PRESBYOPIC CL CORRECTION
Use of Presbyopic Contact Lens Corrections in Optometric Practices
This study found that California optometrists generally prefer to fit presbyopes with a contact lens correction that they're confident will succeed.
By Michael G. Harris, OD, JD, MS, Shawna Kuntz, OD, Cara Morris, OD, and Delma Faria Zardo, OD

Many different modalities of presbyopic correction are available, including bifocal and reading glasses, contact lenses and combinations of both. We designed a study to determine the use of presbyopic contact lens corrections in optometric practice. Additionally, we wanted to find out what factors might influence optometrists' choices of contact lens modality for their presbyopic patients. We also wanted to learn practitioner preferences regarding presbyopic contact lens modalities. Let's start with a review of available contact lens modalities for correcting presbyopia.

Historically Speaking

Presbyopes have worn bifocal spectacles since 1837, although Benjamin Franklin first invented the lenses in 1785 to compensate for the onset of his own presbyopia. Since the early 1980s, we've seen a surge in the development of contact lens options for presbyopes. Although these advances have improved the comfort, safety and vision that presbyopic contact lenses provide, potential vision compromise remains. Current contact lens options for presbyopes include distance contact lenses with reading glasses worn over them for near tasks (DCLs), monovision (MV) and bifocal contact lenses (BFCLs).

DCLs These lenses provide sharp distance vision and clear vision at near when wearing reading glasses over contact lenses. Patients continue to experience good depth perception and peripheral vision with this method. DCL presbyopic patients can use "half-eyes" (or granny glasses) that they can peer over the top of to see distance objects clearly. Unfortunately, these half-eyes have the stigma of being for old people, a label that many baby boomers wish to avoid. Other disadvantages of this correction method are that it doesn't free the patient from wearing spectacles and patients may find it a nuisance to remove the glasses for distance and then find their glasses for near work.

MV This is a contact lens fitting technique for presbyopic patients who wish to avoid wearing spectacles, but it may compromise vision to some extent at distance and/or near. Generally, MV patients wear a contact lens for distance on the dominant eye and a contact lens for near on the nondominant eye. When the patient views distance objects, the brain suppresses the blurred image from the near-corrected eye, and vice versa. You can assess MV success (which depends on the motivation of the individual) by using diagnostic contact lenses. In theory, it's easier to suppress blur in the nondominant eye.

Amount of add power relates to MV success. A reading add of more than +2.50D can potentially affect visual tasks such as reading or viewing distant objects because of the greater anisometropic blur.

The advantage of this modality is that for everyday use, spectacles aren't necessary. If a patient needs better acuity for specific tasks, then he can wear special glasses over the contact lenses. One example is spectacles that a patient wears while driving to correct the near eye for distance. Furthermore, MV patients tend to have a wider peripheral field compared to bifocal lens wearers. The main disadvantage to this modality is the adaptation period, which can last several weeks and may result in temporary blur at distance and near, headaches and fatigue. Other disadvantages include possible decreased depth perception, reduced visual acuity, ghosting from incomplete suppression of anisometropic blur and halos around point sources in low-illumination levels.

BFCLs These allow both eyes to see distance and near at the same time. They're available in soft and GP materials. The primary advantage of BFCLs in comparison to MV is better depth perception at both distance and near. Disadvantages include increased glare and visual difficulties at night and a possible decrease in far and near vision. BFCLs are available in two basic designs:

1. Translating. The top portion of a translating contact lens corrects for distance while the bottom corrects for near. To access the near portion, the patient must look down, thus placing the near portion in front of the pupil. The disadvantage to this type of lens, similar to that of bifocal glasses, is that the patient must move his eyes down to use the near portion of the lens. This design doesn't work well if someone needs to view close objects at or above primary gaze.

2. Simultaneous vision BFCLs allow light from both distance and near objects to enter the pupil at the same time and focus on the retina. Similar to MV, the brain must choose which image to ignore based on the location of the object. This type of BFCL allows a person to see both distance and near in all fields of gaze.

While outside the scope of this article, you can use any number of combinations of the previously mentioned options. Studies have found that patients prefer MV to all other presbyopic contact lens modalities and have had success rates as high as 80 percent. Patients attribute the success of MV over other presbyopic contact lens options to better night vision, better overall acuity and less fitting time. Most failures resulted from blurred vision at distance or near. Perhaps the most important factor in success is proper screening. An ideal MV patient is a low to moderate ametrope with an add power no greater than the refractive error. A highly motivated patient without a high demand for viewing small detail is more likely to succeed.

