Toric Multifocal IOL

Overview

As with nearsightedness, astigmatism is a typical form of natural blur in healthy eyes that is remedied by wearing glasses. It is caused by a hereditary, defective optical shape of the cornea, the transparent front window of the eye.

Your cornea should be totally round, but if it is more oblong (like the back of a spoon) rather than spherical, it will misfocus details, causing your natural vision to be blurrier than in people without astigmatism.

The more astigmatism one has, the blurrier the eyesight is without glasses, and astigmatism has no advantage because it adds natural blur to every focus distance. Corrective eyeglasses adjust for this corneal shape in order to optically correct the blur and correctly focus astigmatic eyes.

Although it has nothing to do with cataracts, astigmatism can be decreased or eradicated when cataract surgery is being performed. Doctors can assess the amount of astigmatism correction that your eye should require in eyeglasses following cataract surgery by measuring your corneal shape with a diagnostic method known as corneal topography.

 

What is Toric Multifocal Intraocular lens (IOL)?

Astigmatism is produced by an uneven shape of the cornea, which causes some degree of impaired vision at all distances. Toric intraocular lenses provide focused vision at a single distance while simultaneously correcting astigmatism, so you may not require distance glasses following surgery.

In situations of multifocal intraocular lens (IOL) implantation, precise astigmatism correction during cataract surgery is required. Toric multifocal intraocular lenses (IOLs) provide dependable astigmatic correction after cataract surgery.

The degree of astigmatism correction that is incorporated into the artificial lens that is chosen for your cataract surgery can be determined by your doctor. A toric lens implant is a more personalized permanent lens implant for your eye. The surgeon's skill is vital since the toric lens implant must be positioned in a certain orientation to appropriately neutralize the corneal astigmatism. To check optimal lens alignment, some surgeons use a safe and painless diagnostic tool in the operating room.

The toric lens may not correct all of the astigmatism, especially if it is severe. Weaker glasses can fix any remaining astigmatism. Furthermore, the toric lens, like the normal lens implant, is still a "single focus" lens, therefore reading glasses are still required if the distance eyesight is good.

Toric lens implants, on the other hand, allow suitable people to see better when they are not wearing eyeglasses, and any eyeglasses worn as a result will be less strong. Over-the-counter reading glasses or non-prescription sunglasses, for example, should operate substantially better if your astigmatism is reduced.

The toric lens improves "depth of focus" for astigmatic patients as compared to traditional lens implants. Although it may develop somewhat in certain eyes with age, astigmatism will not disappear on its own, therefore the advantage of the toric lens implant should be permanent.

Toric IOLs are available in cylinder powers ranging from 1.5D to 6.0D. They are typically meant for normal corneal astigmatism in the 0.75D to 4.75D range, with extended series or bespoke IOLs available for higher cylindrical power. Toric IOLs are offered in monofocal and multifocal configurations.

 

Preparation for toric IOL implantation

Cataract patients can now use the Toric Intraocular Lens to reduce or eliminate preexisting astigmatism (IOL). This revolutionary lens design offers excellent distant vision as well as astigmatism correction in a single step.

Previously, patients undergoing cataract surgery only had the choice of a single-focus lens to correct distant vision. However, they would still need to wear glasses or contact lenses to correct their astigmatism. They might sometimes have to have extra treatments to fix their astigmatism. This astigmatism correction is provided in one step with the Toric IOL and is more predictable and accurate.

 

Patient selection

Many individuals have a graduation in which myopia or hypermetropia coexists with astigmatism (and presbyopia). Previously, there was no method to correct astigmatism with intraocular lenses, thus persons with astigmatism who underwent cataract surgery had to continue wearing spectacles or undergo another complimentary procedure, such as LASIK.

For patients with moderate to severe astigmatism, there is now a safe option. Because astigmatism is an optical condition that has a significant impact on vision quality, patients are typically happier when it is corrected with a toric intraocular lens, which allows them to avoid using spectacles.

