Evaluation of “Bacteriostatic” Contact Lenses*

866

J. M. WESBERRY, R. HIATT, A. R. DEUTSCH AND P. M. LEWIS

5. Drance, S. M. : Studies with applanation water test, Arch. Ophth., 69 :39, 1963. 6. Jackson, H. R. : Cited by Ball : Modern Ophthalmology. Philadelphia, Davis, 1926, ed. S, 1012. 7. Becker, B. : Tonometry, tonography and pro­ vocative tests in the management of the glauco­ mas. Tr. Am. Acad. Ophth. Otolaryng., 64:127, 1960. 8. Sugar, H. P. : Provocative tests in the glau­ comas. Am. J. Ophth., 31:1193, 1948. 9. Roberts, W. : Correspondence. Am. J. Ophth., 59:335. 1965. 10. Smith, J. L. : Applanation vs. Schätz to­ nometry. Am.'.T. Ophth., 58:807, 1964. 11. Correspondence. Am. J. Ophth., 59: 335, 1965. 12. Posner, A. : A new portable applanation to­ nometer. EENT Monthly, 43 :88, 1964. 13. Galin, M. A., Aizawa, F., and McLean, J.

M : Hemodilution and intraocular pressure. Arch. Ophth., 73:25, 1965. 14. Lawrence, C, and Wolff, S. M. : Tonographic water-drinking test in early diagnosis of glauco­ ma. J. Ophth. Soc, 31:15, 1962. 15. Harrington, D. O., and Flocks, M. : The multiple-pattern method of visual field examina­ tion. Arch. Ophth., 61:755, 1959. 16. Sloan, L. L. : An explanation for the poor performance of aphakic patients on the Harring­ ton-Flocks screening test. Am. J. Ophth., 41:987, 1956. 17. Miller, D. : The relationship between di­ urnal tension variation and the water-drinking test. Am. J. Ophth., 58:243, 1964. 18. Becker, B., and Friedenwald, J. S. : Clinical aqueous outflow. Arch. Ophth., 50:557, 1953. 19. Becker, B. : Tonography in the diagnosis of simple (open-angle) glaucoma. Tr. Am. Acad. Ophth. Otolaryng., 65:157, 1961.

EVALUATION OF "BACTERIOSTATIC" CONTACT LENSES* A DOUBLE-BLIND STUDY T H O M A S C H A L K L E Y , M.D.,

LEONARD S A R N A T , M.D.,

AND DAVID S H O C H ,

M.D.

Chicago, Illinois All normal eyes harbor bacteria, 1 yet the incidence of bacterial conjunctivitis is rela­ tively small, even though many of these bac­ teria are known pathogens. T h e wearing of contact lenses does not of itself change the bacterial flora of the eye 2 and, except for unusual circumstances of wear 3 or injury, 4 does not seem to predispose the eye to infec­ tion. Perhaps the major source of contami­ nation of lenses is the containers in which they are stored and, at this time, there seems to be about equal evidence for the su­ periority of wet 5 ' 6 and dry 7 storage. In an attempt to protect the eye further against contaminated contact lenses, one of the major contact lens fabricators has incor­ porated germicidal agents into the plastic used in the manufacture of such lenses.t It * From the Department of Ophthalmology, Northwestern University Medical School. t Wesley-Jessen Co., Chicago, supplied all the lenses used in this study and supported a bacteri­ ology laboratory for the evaluation of their prod­ uct.

is their contention that these agents are nonirritating to the eye and that they can re­ duce the incidence of infection in contact lens wearers. T o this end they prepared a material they term "Aseptoplast," which consists of polymerized methyl methacrylate into which have been incorporated two bacteriostatic agents : hexachlorophene ( 3 . 0 % by weight) and a commercial mixture, Corobex CP-4* ( 1 . 0 % by weight). T h e manu­ facturer states that these specially prepared lenses are bacteriostatic for at least three months of wear. T h e present study was undertaken in two stages. I n the first phase patient tolerance to the lenses was determined, and in the sect Corobex CP-4 is manufactured by the Royce Chemical Company of East Rutherford, New Jer­ sey. They list the contents as follows : active in­ gredients : phenylmercuric borate (2.25%), 2ethyl hexanol (0.11%), and benzethonium chloride (0.75%); inactive ingredients: Carbitol (49.09%), diethyl phthalate (47.24%), and Aerosol OTB (0.22%).

