Corneal Desiccation in Today’s GP Lens Wearers
BY JAVERIA, AZHAR OD; EDWARD S. BENNETT, OD, MSED, FAAO; & CARMEN F. CASTELLANO, OD, FAAO
Corneal desiccation (CD; a.k.a. 3- and 9-o’clock staining, peripheral corneal staining, or peripheral corneal desiccation) is drying of the peripheral cornea adjacent to the lens edge. CD is the most frequent complication associated with GP wear. More severe cases of CD can lead to dellen formation or vascularized limbal keratitis. Studies have reported incidences of CD in GP lens wearers as high as 40% to 90% (Bennett, 1986a; Edrington and Barr, Jan. 2002; Henry et al, 1987); only 10% to 15% of the cases are clinically significant (Fonn and Sorbara, 2005; Ghormley et al, 1990; Bennett et al, 2014; Bennett, 2005; and others. Full list available at www.clspectrum.com/references.).
Lens-related factors historically associated with CD include materials that do not wet optimally, resulting in the tear film breaking up quickly on the lens surface (Bennett, 2014); inferior decentration (Henry et al, 1987); and high edge clearance (Edrington and Barr, Oct. 2002; Musset and Stone, 1981; Bennett, 1986b).
However, advancements in lens materials and manufacturing technology should result in reduced CD. The fluorosilicone/acrylate materials in common use today have less of the hydrophobic silicone. In addition, an increasing percentage of GP lenses are plasma-treated, which increases the surface wettability.
Inferiorly decentered lenses can impact the quality of the normal blink process because the lid/lens edge interaction increases. In fact, the incidence of CD is twice as high in inferior lens-to-cornea fitting relationships when compared to superiorly positioned lenses (Henry et al, 1987). Achieving a lid-attachment fit can minimize incidences of moderate-to-severe CD by reducing the interaction between the lid and the lens edge (Grohe and Caroline, 1989). Likewise, van der Worp et al (2008) found that an interpalpebral lens-to-cornea fitting relationship results in fewer complete blinks and more blink attempts when compared to a lid-attachment fit.
An increasing number of lenses are manufactured in an ultrathin design, which is recommended for all spherical GP patients who have ≤ 1.50D of corneal astigmatism. As this decreases lens mass by 30% to 40%, such lenses are less likely to decenter inferiorly, thus reducing the incidence of CD (Bennett et al, 2014).
In a retrospective chart review from Azhar et al (2015) presented at the Global Specialty Lens Symposium, the incidence of CD was less than 10%. However, this review was not performed in a well-controlled study environment; it included multiple observers and did not focus exclusively on CD.
Therefore, a more controlled follow-up study was performed at the same location. This study evaluated the occurrence of CD in a clinical setting using a prospective model with the same observer. The final results of 100 consecutive eyes wearing GP lenses will be presented in a future column.
Preliminary results show that although the incidence is higher than that demonstrated in the poster, it is also much lower than what previous studies found.
It is evident that CD is not as problematic today as it was in the past. Our next column will cover the final study results and a comprehensive management approach to minimize this GP-induced problem. CLS
For references, please visit www.clspectrum.com/references and click on document #236.
Dr. Azhar is the current Cornea and Contact Lens resident at the University of Missouri-St. Louis College of Optometry. Dr. Bennett is assistant dean for Student Services and Alumni Relations at the University of Missouri-St. Louis College of Optometry and is executive director of the GP Lens Institute. You can reach him at firstname.lastname@example.org. Dr. Castellano is owner of The Koetting Associates, an optometric group practice specializing in contact lenses.