KERATOCONUS AND DRY EYE

Severe Dry Eye in a Keratoconus Patient

When this keratoconus patient developed a thyroid condition, finding the right lens was a challenge.

By Luciano Bastos

Keratoconus can be a difficult condition to manage with contact lenses. But as trying as it can be to manage on its own, the challenge becomes even greater when keratoconus patients develop other conditions that impact their success with contact lens wear.

That is what happened with a patient in our clinic who was first diagnosed with keratoconus 40 years ago. She was first seen by my father, Dr. Saul Bastos, until 2004 when he passed away; she remains our patient today at Instituto de Olhos Dr. Saul Bastos (IOSB). Some challenging circumstances occurred over the course of her life, even up to the present day, that required us to continually monitor and adjust her lens fitting to preserve corneal physiological health and to maintain comfort and vision. The changes that we made along these decades helped the patient continue wearing lenses, but it required much work and research to find the correct solution for each challenge.

Patient History and Initial Lenses

The patient was diagnosed with bilateral keratoconus in 1974 at the age of 22 years old. Her keratometry readings were OD 46.50 x 48.00 @ 175 and OS 47.00 x 51.00 @ 70. She was successfully fit with Soper corneal GP lenses and required lens changes only about every two to three years during the first decade due to slow progression of her ectasia.

Her condition was successfully managed until 1994 when she developed a thyroid disease and, consequently, a thyroid-associated orbitopathy (a.k.a. Graves’ ophthalmopathy). She had the related symptoms, including eyelid retraction, eye exposure, tearing, foreign body sensation, and redness. She was prescribed preservative-free eye drops and instructed to wear patches while sleeping. At that time, my father suspected a thyroid disease and referred her to an endocrinologist.

She was treated during that year, and her thyroid condition was controlled, but she developed significant ocular changes. Interestingly, there were no visible corneal changes, and the corneal GP lenses that she was wearing at that time still looked good during the eye exam. However, the resulting exophthalmos caused increased tear evaporation and a wider palpebral fissure that had a negative impact on the fitting. The lenses frequently dislocated, and the patient experienced lens awareness.

To solve this new problem, my father asked me to develop a large, intralimbal GP based on our keratoconus design. The lenses were manufactured in a high-Dk GP material with a double base curve in the following parameters: OD 51.50D x 45.00D base curve radii (BCR), 12.5mm overall diameter (OAD), 6.5mm back optical zone (BOZ), –7.00D power with an aspheric periphery and OS 52.00D x 45.00D BCR, 12.5mm OAD, 6.5mm BOZ, –7.75D power. Although she became dependent on preservative-free eye drops, she was able to wear these lenses until 2004, when the symptoms of dry eye disease increased.

The patient’s keratoconus over the last decade has remained stable; it is not a highly complex keratoconus case. The challenge with this patient has been the collateral ocular effects from her thyroid disease and the resulting difficulties in designing contact lenses that she can successfully wear, as spectacles do not provide acceptable visual acuity.

Fitting a Mini-Scleral Lens Design

When my father passed away in September 2004, we were evaluating her case and I was already studying scleral lens technology. My father believed a mini-scleral GP lens would help us achieve a better result for her case. It was not until several years later that we finally conducted our first clinical tests with mini-scleral lenses on patients at IOSB; during the years until then, this patient continued wearing the intralimbal keratoconus design while instilling preservative-free eye drops every hour so that she could keep wearing her lenses.

In 2007, we made a first attempt to fit the patient with a 15.5mm mini-scleral GP lens design, which was a larger version of her intralimbal design. She had corneal toricity that was complicating the fit. She also had a small pinguecula nasally OD. Figure 1 shows both the nasal pinguecula and the corneal toricity illustrated by the localized lens edge lift near the inferior sclera. To view a video of how easily the patient was able to apply these mini-scleral lenses and an evaluation of the initial fit, scan this page using the Actable app on your iOS or Android device.

To view a video of how easily the patient was able to apply these mini-scleral lenses and an evaluation of the initial fit, click here.

Figure 1. Nasal pinguecula OD (left) and inferior edge lift due to scleral toricity (right).

She agreed to wear these lenses for one month. When she returned for her follow up, she reported that the lenses helped with her dry eye symptoms, but the comfort was not as good as with the intralimbal GPs. The problems that we faced with the mini-scleral lenses were that they moved on the eye a little more than the minimum allowed, and that air bubbles were entering the fluid reservoir near the area of inferior edge lift.

Taking a Step Back

We suspended that experiment with the mini-scleral lens design and returned the patient to her intralimbal GPs. In the last few years, she again reported problems with lens awareness after five to six hours of lens wear. She also reported that she had been wearing a previous lens that she still had from 2008 that was offering better comfort. When we examined her eyes with these lenses, we understood why she preferred them: they did not move at all, they were fixed in place with no movement after blinking and no tear exchange between the lens and the cornea. We removed the lenses and, fortunately, found no corneal hypoxia or edema, but we would not let her keep wearing these lenses because a lack of tear layer between the lens and the cornea could induce keratocyte apoptosis if the corneal epithelium was damaged, and it could also result in lens adhesion.

We immediately recommended a refit to try to achieve a better lens-to-cornea relationship, even if more frequent use of preservative-free eye drops was necessary. We also tried different materials with different properties to find one that could improve the tear exchange and tear layer.

Fitting Scleral Lenses

Since 2012, we have tried to design ultra-customized scleral contact lenses that could fit her abnormal, highly irregular toric sclera. Figure 2 shows the initial trial lens OD that we designed specifically for her in 2013. The highly irregular scleral toricity with steeper areas at the 225º and 70º positions prevented us from achieving an optimal haptic landing zone on the sclera. The patient’s left eye has a very similar shape, except the axes are at approximately the 120º and 315º positions.