We developed a questionnaire to determine what type of contact lens modalities local optometrists prescribe to their presbyopic patients. We also wanted background information about the practitioners to identify what factors may influence presbyopic contact lens prescribing trends. We sent the questionnaire to Bay Area optometrists in four different counties. The questionnaire contained two sections: a background section and an investigative section.

Background Section Among other things, we wanted to determine whether particular factors about an optometrist's background might affect his willingness or ability to fit presbyopic patients with contact lenses. We began by asking respondents the following specifics:

• The year and optometry school from which they graduated
• The number of days each week they perform primary care/contact lens exams
• The number of complete primary care/contact lens exams each day

We also asked respondents in what type of setting they practiced (commercial, HMO, ophthalmology, group private practice, individual private practice, other). If practitioners responded "other," then we asked them to describe their practice setting. We also inquired as to the number of optometrists or ophthalmologists at their particular location.

We then asked the optometrists if they fit soft bifocal contact lenses (SBF) and/or GP bifocal lenses (GPBF). If an optometrist answered "no" to fitting either type of BFCL, then we asked him to explain why. We also asked respondents who indicated "no" to fitting both types of BFCL to send the questionnaire back without completing the survey portion because it contained questions about BFCL fitting.

Because we wanted to compare the optometrists' background factors to the preferred presbyopic contact lens modality, we asked if they had a preference for a particular modality. If they answered "yes," then we asked them to rank their preferences (1=most preferable and 4=least preferable) for SBF, GPBF, MV and DCL. We then asked them to rank (1=most appropriate reason, 4=least appropriate reason) the following reasons for their preference: ease of fit, less adaptation time, higher success rate or other. If an optometrist checked "other," then we requested an explanation.

Subjects

We mailed questionnaires to 415 optometrists practicing in four Bay Area counties in northern California. We obtained the names and addresses of the optometrists from the California Board of Optometry Web site. If more than one optometrist worked at a certain address, then we sent the survey to the optometrist whose last name came first alphabetically. If an optometrist worked at two different locations, then we sent a questionnaire to the first address listed under that particular optometrist. We sent another questionnaire to the other address if another optometrist worked there.

We mailed 89 questionnaires to optometrists in Alameda County, 28 to optometrists in Marin County, 128 to optometrists in San Francisco County and 170 to optometrists in Contra Costa County. We also reviewed the demographics in each county regarding total population, age range and income, which we obtained from Web sites for the 2000 Bay Area Census and the 2000 United States Census Bureau for California. HMOs employed three of the four optometrists who stated, "Has a Contact Lens Fitter In Office."

Analysis

We compared the preferred contact lens modality to the background information in the questionnaire. The preferred contact lens modality choices were SBF, GPBF, MV, DCL, "no preference" and "does not fit bifocal contact lenses." We classified only optometrists who marked "no" to fitting both SBF and GPBF under "does not fit bifocal contact lenses." We determined the number of years in practice by subtracting the year of graduation from 2004. We calculated the number of exams per month by multiplying "exams per day", "number of days worked per week" and 4.33 weeks per month. (We arrived at 4.33 weeks per month by dividing 52 weeks by 12 months.) If an optometrist responded with a range for number of days a week performing exams or exams each day, then we averaged the range and used the average. We also evaluated which presbyopic contact lens modality was least preferred of those optometrists who fit BFCLs.

Of the 415 questionnaires mailed, 186 came back (45 percent). We didn't include 23 of those questionnaires in our analysis for the following reasons: six surveys arrived after the allotted time period, 10 were returned from sender unopened, four were from either retired optometrists or those who had inactive optometry licenses, one optometrist did research only and two marked more than one presbyopic contact lens modalities as the preferred choice.

We compared the preferred contact lens modality and number of years in practice. We disqualified two questionnaires in this comparison because they didn't indicate the year of graduation.

We examined the relationship between preferred contact lens modality and number of exams each month. We didn't include three questionnaires in this comparison because two didn't indicate the number of days worked each week and one marked 10 days worked each week.

We compared the preferred contact lens modality and number of exams each day. We excluded two questionnaires because they didn't specify the number of primary care/contact lens exams each day.

We also compared the preferred contact lens modality with type of practice setting and determined the preferred presbyopic contact lens modality by Bay Area County.

Results

We designed our study to evaluate the use of presbyopic contact lens corrections in optometric practice and to identify factors that might be associated with optometrists' choices in prescribing contact lenses for their presbyopic patients.

MV was the most preferred presbyopic contact lens modality (Table 1). Table 2 shows that most respondents chose a preferred modality because of a higher success rate with that modality and that this was the primary reason why most respondents preferred MV.

