#3 of 10: Top Reasons for Poor Premium IOL Outcomes and How to Remedy Them: Managing AstigmatismThe ultimate goal in obtaining the premium outcome with a premium IOL requires mastering how to set patient expectations, how to perform the ideal preoperative evaluation (Blogs 1 and 2 in this 10 part series) and even more importantly how to address and treat astigmatism.
It is essential to differentiate between corneal and lenticular astigmatism because the lenticular component will go away with cataract surgery.
Sometimes the lenticular component cancels out the corneal component, sometimes there is no lenticular component, and sometimes it can be additive to the corneal cylinder that exists preoperatively.
Corneal topography and/or the use of a device such as the Marco OPDIII will help distinguish between corneal and lenticular astigmatism preoperatively so your surgical plan can be accurate.
The next hurdle is to decide how to upgrade your patient: toric IOL or a presbyopia correcting IOL with limbal relaxing incisions (LRIs) and/or secondary laser vision correction (LASIK/PRK).
In the USA there is no FDA approved presbyopia correcting IOL that simultaneously corrects for astigmatism, so it really becomes the surgeon’s responsibility to do a thorough preoperative lifestyle analysis of the patient.You’ll want to determine which IOL option will satisfy the patient for most of the 365 days of the year and not just for the one week fishing trip for example.
For those patients with moderate to high astigmatism preoperatively, the bad news is it can be difficult to correct all of it even with LVC/LRI combo, but the good news is the Alcon Acrysof IQ toric IOL, especially with its new recently expanded FDA approved range for treatment of corneal astigmatism up to 6 diopters at the IOL plane and 4.11 diopters at the corneal plane, should be able to do the job. Remember to use the vector analysis calculation for toric IOLs at www.acrysoftoriccalculator.com.
If the decision is to proceed with a presbyopia correcting IOL, then preoperative corneal astigmatism needs to be addressed. In my experience uncorrected astigmatism 0.75 D or greater will usually reduce near and/or intermediate vision results by 2 or more lines. LRIs are a quick and easy procedure that can be performed at the time of cataract surgery or at the slit lamp postoperatively.
If there is ≤0.75 D cylinder preop consider performing an on-axis corneal cataract surgical incision is if the steep astigmatism axis is within 15° of the intended incision.
If the astigmatism axis is outside 15° from the intended incision, place the main surgical incision where comfortable and perform LRIs.
For 0.75-1.50 D cylinder, perform intraoperative LRIs.
For cylinder ≥1.50 D consider intraoperative LRIs to “debulk” astigmatism along with postoperative laser vision correction.
AMO provides a great tool at www.lricalculator.com that provides the necessary adjustment for vector analysis. Various LRI nomograms such as the “DONO” nomogram (Eric Donnenfeld, MD) and “NAPA” nomogram (Louis “Skip” Nichamin, MD) at www.mastel.com/pdf/napa.pdf adjust further for age and pachymetry readings.
I prefer to do my LRIs at the slit lamp with an angled diamond blade preset at 500-600 microns (Accutome) for any postoperative fine tune adjustments rather than bringing the patient back to the OR. The Wavetec Orange device provides for additional real-time intraoperative refinements for either toric IOL positioning and/or for extending or redeepening LRI incisions.
Another option for correcting residual astigmatism is Laser Vision Correction (LVC) and the timing of such should be based on refractive and topographic stability, typically requiring 3 months but no less than 1 month in my experience. PRK may be the preferred method for LVC in patients with corneal epithelial dystrophy and/or thinner corneas. You will find that most LVC “enhancements” with good preop biometry will usually be mixed astigmatism, thus avoiding the need for most costly wavefront treatments.
In the end, untreated corneal astigmatism is detrimental to the premium outcome. Proper patient expectation, proper preoperative evaluation, and proper astigmatism management are the first 3 solutions required for the proper premium result.
Stay tuned for managing posterior capsular opacification in my next blog. I’ll discuss the best timing for Yag treatments, especially in the presence of untreated corneal astigmatism.
Click Here to read the first installment of Dr. Jackson’s series or Here for the second installment.
