Small-incision toric lens surgery helps to reduce astigmatism

October 15, 2013

Kevin Lavery, MD, describes his technique for implanting a 1-piece acrylic astigmatic lens (Tecnis Toric IOL, Abbott Medical Optics) through a 2.2-mm incision or even smaller.

Take-Home

Kevin Lavery, MD, describes his technique for implanting a 1-piece acrylic astigmatic lens (Tecnis Toric IOL, Abbott Medical Optics) through a 2.2-mm incision or even smaller.

Dr. Lavery

By Kevin Lavery, MD; Special to Ophthalmology Times

Battle Creek and Jackson, MI-The trend in cataract surgery toward smaller incisions is an important one. By making smaller incisions, ophthalmologists can reduce the amount of surgically induced astigmatism (SIA) and promote faster visual recovery.

In contemporary cataract surgery, results have already become so refined that reducing both the magnitude and standard deviation of SIA is critical to perfecting results in all cases. It is particularly relevant when implanting a premium toric IOL that is intended to neutralize astigmatism and provide excellent uncorrected distance vision.

However, in the rush to small-incision surgery, it is important to make sure that all components of the procedure can be performed effectively through the small incision-from lens disassembly and phacoemulsification to IOL insertion and positioning.

Additionally, when implanting a toric lens, one wants to be certain the lens can be easily positioned on the correct axis and that it remains stable postoperatively.

Small-incision technique

As seen in the accompanying video, we have recently been very successful in implanting a new 1-piece acrylic astigmatic lens (Tecnis Toric IOL, Abbott Medical Optics) through a 2.2-mm incision or even smaller.

Preoperatively, reference marks are critical, especially if one does not use a device for intraoperative imaging and axis placement.

I use a Mastel marker to mark the cornea at 3 and 9 o’clock with the patient sitting upright and fixating on a target. I make a 2.2-mm temporal incision as posteriorly as possible without getting into conjunctiva, because that posterior position also reduces SIA.

Although I will occasionally move the incision to the steep axis, I find that a consistent and ergonomically comfortable hand position for wound creation is actually more important to the predictability of SIA than always making an on-axis incision.

I use a pre-chop technique.

In this case, I removed the cataract without incidence using a phacoemulsification system (Infiniti, Alcon Laboratories) and a 45° curved Kelman phaco tip.

I like the Unfolder Platinum 1 injector for the Tecnis Toric lens, because the tip of the inserter cartridge fits nicely into a 2.2-incision. With other 1-piece toric lenses, the insertion requires more wound assist-which can stretch the incision.

Once the lens is loaded in the injector, my technician uses a Sinskey hook to tease out the leading haptic.

Positioning the haptic

It is important that the haptic be positioned in a “candy cane” configuration-not straight. That slight bend protects the haptic and puts it into the right orientation with the plane of the lens so that everything follows in behind it smoothly.

There are a few advantages to pulling the leading haptic out before insertion.

> First, it “thins out” the lens profile so that it injects more easily through my small incision.

> Secondly, by having the haptic stretched out it leads directly into the bag, rather than the sulcus.

> Finally, this ensures a very consistent insertion because it is almost impossible for the haptics to stick to each other or to the lens optic.

After injecting the lens, I will begin to rotate the lens clockwise toward my desired axis.

However, for some axes (such as 180°), I will actually rotate counterclockwise a few degrees before the haptics have fully extended. This counterclockwise maneuver prior to the opening of the haptics saves time.

I cannot stress enough the importance of removing all the ocular viscoelastics under the lens before final lens positioning.

For final lens positioning, a two-handed, but single-instrument technique has worked well.

I use a 5-cc syringe filled with balanced salt solution and antibiotic drawn from the bottle and topped with a square-tip hydrodissecting cannula.

With the cannula in one hand and the other hand on the plunger, I “walk” the lens into position and am able to move the whole lens if necessary or rotate either pole of the haptics independent of each other.

This maintains the chamber-creating a very stable environment while I precisely seat the lens.

I prefer this over a typical two-handed technique with irrigation in one hand and an instrument in the other.

Having two instruments in the eye increases the potential for the lens to “jump.”

Moreover, the dimpled markings reflect the microscope light almost like a roadside marker, making it very easy to visualize the whole lens simultaneously and quickly position it in the eye.

Postoperatively, the IOL looks beautiful in the eye. As I have found with other lenses in the Tecnis family of IOLs, the acrylic material stays clear and true, with no anterior scuff marks on the lens after insertion.

Published data from Tecnis Toric clinical trials corroborate my impression that this lens is very stable, with minimal rotation.

I believe that ophthalmologists will be able to inject the lens through an even smaller incision of 2 mm, or even 1.8 mm.

In initial attempts, the limiting factor is actually not the lens or the inserter, but the instrumentation.

For example, Utrata forceps that are designed for a 2.75-mm incision can create wound lock in a small-incision environment. In order to truly move to microincisions, surgeons may need to make a number of instrumentation changes.

Better results are good for patients and practice

The potential to control SIA more precisely and the accuracy of the refractive result with small-incision toric IOL surgery are exciting advances.

In my opinion, toric IOLs represent the easiest entry point to becoming a premium IOL surgeon.

Patient expectations are not as high as they are in multifocal IOL cases. The Tecnis Toric IOL is not technically demanding to implant and ultimately, very forgiving.

Patients are generally thrilled with their brighter, clearer vision and ability to see without glasses after surgery.

Surgeons have long realized the results with higher-powered toric IOLs for patients who would otherwise have very poor uncorrected vision.

Many surgeons underestimate the value of toric IOLs to patients with lower levels of astigmatism, perhaps reasoning that those patients can achieve a pretty good result without paying for a premium IOL.

Though it is true that a patient with low astigmatism may achieve a 20/40 result with a non-toric lens, a toric IOL can make the difference between spectacle independence and reliance on glasses.

Currently, at least 30% of my cases involve a toric IOL.

I now recommend a toric IOL for ≥0.87 D against-the-rule astigmatism and for ≥1.0 D of with-the-rule astigmatism.

Continuing to reduce the “noise” in results with a consistently low magnitude and standard deviation of SIA will drive better outcomes and greater patient satisfaction at all levels of correction.

 

Kevin Lavery, MD, practices at TLC Eyecare and Laser Centers in Battle Creek and Jackson, MI. Readers may contact him at 517/782-1213 or lavery.tlc@gmail.com. He did not indicate any financial interest in the subject matter. 

 

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