Specialty Contact Lenses for Keratoconus and Irregular Corneal Conditions
Lead by Dr. John D. Gelles, the contact lens division of the CLEI Center for Keratoconus has unparalleled experience in specialty contact lens fitting for keratoconus and other corneal diseases. Specialty contact lenses are the mainstay of visual improvement for individuals suffering from vision loss associated with keratoconus and other irregular corneal conditions. Our center is exclusively devoted to addressing the needs of keratoconus patients.
Specialty contact lenses are only a part of the management for keratoconus and irregular corneal disease management. Keratoconus is progressive in nature and treatments such as corneal collagen crosslinking are vital to slowing progression. Additionally visual correction procedures for irregular corneas, such as topography guided PRK, may improve uncorrected vision and vision with glasses while improving the cornea symmetry. This shape improvement may make contact lenses simpler.
At the Cornea and Laser Eye Institute and the CLEI Center for Keratoconus. Dr. Peter S. Hersh, Dr. Steven A. Greenstein, and Dr. John D. Gelles are world renowned experts in keratoconus and irregular corneal disease management and research.
They have written many of the foundational manuscripts on keratoconus management. Dr. Hersh was also the principal investigator, medical monitor and primary author on the clinical trials and manuscripts related to corneal collagen crosslinking in the United States. Dr. Hersh, Dr. Greenstein and Dr. Gelles collaborate to provide the best care to manage your condition.
The Specialty Contact Lens Design Process at CLEI
The process of designing a customized lens to meet the needs of the keratoconus patient starts with an advanced and in depth evaluation. This evaluation guides the process to understand which type of specialty contact lens will meet your individual needs. A multitude of different scans, impressions and diagnostic lenses may be used in the design process. Once a lens type has been selected, Dr. Gelles begins the process of creating a custom contact lens for you. This process generally involves several revisions or modifications to ensure the lens is ideally fit, eye health is maintained and vision is the best possible.
Types of Specialty Contact Lenses for Keratoconus and Irregular Corneal Conditions
Standard Soft Lenses:
Most patients are familiar with standard soft lenses. These lenses are mass-manufactured in a process called cast molding. The lens parameters are generally limited to fit the average shape, size, and power needs of a normal eye. Though they are highly successful for most individuals with uncomplicated corneas and average refractive errors, those patients with moderate to advanced corneal irregularity commonly experience difficulty. However, individuals with mild corneal irregularity and refractive error within the normal parameters, a standard soft lens may achieve a satisfactory outcome.
Unlike their mass-produced counterparts, custom soft lenses are not limited to the typical parameter constraints of the normal corneal population. Custom soft lenses are lathe-cut and can be produced in an extensive range of base curve radii, diameters, materials, and nearly endless refractive powers. Some of these lenses can have a cosmetic or prosthetic option added, which can be useful to improve cosmesis and to reduce glare. Additionally, lens thickness can be significantly increased to create a pseudo-rigidity, which can mask corneal irregularity. Success of these lenses depends on the severity of the irregularity. For individuals who are unable to tolerate corneal GP lenses, custom soft lenses may provide adequate vision and improved levels of comfort.
Custom Corneal Gas Permeable (GP) Lenses:
Corneal GP lenses are the classic choice to mask corneal surface irregularities and to improve visual acuity. These lenses are also referred to a hard lenses, rigid lenses and RGP (rigid gas permeable) lenses. Using corneal GP lenses on a cornea that has very minor irregularity is similar to fitting them for refractive correction on a normal cornea. However, fitting corneal GPs becomes increasingly difficult as the corneal surface becomes more irregular. Success of these lenses depend greatly on the severity and location of the corneal irregularity. Many patient whom have had difficulty with GP lenses in the past generally have irregularity that is too severe to be successful with this type of lens. These lenses are lathe-cut and can be produced in an extensive range of base curve radii, diameters, materials, and nearly endless refractive powers. When fitting a corneal GP lens, precision of fit is of the utmost importance to maintain the corneal integrity and lens comfort. Additionally GP lenses have proven useful in deciding if surgical intervention may be beneficial.
Custom Piggyback (PB) Lens Systems:
For patients experiencing reduced comfort or minor epitheliopathy with a best-fit corneal GP, a PB lens system can be utilized. This approach uses a GP lens to improve visual acuity, while the underlying soft lens provides corneal protection, cushioning the cornea from the GP lens and improving comfort. The PB lens system may be best utilized when other options have failed and GP lens is the appropriate first lens option. Patients may be apprehensive to adopt this modality due to the perceived difficulty of wearing and caring for two lenses. Daily disposable standard soft lenses can be used to as the cushion to simplify care. On occasion a custom soft lens option, such as a cosmetic/prosthetic soft lens or a soft lens with a central excavation (allowing the GP lens to rest in a depression in the soft lens surface), can be used to improve cosmesis, reduce glare, or improve lens centration.
