Lecture 4 Soft Lens Solutions & Care Systems PDF

Lecture 4 So Lens Solutions & Care Systems Review Questions 1. Which statement about soft lens diameter is INCORRECT? a. It is ideally 0.2 to 0.4mm larger than HVID - Want diameter to drape at least 1mm past the HVID b. It allows for stability, comfort, & full...

Lecture 4 So Lens Solutions & Care Systems Review Questions 1. Which statement about soft lens diameter is INCORRECT? a. It is ideally 0.2 to 0.4mm larger than HVID - Want diameter to drape at least 1mm past the HVID b. It allows for stability, comfort, & full corneal coverage with movement c. Most commercial soft lenses have limited diameter options d. Larger diameter lenses have more sagittal depth than smaller diameter lenses 2. Which of the following about soft lens replacement & wear schedule is INCORRECT? a. Soft contact lenses can be replaced daily, every 2 weeks, 1 month, 3 months or 1 year b. 6 month replacement lenses are called conventional contact lenses c. Daily disposable lenses usually cost most d. Extended wear lenses can be worn up to 30 days in a row 3. Which of the following would NOT be part of a soft contact lens fitting assessment? a. Coverage of lens on the cornea b. Centration of the lens on the corena c. Stability of the lens d. Movement of the lens e. Patient comfort f. All of the above are assessed in a soft contact lens fitting Fitting Contact Lenses: Contact Lens Replacement Schedule Lenses may be replaced on a variety of schedules → determined by the FDA at the time the lens is approved for market Each lens can only be approved for ONE interval Most common interval for soft lenses is: ○ DAILY>MONTLY>BIWEEKLY>CONVENTIONAL Nowadays, only specially designed lenses account for lenses that are replaced every 3 to 6 months All gas permeable & hybrid lenses are specially designed finite ioninso for Soft Lens Replacement Schedule aaiyiiii.ie in Daily lenses do not require any maintenace or storage Biweekly replacement soft lenses do require care systems to maintain & store lenses between use 1  Monthly replacement soft lenses also require care systems to maintain & store lenses between use ○ Most monthly replacement lenses come in a “family” with spherical, astigmatism, & presbyopic/multifocal lenses **Nearly 70% of soft contact lenses prescribed will ned care systems for cleaning & maintenance monthyreplacement designs the widestrangeofpoweravailabilityis usually in Importance of Contact Lens Care Systems Lens care systems and solutions are products you use to clean, disinfect and store your contact lenses Important for keeping your eyes healthy and free from infection (CDC) 1. Disinfection → keeps patients safe 2. Cleaning → protein & lipid removal 3. Improves wettability 4. Improves patient comfort & reduce drop out 5. Ensure full day wear 6. Recognize careless attitude 7. Prevent infection & vision loss Product Properties An ideal contact lens solution … 1. Effective disinfection against wide variety of pathogens and microorganisms 2. No toxicity to the ocular tissues 3. Compatibility with contact lens materials 4. Simple to use 5. Lens surface conditioning – enhance wettability and lens comfort 6. Minimize deposition of tear film components 7. Inexpensive The Role of FDA Oversight FDA oversees the commercialization of all contact lens care products, including: ○ Solutions ○ Disinfection unit ○ Marketing claims ○ Labelling ○ Advertising Chemistry Product formulation: ○ pH, salinity, viscosity ○ Breakdown of chemical components ○ Sterility ○ Shelf life Interaction with contact lens materials ○ Affect lens parameters ○ Discolouration ○ Absorption 2  pH range of healthy tear film is ~ 7.3 to 7.7 Average osmolarity of tear films is 305 mOsm/kg ○ Buffers in CL solutions are used to maintain pH levels & osmolarity → plays a role in comfort ○ The GREATER the difference between values for solution & tear film = the GREATER the reaction by the ocular environment on lens insertion (stinging or irritation) Microbiology All CL solutions meet minimum FDA requirements for disinfection of Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Fusarium solani, and Candida albicans ○ These organisms