Long-term outcomes

Professor Thomas Kohnen and Professor Rudy MMA Nuijts What happens to our refractive surgery patients in the long term? A panel of leading ESCRS ophthalmic surgeons addressed this question at a special session of the American Academy of Ophthalmology annual conference in San Francisco, drawing on primary research and extensive literature searches. Subtractive corneal surgeries Surface ablation, including PRK and trans-PRK, lamellar procedures, including LASIK and femtolaser, and lenticule extraction procedures, including SMILE®, are safe and produce comparable visual outcomes with good predictability for periods up to 18 years, said Thomas Kohnen MD, PhD, FEBO, of Goethe University, Frankfurt, Germany. While serious complications are rare, all subtractive procedures change the cornea’s shape and refractive power by removing tissue through ablation or lenticule removal, effectively thinning it. Because of this, treatment guidelines recommend limiting the power of corrections. For example, the German commission for refractive surgery (KRC) guidelines revised for 2019 call for generally applying myopic corrections up to -6.0Dfor PRK, and -8.0D for LASIK and SMILE, limiting corrections to no more than another -2.0D in any case, Prof Kohnen noted. Short-term corneal haze is still an issue with surface ablation, though it generally clears with time. Haze risk increases with deeper ablations, poor corneal surface quality, hyperopic and high astigmatism corrections, repeat treatments, UV exposure and age, Prof Kohnen said. Long-term issues with PRK and LASIK include myopic regression, with LASIK more stable after six years. SMILE refractive results are stable out to five years. Challenges include predicting and preventing ectasia, and accurately calculating IOL power for subsequent cataract surgery. Phakic IOLs With angle-supported PIOLs no longer on the market, Rudy MMA Nuijts MD, PhD, of Maastricht University Eye Clinic, the Netherlands, focused on iris-fixated and implantable collamer lenses (ICLs). Iris-fixated lenses are available in myopic corrections up to -23.5D for non-foldable, and -14.5D for foldable, while ICLs range from +10.0 to -18.0D, making them useful for higher corrections. However, in prospective studies both angle-supported and ICL PIOLs increase endothelial cell loss by two-to-three times physiological rates overall, though rates vary widely and loss may accelerate significantly after 10 years. In addition, all phakic IOLs promote increased axial length, and ICLs promote anterior subcapsular cataract formation, resulting in an overall mean decline in uncorrected distance visual acuity of 1.5 Snellen lines due to myopisation and cataract at 10 years. In addition, 10-year explant rates vary up to 12% for iris-fixated PIOLs and 18% for ICLs, though explant rates for iris-fixated lenses may increase significantly after 10 years. Explantation risk is increased by shallow anterior chamber depth, preoperative endothelial cell density and hyperopic corrections for iris-fixated PIOL risk, and long-term insufficient vaulting leading to cataract formation with ICLs, Dr Nuijts noted. He recommended regular follow-up checking endothelial cell loss extending past 10 years, and counselling patients that PIOLS may be a temporary solution. Toric IOLs Long-term toric IOL success depends on rotational stability, said Oliver Findl MD, of Hanusch Hospital, Vienna, Austria. Rotation mostly occurs in the first hours after surgery and is less likely once the capsule fuses, though fibrosis may result in late rotation. Steps during surgery that may help prevent early rotation include waiting for full haptic extension, completely removing viscoelastic and maintaining anterior chamber stability. Resting patients for an hour after surgery may also be helpful, Dr Findl said. Generally speaking, rotation risk drops substantially after about 15 days due to fusing of the anterior and posterior capsule. When implanting toric IOLs in younger patients, long-term axis shift should be considered, Dr Findl said. With-the-rule astigmatism begins to shift toward against-the-rule around age 36, continuing until about age 69, mostly due to changes in the anterior corneal surface possibly from reduced eyelid tension. Therefore, patients in their 40s or early 50s should be under-corrected for with-the-rule astigmatism, and fully corrected or even over-corrected for against-the-rule errors to improve long-term visual outcomes. Multifocal IOLs Multifocal IOLs are not advisable for patients at risk of central visual field reduction due to macular degeneration, retinal disease or glaucoma, due to the risk of reduced visual acuity and contrast sensitivity, said Béatrice Cochener-Lamard MD, PhD, of the University of Brest, France. MIOL complications occur mostly in the short term, Dr Cochener-Lamard said. Patients with capsule ruptures are at higher risk of cystoid macular oedema. Patients 
who are younger (less than 54 years old), male and with long axial (over 24 mm) length are at higher risk for retinal detachment, according to a retrospective study on 1,500 patients followed for five-to-10 years). Nd-YAG capsulotomy for PCO did not increase retinal risk significantly, 
but it should not be done earlier than six 
months after surgery and after eliminating 
all other causes of visual impairment. Primary open-angle glaucoma presents an MIOL challenge due to reduced contrast sensitivity while pseudoexfoliation increases the chances of lens dislocation, Dr Cochener-Lamard noted. Any intraoperative complication that compromises good and safe positioning of the multifocal IOL justify to switch for a monofocal implantation. Failure to neuro-adapt is the unpredictable cause of MIOL failure, Dr Cochener-Lamard said. Other factors are decentration, IOL opacification, large pupil size and, first of all, dry eye. These should be considered before surgery. All can induce dysphotopisa, haloes, glare, diplopia, poor visual recovery, all occurring actually in short term. Finally, while there are no reports of explantation after 10 years, what happens to MIOLs after 20 years is unknown, so care should be taken in implanting them in young patients, she added. Success of the surgery is determined by proper patient selection and exhaustive information, and talk of the long-term is required. Thomas Kohnen: 
kohnen@em.uni-frankfurt.de
Rudy Nuijts: rudy.nuijts@mumc.nl
Oliver Findl: oliver@findl.at
Béatrice Cochener-Lamard: 
beatrice.cochener@ophtalmologie-chu29.fr

Tags: refractive surgery