Roughly three million people over the age of 50 in the United States wear contact lenses.1 This is also the age when routine medication use becomes a way of life for many patients. So, how do systemic and topical drugs alter the ocular surface environment and the contact lens wearing experience?
Interestingly, soft contact lenses are being investigated as a vehicle for topical delivery of certain drugs, including fluoroquinolones, cromolyn sodium, ketotifen, ketorolac, cyclosporine, dexamethasone, epidermal growth factor, timolol and natamycin.4-7
In one study evaluating the use of extended antibiotic-releasing lenses to treat ocular infections, researchers injected a methicillin-resistant strain of Staphylococcus aureus into the anterior chamber of rabbits to model bacterial endophthalmitis.7 Treatment with a topical fluoroquinolone reduced the bacterial load from 100,000 in the untreated group to 10,000; in comparison, immediate treatment with experimental gatifloxacin-releasing lenses prevented growth of microorganisms, thus providing an effective potential treatment of perioperative or trauma-related infection.7
Silicone hydrogel lenses are known to interact stronger with lipids but weaker with proteins compared with conventional hydrogel lenses.3,4 Within this lens class, however, there are differences in the absorption and release rates of biocidal compounds.3
Lens characteristics that affect drug absorption of a given molecular compound include water content, pore size, hydrophobicity and ionic charge.2 For example, hypertonic solutions such as sodium sulfacetamide 10% or pilocarpine 8% can cause loss of lens water content and alteration of the lens curvature.3 Application of topical medications with an acidic pH can lead to lens dehydration and steepening, while use of alkaline medications can cause hydration and flattening.3 Topical suspensions may also cause lens intolerance due to a particulate aggregation; this has been observed with drugs containing salicylates, which are secreted into the tear film and can cause ocular irritation.3
|Table 1. Chemicals That Cause Color Changes in Hydrogel and Silicone Lenses|
|Yellow||Phenolphthalein (found in some laxatives)|
|Brown||Sulfasalazine (for inflammatory bowel disease)|
|Grayish-Brown||Topical epinephrine and phenyephrine|
Phenazopyridine (for urinary tract infections)
Rifampin (for tuberculosis and meningcoccal disease)
Ascorbic acid (i.e., vitamin C)
|Pink|| Hydrogen peroxide (pharmacy grade)|
|Green||Beta-blockers (systemic; long-term use)|
When evaluating a soft contact lens wearer undergoing treatment for an ocular or systemic condition, take a careful history first, and pay particular attention to irritative symptoms as they relate not only to lens maintenance and care, but also to medications. Do the symptoms improve or become compounded by the removal of the lenses? This may suggest lens absorption and/or release of various agents.
Next, perform an examination with the lenses in place and look for evidence of steepening or flattening. Consider your findings in the context of the patient’s medication profile and use this data to coordinate treatment regimens with the patient’s other—if any—health care providers.
Give special consideration to lens material type and replacement schedule when patients are using concomitant medications. For patients who wear soft contact lenses, daily disposable lenses may be the best option, rather than trying to purge drugs by soaking lenses overnight in a contact lens solution. Gas permeable lenses typically will not have the same absorptive rate as hydrogel and silicone lenses. Keep in mind, however, that each material is different, so the adsorption of drugs cannot always be predicted.
1. Swanson M. A Cross-Sectional Analysis of U.S. Contact Lens User Demographics. Optom Vis Sci. 2012 Jun;89(6):839-48
2. Jones L, Powell CH. Uptake and release phenomena in contact lens care by silicone hydrogel lenses. Eye Contact Lens. 2013 Jan;39(1):29-36.
3. Croker C. Contact Lens Interaction with Pharmaceutical Products and Cosmetics. www.eyesite.co.za/magazine/december2004/columns1.asp?mainbutton=columns&navbutton=columns1 Accessed Apr. 8, 2015.
4. Nichols J. Contact Lenses 2014. Contact Lens Spectrum. 2015 Jan;30(1):22-27.
5. Hui A, Willcox M, Jones L. In vitro and in vivo evaluation of novel ciprofloxacin-releasing silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci. 2014 Jul 15;55(8):4896-904.
6. Peng CC, Chauhan A. Extended cyclosporine delivery by silicone-hydrogel contact lenses. J Control Release. 2011 Sep 25;154(3):267-74.
7. Kakisu K, Matsunaga T, Kobayakawa S. Development and efficacy of a drug-releasing soft contact lens. Invest Ophthalmol Vis Sci. 2013;54:2551–61.