comparison of care systems on rigid gas permeable lenses

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Comparison of Care Systems on Rigid Gas Permeable Lenses

John Pole, OD, MSc, Mary Biolo, BSc, and Gerald E. Lowther, OD, PhD

ABSTRACT METHODS Four different care systems were tested with three

different rigid gas permeable lens materials. Eight patients wore different pairs of RGP lenses, using one care system on one lens and another on the opposite lens in a double masked study. The tear film breakup time on the front surface of the lenses, debris on the lens, and peripheral staining were measured after 30 min and 6 hr of wear on the first day and then after 6 hr of wear on day 7. The patients filled out a questionnaire on day 7 with respect to solution preference. With regard to objective results, there was a greater difference between lens materials than between the different solutions. Subjectively, the patients, in general, preferred the Boston care system.

PURPOSE

The purpose of this study was to determine the clinical effect of different commercially available care systems on gas permeable lenses. Other studies1-3 have indicated that some preservatives, particularly benzalkonium chloride, may bind to lens surfaces and may decrease the lens surface wetting angle of silicone/ acrylate lenses. However, benzalkonium chloride- preserved systems are approved for use with silicone/ acrylate lenses and apparently function well for some patients.

With the increase in number of different lens materials (silicone/acrylates, styrene-based polymers, fluo- ropolymers) and the different preservatives available i.e., benzalkonium chloride, thimerosal, chlorhexidine), it is important to know the clinical effects of each on the different polymers. The relative subjective responses to the different care systems by the patients is important in determining which system to recommend.

Eight adapted rigid lens-wearing patients were fitted with three different lens polymers: 1) Boston IV; 2) Equalens, and 3) Airlens. All the lenses were fitted in the same manner and with the same overall diameters.

The following four care systems were used:

Soaking Cleaner Preservative

1. Boston Boston Chlorhexidine Conditioner Cleaner

2. Allergan LC-65 Benzalkonium Wet-n-Soak chloride

3. Alcon Preflex Thimerosal Soaclens

4. Alcon Opti-Soft Polyquad Opti-Soft Cleaner

Each patient wore a given lens material (both eyes the same) for daily wear for 1 week with one of the four care systems being used on one lens and a second care system on the other lens. After 1 week, the lenses were removed and cleaned as explained below. A different care system and lens material was then used for the following week. Because of the number of lenses and systems, each patient did not use all the system- lens combinations. Each patient used six of the 12 combinations in a random sequence. Neither the patient nor the examiner knew which care system was being used.

The solutions were used in the following pairs: 1) Boston and Wet-N-Soak; 2) Boston and Opti-Soft; 3) Wet-N-Soak and Soaclens; and 4) Soaclens and Opti- soft.

Each lens was cleaned thoroughly on receipt from the laboratory with Sil-O&are polish by rubbing between the fingers. They were then rinsed and cleaned

J Volume 16, Numbers 11 & 12 November/December 1989 333

again thoroughly with unpreserved saline. They were next very well cleaned with the cleaner of the system to be used. This was followed by a soak for 14 days (changing the solution after 7 days and 24 hr prior to dispensing) in the appropriate soaking solution for the system to be used.

Each bottle the patients used was marked right and left as well as was the lens case so the patient would not mix up the systems. They removed the lenses in the evening, cleaned them with the cleaner, then rinsed and placed them in the case with new soaking solution for overnight soaking. The lens was removed the next morning from the case and placed on the cornea. No rewetting drops or any other solutions were used.

The patients were examined 30 min after lens placement, after 6 hr of wear on the first day, and after 6 hr of lens wear on day 7.

At each visit (30 min, 6 hr, 7 days), the visual acuity and B.U.T. on the lens surface was measured. The lens surface debris was graded on the eye with the biomicroscope using a scale of 0 (clean) to 3 (heavy coating), and the amount of peripheral cornea1 staining was also graded on a 0 (none) to 3 (dense, coalesced) scale. At the 1 week visit, the same measurements were made as above plus the patient was ask to fill out a questionnaire (Figure 1) concerning the comfort of the lenses and lens care system preference. Fisher’s least significant difference test was used to determine if there were differences between the different systems and lens materials.

RESULTS

Figure 1 shows the average B.U.T. on the lens surface for each solution. The values are the means for all B.U.T. measurements from all the visits on all the lenses with the indicated solution. Even though there are minor differences in the average values, statistically there was no difference between the different solutions.

