SCLERALS & OSD
Fitting Scleral Lenses for Ocular Surface Disease
Defining fitting goals and patient expectations is an important first step in managing OSD with sclerals.
By Lynette K. Johns, OD, FAAO
The resurgence of scleral lenses in GP materials has opened up many opportunities for fitting complex corneas. In the setting of irregular astigmatism and keratectasias (keratoconus, keratoglobus, pellucid marginal degeneration, and post-laser-assisted in situ keratomileusis [LASIK] ectasia), many patients who were unable to be optimally fit with corneal GP lenses have another non-surgical alternative to consider. The use of scleral lenses to visually rehabilitate these patients is equally rewarding for both the patients and the providers, especially when surgery can be avoided.
Beyond Visual Rehabilitation
Inherent in the design and function of scleral lenses is the tear reservoir that optically neutralizes irregular astigmatism while at the same time constantly bathes the cornea. This feature is paramount to their success when treating severe ocular surface disease. The GP polymer also provides protection and acts as a barrier for fragile corneas against diseased tissue of the lids and trichiatic lashes. While scleral lenses have long been a successful treatment modality for visual rehabilitation in irregular corneas, they can be an invaluable treatment option to incorporate in the care of severe ocular surface disease.
It seems contraindicated to apply a contact lens to a dry-diseased cornea. A cornea that has punctate erosions could be at greater risk for infectious keratitis, for example. Why should the risk with a scleral lens be any different? Scleral lenses have proven to be an effective treatment modality when other conventional dry eye treatments fail. Studies have shown that chronic graft-versus-host disease (cGVHD), Stevens-Johnson syndrome (SJS), ocular cicatricial pemphigoid (OCP), congenital corneal anesthesia syndromes, and persistent epithelial defects (PEDs) can all be managed with scleral lenses.
Initial Approach: Set Goals Early
When beginning a scleral fit, it is very important to first establish the fitting goals with the patient and the referring eyecare provider. Examples of such fitting goals are visual rehabilitation, symptom mitigation, and surface support and protection. In certain patients, all three goals are relevant and apply. Some patients arrive with very complex ocular and medical histories; setting these goals and expectations early can prevent a poor outcome. For example, consider a patient who has a longstanding history of SJS and arrives with opacified, desiccated, and keratinized corneas. You may be fitting the patient for improved comfort while the patient is expecting 20/20 vision. Setting the expectations early can provide a successful outcome for the patient. It can also help you avoid the unnecessary stress of trying to pacify a patient who has unrealistic expectations.
If Only Eyeballs Were Shaped Like Balls
By having a good understanding of ocular surface disease and all of the ocular manifestations associated with each condition, you can better anticipate anatomical obstacles to fit around, inside, or over. Unfortunately, eyeballs are not spherical globes; they have toricity, asymmetry, and there are pingueculae and symblephara that are challenging for scleral lens fitting, especially in severe surface disease. The lids, too, provide another barrier to fitting. Examples include small apertures, forniceal foreshortening, and tarsorrhaphies. All of these ocular features can guide you in choosing an initial diagnostic lens.
A few scleral lens fitters are incorporating optical coherence tomography (OCT) to evaluate the scleral shape and to enhance or dictate the fit (Gemoules, 2008). In the absence of OCT technology, a diagnostic lens can help define elevations and depressions in the scleral shape. By evaluating the compression pattern of the conjunctival vessels beneath the haptic or landing zone of the scleral lens, focal surface elevations are confirmed if there is reduced perfusion in those regions.
Ocular Surface Disease Cases
The following cases are examples of scleral lens fitting for severe ocular surface disease. The patients were seen in consultation and fit by myself at the Boston Foundation for Sight (BFS) in Needham, Mass. Prosthetic replacement of the ocular system ecosystem, or PROSE, is a treatment modality that combines the collaboration of ophthalmologists, corneal specialists, and optometrists to manage complex corneal disease using custom fabricated prosthetic devices to replace or support impaired ocular surface system functions. The PROSE fitting doctor drives the complete device design with an automated CAD/CAM system directly to the lathes. The PROSE devices are available at BFS, a 501(c)3 non-profit institution, and its affiliated partner clinics domestic and abroad.
The cases and examples are intended to provide an overview of various scleral lens fitting concepts relative to specific ocular surface disease conditions. Even though PROSE devices were used in these examples, the concepts apply to commercially available scleral lenses as well. For the purposes of this discussion, scleral lenses in the following examples are defined as large GP lenses that vault the cornea and rest solely on the conjunctival surface. There is no different classification by diameter.
Exposure Keratitis: A Unilateral Case Patient #1 is a 60-year-old female with a history of bilateral ptosis repair. The left eye developed a lid retraction, and a subsequent procedure was performed. Ultimately, she developed significant lagophthalmos in addition to unilateral keratoconjunctivitis sicca.