BACTERIOSTATIC CONTACT LENSES ond the effect of these lenses on the flora of the conjunctival sac was studied. PROCEDURE

Phase 1. Tolerance studies. Sixty-five pa­ tients were fitted with corneal lenses sup­ plied by the manufacturer. In most cases one lens was a standard contact lens and the second was an experimental "Aseptoplast" lens. The allocation of the lenses was on a random basis, unknown both to the patient and to the physician in charge of the pro­ gram. The code was held by the manufac­ turer and supplied only at the end of the ex­ periment. When the code was provided, it was apparent that the manufacturer had oc­ casionally supplied standard lenses for bothi eyes to randomize the experiment further. The patients were largely young myopic; student nurses who wanted lenses forr cosmetic purposes and were well motivated1 to wear them. A few of the patients were; aphakic and were followed in the out-patientt clinic. Each patient was seen at weekly intervals,, and subjective and objective findings re­ corded. After six months of observation, the data were tabulated for the experimental1 and control lenses. Phase 2. Bactériologie studies. In this5 phase of the investigation, a second series5 of patients was fitted with contact lenses ini exactly the same manner as already noted. Again, in most cases, one eye was fitted1 with an experimental "Aseptoplast" lenss and the second with a standard plastic lens. The identity of each lens was unknown bothi to the patient and to the observer. Cultures were made of conjunctival secre­ tions before and at varying intervals afterr fitting the lenses. This was done by swab­bing the inferior cul-de-sac with a sterilee moistened applicator, which was incubatedI in broth and plated out on blood and choco­ late agar. The patients were seen at weeklyer intervals, and, at the end of three months,;, the code was broken and the data were cor­ related with the experimental findings.

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TABLE 1 TOLERANCE STUDIES ON "BACTERIOSTATIC" LENSES

Total number of patients Number lost to follow-up Number in study Without complaints or pathologic findings With complaints or pathologic findings With similar bilateral complaints or findings With unilateral complaints or findings Referable to experimental lenses Referable to control lenses

65 9 56 32 24 19 5 2 3

In all, 204 eyes were cultured, 108 before insertion of the lenses and 96 at intervals after the lenses were dispensed. RESULTS

Phase 1. Tolerance studies. Of the 65 patients originally fitted with lenses, nine were lost to follow-up. This study is based on a group of 56 patients who wore their lenses regularly. Of these 56 patients, 31 wore both lenses successfully without complaints or ocular findings. In 24 patients there were subjective complaints and objective findings of irritation in one or both eyes (table 1). It should be noted that in the group of 19 patients with complaints or findings involv­ ing both eyes most wore one experimental lens and one control lens. In a few cases both eyes were fitted with either control or experimental lenses. In these cases the observer believed that the problems were due to improper fitting or improper use of the lenses by the patient. In no case was there any permanent damage to the cornea. In the five patients with complaints or findings in­ volving only one eye, there was about an equal incidence with the control lenses and with the experimental lenses. Phase 2. Bactériologie studies. To establish the bactériologie characteristics of our experimental population, consisting largely of young student nurses without history or evidence of previous eye disease, 108 con­ junctival sacs were cultured prior to wear­ ing contact lenses. Almost all showed bacteriologic growth (table 2, columns 1 and 2 ) , confirming the reports of others on normal populations.1'8

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THOMAS CHALKLEY, LEONARD SARNAT AND DAVID SHOCH TABLE 2 FLORA OF CONJUNCTIVAL SACS BEFORE AND AFTER WEARING CONTACT LENSES

Organism Sterile Staphylococci Diphtheroids Streptococci Pneumococci Gram-negative cocci Gram-positive rods Gram-negative rods Proteus Spirochetes

Experimental Control , Control , Eyes (108) 'Bacteriostatic' Lens (49) Lens (47) 8 80 15 2 5

2 43 7 0 2

1 36 7 0 3

4

1

0

7

3

7

3 3 2

7 0 0

1 1 0

A total of 96 cultures were made on con­ tact lens wearers (columns 3 and 4 of table 2 ) . T h e number of positive cultures exceeds the number of eyes, since many of the con­ junctival sacs harbored more than one orga­ nism. There were three sterile conjunctival sacs. In no case, did an eye that harbored organisms before the wearing of contact lenses become sterile after insertion of ei­ ther the experimental lenses or the control lenses. There were no cases of conjunctivitis in patients wearing either the conventional or the experimental lenses. Minor abrasions and stippling were noted in wearers of both types of lenses. These responded quickly to treatment, and no serious injury or corneal damage resulted in any patient. DISCUSSION

Conjunctivitis due to the wearing of con­ tact lenses is rather uncommon. However, abrasions are not uncommon and, in the presence of pathogenic organisms, serious corneal injury may result. It has been postu­ lated that the incorporation of germicidal agents into contact lenses would reduce the incidence of such infections. I t is the con­ tention of the manufacturer of these lenses that a true solution of the germicide in the plastic is achieved, and they state : After three months' continuous leaching, the plastic does not decrease in its antimicrobial activity

