Lavinio Scleral Critical Thinking

The Experts at Grin Eye Care Make “Contact” with the Future of Technology

Exciting developments in optometry/ophthalmology are bringing the future of contact lenses within sight.

An estimated 24 million Americans wear contact lenses and most notably they wear them for vision correction purposes. However, now that we have transitioned appreciably into the 21st century, that number will undoubtedly escalate with the advent of contact lenses that go beyond the proverbial purpose of correcting vision. They say the rearview mirror is smaller than the windshield for a reason, and while many individuals have enjoyed contact lenses simply for vision correction and perhaps overall aesthetic appeal, the road ahead is filled with some exciting advances in technology, bringing the future of contact lens wear into clearer view.

The types of contact lenses on the horizon speak to the type of science-fiction-like technology that just might make the movies jealous. Imagine, for example, using contact lenses for disease monitoring, such as delivering medication to glaucoma patients; treating allergies or even giving relief to patients with dry eye issues. What if a damaged cornea could be repaired, restoring vision using stem cells embedded onto a contact lens in a non-invasive manner? Even the technology used in infra-red glasses by the military is now being incorporated into a contact lens, using a thin form of graphite that produces an electric current stimulated by infrared rays, converting them into a visible image, with applications extending beyond contact lenses.

“They are also working towards putting this technology into windshields to improve driving,” noted Dr. Lori Berwald of Grin Eye Care, who joined Dr. Jennifer Johnson in an exciting discussion about the contact lens availabilities of today and the exciting advances of related technology of tomorrow. Through these trusted professionals with decades of experience in the eye care arena, Grin Eye Care is able to provide contact lens patients the newest available materials and types of contact lenses, always keeping quality and optimum eye health at top of mind.

A board-certified optometrist, Dr. Johnson has been with Grin Eye Care since 1995, specializing in comprehensive eye exams, treatment of various eye diseases, cataract and Lasik surgery pre-and post-operative management and also in the fitting of contact lenses on all types of patients. She has a strong focus on the fitting of soft, rigid gas permeable (along with scleral devices) and hybrid contact lenses for all patients, including those with astigmatism, loss of near vision, corneal disease and low visions.

Dr. Berwald, a 1995 graduate of the Southern College of Optometry in Memphis, Tennessee, worked for other high-profile metro area practices prior to joining Grin Eye Care in 2003. She specializes in the diagnosis and treatment of ocular disease, contact lens care, and pre and post-operative care of patients undergoing cataract and refractive surgeries. Dr. Berwald has also relied on her extensive experience in the realm of contact lens care and management to train ophthalmology residents and ophthalmic technicians and students at the University of Missouri-Kansas City.

Among the many advances in contact lens technology to which these doctors look forward include the auto-focusing lenses for presbyopia, a condition most people develop around age 40 that requires the reliance upon reading glasses.

“We currently have the multi-focal lenses, but they are not perfect for distance,” noted Dr. Johnson. “The auto-focusing lenses will be able to change focus depending on where you look.”

Dr. Johnson also referred to scleral lenses, available now, which were essentially the first contact lenses made back in the 1800s and are now used for dry eyes and other eye diseases. A scleral lens, also referred to as a scleral contact lens and an ocular surface prosthesis, is a large contact lens that sits on the sclera, creating a tear-filled vault over the cornea. These lenses are designed to treat numerous eye conditions that don’t necessarily respond to other forms of treatment.

“Scleral lenses are treatment for dry eye patients, keratoconus, and corneas that have been damaged from trauma. Scleral lenses will not cure these diseases, but do allow the patients to have clear and comfortable vision, something that may not be possible with glasses or standard contact lenses.” explained Dr. Johnson.

Some patients are even opting to undergo cataract surgery at a much younger age than may be medically necessary, if only to enjoy clearer vision without the hassle of topical contacts or glasses.

“Patients can have a clear lens extraction now, taking out the lens and still getting the benefit of a refractive procedure at a younger age,” noted Dr. Berwald.



But the excitement doesn’t stop there. Have you ever wondered what it would be like to become a real-life Terminator, a la Arnold Schwarzenegger? The exciting world of virtual reality may soon come to contact lenses.

