Scleral Contact Lenses: An Evolving Technology
BY JASON MARSACK, PHD
As a non-clinician working in the area of visual optics, my introduction to scleral contact lenses occurred fairly recently (within the past few years). As I studied the use of modern scleral lenses in today’s clinic, they at first seemed to be a recent introduction to the family of optical contact lens corrections, intended for use when the more ubiquitous soft and GP corneal lenses were no longer efficacious at solving a variety of patient complaints.
I quickly learned that scleral contact lenses have in fact existed in some form for more than 100 years, and that it is more appropriate to state that scleral lenses are resurgent rather than new. And as I interacted with clinicians, I found that the resurgence surrounding scleral contact lens design and fitting has, in large part, arisen from the versatility that this lens type brings to solving myriad clinical problems.
Origin and Decline
Reports in the literature by Pearson indicate that scleral contact lenses were first demonstrated in the late 1880s by three investigators (Adolf Fick, Eugene Kalt, and August Mueller) working separately (Pearson, 1989; Pearson and Efron, 1989; Pearson, 2007). The introduction of early soft contact lenses in the later 20th century resulted in fewer prescriptions for rigid forms of correction (Efron, 2010), as features of soft contact lenses continued to evolve to meet the needs (both visual needs and lifestyle needs) of a large segment of the population. Soft lenses are comfortable and relatively inexpensive, they’re designed to be frequently replaced and worn on flexible schedules, and they provide good refractive error correction including the more recent addition of presbyopic compensation, etc. If clinicians were to stock a single lens modality in their clinics (a modality that might successfully address most patient problems while at the same time would be accepted by a majority of patients), pre-packaged soft contact lenses would be an excellent choice.
But when the needs of patients are not well met with these soft contact lenses (e.g., in cases of patients who have corneal dystrophies, dry eye syndrome, ectasia, etc. [Foss et al, 1994; Cotter and Rosenthal, 1998; Romero-Rangel et al, 2000; Jacobs and Rosenthal, 2007; and others. Full list available at www.clspectrum.com/references.asp]), then clinicians must choose a correction that can be tailored to an individual patient’s needs. Such contact lens modalities include individual and specialty soft lenses, GP corneal lenses, hybrid lenses, and scleral contact lenses.
Recent Rise in Popularity of Scleral Contact Lenses
Simply put, scleral lenses are a versatile form of ophthalmic correction. They can address patient issues of contact lens intolerance by vaulting over the cornea, distributing the interface of the contact lens over the less-sensitive sclera. The entrapment of a tear lens between the cornea and posterior lens surface keeps the anterior surface of the eye bathed in fluid, reducing the deleterious impacts of dry eye conditions. And, like GP and hybrid contact lenses, the rigid nature of a scleral lens serves to provide a more regular first refracting surface, reducing higher-order aberrations and improving image formation.
From the point of view of a clinician, this single lens modality can be successfully applied to several conditions that often lead to contact lens failure; the literature is replete with reports of scleral lenses being utilized for these purposes (Romero-Rangel et al, 2000; Jacobs and Rosenthal, 2007; Shepard et al, 2009; Gumus et al, 2011; and others).
The increasing interest of clinicians in scleral contact lenses is reflected in both the increased quantity and popularity of courses related to this technology now being presented at professional meetings. As a snapshot, at the 2013 American Academy of Optometry Meeting, at least 10 lecture/workshop/special continuing education events were devoted to some aspect of scleral contact lens use.
New Technology and Expanding Applications
Today’s scleral lenses benefit from state-of-the-art equipment and materials in the design and manufacturing processes. Scleral lens fitting sets, slit lamp nomograms, ocular imaging, and the advanced aqueous solutions used to fill today’s scleral contact lenses address a host of fitting and ocular response factors.
An emerging front in scleral contact lens application relates to its suitability for customization. At least two research groups (including ours at the University of Houston) have studied scleral lenses as a platform for custom wavefront-guided corrections for highly aberrated eyes (Sabesan et al, 2013; Marsack et al, 2013). Interestingly, both of these groups had previously demonstrated the ability to customize soft contact lenses (Sabesan et al, 2007; Marsack et al, 2008; Marsack et al, 2007) prior to initiating work to customize scleral lenses.
Speaking only for our research group, we chose to study scleral lenses for individualized correction in keratoconus research due to their superior stability, the native aberration reduction resulting from the rigid nature of scleral lenses, and the improved comfort associated with “getting the lens off the cornea.”
Considerations When Choosing Whether to Fit Scleral Lenses
While an effective tool, there remain some aspects of scleral lenses that are challenging for both clinicians and patients. The large diameter of this lens type combined with its rigid nature can be, at first glance, intimidating for patients (“I’m supposed to put that on my eye!?”). Clinicians report that time spent with patients educating them on lens application, removal, and care is an important factor in successful scleral lens wear.
Scleral contact lenses may occasionally require removal and exchange of the fluid reservoir during the day to avoid fogging and to maintain optimal visual performance. This can be further complicated by the need for special tools (a suction cup to physically remove the scleral lens from the ocular surface) and specific solutions to replenish the tear reservoir (preservative-free saline).
Fitting fees as well as initial and replacement lens costs can also be important factors when considering scleral lenses.
The versatility of scleral contact lenses makes them an attractive option from a clinician’s point of view. The ability of scleral lenses to address complaints that lead to contact lens failure makes them popular with a certain segment of patients. While it is true that no single form of correction is sufficient to address all patient needs and/or personal preferences, it is clear that scleral contact lenses currently fill a vital space in the contact lens continuum. The resurgence of scleral contact lenses, now 100 years after their introduction, is evidence of that fact. It will be exciting to see how this technology continues to evolve over the next 100 years. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #220.
Dr. Marsack completed a PhD in Physiological Optics and Vision Science at The University of Houston, College of Optometry. His research interests include optical aberration of the eye, custom and pseudo-custom correction of optical aberration, visual performance, metrics predictive of visual performance, and ocular drug delivery.