C o n t a c t L e n s e sA n d M i c r o b i a l K e r a t i t i s

Irsalan Asif, Ritchie Aseke

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CONTENT

All about contact lenses

Incidence and routes to infection

Microbial Keratitis, treatments and Future therapy

Summary

Types of lenses:

• soft contact lenses made from silicon hydrogel [1]

- Permeable to oxygen to maintain healthier eyes in extended wear

- Better comfort

• Gas permeable contact lenses made from silicone acrylate or fluoro-silicone acrylate [2]

- Adhere within the cornea area

- Better for correcting irregular shaped eyes

- More durable

• Used to correct visual impairments such as short-sightedness, long-sightedness, presbyopia and astigmatism

* Picture1 from

Contactlenses.org

Incidence of infection:-

• 125 million contact lens wearers globally in 2011

• An international survey conducted in 39 countries between 2006 and 2010

[3]:-

– Approx. 24 cases in every 10000 wearer per year had microbial

keratitis

– Use of extended contact wear increases incidence of infection by 4 in

comparison to daily wear [4]

– It varies widely with the type of contact lens and pattern of wear

Incidence of infection:-

• Australia, 12 months study between 2003 to 2004 [5]:-

– 4.2 per 10000 wearers are affected per year by microbial

keratitis

• Hong Kong [6],

– 3.4 per 10000 wearers

• UK,

• 3.6 per 10000 wearers

Routes to infection• bacterial adherence to the lens [4]

– The surface is suitable for bacterial adhesion

– They sustain a large quantity of organisms in prolonged contact with the cornea

– formation of biofilm on the lens

• Comparison of Surface Roughness and

Bacterial Adhesion to lenses [7 & 8]

– Surface of cosmetic CLs are significantly

rougher than conventional lenses and the

initial adhesion of bacteria is higher on

cosmetic lenses

– After adhesion, the bacteria can progress to

form a biofilm

– To avoid bacterial keratitis, manufacturers

process for smoother CL surfaces* from Hong et al. 2014

• Bacterial contamination on contact lens storage case

– occurring in 30% to 85% of the cases.

– microbial factors such as biofilm formation and microbial resistance, may be

associated with persistent microbial contamination of contact lens storage cases.

– Higher likely-hood of biofilm formation due to the air-liquid interface

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Routes to infection

– Contact of the lens with contaminated region before

insertion re-infects the lens [9]

– On the case they switch from a planktonic phenotype

to a sessile biofilm phenotype in response to a low-

nutrient environment

– The mature biofilm is significantly more resistant to

antimicrobial agents than planktonic cells

* From Stapleton and Wu, 2011

• stagnation of tear film behind contact lenses

– Lens divide the tear film into two layers [10],

• The pre-tear film in front

• The post-lens tear film between the

cornea and the lens

– Tear exchange reduces the build-up of

debris between the cornea to prevent

inflammation

– Tear stagnation delays removal of bacterial

exotoxins

– its impact in microbial keratitis is not fully

understood [11]

– Believed to reduce resistance of the cornea

to infection

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Routes to infection

* From Caroline and Andre, 2014

Microbial keratitis

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Diagnosis Patient will arrive complaining of a foreign body

trapped in her eye.

Symptoms

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Images of Microbial Keratitis

Staphylococcus Pseudomonas Fusarium Sp.

(Fungal)Acanthomoeba

Treatment

Fortified

antibiotics

Keratoplasty

4th Gen

Fluoroquinlones

Future Developments

Collagen Cross-linking

Photoactivation

Confocal Microscopy

Contact lens Hygiene

CXL

Photoactivation

Microscopy

Hygiene

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KEY TAKEAWAYS

124 cases in every 10000 wearer per year had microbial keratitis

Bacteria adhere to contact lens and

contaminate contact lens disinfectant

solution

Contact lenses stagnate tear

exchange reducing resistance of the

cornea to infection

Microbial Keratitis is a sight

threatening illness.

The causative organism

determines the severity

There are many treatments and

future developments have made

attempts to speed recovery.

T H A N K Y O U !A n y Q u e s t i o n s ?

REFERENCES:1) Britiish Contact Lens Association, 2015. Types of contact lenses. [Online]

Available at: https://www.bcla.org.uk/public/types-of-contact-lenses [Accessed 16 March 2015].

2) Vista-Optics, 2014. Rigid gas permeable contact lens materials. [Online]

Available at: http://www.vista-optics.com/rigid-gas-permeable-contact-lens-materials.html [Accessed 16 March 2015].

3) Efron, N., Morgan, P. B. & Woods, C. A., 2012. International Survey of Contact Lens Prescribing for Extended Wear. Optometry and vision science ,

89(2), pp. 122-129.

4) Eltis, M., 2011. Contact-lens-related microbial keratitis: case report and review. Journal of Optometry, 4(4), pp. 122-127.

5) Stapleton, F., Keay, L., Edwards, K., et al. (2008) The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology [online], 115 (10):

1655–62.

6) Lam, D. et al., 2002. Incidence and riskfactors for microbial keratitis in Hong Kong: Comparison with european and north american. EYE, 16(5), pp. 608-

618.

7) Ji, Y.W., Hong, S.H., Chung, D.Y., et al. (2014) Comparison of Surface Roughness and Bacterial Adhesion between Cosmetic Contact Lenses and

Conventional Contact Lenses. Journal of the Korean Ophthalmological Society [online], 55 (5): 646

8) Giraldez, M.J., Resua, C.G., Lira, M., et al. (2010) Contact lens hydrophobicity and roughness effects on bacterial adhesion. Optometry and vision

science : official publication of the American Academy of Optometry [online], 87 (6): E426–31.

9) Stapleton, F. & Wu, Y., 2011. What is Happening in Your Contact Lens Storage Case?. [Online] Available at:

http://www.reviewofcontactlenses.com/content/c/27817/ [Accessed 16 March 2015].

10) Muntz, A., Subbaraman, L.N., Sorbara, L., et al. (2015) Tear exchange and contact lenses: A review. Journal of optometry [online], 08 (01): 2–11.

Schaefer F. Bacterial keratitis: a prospective clinical and microbiological study. British Journal of Ophthalmology. 2001;85(7):842-847.

Cdc.gov. Estimated Burden of Keratitis — United States, 2010 [Internet]. 2015 [cited 9 March 2015]. Available from:

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6345a3.htm

Picture 1: Contactlenses.org, 2013. What are GP contact lenses?. [Online]

Available at: http://www.contactlenses.org/whatare.htm [Accessed 16 March 2015].