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Keratoconus Treatment & Management

  • Author: Barry A Weissman, OD, PhD, FAAO; Chief Editor: Hampton Roy, Sr, MD  more...
 
Updated: Apr 21, 2016
 

Medical Care

The current paradigm of care for keratoconus is shifting from correcting the vision to slowing the disease process.

Rigid contact lenses and scleral lenses are the mainstay of vision treatment for keratoconus.

Patients with early keratoconus may successfully use spectacles or spherical/toric soft contact lenses. They may even rarely find that spectacle vision is superior to rigid contact lenses. More sophisticated soft contact lenses with aberration-controlled designs are now available and yield variable success.

Patients with modest-to-advanced keratoconus almost always require rigid contact lenses. When rigid contact lenses are no longer tolerated, some patients can maintain contact lens wear and usable visions with hydrogel contact lenses, piggyback contact lenses, or scleral contact lenses.

Scleral lenses are becoming more popular because of their excellent vision with improved comfort over cornea rigid gas-permeable contact lenses. Gas-permeable scleral lenses should be made of the highest oxygen-transmissible (Dk) material, and the tear layer should not be excessive to prevent hypoxia.[37]

Contact lens wear is often complicated by episodes of intolerance, allergic reactions (eg, giant papillary conjunctivitis), corneal abrasions,[38] neovascularization, and other problems, sometimes leading to total intolerance.

Ultraviolet corneal collagen cross-linking (UV-CXL) is the only procedure that is believed to slow the progression of keratoconus. It is used to increase the rigidity of the cornea by inducing additional cross-links within or between collagen fibers using UVA light and a photomediator, riboflavin, with the goal of slowing, possibly stabilizing, and even perhaps reversing, the progression of corneal ectasia in patients with keratoconus.[39, 40]

Riboflavin 5´-phosphate topical ophthalmic (Photrexa, Photrexa Viscous) was approved by the US Food and Drug Administration (FDA) in April 2016 for use in corneal collagen cross-linking (CXL) in combination with the KXL System for the treatment of progressive keratoconus. Both Photrexa and Photrexa Viscous (in 20% dextran) topical ophthalmic solutions are used during various stages of the procedure with the electronic device (KXL System), which irradiates the solutions with ultraviolet A light after they have been applied to the debrided cornea.

Approval of riboflavin 5´-phosphate topical ophthalmic was based on 3 prospective, randomized, parallel-group, open-label, placebo-controlled, 12-month trials conducted in the United States. Patients (n = 205) enrolled in the studies had 1 eye designated as the study eye and were randomized to receive CXL or sham in their study eye. From month 3 through month 12, the cross-linked eyes showed increasing improvement in Kmax (defined as the maximum corneal curvature and measured in diopters [D]).

An average Kmax reduction of 1.4-1.7 D at month 12 was observed in the cross-linked eyes, while the untreated eyes had an average increase of 0.5-0.6 D. The difference (95% CI) between the cross-linked and untreated groups in the mean change from baseline Kmax was -1.9 (-3.4, -0.3) D in Study 1 and -2.3 (-3.5, -1.0) D in Study 2.[41]

Variations of UV-CXL include including accelerated cross-linking[42] and UV-CXL corneal epithelium intact (epi-on) or removed (epi-off) techniques.[43, 44] UV-CXL has also been combined with same-day photorefractive keratectomy (PRK)[45] or ICRS[46] to improve the corneal integrity prior to surgery on keratoconic eyes. UV-CXL generally does not improve visual acuity (or at most improves 1-2 lines), although UV-CXL improves corneal clarity over untreated keratoconic corneas.[47]

Long-term studies are still needed to determine the success and adverse effects of UV-CXL, as well as the long-term biomechanical effect. UV-CXL is not recommended in thinner corneas because of the risk of endothelial damage. Currently, there is no effective way to measure collagen turnover, so the stability of the collagen cross-links remains a concern.[48] To date, endothelial damage has not been reported as a result of the standard procedure.[49] Complications of UV-CXL have included corneal haze, continual progression of keratoconus,[50] and, more rarely, diffuse lamellar keratitis, corneal melting, and persistent corneal edema.[51, 52, 53]

More studies are also needed to identify high-risk patients perhaps related to their age, diagnosis, corneal shape, and/or stages of ectasia.

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Surgical Care

Surgically removing central nodular scars by shaving the corneal surface (superficial keratectomy with a blade or excimer laser phototherapeutic keratectomy) may improve contact lens tolerance, decrease the rate of associated corneal abrasions, and preclude the need for corneal transplant.

Intrastromal corneal rings

Intrastromal corneal rings (ICRS) have been implanted in patients who have become intolerant to contact lenses, but these have been found to be more successful in mild than in advanced disease.[19, 20] ICRS does not halt the progression of keratoconus but may somewhat improve the unaided visual function of the patient after the disease is stable.

