Contact Lens, Surgical Options for Treating Keratoconus
BY WILLIAM L . MILLER, OD, PHD, FAAO
We often think of medical intervention when considering treatment for keratoconus; however, contact lenses can be and are the best treatment approach for 80 percent to 90 percent of such patients. Traditional therapy and management of keratoconus has focused mainly on GP lens use. Traditional GPs (8.0mm to 10mm) were used and are more likely to be used today in patients who have mild keratoconus in which the corneal ectasia is nearly central and small. Specialized designs exist that satisfy patients’ vision and comfort needs including Rose K, Rose K2 (both Blanchard), ComfortKone (Metro Optics) and TruKone (TruForm Optics), among others.
More advanced keratoconus or decentered, oval, or nipple cases may require larger lenses, typically intralimbal (10mm to 12mm) or scleral lenses. More recently, an increase in scleral GP lens application for postsurgical corneas has been instituted, along with their use in keratoconus. The ability to bridge the diseased cornea and rest on more normal scleral tissue provides many benefits to patients experiencing discomfort from traditional GPs. The sagittal depth also provides a tear reservoir that aids in bathing the cornea and creates a tear lens that negates the ectatic cornea’s irregular astigmatism. Some scleral GPs include Jupiter (Visionary Optics), MSD (Blanchard), So2Clear (Art Optical/Dakota Sciences/Metro Optics), Tru-Scleral (TruForm Optics) and PROSE (Boston Foundation for Sight).
Custom soft lenses can also be used for managing keratoconus. Some options include Kerasoft, KeraSoft IC (both Bausch + Lomb), and Intelliwave (Art Optical), which are available as either spheres or astigmatic corrections in the Definitive (efrofilcon A, Contamac) silicone hydrogel material.
Although not meant to be an exhaustive survey of surgical approaches, the following represent current modes of surgical intervention in cases of contact lens intolerance or reduced best-corrected visual acuity due to scarring and hydrops.
The most commonly performed procedure remains the penetrating keratoplasty (PK). Success rates are reported to be nearly 95 percent (Thompson et al, 2003; Tan et al, 2009), but graft rejections, although improved over the years, still remain a significant disadvantage to the procedure. To reduce graft rejection and to preserve the more normal posterior corneal stroma and endothelium, a deep anterior lamellar keratoplasty (DALK) may be performed. DALK is a lengthier procedure, and the patient may develop interface opacities (Anwar and Teichmann, 2002).
The particular surgery will depend on each patient’s history and presenting signs and symptoms. Both PK and DALK have also been performed using femtosecond laser technology (Kumar and Rootman, 2010). Implantation of intrastromal ring segments is an option that may help normalize the corneal surface and reduce aberrations.
In many of the surgical options listed here, your patient will still need to wear contact lens correction. These choices can include any of the previously mentioned lenses as well as RevitalEyes (Metro Optics), which is specifically designed for postsurgical eyes and is made in the Definitive silicone hydrogel material. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #204.
|Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a member of the American Academy of Optometry and the AOA where he serves on its Journal Review Board. He is a consultant or advisor to Alcon and Vistakon and has received research funding from Alcon and CooperVision and lecture or authorship honoraria from Alcon and B+L. You can reach him at firstname.lastname@example.org.|