The future of corneal refractive surgery took center stage on Day 3 of the 42nd Congress of the European Society of Cataract and Refractive Surgeons (ESCRS 2024), at the highly anticipated Main Symposium.
From advances in AI for keratoconus diagnosis and treatment to evolving surgical nomenclature and cutting-edge PresbyLASIK techniques, top experts from around the world discussed the latest breakthroughs shaping the field. The session also previewed upcoming ESCRS guidelines that promise to enhance both safety and efficacy in refractive surgery, offering a comprehensive roadmap for surgeons worldwide.
AI for keratoconus
Although better known for its application in the posterior segment, AI is now making waves in the corneal refractive surgery arena, particularly for diagnosing keratoconus. “The corneal biomechanics may have been abnormal and we can miss it,” said Prof. Dimitri Azar (USA). “So an AI program can easily look at images and give us a better idea.”
Beyond diagnosis, convolutional neural networks (CNN) are also transforming keratoconus treatment. According to Prof. Azar, AI has demonstrated its ability to predict onset of keratoconus, forecast the need for surgery, and reduce the risk of postoperative ectasia after keratorefractive surgery. And in cases requiring collagen cross-linking (CXL), AI can predict keratoconus progression and optimize outcomes postoperatively.
However, Prof. Azar also cautioned that bias in data collection and algorithm design could pose significant risks, stressing the need for careful oversight. “If you start human learning as biased, that bias will be easily transmitted to machine learning programs,” he warned.
The lenticule era
According to Assoc. Prof. Mario Nubile (Italy), it’s important to evolve terminology to better define the procedure. “We should use one term as we do for PRK and LASIK,” he reasoned. “Each company tends to use their own names—small incision lenticule extraction, corneal lenticule extraction, advanced refractive correction… we should use a name to describe the entire family of procedures.”
The updated nomenclature he is referring to is keratorefractive lenticule extraction (KLEx). The new name now addresses the tissue altered (the cornea), the purpose of the alteration (refractive) and the mechanism of alteration (lenticule extraction).
This shift in language sets the stage for cutting-edge technologies, like the new SMILE® Pro, powered by the VIsuMax® 800 (Carl Zeiss Meditec; Jena, Germany) femtosecond laser system. The VisuMax 800 stands out for its reduced laser sculpting time—carving a SMILE lenticule in a mere 10 seconds—thanks to its high 2 MHz laser impulse repetition rate. “It’s very fast, so you minimize the risk for suction loss,” said Assoc. Prof. Nubile, noting another benefit to the system.
Beyond efficiency, he discussed the future of hyperopia correction with KLEx, noting the success of a 12-month multicenter study where 81% of eyes treated were within ± 0.50D of the target refraction.1
Assoc. Prof. Nubile also delved into the promising advancements in lenticule banking, where extracted tissue can be cryopreserved for future use or donated for therapeutic applications. This offers a glimpse into a new era of personalized corneal care, allowing patients the potential to reverse conditions like post-SMILE ectasia by re-implanting their stored lenticule.
Assoc. Prof. Nubile ended his session by emphasizing that additive options, including allogenic lenticule implantation for hyperopia and ectasia, represent the forefront of bioengineering and KLEx innovation. “The lenticule era has just started and we have much more to see in the future,” he concluded.
Biomechanics and customized CXL
Why is assessing corneal biomechanics a must in corneal refractive surgery? In his lecture, Dr. Ingemar Gustafsson (Sweden) emphasized that doing so is critical to avoid undertreatment or overtreatment, ensuring that patients receive the most effective, personalized interventions.
To support his stance, Dr. Gustafsson unleashed a flurry of customized CXL (cCXL) studies which have shown remarkable results, especially in strengthening the biomechanical properties of the ectatic zone. This focal treatment not only leads to overall corneal regularization but also enhances stromal clarity and improves the epithelial profile, contributing to objective and subjective visual outcomes for patients.2-6
Dr. Gustafsson also noted that the localized approach of cCXL also results in less nerve damage, which could translate into faster epithelial healing and potentially fewer cases of dry eye.
Looking ahead, Dr. Gustafsson called for future studies to focus on identifying the specific biomechanical characteristics that determine a patient’s risk for ectasia. He also emphasized the need for developing technique-specific and patient-tailored cCXL protocols, aiming to create even more personalized and effective treatment options.
Epithelial law and rules
Reinstein’s Law of Epithelial Compensation states that irregular astigmatism results in irregular epithelium,” which means that when an eye presents with stable irregular topography, the epithelium has already maxed out its compensatory function.
Expanding on this, Prof. Dan Z. Reinstein (United Kingdom) emphasized that corneal topography can be misleading. “Show me the epithelium!” he demanded instead, a play on the familiar Jerry Maguire quote. He then urged ophthalmologists to “keep calm and measure the epithelium,” highlighting the importance of anatomical diagnosis over surface-level metrics.
Prof. Reinstein proceeded to review several OCT devices—such as the Avanti (Optovue; CA, USA), Cirrus 5000 (Carl Zeiss Meditec; Jena, Germany), and MS-39 (CSO; Florence, Italy)—that are capable of capturing detailed epithelial measurements, which offer more precise insights than keratometry, particularly post-surgery.
