Future Forecast

LASIK has come a long way – but that raises the question of where it might end up. Is there any room left for improvement, or have we taken it as far as it can go? Karl Stonecipher’s view is unambiguous: “People always think that LASIK is done – but we’ve never had a procedure that just disappears. Evolution always continues.” And John Marshall reminds us of recent evolutionary improvements aimed at improving excimer lasers. “Algorithms have been adjusted so that successive laser pulses are sufficiently separated to avoid crosstalk or thermal changes; helical electrodes are being introduced – enabling smoother laser cavities – and they are much more reliable than before; and solid state UV systems have been given fresh impetus due to their importance in military and space technology.” Marshall is particularly excited about the new generation of UV lasers, which has overcome the epithelium penetration issue that previously dogged this technology: “Using a UV plasma to produce changes deep in the stroma is far more accurate than existing methods,” he says. Other technologies to watch, he adds, include two-photon systems which change the refractive index at set layers in the cornea. “There’s a lot of technology coming through that will have a huge impact,” he concludes.

Julian Stevens identifies a number of fields where advances in instruments or research could help improve LASIK even further; as an example, he suggests the likely benefit of an improved understanding of the influence of corneal hydration on collagen density and biomechanics. In addition, he says, current LASIK technology does not sufficiently allow for corneal curvature. “Using an IntraLase femtosecond laser applanates the cornea, and the cornea doesn’t immediately relax to its natural curvature – it’s still relatively flat. In fact, at that point there’s about 5 D of hyperopia, which contributes to the patient’s blurred vision.” Stevens continues: “Our cosine energy adjustment for the angle of the excimer laser on the cornea is completely incorrect: suggesting that the subtleties of a diopter here and there have any significant impact are nonsense.” Other areas for improvement, suggests Stevens, include real-time refractive tracking techniques, better methods for taking account of scatter versus angle, and centration movement control: “When a patient moves under the laser, the angle changes and you get under-correction; proper fixation gives much better results.” His conclusion? “We have a long way to go!” Maloney concurs: “I agree that we need a method of measuring the eye that does not depend on subjective input, and that is immune to accommodation – which is really the only problem with autorefraction and wavefront-guided techniques.” Also on Maloney’s wish-list: a method of strictly controlling laser energy to 0.5 percent instead of 3 percent: “Our laser energy sensors are very good, but they’re not at 0.5 percent – and a 3 percent error on a 7 D myope is 0.21 D.”

Stonecipher agrees that LASIK will continually improve; not step-changes, he says, but incremental improvements to safety and outcomes. These changes could take the form of better techniques and systems – cyclotorsion, wavefront techniques, Contoura, T-CAT, and topographic modified refraction – or better diagnostics for improved decision-making. “In the old days,” says Stonecipher, “we didn’t know how to say no – not because we were bad doctors, but because we didn’t know who to say no to.” Continual improvements in diagnostics, however, will increasingly allow ophthalmologists to guide patients to some treatments rather than others.

In the context of guiding clinical decisions, John Kanellopoulos believes that the Brillouin microscopy method of non-invasively measuring corneal biomechanics will play a significant part in the future of LASIK. “It’s the missing piece – probably the most important missing piece – in preoperative and postoperative assessment for all laser vision correction surgery, but particularly LASIK,” he says. Why is it so important? Because LASIK changes corneal biomechanics dramatically, and the corneal biomechanics that exist in the preoperative eye can critically affect LASIK outcomes. “Brillouin will be a pivotal tool for identifying patients who may not be good candidates for laser procedures,” advises Kanellopoulos. “Postoperatively too, it can identify patients who may have a propensity for ectasia and hence require a preemptive therapeutic procedure.” He acknowledges more work is required before we see a mainstream device based on the Brillouin concept; even so, he says, “I can’t wait to have one in my office.” More generally, Kanellopoulos suspects that ophthalmologists may soon become more cautious about altering the cornea too much: “If we’re going to use the cornea as part of the optical apparatus with a new lens, we may want to be more careful with the patterns of ablation we employ, the optical zone we use, and the range of myopia we address.”

Robert Maloney suggests that future LASIK procedures will be assisted by improved topography: “Current topography systems provide noisy data – and when you remove the noise to get rid of artifacts, you also lose some detail.” Improvements in this field might improve detection of subclinical keratoconus, he suggests. Stefanie Schmickler agrees that current topography methods have room for improvement; in particular, she cites the examples of patients with smaller or deep-set eyes. “We still have problems getting good data from these patients – improved topographic devices would be welcome.”

Are there any other ways of separating good from bad LASIK candidates? Kanellopoulos points to artificial intelligence as an auxiliary tool: “I see it as a helping hand; AI systems based on knowledge acquired through many years of trial and error can remind us of where we can or cannot intervene.” The ability to red-flag danger signs in the cornea, he asserts, make AI-based tools pivotal even for experienced LASIK surgeons: “It can only make our work safer and better.”

But might we see developments that could radically alter the LASIK procedure itself? We’ve been hearing about ray-tracing LASIK for several years – is it ready for the mainstream? Schmickler is skeptical: “If we really needed it, it would already be mainstream! People are happy with femto LASIK and aberration-guided LASIK.” Maloney is also cautious, emphasizing the importance of not confusing the method of measuring aberrations with the aberrations themselves. He reminds us that there are ways to measure aberrations other than ray-tracing – Hartmann-Shack, for example – and it’s not clear which method will be the best. But he is clear on one point: “There is good evidence, for example from Edward Manche’s studies at Stanford that measuring aberrations improves outcomes. Randomized trials have shown that measuring aberrations preoperatively gives better postoperative results.” What other LASIK improvements might we see? Maloney notes that the need for enhancements – secondary procedures – has dropped to about four percent. “This isn’t bad, but it doesn’t seem to be decreasing further; and that concerns me because a four percent rate of enhancements is, in a sense, a four percent failure rate.” Maloney believes that the way to get sub-one percent enhancement rates is via wavefront analysis: “We need measurement approaches that are better than manifest refraction, and I believe wavefront analysis can deliver the precise measurements we require.”

Looking further ahead, LASIK procedures may end up being informed by genetic data. Marshall sees a future in which LASIK procedures are melded with personalized medicine, with specific reference to genetic determinants of wound healing and tissue interactions. Similarly, advances in corneal ectasia will be driven not only by improved biomechanical measuring devices – which will provide objective measurements in the clinic – but also by genetic tests. “Detection of genes that influence biomechanics will be more important than taking biomechanical measurements,” asserts Marshall. “Important genes may include those which govern corneal granular dystrophies or keratoconus – a number of keratoconus genes seem to have roles in biomechanics.” Marshall’s view is that patients will have DNA collected and analyzed prior to refractive surgery: “From a buccal swab, the patient’s gene profile will be defined with regard to refractive surgery risks, and that information will guide clinical decisions and significantly reduce the number of complications.