KERATOCONUS UPDATE Prof M. R. Jain M. S, FICS, FAMS Medical Director MRJ Institute & Jain Eye Hospital, Jaipur Keratoconus cases are young with & their management requires empathy, skill and great understanding the psychology & the visual needs of the patient. Keratoconus (from Greek: kerato- horn, cornea; and konos cone), is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual spherical curve. In Keratoconus can be substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the patient. It is typically diagnosed in the patient's adolescent years and attains its most severe state in the twenties and thirties. If afflicting both eyes, the deterioration in vision can affect the patient's ability to drive a car or read normal print. In most cases, corrective spectacle lenses are effective enough to allow the patient to continue to drive legally and likewise function normally. But with the progress of the disease, the vision gets further deteriorated and the spectacle lenses are of not great help. Symptoms and Signs Keratoconus can be difficult to detect, because it usually develops slowly. However, in some cases, it may progress rapidly. As the cornea becomes more irregular in shape, it causes progressive nearsightedness and irregular astigmatism develops, creating additional problems with distorted and blurred vision. Glare and light sensitivity also may occur. Often, keratoconic patients experience changes in their eyeglass prescription every time they visit their eye care practitioner. It's not unusual to have a delayed diagnosis of keratoconus, if the practitioner is unfamiliar with the early-stage What Causes Keratoconus? New research suggests the weakening of the corneal tissue that leads to keratoconus may be due to an imbalance of enzymes within the cornea. This imbalance makes the cornea more susceptible to oxidative damage from compounds called free radicals, causing it to weaken and bulge forward. Risk factors for oxidative damage and weakening of the cornea include a genetic predisposition, explaining why keratoconus often affects more than one member of the same family. Keratoconus is also associated with overexposure to ultraviolet rays from the sun, excessive eye rubbing, a history of poorly fitted contact lenses and chronic eye irritation. Keratoconus Treatment In the mildest form of keratoconus, eyeglasses or soft contact lenses may help. But as the disease progresses and the cornea thins and becomes increasingly more irregular in shape, glasses and soft contacts no longer provide adequate vision correction. Treatments for moderate and advanced keratoconus include: Gas permeable contact lenses. If eyeglasses or soft contact lenses cannot control keratoconus, then rigid gas permeable (RGP or GP) contact lenses are usually the preferred treatment. Their rigid lens material enables GP lenses to vault over the cornea, replacing its irregular shape w But RGP contact lenses can be less comfortable to wear than soft contacts. Also, fitting contact lenses on a keratoconic cornea is challenging and time-consuming. You can expect frequent return visits to fine-tune the fit and the prescription, especially if the keratoconus continues to progress. Piggybacking" contact lenses. Because fitting a gas permeable contact lens over a cone-shaped cornea can sometimes be uncomfortable for a person with keratoconus, some eye care practitioner’s advocate "piggybacking" two different types of contact lenses on the same eye. For keratoconus, this method involves placing a soft contact lens, such as one made of silicone, over the eye and then fitting a GP lens over the soft lens. This approach increases wearer comfort because the soft lens acts like a cushioning pad under the rigid GP lens. "Piggybacking" contact lenses. Because fitting a gas permeable contact lens over a cone-shaped cornea can sometimes be uncomfortable for a person with keratoconus, some eye care practitioner’s advocate "piggybacking" two different types of contact lenses on the same eye. For keratoconus, this method involves placing a soft contact lens, such as one made of silicone hydrogel, over the eye and then fitting a GP lens over the soft lens. This approach increases wearer comfort because the soft lens acts like a cushioning pad under the rigid GP lens. Your eye care practitioner will monitor closely the fitting of "piggyback" contact lenses to make sure enough oxygen reaches the surface of your eye, which can be a problem when two lenses are worn on the same eye. However, most modern contacts — both GP and soft — typically have adequate oxygen permeability for a safe "piggyback" fit. ClearKone hybrid contact lenses. (SynergEyes Inc., Carlsbad, Calif.) These hybrid contact lenses combine a highly