Bowman layer transplantation

Midstromal transplantation of Bowman layer (also known as anterior limiting lamina [ALL]) is a newer procedure used to flatten and strengthen advanced keratoconic corneas that may be too thin for UV-CXL. A midstromal pocket is created with air. The Bowman layer is removed and replaced by a donor Bowman layer graft. The overall flattening of the cornea could make contact lens wear more comfortable and hence postpone PKP or DALK indefinitely.[54] Bowman layer transplantation usually improves 1-2 lines of visual acuity.

Deep anterior lamellar keratoplasty

Deep anterior lamellar keratoplasty (DALK) is becoming the preferred surgical option for keratoconic eyes without hydrops because of the avoidance of endothelial rejection, quicker heal time, and increased wound strength.[55, 56] Improved graft survival compared to PKP is still controversial.[57] Currently, DALK represents 10%-20% of all keratoconic transplants and 30% when hydrops are excluded.[58] Visual acuity results of DALK are similar if not slightly inferior to those of PKP.

Penetrating keratoplasty

Penetrating keratoplasty (PKP) is still the more commonly performed surgery used to treat keratoconus in patients whose vision is not correctable to better than 20/40. PKP yields good success rates, especially in eyes with endothelial dysfunction and central opacities, resulting in clear visual axes in greater than 90% of all cases. PKP for keratoconus exhibits excellent visual and survival results, but young patients may require one or more grafts during their lifetime.[59]

The introduction of the femtosecond laser to trephine the recipient and donor tissues has improved tissue apposition and hastened healing. Best corrected visual acuities range from 20/50 to 20/100 after PKP, although visual acuities fall to less than 20/200 in 18.9% of advanced keratoconic eyes 15 years after surgery.[60] PKP requires continuing professional care to monitor for rejection, suture-related problems, wound dehiscence, and other difficulties. Although extremely rare, keratoconus can recur in a graft.

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Consultations

Consult with a cornea specialist (a graduate of a cornea fellowship program) and/or contact lens specialist who provides appropriate (primarily rigid gas-permeable) contact lens care.

An ophthalmologist who is a cornea specialist assists in identifying appropriate clinical conditions and timing for surgical intervention, such as superficial keratectomy, PKP, DALK, Bowman layer transplantation, ICRS, or UV-CXL. Alternatively, topography-guided conductive keratoplasty has been shown to be modestly effective in reshaping the cornea in keratoconic eyes, at least temporarily.[61]

A specialty contact lens practitioner (usually an optometrist but can be an optician or ophthalmologist) monitors contact lens care to optimize vision while minimizing complications of contact lens wear. This practitioner also helps to establish the appropriate clinical conditions and timing of surgical intervention, should this become necessary.

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Activity

Patients should avoid (vigorous) eye rubbing.

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Contributor Information and Disclosures
Author

Barry A Weissman, OD, PhD, FAAO Professor of Optometry, Southern California College of Optometry; Professor Emeritus of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Barry A Weissman, OD, PhD, FAAO is a member of the following medical societies: American Academy of Optometry, American Optometric Association, California Optometric Society, International Society for Contact Lens Research

Disclosure: Nothing to disclose.

Coauthor(s)

Karen K Yeung, OD, FAAO Senior Optometrist, Arthur Ashe Student Health and Wellness Center, University of California, Los Angeles

Karen K Yeung, OD, FAAO is a member of the following medical societies: American Academy of Optometry

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Christopher J Rapuano, MD Professor, Department of Ophthalmology, Jefferson Medical College of Thomas Jefferson University; Director of the Cornea Service, Co-Director of Refractive Surgery Department, Wills Eye Hospital

Christopher J Rapuano, MD is a member of the following medical societies: American Academy of Ophthalmology, American Ophthalmological Society, American Society of Cataract and Refractive Surgery, Contact Lens Association of Ophthalmologists, International Society of Refractive Surgery, Cornea Society, Eye Bank Association of America

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cornea Society, Allergan, Bausch & Lomb, Bio-Tissue, Shire, TearScience, TearLab<br/>Serve(d) as a speaker or a member of a speakers bureau for: Allergan, Bausch & Lomb, Bio-Tissue, TearScience.

Chief Editor

Hampton Roy, Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Hampton Roy, Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

Additional Contributors

Fernando H Murillo-Lopez, MD Senior Surgeon, Unidad Privada de Oftalmologia CEMES

Fernando H Murillo-Lopez, MD is a member of the following medical societies: American Academy of Ophthalmology

Disclosure: Nothing to disclose.

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An optic section of a keratoconic cornea shows corneal thinning. Vogt striae and some scarring can also be seen centrally; superiorly, a small (brown) section of the Fleischer ring is noted.
The fluorescein pattern of a rather flat-fitted rigid contact lens on an advanced keratoconic cornea.
 
 
 
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