The patient complained of extreme photophobia, ocular pain, dryness, and foreign body sensation OS that had devastated her quality of life. She remained primarily indoors for more than a year prior to the scleral lens consultation. The patient arrived with the full armamentarium of dry eye treatment including Restasis (Allergan), frequent lubrication, autologous serum, soft bandage contact lenses, and moisture chamber goggles. The right eye was unaffected, and slit lamp examination was unremarkable. Entering best-corrected visual acuity in the left eye was 20/60 that pinholed to 20/50.
Before applying a lens, we defined the fitting goals as: to improve the overall comfort, to visually rehabilitate the eye, and to protect the eye from further exposure and desiccation. Based on her ocular history, there was no suspicion of any anatomical hurdles to the fitting. Slit lamp examination confirmed these findings. There were dense superficial punctate erosions (Figure 1). The patient had poor vision due to the dense punctate keratopathy and an inability to keep the eye open for prolonged periods of time.
Figure 1. The top image is the initial clinical appearance of Patient #1 showing dense punctate epithelial erosions in the setting of keratoconjunctivitis sicca and lagophthalmos. The bottom image is the same eye after almost five hours of scleral contact lens wear. Note the smooth corneal surface and absence of staining.
The patient demonstrated dramatic immediate relief upon application of the first diagnostic device. The exiting visual acuity was 20/25 OS with an 18.5mm spherical scleral lens design. The total sagittal depth was 555µm. Wearing the scleral lens dramatically decreased the patient's corneal staining (Figure 1, bottom). Scleral lens wear supports resurfacing of the ocular surface in a relatively quick period of time. In our experience, the corneal staining will reappear after not wearing the device.
In exposure keratitis cases, scleral lens fitting is often straightforward. Pingueculae may be the only anatomical obstacle encountered. In general, the conjunctiva is relatively insensitive as compared to the cornea; however, some patients are acutely aware of the conjunctiva that is peripheral to the edge of the lens. In such patients, a large diameter is recommended to provide more surface area coverage and protection. Supplemental lubrication over the scleral lenses is strongly recommended, as debris will adhere to the exposure zone of the lens. Informing patients of front-surface debris early in the fitting will help manage patient expectations. Figure 2 shows accumulation of debris on the front surface in the exposure zone.
Figure 2. Front-surface debris in the exposure zone. Note the dried and caked on appearance. Patients still need to supplement with lubrication over scleral lenses.
Front-surface debris can be managed by having the patient remove the scleral lens periodically throughout the day to refresh the fluid and to clean the surface. Scleral lenses may require repeat plasma treatments, and different lens materials can be trialed. The patient may also clean the lens with a saline-wetted cotton swab while the lens is on the eye. It is a challenging management issue, but the benefits of the scleral lens outweigh the nuisance of debris for these patients.
Chronic Graft-Versus-Host Disease
Patient #2, a 47-year-old white male, complained of extreme dryness OS > OD—worse at night—and intense light sensitivity. He also complained of blur and redness. The severity of his visual blur was associated with the dryness symptoms of his eyes. The patient had a history of non-Hodgkin's Lymphoma and was treated with a stem cell transplant five years prior to the scleral lens consultation. Ocular symptoms began six months after the transplant and have continued to worsen over time. He was diagnosed with cGVHD by his referring corneal specialist.
Past ocular treatments included Lotemax (Bausch + Lomb) used with Restasis. The patient discontinued these ocular medications because of cost and his intolerance of ocular stinging. Oral doxycycline had been prescribed for approximately two months, but discontinued as the patient reported no improvement. Nighttime ocular ointments were attempted but not desirable because of the associated blur. Punctal plugs of all four punctae provided minimal relief, and the patient underwent cauterization of superior and inferior punctae OD and OS. He used lubricant eye drops every two hours. The patient took a variety of systemic medications for the non-ocular cGVHD.
Entering visual acuity with spectacles was 20/25 OD and 20/40 OS. Figure 3 shows the appearance of his corneal staining. The corneal staining of each eye appears fairly similar despite his left eye being more symptomatic. As in the last example, there were no significant anatomical obstacles that challenged the design. The goals for fitting this patient were to improve the ocular comfort and also to improve visual acuity. The patient observed immediate relief upon application of both diagnostic devices.
Figure 3. Pre-fitting photos of corneal staining OD and OS for Patient #2 who suffers from cGVHD.
The final scleral lenses were 20.0mm in diameter. He achieved 20/20 OD and 20/25 OS visual acuity. The patient reported optimal comfort all waking hours (Figure 4); ultimately, his goals were met.
Figure 4. Patient #2 (cGVHD) after 5 hours lens wear.
