Brian Johnson, OD
PCLI—Kennewick, WA

Toric intraocular lens implants (IOLs) are designed to correct astigmatism and were first approved by the FDA in 1998. Now several options are on the market—with more on the way. Although surgeons at PCLI first started using toric IOLs in about 2001, we have been implanting them more frequently over the last 2 years. Based on our success, I encourage you to consider toric IOLs for appropriate cataract and refractive lens exchange (RLE) patients.

Toric IOLs are a valuable tool we can use to reduce dependence on glasses and contacts—which is becoming increasingly important to patients. Limbal relaxing incisions (LRI) are sometimes used to treat smaller amounts of corneal astigmatism, but this can often be more accurately corrected with toric IOLs. These implants have given us a greater ability to correct astigmatic refractive errors in conjunction with cataract and lens exchange surgery.

The lens we currently prefer is the AcrySof Toric IOL by Alcon. It is available in three astigmatic powers: 1.5, 2.25 and 3.0 diopters. These powers correlate to about 1.0, 1.5 and 2.0 diopters of correction at the corneal plane. In FDA studies, 97% of patients that had this lens implanted bilaterally achieved spectacle freedom for distance vision.

We share the following strengths and limitations with patients interested in toric IOLs:

Strengths

• Predictability of correction
• Excellent quality of vision
• Independence from glasses for many activities
• Options of monovision, or partially treating higher astigmatism

Limitations

• Glasses are generally needed for either near or distance vision and sometimes both
• Can only correct certain amounts of astigmatism
• May require additional surgery to optimize IOL position
• More exams are required
• Extra costs are involved

It is important to note that toric IOLs are special order lenses, so “same-day surgery” at PCLI may not be an option. Patients usually need to be evaluated at our clinic prior to ordering the toric IOL. There is a rare chance that the lens could rotate off axis enough so that visual expectations are not met. This may require further surgery to reposition the lens implant. After a few weeks of healing, rotation is very unlikely.

When determining if patients have enough astigmatism to warrant toric IOLs, it is important to analyze their K readings. Pre-op corneal cylinder is usually a good predictor of the post-op refractive astigmatism.

Toric IOLs can also be a great option for patients with more astigmatism than the highest powered lens (3.0 D) can fully correct. We have seen people benefit from significantly reduced spectacle astigmatism correction.

Cylinder power and optimum axis are determined with the help of Alcon’s online calculator. Click here to see sample printouts. AcrySof Toric IOLs have marks inscribed on the peripheral optic which need to be aligned with the calculated post-op steep axis of the cornea. They can easily be identified by retroillumination after pupil dilation. After surgery, the implant can be confirmed as “on axis” by rotating the slit-lamp beam to align with these markings.

Significant rotation “off axis” may result in a loss of effective cylinder power.

Misalignment	Effective Cylinder Power
10 degrees	1/3 loss
20 degrees	2/3 loss
30 degrees	Complete loss

Misalignment of more than 30 degrees will start to increase the total astigmatism.

Post-op care is essentially the same as for standard cataract surgery with a spherical IOL.

• Analyze patient satisfaction
• Measure uncorrected distance visual acuity
• Perform manifest refraction

At the 3-10 day visit, dilate and confirm toric IOL axis alignment. If vision does not meet the patient’s expectations and the toric IOL is significantly misaligned, surgical rotation is best done within 1-2 weeks of the initial procedure. (In the absence of symptoms, dilation with IOL check and retinal check at the 3-10 day visit can take the place of the dilation you normally include in your 4-6 week post-op exam.)

Our experience with the toric IOLs has been very positive. As lens implant options continue to expand, it is important to educate patients on alternatives that can improve their lifestyles. You can increase the value of your service by providing expert advice and guidance. As always, if you have questions regarding these lenses or any other aspect of eye care, please feel free to contact us.