Figure 2 shows the mean B.U.T. by the care system for each of the lens materials. There were no significant differences between the systems on any of the lenses. However, if the B.U.T.s for the different polymers are compared (Figure 3), there was a significant difference between the Airlens and the other two lenses. There was no difference between the Boston IV and the Equalens.

Figure 4 shows the mean values for the surface debris grading at all the visits on all the lenses with the indicated solutions. Again, no statistical difference was found between the different systems. Figure 5 shows the surface debris grading for each solution by lens type. No statistical difference was found between the care systems for any lens type. Figure 6 shows the surface debris grading for each lens type-a composite of all lens solutions. In this case, the grading on the Airlens was significantly higher than it was on the other lenses.

Figure 7 shows the amount of peripheral cornea1 staining with the different solutions for all the visits with all the lenses. The eyes where Soaclens was used on the lenses showed significantly less staining than did

B.U.T. ON LENS SURFACE BY SOLUTION FOR ALL LENSES

S.U.T. (set)

n

BOSTON SOACLENS WET-N-SOAK

CARE SYSTEM

Figure 1. The B.U.T. on the front of the lens based on the solution system being used. This is the mean of the measurements on all the lens materials while the indicated solution was being used.

B.U.T. ON LENS SURFACE BY SOLUTION FOR EACH LENS

B.U.T. (SIX)

12

10

8

6

4

2

0 BOSTON SOACLENS WET-N-SOAK OPTI-SOFT

CARE SYSTEM

- AIRLENS BOSTON IV 0 EQUALENS

Figure 2. The mean B.U.T. on the front of the lens for each lens material and with each solution.

B.U.T. BY LENS TYPE ALL SOLUTION VALUES COMBINED

S.U.T. (seconds)

/ J

EQUALENS BOSTON IV AIRLENS

LENS MATERIAL

t

Figure 3. The mean B.U.T. on the front of the lens for each lens material combining the results of all care systems.

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SURFACE DEBRIS GRADING BY SOLUTION FOR ALL LENSES

SURFACE DEBRIS (graded O-3)

0.8

BOSTON WET-N-SOAK OPTI-SOFT

CARE SYSTEM

Figure 4. Surface debris grading on a scale of O-3 by care system combining results for all lens materials.

SURFACE DEBRIS GRADING BY SOLUTION FOR EACH LENS

SURFACE GRADING (O-3)

/1 1

1.2 1

0.6 0.6 0.4 0.2

0 BOSTON SOACLENS WET-N-SOAK OPTI-SOFT

CARE SYSTEM

- EQUALENS m BOSTON IV 0 AIRLENS

Figure 5. Surface debris grading on a scale of O-3 by care system for each lens material.

SURFACE DEBRIS GRADING ALL SOLUTION VALUES COMBINED

0.6

SURFACE GRADING (O-3) rmpp

EQUALENS BOSTON IV AIRLENS

LENS MATERIAL

Figure 6. Surface debris grading on a scale of O-3 by lens material combining all care systems.

eyes that used the other systems. Figure 8 shows the peripheral staining by lens type for the different solutions. Statistically, with the Boston IV material, the eyes on which the Soaclens were used had significantly less staining than did eyes that used the Boston solutions. With the Equalens (Figure 8) the Boston solutions showed less peripheral staining than did the Wet-N- Soak. With the Airlens, the Soaclens shows significantly less staining than did the Opti-Soft solution. Fig- ure 9 shows the peripheral staining by lens type for all solutions. The Equalens caused significantly less peripheral staining than did the other two lens materials.

With respect to the patients’ responses to the ques- tions on the questionnaire, some definite preferences were found. The results are given as the percentage of patients who used the pair of solutions indicated, one solution on one eye and the other on the opposite eye. The composite results from all lens types are given.

