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Many patients undergoing phacoemulsification want more than simply cataract extraction. Dr Detlev Breyer says that advances in surgical technique and IOL design have made it possible to satisfy most patients' requirements.
Co-axial microincisional surgery (CO-MICS) through a 1.6–1.8 mm incision with implantation of the Acri.LISA Toric 466 TD aspheric toric bifocal IOL (Carl Zeiss Meditec) represents an excellent solution for achieving successful phacorefractive surgery, according to Detlev Breyer, MD.
"Many patients with astigmatism are interested in having a presbyopia-correcting IOL implanted," said Dr Breyer. "However, correcting the astigmatism with incisional techniques does not always provide reliable results, and the outcomes can change over time.
Acri.LISA toric IOL design
The lens is constructed of a hydrophilic acrylate material with a hydrophobic surface, and is available in a range of powers for sphere (-10 to +32 D) and cylinder (1 to 12 D). With a total diameter of 11 mm and an optical diameter of 6 mm, the lens can be implanted through incision sizes >1.5 mm, so that it retains the benefit of MICS in terms of a procedure that is astigmatically neutral.
The biconvex plate style implant has a four-haptic design to provide the rotational stability and centration that are critical to good long-term outcomes. It features an aspheric design on the front and back surfaces, which has benefits for improving contrast sensitivity, increasing depth of focus, and reducing poor vision symptoms at night. The toricity component is on the anterior surface of the optic along with positioning marks to guide surgeons in lens orientation. The posterior surface is bifocal with a diffractive structure that has smooth steps to reduce light scatter. The lens features a power add of +3.75 D and distributes light asymmetrically: 65% for far and 35% for near. This asymmetric light distribution helps to improve intermediate vision while also reducing haloes and glare at night.
Dr Breyer stated that optimal results with the IOL require true MICS surgery: this means that the incision size must remain below 2 mm even after IOL implantation. Dr Breyer's preference is to use the Oertli phacoemulsification platform with the CO-MICS 2 tip, which allows CO-MICS through a 1.6 to 1.8 mm incision.
"As the CO-MICS procedure is astigmatically neutral, it therefore optimizes the predictability and precision of phacorefractive surgery," Dr Breyer noted. "It also minimizes the induction of aberrations."
According to Dr Breyer, in contrast to bimanual sleeveless MICS, monomanual CO-MICS has no intra-or postoperative leakage problems, has better fluidics and phacodynamics, and less postocclusional surge.
"Achieving an emmetropic outcome is also critical, and so optical biometry (using the IOLMaster from Carl Zeiss Meditec) should be used for axial length measurements because of its high precision," Dr Breyer added.
The perfect implantation
Providing a few more surgical tips, Dr Breyer said that reference marks should be placed on the eye while the patient is sitting upright. He encouraged surgeons to take the time to create a perfect capsulorhexis, which should measure about 6 mm and be centred perfectly. If the capsulorhexis is too small, the IOL position can shift postoperatively, he cautioned.
Dr Breyer also recommended performing extensive hydrodissection; this should minimize intraoperative stress on the zonules, taking into account that the alignment of the IOL is inevitably associated with a certain degree of zonular stress. Dr Breyer also clarified that he does not use viscoelastic for the implantation, to avoid the potential for lens rotation when the viscoelastic is removed.
An injector system for implanting the IOL (such as the Acri.Shooter from Carl Zeiss Meditec) is a push-type device that is easy to use and allows surgeons to fixate the globe with their second hand, he said. Although the IOL is not ultra-thin, it compresses readily, allowing it to fit through incisions as small as 1.6 mm, Dr Breyer added.
Patients report positive outcomes
"Results from 11 patients who underwent bilateral CO-MICS with implantation of the IOL demonstrate the excellent outcomes achieved using this combination approach to phacorefractive surgery, even in patients with high astigmatism," he said. Excluding one patient after keratoplasty and another with amblyopia, distance vision equivalent to or better than the legal level required in Germany for driving without spectacle-correction was achieved in all of the remaining patients, and they were also able to read newspapers without glasses.
Responses to a questionnaire conducted postoperatively demonstrated a high level of patient satisfaction. Only one patient reported wearing glasses at nighttime for driving, noting that he felt more comfortable. All 11 patients responded in the affirmative to questions asking whether the IOL met their expectations and if they would recommend the lens to a relative. All patients were offered LASIK at no charge to improve their uncorrected visual acuity, and all declined.
"The ability to avoid a bioptics procedure is an enormous benefit of this approach to phacorefractive surgery with CO-MICS and implantation of this toric bifocal IOL," Dr Breyer said.
Although he said he would not recommend this IOL for older patients or in eyes that have undergone penetrating keratoplasty, an 80-year-old patient with amblyopia was very happy with the outcome after surgery, Dr Breyer claimed.