Introduction  

Toric lens is a foldable, single-piece lens used to correct regular corneal astigmatism at the time of cataract surgery. Cataract surgery removes a clouded lens that has failed to focus light rays on the retina. With a cloudy lens, the patient’s vision can look hazy, less colorful and blurry. Toric lens is categorized as an intraocular lens (IOL). An IOL is a small, artificial lens that replaces the natural lens of the eye in cataract surgery. 

Astigmatism refers to a refractive error caused by the abnormal curvature of the cornea or lens. Usually, the cornea and lens are smooth and curved equally in all directions. The unevenly curved cornea or lens prevents light rays from bending correctly giving rise to astigmatism. However, the patient with both cataract and astigmatism may not regain high-quality distance vision unless laser surgery is performed. 

Toric lens is made of silicone or acrylic. It helps to protect the eye from the harmful ultraviolet (UV) rays of the sun since it’s lined with special protective material. It’s not recommended for people who have had refractive surgery because the toric lens’ power calculations may not be precise enough to address astigmatism. The lens can be implanted in one eye if only one eye is affected by astigmatism and cataract.

The eye doctor will calculate the spherical power required for each patient’s toric lens. The doctor measures the length of the eye and the cornea’s curve using a special calculator. For example, for Alcon AcrySof models, the surgeon can input the required information into an online toric calculator at www.AcrySofToriccalculator.com. The calculator determines the best model and axis of orientation of the lens. Patients with irregular astigmatism may not fare as well as those with regular astigmatism.

Types

The following are the available brands of toric lens:

  • AcrySof Toric IOL - It is an aspheric, one -piece hydrophobic lens
  • Staar Toric IOL - It is made from a silicone plate
  • AMO Tecnis Toric IOL - It is a one-piece design aspheric hydrophobic acrylic lens
  • Trulign Toric IOL - It is an aspheric silicone IOL

 

Purpose

Toric lens replaces the clouded natural lens during surgery. The clear, toric lens comes with new corrective power that allows rays to focus light on the retina which in turn provides clear vision. The toric lens also significantly improves uncorrected distant vision. The lens, to a large extent, reduces the dependence on eyeglasses and contact lenses.

Side Effects

Because implantation of a toric lens is a form of cataract surgery, complications, risks and side effects may arise such as:

  • The toric lens may not be able to correct all the astigmatism. However, it should be able to fix most of it. Patients may still need glasses for reading or close vision activities such as driving, cooking, etc. 
  • Displacement of the toric lens can occur. The doctor will need to perform another surgical procedure to reposition, exchange or remove it leading to further risk.
  • Patients may experience vision distortion such as blurry or double vision.
  • Inflammation (swelling) of the eye may result which may lead to further eye complications.
  • Retinal detachment. Retinal detachment is the pulling away of the retina from its normal position. This can result in severe loss of vision if not treated.
  • Eye pressure may increase which can lead to glaucoma. Glaucoma is a severe eye disease that can cause loss of vision or total blindness.
  • Bleeding and infection could arise with serious ramifications such as loss of vision.

 

Overcorrection

It is possible that the toric lens may over correct astigmatism. Overcorrection means the patient receives a toric lens with more power than required. This may lead to complications such as eye-straining, blurry vision and the need for a second surgery.

Storage

Toric lens is stored in a vapor-permeable package,  a relatively dry environment and at room temperature. Research shows that the environment in which the lens is stored is crucial for its effectiveness. One study concluded that spraying an environment where the lens is stored can cause surface changes to the lens. The lens should be moved to a safer environment without chemicals.