This patient began wearing 18.0mm devices in the beginning of the fitting process. As mentioned before, some patients are aware of the tissue that is not covered by the lens. He was successfully trained with application and removal of the 18.0mm spherical devices (540µm sagittal depth), but he complained of symptoms of wind and exposure outside of the area of the lens. His complaint warranted a trial with a larger, 20mm diameter device. He observed an improvement with this trial. The change in the diameter was essentially like starting over, but ultimately it was beneficial. His final correction OD was an against-the-rule (ATR), back-surface toric, 20.0mm overall diameter lens, 620µm sagittal depth from the flat meridian and 250µm difference between the flat and steep edge. The left lens was a 20.5mm overall diameter, ATR, back-surface toric design with 645µm of sagittal depth from the flat meridian and 250µm of toricity.
Along with ocular surface abnormalities, debris is the most common problem encountered with dry eye patients. If a spherical design was used in either eye, not only would Patient #2 suffer from front-surface debris, but it would be compounded with reservoir debris as well. The back-surface toricity improves alignment of the lens to the sclera and reduces the excessive tear exchange that carries the debris (Figure 5).
Figure 5. The first image shows diffuse front-surface debris in a patient who has keratoconjunctivitis sicca. The second image shows an example of debris in the reservoir of the device. Finding the path or pattern of debris provides an opportunity to improve the alignment of the device to the sclera.
Limbal Stem Cell Deficiencies There are a variety of limbal stem cell deficiencies that include—but are not limited to—aniridia, SJS, OCP, and eyes exposed to radiation, chemical burns, and even to contact lens wear. Findings include corneal neovascularization, pannus, keratinization of the palpebral or bulbar conjunctiva, corneal perforation, symblephara, scarring, and melting of the cornea. Patients who have these ocular conditions and manifestations suffer tremendously from photophobia, pain, dryness, and reduced visual acuity (Dua, 2000). Scleral lenses are a valuable treatment to protect the cornea and provide relief while improving vision.
Patient #3 suffered from SJS for complained of dryness and light sensitivity. He had an asymmetric presentation of the condition (Figure 6), which is not that uncommon in limbal stem cell deficiencies. The patient's entering best-corrected visual acuity was hand motion OD and 20/50 OS. Optimizing the comfort for both eyes was crucial, but improving the vision in the left eye was a high priority as well. His vision subjectively improved in the right eye, and he achieved 20/25 OS with a scleral lens.
Figure 6. Patient #3, who has a history of SJS from more than 30 years ago. OD demonstrates diffuse pannus across the cornea with a paracentral anterior fibrotic scar (left photo). Superior pannus that spares the pupil OS appears in the right photo.
A symblepharon that is too close to the limbus may disqualify an eye or patient from scleral lens candidacy. Patient #4 had a history of SJS. Her right temporal symblepharon began to encroach onto the cornea. Multiple attempts to refit to smaller lenses proved uncomfortable and time-consuming. Her lens was notched to accommodate the symblepharon (Figure 7, left), but the tissue continued to advance. The patient underwent a symblepharon lysis with mitomycin C, but a new inferior temporal symblepharon developed (Figure 7, right). When encountering symblephara, it is important to ensure that there is room for the lens to settle. Fitting inside of a symblepharon reduces the risk of scleral lens impingement. Prolonged impingement could lead to conjunctival hypertrophy in normal tissue, and the symblepharon may react more aggressively.
Figure 7. Patient #4 had an advancing temporal symblepharon that required a notch to accommodate in the left photo. The right photo shows that after symblepharon lysis, the tissue is avascular where the symblepharon once was, but a new symblepharon formed.
Common to all ocular surface disease patients, many arrive for scleral contact lens fitting with extremely “angry” hyperemic eyes. As a scleral lens is worn over longer periods of time, the hyperemia may lessen. As a result, the lens fit may appear too loose. Signs of this loosening are increased edge lift, increased tear exchange and, in some cases, bubble intrusion into the reservoir. As the inflammation subsides, the lens fit may require tightening of the outer curves.
It may appear trivial to define fitting goals that are seemingly obvious. In some cases, the cornea becomes so conjunctivalized that it is no longer uncomfortable. Subjecting such an eye to daily lens application and removal when there is no visual improvement is not a reasonable outcome. In fact, it may put the eye at risk for mechanical trauma and abrasions.
It is very easy for a contact lens fitter to become engulfed in the details of the fitting. This is particularly true in cases of complex corneal disease in which multiple ocular, systemic, and surgical treatments are employed at the same time. For example, a patient who has rheumatoid arthritis and secondary Sjögren's syndrome may benefit from all the therapeutic benefits of scleral lenses. However, if the patient has poor dexterity that would interfere with application and removal and he lives alone, how effective is the treatment?
Patients who have suffered for months or years can experience rapid and immediate resolution of symptoms upon application of a device. Regular monitoring of these patients is crucial because of the complex nature of their eyes and systemic health. Incorporating scleral lenses in the treatment of ocular surface disease is a truly rewarding experience. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #188.
|Dr. Johns is a senior optometrist at Boston Foundation for Sight. She is also adjunct clinical faculty at the New England College of Optometry.|