T2b Preservatives Effects Ocular Surface

Overview of Preservatives in Ocular Health

  • Preservatives are used in ocular medications to prolong shelf life but can adversely affect the ocular surface.

Effects of Drugs on Corneal Epithelium

  • Drug effects categorized by damage potential:

    • No Damage:

      • Atropine

      • Chloromycetin

      • Gentamicin

      • Methylcellulose

      • Polyvinyl alcohol

      • Saline

    • Moderate Damage:

      • Pilocarpine

      • Fluorescein

      • Rose Bengal stain

    • Important Damage:

      • BAK (Benzalkonium Chloride)

      • Topical anaesthetics

Benzalkonium Chloride (BAK) and Corneal Damage

  • Histological analysis reveals:

    • BAK reduces epithelial thickness

    • Induces nuclear condensation and vacuole formation

    • Dose-dependent decrease in cellular viability

Comparison of Preservatives

  • BAK vs Polyquad vs SofZia:

    • SofZia preserved Travoprost shows greater cell survival compared to travoprost preserved with BAK.

    • Travoprost containing polyquad performed better than its BAK preserved formulation

Ocular Absorption and Benzalkonium Chloride

  • Examination of pupil diameter post-instillation suggests:

    • Influence of BAK on ocular absorption.

Use of Preservatives in Medication

  • Should preservatives be included in certain medications?

    • Dry Eye Products:

      • No!

      • Preservatives worsen compromised tear film.

      • Shift toward unit dose products and ointments.

    • Ocular Anti-inflammatory Agents:

      • Preferably preservative-free due to increased susceptibility of inflamed eyes to surface damage.

    • Glaucoma Medications:

      • Long-term, asymptomatic treatment where ocular irritation can lead to discontinuation; however, BAK boosts drug absorption to the posterior segment.

Ocular Medicamentosa

  • Defined as chemical irritation or ocular tissues caused by topically applied drugs or preservatives, or by environmental or occupational substances

  • Notable irritants include:

    • Brimonidine

    • BAK

    • Prostaglandin analogues

  • Related factors:

    • Drug count, dosage/frequency, treatment duration, age, preexisting ocular surface health.

  • Symptoms include:

    • Ocular pain, stinging, burning, photophobia, redness, lid swelling, blurred vision.

  • Signs include:

    • Punctate staining, oedema of cornea/conjunctiva.

  • Treatment options:

    • Cessation of irritating medication, use of preservative-free alternatives, tear lubricants, possible short course of topical steroids.

Glaucoma Medications

  • Multiple medications and doses are applied daily for chronic conditions.

  • Chronic, long-term use can span decades, making cessation challenging due to severe consequences of untreated conditions.

  • Persistent use can lead to long-term effects on lid margins, cornea, and conjunctiva, resulting in ocular surface disease and permanent dry eye.

  • Non-preserved unit dose options available include Lumigan PF and Ganfort PF, while less cytotoxic preservatives in formulations like Travatan, Duotrav (Polyquad), and Alphagan P (Purite) can help but remain pro-inflammatory/cytotoxic.

  • Compliance with medication can be affected by severe symptoms resulting from treatments for an otherwise asymptomatic condition in mild to moderate cases.

Ocular Surface Impact from Glaucoma Medications

  • Associated signs include:

    • Abnormal Schirmer test

    • Abnormal tear osmolarity

    • Meibomian gland dysfunction

    • Lid margin vascularization

    • Corneal/conjunctival staining

    • limbnal or bulbar hyperaemia

    • punctate epithelial erosions

  • Prevalence of ocular surface disease (OSD) in patients on various topical therapies is significant.

Safety Concerns with Unpreserved Preparations

  • Unpreserved fluorescein: Pseudomonas can use fluorescein as an energy source, now supplied on dry filter paper

  • Unpreserved saline: touching the tip introduces bacteria

  • Unit doses and minims: no need to contain preservatives, eliminates tear and cornea toxicity, expensive

  • Tap water: Contains acanthamoeba, free living protozoan which causes severe corneal ulceration, don’t rinse contact lenses in tap water or use dirty lens cases

Contamination Risks in Diagnostic Minims

  • Study outcomes highlight microbial contamination risks in reused minims.

  • Cost analysis shows significant financial implications in reducing contamination risks.

Contamination of Autologous Serum

  • Risk of bacterial and fungal contamination in autologous serum eye drops is low, but monitoring is critical for safety.

  • not preserved

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