Prof. Reinstein ended his lecture by introducing his “Four Rules of Epithelial Healing,” noting that (1) the epithelium thickens to fill depressions and (2) thins over peaks, with (3) changes proportional to stromal alterations. And (4) that the amount is defined by the rate of curvature change.
PresbyLASIK
Presbyopia is a critical issue that has a profound impact on patients’ quality of life—comparable to chronic conditions like hypertension. As one of the leading reasons patients seek refractive surgery today, presbyopia correction techniques have become a focal point in refractive advancements.
Dr. Jaime Aramberri’ (Spain), during his lecture, centered on PresbyLASIK, a compelling solution for correcting ametropia and presbyopia in patients aged 40 to 60. “PresbyLASIK can be defined as the LASIK technique that applies a multifocal or little profile to the cornea in order to achieve an increased depth of field,” he explained.
“It’s a quick surgery under topical anesthesia, and it’s a quick recovery,” Dr. Aramberri noted. “And very importantly, it preserves the lens for future surgeries.”
He then outlined two main strategies. The first, called central PresbyLASIK, adds more power to the central cornea. The counterpart is the peripheral PresbyLASIK, giving more power to the annular area in the mid-periphery.
Dr. Aramberri prefers central PresbyLASIK because it works better. “There is a synergic effect. The central cornea’s higher power, plus its induced spherical aberration and the small aperture… they all play in favor of good near vision,” he explained. But, Dr. Aramberri found that he could only extend the depth of focus up to a certain limit before there was a decrease in vision quality.
Like other platforms, he came up with the same conclusion: to use micro-monovision, where the dominant eye (DE) is corrected for distance vision and the non-dominant eye (NDE) for near vision. This approach aims to balance the patient’s ability to see clearly across various ranges.
However, Dr. Aramberri cautioned that there are notable differences in the accuracy and safety of this technique across different surgical platforms, with surgeons often facing a learning curve. Additionally, while most patients experience significant improvement, some regression of near-vision effects can occur over time, necessitating possible further interventions.7
Despite these challenges, postoperative surveys indicate a high level of patient satisfaction with PresbyLASIK outcomes. Many patients report being able to regain a fuller range of vision without the need for reading glasses, a factor that significantly enhances their day-to-day lives.8
ESCRS guidelines
To close out the symposium, Prof. Jesper Hjortdal (Denmark) provided an in-depth overview of the upcoming ESCRS guidelines on cataract and refractive surgery. Aimed at enhancing patient safety and optimizing surgical outcomes, these recommendations are being developed with a rigorous approach to ensure they address the most critical aspects of cataract and refractive surgery.
Prof. Hjortdal explained that the guidelines are grounded in the PICO methodology—Patient, Investigated Condition, Comparison and Outcome. This approach allows for a comprehensive evaluation of patient safety, surgical efficacy and predictability, offering a structured framework for decision-making.
Among the key areas the guidelines will cover are the absolute and relative contraindications for corneal refractive surgery, ensuring that only suitable patients undergo these procedures. Prof. Hjortdal also stressed the importance of detailed preoperative evaluations to tailor the surgical approach to individual cases. The recommendations will outline the refractive ranges appropriate for various techniques, including surface ablation, LASIK and KLEx, giving surgeons clear criteria for choosing the best method.
The guidelines are expected to be completed and released by the next ESCRS meeting in Copenhagen in 2025. Once finalized, they are set to significantly improve both the safety and outcomes of corneal refractive surgery, providing surgeons with updated standards to follow in an ever-evolving field.
Editor’s Note: Reporting for this story took place at the 42nd Congress of the European Society of Cataract and Refractive Surgery (ESCRS 2024), held from 6-10 September in Barcelona, Spain.
References
- Reinstein DZ, Sekundo W, Archer TJ, et al. SMILE for hyperopia With and without Astigmatism: Results of a prospective multicenter 12-month study. J Refract Surg. 2022;38(12):760-769.
- Osman IM, Helaly HA, Abou Shousha M, et al. Corneal safety and stability in cases of small incision lenticule extraction with collagen cross-linking (SMILE Xtra). J Ophthalmol. 2019;2019:6808062.
- Noor IH, Seiler TG, Noor K, et al. Continued long-term flattening after corneal cross-linking for keratoconus. J Refract Surg. 2018;34(8):567-570.
- Hammer A, Richoz O, Arba Mosquera S, et al. Corneal biomechanical properties at different corneal cross-linking (CXL) irradiances. Invest Ophthalmol Vis Sci. 2014;55(5):2881-4.
- Piao J, Wang S, Tao Y, et al. Corneal epithelial remodeling after femtosecond laser-assisted in situ keratomileusis combined with intraoperative accelerated corneal collagen crosslinking for myopia: A retrospective study. BMC Ophthalmol. 2022;22(1):349.
- Amaral DC, Menezes AHG, Vilaça Lima LC, et al. Corneal collagen crosslinking for ectasia after refractive surgery: A systematic review and meta-Analysis. Clin Ophthalmol. 2024;18:865-879.
- Vargas-Fragoso, V, Alió JL. Corneal compensation of presbyopia: PresbyLASIK: an updated review. Eye Vis. 2017;4(1):11.
- Soler Tomás JR, Fuentes-Páez G, Burillo S. Symmetrical versus asymmetrical PresbyLASIK: Results after 18 months and patient satisfaction. Cornea. 2015;34(6):651-7.