oxygen-permeable rigid center with a soft peripheral "skirt." The ClearKone version was designed specifically for keratoconus and vaults above the eye's cone shape for increased comfort. The manufacturer says hybrid contacts provide the crisp optics of a GP lens and wearing comfort that rivals that of soft contact lenses. ClearKone hybrid lenses are available in a wide variety of parameters to provide a fit that conforms well to the irregular shape of a keratoconic eye. SYNERGEYES HYBRID CNTACT SynergEyes Lenses for Keratoconus Lenses for clear vision. tilizing revolutionary hybrid technology, SynergEyes® has developed a family of lenses that provide keratoconus patients with the all-day comfort of soft contact lenses and the excellent visual clarity of rigid gas permeable lenses. SynergEyes contact lenses for keratoconus are custom designed to meet your vision correction needs. There are two different lens designs, SynergEyes® KC, and ClearKone™, to address all stages of keratoconus. Whether you have an early, moderate, or advanced stage of keratoconus, SynergEyes has a lens that will deliver clear vision and comfort. he Rose-K is an example of an exceptional and flexible lens design originally introduced by New Zealand Optometrist, Dr. Paul Rose. However, the key to a successful contact lens fitting isn't as much the lens as it is the skill and experience of the contact lens fitter. Fitting contact lenses on a keratoconic cornea is delicate and time-consuming. You can expect frequent return visits to fine-tune the fit and prescription. In some cases the process can take many months. For many patients it is also a continuing process which begins all over again as the condition progresses. Rose K Lens Heralded as "a quantum leap forward in the evolution of lens design for the condition" of keratoconus the Rose K lens has become the world's most frequently prescribed gas permeable contact lens for keratoconus. Unlike traditional contact lenses, the complex geometry built into every Rose K contact lens closely mimics the cone like shape of the cornea, for every stage of the condition. The result, a more comfortable fitting lens for patients and better sight (visual acuity). The Rose K lenses complex geometry has only become possible since computer controlled contact lens lathes were developed to cut sophisticated oxygen permeable polymers to the right shape. The Rose K lens has a number of features that make it ideal for keratoconus: 1. It's complex geometry can be customized to suit each eye and can correct all of the myopia and astigmatism associated with Keratoconus 2. They are easy to insert, remove and clean 3. They provide excellent health to the eye, because they allow the cornea to "breathe" oxygen directly through the lens 4. Practitioners have the Rose K trial set fitting system which achieves a first fit success in over 80% of patients internationally. Fig 1 Standard G P Contact Lens Fig 2 Rose K Contact Lens Rose K2 Lens Mr Paul Rose further refined the Rose K lens to take into account the unusual corneal shape of keratoconus patient's, which require abnormal curves on the back of the lens to fit the cornea optimally. This new lens is known as the Rose K2 lens. The Rose K2 lens minimizes these aberrations by applying very small changes to the curves on both the front and back of the lens in an attempt to bring the light passing through the lens within the pupil zone to a single point. ACT (Asymmetric Corneal Technology) By nature, the keratoconic cornea is asymmetric, where the inferior quandrant is frequently significantly steeper than the superior portion, causing the GP lens to lift off at 6 o'clock (see illustration E). Rose K lenses incorporating ACT are designed to accomodate this asymmetry (good edgel lift at 3,9 and 12 o'clock but lift at 6 o'clock). The inferior quandrant of the lens is steeper than the superior quadrants, providing a more accurate fit at 6 o'clock making the lens more comfortable and stable (see illustration F) and often provising superior vision. ACT is independant of the primary base curve and edge lift value and is available for Rose K2, Rose K, Rose K2 IC and Rose K2 Post Graft lens designs. Our fitting strategy for the Rose K lens doesn't follow the fitting guide precisely. We fit the Rose K lens flatter than the fitting guide suggests, and we do not necessary select a lens of the same diameter as the diagnostic set. In fact, a number of parameters on the lens are easy to customize, and we take advantage of that flexibility. Fitting lenses too tight is the single most common error in keratoconus. LENSES Scleral and semi-scleral lenses. Larger diameters found in these gas permeable (GP) lenses enable edges to rest on the eye's white