9th July 2015
Toric Lens Implants
Are you noticing heightened visual demands in the newest generation of cataract patients? I certainly am. More than ever, patients are anticipating great uncorrected vision after surgery. And like never before, they are involved in choosing IOLs that match their lifestyle. At Pacific Cataract and Laser Institute, the most common lifestyle lens implant that patients select is the toric IOL—which is a great option.
We’ve Come a Long Way
When I started my career in optometry fresh out of SCCO in 1984, phacoemulsification was utilized in less than 10% of cataract surgeries. In the early days of phaco, a successful outcome was:
- a can-opener capsulotomy without capsular rupture
- a sulcus placed IOL
- a sutured wound
- a post-op refractive error with less than 2 diopters of astigmatism
- and an equivalent sphere of plus or minus 2 diopters.
But it was a huge step forward from intracapsular cataract surgery and post-op aphakia. By the time I joined PCLI in 1990, the use of phaco in cataract surgery had jumped to 50% of cases nationwide.
A huge improvement!
As surgery techniques and IOL technologies have advanced, so have patient expectations. Today, many of the cataract patients I see before surgery in our Anchorage office expect freedom from glasses. They often know someone who has had laser vision correction and anticipate a similar outcome. Of course, their lost accommodation makes it impossible for us to match the vision a 30-year-old enjoys from LASIK, so we carefully dial back expectations and offer lens implant options that can help.
Multifocal IOLs can be a good option for carefully selected patients, but they cannot be used for anyone with a significant amount of astigmatism. Although a toric multifocal has been winding its way through FDA trials for several years, it is not yet on the market.
I believe we often help our patients most by providing good uncorrected distance vision—and single vision toric IOLs are a great asset in our tool box.
The toric implants we use reduce corneal astigmatism by 0.69 – 4.11 diopters. Although they are not produced in 0.25 D increments, the intervals reduce astigmatism enough to make patients functional for most visual tasks. As with toric contact lenses, it is wise to educate patients that toric IOLs will reduce astigmatism but may not give perfect 20/20 uncorrected vision. With the proper counseling, most patients are happy with their uncorrected distance vision. But they must understand that they will likely benefit from glasses for some activities.
Toric IOLs may be a good choice for patients if:
- They are interested in reducing dependence on spectacles—even if only for one distance (usually far)
- Corneal astigmatism (which may be different than refractive astigmatism) is greater than 0.75 and less than 4.50 diopters
- Their astigmatism is regular
Toric IOLs will be more challenging for patients with uncertain corneal measurements due to:
- Previous keratorefractive surgery — Precise corneal power measurements and IOL calculations are difficult to obtain, but previous surgery does not rule out toric IOLs.
- Long history of rigid contact lens wear — As years of contact lens wear can mold the cornea, they must be left out for weeks and sometimes months until corneal curvature returns to normal.
- Significant ocular surface disease — Measurements can be distorted from chronic epithelial irregularity. Addressing the disease well ahead of cataract surgery will sometimes resolve the problem.
Toric IOLs are not a good choice for patients with:
- Irregular astigmatism from corneal ectasia or corneal scars
- Progressive or unstable corneal conditions
- Uncertain or inaccurate axial length measurements — This is usually due to very dense cataracts or very long or short axial lengths.
- Unstable capsular bag or zonular problems — To be effective, toric IOLs need to be placed in a stable capsular bag so zonular dehiscence, phacodonesis, or significant pseudoexfoliation are contraindications.
- Intraoperative capsular ruptures or tears
After-surgery care for patients with toric IOLs is the same as with single-focus lens implants, except that the lens axis needs to be checked during the first month. In about 3% of our cases, the IOL will rotate off axis enough to consider repositioning. This usually occurs within the first week.
Keep in mind that toric IOL positioning is not a perfect science. Even when the post-op axis is off the planned target, the patient may see well and be happy. But when the IOL has moved enough to decrease vision, it can usually be rotated back to the desired position. After a month, the capsular bag is typically scarred enough around the lens haptics that rotation is rare.
At Pacific Cataract and Laser Institute, toric lens implants have proven to be an excellent option for properly selected candidates who are realistic in their expectations. They help many cataract surgery patients reduce dependence on spectacles. As with all IOLs, a successful outcome is typically a refractive error of less than 0.75 diopters of astigmatism and an equivalent sphere of plus or minus 0.75. Patients do not always achieve 20/20 uncorrected visual acuity, but an outcome in this range typically provides uncorrected vision better than 20/40.
Regardless of the numbers, patient satisfaction is the ultimate end point for determining surgical success.
Call With Questions
If you have questions about toric IOLs, or wish to discuss a specific case, please feel free to call any of our optometric physicians. We are always happy to help.