Custom Hybrid Lenses:
Hybrid lenses utilize a GP center with a soft lens edge, so they have characteristics of both GP and soft lenses. Various hybrid lens designs exist, with multiple geometries to accommodate a mild to moderate corneal irregularity. The GP portion of the lens can be modified to align with or vault over the corneal irregularity while the soft skirt an aids in adjusting lens movement, tear exchange, and lens centration and can also influence alignment of the GP portion of the lens. Hybrids can produce improved vision and comfort over corneal GPs in cases of lens decentration and lens intolerance. Of note, quality of life is similar with corneal GP, soft, and hybrid lenses. Hybrid lenses are filled with saline prior to lens application and because of the soft edge special attention to the force of lens application to avoid issues with lens wear.
When corneal irregularity is extreme, scleral lenses are preferred over other lens designs. These lenses vault over the cornea, aligning with the sclera and overlying conjunctiva (white of the eye). Scleral lenses can overcome nearly any corneal irregularity and should be considered as an option prior to referral for corneal transplantation. Individuals who have keratoconus and who otherwise would have undergone corneal transplantation secondary to contact lens failure can achieve success with these lenses. These lenses are can be designed with an abundance of unique modifications. Advanced fitting techniques can include impression based and scan based design. These lenses are lathe-cut and can be produced in an extensive range of shapes, diameters, materials, and nearly endless refractive powers. In addition, highly customizable optics such as wavefront guided, higher order aberration correcting optics can be added in some lenses.
Understanding Vision from Normal Corneas versus Keratoconus and Irregular Corneas
The eye is similar to a camera, a series of lenses (cornea and internal lens in the eye) are in place to help light focus on the film or camera sensor (retina in the eye). The cornea is analogous to the front lens on a camera. Normal corneas have a smooth dome shape, this allows light to focus to a single, sharp focal point. In a perfect eye this focal point lands on the retina. If the focal point is in front of or behind the retina the vision is blurry. This misalignment is called refractive error. Glasses, contact lenses, or vision correction surgery can aid in moving the focal point to the retina. This creates clear distortion free vision.
Keratoconus and Irregular Cornea
A irregular cornea is one that has lost its smooth dome shape. This can be caused by a variety of conditions such as keratoconus. This irregularity causes light to distort, resulting in multiple focal points. This creates a type of blurred vision that can be described as distorted, overlapping, or ghosted and is also responsible for glare, flare and halos. Glasses and standard soft contact may help in moving the multiple focal points back toward the retina but these focal points remain separate and the vision still distorted. This visual distortion is called an higher order aberration.
Vision Simulations with Glasses Correction
Keratoconus & Irregular Cornea
Understanding Vision with a Specialty Contact Lens for Irregular Cornea
A specialty contact lens masks the irregular cornea shape. The lens surface creates a smooth dome shape, and this allows the multiple focal points to come back into a single focal point, improving vision and reducing distortion.
When a specialty contact lens is worn, the vision is significantly improved. In some cases vision will need to be further refined with the use of highly customized optics, even further improving vision and reducing distortion.
Visual Simulation with a Specialty Contact Lens
Keratoconus and Irregular Corneas
Irregular corneas develop as a result of disease, dystrophy, trauma, or surgical complication. The resultant vision from the asymmetric corneal shape cannot be adequately corrected with spectacles or traditional soft contact lenses. The primary function of specialty contact lenses for this population is to mask the abnormal corneal surface, reducing the associated blur and improving visual acuity.
Irregular Corneal Conditions:
Corneal Ectasia: These are diseases characterized by weak and thin corneal tissue resulting in an irregular cornea shape. Examples include conditions such as keratoconus, keratoglobus, pellucid marginal degeneration, and corneal ectasia after surgery.
Post-Keratoplasty: A keratoplasty is also known as a corneal transplant. These surgeries are used when the cornea is severely scarred or have extremely advanced disease. They can involve the replacement of all or select layers and areas of the cornea. After transplantation the cornea is smoother and clearer but irregularities still exist. Examples include penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK), corneal tectonic grafts (patch grafts), and epikeratophakia.
Post-Corneal Surgery: In very rare cases, after a corneal procedure to reshape the cornea, the corneal surface may become irregular in shape. Examples include after laser assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), radial keratotomy (RK), or intracorneal ring segment (Intacs, Keraring, MyoRing, Ferrara Ring).
Corneal Opacity: A corneal opacity is a scar in the cornea. Scars may result in an irregular corneal surface and can occur after trauma, infection, or advanced ectasia.
Corneal Dystrophies: These are genetic, often progressive, conditions where abnormal tissue often accumulates in the cornea. Anterior and stromal dystrophies such as lattice, granular, Meesmann, Cogan, and Reis-Bucklers dystrophies may result in an irregular corneal shape.
Corneal Degenerations: These conditions cause deterioration and sometimes impair function of the peripheral cornea tissue. Examples include Salzmann’s nodular degeneration and Terrien’s marginal degeneration