Current GP Lens Research
BY S. BARRY EIDEN, OD, FAAO
While we are well aware of the advantages that GP lenses provide for our patients (including optimization of vision and physiological response), comfort adaptation and perceived complexity of fitting methods continue to limit their use. In the United States, based on 2014 data, only 6% of contact lenses were prescribed in GP materials (including corneal, scleral, and corneal reshaping designs) (Nichols, 2015). According to that report, this statistic is down from 8% in 2013 and 9% in 2012. International utilization of GPs in 2014 was reported to be 8%; however, the number varies greatly from country to country, ranging from a high of 44% to a low of 1% (Morgan et al, 2015).
Let’s take a look at some recent research outcomes in the field of GP contact lenses.
Fit Assessment To fit corneal GPs, practitioners must overcome the perceived complexity and challenges of fit assessment. A key element in the appropriate fitting evaluation of these lenses is the assessment of fluorescein patterns that indicate the lens-to-cornea fitting relationship.
Wolffsohn et al (2015) examined the optimum time at which GP fluorescein patterns should be evaluated. Aligned, 0.2mm steep, and 0.2mm flat GPs were fit to 17 patients. Fluorescein was applied to their upper temporal bulbar conjunctiva with a moistened fluorescein strip. Digital slit lamp images at 10x magnification of the fluorescein pattern viewed with blue light through a yellow filter were captured every 15 seconds. Fluorescein intensity in central, midperipheral, and edge regions of the superior, inferior, temporal, and nasal quadrants of the lens were graded subjectively using a +2 to –2 scale on the simultaneously captured images.
Subjectively graded and objectively image analyzed fluorescein intensity changed with time (p < 0.001). The expected aligned, flat, and steep fitting patterns could be seen in each meridian after approximately 30 to 180 seconds subjectively and 15 to 105 seconds in captured images.
The authors concluded that although the stability of fluorescein intensity can start to decline in as little as 45 seconds post-fluorescein instillation, the most appropriate time window to subjectively evaluate GP contact lenses in clinical practice is within 30 to 180 seconds of fluorescein instillation.
Lens Adaptation The greatest challenge to corneal GP lens fitting is the initial adaptation to lens wearing comfort experienced by our patients. Caracedo et al (2015) attempted to evaluate neophyte contact lens wearers’ adaptation to GP lenses in terms of wearing time, tear volume, stability, corneal staining, and subjective ratings over one month. Twenty-two subjects were enrolled to wear GPs on a daily wear basis. The study participants had never worn contact lenses previously. Contact Lens Dry Eye Questionnaire, Visual Analog Scales, Schirmer’s test, tear film breakup time (TBUT), and corneal staining grading were performed. Follow-up visits were scheduled at one, seven, 15, and 28 days following initial dispensing.
Results found that six subjects (27%) dropped out from the study before one month due to discomfort. Successful GP wearers (16 participants) achieved high levels of subjective vision and reported comfort scores of approximately nine of 10 between 10 and 15 days. They reported wearing their lenses for an average of 10.12 ± 2.43 hours after one month of wear. Conversely, unsuccessful wearers discontinued wearing the lenses after 10 to 15 days, showing significantly lower comfort scores and wearing time compared with the first day of wear. Schirmer’s test showed a significant increase at 10 days (p < 0.001), and the TBUT trends decreased after the first week of wear in the unsuccessful group.
The authors concluded that symptomatology related to dryness and discomfort, detected during the first 10 days of adaptation, may help clinicians predict participants who will potentially fail to adapt to GP lens wear.
Those with significant experience in fitting neophytes in corneal GP lenses realize that successful patients must get beyond the first approximately two weeks of adaptation before feeling that they will be successful. However, this study shows that those who failed to adapt had significantly lower comfort responses during that adaptation period when compared to successful wearers.
Visual Acuity Improvement One of the most appreciated advantages of GP contact lenses over other vision correction modalities is the optimization of vision outcomes. Opačić et al (2015) evaluated the performance of corneal GP lenses versus spectacles for patients who have high degrees of astigmatism (specifically corneal astigmatism). The investigation looked at auto-kerato-refractometry, manual keratometry, corneal topography, and Snellen visual acuity (VA). The best-corrected VA obtained with spectacles was compared with the best-corrected VA obtained with GPs in 72 patients (116 eyes).
All patients showed significant improvement in VA with GP lenses compared to spectacles (p = 0.0001). Level of improvement in VA represented as the number of lines obtained was as follows: 74% of patients gained two to four lines with GP lenses compared to spectacles, and almost 10% of patients gained five to seven lines.
The authors concluded that GP contact lenses provide a significant improvement in VA compared to that reached with spectacles in patients who have high corneal astigmatism. This study supports the clinical impressions held by experienced practitioners and should encourage us to suggest corneal GP lenses for our highly astigmatic patients who desire or require maximum visual performance and primarily have corneal astigmatism.
Quality of Life We often fail to realize the positive impact on quality of life that results from our efforts. Most dramatically, patients who suffer from vision-compromising diseases such as keratoconus, who can greatly benefit from contact lens therapy, will experience significant improvements in life quality. Wu et al (2015) compared the impact of GP contact lenses on vision-related quality of life (VR-QOL) in keratoconus patients of different grades of severity. Forty-six patients who had bilateral keratoconus were divided into three groups according to the average of the steep keratometry (K) readings in the two eyes of each patient. Main outcome measures included binocular VA, lens wearing time, the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25), foreign body (FB) sensation, comfort, and overall satisfaction.
Results found that patients who have severe keratoconus had significantly reduced wearing time compared with the other two groups (4.8 ± 2.5 hours per day). Regarding the subjective criteria, there was no significant difference on NEI-VFQ-25 scores, FB sensation, comfort, and overall satisfaction between mild and moderate keratoconus groups, but scores in the group who had severe keratoconus were significantly lower compared to the other two groups. Binocular VA strongly correlated with NEI-VFQ-25 scores; however, those scores had no significant correlations with different disease severities.
The researchers concluded that appropriate correction with GP lenses contributes to good VR-QOL for keratoconus patients; however, as the disease progresses to a steep keratometric value of greater than 52.00D (6.50mm), GPs did not guarantee a relatively good VR-QOL.
Newer lens designs might bring better life quality for these patients who have severe keratoconus. We should realize, however, that our main goal should always be to diagnose the disease as early as possible and apply methods to control, if not halt, disease progression to a level at which quality of life is not compromised regardless of contact lens performance.
Although GP corneal contact lenses are being fit at an ever decreasing rate, it is imperative for contact lens practitioners to realize the numerous advantages of this lens modality and to better understand how to present to our patients both these advantages and realistic expectations regarding initial adaptation to the wearing of these lenses. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #239.
Dr. Eiden is president and medical director of North Suburban Vision Consultants, president and founder of the International Keratoconus Academy of Eye Care Professionals, and co-founder of EyeVis Eye and Vision Research Institute. He is an adjunct faculty member at The University of Illinois Medical Center as well as at the Indiana and Illinois Colleges of Optometry and Pennsylvania College of Optometry at Salus University. He is also a consultant or advisor to CooperVision, Alcon, B+L, Visionary Optics, Alden Optical, Oculus, Oasis Medical, Paragon Vision Sciences, and SpecialEyes.