Research Study – A Comparison of SynergEyes KC Lens versus Traditional RGP Lens Designs for Patients with Irregular Cornea
Objectives. To compare whether patients with irregular corneas are more comfortable wearing SynergEyes®, a hybrid contact lens, compared with rigid gas permeable contact lenses.
Methods. A retrospective chart review of patients seen from the specialty contact lens practice at the University of Pittsburgh, who were refit with hybrid lenses from November 2005 to December 2006. Inclusion criteria included presence of irregular astigmatism in at least one eye from any cause, prior use of rigid gaspermeable lenses within the past year in at least one eye, lens tolerance issues, and all day use of contacts to attain functional vision. Best corrected spectacle and hybrid lens corrected Snellen acuities, the number of lenses needed to complete the fitting, lens related complications, and whether patients preferred the SynergEyes or rigid lens after at least 3 months of followup were used as the variables to compare the safety and efficacy between the two lens modalities.
Results. Seventy-nine eyes of 54 patients met criteria for inclusion. The average improvement over spectacle acuity was four Snellen lines with the SynergEyes lens. The average number of lenses required to successful fitting was 1.71. On review of patient opinions in followup, 79.5% of patients reported comfort was improved compared with rigid lenses, 13.5% said comfort was not better or the same, and 7% believed they were less comfortable.
Conclusions. In this population, the SynergEyes lens resulted in increased lens tolerability for many patients wearing therapeutic contacts. Patients who are otherwise unable to tolerate rigid gas permeable contacts should attempt use of a hybrid lens before resorting to penetrating keratoplasty.
Rigid gas permeable contact lenses are widely used for therapeutic applications in situations where irregular corneal topography causes high amounts of optical distortions and higher order aberrations (1-5). The inflexible structure of these lenses allows the tears to pool in the post lens space, effectively masking the irregular surface and imparting a spherical shape at the corneal plane. Together, these features improve the optical quality of the image produced at the fovea. Rigid lenses are highly effective at providing usable functional vision and can, in many instances, prevent corneal transplantation (1-5). While vision with theses lenses is usually significantly improved, ocular co-morbidities such as overwear syndrome, dry eye, blepharitis and tear film insufficiency, even when treated, can sometimes conspire to cause contact lens intolerance severe enough to result in reduced wearing times and/or discontinuation of lens wear. In these cases, patients must choose between nonfunctional vision and corneal transplantation (which may not eliminate the need for contact lenses).
The SynergEyes lens (Carlsbad, CA) aims to solve the problem of discomfort by surrounding a rigid gas permeable optic comprised of the highly oxygen permeable material Paragon HDS 100 (paraflufocon D) chemically bonded to a soft outer skirt comprised of PolyHEMA hem-iberfilcon A, which is nonionic and 27% water. The availability of different rigid optic designs, which includes the A series for more regular corneas, the KC series for steep and keratoconic topographical profiles, and the PS series for post-surgical corneas, allow for greater practitioner flexibility in fitting a wider variety of patients. In addition, the SynergEyes design offers a selection of soft skirt base curves that are useful to further optimize fitting.
A retrospective chart review was undertaken from the author’s contact lens practice at the UPMC Eye Center, University of Pittsburgh from December 2005 to December 2006. Cases were identified by obtaining billing records of patients who had been fit with SynergEyes lenses. The total number of patients fit with the lenses during the study period was 62. Inclusion criteria included the presence of corneal irregularity in one or both eyes necessitating the use of full time contact lens wear to attain functional acuity, prior use of traditional therapeutic rigid lens design within the past year, and refitting in at least one eye with a SynergEyes lens. Permission to conduct the review was obtained by the Institutional Review Board of the University of Pittsburgh.
Sixty of the 62 patients fit with SynergEyes lenses met the entry criteria during the period of the chart review. Six of these patients were not included in the review because of incomplete data sets, leaving a total of 54 eligible patients. There were 32 men and 21 women included in the review. The mean age was 36.17 years old (range, 23-90 years). The breakdown of conditions per eye for which lenses were prescribed is as follows: Keratoconus (57%), penetrating keratoplasty (15%), LASIK-induced keratoectasia (4%), Descemet’s stripping endothelial keratoplasty (1%), scarring (7%), Alpha Cor Prosthesis (1%), radial keratotomy induced keratoectasia (5%), globe rupture/trauma (6%), high astigmatism (2%), and pellucid marginal degeneration (2%).
