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      Drugs & Diseases > Ophthalmology

      Keratoconus Treatment & Management

      Updated: Jan 04, 2023
      • Author: Karen K Yeung, OD, FAAO; Chief Editor: Hampton Roy, Sr, MD  more...
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      Treatment

      Medical Care

      The current paradigm of care for keratoconus has shifted from not only correcting the vision but also slowing the disease process.

      Scleral gas-permeable lenses and corneal rigid gas permeable lenses are the mainstay vision treatments 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 but are generally more comfortable than rigid gas permeable lenses.

      As the irregular astigmatism advances, corneal rigid gas contact lenses and scleral lenses provide better visual acuity for moderate to advanced keratoconus. Scleral lenses are 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 minimize hypoxia. [40]

      Contact lens wear is often complicated by episodes of intolerance, allergic reactions (eg, giant papillary conjunctivitis), corneal abrasions, neovascularization, and other problems, sometimes leading to total intolerance. Surgical care is recommended when the best corrected visual acuity achieved with contact lenses is worse than 20/40 vision or when contact lenses and scleral lenses are no longer tolerated.

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      Surgical Care

      Surgical care is differentiated among (1) treating the progression of keratoconus with ultraviolet corneal collagen cross-linking (UV-CXL), (2) removing corneal scars to improve contact lens tolerance, and (3) improving keratoconus-induced poor vision keratoconus with intrastromal corneal rings and corneal transplants. Surgery to improve visual acuity is elected when the best-corrected vision achieved with contact lenses or scleral lenses is worse than 20/40 or when contact lenses are no longer tolerated. Patients may still require contact lenses after surgical correction. [41]

      Ultraviolet corneal collagen cross-linking

      Whereas contact lenses improve the vision, UV-CXL is the only procedure that slows 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. When exposed to ultraviolet A radiation, riboflavin produces oxygen free radicals that initiate the creation of new covalent bonds. These bridge the amino groups of collagen fibrils, increasing the rigidity of corneal tissue. [42]

      Variations of UV-CXL include including accelerated cross-linking [43] and UV-CXL corneal epithelium intact (epi-on) or removed (epi-off) techniques. [44, 45] UV-CXL has also been combined with same-day photorefractive keratectomy (PRK), [46, 47] ICRS, [48] and phakic intraocular lens [49] 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. [50]

      UV-CXL is currently approved only for corneas with progressive keratoconus. It 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. Complications of UV-CXL have included corneal haze, [51] continual progression of keratoconus, [52] and, more rarely, corneal scarring, diffuse lamellar keratitis, [53] corneal melting, [54] persistent corneal edema, [55] endothelial cell density loss, [56] and herpetic keratitis. [57, 58, 59]

      Currently, CXL treatment is most effective in patients with progressive keratoconus who are aged 16-40 years and have a minimum corneal thickness of 400 microns, a maximum keratometry of < 60D, and no other known corneal diseases. [60]

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

      Surgical removal of nodular scars

      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) are polymethyl methacrylate segments implanted into the corneal stroma to reduce corneal distortion by flattening the steep areas of the keratoconic eye. Although not often fully successful, they are an option for patients who (1) are intolerant to contact lenses, (2) have clear central corneas, (3) have corneas with a thickness of at least 400 µm, and (4) retain penetrating keratoplasty as a remaining option. ICRS has been found to be more successful in mild than in advanced disease. ICRS does not halt the progression of keratoconus but may somewhat improve the unaided visual function of the patient after the disease is stable. Visual recovery may range from 3 months to a year after the procedure. ICRS is now being combined with CXL, although long-term results are still pending.

      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. [61] 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. [62, 63] Improved graft survival compared to PKP is still controversial. [64] Currently, DALK represents 10%-20% of all keratoconic transplants and 30% when hydrops are excluded. [65] Visual acuity results of DALK are similar if not slightly inferior to those of PKP in patients who do not have deep central corneal scarring.

      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. [66] Approximately 2.4%-20% of patients with keratoconus will require PKP, although this trend is decreasing owing to improved contact lenses and other surgical procedures. [31]

      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. [67] 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. Rejection rates range from 5.8%-41% during the first two years postsurgery. [68, 69, 70] Most patients will require spectacles and/or contact lenses following surgery.

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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 and scleral contact lens) 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.

      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.

      Psychiatric care may also be beneficial given that depressive disorders have been associated with the vision impairment caused by keratoconus. [71, 72, 73]

      Genetic counseling may also be beneficial to pregnant patients with keratoconus given the genetic nature of the condition. Although keratoconus is multifactorial, influenced by environmental and biochemical factors, multiple genes are known to be involved, and there is a high prevalence of family history.

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      Activity

      Patients should avoid (vigorous) eye rubbing.

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      Prevention

      Patients should avoid eye rubbing.

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      Long-Term Monitoring

      Frequently observe patients with keratoconus, especially because most wear contact lenses, which can produce complications including hypoxia and giant papillary conjunctivitis. Examine the upper eyelids via lid eversion in all contact lens wearers.

      Even in the absence of signs or symptoms of complications, contact lens care should be provided at 4-month to 6-month intervals to promptly address changes in fit or optics, as well as detecting asymptomatic complications and early intolerance.

      Patients with keratoconus who use contact lenses often have corneal abrasions, [74] particularly if corneal steepening has made the current rigid contact lens fit flat. Addressing such problems may preclude increased scarring, which could necessitate PKP.

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