A Case of a Failed Automated Lamellar Keratoplasty
A Case of a Failed Automated Lamellar Keratoplasty
This case follows the contact lens management of a patient whose refractive surgery was unsuccessful.
By Travis M. Johnson, OD, FAAO
Automated lamellar keratoplasty (ALK) has largely been replaced by other, more predictable refractive surgery methods. Laser-assisted in situ keratomileusis (LASIK), photorefractive keratoplasty (PRK), intrastromal corneal ring segments, and conductive keratoplasty are more predictable refractive surgery procedures with less visual side effects for lower refractive errors. Phakic intraocular lens implants and clear lens exchange are considerably safer compared to ALK and provide significantly better visual outcomes for high refractive error (Morales et al, 2006). In the event that the corneal surface has been compromised, penetrating keratoplasty and posterior/anterior lamellar keratoplasty are surgical procedures that may be necessary to restore functional vision.
A non-surgical approach to restoring functional vision is specialty contact lens fitting. GP designs such as scleral lenses, reverse geometry lenses, and intralimbal lenses are excellent options for irregular corneas. These designs offer breathable fluorosilicone-based materials that are friendly to the tissue health of a compromised cornea. Specially designed GP lenses would be the first choice with most irregular cornea conditions; however, if comfort cannot be achieved, other hybrid and combination piggyback designs can be problem solvers (Donoso and Castillo, 2006; DePaolis et al, 2006; Caroline and André, 2005; Bergenske et al, 2002).
The purpose of this article is to describe the contact lens management for a case of a failed ALK procedure.
A 48-year-old caucasian male presented to the clinic wearing a soft contact lens in the right eye and no correction in the left eye. His distance and near visual acuity in the right eye was 20/30. His distance visual acuity with the left eye was hand motion with no ability to resolve letters of any size at any distance. He had a history of a failed ALK surgery in his left eye in 1988. The patient's right eye was corrected with a high-minus soft lens that was more than one year old. The poor comfort of the lens resulted in reduced wearing time, and the patient also noticed redness after several hours of lens wear OD.
The patient remembered that he had attempted rigid lenses on the left eye after it had healed and stabilized. He reported that he was never able to see very well with the rigid lenses and that he was most troubled by the lack of comfort. He stated that he had tried his best to adapt to the rigid lenses, but he was not able to wear them for any length of time without significant lens awareness.
The patient's refraction was –16.50 –1.50 x 050 in the right eye (20/30-2 at distance and 20/40 near). Refractive testing was not productive for the left eye. The right cornea was clear, but exhibited significant distortion over the central area, measuring 5mm in diameter. The epithelium was intact, but significant negative staining was present with fluorescein. The left stroma appeared distorted and irregular with significant disruption to clarity in the distorted area.
Corneal topography results OD were 47.54/45.73 @ 032 (Figure 1). Corneal topography results OS were extremely varied centrally. Sim Ks measured 57.79 in the steepest meridian and 42.83 in the flattest meridian. The peripheral cornea showed significantly different readings in the four quadrants. Generally, the cornea was flatter in the superior region above the midline. The cornea was flatter in the midperiphery below the midline, but there was significant steepening as the topography moves toward the inferior corneal limbus (Figure 2).
Figure 1. Topographical mapping of the severly myopic OD shows normal axial map, but a distortion is present in the instantaneous (tangential) map centrally, with some inferior steepening highlighted by the refractive map.
Figure 2. Topographical mapping of the post-surgical OS shows generalized elevation and depression across the central cornea in the Axial map and significant elevation and depression in alternating hills and valleys in the Instantaneous (tangential) map and refractive map.
Differential diagnosis in this case was not extensive given the surgically induced nature of the ectasia, although it was necessary to consider a predisposing factor to the ectasia. Fuchs' dystrophy was considered, but the endothelium appeared normal in the right eye and normal in the midperiphery of the left eye. We also considered keratoconus, but the corneal topography and slit lamp findings of the right eye did not demonstrate the hallmark signs of keratoconus. Because keratoconus is largerly considered a bilateral disease, the likelihood of keratoconus in the left eye was not significant. The case history did not reveal any infectious processes or degenerations. The patient was diagnosed with high myopia (OD) and iatrogenic surgically induced irregular astigmatism and corneal ectasia OS.
Contact Lens Fitting
The patient later returned to the clinic for specialty contact lens fitting. He had been wearing the Kontur (Kontur Kontact Lens) daily wear contact lens in his right eye with reasonable clarity and comfort. However, I attempted to fit a different daily wear design that would address the cylinder component of his prescription (Hydrasoft Toric XR, CooperVision). He was able to achieve 20/25 acuity at distance and 20/30 acuity at near OD.