Twenty-five patients were fit with the SynergEyes lens bilaterally and 29 were fit unilaterally, for a total of 79 eyes. The average amount of refractive cylinder for was 2.75 diopter (D) (range, 0-7D). The mean best corrected Snellen acuity with spectacles was 20/70, improving to a mean of 20/30 with the SynergEyes lens, yielding an average improvement of four lines of vision. The average number of lenses to successful fit was 1.71 (range, 1-4 lenses). Fitting problems that were encountered included: lens tightness 11%, removal problems 9%, dryness 6%, lens intolerance leading to eventual discontinuation 2%, subjective redness 1%, lens deposition 1%, corneal edema 1%, persistent bubble 1%. By the 3-month follow up visit, 52% of patients reported no problems, and no patients discontinued because of dissatisfaction with vision. About 79.5% of the patients reported that the comfort was improved compared with rigid lens designs, 13.5% said that the comfort was not better or the same and 7% believed that they were less comfortable.
The patients included in this review habitually relied on their contact lenses in order to function and this continued to be the case for our subjects after refitting. Twenty-five percent admitted to use of lenses for all waking hours, 7% wore them 10+ hours, 3% from 5 to 10 hours, 2% between 1 and 5 hours, and the remainder were too variable to quantify.
The use of a soft lens as a cushion to improve tolerability of rigid lenses has been widely employed both with the SoftPerm Lens (6-9) and use of piggyback systems (10-12). Concerns over the possibility for corneal hypoxia with the latter modality have been somewhat mitigated by the availability of silicone hydrogel lenses (13-15). However, a two lens system can be cumbersome and complex for the patients, and the risk of noncompliance with lens care regimens is likely to be greater. Although a review of the literature did not find articles that dealt with compliance in wearers of piggyback systems, per se, there is ample evidence that lens wearers tend not to clean lenses according to prescribed regimens and also tend not to discard disposable lenses in a manner consistent with doctor recommendations (16,17). It is therefore reasonable to conclude that taking care of both a rigid and soft lens would probably increase noncompliant behaviors.
The SoftPerm lens continues to be used as a viable alternative to use of piggyback systems and rigid lenses. However, the SynergEyes lens is an improvement on its predecessor in that the rigid optic allows more oxygen to reach the cornea (18) and has the availability of greater flexibility for lens design. The choice of different soft skirt base curves as well as different rigid optic designs with the SynergEyes lens provides the practitioner with a greater armamentarium to fit a wide variety of abnormal corneal pathologies.
The most common problem encountered was a tightening of the lens over the course of the day (11%), particularly in patients who had dry eye syndrome. Because many of these patients were fit just after release of the lenses, it is likely that practitioner learning curve played a role in this problem. We now understand that the key to increasing lens movement is actually steepening the lens, which at first seemed a paradoxical solution. Instead of the concept of first definite apical clearance lens that works well with many rigid gas permeable designs for irregular corneas, it is instead useful to prophylactically fit the steepest lens that will not produce an air bubble for both the rigid and soft base curves. This will increase lens movement, and in most instances, avoid lens adherence. As with all contacts, the SynergEyes lenses is not an option for all patients. In some cases, it is not possible to attain a satisfactory fit, but in the author’s experience this is usually with more pronounced corneal irregularities. However, for some patients, the increased diameter of the SynergEyes lens conferred a stability that would only have been achieved with miniscleral or scleral designs.
In this cohort, 35% of patients reported that they wore the lenses for more than 10 hours per day. However, in this study it is not possible to draw conclusions about whether wear time would be increased for patients who did not rely on their lenses to function. In addition, a criterion for inclusion in this review was the presence of limited lens tolerance. This factor may have skewed the results in favor of the hybrid lens. Future studies would benefit from a prospective design comparing the comfort and wearing time of SynergEyes to rigid lenses in a population that (1) do not have problems with rigid lens acceptance and (2) use lenses on a more voluntary basis for cosmetic purposes. Indeed, a recent article by Lipson suggests that the SynergEyes lenses are not more comfortable than soft toric lenses in normal patients (19). In addition, studies looking at quality of life, vision and comfort issues between hybrid and piggyback systems would be useful to guide the practitioner in tailoring lens modalities to optimize patient satisfaction. In our study, patients overwhelmingly preferred the SynergEyes lens for comfort compared with rigid gaspermeable lenses. Best corrected visual acuity improved four lines over Snellen vision and was comparable to that attained with published reports of traditional rigid lens designs. The use of a high dK hybrid lens for therapeutic indications can improve patient comfort in situations where all day wearing is required, and should be included as an option before penetrating keratoplasty.
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