A Pot Pourri on Contact Lenses*

Résumé

Contact lenses have been the most outstanding innovation in non-medical or non-surgical aspects of vision care in recent years. Progress has been steady and rapid over the past four decades in both the science and art of contact lens fitting. But have not our successes in this area led us to neglect the less spectacular procedures at our disposal?

For example, has the trend to simplify fitting procedures, to make the fitting less tiresome, less time-consuming for both patient and practitioner really resulted in improved quality of service? Has this trend improved the main objective, the end result of fitting - namely, an optical device to correct a specific visual problem?

Optometry earned its reputation because of its expertise in doing skillful and accurate eye examinations and by prescribing a variety of aids capable of satisfying the vocational and avocational needs of their patients. Contact lenses have limited abilities to satisfy the multifarious demands of our modern society and industry. Practitioners, perhaps because of the popularity of contact lenses and for fear of being considered old-fashioned, may not discuss openly the very limited optical performance of contact lenses when compared with conventional ophthalmic lenses. Could we not be doing a disservice to the patient and the profession?

A well-fitted contact lens must meet at least two criteria: it must cause no insult to the cornea and its physiology, and it must provide as accurate a refractive result as would a conventional spectacle lens. If we are interested in meeting vocational and avocational needs, we should ask ourselves whether even the well-fitted contact lens satisfies these needs. The answer would be in the affirmative for the majority of pre-presbyopes, but as age increases, the number of successful patients falls drastically. This is a challenge for the profession and the industry. Will contact lens designs ever be as numerous and complete as those available with spectacle lenses in order to meet al/ vision demands?

Optometrists should not forget that the contact lens is but one of the many devices and procedures available in the performance of their duty as vision care professionals. There is a "glamour" of a sort in contact lenses, but optometrical vision care is much more than the fitting of contact lenses.

Although the human visual system has a certain flexibility and can tolerate other than the optimum refractive correction, it is this writer's opinion that the fitting of soft contact lenses has tended to produce sloppy retraction. A spectacle lens in error by 0.50D sphere, or even 0.25 cylinder would likely be rejected and sent back to the laboratory for correction. Are we as prompt to reject a contact lens when over-retraction reveals that it is not the proper correction? What happens to this incorrect lens? Is it destroyed? Will the laboratory accept its return, or is it simply one more "slightly used" lens in an ever growing inventory?

Why should such an attitude prevail when one considers the tremendous amounts of money and effort expended on research?

It would seem that the answer to the preceding question is simply that clinicians and researchers have overlooked the primary objective of any lens -namely that it is a refractive device intended to compensate an optical or muscular defect of the human eye.

Researchers have done an outstanding job in helping to explain corneal physiology, in the development of materials more compatible with the requirements of corneal physiology, in the pro­duction of all necessary solutions. But have our efforts to improve the contact lens as a refractive device been on a par with our efforts to understand corneal physiology? Bifocal and toric lenses do exist, but fitting is still very much a hit and miss affair despite the improvements realized in the design of toric lenses. There is still a long way to go, particularly in providing a wider range of cylindrical powers and axis orientations, not to mention design parameters. Can we look forward to the day when soft lenses will permit, as is possible with rigid lenses, the practitioner to calculate the results of his/her prescription when placed on the eye? This is not beyond the realm of possibility, but our understanding of the performance and flexure of soft lenses, the nature and physical properties of present day materials, appears to be inadequate at the moment.

Will bifocal contact lenses ever become truly versatile and practical devices, a worthy competitor to the present array of multifocus spectacle lenses? Limitations of existing designs are barriers to the desire to continue with contact lenses when presbyopia is reached. The potential for future growth seems restricted by the limits of present designs: poorer acuity than with SV lenses, small near point fields, discomfort and lack of variation in near point powers.

What clinical procedures are available to better evaluate refractive results? Is the contrast sensitivity technique the ultimate, or are attempts yet being made to find "the ultimate", a simple, inexpensive test which all practitioners can readily integrate into their office routine?

Have we abandoned our efforts to provide the practitioner with an accurate tool to check all soft lens parameters? All offices have a vertometer of sorts to verify spectacle lenses, even though the laboratories have these instruments as well. It would appear logical that practitioners should be as well equipped to verify soft lens parameters as they do with rigid lenses, and regular spectacle lenses. Practitioners' confidence would be enhanced because they would know exactly with what they are working.

Improvement in contact lenses as optical correc­tions will not be achieved by any reduction in available lens parameters whatever the reason: to enhance production capabilities, to simplify fitting, or to reduce costs. Single base curve series, single diameters fitted to different corneae of different dimensions may not cause damage to the corneae, but what kind of refractive result ensues? Why do contact lens manufacturers and designers try to evade the basic rules of optics? It takes specific curves to produce specific powers for the materials involved. Is lens flexure adequate justification for the scrapping of scientific parameters? Why do clinicians let themselves be swayed by manu­facturers? Why do clinicians not boycott firms who refuse to provide lenses with all the required parameters?

What effect on acuity, accommodation, binocular relationships, aniseikonia and stereopsis results from the single base curve series? Has anyone ever taken th.e time to investigate the variations in resulting refractions for a series of eyes all having the same degree of optical error, but with different corneal diameters and curvatures? Will a lens with specifications 8.4/-3.00/13.5 properly correct pa­tients with keratometer readings of 400, 420, 440, 460, 480, all of whom are -3.00 diopter myopes? What happens with corneal diameters of 10.5, 11.0, 11.5? How many of these will give piano over­refraction? Plano over-refraction may be achieved by changing lens powers, but this may involve the introduction of variable and unwanted cylindrical effects. Certainly it involves a considerable in­ventory, which is contrary to the goal of reducing costs. Moreover, can the practitioner afford a significant inventory of several makes of lenses?

