Drs. Wörtz and Fram discuss the value of biometry and topography when treating patients with more complex cases of astigmatism, and Dr. Fram reviews her process for identifying the best treatment approach based on patients’ corneal characteristics.
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How to discuss astigmatism with patients
Dr. Fram highlighted that she has changed the language she uses from correcting astigmatism to reducing astigmatism, as it is a key distinction to make to patients during conversations. She prefers to explain to patients that the treatment goal is not necessarily to get rid of all of the astigmatism, but to reduce it as much as possible to improve their visual function.
She began changing how she discusses astigmatism with patients due to the occurrence of unpredicted or residual astigmatism that may linger even if the surgeon has used calculators, formulas, and pre-operative diagnostic testing to hit the refractive target.
Measuring biometry and topography for astigmatic patients
For a patient with 2 diopters or more of astigmatism, either with-the-rule (WTR) or against-the-rule (ATR), Dr. Fram emphasized the importance of:
- Looking at the topography first to ensure the findings are reproducible.
- Acquiring clear Placido imaging.
- Establishing symmetry of the astigmatic bowtie on the topographic image.
Once the quality of the corneal topography has been confirmed, she then evaluates the patient’s biometry. Dr. Fram uses two different biometer units (IOLMaster 700 and LENSTAR) since it allows her to compare the readings between the devices to ensure that the measurements are accurate.
Lastly, Dr. Fram assesses the autorefraction (AR) for an additional data point to make certain that she has reproducible reporting of the astigmatism. Next, she reviews the strength of the patient’s glasses prescription before they developed a cataract (if available), as it helps her to better understand the patient’s vision, particularly in borderline cases.
Dr. Wörtz added that based on his clinical experience, if the anterior axis does not match the patient’s glasses by amplitude or axis, he likes to look at their glasses prescription to check if their posterior corneal astigmatism is pulling the patient’s refractive astigmatism in a specific direction.
The value of intraoperative aberrometry
Additionally, Dr. Fram utilizes intraoperative aberrometry as she finds it to be a powerful tool that measures aphakic refraction to provide surgeons with total corneal power, as long as the incisions are not overhydrated and the surgeon has reliable biometric and topographic readings.
Further, she explained another feature of intraoperative aberrometry lies in the ability to track data. Dr. Fram leverages this data as a “gut check” of sorts when going back to look at prior cases, whether it was an Eyhance Toric, EnVista Toric, or Alcon SN Toric lenses.
Dr. Wörtz added that intraoperative aberrometry, much like any tool, is only valuable to the surgeon if they feel comfortable using it in their hands and thoroughly understand its appropriate application.
Using online formulas and calculators to manage astigmatism
As part of Dr. Fram’s surgical protocol, after looking at the AR, biometry, and topography, these values are integrated into the Barrett Toric Calculator, Dr. Fram’s calculator of choice, and then this is further integrated into the ZEISS VERACITY software on her IOLMaster 700. Dr. Wörtz commented that for a long time he only used online calculators, but eventually, he shifted to only using the Barrett Toric Calculator. However, his partner still uses online calculators in addition to the Barrett Toric Calculator because the two don’t always agree.
Dr. Fram explained that this might occur because, for a period of time, the Alcon Toric Calculator did not account for posterior astigmatism, but now the Barrett Toric Calculator does account for posterior corneal astigmatism. As a result, while they are still helpful, Dr. Fram no longer uses online calculators and only uses the IOLMaster 700 and LENSTAR.
She added that this is where VERACITY can be particularly helpful, as it offers surgeons the ability to blend measurements taken from different instruments to get total corneal astigmatism. Anecdotally, Dr. Wörtz emphasized that this program is an efficient way to integrate data from machines to get improved and individualized results for patients.
Reducing astigmatism while factoring in patient vision expectations
Next, Dr. Fram outlined her process for treating patients with oblique astigmatism and borderline cases who have closer to just 1 diopter of astigmatism. She noted that earlier in her career, she would never flip the axis to ATR, and she always planned to leave a little WTR because as patients age, there is more compensatory ATR contribution.
However, with time, she has also come to understand that patients expect to have their astigmatism reduced to a point of less than half a diopter. As such, she has begun minimally flipping the axis to get the most amount of astigmatism reduction at the time of surgery, which is a personal preference.
Why Dr. Fram implemented light adjustable lenses into clinical practice
As the goal of treatment is to customize the lens to the patient’s needs, when deciding whether light adjustable lenses (LALs) would benefit her patients and the practice, Dr. Fram looked at the number of patients who were post-LASIK and post-radial keratotomy (RK) with good Placido imaging. After calculating this number, she found that they made up almost 20% of the practice’s patient population.
Additionally, at the time, she performed many “mini-monovision” procedures, so as long as patients had 3 diopters or less of astigmatism, she realized that it was possible to capture all of the astigmatism, though it at times required multiple treatments to get this result.
Anecdotally, after 1 year of implementing LALs into clinical usage, now 93% of patients are within half a diopter for post-myopic-LASIK patients. She highlighted that slight drifts are possible, and she has heard of patients experiencing up to a quarter diopter of drift, but in her medical opinion, she has not often encountered this issue.
An essential aspect of having strong surgical outcomes with LALs is implanting these lenses in patients with clear Placido imaging, as the light adjustable technology does not correct what is in the cornea. She added that post-RK patients might still experience fluctuation because they have RK incisions of potential variable depth and quantity. As such, she always tells patients that they could experience their best vision with a contact lens in addition to the LAL.
While the technology is incredibly beneficial for patients, it is imperative that the surgeon has a strong setup to support the long-term implementation of LALs. Two essential factors for successfully integrating LALs include having time in-clinic to adjust the lenses and having a strong MD/OD practice where an optometrist can support the preparation of the patient for surgery with appropriate diagnostic testing.
New lens technologies on the horizon
A new lens technology that Dr. Wörtz is excited about is the IC-8 Apthera intraocular lens (IOL), especially for post-RK patients and individuals with keratoconus. Dr. Fram highlighted that in Europe, the IC-8 IOL was most beneficial for patients with aberrated corneas.
The pinhole technology in the lens increases the depth of focus and can help correct astigmatism without having to make any incisions. Further, decreasing higher-order aberrations is the treatment goal for many of these patients, so for patients with keratoconus and increased spherical aberration, the IC-8 IOL could be a good fit.
Dr. Fram added that it is important to keep in mind that these patients often need a YAG laser procedure later on, and some patients reported slightly darker vision during the trial, though it was not to a degree that required explantation of the lens. She remarked that this lens is an exciting addition to the armamentarium that can be used for patients who are suffering from the quality of their vision due to corneal aberrations.
Conclusion
As there is now a plethora of IOL choices available to surgeons to address uncorrected astigmatism, utilizing measurements from devices such as biometry and topography are foundational tools to identify an appropriate lens choice for the patient.
