Contact lens researchers update their study results

Issue: December 1999

FT. LAUDERDALE, Fla. – Many research abstracts involving contact lenses were presented at the Association for Research in Vision and Ophthalmology (ARVO) meeting. Primary Care Optometry News recently contacted the researchers for updates on those study results. Topics included using corneal topographers to fit and monitor different types of contacts, the effect of hard contact lenses prior to intrastromal corneal ring segment (ICRS) implantation, the ability of certain strains of virus to survive during various disinfection techniques and a comfort comparison between contact lens and spectacle wearers.

Topographers for soft lens fitting

While corneal topographers have typically been used to fit rigid contact lenses, Loretta Szczotka, OD, MS, FAAO, and her colleagues reported that topography may also help predict which patients will do well wearing soft toric lenses using standard fitting guidelines and those who may require specialty fitting. They are now exploring what approach to take with the patients who may experience problems with empirical fitting techniques. Dr. Szczotka said that the research should prove beneficial to practitioners who fit soft toric lenses. “It’s a huge potential for utility of topography, and a huge potential for helping solve soft toric problems,” she said.

Hard lenses and ICRSs

Terry E. Burris, MD, and colleagues studied the effect of hard contact lens wear on visual performance following ICRS implantation. While it was concluded that rigid wear prior to the procedure may affect the performance of the ICRS, Dr. Burris said that the study’s weakness was a very small sample size. He said that many rigid lens patients showed symmetrically toric topography patterns, which called for further investigation, because the researchers were not sure whether the symmetric toricity or the hard contact lens wear had occurred first. The group is now working on a study to delve deeper into other preoperative risk factors — such as corneal thickness and limbal diameter — in addition to hard lens wear and astigmatism to examine their effect on Intacs (KeraVision Inc., Fremont, Calif.) corneal ring segments. Dr. Burris said that practitioners may want to be sure a prospective refractive surgery patient has a stable cornea prior to surgery, particularly if he or she has worn rigid contact lenses.

Disinfection vs. adenovirus

adenovirus ---In the study, heat completely removed ade novirus from soft lenses, while it was still found in lenses cleaned with multipurpose solutions and hydrogen peroxide.

Kathryn Fethke, MD, and associates investigated whether adenovirus could survive contact lens disinfection. Originally, the group evaluated adenovirus type 8 by conducting three experiments on soft contact lenses and one on hard lenses. They found that in the soft lens category, with a multipurpose solution, adeno virus was recovered from nine out of 10 lenses; with hydrogen peroxide, the virus was recovered from three of 10; and with heat disinfection, there was no recovery of adenovirus. In the hard lens category, adenovirus was recovered from three out of 10 in the multipurpose solution. When the study was conducted using the type 19 strain of the virus, Dr. Fethke said that adeno virus survived on both types of lenses using a multipurpose solution; it was recovered in 10 out of 10 with hydrogen peroxide; but heat removed type 19 completely. Dr. Fethke said the next phase of the study would be alternative methods of eliminating adenovirus from lenses. She noted that while the virus does not present a large problem for soft lenses because many are disposables, wearers of the more expensive gas-permeable lenses would benefit. “We’re trying to find a practical way to tell patients with adenovirus how they can clean their contacts without having to throw them away,” she said.

Extended-wear lenses for amblyopia

Amgad Mostafa Dowidar, MD, of the Alexandria Faculty of Medicine, Egypt, evaluated the efficacy and safety of occlusion extended-wear soft contact lenses as a substitute to eye patches for treating amblyopia. Forty patients with strabismic amblyopia, ages 3 to 9, were included in the study. Twenty received eye patch treatment for the normal eye, according to the age of the patient and the depth of the amblyopia, while the other 20 patients used opaque extended-wear contact lenses. Eighty-five percent of strabismic eyes using occluder contact lenses improved at least one line of visual acuity, compared to 70% in eyes using patches. In the contact lens group, complications included lens irritation and poor fitting; in the patch group, complications included skin allergies and poor compliance. Dr. Dowidar concluded that, provided anterior segment complications of occluder contact lenses are monitored and managed carefully, the lenses are a successful substitute for nontolerated eye patches for treating strabismic amblyopia.

