Toric contact lenses are lenses designed in geometric or torus shape in the form of a donut, specially made for correcting astigmatism. Toric lenses create various refractive or focusing powers vertically and horizontally. In astigmatism, In astigmatism, the corneas lack a rounded shape, which makes light bend in a way that hits multiple spots on the retina as opposed to just one. This can lead to blurry vision. This is where these cylindrical lenses play an important role.
This guide breaks down the origin, material, stabilization of Toric lenses. It also went on to elucidate the wear time, cost, technology advances, Durability, regulation, and Corrective Ranges of toric lenses.
Origin of Toric Lenses
The invention of toric lenses dates back to the early 1970s. Warby Parker’s article states that in 1971, Bausch & Lomb pioneered toric lens technology by manufacturing the first U.S. commercial soft contacts. Later in the 1970s, two notable types of soft contact lenses were introduced to wearers: toric lenses and extended-wear contacts.
In 1978, the Food and Drug Administration (FDA) approved toric contact lenses. These lenses correct astigmatism, including myopia (nearsightedness) and hyperopia (farsightedness), which have already been corrected by contact lenses.
Key Principle of Toric Lenses
Toric Fitting Methods
Toric lens fitting is important because of the orientation and need to stay correctly in your eyes. They require precise fitting by an eye doctor to ensure proper alignment with the cornea for effective astigmatism correction. They have a middle axis, like the Earth’s equator, which makes your vision line clear. When your toric lenses don’t fit well, they slip, including the visual clarity.
Step 1
Start with new spectacle refraction and add power. Choose initial trial lens power according to the spectacle to contact lens power conversion table. Select the trial lens axis closest to the spectacle axis.
Step 2
Fix the trial lens into the wearer’s eye. Allow the contact lens to settle for about 10 minutes before evaluating the contact lens fit and visual acuity.
Step 3
Evaluate the success of the lens to
- Finalize axis orientation
- Determine the distance and near vision binocularly, especially in room illumination.
- If visions at distance and near are acceptable, dispense lenses and fix the follow-up exam within 1–2 weeks.
Materials for Toric Lenses
Toric lenses are often made from one of two materials, which are:
- Hydrogel
- Silicone hydrogel
Silicone hydrogel lenses provide more breathability than hydrogel contacts and can be a bit more costly.
Unlike the regular soft lenses that correct farsightedness and nearsightedness, toric lenses focus on various parts of the lens to correct the nearsightedness or farsightedness that goes along with astigmatism. They are also designed to allow them to rotate to the perfect angle on the front of your eye.
Finding a perfectly fitting toric lens that provides comfort and visual sharpness requires some trials. This is because each eye with astigmatism is different.
Gas permeable lenses
People use gas-permeable lenses to correct astigmatism. GP lenses can correct astigmatism without a specialized toric design due to their rigid nature. They retain their shape on the eye’s misshapen surface instead of conforming to the surface like soft lenses do.
The only gas-permeable lenses with toric designs are those prescribed for high or unusual levels of astigmatism.
Stabilization
The stabilization of toric lenses is important because it enhances better vision, which needs a fixed cylinder axis in the right place; it also minimizes the lenses from rotating.
Stabilization of toric contact lenses can be achieved by the following methods:
- Prism ballast
- Truncation
- Double Slab-off
Prism Ballast: Eye care professionals commonly use prism ballast for stabilization. A prism of between 1.00 and 1.50 D is ground at the base down part of the lens for the base of the prism to be thicker. This reduces oxygen permeability through the portion of the lens, leading to hypoxic disturbances in the inferior area of the cornea. Much quantity of prism may be needed for users with tight lids, flat corneas, or oblique axis astigmatism, especially.
Truncation: In truncation of lenses, a portion of the lens is sliced off. This is mostly 0.50 to 1.5 mm on the bottom of the lens. This sliced-off portion forms shelves that rest upon and align with the lower lid. It stabilizes lenses with thick edges, mostly when joined with prism ballast. The portion that is sectioned off is determined by the size of the lens; smaller lenses require smaller portions than larger lenses. Double-truncated lenses can be gotten by sectioning off the upper edge. When lenses are truncated, their diameter is decreased, which results in a looser fit.
