Article

CONTACT LENS DESIGN & MATERIALS

WHAT ABOUT HYBRID CONTACT LENSES?

In recent years, scleral contact lenses (CLs) have become the specialty CL fitters’ first choice for correcting complicated corneal conditions (Walker et al, 2016). But what happened to hybrid CLs?

Hybrid CLs were first introduced into clinical practice in the mid-1980s (Abdalla et al, 2010). Since then, they have gone through a technological evolution that has taken them from CLs made from low-oxygen-permeable materials that were uncomfortable and commonly associated with complications to CLs made from high-oxygen-permeable materials that are relatively comfortable and much safer compared to past versions (Pilskalns et al, 2007). Hybrid CLs have a GP center that promotes clear vision, which is fused to a soft CL skirt that helps with centration and comfort (Pilskalns et al, 2007; Erdurmus et al, 2009). Therefore, hybrid CLs offer some of the best qualities of each modality, though there are still other considerations to be made before electing to fit a hybrid CL.

Advantages

Hybrid CLs are usually not considered until after both soft and GP CLs fail, likely because of inadequate fit, comfort, or vision (Hashemi et al, 2014). Modern hybrid CLs actually have a lot in common with mini-scleral CLs. Hybrid CLs are similar in size to mini-scleral CLs, and they are designed to avoid central corneal touch (Downie and Lindsay, 2015).

Hybrids CLs are often alignment fit, which subsequently provides a beneficial layer of tears between the cornea and CL, tears that can help mask irregular corneal astigmatism (Abou Samra et al, 2016). This layer of tears is generally thinner than what is commonly considered acceptable with scleral CLs, which suggests that hybrid CLs are less likely to induce corneal hypoxia compared to scleral CLs (Compañ et al, 2014; Bickle et al, 2017).

Hybrid CLs can also provide better visual and contrast acuity and a better quality of life compared to both soft and GP CLs in patients who have advanced disease, likely because the hybrid CL design reduces higher-order aberrations by providing good centration and central corneal vault while having the soft CL portion of the lens be the primary contact point with the eye (Lipson and Musch, 2007; Hashemi et al, 2014; Piñero et al, 2014).

Research also suggests that an experienced fitter needs only 1.8 trial CLs to obtain a good fit and that modern hybrids have a low risk of giant papillary conjunctivitis (Abdalla et al, 2010; Abou Samra et al, 2016).

Drawbacks

Not all patients are able to wear hybrid CLs. In fact, the top reasons that patients elect to not wear hybrid CLs are discomfort, cost, and difficulty of handling (Abou Samra et al, 2016; Carracedo et al, 2014).

Additional hybrid challenges include the need for practitioners to learn a new modality and the need for high-molecular-weight sodium fluorescein when evaluating hybrid CLs that have hydrogel skirts (Downie and Lindsay, 2015; Carracedo et al, 2014). Similarly, some patients indicate poor vision despite hybrid CLs having a GP center (Abdalla et al, 2010), and it usually takes patients longer to adapt to hybrid CLs than to soft CLs (Lipson and Musch, 2007).

In Conclusion

In general, patients are successful with hybrid CLs (Abdalla et al, 2010), though this modality might not be considered a first-line treatment because it is an advanced design with the above limitations. Nevertheless, hybrids may be a good option for patients who highly value quality vision and for patients who have high corneal oxygen requirements (Lipson and Musch 2007; Compañ et al, 2014). Overall, hybrid CLs are a good option for your patients who have advanced disease and who have previously failed with other modalities (Carracedo et al, 2014). CLS

For references, please visit www.clspectrum.com/references and click on document #267.