Hybrid contact lenses can be an excellent option for patients who require the crisp optics of a GP lens, yet appreciate the peripheral comfort of a soft lens. To obtain success with this modality, achieving the optimal level of comfort may involve multiple trial lenses beyond the manufacturers’ suggested initial lens. Furthermore, an empirical fit of these lenses can result in a longer period of time before a contact lens prescription is finalized if certain ocular measurements and aspects of fit are not considered.
A Study in Comfort
In a Ferris State University IRB-approved study carried out by researchers at the Michigan College of Optometry’s Vision Research Institute, 74 eyes of 37 subjects who had normal ocular health were fit with the SynergEyes Duette hybrid contact lens to assess factors that contribute to overall comfort during wear.
All subjects were neophyte hybrid lens wearers. Tests performed during the initial study visit included, but were not limited to, measuring distance LogMAR visual acuity, analyzing refractive status, measuring corneal curvature and horizontal visible iris diameter (HVID) by corneal topography, and biomicroscopy with white light.
Although the Duette hybrid lenses are fit empirically in clinical practice, a diagnostic fitting was then carried out to expedite the fit and eventual dispense of the study lenses. For this study cohort, the manufacturer recommendation of an 8.4mm (F) initial skirt curve was accurate in 46/74 eyes (62%).
Three clinical pearls are worth mentioning. First, lid anatomy impacted where the hybrid lens came to rest. If the initial lenses decentered inferiorly due to, for example, taut superior lid anatomy in a 19-year-old Asian female, a steeper skirt resulted in improved centration and overall patient comfort.
Second, in some patients who had a relatively smaller (Figure 1) or larger (Figure 2) HVID, the skirt curve had to be fit either flatter or steeper, respectively, than the initial trial lens to maintain lens centration. While HVID and keratometry findings are easily acquired ocular measurements, further research is being conducted to analyze their role and, specifically, the role of sagittal depth in hybrid lens fitting.
Third, to ensure adequate movement, the skirt was often fit flatter to preserve the lens dynamics and positioning of the initial fit.
Following training for care and handling on a daily wear basis, subjects wore their lenses for two consecutive one-week trial periods. At both the dispensing and one-week follow-up visits, adequate centration of the lenses was positively associated with overall subjective comfort.
When fitting hybrid contact lenses, it is imperative to measure all pertinent anterior ocular structures. While the soft skirt of a hybrid lens cushions the eye from the GP center, manipulating its parameters following correct base curve selection can improve the long-term comfort and success with this modality. CLS