“These contacts will be designed for people with normal vision, providing digital content over them which is incorporated into the contact lens. For example, they can establish an image in the lens for gaming,” noted Dr. Johnson, emphasizing these lenses are for entertainment purposes only, operating like a smart contact lens controlled by the blinking of the eyes. “These will have an application in the lens that can pull up information on people’s names and locations, and can be used with a companion device, such as a smart phone.”

Another exciting advancement in contact lens technology points to those with macular degeneration and low vision issues.

“These lenses are used to enhance what one sees by magnifying the image,” stated Dr. Berwald. “This can create improvement in daily activities, such as driving, reading or just writing a check because it gives that needed visual magnification.”

Other high-tech contact lens possibilities include a camera/video recording device in the lens that can be paired with high-tech glasses and controlled by blinking.

“Of course, that type of lens would come with some privacy concerns,” cautioned Dr. Johnson.

As researchers dive deeper and deeper in the realms of technology, they are unveiling potential new uses for contact lenses, including noninvasive means of monitoring diseases, such as patients who need to monitor blood glucose levels for diabetes or intraocular pressure associated with glaucoma.

“Not necessarily for vision purposes alone, health monitoring lenses can monitor certain conditions by looking at one’s tears to determine what is going on in the body,” noted Dr. Johnson. “These types of contact lenses will take measurements of certain elements in tears to measure glucose levels in the body. For diabetics, this would mean no more finger pricks to measure glucose levels.”

Once the tears are studied, the data would be reported to a platform, such as a doctor’s software system, through the use of blue tooth technology via a microchip in the lenses powered by a tiny (very tiny!) antenna.

“What still needs to be determined, however, is how close the glucose in tears correlates with actual blood glucose levels,” noted Dr. Johnson.



Other types of pending contact lenses include those that can measure a person’s vital signs. For example, in 2011, Sensimed released the first commercial smart contact lens that records specific changes in the curvature of the cornea. These disposable lenses, worn for just 24 hours once or twice a year, provide physicians data on intraocular pressure fluctuation (IOP).

“A patient’s IOP can fluctuate as much as 10 points in one day, and this type of contact lens would give the doctor a better idea as to the status of the patient’s glaucoma,” expressed Dr. Johnson, also noting that research has been conducted to determine if contact lenses are a viable means by which to deliver medication, such as ophthalmic drugs (eye drops) used for treating glaucoma.

And for those who are anticipating something out of those wild science fiction movies, research is being conducted into the use of contact lenses for electronic viewing purposes and augmented reality, combining real and virtual aspects to create a seemingly seamless world between real life and fantasy.

Since they have been introduced, contact lenses have changed the lives of people daily, improving not only one’s vision but also quality of life. As technology opens the door for increased uses for contact lenses, it would seem the opportunities for new uses for contact lenses are unlimited. However, because advances in technology take appreciable time, don’t call your eye professional today in anticipation of securing a pair of any of these high-tech contact lenses immediately. In addition to ample research and development, the prototypes also have to undergo numerous studies and clinical trials.

Additionally, no matter for what purpose contact lenses are made, either today or in the future, they still need to be deemed as a medical device and should only be dispensed and fitted by a trained eye care professional to ensure the highest level of safety and health for patients. For that level of quality, experience and trust, the eye care professionals at Grin Eye Care stand at the ready.

“We fit many patients with contact lenses and also attend numerous classes to learn the latest in cutting edge technology to understand better what we can provide for our patients,” emphasized Dr. Berwald.

For more information on contact lens technology, eye health and other ophthalmologic procedures, or to schedule a visit with Dr. Johnson or Dr. Berwald, visit Grin Eye Care at 21020 West 151st Street in Olathe; call 913.829.5511; or go online at grineyecare.com.


l-r: Craig Place, M.D.; Jeff Wongs, M.D.; Lori Berwald, O.D.; Jennifer Johnson, O.D.; Barbara Wolock, M.D.; Milton Grin, M.D.; Anne Wishna, M.D.; Breanne Niebuhr, O.D.; Emily Enright, O.D.; Jamie McGowan, O.D. and Jeffry Gerson, O.D.

913.829.5511    |    grineyecare.com


Critical Measurements to Improve Scleral Lens Fitting

Gathering as much data as possible can help streamline the process and provide better outcomes.

By Jason Jedlicka, OD

Release Date: September 2015

Expiration Date: September 1, 2018

Goal Statement:

This course reviews methods for capturing and interpreting essential measurements when fitting scleral lenses.