The patient should have a visibly significant cataract and astigmatism. An excellent applicant will be interested in spectacle independence, even if only for one focus point (usually distance). It should be made apparent to the patient that lenticular correction will be necessary at longer distances (typically near and intermediate). Achieving a satisfactory outcome requires the patient to have realistic expectations. Multifocal/extended depth of focus IOLs are also available, which may aid in lowering spectacle dependence at near and/or intermediate distances.

Patients with a history of trauma or any developmental defect in which the capsular bag support is weakened are not appropriate candidates for these IOLs. These lenses should also be avoided in patients with anterior or posterior uveitis with synechia (adhesions) or poorly controlled inflammation, cases with zonular instability due to any cause, uncontrolled glaucoma, corneal dystrophies, low endothelial cell counts, and complicated cataract surgeries where intraoperative complications are expected.

Another important consideration that is sometimes overlooked during toric IOL design is the angle alpha. Angle alpha is defined as the angle formed between the limbal center and the visual axis. When angle alpha exceeds 0.5 mm, the center of the capsular bag may not align with the patient's optical axis, resulting in unexpected refractive surprises postoperatively.

 

Preoperative evaluation

The modern toric lenses are intended to treat regular corneal astigmatism and are universally recommended in situations with preoperative corneal astigmatism. Before giving a toric lens, it is vital to control expectations and do a thorough ophthalmic examination, since cases of irregular astigmatism caused by corneal scarring or ectasia are not acceptable candidates. Zonular instability, posterior capsular dehiscence, inadequate pupillary dilatation, and previous operations such as vitreoretinal procedures, bucking, and glaucoma implants are all relative contraindications since the intended outcomes may not be obtained.

Accurate biometry is required for exact IOL power computation. The axial length may be determined using either ultrasonic biometry or optical methods. Keratometry estimate is critical for determining the power and axis of the toric IOL. For keratometry estimation, many equipment based on diverse principles, including as manual and automatic keratometers, placido-based corneal topographers, slit scanning systems, Scheimpflug imaging systems, aberrometers, and optical coherence tomography (OCT)-based systems, can be employed.

Taking several measurements and using at least two independent instruments based on different principles can improve the accuracy of keratometry estimate. Toric IOL implantation is a suitable option for cases with a comparable steep corneal meridian on diverse devices. However, if there is substantial fluctuation in the axis and magnitude of the toric IOL on multiple devices, the patient should be assessed to rule out coexisting ocular diseases. In such instances, the visual results may be unsatisfactory.

 

Toric IOL power selection

The surgeon will use the online toric calculator and enter the necessary data. The best model and the lens's axis of orientation will subsequently be determined by the calculator. Surgeons will notice that the toric power varies depending on the degree of primary corneal incision generated astigmatism and the location of the incision.

Surgeons are urged to enter different major incision locations to see how they affect the results. Higher astigmatism powers may be corrected by surgeons who are more flexible about where they make their primary incision.

The spherical power may be determined by the surgeon using standard IOL calculation procedures. Corneal astigmatism will decide which of the two powers is employed. The +2.5 D power is advised for corneal astigmatism of 1.4 to 2.3 D, while the +3.5 D toric is recommended for astigmatism more than +2.3D.

Other online calculators provide the user with a choice of options, including those that produce residual astigmatism on a different axis. When using this calculator, it is critical to confirm the axis direction as well as the power of the indicated toric.

 

How is toric IOL implantation is done?

Prior to commencing the surgical operation, the cornea is precisely reference marked while the patient is erect and facing ahead. It is critical that the patient sits for this treatment since cyclotorsion can develop when the patient lies down.

Following the application of a topical anaesthetic, the cornea is marked at the 3, 6, and 9 o'clock locations. Some surgeons just mark 3 and 9 o'clock. This can be done either in the preoperative area or in the operation room. Corneal marking equipment are available to help with this procedure. This can also be marked using a skin marking pen.