Figure 2. The scleral topography OD is highly asymmetrical, with a steeper or depressed area at around the 225º (left) and 70º (right) positions.

In January 2014, we designed a more sophisticated scleral lens for this patient with greater haptic zone toricity to better accommodate the shape of the eye; however, it was not enough to properly land the lens haptic 360º around the sclera.

We also failed to adjust the lens sagittal depth (sag), which was lower than initially planned because of the alterations to the lens landing zone. When we alleviated the weight and made it flatter, the lens tended to better accommodate the eye; however, the sag was not the same, and I did not realize this until we saw the results. We managed to design and manufacture another pair with the sag corrected to avoid apical touch. Scleral lenses can be successful with a range of sag values, so you don’t need to be as precise with the amount of corneal clearance. But, after a few hours of settling, the lens may be too close to the cornea, especially in highly irregular corneas. So, as a rule of thumb, I believe more sag is desirable, depending on what you see with the trial lens and what you are planning to do with the final lens.

As discussed, the new lenses were designed in a way to compensate for the sag lost when steepening the small area affected and flattening the larger area where there was more compression and lens weight. It is important to mention that, despite reduced lens comfort with the scleral lenses when compared to the intralimbal GPs, the scleral lenses provided immediate relief from the dry eye symptoms. In addition, the overall appearance of the eye was fine except that the lens irritated the pinguecula.

Figure 3 shows a profile view of the lens itself, illustrating the nonrotationally symmetric haptic design. Figure 4 shows the results with the new design. Although the initial findings were better, when we examined the haptic zone and lens edge we found that the modifications were not enough for even landing around the entire sclera (Figures 5 and 6). We were not satisfied with this, and it was evident that we still needed a better scleral fit.

Figure 3. An ultra-customized scleral lens with a nonrotationally symmetric haptic design to accommodate a severely irregular toric sclera.

Figure 4. Fluorescein pattern (left) and corneal clearance (right) of the new scleral lens design.

Figure 5. The modified haptic zone was not enough to properly cover the entire sclera, but made a significant improvement to the fit.

Figure 6. The macro image (turned horizontally) shows the highly abnormal scleral toricity.

Considering Next Steps

It is undeniable that this patient could benefit immensely from a scleral lens fitting, not only as a means of vision correction, but also because of the therapeutic effect that the patient noticed on her dry eye symptoms as soon as the lenses were applied.

We want the patient to allow us to continue trying new lenses that may be better for her. Therefore, with each lens trial, we have talked with the patient about her condition, the challenges specific to her situation, and our fitting goals and possible outcomes with each attempt. One possibility that we discussed with the patient was to perform eye impressions and have custom lenses produced from her eye molds. While it is a good idea that we may consider in the future, the technology is costly and we currently have only two patients who have such highly abnormal scleral irregularity and toricity.

We are also considering designing another pair of scleral lenses with the necessary changes; the most recent pair was close to what we need compared to the initial attempts. Although, to date, we have not been able to produce scleral lenses that are successful for this patient, we will not give up and will continue modifying the design until we succeed.

It is important to mention that despite knowing the therapeutic benefits of the scleral lenses, our patient said that she would remain in her intralimbal GPs if given a choice. However, she may change her mind if we are able to fit her with scleral lenses that offer an acceptable result.

Case Resolution to Date

The patient continued to wear her intralimbal specialty GPs manufactured in a high-Dk material, but she still had problems with significant dry eye symptoms. Comfort with lens wear deteriorated to the point that she started wearing a lens in one eye only to rest the other eye for a day, then switching to the other eye on the following day.

We recently fitted her with the exact same lens design, but manufactured in the Hybrid FS material from Contamac. She has been very happy so far with her new lenses, wearing them for 10 to 12 hours a day without symptoms. The current lens parameters are OD 51.50D x 46.00D BCR, 10.8mm OAD, 7.2mm BOZ, –6.00D power, and OS 52.00D x 46.00D BCR, 10.8mm OAD, 7.5mm BOZ, –6.00D power. Figure 7 shows the lens fit. To see a video of the evaluation of this intralimbal contact lens design on the eye, scan this page using the Actable app on your iOS or Android device. The video shows the excellent lens-to-cornea relationship that we achieved with this intralimbal GP design. You’ll note the good fluorescein pattern and lacrimal exchange. This lens design provides comfort and the best visual acuity possible for the patient while preserving her corneal physiological health. She still needs to instill preservative-free eye drops in both eyes every hour, but otherwise the patient is very satisfied.

To see a video of the evaluation of this intralimbal contact lens design on the eye, click here.

Figure 7. The most recent intralimbal GP lens manufactured in the Hybrid FS material.

We were surprised to see this level of success with the new intralimbal GP lenses. While it’s too soon to take for granted that we’ve found the best contact lens design for this patient, the results our team has seen thus far are really encouraging. If the patient continues to have such a good wearing experience over subsequent months, we will let it go and reserve scleral lenses as a last resort.

Conclusion

Most corneal complications with GP contact lens wear occur due to poorly designed lenses and improper fits—or both combined, which is the worst scenario. But when corneal GP lenses are well fit, patients may prefer them over scleral contact lenses. This is especially true for patients who have worn corneal GP contact lenses for many years with no problems. Corneal GP lenses are easier to apply and remove as well as easier to clean and maintain. CLS

Luciano Bastos is the director and clinical instructor of specialty contact lenses at the Instituto de Olhos Dr. Saul Bastos (IOSB), and is the director and specialty lens consultant of Ultralentes, a small laboratory specializing in GP and scleral lens designs in Porto Alegre, RS, Brazil.