sclera. Scleral lenses cover a larger portion of the sclera, whereas semi-scleral lenses cover a smaller area. Because the center vaults over the irregularly shaped cornea, this lens doesn't apply pressure to the eye's cone-shaped surface and feels more comfortable. These types of lenses also are more stable than conventional contact lenses, which move with each blink because they cover the c One example of a scleral lens is the Boston Scleral Lens Prosthetic Device (BSLPD). This cone-shaped device resembles a large contact lens and works partly by maintaining a "pool" of fluid on the eye's surface through which light rays pass and are bent to achieve proper focus. ornea only partially. Intacs. (Addition Technology, Des Plaines, Ill.) Intacs, or corneal inserts, received FDAapproval for treating keratoconus in August 2004. These tiny plastic inserts are placed just under the eye's surface in the periphery of the cornea and help re-shape the cornea for clearer vision. Intacs may be needed when keratoconus patients no longer can obtain functional vision with contact lenses or eyeglasses. Several studies show that Intacs can improve the best spectacle-corrected visual acuity (BSCVA) of a keratoconic eye by an average of two lines on a standard eye chart. The implants also have the advantage of being removable and exchangeable. The surgical procedure takes only about 10 minutes. Intacs might delay but can't prevent a corneal transplant if keratoconus continues to progress. A recent surgical alternative to corneal transplant is the insertion of intrastromal corneal ring segments. A small incision is made in the periphery of the cornea and two thin arcs ofpolymethyl methacrylate are slid between the layers of the stroma on either side of the pupil before the incision is closed.[40] The segments push out against the curvature of the cornea, flattening the peak of the cone and returning it to a more natural shape. The procedure, carried out on an outpatient basis under local anaesthesia, offers the benefit of being reversible and even potentially exchangeable as it involves no removal of eye tissue.[40] The principal intrastromal ring available is known by the trade name of Intacs. Internationally, Ferrara Rings are also available. Intacs are a patented technology and are placed outside the optical zone versus the smaller prismatic Ferrara rings that are placed just inside the 5 mm optical zone. Intacs are the only corneal implants that have gone through the FDA Phase I, II and III clinical trials and were first approved by the Food and Drug Administration (FDA) in the United States in 1999 for myopia; this was extended to the treatment of keratoconus in July 2004.[41]. Corneal cross linking. This non-invasive procedure strengthens corneal tissue to halt bulging of the eye's surface in keratoconus. While various methods are under investigation, one brand name associated with the procedure is corneal cross linking with riboflavin or C3-R (Boxer Wachler Vision, Los Angeles). In the C3-R procedure, eye drops containing riboflavin (vitamin B2) are placed on the cornea and are then activated by ultraviolet light to strengthen links between the connective tissue (collagen) fibers within the cornea. In the United States, FDA clinical trials for corneal collagen cross linking began in early 2008. Early results showing benefits of this method have been promising. In 2008, University of Siena researchers in Italy reported positive outcomes in all 44 eyes that were followed for three years after treatment with corneal collagen cross linking.* Other researchers have concluded that this simple treatment might reduce significantly the need for corneal transplants among keratoconus patients. Corneal cross linking also is being investigated as a way to treat or prevent keratoconus-like complications followingLASIK or other vision correction surgery. KERATOPLASTY Between 10% and 25% of cases of keratoconus[15][35][36] will progress to a point where vision correction is no longer possible, thinning of the cornea becomes excessive, or scarring as a result of contact lens wear causes problems of its own, and a corneal transplantation or penetrating keratoplasty becomes essential.. Keratoconus is the most common grounds for conducting a penetrating keratoplasty, generally accounting for around a quarter of such procedures.[37] The corneal transplant surgeon trephines a lenticule of corneal tissue and then grafts the donor cornea to the existing eye tissue, usually using a combination of running and individual sutures. The cornea does not have a direct blood supply, and so donor tissue is not required to be blood type matched. Eye banks check the donor corneas for any disease or cellular irregularities.