This post will expand on the topic of corneal toricity introduced in last month’s entry.
Astigmatism can be a source of confusion for our patients and as just one part of a lengthy preoperative discussion can sometimes feel overwhelming (for the patient and the doctor!).
Appropriate patient selection and counseling help ensure the best surgical outcome for our patients, especially when considering a premium IOL. But properly educating a patient on their personal measurements and what that means for their IOL options also has a very important role in managing patient expectations.
The foremost example of this would be informing a patient with significant corneal astigmatism that their best-corrected visual acuity will be with updated glasses 1-month postop if they chose the standard over a toric IOL, no matter that their neighbor or spouse ended up with no distance glasses after cataract extraction.
As an optometrist working at a surgical comanagement clinic, corneal astigmatism is a focus when evaluating a patient for cataract surgery. We remember that a patient’s total astigmatism that was corrected in their glasses or contacts takes both their corneal and lenticular cylinder into account. However, if one is proceeding with cataract surgery, the patient’s astigmatism originating in their natural lens is no longer a concern because it will be eliminated with cataract extraction. (As you can imagine, preoperative refraction can, in fact, have little influence when determining if a patient would benefit from the specialty toric IOL.)
In our clinic, a patient’s corneal cylinder can be measured three or even four ways to be sure of the accurate magnitude of cylinder and its axis; measurements include biometric readings with the Lenstar (Haag Streit), Scheimpflug imaging with the Pentacam (Oculus), autokeratometry and even manual Ks when necessary.
This brings us to the significance of the term “premium IOL.” Like multifocal IOLs, toric implants are not covered by insurance and so come with out-of-pocket expense for the patient. If patients are found to be a candidate for a toric IOL, they suddenly have a decision to make concerning which implant they would like to proceed with. Personally, if a patient has generally good ocular health and about 1.25 D of corneal cylinder or more, we have the “toric discussion.” Even then, I make it clear that they can save themselves the money if being more glasses free is not a priority. This lens upgrade is for patients motivated to have more accurate distance vision after cataract extraction; however, we stress that the patient will still be dependent on near vision glasses and that no lens can promise a truly glasses-free postop.
If a patient shows interest in proceeding with a toric implant, we then discuss the low risk of lens rotation, about 3%, especially in the first week of healing, that may call for a lens realignment if the shift was significant enough to have an impact on vision. Understandably, much like toric contacts, lower-powered toric IOLs are more forgiving of a small rotation compared to higher-powered toric IOLs.
Toric IOLs continue to improve in design and range of powers offered; however, there are still high myopes, hyperopes and astigmats that fall outside the offered range. While the highest 6-D toric IOL only has an effective power of correcting about 4.5 D at the corneal plane, I do recommend this lens for patients with significant corneal astigmatism who will be left with some still uncorrected; I simply educate them that while they will likely need some correction for best vision at both distance and near, it will be optically superior vision than if no astigmatism was treated during cataract extraction.
There are patients I am less excited to recommend the toric lens upgrade for, such as those with irregular corneal cylinder, whether it be from keratoconus, corneal transplant or post-laser vision correction (LASIK or PRK). These lenses should also be approached cautiously in patients with compromised capsule or zonule integrity, like in patients with history of significant blunt ocular trauma or diseases like Marfans. These patients would likely best benefit from spherical monofocal IOLs and an honest discussion that postoperative correction with spectacles, or gas-permeable contact lenses in certain cases, would provide the most stable vision. I may also steer patients away from a lens upgrade if they are amblyopic or have significant concurrent disease such as age-related macular degeneration.
When evaluating a patient for cataract surgery, a good practitioner not only considers the hard data and provides a thorough examination but takes a patient’s personality and visual demands into account. Patient lifestyle, patient expectations and referring OD recommendations are all vital when building a surgical plan, and only then, in the hands of a great surgeon, can these specialty lens technologies provide amazing visual outcomes for our patients.