After the patient has been draped, the steep axis should be indicated with a degree gauge to serve as a reference for the orienting markings on the toric IOL later in the process. It is prudent to double-check the axis with preoperative notes. The surgeon then performs the procedure as usual.

In this stage, an ophthalmic viscoelastic device (OVD) is injected into the capsular bag. Cohesive OVDs are recommended over dispersive agents. Cohesive OVDs are less likely to cover the IOL surface and are easier to remove at the conclusion of the case.

At this point, the Toric should be roughly aligned with the ultimate ideal lens position, around 10-15 degrees counterclockwise. After that, the viscoelastic is gently removed from behind the lens and anterior to the lens. If necessary, a second device can be used to secure the IOL in place. Occasionally, the IOL may need to be rotated 10-15 degrees into place during this stage. If not, it is rotated into the ultimate position using a second instrument.

A little shove posteriorly will secure it when properly aligned. This step improves IOL contact with the posterior capsule, lowering the likelihood of postoperative rotation. If the IOL over-rotates, viscoelastic should be injected into the eye and the preceding processes should be redone since it can only be turned clockwise.

The monofocal toric implantation process is similar. When it is inserted into the capsular bag, it should be roughly aligned. Here are some pointers to avoid postoperative rotation. It is vital to remove the OVD completely. Again, the surgeon should pay close attention to any OVD that has become trapped behind the IOL. This increases IOL-posterior capsule contact and reduces unwanted rotation. The company also suggests leaving the eye a little 'softer' than usual.

 

Postoperative care after toric IOL implantation

Keratometry and refraction can both detect residual error. After dilating the eye, examining for markings, and correlating with the intended axis, the misalignment may be confirmed on the slit light. Tracing aberrometers, on the other hand, provide a solid notion of the location of the IOL, the amount of misalignment from the target axis, and how much re-rotation is necessary. Another method for determining the amount of re-rotation necessary is to perform a vector analysis of the misalignment.

IOL instability can be caused by a variety of factors. Typically, lens instability occurs during the first week after surgery. The rotation stability of a toric IOL is determined by its material and design. Because of their adhesive nature, hydrophobic IOLs are determined to be the most stable lenses, followed by hydrophilic, PMMA, and silicone IOLs in that order.

Hydrophobic plate haptic IOLs offer comparable rotational stability to open-loop IOLs, however with silicone lenses, open-loop IOLs have superior IOL stability than plate haptic versions. IOL misalignment should be discovered as soon as feasible since adhesions produced between the bag and the IOL make late surgical intervention and re-rotation of the IOL problematic.

 

What are the benefits of Toric Multifocal IOLs?

This intraocular lens design is distinguished by its ability to correct astigmatism. At the same time, it corrects myopia and hypermetropia as needed. Because it is a monofocal lens, it only covers the refractive flaw at a specified distance, hence this correction is generally fixed for distance. Monovision, like ordinary monofocal lenses, can be used; that is, one eye for distance and the other for close vision.

Toric multifocal intraocular lenses are the appropriate choice for individuals with astigmatism who want to correct their refractive defect in both distance and close vision at the same time.

By repairing astigmatism and cataracts in the same procedure, patients may experience clearer distant vision while participating in activities such as travelling, sports, driving, and other hobbies without the trouble of glasses.

 

Some advantages of Toric multifocal IOL:

• Reduced lifetime cost of glasses and contacts. Toric IOLs can reduce your requirement for reading glasses or computer glasses following cataract surgery. These implanted lenses broaden your field of vision, allowing you to see well up close and far away without the use of glasses. Many patients who select multifocal IOLs discover that they may go glasses-free or only need reading glasses occasionally for tiny text after surgery.
• More freedom to live actively and unencumbered. Multifocal IOLs increase close, midrange, and far-distance vision, depending on the lens type used. In many situations, after having the lenses implanted, patients no longer need to wear corrective glasses to see well.
• No upkeep or routine replacement necessary. The effects of multifocal IOLs are long-lasting. Unlike contacts, multifocal IOLs are implanted inside the eye and do not require any further maintenance or replacement. 