The patient was interested in trying specialty contact lenses in an effort to regain functional vision OS. I first fitted him with a Softperm (Ciba Vision) lens (–13.00D) in the left eye that provided 20/30 acuity at near, which was a significant improvement. However, the patient needed a full diopter more in the over-refraction, so I decided to fit a piggyback combination OS using Night & Day (Ciba Vision) and the CAD (Valley Contax) GP design. The patient was able to achieve 20/25+ at distance and 20/30 at near with this piggyback lens system. However, he expressed some lid awareness and, as with many piggyback designs, there are always hypoxia concerns.
I next decided to pursue a different hybrid option for both eyes—the SynergEyes A (SynergEyes) lens. With this lens the patient was able to achieve 20/20 vision at distance and 20/40 at near OD and OS. I selected the diagnostic lens from the fitting kit using the mean K readings and rounding up to the steepest base curve closest to the mean K average. The patient was emerging into presbyopia and was educated as to the need for reading glasses over his hybrid lenses for optimum near acuity (the SynergEyes Multifocal was not commercially available at this point as an alternative). The patient has continued to return to the clinic every six months for evaluation of corneal health. Given the post-surgical nature of his left cornea, the increase in oxygen transmission is a welcomed improvement of the technology.
Specialty contact lens fitting requires knowledge of a variety of designs and materials. No one lens design can satisfy the many needs of patients who have corneas deformed from pathology or from post-surgical anomalies.
It is estimated that nearly 2 percent of post-refractive surgery patients will need further visual correction (DePaolis, 2008). Soft lens designs in post-refractive surgery patients often provide satisfactory fitting results, but fluctuating vision is the primary reason these lens designs fail. Reverse geometry contact lens designs can provide clear and stable visual outcomes in post-refractive surgery patients.
Discomfort is the primary reason that reverse geometry contact lenses fail in a segment of this population. Refractive surgery is often the alternative that patients turn to because of contact lens intolerance and because they want to be free from the hassle of contact lens wear altogether (DePaolis, 2008). Piggyback contact lens systems, in which a soft lens is used as a foundation lens and a GP lens is fit over the soft contact lens, can be an excellent alternative to stand-alone GP contact lenses—but hypoxia is always a long-term concern, although the use of silicone hydrogels and highly permeable GP materials can help reduce this concern. The combination can often also create lid awareness on the palpebral conjunctiva. This awareness is often tolerated for several hours, but the constant friction can be enough of an irritant to reduce wear time.
Softperm lenses were the most popular hybrid contact lenses of the late 1980s and 1990s. These lenses were the grandchild of the Saturn II hybrid contact lens. Such hybrid contact lenses offered good centration, good acuity, and relatively good comfort; however, the lack of oxygen permeability resulted in inflammatory consequences when overworn. High astigmatism would also cause significant lens flexure, making stable acuity difficult to maintain (Maguen et al, 1992).
The SynergEyes A lens received FDA approval in 2005. It offers a high-Dk/t GP lens center and a 30- percent water soft skirt. Currently, the SynergEyes lens is offered in a variety of different designs for single vision, presbyopia, keratoconus, and post-surgical vision correction. New designs with a high-Dk soft skirt have also received FDA approval and will soon launch. Each version is specific to keratometry reading, corneal shape, and optic zone.
In selecting a starting point for the SynergEyes A lens, the mean keratometry reading or sim K reading (topography) is a starting point. When selecting a diagnostic lens from the fitting kit, it is often successful to use the mean K readings and round up to the steepest base curve that is closest to the mean K average. It is necessary to place one or two drops of high-molecular-weight fluorescein inside the bowl of the SynergEyes lens for evaluation of the fit. Fluorescein placed in the eye after the lens is already applied will not flow under the lens enough to allow you to evaluate the lens-to-cornea relationship (Szczotka, 2003; Donoso and Castillo, 2006; Bergenske et al, 2002). The optimum fluorescein pattern shows apical clearance over the GP portion of the lens and touch at the 9mm zone on the midperipheral cornea connecting with the soft skirt (DePaolis, 2008).
Know Your Options
This case report illustrates the need for clinical knowledge of different specialty contact lens designs. If you experience difficulty because of limitations of one specialty lens design, do not eliminate all specialty contact lens fitting and deem it as not useful. The many specialty lens designs available give clinicians multiple options for fitting irregular corneas.
Post-refractive surgery corneas offer a wide spectrum of challenges that may require you to try several lens designs. Patients are very disappointed and frustrated when their refractive surgery goes wrong. A working knowledge of different specialty contact lens options is necessary. Even if a clinician is not interested in pursing a niche in specialty contact lens fitting, it is essential to be aware of the contact lens designs and what they can do.
It is also necessary for researchers in the contact lens industry to continue to improve existing lens designs and to invent new designs. No one contact lens offers the ultimate solution. All-day comfort, clear vision, stable vision, and cornea-friendly materials are all goals that the contact lens industry must strive to meet. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #180.
|Dr. Johnson is the founder of St. Croix Vision Center in Stillwater, Minn., and Advanced Vision Clinic & Optical in St. Paul, Minn.|
Contact Lens Spectrum, Issue: November 2010