Contact lenses: Still an evolving technology

Issue: January 1997

Brien A. Holden, PhD, is a professor of optometry at the University of New South Wales, the founder and director of the Cornea and Contact Lens Research Unit at the School of Optometry, University of New South Wales, and the director of the Cooperative Research Centre for Eye Research and Technology. The author of 118 papers and eight book chapters, Holden also holds two patents — one for the method of treating presbyopia with concentric bifocal contact lenses and another for flexible contact lenses. Cofounder of the International Association of Contact Lens Educators, Holden serves as association president. He also helped establish the International Society for Contact Lens Research and served as its president from 1982 to 1984. In this interview with Primary Care Optometry News, Holden discusses major breakthroughs in the contact lens industry, the direction of contact lens research and the impact of refractive surgery.

Primary Care Optometry News: What have been the major breakthroughs in the contact lens industry in the past 15 years?

Brien A. Holden, PhD: There have been four breakthroughs. Undoubtedly, the most important has been the development of high oxygen-permeable soft contact lenses to evaluate the potential for extended or continuous wear. These materials multiply the potential of contact lenses.

The reason for this is that people are seeking a permanent or semipermanent correction of their refractive condition, and this can be supplied only by continuous wear. Thus, during the past 30 years since soft lenses were invented, and up until 3 to 4 years ago, there has been only one high Dk soft material. That was silicone elastomer and it did not work because of a lack of movement on the eye.

It is clear that the resources of major contact lens corporations are being directed toward the development of a high Dk soft material, and this area is where the future of contact lenses lies.

The second most important breakthrough has been in the area of manufacturing technology. Low cost manufacturing has led us to the point where daily disposable contact lenses have become a reality. This low cost manufacturing has resulted from a tremendous investment in the production of contact lenses. The question is: How low will the cost go for daily disposable lenses? Will it drop to a dollar a day for the patient? If it does, these lenses will become the most convenient form of daily wear contact lenses. The mode of contact lens correction should be perceived as a continuum.

Glasses will never be outmoded, nor will contact lenses, even in the face of refractive surgery. Therefore, people will always want to use lenses on a daily basis or for occasional use, especially if there are still minor problems with extended wear lenses.

The third most important breakthrough has been the development of multipurpose solutions. These have changed the nature of contact lens care and maintenance, and when combined with disposable lenses replaced on a weekly or biweekly basis, they have provided an efficient system if patients are prepared to look after their lenses like they look after their teeth. This is currently the "bread and butter" system.

The fourth major breakthrough is the high Dk rigid gas permeable contact lens. What these lenses have proved, at least in 10 years of study at the Cornea and Contact Lens Research Unit, is that they can be worn safely and effectively for continuous wear with patients removing them only 2 and 3 times per year in some cases.

PCON: It seems that contact lens research has moved away from oxygen transmissibility and toward the study of surface chemistry, bacteria and contaminants. Do you agree that the focus should be on immunology and surface reactivities?

Holden: This question is a perceptive one, predicated on the assumption that as oxygen transmissibility improves to the point where the epithelium is kept healthy and the risk of infection is extremely low, we still need to look toward surface chemistry, bacteria and contamination. We need to prevent or limit these problems as they will impact the inflammatory response to contact lenses.

If one does not take care of the proteins that coat lenses and their tendency to attract significant bacteria, then one could end up with high Dk lenses that still cause inflammation. The unknown in this equation is the importance of the switch of conventional hydrogel materials to silicone hydrogels or fluorohydrogels.

The deposit characteristics and the bacterial contamination of the materials may be quite different. Interaction between the bacteria, the surface and the proteins may be modified by these different material chemistries and surface treatments.

PCON: The issue is refractive surgery vs. contact lens practice: Can you compare and contrast the two? Is there a race between them? Who will win? Or, can they coexist?

Holden: At the present time refractive surgery — even in its simplest form, laser surgery — is not attractive to the majority of the population. Results in the United Kingdom during the past 5 years indicate that only about 10,000 of a population of 60 million are prepared to have laser surgery each year, compared with about 3 million who wear contact lenses. It is not a competition between laser surgery and contact lenses. In fact, laser surgery will not significantly impact the contact lens practice or business.

Contact lenses are growing globally at about 7.5% per year; refractive surgery is growing very slowly. Figures from the United States indicate that a tenth of the number of people who are expected to have this surgery in the first 6 months are, indeed, having the surgery. Nevertheless, refractive surgery is very satisfying for many patients, particularly high myopes, if it is successful. (Although the chances of success in this refractive group are much lower than they are with low to moderate myopes.)

Refractive surgery will improve with time, and we will see new lasers with better fixation systems, more even distribution of energy and better optical design that will produce better results.

Wound healing will come under better control with time. However, it is also clear that a substantial number of surgeons are not happy with ablating Bowman's layer, and we believe there are significant controlling influences from Bowman's. It appears to be a major attenuator of healing and inflammatory responses, modulating the epithelial messages to the repair systems of the anterior eye. Without Bowman's, the system seems very often to be out of control and not finely tuned to the best optical result.

Laser surgery also suffers from the drawback that the laser companies have invested substantial amounts of money, which they need to recoup. They cannot afford to invest further in more sophisticated delivery systems or better corneal shape algorithms. An anterior corneal surface shape is needed to control the massive aberrations produced when a spherical ablation is performed over a small central zone of the cornea.

PCON: In North America, 12% to 15% of those who are able to wear contact lenses do so, and many consider this the saturation point. In other countries the percentage of contact lens wearers can be as low as 1%. Can you discuss your interest in taking contact lens technology to other countries?

Holden: Our figures indicate that 11% of the total population of North America wears contact lenses, including the United States and Canada. This represents about 32 million people. This number of wearers has been achieved:

without an extended wear contact lens that works, and in the absence of true continuous wear contact lenses that can make contact lenses incredibly convenient;
against a background of extremely bad press resulting from extended wear lenses causing infections;
in the absence of a wide distribution of products in convenient forms — such as disposables or extended wear — that correct astigmatism; and
without the development of any form of presbyopic contact lens to seriously rival monovision.

Thus, contact lens technologies have not reached the point where contact lenses are achieving, in my opinion, a fraction of what they are capable of achieving. We have daily wear contact lenses, which are expensive when disposed of on a daily basis and cause redness and dryness toward the end of the day. We do not have the convenience of being able to leave lenses in for long periods of time and we do not have lenses that truly challenge the comfort and simplicity of spectacles.

Contact lenses, however, could provide better vision than spectacles, more consistent vision than spectacles, plus 24-hour vision and convenience. We have yet to see this contact lens, and when we do, contact lenses will significantly challenge the 2.5 billion people who wear spectacles.

The final issue for contact lenses is the frontier mentioned: developing countries. To significantly advance the distribution and use of contact lenses worldwide we need products that are safe, effective and comfortable for extended and continuous wear. We need products that are widely distributed and marketed throughout the world.

We need practitioners who are knowledgeable and skillful. In China, a country of more than 1 billion people, there are only 2,500 contact lenses practitioners. We need patients who are aware of contact lenses and their value and advantage, and who have the economic wherewithal to afford modern products.

Although contact lens companies, in particular Bausch & Lomb and Johnson & Johnson, have stepped up as major sponsors of worldwide education, other corporations need to bite the bullet and provide opportunities for advancement.

For Your Information:
Brien A. Holden, PhD, may be contacted at The University of New South Wales, Sydney, 2052 Australia, Building R2, 22-32 King St. Randwick NSW 2031 Australia.