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