Corneal Desiccation in Today’s GP Lens Wearers: Results
BY JAVERIA AZHAR, OD; EDWARD S. BENNETT, OD, MSED, FAAO; & CARMEN F. CASTELLANO, OD, FAAO
Our July column stated that studies have reported as high as 40% to 90% incidence of corneal desiccation in GP lens wearers (Edrington et al, 2002; Henry et al, 1987; Fonn and Sorbara, 2005). However, there have been many improvements in lens design and materials that should result in reduced incidence.
Protocol and Methods We performed a study to evaluate the occurrence of corneal desiccation in today’s clinical setting in a controlled environment using a prospective model with the same observer and to determine the overall incidence, as well as the percentage, of clinically significant cases. A total of 100 consecutive eyes wearing spherical GP lenses were evaluated at Dr. Castellano’s practice. The study received approval from the University of Missouri-St. Louis Institutional Review Board. The grading scale used to assess corneal desiccation is from Schnider et al (1997). The grading scale defines 0 as an absence of staining; 1 as discrete countable punctate spots, superficial depth; 2 as mild confluence, superficial depth; 3 as marked confluence, deep staining; and 4 as epithelial loss.
In addition, the lens position was assessed similarly to a study by Henry et al (1987) and categorized as superior-central, central, and inferior. One hundred eyes from 52 subjects, all wearing spherical lenses (predominantly monovision), were evaluated. There were 33 females and 19 males with an age range of 40 to 83 years.
Results A total 30% of the eyes evaluated exhibited corneal desiccation staining, with 27 eyes exhibiting Grade 1 staining and three eyes with Grade 2. Essentially, only 10% of the eyes exhibited significant staining. There were 78 eyes in which the GP lens exhibited a superior-central position, 21 had a centered position, and only one lens decentered inferiorly. Of the superior-central lenses, 23 (29.5%) corneas exhibited desiccation staining, seven (33%) of the central-positioned lenses exhibited staining, and there was no staining in the inferior-positioned lens.
Discussion The 30% value is lower than that reported in previous studies and may reflect improvements in materials, designs, and manufacturing technology. The fact that the subject population was older than normal is important as tear volume decreases with age. In a study by Henry et al (1987), 34% of the lenses positioned superior-central with 37% manifesting desiccation staining, 53% positioned centrally with 57% exhibiting staining, and 13% positioned inferiorly with 73% exhibiting staining.
Although the incidence of corneal staining did not vary greatly between superior-central and central-positioning lenses, it is important to mention that only one lens was decentered inferiorly. This may reflect the thinner designs and more uniform edges in common use today. And, because an inferior-positioned lens typically results in greater superior edge clearance, more lid-lens interaction is possible, impacting the quality of the blink and causing corneal desiccation. Certainly, a lid-attachment fitting relationship with a superiorly positioned lens design is desired to minimize interference with the normal blink process.
The fact that only 10% of the staining was clinically significant supports the quality of today’s lenses and their resultant lens-to-cornea fitting relationships. CLS
For references, please visit www.clspectrum.com/references and click on document #240.
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 email@example.com. Dr. Castellano is owner of The Koetting Associates, an optometric group practice specializing in contact lenses.