Corneal astigmatism, a condition that many patients present with, is caused by one principal meridian of the cornea being considerably steeper or flatter than the other principal meridian of the cornea. Fitting a patient with a soft toric contact lens for astigmatism is routine for eye-care practitioners and many times practitioners can choose a soft toric contact lens straight from their diagnostic fitting set that will provide acceptable vision and comfort for many astigmatic patients. But what happens when the patient’s refractive cylinder exceeds -2.25 diopters, which is the usual limit for off-the-shelf soft toric contact lenses? Let’s consider another scenario. What is a practitioner to do when a patient presents with comfort, fit, or visual acuity issues with a standard commodity off-the-shelf soft toric contact lens caused by an odd sized or odd-shaped cornea? It is in these exact scenarios that a custom soft toric contact lens may prove to be a great alternative!
The base curve and diameter of off-the-shelf toric contact lenses are manufactured for the mass population, those patients who fall within the center portion of the bell curve in regards to the corneal anatomic features that assist in determining the fit of a contact lens. The limited base curve and diameter offerings of off-the-shelf toric contact lenses can at times restrict practitioners when fitting patients who reside on the ends of the bell curve. This restriction in base curve and diameter can lead to comfort and/or visual acuity compromise. It is these patients who could potentially benefit the most from a custom soft toric contact lens such as SpecialEyes.
As we all know, off-the-shelf toric contact lenses are also limited in power offerings. Patients that have high refractive errors that fall outside of the off-the-shelf range in regard to sphere and cylinder power are often given an alternative choice to wear ophthalmic glasses. With large refractive errors, patients wearing ophthalmic glasses may find the glasses heavy, uncomfortable, or unattractive. These patients may also benefit from a custom soft toric contact lens.
The beauty of a custom soft toric contact lens, such as SpecialEyes, is the ability to design the toric contact lens to the patient’s exact refractive error. This includes precise sphere power and cylinder power in 0.10 diopter steps, as well as the exact axis in 1 degree increments, which is beneficial for the higher astigmatic patient. The broad range of customization of SpecialEyes custom soft toric contact lenses can aid in decreasing the chance of visual compromise when compared to fitting an off-the-shelf toric contact lens. This vast parameter range allows practitioners the opportunity to provide his or her patients with optimal vision correction, not compromised vision correction, which can often be found when fitting a patient in an off-the-shelf toric contact lens.
Right now you may be thinking “Well, I would fit my high astigmatic patient in a GP contact lens”. Yes, that is a viable option in many situations. However, patients that have had comfort issues or have a known intolerance to GP lenses may find more success in a custom soft toric contact lens. A prior GP intolerant patient will find that a custom soft toric contact lens provides optimal comfort due to the pliable nature of the material, coupled with precise visual acuity made possible by the vast parameter availability.
Currently, in my opinion, technology in the optometric industry seems to be advancing and prescribing custom soft toric contact lenses is following that technology curve. Consider the technology used in manufacturing ophthalmic lenses, the talk of “freeform” and “digital” lenses and the new tools and computerized equipment to manufacture lenses in power increments of 0.01 diopters. Thanks to the advancement in technology, digital lenses are completely custom and made-to-order for our patients. Custom soft toric contact lenses are just the same — you specify exactly the needs of your specific patient and the custom soft toric contact lenses are made-to-order. This ensures that the patient receives not only a unique individualized contact lens made especially for his or her cornea, but also a fresh lens that has not been massed produced and placed on a shelf waiting for a home.
Joanna Chmiel, ABOC, NCLEC
Joanna Chmiel is an ABO and NCLE certified consultant at SpecialEyes. She brings with her 8 years of experience in the optical and contact lens industry.