EXPERIENCES WITH ACUITY POLYMER’S ACUITY 200 MATERIAL
Acuity 200 is a next-generation contact lens material (fluoroxyfocon A) and features the highest gas permeability (200 Dk) of any GP material on the market, according to the company. Engineered using Acuity Polymers’ recently patented ultra-Dk technology, Acuity Polymers says that Acuity 200 offers exceptional permeability and wettability for healthy lens wear while providing excellent all-day comfort, whether in a scleral or corneal lens design. Eyecare practitioners are able to buy finished lenses from various labs using the Acuity 200 material.
I recently talked with practitioners who are actively fitting lenses made from the Acuity 200 material in their practices.
Please tell us about your general experience with lenses made from the Acuity 200 materials.
Kaj Verner Thøger Nielsens, an optician who practices in Denmark, has been been using Acuity 200 in semi-scleral and scleral designs for nearly two years. “With existing patients in my practice, I am a little conservative until there is a reason to change,” he notes. “However, Acuity 200 is the preferred material for new clients.”
Mr. Nielsens has experience with Acuity 200 in different lens designs. “In standard designs, such as spherical and peripheral-toric, I have seen only a small difference in performance using different materials. Depending on the thickness, there has been a change in the back curve/radius parameter over six-to-12 months,” he continues. “In my specialized design, a quadrant-toric semi-scleral, there can be a big difference in junction thickness. Acuity 200 gives me the same thickness but with a higher oxygen level and, at the same time, excellent comfort.”
He predicts that orthokeratology (ortho-k) lenses will be the next contact lens in which this material may be preferred to provide the healthiest conditions.
Lachlan Hoy, BAppSc(Optom)Hons, GCOT, of Australia, has also been using Acuity 200 for several years. “I have been lucky enough to use Acuity 200 since early 2018 for EyeSpace rigid GP lenses,” he explains. “Initially, we used the Acuity 200 ultra-Dk material for scleral lenses; now we use it for corneal and ortho-k lenses as well. In the specialty contact lens industry, we have seen improvements in manufacturing, lens design, corneal metrology, and coatings; however, we have not had a new material for a decade.
“Typically, as the Dk of a material increases, it is at the detriment other properties such as hardness and wettability” he continues. “I have been surprised to see this material have such good wettability, stability, and durability in a wide range of settings.
“From a manufacturing perspective, it is a great material to lathe cut, polish, and handle. As a clinician, having a material that delivers more oxygen to the cornea gives me the confidence to fit this lens to the most complicated and diseased eyes,” he adds.
Aaron Wolf, OD, of Austin, TX, agrees that the wettability provided by Acuity 200 has been a major benefit to his patients. “What I was hoping for in the Acuity 200 material was that my high-complexity scleral lens patients would gain the improved long-term safety of a highly permeable material without sacrificing wettability or comfort. And that’s exactly what I got!” he says. “Patients can’t tell any difference in comfort compared to their previously comfortable yet lower-Dk alternatives.”
Who are the best candidates for this material and why?
According to Dr. Wolf, the best candidates for Acuity 200 are patients who have mildly dysfunctional endothelium or corneal grafts or patients who require larger-diameter scleral lenses or have unusually high lens powers that require increased lens thickness. “These are the types of patients who we generally worry more about in scleral lenses,” he says, “so we really must strive for the greatest oxygen transmissibility possible.
Mr. Nielsens likes this material for patients who, due to wettability issues, are experiencing lens deposits. “This material provides a high level of oxygen and has performed better than expected regarding wetting and deposits. The wetting angle is 48º, which is similar to other materials. However, those materials can have dry spots and lipids, depending on cleaning,” he notes. “These issues have not been experienced often with Acuity 200 and have been solved by changing the conditioning solution when they do.”
Mr. Hoy says that a better question is “Who isn’t a candidate for this material?” “Some clinicians may argue that an ultra-Dk material is only necessary in the setting of scleral lenses, high-powered thick lenses, or when fitting diseased eyes such as those that have had corneal grafts,” he says. “Initially, I used Acuity 200 exclusively for scleral lenses and found that the ultra-Dk doesn’t come at the cost of other properties such as comfort, wettability, hardness, durability, light transmission, or UV protection. As a result, I now use it routinely for regular corneal lenses as well.”
How has this material helped with troubleshooting for particular patients? Tell us about any success stories in that regard.
Dr. Wolf points to the oxygen permeability as a benefit to a certain subset of his patients. “I have patients who have severe ocular surface disease and who require large-diameter scleral lenses for ocular protection. And because they can be in these lenses for multiple years, they can develop corneal vascularization in lenses of lower permeability but traditionally better wettability,” he says. “I’m finding that with the Acuity 200, I’m able to reduce any corneal hypoxia without sacrificing comfort or wettability in these already very dry eyes.”
As an example, he tells of a patient who has only one functional eye and who requires a large-diameter impression-based scleral to see. “This patient absolutely needs to wear her lens for long hours every day,” he says. “With the Acuity 200 material, I can rest easy knowing that she is in the best material to provide as much oxygen as possible to an eye that desperately needs this lens all day so that she can function independently and live a high-quality of life.”
For Mr. Hoy, Acuity 200 has helped with patients who are experiencing midday fogging with scleral lens wear, which is commonly reported by lens wearers after a few hours of wear. “Fogging can be due to post-lens tear debris, corneal edema, lens flexure on eye, a dirty lens surface, and poor wettability,” he explains. “Since using Acuity 200, the incidence of fogging has decreased dramatically, allowing for longer wearing time, clearer vision, and whiter eyes.”
He also notes that major astigmatism is commonly associated with corneal graft and requires GP contact lenses to provide clear vision. “Often, these eyes have blood vessel invasion to the cornea, thick cornea, and low endothelial cell counts. While GP contact lenses can provide clear vision, the wear of contact lenses can cause significant hypoxic stress to the precious donor tissue. Using an ultra-Dk material for these eyes is imperative.” he says.
He recounts the story of a 76-year-old female who had a corneal graft in 1976 and presented to him three years ago. “The corneal graft had 24D of astigmatism and 4mm of blood vessel invasion nasally to both the host and donor cornea. Her corneal surgeon had her using [bevacizumab] eye drops and was considering a regraft. Her unaided vision was 6/200, and best-corrected spectacle acuity was 6/60. A scleral lens was fitted with a toric-back optic zone radius of 9.0/7.0, 500 microns of toricity, and a back vertex power of +6.00/–10.50 x 180. She achieves 6/6 vision,” he says. “Three years later, she continues to wear her contact lens, the eye remains quiet, and the graft continues to survive.” CLS