Corneal physiology & contact lenses-2

1. Corneal physiology & contact lenses-2 Rigid contact lenses III RGP lens care & patient education INSTRUCTOR: AREEJ OKSHAH OTUM 19/11/2009

2. Care system i.e. care regimen • Wetting & soaking Most solutions used for wetting & soaking of RGP lens have many functions in the same solution; enhance the wettability of the lens surface; maintain hydration state (as in the eye); disinfection The most important components in these solutions are the preservatives & wetting agents

3. ……….Wetting & soaking Disinfection: • using the lens care system to minimize the micro-organisms (e.g. could cause microbial keratitis & conjunctivitis) that challenge the eye especially in the presence of the lens • Factors that enhance the contamination include: with the contact lens by way of patient’s hands; contaminated lens products; lens care packaging; lens case • Disinfection of GP lens is accomplished by the presence of lens care product preservatives; lens disinfecting agent • Preservatives are active chemical ingredients; either bactericidal (killing microbes) or bacteriostatic (inhibit their growth): preservatives should provide the required degree of infection (different environments); not cause toxicity; compatible with the tear film; compatible with the lens materials to avoid adverse effects. The most commonly used are BAK, chlorhexidine, thimerosal, EDTA (ethylenediamine tetra-acetate), benzyl alcohol, polyaminopropyl biguanide…..

4. ……….Wetting & soaking Wetting agents • Wetting/soaking solutions contain polyvinyl alcohol (PVA), or methylcellulose derivatives as wetting agent: • PVA: is water soluble; relatively nonviscous; nontoxic to the eye; good wetting on the eye & the lens surface; • Methylcellulose: retards the regeneration of corneal epithelium; preferable with more viscous RGP lens solutions

5. Cleaning • Cleaners include: - Nonabrasive surfactants: i.e. detergent cleaning agent to move contaminants (lipid,mucoproteins,debris) from the lens surface; rubbing the or pressure should be applied to remove deposits from RGP lens - Abrasive surfactants: i.e. abrasive particulate matter as adjunctive agent in removing deposits that are difficult to remove by surfactants alone - Surfactant soaking & multipurpose lens care products: traditionally; separate soaking & cleaning solutions (2 bottles); now one-bottle GP lens regimen combining these. These are surfactant soaking and are intended to dissolve deposits during overnight soaking cycle so little pressure is needed - Enzymatic cleaning (liquid or tablets): using weekly enzymatic cleaning regimen for GP lens is important - Special techniques: e.g. cotton tipped applicator with few drops of abrasive surfactants to swab the inside of the lens in addition to the regular regimen & enzymatic cleaning; in case of build-up deposits - in-office polishing & cleaning can be done annually; but renew the lens the other year

6. Patients own lenses should be stored in hydrated state after removal to maintain hydration & disinfection & wettability & to minimize surface scratch of the GP lens because it’s used often or regularly • For office or lab.: store in dry state: Disinfection(5-10mins soak in H2O2 disinfecting system) then dry the lens ,  cleaning & rinsing followed by wetting/soaking prior using dry GP lens

7. Compliance with lens care regimen • Ocular complications associated with non-compliance are more common with soft lens wearers. However non-compliance with the recommended care guidelines for GP lenses causes problems as well .>>>examples for non compliance: • Patients doesn’t clean the lens as desired • doesn’t adhere to the prescribed wearing schedule • doesn’t use disinfection properly • doesn’t wash hand before lens handling • using inappropriate wetting solution e.g. saliva or tap water (acanthamoeba infection) • using expired solutions • case is not cleaned or replaced regularly • switching to another solution’s brand

8. Rewetting & lubrication • Using a solution for rewetting the GP lens while it still on the eye to rewet the lens surface; to stabilize the tear film; to rinse debris; to break loosely attached deposits e.g. PVA, methylcellulose, preservative-free rewetting drops

9. Dispensing visit procedures • V.A: reductio of V.A compared to the base line do biomicroscopy to check the lens position & wettability • Over-refraction: V.A should be almost equal to the expected V.A…. If not do monocular sphere over-refraction • Biomicroscopy: to evaluate lens centration, lag, fluorescein pattern, wettabilty…. Wide beam; low intensity white light; low magnification

10. Important to patient's education • Handling • Insertion • Removal • Cleaning • Care regimen • Avoid scratch especially when dropping the lens on hard surface • Foreign body particles like dust could cause discomfort should remove the lens • Cosmetics (could cause discoloration, damage, surface deposits should applied after application of the lens) • Swimming: not recommended to wear GP lenses; unless wearing goggles

11. Adaptation • Tell the patient that adaptation may take from 10 days to 4 weeks until achieving of no lens awareness…evaluate tearing & discomfort • Wearing schedule: Day 1: 4 hours Day 2: 4 hours Day 3: 6 hours Day 4: 6 hours Day 5: 8 hours Day 6: 8 hours Day 7: 10 hours Day 8: 10 hours But all-day RGP lens users should start to wear it 12hours a day Immediately

12. Visits schedule • Daily RGP lens wearers (DW): Visit 1: 1 week after dispensing Visit 2: 1 month after 1st visit Visit 3: 3 months after visit 2 Visit 4: 6 months after visit 3, then every 6 months • Extended RGP lens wearers (EW): Visit 1: 1 week after dispensing (should wear daily wear lens firstly) Visit 2: 24 hours after initiating EW Visit 3: 1 week after initiating EW Visit 4: 2 weeks after visit 3 Visit 5: 1 month after visit 4 Visit 6: 3 months after visit 5, then every 3 months