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My colleagues and I watched our patient HT grow up, and become a star athlete, a registered nurse, a wife, and a mother. Along the way, she developed keratoconus, which negatively affected her vision and quality of life; over time, it worsened. She tried multiple contact lens designs and materials with limited success. As she inserted a pair of soft keratoconic lenses, I anxiously waited to see how well she could see—and tolerate—lenses created from a totally new concept in lens design. She turned to me and said, “I have not seen this well since I was in high school.”
Specialty contact lenses offer eye care providers a unique opportunity to use knowledge, skills, and technology to enhance patients’ vision and quality of life. These lenses also offer patients a chance to see more clearly and comfortably.
Keratoconus is a progressive, noninflammatory corneal disorder characterized by stromal thinning and corneal steepening. The process leads to irregular astigmatism, scarring, and often causes marked dis- torted vision.1,2 Histological and confocal microscopic examinations of keratoconic corneas reveal progressive thinning of the central and midperipheral cornea with degenerative alterations in the anterior limiting lamina (Bowman layer).2 Progressive corneal ectasia typically occurs inferior to the visual axis, and while apex location varies from patient to patient, it may not have an impact on the success of contact lens correction. Nejbat et al3 fitted 156 keratoconic eyes with rigid gas-permeable (RGP) lenses and found that the location of the cone did not affect patients’ ultimate RGP- corrected visual acuities.
“The revival of large-diameter RGP lenses and the introduction of new contact lens designs and materials afford practitioners a range of treatment options.”
For many years, rigid corneal contact lenses (with a diameter less than that of the cornea) were the primary tool for treating keratoconus. The revival of large-diameter RGP lenses and the introduction of new contact lens designs and materials afford practitioners a range of treatment options. Large-diameter lenses fall into three categories: corneal (8-12.5 mm), corneoscleral (12.5-15 mm), and scleral (15-25 mm).4 As a group, these are often referred to as “scleral lenses”, and because large-diameter lenses rest primarily on the sclera, they produce less lens sensation and awareness than those that rest on the highly sensitive cornea.4
Increasing interest in scleral lenses has fostered a number of websites to educate practitioners about how to fit these lenses. The Scleral Lens Society and the Contact Lens Manufacturers Association are useful resources for learning about this mode of vision correction. In 2010, Eef van der Worp published, “A Guide to Scleral Lens Fitting,” an excellent reference for establishing a scleral lens practice.5
BEYOND RIGID DESIGNS
Not withstanding the advances in rigid keratoconus designs, some patients cannot tolerate them. Fortunately, other options have emerged. The SynergEyes lens is a hybrid design composed of a gas- permeable center and a soft-skirt surround. In 2010, the manufacturer introduced ClearKone, a hybrid design specifically formulated to facilitate keratoconic lens fitting. The design offers multiple combinations of soft-skirt curves and central base curves. By enabling customization of these variables, the ClearKone concept reduces the risk for “tight lens” syndrome, a common problem associated with early designs of hybrid lenses. Although these lenses can theoretically be fitted empirically, the use of a fitting set is highly recommended.6
Customizable soft lenses are a relatively new option for keratoconus; examples include the NovaKone and the KeraSoft IC (Bausch + Lomb). The NovaKone (Figure) was introduced in 2011 and is made from hioxifilcon D, a 54% hydrogel material. Although the standard diameter is 15.0 mm, NovaKone lenses may be prescribed in other diameters. The fitting system is configured around three variables. The base curve (ie, the central curve) is adjusted to optimize the relationship between the corneal apex and the lens. The fitting curve surrounds the base curve and is altered to optimize the relationship between the peripheral cornea and the peripheral curve. These base and fitting curves can be independently adjusted to enhance overall fit. The other variable is the IT factor, which determines center thickness; corneas with higher degrees of irregu- larity typically require higher IT values. These lenses may be ordered in spherical or toric powers.7
The Kerasoft IC, a new soft lens design configured for keratoconic corneas, is composed of a lathable silicone-hydrogel material (Definitive), which contains 74% water. The base and peripheral curves can be independently manipulated to enhance fitting.8
POSTREFRACTIVE SURGERY LENSES
Some individuals who undergo refractive surgery have less-than-optimal results.9 Potential post-LASIK complications include decreased night vision, glare, halos, monocular diplopia, and distorted vision.10 These may occur despite an otherwise good surgical outcome as the result of an increase in higher-order aberrations due to the corneal surface irregularities produced or to postsurgical wound healing.10 Because these procedures typically create central corneal flattening, rigid lenses with conventional geometry (ie, the steepest curves are in the center of the lens with gradual flattening toward the periphery) do not work well. In reverse-geometry or plateau lenses, the secondary and midperipheral curves are steeper than the base curve.11
Tan et al fit 28 post-LASIK patients who complained of reduced night vision, glare, halos and/or monocular diplopia. They reported that reverse-geometry RGPs reduced higher-order aberrations by approximately 65%.10 Steele and Davidson reported good results in fitting post-LASIK patients with moderate amounts of correction in soft spherical and toric lenses.12 Soft reverse-geometry lenses are also available. The Harrison postrefractive surgery soft lens was introduced by Paragon in 1997,13 and it is now available from X-Cel Contacts (hefilconA, FlexLens Post Surgical) in a broad range of powers, diameters, and configurations.