The response to question, “01 initial /ens placement in the morning was either/ens more comfortable?“, was as follows:

(Oh preferring listed solution) BOSTON vs. WET-N-SOAK

27%-BOSTON 9%-WET-N-SOAK

64%-NO DIFFERENCE (n = 11)

BOSTON vs. OPTI-SOFT 55%-BOSTON O%-OPTI-SOFT


WET-N-SOAK vs. SOACLENS 27%-WET-N-SOAK 27%-SOACLENS 45%-NO DIFFERENCE

(n = 11) SOACLENS vs. OPTI-SOFT 25%-SOACLENS 0%-OPTI-SOFT


The response to question 4, “On initial /ens placement in the morning was vision with either lens better?, ” was as follows:

(% preferring listed solution) BOSTON vs. WET-N-SOAK



BOSTON vs. OPTI-SOFT 55%-BOSTON

0%-OPTI-SOFT 45%-NO DIFFERENCE

(n = 11) WET-N-SOAK vs. SOACLENS

18%-WET-N-SOAK 27%-SOACLENS 1

Volume 16, Numbers 11 & 12 November/December 1989 335

PERIPHERAL CORNEAL STAINING BY SOLUTION FOR ALL LENSES

PERIPHERAL CORNEAL STAINING (O-3) /I I

t 7

BOSTON SOACLENS WET-N-SOAK OPTI-SOFT

CARE SYSTEM

Figure 7. Peripheral cornea1 staining by type of care system combining all lens material results.

PERIPHERAL CORNEAL STAINING BY SOLUTION FOR EACH LENS

PERIPHERAL CORNEAL STAINING (O-3) 1

0.6

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

BOSTON SOACLENS WET-N-SOAK

CARE SYSTEM OPTI-SOFT

- EQUALENS BOSTON IV 0 AIRLENS

PERIPHERAL CORNEAL STAINING ALL SOLUTION VALUES COMBINED

PERIPHERAL CORNEAL STAINING (O-3)

4

EOUALENS BOSTON IV AIRLENS

LENS MATERIAL

Figure 9. Peripheral comeal staining by lens material combining results from all care systems.


SOACLENS vs. OPTI-SOFT 27%-SOACLENS

0%-OPTI-SOFT 73%-NO DIFFERENCE

(n = 11)

The response to question 6, “Did one lens have to be removed and cleaned during the day more often than the other?“, was as follows:

(% indicating which lens needed cleaning more often) BOSTON vs. WET-N-SOAK

0%-BOSTON 36%-WET-N-SOAK 64%-NO DIFFERENCE

(n = 11) BOSTON vs. OPTI-SOFT

0%-BOSTON 55%-OPTI-SOFT 45%-NO DIFFERENCE

(n = 11) WET-N-SOAK vs. SOACLENS

9%-WET-N-SOAK 27%-SOACLENS 64%-NO DIFFERENCE

(n = 11) SOACLENS vs. OPTI-SOFT

8%-SOACLENS 42%-OPTI-SOFT 50%-NO DIFFERENCE

(n = 12)

The response to question 7, “If you had to use two identical care systems would you want the one you used on the right or leff lens?“, was as follows:

(% preferring listed solution) BOSTON vs. WET-N-SOAK



BOSTON vs. OPTI-SOFT 73%-BOSTON 9%-OPTI-SOFT


WET-N-SOAK vs. SOACLENS 27%-WET-N-SOAK 45%-SOACLENS 27%-NO DIFFERENCE

(n = 11) SOACLENS vs. OPTI-SOFT

58%-SOACLENS 8%-OPTI-SOFT

33%-NO DIFFERENCE (N = 12)

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B.U.T. ON LENS SURFACE FOR EACH PATIENT

S.U.T. (set)

12

’ 9.89

8

6

2 3 4 5

PATIENT

7.18

I

6

5.12

I 7

3.5

I

8

Figure 10. B.U.T. on lens surface for each patient. Results from all Figure 11. Surface debris grading for each patient. Results from all care systems and lens materials. care systems and lens materials.

DISCUSSION Statistically, there were no differences between the

care systems with respect to lens surface B.U.T. or the amount of surface debris. However, there were differences between materials with the Boston IV and Equal- enses being essentially the same with the Airlens showing a significantly shorter B.U.T. and more surface debris. Likewise, there was a significant difference in the average B.U.T. and surface debris grading between some patients as shown in Figures 10 and 11. For B.U.T., patient l’s time was significantly less than the times of patients 5-8. Likewise, patients 7 and 8’s times were different from those of patients 1-5. For the surface debris, patient l’s value was statistically different from all the others except for patients 6 and 8’s values, whose were significantly greater than all the other patients. Therefore, the differences between patients and materials seem to be greater than those between solution systems for these measurements. There were some differences between patients with respect to peripheral staining, but not as many or as great as with the other two measurements.

