Taking a closer look at the irregular cornea
Professor Thomas Kohnen
The ESCRS and EuCornea collaborated to present a large symposium, “The Irregular Cornea”. The symposium, which took place during the XXXV Congress of the ESCRS in Lisbon, featured six speakers, who each approached the problem from a different angle.
Professor Harminder Dua, Queen’s Medical Centre, Nottingham, UK, discussed “The Irregular Keratoplasty Cornea”.
“Keratoplasty is an art, not just a technique or science,” said Prof Dua. He covered each type of keratoplasty, focusing first on penetrating keratoplasty (PK), in which host factors can contribute to significant irregularity. An interesting tip he offered delegates was to inject fibrin glue into the anterior chamber and graft-host junction for persistent leaks related to graft-host bed disparity.
Corneal incisions were covered by Professor Thomas Kohnen, Goethe University, Frankfurt, Germany.
“Corneal incisions have several indications, including natural astigmatism, post-PK eyes, during or after cataract surgery, and following refractive surgery,” said Prof Kohnen. Limbal relaxing incisions (LRIs) are effective up to 2.0 dioptres.
“When performing LRI after LASIK or PRK, make sure to place the incisions central to the insertion of conjunctival vessels and peripheral to the LASIK flap,” he reminded delegates.
The femtosecond laser can also be used to great effect after keratoplasty. “This is safe and easy, and can reduce topometric and subjective astigmatism, although there doesn’t seem to be a significant change in visual acuity,” said Prof Kohnen. He predicted that laser-specific nomograms will be developed in the future.
Professor Leopoldo Spadea, University of Rome, Italy, discussed the use of the excimer laser to correct corneal irregularities.
“There are many good indications for customised corneal ablation treatments, including ocular injuries, burns, post-infectious scarring, corneal ulcers and pterygium,” said Prof Spadea. He also added prior eye surgery to that list, in cases of decentred ablations, central islands and post-keratoplasty astigmatism.
Prof Spadea outlined two approaches: surface, including advanced surface ablation; and intrastromal, which includes LASIK.
“Topographic customised treatment strategies require a precise combination of topographic elevation data of both corneal surfaces, refractive data and pupillometry,” he said. This technique allows us to correct the majority of irregular corneas, he concluded.
Covering the controversial topic of intracorneal rings was Professor Joaquim Murta, Centro Hospitalar Universitario Coimbra, Portugal.
“Indications include not only keratoconus, but also post-keratoplasty irregular astigmatism,” said Prof Murta. Contraindications include K-values > 70D, central corneal opacifications and high patient expectation for uncorrected emmetropia.
“Make sure not to implant too centrally, or dysphotopsia will occur,” he reminded delegates.
Professor António Marinho, Hospital Arrábida, Porto, Portugal, shared his experiences with cataract surgery in irregular astigmatism. Prof Marinho suggested treating irregular astigmatism prior to cataract surgery.
“This can be done using intracorneal rings or topo-guided PRK and then waiting at least three-to-six months before performing cataract surgery,” he said. Because the biometry will be challenging, consider intraoperative aberrometry. Spherical monofocal IOLs are the rule, and pinhole IOLs can be used for extreme cases.
Professor José Güell, Institute of Ocular Microsurgery, Barcelona, Spain, finished the symposium with a discussion of phakic and add-on IOLs to treat ametropia in irregular corneas.
“In most cases, ametropia in the irregular cornea cases will be managed with contact lenses, but phakic and add-on IOLs may significantly improve visual acuity and patients’ quality of life,” he said.