 

What are the complications of toric IOLs?

Cataract surgery is one of the most routinely done operations in the United States. The treatment is conducted under local anesthetic in an outpatient surgical center and takes only a few minutes to complete. However, it is critical to remember that any medical operation may result in unanticipated consequences and that outcomes cannot be guaranteed. Even with our best efforts, some patients may require little correction to strengthen their vision.

Toric IOLs have a few additional possible risks, in addition to the standard difficulties connected with cataract extraction and intraocular lens installation procedures. Astigmatism might be cured too much or too little.

The toric IOL may spin off-axis. If it spins off-axis, it will have a partial impact. For example, for every 3o spin off-axis, the toric's corrective effect is diminished by 10%. The lens would have to be 30o off-axis in order to lose its full impact. Complete excision of OVDs, particularly those posterior to the IOL, is necessary to prevent IOL rotation.

Halos or other extra visual side effects are not introduced by toric lens implants. They do not change the way cataract surgery is conducted and do not significantly extend the operative time. Despite the fact that the surgical recovery is the same, individuals with astigmatism see better with toric lens implants during the early postoperative period when they have not yet gotten new prescription eyeglasses.

 

Will I still need eyeglasses with a toric lens implant?

The toric lens implant does not allow you to read and see far away without glasses. It may not fix all of your astigmatism. However, as compared to a normal lens implant that does not correct astigmatism, the toric lens implant should enhance your ability to see without glasses, and any glasses you do need should be less strong and perhaps more comfortable to wear.

Every artificial lens implant model (both standard and toric) is available in more than 60 different "powers," similar to contact lenses or spectacles. It is critical to match the right artificial lens implant power to your eye, just as it is with prescription eyeglasses or contact lenses.

Doctors use trial and error to evaluate several lens strengths in front of your eye to prescribe the proper spectacle or contact lens power. When asked "which is better, one or two?" "During an eye test, you choose the lens power that allows you to see the best. However, because the artificial lens implant is only implanted within the eye after your natural lens (cataract) has been removed, you cannot preview or "test out" different powers while the procedure is still in progress.

Obviously, doctors cannot install more than one lens implant in the operating room to allow you to choose which one provides the greatest distant focus. They also cannot adapt to a different lens implant power later on, like contact lenses may.

 

How much does Toric Multifocal IOL cost?

Toric lenses, on the other hand, come at an added expense. Cataract surgery with a typical lens implant is covered by insurance. The extra expense for implanting toric lenses, on the other hand, is not reimbursed and must be paid for by the patient out of pocket. Keep in mind that the advantages of toric lens implants are that they improve your natural eyesight without the need of spectacles. They are not "medically required" since they do not improve your eye health.

The cost of intraocular lenses varies depending on the doctor and the area. As a result, quoting a "one size fits all" pricing is problematic. The average cost of a premium intraocular implant in 2017 was $1,415 per eye. Make an appointment with Eye Health Partners to get a precise quotation.

 

Conclusion

Astigmatism is a prevalent eye disorder that affects a large number of people. When this astigmatism becomes moderate or severe, it might cause blurred or impaired vision. The reason of hazy and impaired vision is an uneven shape of the cornea or lens of the eye. The cornea and lens of a normal eye are circular in shape, but the cornea and lens of an astigmatic eye are longer and more oval in shape.

Toric intraocular lenses (IOLs) are a safe and successful surgical approach for precisely correcting astigmatism. For successful postoperative outcomes, adequate knowledge of the science behind using these lenses, appropriate case selection, meticulous preoperative measurements and planning, robust intraoperative surgical steps, and early postoperative recognition of IOL misalignment should be followed rigorously.

Even when the goal refraction power is judged to be myopia, the use of a toric IOL is preferable to a monofocal IOL for both near and distance vision in cataract patients with astigmatism. This might be useful when an ophthalmologist consults with a patient.