Article

SPECIALTY LENS FITTING: LEARN BY EXAMPLE

This case series provides scenarios that practitioners may face during scleral and specialty lens fitting.

Specialty contact lenses continue to evolve, increasing practitioner success for patients who can’t be helped with standard contact lenses. Innovative manufacturing developments have allowed laboratories to improve products and designs. New materials and lens treatments have helped reduce complications. Novel instrumentation and software is now capable of fitting custom lens designs for each individual eye. Finally, scleral lenses have become embraced by an ever-increasing number of practitioners to help improve the quality of life for patients who have severe corneal irregularity or ocular surface disease.

This article will summarize case examples in which specialty lens fitting has successfully managed common and uncommon ocular abnormalities.

Even though surgical procedures such as corneal collagen cross-linking (CXL), laser-assisted in situ keratomileusis (LASIK), and corneal transplants are effective at treating various corneal disease and refractive issues, contact lenses ultimately still often play a role in allowing patients to reach their full visual potential. In addition, contact lenses can be fit to accommodate any corneal shape abnormalities that may exist after these procedures.

CASE #1: SPECIALTY SOFT CONTACT LENS REFIT

A 41-year-old male diagnosed with keratoconus had complained of poor vision in his left eye with his current keratoconic specialty soft contact lens. His visual acuity (VA) in his left eye measured 20/60 and demonstrated no improvement with over-refraction.

CXL was recommended; however, during the interim, corneo-scleral topography of the patient’s left eye was used to fit a scleral lens. A 16.5mm back-toric scleral contact lens was successfully fit that provided 20/25 VA with his left eye. One month later, the patient had uneventful CXL.

Three months later, the patient reported for follow up after not wearing his left scleral lens for one week because he complained that it was uncomfortable to wear. Corneo-scleral topography revealed a significant change in his scleral shape post-CXL (Figure 1). The scleral lens was redesigned to incorporate a multi-meridian design. At a follow-up appointment after dispensing, the patient reported doing well and had 20/25 VA.

Figure 1. Sagittal plot of the patient’s left eye three months post-CXL.

This case highlights an apparent change in scleral shape three months post-CXL. For this patient, a multi-meridian scleral lens was required to provide a comfortable fit and improved visual acuity.

CASE #2: POST-LASIK

A 59-year-old female reported for contact lens fitting. She had previous myopic LASIK surgery and was currently wearing the following spectacle progressive addition lenses: OD –0.25 –1.00 x 007, 20/20 and OS –0.75 –0.75 x 172, 20/20. She had previously worn corneal GP lenses prior to undergoing LASIK, but postoperatively, her eyecare provider discouraged contact lens fitting secondary to her “flat” corneas and residual astigmatism. Corneal topography showed mildly oblate corneal geometry. Anterior slit lamp examination was remarkable only for a small paracentral scar of her right eye.

After a discussion of lens options, she was fit with 15.5mm multifocal mini-scleral contact lenses. Corneo-scleral topography was used to design the lenses with customized back-surface-haptic toricity. Front-surface optics included a 2mm center-near add of +2.00D for both eyes. At the initial dispense, VA was 20/25 in both eyes for distance, and the patient was able to read J1 at near.

On follow-up evaluation, she reported success with the lenses but desired a slighter stronger near power. Her nondominant left lens was remade with a +3.00D add, and she was happy with the comfort and vision of the final dispensed lenses.

Scleral lenses are an option for post-myopic refractive surgery patients, and multifocal power can be added to manage presbyopia.

CASE #3: POST-HYPEROPIC LASIK

A 34-year-old male reported for contact lens evaluation post-hyperopic LASIK. His manifest refraction was OD +4.25 –2.00 x 166, 20/40 and OS +3.25 –1.25 x 050, 20/50. Corneal topography showed significantly prolate corneas with mild scarring of both eyes as well as moderate scleral toricity and elevated nasal pingueculas for both eyes. Back-surface-toric haptic 16mm scleral lenses were designed and manufactured for each eye.

The initial lens for the right eye was designed with a customized edge lift to vault the nasal pinguecula. At lens dispense, his right lens was comfortable, with VA measuring 20/40. However, his left eye was uncomfortable and his vision blurred.

Examination of the left lens showed that there was impingement of the nasal pinguecula that was causing the lens to decenter. Another left scleral lens was designed with a customized edge lift, similar to the successfully fitting right lens. The new left scleral lens centered on the eye without compression or impingement and provided 20/40 VA.