P. aeruginosa with high Dk lenses

Researchers at the Department of Ophthalmology at the University of Texas Southwestern Medical Center in Dallas found a strong correlation between high Dk contact lenses and decreased binding of Pseudomonas aeruginosa to human epithelial cells. Volunteers were randomized into groups wearing lenses with a Dk of 100 or lenses with a Dk of 20 for 4 weeks. Daily wear with the low Dk lenses showed a significant increase in bacterial binding to epithelial cells. The high Dk lenses also showed a small increase; the increased difference in binding between low vs. high Dk test lenses was significant. The decreased incidence of binding produced by daily wear of high Dk lenses suggests that these lenses could significantly reduce the risk of ulcerative keratitis, the most significant complication associated with contact lens wear. “The new class of hyper transmissible materials that are now getting into clinical use will replace every other lens out there on the market because they are definitely superior,” said H. Dwight Cavanaugh, MD, PhD, who authored the study.

Comfort with spectacles vs. contacts

A study in Australia compared the comfort of contact lens wearers to that of spectacle lens wearers. Participants used the correction device for 1 year and completed subjective questionnaires with questions on vision and ocular and facial comfort. A second questionnaire asked about frequency of 20 symptoms. Vision was found to be similar in both groups, with the contact lens wearers showing a slight advantage. Contact lenses wearers experienced more burning, dryness, redness, watering, foreign-body sensation, stinging and filming. Patients wearing spectacle lenses were more likely to experience dull ache, pain in the eyes and scratchy, hot, tired eyes. Facial comfort was also greater in the contact lens group, according to Brien Holden, PhD, professor of optometry at the University of New South Wales.

Lipid, protein deposition

A Vistakon-supported study showed that deposition of lipids and proteins can vary significantly from contact lens to contact lens and from patient to patient. In a study conducted at Aston University in Birmingham, England, 20 subjects wore Bausch & Lomb Soflens 66 or Vistakon Acuvue lenses for 28 days. Each day, the lenses were collected and analyzed for deposits. The Acuvue lenses, classified as Food and Drug Administration group IV, were found to have increased surface and bulk protein spoilation, while the Soflens 66 lenses had increased lipoidal spoilation. Results varied significantly among patients. Fifteen percent of patients exhibited increased protein spoilation, and 25% showed increased lipid deposition. Intra-subject variation was approximately 30% for bulk protein, 40% for surface protein and 55% for lipid, according to the study authored by Lyndon W. Jones, OD, associate professor at the University of Waterloo.

P. aeruginosa adapting to disinfectant

The ability of cytotoxic P. aeruginosa to survive and grow during contact lens chemical disinfection appears to be related to the organism’s ability to adapt rather than a decreased efficacy of disinfectant over time. Researchers in Australia inoculated a preserved disinfectant with a cytotoxic P. aeruginosa strain in a contact lens case. After 7 days, the surviving P. aeruginosa (pre-exposed) were used to inoculate fresh disinfectant and the same disinfectant again after it was filter-sterilized. New P. aeruginosa were also used to challenge both fresh and filtered disinfectant. The pre-exposed bacteria showed significantly higher levels of growth at all time points from 4 hours to 7 days when compared to the new bacteria. Growth of the new bacteria was inhibited in filtered disinfectant compared to the fresh solution, suggesting that the growth of cytotoxic strains was not caused by the disinfectant becoming less effective. The exposure of the bacteria to the disinfectant appears to result in adaptation to the disinfectant or the low nutrient environment of the case, according to Carol Lakkis, BScOptom, PhD, FAAO, FVCO, of the Department of Optometry and Vision Sciences at the University of Melbourne.

