A New Hyper-Dk Option for GP Lenses
NEW HYPER - DK GP MATERIAL
A New Hyper-Dk Option for GP Lenses
Five clinical investigators discuss their experiences with a new hyper-Dk GP material.
By Craig W. Norman, FCLSA
Craig Norman is director of the Contact Lens Section at the South Bend Clinic in South Bend, Indiana. He is a fellow of the Contact Lens Society of America and is an advisor to the GP Lens Institute. He is also a consultant to B&L.
Dr. Anderson practices in Tampa, FL.
Dr. Jedlicka practices in Wayzata, MN.
Dr. Lee practices in San Francisco, CA.
Dr. Vicksman practices in Denver, CO.
Dr. Movic practices in Bloomington, IL.
A roundtable discussion recently took place with the clinical investigators of Boston XO2 a new hyper-Dk GP lens material from Bausch & Lomb that just received FDA approval. The roundtable panel consisted of clinical investigators Bruce Anderson, OD; Jason Jedlicka, OD; Kim Lee, OD; Sherwyn (Sandy) Vicksman, OD; and Wilson Movic, OD. The randomized study discussed in this roundtable compared 150 subjects who were dispensed acontact lens made from Boston XO2 (Dk=141) for one eye and a lens made from Boston XO (Dk=100) material for the contralateral eye. Patients wore the lenses on a daily wear basis and returned for scheduled follow-up visits over a three-month period. The subjects were successful GP lens wearers whom investigators refit for the study with similar lens parameters and who continued their habitual lens care regimen.
Assessments performed during the evaluation visits included refraction, keratometry readings, slit lamp examination, visual acuity (VA), lens surface wettability, centration, movement, comfort and deposits. At various intervals throughout the study both the subjects and the investigators completed questionnaires to comment on their experiences.
Following is the discussion that occurred during the roundtable.
Craig Norman, FCLSA (CN): Historically, a concern with higher-Dk GP lenses is that there's a trade-off between better oxygen transmission and lens performance characteristics such as wetting and lens flexure. What were your experiences during the study?
Bruce Anderson, OD (BA): I felt that Boston XO2 performed at about the same level as the Boston XO. Our patient record review showed that in terms of wettability the two materials were comparable. We also didn't experience any problems regarding lens flexure or variation in vision. The two materials were very similar in the way they performed.
Wilson Movic, OD (WM): When I added up the study scores, I found that our patients responded similarly to the two materials for both comfort and vision.
Kim Lee, OD (KL): Most of my patients were split down the middle as far as deciding whether the new material was better than the old. My scores showed that there wasn't a big difference between them.
Jason Jedlicka, OD (JJ): We had patients who had worn a variety of previous materials, some low Dk. Switching them to the study material seemed to make no difference in their ability to successfully wear their lenses. I would agree that they preferred the new material at least equally to the control.
|There is science behind this lens material, which is in its favor.|
BA: I'd like to quickly add that I totaled up our numbers, which I'm sure we all did, and my patients were exactly split down the middle — half preferred the study lens, half preferred the XO. So it's almost like a flip of the coin with how comparably the two lenses performed.
CN: This study evaluated only single vision lenses. Did you note any differences in the various powers of myopic prescriptions used?
KL: My group had a number of high myopes. We had a large Asian population who'd worn GP lenses for some time, and they liked the lenses made from Boston XO2. The study lenses performed equally well both subjectively and objectively.
JJ: We had a disproportionately high percentage of higher myopes, –7.00D and up, with the highest at about –12.00D. Everyone did well, and in that particular patient population where you're looking for more oxygen permeability because of lens thickness, I was satisfied with the patients' comfort and vision. We had some higher astigmatic patients as well, and their vision was at least as good as with their previous lenses. I was happy with the ability of Boston XO2 to perform on higher lens power prescriptions.
Sandy Vicksman, OD (SV): I was surprised by the prescription range of the patients we evaluated, with more than a few over –10.00D and with one at –17.00D. We found little difference between the test and control lenses.
BA: In terms of high myopes, I don't think we experienced any issues or problems. All of my patients were myopic. I had three patients with prescriptions above –10.00D, the highest at –14.50D.
CN: What about for hyperopia?
WM: I had one +7.00D hyperopic patient who did well the entire study with the first lens ordered.
JJ: I had only one hyperopic patient and experienced no problems with the fitting.
CN: Did any of you have patients with more than 2.00D of corneal astigmatism? If so, did you worry about any flexure or notice any flexure occurring?
KL: In my group about 25 percent had more than –2.00D of astigmatism. Their vision was good with their old lenses and with both test lenses. I didn't see any significant flexure.
BA: There were several higher astigmatism patients in our group, but it was really a non-issue in terms of the performance of the lens. The test lenses were comparable to what they'd worn before, and reviewing the patients' evaluation of their level of vision, the result was either the same or better than previously.
SV: About 20 percent of our patients had 2.00D of cylinder or higher, and there was virtually no difference between the XO and XO2 materials.