Faculty/Editorial Board:

Jason Jedlicka, OD, and Greg DeNaeyer, OD

Credit Statement:

This course is COPE approved for 1 hour of CE credit. COPE ID 46692-CL. Please check your state licensing board to see if this approval counts toward your CE requirement for relicensure.

Joint Sponsorship Statement:

This continuing education course is joint-sponsored by the Pennsylvania College of Optometry.

Disclosure Statement:

Dr. Jedlicka has no finanical interest in any products mentioned. Dr. DeNaeyer is a shareholer of Precision Ocular Metrology and received royalty payments for the Europa lens.


Fig. 1. Corneal topography display demonstrating a corneal diameter of 12.19mm, confirmed by manual measurement of 12.2mm.

Scleral lenses have always been a mainstay of a specialty contact lens practice, offering patients with irregular corneas and severe ocular surface disease alike the chance to benefit from lens wear. But the category has been enjoying a renaissance in recent years, as the evolution of scleral lens designs has given us more fitting options—namely, standard and reverse geometry designs, toric curves in the landing and transition zones, and toric and multifocal optics—that in turn allow us to offer these lenses beyond the core group of traditional scleral patients.

While this increase in scleral lens parameter options gives practitioners the ability to fit a wider range of eyes, it may make perfecting the fit itself more challenging. Technology, on the other hand, is providing information that can help us fit these lenses quicker and more accurately. 

This article reviews some of the newer approaches to the evaluation and fit.

The Limits of Diagnostic Sets

Traditionally, scleral lenses are fit using one or several diagnostic sets. Practitioners use accompanying fitting guides based on keratometry readings, ocular surface health and patient history to select an initial diagnostic lens; alternatively, they can simply choose a lens from the middle of the set to start with and adjust their selection accordingly based on the amount of lens depth needed. Some scleral lens fitters may opt to look at the profile of the eye they're fitting and use their experience to tell them which lens is most appropriate.

Fig. 2. HVID ruler for measuring horizontal corneal diameter.

These techniques, however, while sometimes accurate, are difficult to teach and unreliable overall. Keratometric readings provide little information about the ocular surface, even when combined with ocular history such as a diagnosis of keratoconus or surgical procedures. If blind-selecting a lens, practitioners face the issue of identifying the necessary depth adjustments—assuming the fitting set is appropriate for the eye shape to begin with. Thus, a more appropriate measurement system is needed.

Selecting a Lens

While scleral lenses, unlike corneal lenses, vault the cornea to rest on the sclera, it is still vital for the practitioner to understand the contours of the patient's cornea to ensure adequate but not excessive vault, which, after allowing for lens settling, should be approximately 150μm to 250μm centrally and then and taper back to eventually land on the sclera just past the limbus. Inadequate vault can result in cornea/lens touch and associated problems, as well as difficulty with lens removal due to capillary attraction; excessive vault can inhibit oxygen flow, patient comfort and ease of application. Aligning a scleral lens properly also lessens the need for high prescriptions that may reduce visual acuity, which can occur especially when fitting steep corneal lenses in keratoconus, for example. Corneal topography can be used to ascertain corneal diameter or horizontal visible iris diameter (HVID), corneal apex location and the sagittal height of the cornea at a 10mm chord. 

Anterior segment depth measurements obtained using optical coherence tomography (OCT) or Scheimpflug imaging is another way to improve the fit of a scleral lens. The initial fitting process can be streamlined by use of OCT or Scheimflug imaging, as these instruments obtain objective measurements of the depth of the cornea and sclera out to nearly 15mm, thereby providing a known starting point for diagnostic fitting.  In addition, these images allow the fitter to see the contour of the cornea and sclera, to help determine if a particular fitting set may be more ideal than others. OCT can also be used to evaluate the success of a fit at follow up by providing precise measurements of the tear reservoir and edge contour to the sclera after a period of wear, without having to remove or manipulate the lens on eye. 

Fig. 3. Corneal topography demonstrating the apex of the cornea located approximately 4.5mm inferior to the corneal center. This shape may be better fit with a scleral lens with a reverse geometry design.

Other scleral imaging instruments provide information regarding scleral shape and toricity to determine whether a lens should be ordered with toricity in the landing zone. Below are some methods for obtaining these measurements. 