With respect to subjective preference when two systems were used on opposite eyes at the same time, many patients indicated differences. Overall, the Bos- ton care system was preferred most often with little overall difference between the Wet-N-Soak and Soa-

1.4 ,

1.2-

1

SURFACE DEBRIS GRADING FOR EACH PATIENT

SURFACE DEBRIS GRADING (O-3) -m-

0.8

0.8

0.4

0.2

0

0.24

~ 1 2 3 4 5 6 7 8

PATIENT

clens. The Opti-Soft system, which is not formulated for or recommended for rigid lenses, was the least preferred. This is most likely because of the low viscosity of the solution. The system was tested in this study to determine if a lower viscosity solution would improve the problem of surface debris build-up, which obviously it did not.

The results of this study should not be interpreted as meaning that the Boston care system should be used on all patients or to the exclusion of other systems. Obviously, many patients could not tell a difference between systems and some preferred other systems.

Acknowledgment

We would like to thank Art Optical, Grand Rapids, Michigan, for providing the Boston IV and Equalenses.

References

1. Rosenthal, P., et al. Quantitative analysis of chlorhexidine glu- conate and benzalkonium chloride adsorption on silicone/acrylate polymers. CLAO J. 12(1):43-50, 1986.

2. Meakin, B., Gee, H. Interaction of benzalkonium chloride with Boston contact lens material, Br, Contact Lens Assoc. J. 6(2):42- 50, 1983.

3. Benjamin, W., et al. Contact angle update: Care regimens. KXC 11(8):501-506, 1984.


About the Authors

John J. Pole, 00, MSc, received his OD degree from Ohio State University in 1975. He also com- pleted the combined MSc-contact lens residency program at the same institution in 1979. Dr. Pole is currently an associate professor of optometry at Ferris State University, after spending several years in private practice in Columbus, Ohio.

Mary L. Biolo received her AAS degree in optometric technology and BS degree in applied bi- ology from Ferris State University. She has been a full-time optometric research technician, coor- dinating the clinical research studies in the Con- tact Lens Research Clinic at the College of Optometry, Ferris State University for the past 5 years.

Gerald E. Lowther, 00, PhD, received his de- grees from The Ohio State University where he was an associate professor before becoming professor of optometry at Ferris State University. He is presently professor of optometry at the School of Optometry, University of Alabama at Birmingham.

Clinical Implications The study indicates that subjective responses to gas permeable lenses are more a function of lens materials and individual patient’s differences than of the care system used.

There are more consistent results from a given material used with various solution systems than from the results of given solution systems with various materials. In order to service our patients, we must be aware of these differences and remember that there is no one best solution system for all gas permeable lenses.

In review of the disagreement as to which solutions work best on a specific gas permeable material, all of the opinions may be partially correct.

Jack J. Yager, OD 214 E. Park Street Orlando, FL 32803

5x5 ICLl C

Manufacturer’s Comments It is difficult to draw conclusions from a study with a sample size too small to give meaningful statistical power, particularly when there apparently is significant variability within the study population and little difference among the test products. The statistical power is further reduced when all cells of a crossover study are not filled. A multiple crossover design also complicates the task of the subject in making subjective choices.

A further complication, not inherent in the study design but rather the effect of progress, is that the Wet-N-Soak@ product regimen has subsequently been improved with the introduction of Wet-N-Soak@ PLUS Wetting and Soaking Solution and Resolve/GP@ Daily Cleaner. In Allergan’s clinical and marketing evaluations it was noted that the subjective response to Wet-N-Soak 0 Wetting and Soaking Solution was enhanced by increasing the viscosity while simultaneously increasing the concentration of lens surface wetting agent. In addition, it was noted that the preservative concentration could be lowered in this new formulation which is now marketed as Wet-N-Soak@ PLUS Wetting and Soaking Solution. It has also been noted that a more efficacious daily cleaner, Resolve/GPO, enhances lens wettability and hence should reduce the required frequency of removal for cleaning during the lens wearing period.

I would echo the position of the authors that this paper’s results should not be used to decide if one lens care system should be used to the exclusion of others. Differences in contact lens care systems, just as differences inherent in the available contact lens materials, offer opportunities to prescribe for the differences in patients. Each practitioner will probably establish a care system of choice, but that generally will be based upon more experience than the perception of eight patients.

Richard C. Courtney, OD Senior Director

Contact Lens Clinical Research Ailergan Optical

Irvine, CA 92715-l 599


comparison of care systems on rigid gas permeable lenses

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