More than half of the respondents (58 percent) marked GPBF as their least preferred modality. The main reason why respondents didn't fit GPBFs was "Poor Comfort/Unsatisfied Patients" (33 percent of respondents). Optometrists may prefer the quicker adaptation and greater initial comfort of soft contact lenses, which makes it challenging to convince them to try GP lenses. Twenty-nine percent of respondents who didn't fit GPBF indicated "Not Enough Experience/Too Complicated" as the reason. This suggests that the profession, the contact lens industry and the optometry schools need to provide better training in fitting of GPBF.

Four practitioners who didn't fit SBF gave the following reasons: "Visual Compromise" (2), "Too Complicated to Fit" (1) and "Too Expensive for Patients" (1).

The majority of returned questionnaires were from University of California Berkeley School of Optometry graduates (70 percent) and Southern California College of Optometry graduates (12 percent). MV was the preferred presbyopic lens modality of graduates from both schools.

Number of years in practice ranged from one to 50 years with an average of 19.5 years. Trends in our data indicate that optometrists who've been in practice for more than 30 years are less likely to fit BFCLs than optometrists who've been in practice for a shorter period. This could result from the lack of BFCL experience while in optometry school. Practitioners who've practiced longer than 30 years may have become accustomed to fitting MV or DCL and have become reluctant to try modern BFCLs. A higher percentage of graduates in practice greater than 30 years preferred MV.

The average number of exams each month was 193 exams, ranging from 30 to 476. The number of exams each day ranged from two to 26 with an average of 10. Optometrists performing more than 300 exams a month (45 percent) and more than 16 exams a day (60 percent) were less likely to fit BFCLs. (Forty-one percent of respondents who perform more than 300 exams each month didn't fit BFCLs.) DCL was the preferred presbyopic contact lens modality (30 percent) for those optometrists performing more than 300 exams a month and MV was the preferred modality (30 percent) for those optometrists performing more than 16 exams each day. Busy optometrists may choose DCL and MV because they take less time to fit.

In comparing the preferred contact lens modality and type of practice setting, optometrists who marked "other" indicated the following settings: Veterans' Affairs Hospital (1), hospital (1), refractive surgery center (2), nonprofit multi-disciplinary clinic (1), multiple types of practices (2) and not specified (1). A high percentage of optometrists practicing in HMO or "other" don't fit BFCLs. This could be because optometrists who practice in HMO settings tend to have contact lens fitters in office and those who practice in "other" settings may generally not fit contact lenses. Optometrists practicing in ophthalmology practices preferred MV (43.8 percent) and DCL (43.8 percent), while optometrists practicing in commercial setting preferred SBF (41.7 percent).

Optometrists in Marin County preferred SBF, while those in the other three counties preferred MV. This could be because Marin County has the highest per capita income, thus allowing Marin County patients to afford the higher cost of SBF.

The Mold and How to Break it

Our results indicate that optometrists generally prefer MV correction for their presbyopic contact lens patients, mainly because they experience a high success rate. Optometrists who see more patients each month, more each day or who work in ophthalmology practices tend to prefer the simpler modalities (MV and DCL). It's difficult to argue with the reasoning that the higher success rate of MV makes it the preferred modality; if optometrists have a consistently favorable outcome with one modality, then they may have little impetus to try another. They might only try other modalities when MV fails, which could result in optometrists having little practice in fitting the more challenging BFCLs and fewer patients wearing that modality. Patients may be "settling" for MV without knowing that other options might be better for them.

BFCLs may actually provide better results for some of the patients who currently use DCL or MV, but without the training to fit them properly and access to appropriate fitting sets, many optometrists are likely to remain reluctant to fit BFCLs.

As more baby boomers become presbyopic, their demand for the best contact lens option is likely to increase. For the contact lens practitioner community to keep up with the increasing demands and needs of their presbyopic patients, we need better education about presbyopic contact lens options, specifically SBF and GPBF. We also need continuing research to improve the design of presbyopic contact lenses and to enhance the development of new presbyopic contact lens modalities.

To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #114.

Dr. Harris is director of policy and planning, associate dean emeritus and is a clinical professor at the University of California Berkeley, School of Optometry.

Dr. Kuntz, Dr. Morris and Dr. Zardo are all 2004 graduates of the University of California Berkeley, School of Optometry.

The authors conducted this study through their affiliation with The Morton D. Sarver Laboratory for Cornea and Contact Lens Research at the University of California Berkeley, School of Optometry.

Additional data tables and a copy of the questionnaire on which this study is based are available below.