About contact lenses the types and the problems that can be caused. Microbial keratitis is used as an example and th diagnosis, treatment and future developments are looked into

1. C o n t a c t L e n s e s
A 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

3. 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

4. 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

5. 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

6. 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

7. • 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

8. • 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

9. Microbial keratitis
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10. Diagnosis Patient will arrive complaining of a foreign body
trapped in her eye.

12. Symptoms
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13. Images of Microbial Keratitis
Staphylococcus Pseudomonas Fusarium Sp.
(Fungal)
Acanthomoeba

14. Treatment
Fortified
antibiotics
Keratoplasty
4th Gen
Fluoroquinlones

15. 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.

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

18. 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].