The following article appears in Optometric Management's January 2018 special “Contact Lens” editorial section.
PROVIDING KERATOCONUS patients with contact lenses can be a remarkably rewarding part of your practice. The reason: You are providing a “yes” to patients who may have been interested in contact lens wear.
Here, I discuss how to identify keratoconic patients and the contact lens options available to provide them with successful wear.
IDENTIFYING KERATOCONUS PATIENTS
A patient who manifests against-the-rule or oblique astigmatism that is increasing in amount without clear BCVA endpoints is a red flag for the condition. For this patient, consider ordering a topography to help determine the appropriate diagnosis. Keratoconic corneal thinning may also be seen on OCT and pachymetry scans of the cornea.
In its more moderate to severe stages (corneal thickness between 400μm and 524μm), keratoconus will decrease a patient’s BCVA with traditional ophthalmic lenses. Specifically, these patients often experience a significant decline in visual quality in low light levels as the pupil dilates. In milder cases (corneal thickness above 525μm), the patient’s VA may be correctable to 20/20, but his or her visual quality may be negatively affected. Thus, when the condition is identified, it is important to appreciate the degradation in the quality of vision these patients will often experience, even if they have 20/20 VA.
Early identification of keratoconus is critical to help guard the patient from behaviors, such as mechanical stress from eye rubbing, that can exacerbate and accelerate the progression of the condition. Keratoconus is strongly associated with allergic and atopic conditions, both of which can prompt eye rubbing. Educate patients who have keratoconus and allergic and atopic conditions to avoid allergens and to use cool compresses and appropriate pharmacotherapy, including topical mast cell stabilizer/anti-histamine combinations, along with corticosteroids, as alternatives to eye rubbing.
In addition, educate these individuals about their contact lens options, as options will often mask many of the aberrations that keratoconus patients may experience with eyeglasses.
CONTACT LENS OPTIONS
The following can benefit keratoconus patients:
- Standard soft toric contact lenses. Early, or mild, keratoconic patients often benefit from these, as toric lenses usually have thicker profiles than spherical lenses and provide some level of improvement when placed on the eye. Don’t be surprised if the cylinder power and axis required in these contact lenses do not coincide with what you would expect based on the patient’s spectacle prescription. The presence of irregular astigmatism in the plane of spectacle lenses often produces unreliable powers for standard soft toric lenses. As such, it is critical to perform a careful over-refraction after the lenses have settled on the eyes to optimize the prescription in the lenses.
- Soft contact lenses. Additionally, a number of soft contact lens options specifically made for the keratoconic patient now exist. NovaKone (Alden Optical) is a specialty lens designed to provide a steep central base curve along with a flatter periphery that is meant to align with the contour of the sclera. KeraSoft IC (Ultravision) is a specialty lens made for keratoconus that leverages aspheric optics to optimize vision for these patients. Be sure to contact the manufacturers of these lenses for fitting guides.
- Small diameter GP lenses. These lens designs have traditionally been the primary choice for keratoconic patients because the lenses’ rigid surface provides correction of the higher-order aberrations and irregular astigmatism often associated with the irregular cornea. These lenses require initial lens adaptation because of the lens edge awareness that many first-time GP wearers will experience. When adapted to, these lenses can be worn successfully by many of these individuals. The ideal patient for this lens has central cones and currently wears GP lenses.
- Hybrid lenses. These lenses provide the benefits of GP optics in the center of the lens with the comfort of a soft skirt around the periphery of the lens. The lens feels more like a soft lens, but offers GP optics, so the patient achieves wearing comfort, along with good vision. The lenses are ideal for patients who experience insufficient vision, due to the patient’s unmet visual demands and the irregularity of the cornea, via soft lenses. The lenses also work well for patients whose visual quality improves with GP lenses, but have a difficult time wearing the lens because of poor comfort. Contact SynergEyes, the only company that makes hybrid lenses, regarding fitting questions.
- Scleral contact lenses. These large diameter GP lenses rest on the conjunctiva and underlying sclera, completely vaulting the cornea. They have the benefit of providing the optics of a GP lens with significantly less lens awareness. Additionally, the optical zones in scleral lenses are larger than in small diameter GP lenses; this can improve vision in some patients. There are three critical components to successfully fitting scleral lenses. The first is obtaining appropriate central corneal clearance between 100um to 300um at the center of the cornea. The second is obtaining appropriate limbal clearance. The third is the scleral landing zone, which should, ideally, mimic the sclera profile and not be steeper or flatter than the sclera. (For information on how to fit scleral lenses, see http://bit.ly/2iYeosN .)
Early identification of keratoconic patients, understanding the contact lens options available to provide them with successful wear and offering these lenses in your practice, can change these patients’ lives for the better, while creating patient loyalty and several referrals to your practice. OM