It is important to note that significantly raised nasal pingueculas can disrupt the fit of a scleral lens, which negatively impacts vision and comfort. Customized edge lifts can allow a scleral lens to fit over the pinguecula, avoiding impingement and secondary lens decentration.

CASE #4: POST-LASIK WITH IATROGENIC KERATECTASIA

A 19-year-old female presented in 1998 post-LASIK with iatrogenic keratectasia. There were no pre-LASIK topographies available, and the LASIK was performed at a time before routine pachymetry. She had seen a corneal specialist once a month and exhibited progressive steepening and corneal irregularity. At that time, there also was no approved CXL in Australia. Best-corrected visual acuity (BCVA) in glasses was 20/200 OD and 20/80 OS. As a last resort, she was referred for a GP fitting before consideration of a full-thickness corneal transplant. At the time, it was felt that a corneal graft was inevitable.

She was fit with a 10.00mm corneal GP keratoconus lens design, which resulted in VA of OD 20/30 and OS 20/20. Over the next 19 years, she diligently returned for, at minimum, yearly reassessments and has had at least eight lens remakes over that time. Her corneal topography has remained virtually unchanged during this period.

The last GP fluorescein pattern (Figure 2) shows well-fitting lenses that have been virtually unchanged in sagittal height over this period. Over decades of fitting complex corneas, it is our anecdotal opinion that corneal transplantation should always be a last resort.

Figure 2. Fluorescein pattern of corneal GP lenses for a patient who has ectasia.

CASE #5: BILATERAL CORNEAL TRANSPLANTS

A 63-year-old female who had bilateral corneal transplants was referred for customized contact lens fitting in 2015. The grafts were considered end-stage, as they were approximately 40 years old. Best-spectacle VA was OD 20/60 and OS 20/200. Corneal topography was very irregular in both eyes.

We followed our normal fitting protocol, which rules out smaller-diameter GP lenses first before moving on to larger-diameter scleral lenses. We avoid hybrid lenses on most corneal transplants because we have found that the compression that these lenses apply to the donor-host junction tends to cause inflammatory complications.

The right cornea was fitted with an 11.2mm reverse geometry GP lens design, which allows for all-day wear with 20/25 acuity. The right cornea was severely ectatic and irregular, caused by thinning of the donor host junction, and could only be fitted with an oblate-shaped 17.0mm scleral design. The sagittal depth of this lens was 6,250 microns and required a 3.0D toric periphery to stabilize it with minimal scleral impingement.

Assessing and fitting patients who have high plus or minus prescriptions can be tricky. It is important to use a design and material combination that will provide the cornea with adequate oxygen, and you should also consider the size of the optical zone and the stability of the fit to help provide consistent vision.

CASE #6: HIGH HYPEROPIA

A 36-year-old male who had high hyperopia had habitually worn corneal GP lenses, but had recently lost his left lens. Although he enjoyed the vision with his previous lenses, he wanted a lens that was more comfortable to wear. Additionally, the patient is an avid outdoorsman and was frequently having difficulties with foreign body debris beneath the lens that would interrupt his activities. His refraction was OD +6.75 –0.75 x 110, 20/20 and OS +8.25 –1.75 x 080, 20/25.

After discussion, he was fit with customized soft toric daily wear contact lenses for monthly replacement. After dispensing and reordering with an over-refraction adjustment, his best-corrected vision with the soft contact lenses was 20/25 and 20/30 in the right and left eyes, respectively.

However, he was unhappy with the visual result. After additional discussion, he was refit with mini-scleral contact lenses. The scleral lenses were fit from corneo-scleral topography and had customized back-surface toricity using a material with an oxygen permeability (Dk) value of 140 to maximize oxygen transmission. After initial application, he immediately was happy with both the comfort and vision that the mini-scleral lenses provided (Figure 3).

Figure 3. A 15.5mm mini-scleral contact lens to correct high hyperopia.

Mini-scleral lenses were an ideal solution for this patient who wanted the improved optics that GP lenses offer with the additional advantage that scleral lenses have relatively improved stability and are able to keep out environmental debris that can lead to discomfort and interrupted wear. It is important to use a hyper-Dk material for high-plus lenses to maximize oxygen, as their center thickness will be relatively thick.

