Contact Lens Related Keratitis Notes

Ulster University - Contact Lens Related Keratitis

Learning Outcomes

  • Outline the incidence of CL Microbial Keratitis.
  • Describe risk factors for CL Microbial Keratitis.
  • Describe signs and symptoms of CL Microbial Keratitis.
  • Discuss the prevention and management of CL Microbial Keratitis.
  • Describe the presentation and aetiology of Solution Induced Corneal Staining (SICS).

What Is Keratitis?

  • A broad term used to describe practically any inflammation of the cornea.
  • May be the result of:
    • Physical agents e.g. abrasions, dust
    • Chemical agents e.g. UV light, solution toxicity
    • Infective agents

CL Related Keratitis

  • Divided into three sections:
    • CL Induced Microbial Infiltrative Keratitis (CL-MIK)
    • Toxic Keratitis
    • Solution Induced Corneal Staining (SICS)

CL Induced Microbial Infiltrative Keratitis Definition

  • Most severe reaction that can occur in response to contact lens wear.
  • “An inflammation of the corneal tissue due to direct infection by a microbial agent such as a bacterium, virus, fungus or amoeba”

Incidence of CL-MIK Pre-SiHy

  • Poggio et al, 1989
    • 4.1 cases per 10,000 Px per year for soft DW
    • 20.9 cases per 10,000 Px per year for soft EW
  • MacRae et al, 1991
    • 5.2 cases per 10,000 Px per year for soft DW
    • 18.2 cases per 10,000 Px per year for soft EW

Incidence of CL-MIK Post SiHy (MK in Australia)

  • Stapleton et al, 2009
  • Lens Type vs. Incidence of MK per 10,000 Wearers:
    • DW GP: 1.2
    • DW SCL: 1.9
    • DW DD SCL: 2.0
    • DW SiHy: 11.9
    • Occ O/N SCL: 2.2
    • Occ O/N DD SCL: 4.2
    • Occ O/N SiHy: 5.5
    • CW SCL: 19.5
    • CW SiHy: 25.4

Relative Risk Dart et al, 2008

  • 2 year study, examined 367 cases of MK
  • Relative risk MK significantly increased with DD wear (RR 1.56) v disposable wear (R 1.0)
  • Differed between DD brands
  • But risk of vision loss with DD was less than for other disposable lens types
  • RR for occasional overnight wear was 1.87
  • RR for overnight wear was 5.4

Risk Factors for CL MIK

  • Hypoxia
  • Patient non-compliance
    • Poor hand hygiene
    • Sleeping in CLs
    • Care system
  • Internet CL Supply
  • Swimming in CLs
  • Blepharitis
  • Diabetes Mellitus
  • Epithelial Trauma
  • Steroid Use
  • Warm Climate

Pathology of CL-MIK

  • Bacteria
    • Staphylococcus / Streptococcus
    • Pseudomonas Aeruginosa (60% CL Keratitis)
  • Fungi
    • Fusarium / Candida / Aspergillus
  • Protozoa
    • Acanthamoebas - found in soil, dust, water taps, swimming pools & hot tubs, air, nasal mucosa!!!
    • Exist in two forms- trophozites and cysts
    • Dramatic increase in this type of infection first noted in mid -1980s, particularly in CL wearers
    • Corneal signs often disproportionate to pain

Symptoms of CL-MIK

  • Moderate to severe pain of rapid onset
  • Continuing or worsening pain following lens should make the practitioner suspicious
  • Severe redness
  • Blurred hazy vision, reduced VA
  • Photophobia and lacrimation
  • Swollen, puffy lids

Signs of CL-MIK

  • Significant, corneal infiltrate (potentially large and dense), often central or paracentral
  • Diffuse infiltration surrounding lesion
  • Breakdown / full thickness loss of overlying epithelium
  • Corneal oedema may present as striae/folds
  • Limbal and bulbar redness extends as condition advances – circolimbal hyperaemia
  • Anterior chamber flare and hypopyon
  • Swollen, red lids
  • Discharge
  • Typically unilateral

Prevention of CL-MIK

  • General advice to patient
    • Improve hygiene – hands, lens case
    • Avoid tap water & home-made saline
    • Improve care system compliance
    • Avoid swimming / hot tubs with CLs
    • Maintain good lid hygiene
  • Prevent/ alleviate mechanical trauma
  • Discontinue EW, change to DW
  • Improve oxygen performance??
  • Fit GP lenses

Management of CL-MIK Optometric

  • Refer urgently to Ophthalmology / A& E

Management of CL-MIK Medical

  • Corneal scraping - identify the micro-organism
  • Use of broad-spectrum antibiotics prior to identification
  • Specific antibiotics, perhaps by sub-conjunctival injection
  • Mydriatics - prevent posterior synechia
  • Collagenase Inhibitors
  • Non-steroidal anti-inflammatory agents
  • Analgesics
  • Corneal Debridement – for drug penetration
  • Bandage lens – assist re-epithelialization
  • Surgical Intervention – Corneal Graft

Prognosis For Recovery

  • Depends on speed & efficiency of treatment
  • Prognosis is good if:
    • Px removes CLs promptly
    • Seeks immediate advice
    • Correct diagnosis is made
    • Appropriate and aggressive therapeutic measures are enforced
  • Slow course of recovery for acanthamoeba infection – periods of improvement and regression
  • Delayed or inappropriate treatment can result in total vision loss

