Apply clinical research results to your contact lens practice

Issue: June 2004

ByJennifer L. Smythe, OD, MS, FAAO

Jennifer L. Smythe, OD, MS, FAAO, can be reached at Pacific University College of Optometry, 2043 College Way, Forest Grove, OR 97116; (503) 352-2770; fax: (503) 352-2929; e-mail: smythej@pacificu.edu. Dr. Smythe has no direct financial interest in the products she mentions in this article, nor is she a paid consultant for any of the companies mentioned.

Keeping abreast of what is new in the literature serves many purposes. First and foremost, research provides answers to both basic science and clinical questions. Scientific study lends credibility to new products, techniques and modalities. Research can provide a much-needed reality check for clinical impression.

Recently, the literature has provided compelling ideas and answers for the contact lens practice and has even raised more questions about continuous wear, corneal reshaping and the correction of presbyopia. Often, the dilemma is to determine how to interpret the results of new research in a way that is meaningful for use in practice.

Continuous wear and corneal reshaping are two of the hottest topics in the research arena. New insight has been provided on the safety and efficacy of these new and improved versions of relatively not-so-new modalities (extended wear and orthokeratology). It has been well established in the literature that complications related to hypoxia have virtually been eliminated with high-Dk lens materials. Unfortunately, inflammatory, mechanical and infectious complications (although rare) are still a possibility with overnight wear.

Rick factors for high-Dk lenses

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Ortho-K with multifocals: This topography map was taken of one of Priti Patel’s patients in the Nova study. The map shows central corneal steepening from overnight wear of an aspheric multifocal fitted 1.5 D steeper than the manufacturer’s recommended fitting guide.

A study of 275 subjects by du Toit and colleagues reports a greater incidence of adverse responses in younger individuals (47% of those younger than 21 years old) wearing high-Dk lenses (Association of age, gender and ethnicity with the incidence of adverse responses with extended wear of silicone hydrogel lenses. Optometry and Vision Science. 2002;79:12S.). Men had a higher incidence of inflammatory responses, and Asians were at greater risk for mechanical complications.

It could be speculated that age and gender risks might be related to issues of compliance, whereas the ethnicity factor is most likely the result of lens-to-cornea/conjunctiva fitting relationships. What this means to a practitioner is that the modality may not be ideal for adolescents, teenagers and young adults. Patient education, appropriate fitting relationships and routine follow-up care is paramount for all continuous wear patients regardless of age, gender or ethnicity, but especially in individuals who are considered to be at higher risk.

In a study by Jennifer Choo, BSc, and colleagues at Pacific University, 15 healthy subjects swam in a chlorinated public pool while wearing a silicone hydrogel lens (PureVision, Bausch &Lomb) in one eye and a conventional hydrogel lens (Acuvue 2, Vistakon) in the fellow eye (Bacterial populations on silicone hydrogel and hydrogel contact lens after swimming in a chlorinated pool. OVS. 2003;80:12S.). After 30 minutes of water activity, the lenses were aseptically removed. Significant microbial growth was found on 27 of 28 lenses cultured, regardless of lens material.

In practice, patients commonly ask if it is acceptable to swim in their contact lenses. Although this study protocol did not attempt to correlate microbial growth after swimming with an increased risk of complications, it still seems prudent to make specific recommendations. If a patient is going to wear his or her contact lenses during water activities, he or she should consider tight-fitting goggles or fully clean and disinfect the contact lenses prior to overnight wear.

CRT: How long does it take?

In a 1-month study by Luigina Sorbara, OD, MSc, FAAO, and colleagues at the Centre for Contact Lens Research, 23 new contact lens wearers were fitted with and dispensed CRT lenses (Paragon, Mesa, Ariz.) for overnight wear (Refractive, keratometric and visual effects of CRT after one month of lens wear. OVS. 2003;80:12S.). Refractive error, keratometry changes and visual acuity were assessed at multiple intervals on days 1, 4, 10 and 28. From days 10 to 28, stable ametropia, acuity and subjective vision were achieved.

These data shed light on several things. First of all, the study highlights the importance of the 1-week visit with corneal reshaping. If treatment effectiveness at day 10 is the same as day 28, the 7-day visit is critical for refining or maximizing the lens-to-cornea fitting relationship. For the patient interested in CRT, knowing that stable, uncorrected visual acuity can be reached by day 10 (on average) may be very influential to the decision-making process as to whether or not to proceed with the modality.

Ortho-K with multifocals?

Refractive error changes and alteration of corneal topography have historically been unwanted side effects with high-eccentricity gas-permeable multifocal contact lenses. In a small pilot study, Priti Patel, BS, and colleagues from Nova Southeastern University College of Optometry, attempted to purposely induce a myopic shift, which could potentially be beneficial for the correction of hyperopia and presbyopia (Innovative uses of traditional technology for reversible correction of presbyopia and hyperopia. OVS. 2003;80:12S.).

Three presbyopic female subjects monocularly wore the VFL 3 from Conforma (Norfolk, Va.), fit 1.5 D steeper than suggested by the manufacturer’s recommended fitting guide, overnight for 7 days. Central steepening of the corneal topography and an increase in myopic refractive error (0.37 to 2.00 D) were observed. From the standpoint of research and development, this modality might be an opportunity for early presbyopia in emmetropes and low refractive error. In clinical practice today, these findings illustrate another reason for patient communication, especially when compliance with wear schedules is an issue and a corresponding shift in refractive error is noted. Problem solving would include decreasing wear time, flattening the base curve-to-cornea fitting relationship or re-fitting into a lower eccentricity design.

Compliance in high school students

In a study evaluating the “Emerging problem of social swapping of contact lenses in high school students,” Crystal Klaahsen, BS, and fellow students from the New England College of Optometry went into a Boston-area high school and distributed a voluntary, anonymous survey to contact lens-wearing students (OVS. 2003;80:12S.). Of the 30 respondents, 26% of them admitted to having shared their contact lenses with another individual. All of them were females, and the majority were 14 or 15 years old. Not surprisingly, the survey revealed that when the students were aware of the dangers of swapping contact lenses, they were more apt to reconsider the practice. These data reinforce the fact that patient education is paramount to all aspects of wearing contact lenses.

When fitting teenagers with cosmetic contact lenses, spend time talking about the risks involved with contact lens wear, and explain that the lenses are prescribed to fit them and only them. Although the fact that 26% of respondents had shared their contact lenses seems rather staggering, the take-home message from this study is the fact that patients, regardless of age, will consider the practitioner’s recommendation. It is our job to make sure those guidelines come out loud and clear. This could also be a practice management opportunity by distributing information on the dangers of sharing contact lenses to school health care personnel and counselors.