Presbyopic LASIK – the final frontier
Stefanie Petrou-Binder MD
CAN refractive surgeons provide presbyopic patients with both satisfactory reading and distance vision? Two pioneering refractive surgeons presented contrasting viewpoints on this issue at the Congress of the German Ophthalmic Surgeons (DOC).
"What we term ‘presbyopic LASIK' is a surgery we developed that effectively provides the presbyopic patient with good distance visual acuity of 20/25 or better and near vision of J2 or better. We reshape the central 3 mm zone to be multifocal but leave the most peripheral area of the cornea unchanged for intermediate and distance vision," asserted Luis A Ruiz MD, Scientific Director of the Centro Oftalmologico Colombiano Bogota, Bogota , Colombia . Dr Ruiz and his colleagues in Bogota performed close to 1,500 presbyopic LASIK corrections since 1993 when they began developing this specialised surgery. Dr Ruiz described the procedure as involving a corneal flap and the formation of a precise annular ablation in the central zone of the newly exposed corneal stroma. This leaves an un-ablated central protrusion of the stroma and transforms the exterior surface of the replaced flap into a multifocal surface, he said.
Dr Ruiz' studies revealed that while the central 3.0 mm area of the cornea is the ideal site for near visual correction, it does not affect intermediate or distance vision, as the more peripheral corneal areas remain unchanged. He pointed out that the pupil naturally contracts for near vision, which seems to support this theory.
The masked approach
To create the circular ablation, Dr Ruiz combines a PMNIA mask with his laser (PTK program), which provides a laser beam with a diameter larger than that of the mask. "Second generation lasers allow us to create the annular ablation directly. The slope toward the unablated central zone is relatively steep, while the slope directed toward the periphery becomes flatter, giving the ablation its spherical shape," he reported.
Dr Ruiz uses laser software with predetermined annular ablation profiles that correspond with preoperative defects. He treats patients with presbyopia alone, or presbyopia with concomitant myopia or hyperopia, with or without astigmatism. "By treating other refractive defects at the same time as presbyopic LASIK, we reduce the ablation time and the recovery time." Dr Ruiz reported that his patients recover near vision on the first postoperative day. They experienced no regression. Distance vision, by contrast, required roughly two to three months to attain maximum visual acuity. Dr Ruiz suggested that surgeons operate on one eye at a time, allowing the patient to attain maximum distance vision in the first eye before going on to the second eye. He explained that the patient has the advantages of monovision in the interim, but with better distance vision and with fewer problems with stereopsis and aniseikonia.
"If the patient's eye requires cataract extraction after undergoing presbyopic LASIK, the reshaped cornea will provide good near vision following cataract removal," Dr Ruiz noted. He maintained that presbyopic LASIK was safe and effective for correcting presbyopia. He and his team are certain that the newest generation of lasers with advanced tracking systems and smoother ablation profiles will increase the efficacy of the procedure.
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"Centration is critical to avoid induced astigmatisms and loss of BCVA lines. With customised ablation, the procedure is also reversible and can be enhanced. To improve results, decrease recovery time, and minimise the occurrence of symptoms such as glare, halos and reduced contrast sensitivity, we make the ablation pattern more aspherical," Dr Ruiz affirmed. While some refractive surgeons subscribe to Dr Ruiz' method of treating presbyopia (and other refractive errors) by creating a multifocal central corneal area, others prefer to create monovision, as a safer, more effective option.
The monovision option
Theo Seiler MD, Institute for Refractive and Ophthalmic Surgery and professor at the University of Zurich , Zurich , Switzerland , has had good results with creating monovision in his presbyopic patients. "We have been using LASIK to create monovision since the early 1990s, with very satisfying results. It seems to be important to make the dominant eye emmetropic, while the second eye remains slightly myopic (around –1.0 D)," he said. He recommended that patients simulate monovision before undergoing surgery by wearing contact lenses, to test whether the individual patient is suited to monovision. Patients with higher astigmatism may not have this option, but the surgeon may still operate the patient at his request.
Refractive surgeons can perform re-ablation one month following the initial surgery for patients that are not satisfied with their results. "Presbyopic LASIK corrections are still in the scientific testing stages. Creating a multifocal cornea, such as supported by Dr Ruiz, is responsible for both reduced high- and low- contrast sensitivity. Many patients opt for monovision instead." "We performed presbyopic LASIK in the 1990s by creating a centralised undercorrection, a kind of ‘central steep island'. The overall results were disappointing. The price for the pseudoaccommodation was an increased light sensitivity and reduced visual acuity," Dr Seiler reported.
"Many patients were unhappy with the visual results and malpractice suits centred on the loss of vision due to the surgery."
Luis Antonio Ruiz MD
Centro Oftalmologico Colombiano Bogota
Bogota , Colombia
Theo Seiler MD, PHD
Institute for Refractive and Ophthalmic Surgery (IROC)
Zurich , Switzerland
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