Topographic changes with rigid lenses

Both apical touch and apical clearance rigid contact lenses cause rapid reversible changes in corneal topography, according to researchers in Australia. Ten patients were fitted with an apical touch lens in one eye and an apical clearance lens in the other. Topography was performed after 10 minutes and 1 hour of wear, and then up to 1 hour after the lenses had been removed. Data compiled by Helen Swarbrick, PhD, FAAO, a senior lecturer at the University of New South Wales in Sydney, Australia, showed that the topographic changes induced by the apical touch lenses were rapid and pronounced, while patients wearing the apical clearance lenses experienced a more gradual midperipheral steepening accompanied by apical flattening of the cornea. For both lens types, recovery toward baseline was not complete after the lenses had been removed for 1 hour, although the central corneal flattening recovered more rapidly than the midperipheral steepening. The central corneal flattening found under the apical clearance lenses and the relatively slow recovery of the midperiphery with both lens types suggest that the factors inducing changes to corneal shape and the nature of the underlying tissue changes may vary among different types of lenses, according to Dr. Swarbrick.

For Your Information:

Loretta Szczotka, OD, MS, FAAO, is the director of the contact lens service at University Hospitals of Cleveland. She may be reached at 11100 Euclid Ave., Ste. 3200, Cleveland, OH 44106; (216) 844-3609; fax: (216) 844-7117; e-mail: lbs6@po.cwru.edu. Dr. Szczotka has no direct financial interest in the products mentioned in her study summary, nor is she a paid consultant for any companies mentioned.

Terry E. Burris, MD, may be reached at 6950 SW Hampton, Suite 150, Portland, OR 97223; (503) 624-4814; fax: (503) 624-4904. Dr. Burris has no direct financial interest in the products mentioned in his study summary. He is a paid consultant for KeraVision Inc.

Kathryn Fethke, MD, may be reached at UPMC Ophthalmic Microbiology, Eye & Ear Institute, 203 Lothrop St., Pittsburgh, PA 15213; (412) 647-7211; fax: (412) 647-5331. Dr. Fethke has no direct financial interest in the products mentioned in her study summary, nor is she a paid consultant for any companies mentioned.

Amgad Mostafa Dowidar, MD, may be reached at 1 Beak Street, Bolkly, Alexandria, Egypt; (203) 597-6249; fax: (203) 425-5781; e-mail: aastf017@hotmail.com. Dr. Dowidar has no direct financial interest in the products mentioned in his study summary, nor is he a paid consultant for any companies mentioned.

H. Dwight Cavanaugh, MD, PhD, is the Dr. W. Maxwell Thomas chair professor and vice chairman of the Department of Ophthalmology at the University of Texas Southwestern Medical Center in Dallas. He can be contacted at 5323 Harry Hines Blvd., Dallas, TX 75235-9057; (214) 648-8074; fax: (214) 648-9061. Dr. Cavanaugh has no direct financial interest in the products mentioned in his study summary. He receives research funds through the university from Bausch & Lomb, CIBA Vision and Menicon.

Brien Holden, PhD, can be contacted at the University of New South Wales, Building R2, 22-32 King St., Sydney, 2052 Australia. Dr. Holden has no direct financial interest in the products mentioned in his study summary. He receives research funds through the university from Vistakon and Johnson & Johnson.

Lyndon W. Jones, OD, is an associate professor in the School of Optometry at the University of Waterloo. He can be contacted at School of Optometry, University of Waterloo, Waterloo, Canada N2L 3G1; (519) 888-4567; fax: (519) 884-8769; e-mail: lwjones@sciborg.uwaterloo.ca. Dr. Jones has no direct financial interest in the products mentioned in his study summary, nor is he a paid consultant for any companies mentioned.

Carol Lakkis, BScOptom, PhD, FAAO, FVCO, can be contacted at the Department of Optometry and Vision Sciences, University of Melbourne, Parkville VIC 3052 Australia; (61) 3-9349 7415; fax: (61) 3-9349 7498; e-mail: c.lakkis@optometry.unimelb.edu.au. Dr. Lakkis has no direct financial interest in the products mentioned in her study summary, nor is she a paid consultant for any companies mentioned.

Helen Swarbrick, PhD, FAAO, can be reached at Newton Bldg., 3^rd Floor, Sydney 2052, Australia; (61) 2-9385 4373; fax: (61) 2-9313 8604; e-mail: H.Swarbrick@unsw.edu.au. Dr. Swarbrick has no direct financial interest in the products mentioned in her study summary, nor is she a paid consultant for any companies mentioned.