Disclosure: Cimberle does not report relevant financial information.
Astigmatism is the most common and complex ametropia. Management requires careful analysis of many variables and personalized strategies.
“No one-size-fits-all concept can be applied to astigmatism because every astigmatism is different. We need to thoroughly examine each case, carefully review the data and design a tailored treatment strategy.” Ugo Cimberle, MD, called.
Today’s technology allows for the safe and effective treatment of any degree and type of astigmatism, regular or irregular, and the most difficult cases are often those that bring the best results and satisfaction.
“Astigmatism can be very debilitating. There are patients who have struggled for years with glasses that were never right and who see their lives completely changed after the operation. I’m often amazed myself at the results we can achieve,” he said.
When developing a strategy for astigmatism management, several factors need to be evaluated. Age and lens status are paramount as the presence of a cataract would immediately qualify the patient for a lens-based strategy.
Other basic determinations are the degree of severity and whether the astigmatism is congenital or secondary to trauma or corneal transplantation, regular or irregular, and axisymmetric or not.
“Very high post-graft astigmatism is better treated with a lens, but laser enhancement may be needed if there is an irregular component that toric IOLs cannot address,” Cimberle said.
He generally avoids IOL surgery in patients under the age of 45, especially myopic patients, but there may be exceptions.
“I implanted a toric IOL in a patient who underwent sliding intrastromal keratoplasty a few years ago and had a high degree of astigmatism and a very flat cornea. It changed her life dramatically,” he said.
Toric IOLs can effectively treat axisymmetric astigmatism, while irregular astigmatism with a pronounced non-axisymmetric component requires well-designed laser treatment. On the other hand, laser treatment has limitations in terms of the degree of astigmatism, and if it is too high, the treatment may need to be combined with IOL implantation.
“The severe hyperopia associated with this can also pose a limitation for laser treatment, as it would require excessive steepening of the cornea. Mixed astigmatism and myopic astigmatism are easier to treat with laser, but corneal thickness is always a critical parameter,” Cimberle said.
Individual laser treatments
Not only are all cases of astigmatism different, but all lasers are different and have different properties, capabilities, and algorithms that produce different results.
“Studies often generalize and say do this and don’t do that, but the do’s and don’ts depend on what laser you have. What doesn’t work well with your laser may work well with mine, or vice versa, and knowing your system well is extremely important,” said Cimberle.
Astigmatic treatments require best-in-class eye-tracking technology with static and dynamic cyclotorsion compensation, since just a few degrees of axis error can critically affect results. For normal astigmatism, standard ablation programs may be sufficient, but for other types with asymmetrically steep meridians, decentered corneal vertex, and high kappa angle, custom topography-guided and wavefront-guided ablation programs are highly preferred.
“We need special high-level software to maximize the results. With standard lasers, we can still use methods like bitoric ablation, but they’re a bit of a craft solution,” Cimberle said.
Using the Schwind Amaris platform, he personally believes there is no better laser for astigmatic treatments.
“Amaris’ custom ablation treatment profiles, based on wavefront analysis, allow us to address the effects of this imperfect morphology on aberrations, rather than the imperfect morphology of the cornea. It adapts the treatment extremely precisely to each eye individually. Combined with very precise and reliable eye tracking, it delivers unbeatable results for all types of astigmatism up to 7D,” he said.
Toric IOLs have also evolved to high standards and the choice is a matter of subjective preference and habit.
“There are no objective criteria in favor of one-piece IOLs versus C-loop IOLs, and both types now have a good level of rotational stability,” said Cimberle.
Large eyes can sometimes have problems where rotation can never be completely ruled out and repositioning may be necessary.
“Patients should know that rotation is not common but can occur and we cannot predict if and when it will occur as it depends on how their capsular bag responds to the implantation. You should know that in these cases, re-rotation is required,” he said.
Early rotation is easy to set, but late rotation due to capsular bag contraction is better treated with a laser or piggyback lens implantation.
For eyes where astigmatism can change over time, such as after a corneal transplant, Cimberle suggested piggybacking a toric IOL in the sulcus over a monofocal IOL implanted in the capsular bag from the start.
“If the astigmatism changes, you can more easily reposition the piggyback lens long after implantation,” he said.
IOL alignment is a crucial step and while the traditional manual inking methods based on topography can still be a good option, digital systems such as the Callisto eye (Carl Zeiss Meditec) and the Verion digital marker (Alcon) offer an improved one precision and reliability.
Slicing techniques are no longer part of Cimberle’s weapon arsenal.
“We’ve been using them for many years, but incisions always weaken and alter the biomechanics of the cornea to some extent. They’re easier to do but we have two options that work so well, I don’t think we need cuts these days,” he said.
Successful astigmatic treatment, be it laser or toric IOL implantation or both, results in a high level of patient satisfaction – even more so when the astigmatism is high, asymmetric and irregular and therefore is never properly treated by eyeglass correction.
“Whether regular or irregular, astigmatism is always worth treating. Even if full correction cannot be achieved, there is always enough improvement to make patients happy,” said Cimberle.
A slight residual astigmatism can be desirable as it can increase the depth of field.
“Be aware of this when implanting a toric IOL in presbyopic patients with cataracts as it can impair near vision. A low level of astigmatism against the rule should be left as it provides the low level of multifocality that helps see without glasses. Customize the refractive targeting and remember that perfection isn’t always the best choice,” he said. – by Michela Cimberle
- For more informations:
- Ugo Cimberle, MD, is Head of Ophthalmology at the Villa Maria Cecilia Hospital, Cotignola, and at the San Pier Damiano Hospital, Faenza, Italy, contactable at Piazza Carlo Luigi Farini, 4 – 48121 Ravenna (RA), Italy; Email: firstname.lastname@example.org.