Double Slab-off lenses: In this technique, superiority and inferiority thin zones are made. The lens is thicker along its central body, which lies within the palpebral aperture, and thinner along the inferior and superior edges, which come to lie under the upper and lower lids. There is no lid impact along the inferior surface, which makes the technique comfortable. Double slab-off does not provide as much lens stability as the truncated techniques. To prevent rotation, these lenses are combined with prism ballast.
Wear Time of Toric Lenses
The wear time of your toric lens depends on the type of lens. Lenses designed for daily or one-time wear may be worn for about 14-to-16-hour time frames. On the other hand, for the purpose of resting the eyes, an eye care professional may advise you to remove your contacts for one or two hours before retiring for the night, which means less time to wear them.
Toric lenses provide flexibility and are available for various wear times, such as daily, weekly, and monthly. They are designed to correct your astigmatism. Always ask your eye doctors to know the best wear schedule lenses for you. In case of irritation, report it to your eye doctor.
Popular Brands
- Kiama cosmetics
- Alcon
- Johnson & Johnson vision care
- Coopervision
- Bausch + Lomb
- SynergEyes
- Essilor Contact Lens
- Acuvue Oasys for Astigmatism
- Air Optix
Cost of Toric Lenses
The price of toric lenses is determined by various factors such as frequency of wear, brand, etc. Daily disposable contacts are more expensive than biweekly and monthly disposable lenses. Spherical lenses, which are non-toric and used for nearsightedness or farsightedness, are less expensive than toric lenses used for correction of astigmatism.
An article written by Warby Parker suggests that contacts for astigmatism cost about $30 to $120 per month and $300 to $800 per year. Eye Q Premium Laser in their article wrote that premium toric lenses, like multifocal toric lenses, or astigmatism correction cost about $100-$150 and above.
Uses of Toric Lenses
Toric contact lenses are used to correct astigmatism defects that happen due to different curvature of the cornea or lens in the eyes, also known as regular astigmatism, corneal astigmatism, or lenticular astigmatism. The use of toric lenses provides different refractive or focusing powers on the vertical and horizontal alignments to help the eyes see clearly.
Combination of astigmatism with other refractive errors, such as myopia or hyperopia, can lead to blurry vision, etc. With toric contact lens prescriptions that are customized, it enhances clarity for individuals with complex visual needs created by a combination of refractive errors.
Toric lenses have to be well fitted for full correction. To get your toric lens rightly fitted, your eye doctor has to be knowledgeable in hard-to-fit eyes.
Technological Advances
The advanced toric lenses for correction of astigmatism provide better stability and vision correction. They are designed to be stable, reducing the need for frequent adjustments.
This advancement in lens materials used in manufacturing them has also improved the comfort of toric lenses. The advancements have also offered the availability of a wider range of prescriptions, making it easier for individuals with astigmatism to find the perfect fit.
Eye Health
To ensure duration and also maintain your eye health, it is important to care for and maintain your toric lenses. Follow these necessary care and maintenance advice:
- Before touching your lenses, always wash your hands with soap and water and then dry them with a lint-free towel.
- Use the approved lens solution by your eye care professional to clean and disinfect the lenses after each use.
- Avoid using tap water or saliva to clean the lenses. Because they contain bacteria and harmful microorganisms that can lead to eye infections.
- Your toric lenses should be kept in a clean case with fresh solution, and replace the case often to avoid bacterial contamination.
- To prevent blurry vision, ensure there are no bubbles in the lenses.
Limitations of Toric Contact Lenses
There are some limitations linked with the use of toric lenses. These include:
- Toric lenses are limited due to their rotation issues. They can rotate out of alignment, which can cause blurred vision. A toric lens is made to align with the astigmatic axis of the eye. This misalignment is mostly caused by the blinking of the eye or the lens design.