CASE #7: HIGH MYOPIA

A 23-year-old very-high myope presented for possible contact lens fitting. His manifest spectacle refraction was OD –26.00 –5.00 x 180, 20/80 and OS –28.00 –5.00 x 180, 20/100. His habitual spectacle prescription resulted in 20/200 in both eyes. Corneal topography was normal. Several options were considered:

  1. Custom Soft Silicone Hydrogels However, with this type of lens, there is a potential for patients to experience giant papillary conjunctivitis (GPC) issues.
  2. Small-Diameter GPs These lenses would need a lenticular periphery, and it is possible that there could be issues with a small optical zone.
  3. Hybrids These lenses would be a reasonable first option for most patients.
  4. Sclerals This was the lens option that was chosen due to scleral lenses’ stability and large optical zone.

The lenses were designed using corneo-scleral topography to rule out any significant scleral toricity. Only 0.50D scleral toricity was discovered; therefore, a spherical-back-surface trial lens was used. A –2.00D trial lens with a 45.00D base curve radius (BCR) and 16.00mm overall diameter (OAD) required approximately –30.00D over-refraction and could achieve approximately 20/50 OU.

On delivery, the lenses fit well with adequate apical clearance of 180 microns OD and 220 microns OS. Over-refraction was OD +3.25D and OS +2.50D, which resulted in VA of 20/20- in both eyes. The practitioner was nearly as shocked as the patient. Over the following months, the patient decided to learn how to drive and is expecting a driver’s license shortly.

While your patients may be “OK” in their current lenses today, that may not always be the case in the future. Over time, we have found that discomfort is a major determining factor in contact lens dropout. Rather than sticking with the status quo, practitioners should adjust their patients’ lenses to accommodate their current needs.

CASE #8: PLANNED REPLACEMENT SOFT LENS REFIT

A 40-year-old female patient was referred for contact lens evaluation. She had a history of high myopia and decreased visual acuity with her planned replacement soft contact lenses.

Entering VA with soft toric lenses was OD 20/25 and OS 20/100. Manifest refraction OS was –15.25 –1.50 x 083, 20/25. Anterior slit lamp examination was unremarkable. Contact lens refitting options for her left eye were discussed, which included refitting a soft toric, a corneal GP, and a mini-scleral lens. The patient was fit in a mini-scleral contact lens for her left eye.

Corneo-scleral topography revealed significant with-the-rule scleral toricity. A 15.5mm scleral contact lens was designed with back-surface toricity to match the scleral shape. Front-surface toricity was added to correct a small amount of residual astigmatism. The power of the dispensed lens was –15.25 –0.75 x 075, 20/20. The lens centrally cleared the cornea, and no haptic blanching was observed (Figure 4). The front-surface toricity was stabilized with the customized back-surface-toric design. The patient reported that the comfort of the scleral lens was better compared to her previous planned replacement soft lens.

Figure 4. A front-surface-toric scleral lens stabilized with a customized back-toric haptic.

For this patient, a refit of a custom soft toric lens could have been attempted, but a GP lens was chosen for the possibility of improved vision. A scleral lens was chosen over a corneal GP lens to take advantage of improved comfort and stability. Although she is relatively happy with her right soft lens, she is now considering a mini-scleral lens for that eye based on the success with her refit left eye.

CASE #9: DISCOMFORT WITH CORNEAL GP LENSES

A 36-year-old male was referred for keratoconus hybrid lens fitting due to discomfort issues in 2009. He had been fitted with small-diameter (9.5mm) GP lenses that often fell out of his eyes. The lenses were fit too flat on his conical corneas, which in turn was causing significant epithelial disruption.

Even though we believed that refitting the GP lenses could be achieved, it was decided that we would refit with keratoconic hybrid contact lenses so that he could compete in contact sports without having to worry about the lenses dislodging. These were successfully worn for approximately six years with the lens replaced in the same parameters each year, as there was no further keratoconus progression.

In 2016, he presented with significant discomfort of the right eye with lens wear. Vision was OD 20/20 and OS 20/30. The lenses were well-centered, but on removal, the right cornea was significantly compromised in the midperiphery. Changing the landing zone was not possible.

Because the patient was a private investigator, it was not uncommon for him to wear the lenses for 36 hours with no sleep. We refit both eyes with 16.5mm scleral lenses (Figure 5). Even though the lenses were very comfortable, they was impinging on nasal pinguecula and causing significant hyperemia. The lenses were remade with nasal notches (Figure 6). This refitting has kept the patient seeing and feeling well for the last 12 months.

Figure 5. A keratoconus patient fit with scleral contact lenses.