Speaking of inventory raises the question of the dubious merit of fitting from inventory. What technical advantage, other than patient conveni­ence, is to be realized from fitting from inventory? The patient loses any assurance that he or she will obtain a new and unused lens, free from aging deterioration. What happens to a lens found to be unsatisfactory after a few days, or even a few weeks? Does it go back into inventory as a "new, unused lens"? Is there any possibility that such a lens was not properly asepticised and disinfected, thus presenting some risk for future patients? Can the practitioner afford to discard the lens? If it could be done, would it?

There follows then a serious economic consi­deration. Professional fees should take into account the possibility of having to refit or exchange lenses, as well as to build and maintain an adequate inventory for trial purposes. Are such fees realistic considering the existence of price cutting outlets with slogans such as "Satisfaction guaranteed or money refunded"?

Does not the fierce competition between corpora­tions and the offering of lenses at lower and lower cost reduce the sources of funds available for research and development? Do discounts for volume purchase serve only to encourage the price cutters to enter the field?

In the rush by multinational corporations to corner the market, to mass produce lenses, one must seek their true motivation - quality vision care, or profits. Cannot the trend to reduce parameters more honestly be interpreted as profit based, rather than aimed at improving care? The clinicians must bear some responsibility also. One would have to look long and hard. through the I iteratu re to find any objections being raised by optometrists. Is the reduction in parameters the first step in the production of over the counter "throwaway" lenses, a feeling out of the market, of acceptability to the public and the professionals? Could not this lead to a situation similar to that of the "glazed goods" sold over the counter in department stores and other retail stores?

Would this be in the patient's best interest? Would not this approach involve risk that the patient would judge a symptom to be, instead, a dirty lens and simply exchange it for one at hand?

Among the many solutions available to practi­tioners and patients are decongestants. We question the indiscriminate use of such solutions by patients, but some optometrists tolerate their use, and even recommend them. A red eye is a warning, a symptom that something is wrong. Does not their use place some patients at risk? A red eye during an adaptation period is not unexpected. If only an adaptation symptom, it will cease in a few days, perhaps even hours. But a red eye beyond the adaptation period needs to be examined closely and decongestants avoided. Of course, a true red eye should be differentiated from an eye which is described as "bloodshot" by the patient, but which is normal for that particular individual. The wearing of contact lenses may draw attention to the presence of prominent scleral vessels and the contacts may be lamed. It is just such a situation which enhances the value of a prefitting, coloured photograph of the anterior eye. Who can say that it would not become an indispensible piece of evidence in the event, say, of suggestion of malpractice? Even more applicable, would it not allay any anxiety in the patient that the lenses were the cause of the redness?

Finally, what must one think of extended wear lenses? The key to their successfu I use and eventual acceptance by optometrists lies in the optical, chemical and physiological properties of the materials used in their manufacture, in essence, the durability of the material. However, have we also looked at the relationship between materials and the specific metabolism of the individual patient? Would a criteria for selection of a patient be found in such a relationship?

Whether long term effects on ocular tissues and physiology will limit their popularity and usefulness has yet to be determined with certainty. Are only the more venturesome practitioners and patients inter­ested at the present time? Will their introduction follow the same pattern as did the introduction of hard lenses? Will everyone jump on the bandwagon once their safety has been demonstrated, or perhaps before?

But what is the motivation behind the use of extended wear lenses? Historically, they were the brainchild of John de Carle of London, but could he, as an individual, have caused their widespread demand? What part have the professions, the public, the manufacturers played in their popularity? Is it the desire of the individual to always see clearly, at least at far, or is it a desire to eliminate the bother of daily removal and cleaning? What has the pro­fession to gain from their introduction? From a corrective, or optical aspect, can the technique really be described as "progress"? Physiologically, there has certainly been progress which has led to a better understanding of the cornea and its function.

The very nature of the device implies a much greater responsibility on the part of the practitioner and demands greater attention be paid to after care. Have criteria to permit safe patient selection been determined? Have adequate after care procedures and tests been established so that users are subject to minimal risk? Should the professions endorse or oppose the direct advertising of extended wear lenses by the manufacturers to the public? Would controls be in the public interest or would consumer groups fight them as contrary to the public right of freedom of choice?

Progress in contact lens work is a direct outcome of the research efforts and funds directed to this science. Whether this research is due to the work of individuals, small, independent firms or multi­national corporations is immaterial. Understand­ably, individuals do not possess the funds and facilities available to large corporations, but it must be recognized that, were it not for the many individual pioneer actions, the larger corporations would not have become involved. The rapid growth and development in the industry has resulted from the infusion of research funds by the larger corporations. Without them, progress would have been slower, but can we not ask if quality vision care would not have been better served by slower growth and less emphasis on profit for profit's sake?

Contact lenses have been a boon to vision care, and do serve to meet a very real demand. However, have they also become an obsession that blinds us to other modalities in vision care? Is it perhaps time to rethink our priorities and objectives as vision care practitioners, even if they happen to conflict to some degree with those of some colleagues and manufacturers, or even with popular trends?

As guardians of human vision, optometrists must answer these and many other questions before the profession gives unqualified approval to the direction in which contact lenses are moving.

* Written as a Guest Editorial for the Contact Lens Journal, November, 1984.