HVID. Because the scleral lens needs to vault the entire cornea and limbus, it must be large enough in diameter to land outside the corneal-limbal zone. Corneal diameter measurements can be obtained using a corneal topographer—simply capture the topographical map and use the corneal diameter measure on the display (Figure 1). Some topographers may also offer the ability to measure HVID with a point and click line display. A handheld ruler (Figure 2), slit lamp reticule or slit lamp camera with measuring capabilities, as well as anterior segment OCT, can also be used to measure HVID. 

Corneal Shape. Evaluating corneal shape is a good next step in the scleral lens fitting process. Knowing where the corneal apex is will allow you to choose a lens with the most appropriate shape to match the cornea. If the corneal apex is within the central 4mm of the cornea, a standard geometry lens should work well; if the apex of the cornea is located outside the central 4mm, however, or if there are significant elevations (e.g., Salzmann's nodular degeneration) near the peripheral cornea, a reverse geometry lens design may be more successful (Figure 3)

Sagittal Height. Another useful measurement to aid in the scleral lens fitting process is corneal sagittal height. Found on many corneal topographers, it is the measurement between the geometric center of the cornea and the intersection of a specified chord length—in this case, 10mm (Figure 4). Average sagittal height from 10mm to 15mm for all eye types is approximately 2,000μm.1 Thus, by using the 10mm chord depth and adding 2,000μm for the sag of the 10mm to 15mm chord plus the desired vault, you can come very close to the proper sag of the lens needed. 

Fig. 4. Three-dimensional display of corneal topography shows corneal sagittal height measurement at 10.0mm of 1,906 microns.
Fig. 5. OCT image demonstrating a sagittal height of 3,760 microns at a 15mm chord.
Fig. 6. Pentacam image demonstrating a sagittal height of 4,230 microns at a chord of 14.64mm.

Take the following example: a 10mm chord demonstrates a sagittal height of 1,906μm. Based on a desired initial vault of 350μm centrally, a diagnostic lens in a 15mm diameter should be 4,256µm (i.e., 1906µm + 2,000µm + 350µm for vault = 4,256µm starting point for a 15mm lens). If the lens to be fit is larger than 15mm, the sagittal height will need to be increased incrementally, as the larger area of eye surface to be covered will mean greater overall depth. In my experience, having reviewed several scleral fits in retrospect, I find that an adjustment of approximately 300µm per millimeter of lens diameter is fairly accurate (i.e., 4,256µm + 600µm, for a 2mm diameter increase = 4,856µm sagittal height for a 17mm diameter lens).

Obtaining a cross-sectional image of the anterior segment using diagnostic imaging technology is another useful way to obtain a starting point for an initial diagnostic lens. The software included in these instruments can provide measurements for a variety of possible heights and widths (Figures 5 & 6), simplifying the initial lens selection process. 

Scleral Contour Measurements. Some instruments are capable of evaluating the shape of the sclera, which may help practitioners achieve a proper lens fit. Figure 7 shows an image of a highly toric sclera obtained from the Eye Surface Profile (Eaglet Eye), one of two such instruments (the other being the sMap3D by Precision Ocular Metrology; see "Virtually Fitting Custom Scleral Lenses"). However, while these instruments provide more information about the ocular surface than corneal topography, at this time they are so new that the data they provide cannot yet be applied universally to all scleral lenses with simple formulas or rules.

Virtually Fitting Custom Scleral Lenses

By Gregory W. DeNaeyer, OD

Fig. 1. Data from three eye positions is stitched together to form a 3D model.

The sMap3D topographer (Precision Ocular Metrology) uses a structured light approach for three-dimensional mapping to obtain measurements of the cornea and sclera with a 22mm maximum field of view. The sMap3D takes multiple triangulated measurements using a single DLP projector and two cameras positioned laterally on each side.

Fluorescein is added to the patient's eye, which is necessary for imaging the corneal and bulbar conjunctival surface. The patient is then instructed to gaze at a fixated light straight ahead while the eyelids are opened as widely as possible with assistance from the practitioner or a staff member. The practitioner focuses the eye and captures the image. Two additional measurements with the patient fixating up and down are taken in succession.

