During this pandemic, practitioners have had the opportunity to reflect on and to alter best practices for scleral lens fitting. Due to the potential risk of infection with prolonged exposure, it is important for practitioners to develop practices and procedures to keep their patients and staff safe. It is critical to reduce the length of time that patients are in the office and to decrease the number of in-office visits; this is especially true for scleral lens fitting and follow-up appointments, which can be time consuming. It is also important to limit the number of patients in the practice and waiting room at any one time to enable social distancing. Although physical distancing is in place, it is pertinent that practitioners maintain immense empathy when fitting scleral lenses.
To minimize patient time in the office, a telehealth appointment can be made prior to the examination. At this time, patient information—such as history of present illness, review of symptoms, medications, and other pertinent information—is obtained. At the telehealth exam, the goals, expectations, and methods of scleral lens fitting should be discussed. Practice updates including safely precautions and personal protective equipment may also be explained. In addition, review fitting expectations and type of fitting, such as diagnostic or empirical fitting.
It is important to educate patients that practitioners and the industry are moving away from diagnostic lens fitting and toward empirical fitting. The advantages of empirical fitting are that it is more customized, safer, and more efficient compared to diagnostic lens fitting. There are several methods of empirical fitting.
Impression scleral lens technology is a valuable tool in a scleral lens practice. One impression-based scleral device is indicated for highly irregular ocular surfaces and severe vision impairment that require high-quality optical correction. An impression of the eye captures curvatures of the entire ocular surface with accuracy within 1µm to 2µm. A customized scleral lens design is created through 3D scanning of the mold. Also available is an impression-based scleral lens that is indicated for standard to moderately irregular ocular surfaces. It is ideal for patients who require scleral lens correction and prefer a straightforward fitting process with a superior fit and premium optics.
Another technique when performing empirical fitting is to use scleral profilometry. There are several devices in this category. Two devices use fluorophotometry to obtain measurements after sodium fluorescein is applied. The camera of another captures 25 slices of the anterior surface as it rotates (taking approximately two seconds), without requiring fluorescein. With some of the devices, the eye remains in primary gaze, which minimizes the influence of extraocular muscle involvement. Another takes images in three positions of gaze—primary, superior, and inferior—and then stitches the images together. All of these instruments have algorithms that provide suggestions for selecting an optimal diagnostic lens, thus saving time. In addition, information about the optimal base curve and suggested values for the landing zones are also provided.
One instrument has a built-in database of lenses. Practitioners select the desired lens brand and overall diameter, and the device will recommend a starting sagittal depth and landing zones. Other devices are designed to work with lenses from specific manufacturers, although the data can be also be used for other designs. A number of laboratories can use data from one of the instruments, either by providing a fitting guide specific to the lens brand desired or by directly importing the data file into their lens design software.
Data from some of the instruments can be directly exported into scleral lens fitting software to generate a specific manufacturer’s scleral lenses. Those scleral lenses are created using an ocular surface scanning software. Once an eye has been scanned, a practitioner is able to utilize the software to design a highly custom scleral lens in three-dimensional space, on site. This information is then directly sent through the software to the manufacturer.
For all of these instruments, scleral lens power is determined by placing a rigid lens of a known power and base curve on the eye and then over-refracting. Alternatively, an initial prescription may be calculated from the manifest spectacle refraction (if obtainable) along with keratometry values. If a lens was worn previously, initial lens power may be estimated from that lens. Another option is to use keratometry readings and the prescription of the fellow eye to approximate an initial lens power (assuming similar axial length). The initial lens serves as the first diagnostic lens; fit and power are determined from this lens.
After the initial diagnostic lenses are dispensed, lens changes with fit or power adjustments can be shipped directly to patients. The follow-up visit may be done by telehealth; an in-office visit is done to finalize the fit.
Fortunately, the future is bright for customized scleral lenses. By utilizing empirical fitting, we have the opportunity to provide excellent service and more customized lenses for our patients in an efficient manner.
Many thanks to Tom Arnold, OD; Daddi Fadel, DOptom; and Christine Sindt, OD for their wonderful insights on this topic.
Dr. Barnett is a principal optometrist at the University of California Davis Eye Center, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Alden Optical, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, EveryDay Contacts, Johnson & Johnson Vision, Ocusoft, Paragon Bioteck, RaayonNova, ScienceBased Health, SynergEyes, Tangible Science, and Visioneering Technologies.