are threats to CL wearers (harvested in worn CLs, used CL cases & infected eyes) Methicillin-resistant S. aureus (MRSA) and Acanthamoeba are additional organisms that are more difficult to kill ○ NOT currently part of FDA requirements for disinfection ○ CL solutions do have some levels of success against them Differing levels of disinfection by lens systems depends on: 1. Type of disinfectant 2. Total formation: chelators: buffers, etc Disinfection solutions: kill organisms by simply placing the lens in the solution Disinfection systems: require a regimen including cleaning & rinsing to kill sufficient organisms International Organization for Standardization (ISO) has an outlined criteria for assessing whether a preservative is effective → states that: ○ Starting bacteria in a test tube must have reduction by at least 3 log units (99.9%) ○ Reduction in fungi by at least 1 log unit (90%) ○ All while cells are soaking within manufacturer's recommended disinfection time (no rubbing or rinsing necessary) DISINFECTING SOLUTION → Meets all this criterion If solution cannot meet this criterion → can still be approved as DISINFECTION SYSTEM ○ After putting lens through recommended disinfection regimen with rubbing & rinsing, lens should not grow more than 10 colonies of microorganisms on lab plate 3  It is important to consider how effective each preservative is & how each may affect the ocular surface when used as directed by manufacturer Hypersensitivity reactions to preservatives must be considered when patient begins using a preserved product Knowing major preservatives will allow you to recommend products with different preservatives ○ Different preservatives – different chemical structures – less likely to evoke same hypersensitivity reaction TWO KINDS OF PRESERVATIVES: 1. Quaternary ammonium compound - Benzalkonium chloride (BAK) ⇒ MOST COMMON - Polyquaternium-1 (Polyquad ®) 2. Biguanides - Chlorhexidine gluconate - Polyaminopropyl biguanide (PAPB) Dynmed ® - Polyhexamethylene biguanide (PHMB) Tishchem ® - Alexidine dihydrochloride Others: ○ Thimerosal ○ Sorbic acid ○ Polyhexanide hypochlorite ○ Myristamidopropyl dimethylamine (Aldox) ○ Ethylene diamine tetraacetic acid (EDTA); used in combination with BAK ○ Benzyl alcohol When a CL is soaked in solution, interaction between the preservative & lens material can occur ○ Small preservative molecules (ie. Thimerosal) raise risk of being absorbed by CL Benzalkonium Chloride (BAK) Most commonly used preservative in eye care A quaternary ammonium compound Antifungal & antibacterial Bacteriocidal in combination with EDTA → causes corneal SPK, conjunctival hyperemia + edema ○ Excessive use of BAK → preserved artificial tears can be toxic BAK-based products can contaminate soft lenses with repeated use → found in some GP solutions, NOT used in soft lens solution DO NOT use BAK-preserved eye washes to soak or rinse soft lenses ○ **Recommend Non-preserved products whenever possible 4 Toxicity Interaction with living tissues: ○ Animals ○ In vitro ○ Human testing Clinical Clinical research trials use groups of real patients: Evaluation ○ At least 60 subjects for 3 months for new products ○ At least 30 subjects for 1 month for roughly equivalent products ○ Reference slide 31 on powerpoint Class III contact undergo more rigorous clinical testing compared to Class II Product Monographs → the most consistent & reliable source of information Product Categories Contact Lens Care Systems Multipurpose Solutions Clean, Store, Condition (Lubricate), Rinse Can be single or dual disinfection systems Soft lenses & GP lenses ADVANTAGES: Compatible with most lens types Convenience Longer storage times ○ Most allow storage for up to 30 days without replacing solution DISADVANTAGES: Patient hypersensitivity to preservatives Do not clean as well compared to a separate daily cleaner Long disinfection times; average 4-6 hour soak time “No Rub” solutions still have rinsing step that is often ignored Patients often “top off” solutions Oxidative Care / Clean & store (not for rinsing) Peroxide-Based Systems Soft lenses & GP lenses Known as red-cap solutions ⇒ DO NOT allow contact with the ocular