. . . a small amount of germicide would find its way into the tears, which would account for the anti­ microbial activity of the plastic. This statement is open to question. H e x a chlorophene is very insoluble in water, and it is unlikely that any significant amounts would preferentially dissolve in tears. T h e active ingredients of Corobex C P - 4 (see footnote under "procedure") are quite water-soluble, however, and it seems likely that these substances would be quickly dis­ solved out in the storage solutions of the lenses or in the tears. This objection is somewhat supported by our findings. In no case was there an altera­ tion in the bacterial flora of the eye after wearing the "germicidal" lenses. It is true that there were no cases of conjunctivitis in the wearers of these lenses, but neither were there any infections in the wearers of stan­ dard plastic lenses. This complete absence of infection was due more likely to the care­ ful supervision of the patients than to any inherent antimicrobial activity of either type of lens. Neither the control lenses nor the experimental lenses demonstrated any inher­ ent properties irritative to the eye. CONCLUSIONS

1. Double-blind bactériologie studies, be­ fore and after the wearing of so-called ger­ micidal contact lenses, failed to reveal any in vivo bactericidal activity of these lenses. 2. Neither the usual methyl methacrylate lenses nor the experimental lenses significantly altered the conjunctival flora of the wearers. 3. W e a r i n g of contact lenses of either type did not predispose the patients to con­ junctivitis, although occasional staining and abrasions of the cornea were seen with both types of lenses. 4. T h e germicide-impregnated lenses were no more irritating to the eye than ordinary contact lenses. 303 East Chicago Avenue

(60611).

BACTERIOSTATIC CONTACT LENSES REFERENCES

1. Cason, L., and Winkler, C. : Bacteriology of the eye: I. Normal flora. Arch. Ophth., 51:196, 1954. 2. Winkler, C, and Dixon, J. : Bacteriology of the eye: III. Effect of contact lenses on the nor­ mal flora. Arch. Ophth., 72:817, 1964. 3. Payrau, P., and Perdriel, G. : Bilateral hypopyon ulcer of the cornea following continuous wearing of contact lenses. Bull. Soc. Ophtal. France, 9 :852, 1956.

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4. Fitzgerald, J., Kapustiak, W., and McCarthy, J. : Contact lens corneal ulcer. Am. J. Ophth., 54:307, 1962. 5. Bettman, J. W. : Contact lens storage, wet or dry? Am. J. Ophth, 56:77, 1963. 6. Dabezies, O. H. : Wet vs. dry storage of cor­ neal contact lenses. Amer. J. Ophth, 59 :684, 1965. 7. Allen, H. F. : To wet or not to wet. Arch. Ophth, 67:119, 1962. 8. Smith, C. H. : Bacteriology of the healthy conjunctiva. Brit. J. Ophth, 38 :719, 1954.

T H E SURGICAL T R E A T M E N T O F I N T E R M I T T E N T EXOTROPIA* WARREN W.

BINION,

M.D.

Fort Worth, Texas

The patients considered in this study originally had exodeviations which at times were latent and at other times were mani­ fest. Primary (divergence excess), conver­ gence insufficiency, and combined types are included in this series. With the passage of time, patients may change from one of these categories to another, hence the inclusion of all three types of this intermittent deviation. A.

BASIC PHYSIOLOGY

Because there is such a diversity of opin­ ion as to the treatment of intermittent exotropia, it is not surprising that a controver­ sy exists in explaining the basic physiology of this condition. Adler1'2 emphasized that divergence is an active process. He found an increased burst of impulses above the resting level from the lateral rectus electrode preceding the move­ ment of this muscle from the convergent to the straight-ahead position. Breinin3 found that lateral rectus innerva­ tion was increased and medial rectus inner­ vation inhibited in the deviating eye at the time fusion was disrupted and exotropia oc­ curred. Breinin, using data from monocular electromyograms, emphasized that active di­ vergence was responsible for the occurrence * Presented before the Texas Society of Ophthal­ mology and Otolaryngology, San Antonio, Texas, December, 1965 (candidate thesis).

of exotropia and placed little importance on the diminished medial rectus activity. There is no controversy with respect to exophoria. It is generally believed that con­ vergence supplies the fusion innervation necessary to keep the deviation latent. From this, Jampolsky4-7 concluded that it was log­ ical to implicate a diminution in convergence as a causative factor in the development of intermittent exotropia. He measured both eyes simultaneously and found a decrease in the medial rectus firing in each eye at the time exotropia became manifest. There was also a decrease in the firing of the lateral rectus muscle of the fixing eye while the lat­ eral rectus of the deviating eye received in­ creased innervation. Both lateral rectus muscles should have demonstrated increased motor activity, he stated, if one supports ac­ tive divergence as the explanation for the break in fusion. He tested both eyes simul­ taneously with binocular electromyograms. B.

CLINICAL CLASSIFICATION

Whether a divergent deviation remains a phoria or progresses through intermittent ex­ otropia to constant exotropia depends upon the fusion ability to overcome the deviation entirely, partially or not at all. The near deviations are thought to be due to an insufficiency of convergence.8'10'12 Cases may be classified as: (1) primary