Figure 6. Notched scleral lenses that bypass pingueculas.

CASE #10: KERATOCONUS

A 30-year-old male patient reported having problems with his distance and near vision. His visual acuity had worsened continuously from the age of 17 secondary to keratoconus. The patient complained of significant light sensitivity and glare. Corneal GP keratoconus lenses were unsuccessful secondary to severe ectasia. He was then referred to our institute for a scleral lens fitting.

A complete examination of the anterior and posterior segments of both eyes revealed significant thinning of the central cornea as well as apical scarring and Vogt’s striae. Scheimpflug imaging resulted in a classification of grade 3 to 4 keratoconus for the right eye and grade 3 keratoconus for the left eye.

The corneal radii of the right eye were below 5mm, and the central corneal thickness was 290μm. With the left eye, the situation was slightly better; the radii were nearly 6mm, and the central thickness was 390μm. Uncorrected VA was less than 20/320 at distance and 20/160 at a 10cm working distance. No improvement was obtained with retinoscopy or manifest refraction.

The patient was fit with an 18mm scleral lens design using a GP material with a 78 Dk. We chose an 18mm scleral lens because the ectasia was relatively central and we did not need increased paralimbal vault.

The scleral lenses were evaluated with Scheimpflug imaging (Figure 7). This type of imaging is very helpful to check the fit of a scleral lens on the eye. The scleral landing was checked at the slit lamp.

Figure 7. An 18mm scleral lens on the right eye.

An over-refraction was completed when the shape and sagittal depths of the scleral lenses were adequate. The right lens (base curve 6.54mm and power of –18.75D) resulted in a VA of 20/80. The left lens (base curve 7.74mm and power of –9.75D) resulted in a VA of 20/50.

At a follow-up visit, the patient complained that his eyes became increasingly hyperemic during the day. The redness became worse after lens removal and remained injected for several hours. This was thought to be due to hypoxia, despite the relatively high-Dk material. The scleral lenses were 400μm thick, which resulted in reduced oxygen transmissibility. The patient discontinued lens wear.

As an alternative, we used a corneal topographer’s simulated fluorescein pattern software to determine whether adaptation with corneal GP keratoconus lenses would be possible. A small GP keratoconus lens would have some advantages over the scleral lens. For example, it would have a better oxygen transmission [Dk/t] value, and it would allow tear exchange under the lens, both of which would provide more oxygen to the cornea. On the right eye, a bitoric compensated GP keratoconus lens was applied, which fit well. Unfortunately, the optical result was insufficient due to the extremely short radii.

Right: base curve 4.80mm x 4.60mm, power –25.00D/–28.00D, diameter 9.00mm, eccentricity 1.40 x 1.28; VA with this lens was 20/200.

Left: base curve 5.90mm, power –23.25D, diameter 9.0mm, eccentricity 1.35; VA with this lens was 20/100.

Thus, the corneal GP lens was not an option. The patient was refit with a 15.5mm scleral contact lens with an approximate center thickness between 200 to 240 microns using a material with a Dk value of 100. The patient was successfully fit using diagnostic lenses in the following parameters:

Right: base curve 7.00mm, return zone depth (RZD) 1200, landing zone angle (LZA) 62/66, power –16.25D.

Left: base curve 7.00mm, RZD 1000, LZA 60/64, power –16.25D.

VA with the dispensed lens was 20/50 and 20/40, respectively. The lenses had an ideal fit centrally and peripherally (Figure 8). The mini-scleral lenses could be worn without problems for 12 hours without bulbar redness. After lens removal, the eye no longer had a “rebound” effect.

Figure 8. Mini-scleral lens on the patient’s left eye.

The basic prerequisite for managing complications is to know the different products, their designs, and possible influencing variables. This case is a good example of a reduction of the scleral lens thickness and the optimization of the material properties. As an alternative, practitioners should think of custom-made corneal GP lenses, which can also lead to success with a modified geometry. A corneal lens provides the cornea with more oxygen compared to a scleral lens due to the smaller overall diameter and the tear exchange under the contact lens. It is not possible to fit all patients with the same product.

CONCLUSION

The improvements in specialty lens manufacturing and design have allowed increased clinical success for managing patients who have not been helped with standard methods such as surgery, medications, and standard lens designs. The cases in this series demonstrate that diversity and creativity of a practitioner's approach is critical to addressing the specific needs of each individual. Educational opportunities, including workshops and lectures, are imperative for keeping up-to-date on key improvements of the future. CLS