Comparison with Other Materials
CN: What type of lens materials were subjects previously wearing? Did any of you use the control material, Boston XO, before this study?
SV: I had patients wearing lenses made from low-Dk materials and a few patients wearing Menicon Z, which is another hyper-Dk material. The study patients did as well with the new Boston XO2 material as with their previous material. I typically use XO or Boston ES as my primary material, and living in Denver I lean more toward XO because of the altitude and lower oxygen. I prefer to use a higher-Dk material, and the XO works well.
JJ: For our specialty fitting in particular, Boston XO is by far our most popular material.
BA: Boston XO is my "work horse" material. For the study, I don't recall any clinical differences between the patients' previous lenses and the study lenses. But in reviewing what the patients noted, quite a few said their eyes looked less red with the newer lenses. I'd say one-third to one-half of the patients saw a subjective difference and felt like their eyes were less red and less irritated. They could see a difference from their habitual lenses.
CN: Have you used other hyper-Dk materials? And if so, did you notice any difference between them and the study materials?
BA: I use a moderate amount of Menicon Z material, primarily in special cases in which oxygen is critical. I worry sometimes about the solutions I have to use with the material. This was a non-issue in the study because the patients used their habitual lens care products and the study lenses performed well.
SV: Three or four of my patients were previously in the Menicon material, and they all did as well with their study lenses as with their previous lenses.
JJ: I don't know if we've touched on this, but up until this point my concern with using hyper-Dk materials has been not only with wettability, but with durability — surface scratches, softness of the material and flexure — so I use very little Menicon Z material for that reason. I've felt comfortable enough with XO for the cases in which I needed more oxygen. My experience with XO2 in this study was that it had the same characteristics as the XO material, so I felt comfortable with it and I trusted that it wouldn't have those same characteristics of the other hyper-Dk materials.
Lens Care Products
CN: Any comments regarding the use of patients' habitual lens care products in this study?
SV: Our patients used Boston Original, Advance and Simplus (Bausch & Lomb), plus some other solutions. It didn't seem to make any difference.
WM: Of our 24 patients, we had one who experienced deposit problems. It almost looked like protein deposits that form on soft lenses, although it might have been lipids. Nevertheless, it didn't present a corneal health problem, and it didn't bother the patient enough to discontinue the study.
KL: One of our patients used Equate and the rest used various Boston products. They were all fine. I believe our one patient who didn't do well resulted from noncompliance.
CN: How will a hyper-Dk lens material such as Boston XO2 fit into your practice?
BA: My hope is that it will become the standard material. I think that a higher-Dk lens is a benefit to anyone who wears contact lenses, just as higher-Dk silicone hydrogel lenses have become the standard rather than the exception. My goal is to fit patients with the most permeable lens I can that I think they can succeed with.
JJ: Today we're fitting larger diameter lenses more often. If this lens material were available today, I'd fit any patient with a GP lens diameter above 10mm, which is fairly common in my practice, in this material because of the permeability. Larger lenses move less and need more oxygen through the lens rather than around it. Also, I would immediately fit anybody who has a moderately higher prescription, especially infants and children who now are in XO, into the more oxygen permeable lens if there were no other differences, given the comparable performance of the materials.
KL: I feel that most GP wearers are high myopes who love their lenses and wear them all day long. They don't like wearing glasses, and some won't at all. If they wear their lenses for 16 hours a day, I'm all in favor of putting them into a hyper-Dk lens.
WM: There is science behind this lens material, which is in its favor. I feel that this material will become the standard of care.
CN: If a patient presents to your office wearing a mid-Dk lens and it's time for a change, would you consider moving him into a hyper-Dk material such as Boston XO2?
KL: It's your job as a clinician, and I do this every day, to explain, "You know what? There is something better. As your doctor, I'd like you to try this new product and I know it's going to perform well." Your patients come to you for your professional advice, and you owe it to them to upgrade them whenever possible to the newest technology. I think your patients will also notice and appreciate that you keep up with the newest and the best technology.
SV: At our mile-high Denver altitude I prefer higher-Dk lenses, whether silicone hydrogel or GP. So yes, higher Dk is something I will recommend.
BA: I'd feel confident about fitting patients into Boston XO2, and I would upgrade my patients.
JJ: Regarding patients who need a higher-Dk material, Boston XO2 is where I'm going with my patients. I think you can feel confident right away jumping on board with it without any reservations as soon as it's available.
CN: Would you consider Boston XO2 as the lens material of choice versus other hyper-Dk materials?
WM: I would, just for the fact that it doesn't require plasma treatment. That makes it a better material in my mind, and hyper-Dk benefits patients.
KL: With other hyper-Dk materials that require plasma treatment, the care regimen is a concern. That's not a concern with Boston XO2, which goes long way with me.
BA: This new lens material will be available from our local lab. That's important to me because I fit many special designs.
JJ: I don't use other hyper-Dk materials much because of issues with performance. I've traditionally used Boston XO as my highest Dk material. Boston XO2 will become an upgrade to those patients for more oxygen without losing any performance. CLS
Contact Lens Spectrum, Issue: October 2007