- It is more difficult to have or achieve a right fit using toric lenses than spherical lenses. This happens because the lenses need to align with the astigmatic axis, which varies among individuals. Incorrect fit of the lenses can cause vision problems and discomfort.
- The cost of toric lenses is more expensive than standard soft contact lenses. This is because of the complexity in their manufacturing processes and designs.
- Toric lenses have fewer options than spherical lenses. This includes fewer options of materials, replacement schedules, cosmetics, and colored lenses.
Corrective Range
The American Academy of Ophthalmology published an article stating the corrective range of toric lenses. The article stated that toric IOLs are different from spherical IOLs because of their different powers in different meridians. When a toric IOL of the right cylinder power is inserted into the eye and rotated into the correct axis, it can correct the wearer’s corneal astigmatism.
Also, the cylinder power of a toric IOL has a spherical power. Axial length, average corneal curvature, and the most current IOL formula, the anterior chamber depth, are used to calculate the spherical power in a toric IOL. The spherical power of a toric IOL is the same IOL power that would be used for the eye if astigmatism was not being corrected.
Toric IOLs are available with cylinder powers ranging from 1.5 D to 6.0 D. These lenses provide astigmatism correction of 0.75 D to 4.75 D at the corneal plane. The spherical power and cylinder power of a toric IOL are both indicated in the description of a toric IOL.
Availability of Toric Lenses
Toric lenses are available in online stores such as Kiama Costmestics, Amazon, etc., and your eye care professional. Extensive varieties of toric lenses from Acuvue, Johnson & Johnson, Alcon, Bausch + Lomb at very affordable prices are available at Kiama Costmetics. You can access the online store globally.
Durability
Toric lenses are durable with the use of rigid gas permeable (RGP) materials. They are made from firm, oxygen-permeable material, which allows visual clarity. Because of their rigid nature, RGP lenses offer a more accurate correction for astigmatism and also stability on the eye. RGP toric lenses are beneficial due to their longevity and durability. They can last longer than soft toric lenses, making them a cost-effective option for you. Durability of toric lenses allows extended wear, longer usage time.
It’s important to seek the opinion of your eye care professional to determine the best type and material of toric lenses for your specific needs. Factors such as the condition of your eye, how severe your astigmatism is, and your lifestyle preferences will be considered by your eye doctor to recommend the best option for you.
Alternatives to Toric Lenses
- LASIK
- Refractive surgery
- Intraocular lenses such as toric IOLs and multifocal IOLs
- Corneal Reshaping Treatment
- Implantable Collamer Lens (ICL)
Legal and Regulatory Information
In summary, the Food and Drug Administration (FDA or the Agency) has determined the regulatory review period for LIGHT ADJUSTABLE LENS and is publishing this notice of that determination as required by law. FDA has made the determination because of the submission of applications to the Director of the U.S. Patent and Trademark Office (USPTO), Department of Commerce, for the extension of a patent that claims that medical device.
An article by the American Academy of Ophthalmology stated that “the Federal Food, Drug, and Cosmetic Act prohibits false and misleading advertisements for restricted medical devices, including Federal Drug Administration (FDA)- approved lasers used for LASIK surgery. Advertising that is literally true but that conveys a misleading impression to reasonable consumers may be unlawful. Deception can also occur through the omission of information if the absence of the information causes the advertisement to convey an inaccurate impression about a material fact, one that is likely to affect consumer conduct or decisions with respect to the service or product at issue. Thus, ophthalmologists should ensure that statements made directly or by implication in informational, promotional, and advertising materials are accurate and are not likely to deceive consumers. This is especially true in testimonial ads. Ophthalmologists are responsible for unlawful or deceptive claims made during testimonials that are used in their promotion and advertising materials. In addition, the FDA’s premarket approval orders might contain certain conditions of approval that could include requirements that physicians or companies provide specific risk information in promotional materials.”