As mentioned previously, the advent of the lathable silicone-hydrogel material known as Definitive, produced by Contamac and composed of efrofilcon A, allows manufacturers to produce custom designs from a material with a Dk of 60.8.14 The material can be used to fabricate reverse-geometry lenses, and because of the significant increase in its oxygen permeability, the risk for corneal edema and neovascularization is reduced.15
A rock propelled by a Weed Eater struck the right eye of RB, a 34-year-old ranch worker. He immediately developed hyphema and was successfully treated by a local ophthalmologist. After the hyphema cleared, the patient was found to have several broken zonules with 2-mm lateral displacement of the lens and a fixed 8-mm pupil. His work requires him to be outside most of the time in a windy, dry climate with sunny, clear skies more than 300 days each year. The enlarged pupil produced severe photophobia, even when he wore dark sunglasses. He was referred to our clinic for a prosthetic contact lens.
We found minimal refractive error, but glare testing revealed a substantial reduction in his visual acuity. We obtained multiple photographs of his unaffected eye and ordered a custom prosthetic lens from Orion Vision Group. The lens had a black underprint with a 4-mm pupil to reduce glare and a color overlay to match the color of the patient’s other iris. He successfully wears this lens every day and is able to work outside in the sunny environment without discomfort or reduced vision.
Individuals who have suffered ocular trauma with or without residual vision often have disfigurement of the cornea or iris. Complications from surgery related to glaucoma, retinal disease, corneal disease, or infec- tious diseases such as trachoma and herpes keratitis may cause disfigurement of the cornea. These patients often benefit psychologically and/or functionally from prosthetic lenses. In the case of a blind or disfigured eye, the benefits are primarily cosmetic, but very important to the patient.16
COUNTING THE COST
Specialty lenses are, by their very nature, often significantly more expensive than conventional lenses. They often require substantially more chair time to ultimately achieve success. It is important that patients understand that these are not “trial lenses,” and that when the initial lenses are not successful, they must be returned to the manufacturer for credit. In some cases, health or vision insurance may pay for part or all of the material and professional fees, but the patient often has to pay for the entire cost of the therapy. When establishing a specialty lens practice, it is vital to set appropriate professional and material fees and explain them to the patient at the outset of his or her treatment. In-depth discussions of the financial aspects of specialty lens care are beyond the scope of this article, but I would strongly recommend Dr. Clarke Newman as a true authority in this area.17
Fitting patients with specialty contact lenses can be challenging, frustrating, and time consuming, but offering this service can also be tremendously rewarding. There are many online resources available as well as meetings like the Global Specialty Lens Symposium held in Las Vegas and the San Diego Specialty Contact Lens Symposium. Specialty lenses give us the opportunity to improve—and in some cases change—some one’s life. Consider adding them to your practice.
William Townsend, OD, practices at Advanced Eye Care in Canyon, Texas, is an adjunct professor at the University of Houston College of Optometry, and is president of the Ocular Surface Society of Optometry. He indicated no financial interest in the products or companies mentioned herein. Dr.Townsend may be reached at firstname.lastname@example.org.
- Hollingsworth JG, Efron N. Observations of banding patterns (Vogt striae) in keratoconus: a confocal microscopy study. Cornea. 2005;24(2):162-166.
- Mathew JH, Goosey JD, Bergmanson JP. Quantified histopathology of the keratoconic cornea. Optom Vis Sci. 2011;88(8):988-997.
- Nejabat M, Khalili MR, Dehghani C. Cone location and correction of keratoconus with rigid gas-permeable contact lenses. Cont Lens Anterior Eye. 2012;35(1):17-21.
- Efron N, Morgan PB, Helland M, et al. International rigid contact lens prescribing. Cont Lens Anterior Eye. 2010 Jun;33(3):141-143.
- van der Worp E. A Guide to Scleral Lens Fitting. College of Optometry, Pacific University. http://commons.pacificu.edu/mono/4/. Accessed January 14, 2012.
- Davis R. Recent Hybrid Lens Technology. http://treatkeratoconus.com/blog/evolution-of-a-hybrid-lens-part-2
- Alden Optical. Soft contact lenses for keratoconus. http://www.aldenoptical.com/docs/novakone/AldenOptical_No- vaKone_FittingGuide.pdf. Accessed January 14, 2012.
- Bausch + Lomb KeraSoft IC Training Website. http://www.kerasofttraining.com/. Accessed January 14, 2012.
- Melki SA, Azar DT. LASIK complications: etiology, management, and prevention. Surv Ophthalmol. 2001 Sep-Oct;46(2):95-116.
- Tan G, Chen X, Xie RZ, et al. Reverse geometry rigid gas permeable contact lens wear reduces high-order aberrations and the associated symptoms in post-LASIK patients. Curr Eye Res. 2010;35(1):9-16.
- AOCLE. Association of Optometric Contact Lens Educators. http://www.aocle.org. Accessed January 14, 2012.
- Steele C, Davidson J. Contact lens fitting post-laser-in situ keratomileusis (LASIK). Cont Lens Anterior Eye. 2007;30(2):84-93.
- The Harrison postrefractive surgery soft lens was introduced by Paragon in 1997. Primary Care Optometry News. October 1997. http://tinyurl.com/bj2vwmm. Accessed January 22, 2010.
- Brujic M, Miller J. The comfortable side of keratoconus. January 25, 2012. Review of Cornea & Contact Lenses. http:// www.reviewofcontactlenses.com/content/d/rgp_lenses/c/32141/
- Kinoshita BT, Lampa M, Caroline P. Unique applications for silicone hydrogel lenses. September 1, 2008. Contact Lens Spectrum. http://www.clspectrum.com/articleviewer.aspx?articleid=102038. Accessed January 17, 2013.
- Cassell M. Changing lives with prosthetic soft lenses. April 1, 2010. Contact Lens Spectrum. http://www.clspectrum. com/articleviewer.aspx?articleid=104098. Accessed January 17, 2013.
- Newman Clarke. Coding Strategies. http://www.clspectrum.com/articleviewer. Accessed January 17, 2013.