surface Microfiltered 3% hydrogen peroxide (H2O2) ⇒ gold standard disinfectant ○ Broad range of antibacterial, antiviral, & antifungal activity 5  Compatible for use with most lenses → approved for use with both GP & soft CLs Requires a minimum soak time for complete neutralization: H2O2 → H2O + O2 ○ Neutralization accomplished in 1 of 2 ways: 1. Patient must be provided lenscase which contains a metallic disc 2. Oxysept (J&J) uses a tablet that is inserted with the lenses & changes colour Early removal of the lenses from the case may burn the cornea (corneal keratitis) → UNLIKE MPS care systems Newer products in this category are incorporating better cleaning & lubricating agents in order to compete with MPS products Patients should NOT use OTC 3% hydrogen peroxide (brown bottle peroxide) due to impurities that can damage or discolour soft lenses ADVANTAGES: Preservative-free Best antimicrobial action of all lens care solutions DISADVANTAGES: Cannot be used for rinsing Minimum soak time required – typically 6 hours must be allowed before removing lenses from case for use Multistep Solutions Two different steps → cleaner + conditioner ○ One solution cleans & disinfects → solution must be rinsed off from lens completely before application ○ Second solution → conditions the lens ONLY GP Lenses System works better for patients who have heavily deposits on their contact lenses or having difficulty keeping their lenses clean Generic Solutions Commonly older, non-premium versions of solutions Can vary by country Read the label → the chemistry tells you which brand name solution it is UCLA study → found that patients with a CL complication were 2x as likely to use generic/store brand solution instead of the leading MPS 6 Rewetting Drops Surfactant Cleaners Viscoelastics (Sodium Lubricants Hyaluronate) Remove or reduce Hyaluronate Rewetting agent to deposit formation (hyaluronic acid, HA) bind water to eye or Surfactant → is a water-retaining add moisture surrounds surface of polymer contaminant with charges (causes contaminants to repel each other & get flushed away) Protein Removal Enzymatic Cleaners Chemical Cleaners - Citrate Enzyme cut proteins into small Chelating buffer in Alcon solutions pieces Negatively charged Rinsing removes protein fragments Ionically binds to charged protein Dissolved in saline solution as a molecule & pulls them away from separate cleaning step or in lens surface disinfecting solution in a single step Avaliable in tablet or liquid forms: ○ Papain: derived from papaya ○ Pancreatin: derived from hog pancrease ○ Subtilisin: synthetic Factors Influencing Solution Selecting Things to consider for CL solution choice: 1. Soak time 2. Efficacy of disinfection 3. Comfort 4. Biocompatibility Selecting a Contact Lens Care System: Multipurpose Solution: ○ Ideal for non-compliant/adherent patients ○ Disposable lens wearers ○ Intermittent lens wears ○ Need to compare preservatives & other components Peroxide-based System: 7  ○ Patients with allergies ○ Heavy depositors ○ Conventional lens wearers ○ OK for GP lenses too ○ Patients at risk for viral infections ○ Preservative-free advantage Most patients purchase their contact lens solutions based on the recommendation of their eye care provider Solution Induced Corneal Staining (SICS) Diffuse SPK → chronic disruption to the epithelial cell layer “Preservative release” ⇒ when the contact lens is applied to the eye & staining is documented ○ Can occur as early as 2 hours & remain at various levels throughout lens wearing day NOT shown to lead to increased microbial keratitis ○ BUT increases a contact lens wearers’ chance of a corneal infiltrative event 3x (corneal infiltrate = WBC) INCREASED CL discomfort = INCREASED corneal staining DOES happen with certain solutions ○ PHMB found to bind 50x more than Polyquad-1(Polyquad is much bigger than PHMB) Patient Education, Patient Compliance/Adherence 1. Proper Lens Handling Lens Acquisition Purchasing lenses without a prescription Lens Wear Sleeping or napping in CLs Not replacing lenses as directed Ignoring a red eye while wearing lenses, commonly done without backup glasses Personal Hygiene, Lens Care & Handling Not washing hands thoroughly for lens handling Not rubbing and rinsing the lens before storage Topping off solution in the case Not using lens case Not replacing lens case at LEAST every 3 months Water exposure → showering, swimming, sauna Reasons for Non-Compliance/Adherence Lack of patient education → material compatability High cost of lenses Complicated care systems ○ Multiple steps 8  ○ Storage time Complications (bio-compatible) 2. Proper Lens Care “To rub or not to rub” Rub & rinse can help remove debris, deposits, & microorganisms from lens In 2010, FDA published an addendum (Contact Lens Care Product Labelling) ⇒ recommended that manufacturers of MPS products remove “no rub” directions from product leblling ○ Imphasis on importance of rubbing & rinsing ○ Private label products were NOT explicitly required to comply with this recommendations, thus accounting for presence of “no rub” labelling on some of these products Lens Case Care Cases should be rinsed regularly & replaced every 3 months Contamination of lens cases → may result in biofilm ○ Biofilm ⇒ aggregation of microorganisms to a surfacce or to one another marked by a glycocalyx extracellular matrix Makes organisms more resistant to disinfecting agents Visibly soiled lens case = guranteed lens contamination Commerical solution manufacturers ⇒ lens cases are thoroughly tested to ensure they DO NOT promote micorbial growth ○ Any lens care product you buy will come with an FDA approved case for use with that particular product Third party lens cases DO NOT undergo rigorous testing Strategies to Minimize Risk (Biofilm formation) BEST: ○ Mechanicl rub & rinse ○ Tissue wiping GOOD: ○ Soaking in solution for 6 hours ○ Air dry MINIMAL: ○ Rinsing cases with disinfecting solution or hot tap water 9  ○ Air dry LEAST: ○ Emptying & recapping after lens removal 3. Proper Lens Following as prescribed by doctor (FDA guidelines) Replacement Modified with follow-up findings Replace before significant problems develop, INCLUDING: ○ Discomfort / pain ○ Redness / discharge ○ Allergy ○ Blurry vision ○ Light sensitivity 4. Proper Follow-Up Following first encounter → have patient return before lens replacement, wearing the lenses, unless a problem arises with the lenses ○ Ie. 2-week replacement lens, follow-up with patient in 7-10 days Following prescribing CL Rx: ○ Schedule next appointment in 12 months ○ If seen before next appointment: Review compliance issues: Wear time → max 14-16 hours/day or as determined by doctor Lens cleaning & disinfection after each wear & before reuse Lens replacement as directed ○ Lens overwear can damage cornea Corneal neovascularization in daily CL wearers ⇒ suggestive of extended wear Contact lens care adherence (vs. complaince) should be the MAIN FOCUS ○ Open discussion with patient regarding their CL hygiene ○ Should be done at EVERY VISIT ○ Document on file ○ Educate patients on increased risk of microbial keratitis when using CL vs. spectacle correction **COMPLIANCE IS KEY ⇒ practitioners must educate patients on how to clean lenses, maintain, & replace their lens cases & how to follow expiration dates 10 Environmental Concerns with Contact Lenses Routhier et al, 2012 Study: ○ Annual supply of daily disposable lenses (365 pairs) produced 11.4g of plastic waste (=2 credit cards) VERSUS 20oz water bottle produces 28.5 g of plastic waste (=2.5 year supply of daily disposable lenses) ○ Standard lens case equivalent to a 4 year supply of dailies ○ Peroxide case equivalent to a 8+ year supply of dailies Plastic #5 are more commonly accepted by recycling programs B&L One by One CL Recycling Program: ○ One of the 1st companies to introduce CL recycling program ○ Accepts CL waste that DOES NOT consists of Plastic 5, contact lens blister packs, & their foil tops ○ All sorted at recycling plant ○ Available free of charge to those that want to participate Gimme 5 (plastic #5) recycling program → offers collection sites in major cities for plastic #5 waste ***AOA REMINDER ⇒ lenses SHOULD NEVER be flushed down the sink or toilet MAIN THINGS TO NOTE: ○ Contact lenses are LESS plastic than care systems ○ There are CL recycling programs 11