinge that makes four points of fixation guaranteed, making this lens ideal for the correction of anisometropic outcomes that damage binocularity, especially following corneal graft or keratoconus.[7] In keratoconus, especially when the stability of the disease is obtained following crosslinking and other associated therapies such as intracorneal ring segments, customized corneal surface excimer laser surgery may further improve the vision, but only in small refractive residual errors.[2,3,4,5,6,7] When using phakic IOLs in keratoconus, the rotational stability of the phakic toric lens in keratoconus and keratoconus-related surgeries is mandatory as the correction of high cylinders might be very negatively affected by rotational instability induced by the lens.[8]

At this moment, thanks to the development of the industry, we have new opportunities for our patients with a poor or inadequate indication for corneal RS and who have aniseikonia, anisometropia, and an impossible binocularity, especially following keratoconus and keratoconus-related therapies. These technologies are welcomed and indeed need to expedite the adequate clinical results to establish their role and indication in the benefit of the many patients affected by corneal disease and particularly keratoconus.

About the author —

Prof. Dr. Jorge Alio MD, PhD, FEBO, FWCRS is Professor and Chairman of Ophthalmology, University Miguel Hernandez, Alicante, Spain, founder of Vissum Miranza, Alicante, Spain and the Jorge Alió Foundation for the Prevention of Blindness. His main research interests include lens, refractive and corneal surgery. Pioneer in the area of multifocal, accommodative and toric IOLs, excimer laser refractive surgery, phakic IOLs and more recently corneal regeneration surgery. Author of over 777 peer review papers in indexed journals, 431 chapters, 97 books and over 2861 communications in international congresses. 2024 Hirsch factor (h-factor) of 77 (Scopus). LXIII chair of the Academia Ophthalmologica Internationalis, XLIX chair of the European Academy of Ophthalmology, President of the ISRS/AAO (2006-2008) member of the American Ophthalmological Society, he has been member of the Board of the European Society of Cataract and Refractive Surgeons and has received over 103 international and national awards. He is the creator and Director of the online International Specialization Course in Refractive, Cornea and Lens Surgery (University Miguel Hernandez). Fellows from all over the world come to his research facilities to be trained under his supervision.