Fig. 2. Scleral elevation map and toricity.
The sMapPro software is able to stitch together the images taken in straight, up, and down positions to produce a three-dimensional model of the patient's eye (Figure 1). Stitching is a necessary step to obtain maximum area of the sclera that is occluded by the lids despite the eyelids being held open. A stitched model is required for measurement of the vertical meridians to determine accurate toricity measurements and over all sagittal depth value, which are used for custom fitting.

The sMapPro software gives sagittal depth data at any specified chord. Corneo-scleral topography and elevation maps can be evaluated. Scleral toricity can also be calculated from any specified radius from center (Figure 2). The virtual fit screen allows the practitioner to send the data directly to Visionary Optics for analysis and design of a custom Europa Scleral lens. A diagnostic lens does need to be applied for over-refraction to determine final lens power.

Fig. 3. Virtual fit scleral lens on a keratoconus patient.
Alternatively, the practitioner can custom fit the lens using the software's virtual fitting plots. sMapPro software allows for complete specification of any lens parameter to virtually adjust for corneal and limbal clearance, as well as custom back surface toricity. The sMapPro recommends a starting base curve based upon any desired initial amount of central corneal clearance. Peripheral curve toricity is calculated based upon the patient's maximum scleral toricity. The fitting software adjusts peripheral curve widths to ensure limbal clearance. Figure 3 shows a virtual fit of a Europa scleral lens for a patient with keratoconus.

Dr. DeNaeyer is clinical director of Arena Eye Surgeons in Columbus, Ohio, and a consultant to Alcon, Visionary Optics, Bausch + Lomb and Aciont. He is also the designer of the Europa scleral lens (Visionary Optics) and a shareholder for Precision Ocular Metrology (sMap3D).

Assessing Lens Fit

Fig. 7. Corneal and scleral topography obtained with an eye surface profiler indicate a highly toric scleral contour.Fig. 8. OCT images of an adequately vaulted scleral lens (top) and inadequately vaulted scleral lens (bottom).

Once the scleral lens is on the eye, OCT can be used to assess lens fit by providing information on central vault, limbal clearance and landing zone in relation to the sclera. The amount of desired central vault and limbal clearance varies somewhat from one lens design to another, as well as from one fitter to the next. Generally speaking, a settled scleral lens should have between 150μm and 250μm of central vault, which tapers down to a fraction of that (20μm to 40μm) over the limbus to eventually land on the sclera. A scleral lens with excessive or inadequate vault, or one that lands on or inside the limbus, needs to be reordered with the appropriate adjustments made to fix these deficiencies. Keep in mind these parameters may change somewhat from initial application to a time several hours later as the scleral lens settles into the tissue. 

With respect to limbal clearance, there is no "magic number"; rather, as long as some amount of clearance exists, the limbus should be able to tolerate the lens. Note, however, excessive limbal clearance may allow for conjunctival prolapse and possibly sectoral hypoxia due to a thick tear reservoir. Figure 9 demonstrates several OCT images of scleral lenses with varying degrees of clearance over the limbal area.


Fig. 9. OCT images of scleral lenses over the limbus, demonstrating ideal, inadequate and possible excessive clearance.Fig. 10. OCT images of scleral edge profiles. The top image appears to have a proper alignment to the sclera, the middle image is loose and the bottom image is tight.

OCT imaging can also be used to evaluate edge profiles. This is helpful in ensuring that the landing zone of the lens is acceptable in all quadrants. A scleral lens that is too flat will demonstrate edge lift on OCT. This flat edge will encourage debris to accumulate under the lens and fogging of the vision over the course of the day. A scleral lens that is too tight will demonstrate an appearance of lens "digging in" to the conjunctival-scleral complex. This tightness will create discomfort and redness over time, and may have more significant long-term effects on the ocular surface. OCT can be particularly helpful in comparing edge fit along different meridians in helping to determine if toric landing curves might be helpful to improve a scleral lens fit. Figure 10 shows several edge profiles. 

Fitting scleral lenses in the past has been more of an art than a science in many respects. The future of scleral lens fitting figures to be more scientific, driven by precise ocular surface measurements and software that can customize a lens to the individual eye. In the immediate term, using the technology that is available will streamline the fitting process while we wait for a technological revolution in scleral lens fitting to occur. 

Dr. Jedlicka is a clinical assistant professor at the Indiana University School of Optometry and president of the Scleral Lens Education Society.

References

  1. Kojima, R. Eye shape and scleral lenses. Contact Lens Spectrum. April 1, 2013.

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