Treating +4.0 hyperopia?
For younger patients, LASIK, SMILE are top options. Howard Larkin reports
Fernando Faria-Correia MD, PhD
Consider the case of a 35-year-old female paediatrician with +4.00D hyperopia. In four years, her uncorrected visual acuity declined from 2/20 to 20/100 in both eyes, while her spectacle prescription increased from +2.25D to +3.50D. Looking for a solution that would increase her visual independence, she consulted Fernando Faria-Correia MD, PhD, of CUF Porto, Porto, Portugal.
After careful corneal tomography and biomechanical analysis, and counselling and treatment for slight dry eye, Dr Faria-Correia recommended topography-guided femto-LASIK, he told AAO 2020 Virtual. One month after surgery her uncorrected VA was 20/25 in the right eye and 20/20 in the left. The patient was quite satisfied despite some blurry vision episodes that Dr Faria-Correia said were consistent with corneal epithelial remodelling typical of hyperopic LASIK.
Understanding the difference between facultative hyperopia, which can be overcome by accommodation, and absolute hyperopia, which cannot; as well as manifest hyperopia measured with noncycloplegic refraction and latent hyperopia measured with cycloplegic refraction, were keys to determining the treatment, Dr Faria-Correia said. Ocular surface optimisation and preoperative corneal evaluation helped improve the outcome, while epithelial mapping using segmented topography helped him understand the visual outcome, he added.
But what would other ophthalmologists do? Two other surgeons gave their views on the best treatment for laser corneal correction of a young +4.00D hyperope.
Making the case for hyperopic LASIK was Gustavo Tamayo MD, director of Bogota Laser Ocular Surgery Centre, Bogota, Colombia. He considered three surgical options.
Refractive lens exchange with IOLs is not an option “unless we change the definition of young”, Dr Tamayo said. Phakic lenses are subject to exacting requirements, most significantly a 3.0mm anterior chamber depth that is unusual in small hyperopic eyes, and are subject to severe complications, he said. With corneal additive surgeries having died out, hyperopic LASIK is the most attractive surgical option, he reasoned.
Dr Tamayo listed several critical factors for hyperopic LASIK. Maximum post-op corneal curvature is 50D, so the amount of hyperopia that can be corrected may be limited by pre-op corneal curvature, with one dioptre of hyperopia corrected increasing corneal curvature by the same amount. Cycloplegic refraction and post-op lubrication are also essential.
Outcomes are excellent, Dr Tamayo said. In a study of 98 hyperopic eyes treated with LASIK or LASEK in his clinic, 93% had 20/20 uncorrected vision and 98% 20/40 or better and only 2% with worse corrected vision 24 months after surgery – results that echo FDA trial data from 2004 and many studies since. While patients must be made aware that the correction will regress over time, enhancements are easy and complications few and mild compare with phakic IOLs.
“Hyperopic LASIK is the best option for young hyperopes, particularly up to +6.00D,” Dr Tamayo concluded.
Making the case for SMILE was Rupal Shah MD, group medical director at the Centre for Sight-NVLC, Vadodara, India. While still a short way from commercial availability and not approved in the USA, SMILE for hyperopia has several advantages over LASIK, she said. These include no flap or related complications, a smaller incision that affects tear profile less after surgery, no tissue ablation resulting in less scatter and more predictable outcome, and lower overall energy input leading to less inflammation and greater stability after treatment.
An early study Dr Shah conducted on 100 hyperopic eyes in 2010 found results were less stable and predictable than hyperopic LASIK. Alterations to the procedure heave since improved it, she said. These include altering the lenticule geometry, increasing the transition zone to 2.0mm and optimising laser settings. This larger transition zone creates a tapering edge to the lenticule rather than a steep drop off due to the larger amount of tissue removed at the perimeter to flatten the cornea.
Current multi-centre studies are being analysed, though the results are promising, approaching or even exceeding hyperopic LASIK in some cases, Dr Rupal said.
“For younger hyperopes, laser refractive surgery is more appropriate, and SMILE would be my natural choice.”
Theo Seiler MD, PhD, founder of Institute for Refractive and Ophthalmic Surgery (IROC) in Zurich, Switzerland, congratulated Dr Tamayo on his excellent LASIK outcomes.
“Our hyperopic results are poor; 30% of complaints I see in my clinic are because of hyperopic LASIK.”
Dr Seiler said the main problem is the optical zone size, which ranges from 6.5mm to 7.0mm with a 1.0mm transition zone. A lack of understanding where to centre the LASIK ablation or SMILE further complicates the procedure, he added. This reduces overall patient satisfaction with corneal hyperopic corrections to about 70%.
However, Dr Shah reported good results with hyperopic SMILE up to +4.0D. Dr Seiler suggested that this may be due to newer procedure guidelines Dr Shah is using, which allow a total lenticule diameter in the 8.5-to-9.0mm range. But the optical zone declines from year to year due to epithelial remodelling, he noted, making long-term results problematic. Dr Shah stated she has not seen such regression in her patients with a larger transition zone.