Toxic Keratitis

  • Caused primarily by the anti-microbial agents in contact lens disinfecting solutions
  • Anti-microbial agents disrupt cell wall of the bacteria, may also break down epithelial cell walls, leading to a toxic reaction
  • Severity of toxic reaction dependent on concentration of agent and exposure time
  • Balance microbial efficacy against ocular toxicity

Toxic Keratitis Causative Agents

  • Thimerosal / Thiomersal
  • Chlorhexidine & Benzalkonium Chloride
    • Bind to CL materials, particularly when covered in protein deposits
    • Opportunity for ocular toxicity is high, due to long exposure time
  • Hydrogen Peroxide
    • Failure to neutralise disinfecting agent
    • Some systems self –neutralizing or “one-step”

Symptoms of Toxic Keratitis

  • Stinging on lens insertion
  • Ocular hyperaemia
  • Lacrimation
  • VA rarely affected

Signs of Toxic Keratitis

  • Bulbar conjunctival and limbal hyperaemia
  • Diffuse SPK, stains with fluorescein
  • Stinging sensation on insertion of the CL
  • Symptoms and signs resolve on discontinuation of offending solution
  • CLs may need replaced where the preservative has bound to the lens surface

Prevention of Toxic Keratitis High Molecular Weight Preservatives

  • Toxic keratitis less commonly noted since the introduction of high molecular weight preservatives
    • Polyhexanide
    • Polyquad
  • Not absorbed into lens matrix
  • More effective\ can be used at lower concentrations
  • Potential for toxicity /hypersensitivity reduced

Solution Induced Corneal Staining (SICS)

  • Soft lens materials
  • Annular ring
  • Temporary
  • Clinical significance?

Solution Induced Corneal Staining Solution-Material Biocompatibility

  • Andrasko & Ryen: staininggrid.com
  • Evaluation of solution/ lens interactions
  • Rates incidence for range of combinations
  • Based on worst eye only
  • 2 / 4 / 6 hour wearing periods
  • Five corneal regions – percentage staining
  • Subjective comfort assessed

Staining Grid Limitations

  • Small sample sizes in each study
  • Contentious colour coding initially
  • Limited published data / peer review
  • Clinical significance uncertain
  • No/limited statistical analysis

IER Study

  • Carnt et al
  • Larger clinical trial, longer study duration
  • Repeated assessments
  • Grading technique
  • Contrasting findings
  • Fuels debate

IER Study Findings

  • The IER MATRIX STUDY: Corneal Staining
  • Solution-Induced Corneal Staining per month with the combination*
    Lens / Solution
  • CLEAR CARE® H₂O₂
  • AQuifyⓇ MPS PHMB
  • OPTI-FREE Express® POLYQUAD® and ALDOX®
  • OPTI-FREE RepleniSH® POLYQUADⓇ and ALDOX®
  • ACUVUE® ADVANCE™
    • 0.0%
    • 0.9%
    • 0.0%
    • 0.0% (2W)
  • ACUVUE® OASYS™
    • 0.9% (2)
    • 2.5% (2)
    • 6.2%
    • 7.1% (2W)
  • O₂OPTIX™
    • 0.5%
    • 5.9%
  • PureVision
    • 0.9%
    • 3.2%
    • 23.2%
    • 6.7%
    • 11.3%
    • 14.2%**

Understanding This Data

  • Internationally accepted clinically significant staining is Grade = 3 coalescent macropunctate
  • Andrasko grid shows that most lens/lens care combinations represent clinically insignificant Grade 1 micropunctate or Grade 2 macropunctate
  • Superficial, transient corneal staining occurs in lens and non-lens wearers
  • Based on scientific data, is not a risk factor for lens related corneal infection

Further Developments

  • Hypothesized that SICS appearance was not indicative of actual tissue damage - but a consequence of the fact that PHMB and fluorescein molecules can complex together.
  • Attachment of these groups to the epithelial surface was proposed to mimic the appearance of staining.
  • But other studies suggested SICs represented real change in epithelial cell behaviour.

Laboratory Studies

  • Bandamwar et al grew corneal epithelium cells in culture and subjected them to various kinds of stress, including mechanical and chemical sources.
  • Cells that were stressed but still viable, significantly hyper-fluoresced
  • Bakaar et al showed that the distribution of the hyperfluorescent cells on culture plate replicated the punctate appearance of staining seen clinically

Conclusions

  • Further studies implicated surfactant agent in MPS as influential in fluorescein transport across cells
  • Together, studies indicate that without causing cell death, MPS can alter cell behaviour in respect of their uptake of fluorescein.
  • When this occurs, the appearance of the affected cells mimics both the characteristic punctate appearance and transient nature of SICS.

Further Reading

  • Efron N (2012) Contact Lens Complications 3rd Edition (Chapters 24 & 25) Elsevier. Edinburgh
  • Efron N (2002) Contact Lens Practice (Chapter 39) Butterworth Heinemann. Oxford
  • Carnt N, Willcox M et al. Corneal Staining: The IER Matrix Study. Contact Lens Spectrum, Sept 2007.
  • Papas E (2019) Staining Wars. Contact Lens Update, July 2019. https://contactlensupdate.com/2019/07/16/staining-wars/