1 Contact lenses-2 - Advanced Applications of Contact Lenses-2 - Complications of contact lens wear Instructor: Areej Okashah 7/1/2010

2 Orthokeratology:  i.e. contact lens corneal reshaping: is the planned application of specially designed RGP contact lenses to reshape the cornea; this temporarily reduces myopic refractive error & improves unaided visual acuity.  This procedure allows patients to see well enough in order to perform daily activities without the need for spectacle or CLs correction for at least part of the day…  Orthokeratology has been practiced for more than 40 years; however its efficacy & safety still controversial

3 …  Overnight wear of ortho-K is relatively a recent development  Remember that conventional rigid lenses have secondary & peripheral curves that are progressively flatter than the central (base) curve  Modern ortho-K lenses employs a reverse-geometry lenses to produce the desired corneal changes; these lenses have secondary peripheral radii of curvature that are steeper than the back optic zone radius (BCR). This alteration in design allows the lens to re-approach the cornea beyond the base curve which results in improved lens centration. & this steeper secondary curve causes the corneal tissue to redistribute radially from the centre of the cornea causing the central corneal epithelium to thin & the peripheral epithelium to thicken leading to refractive error changes

4 ….  Recently used ortho-k lenses have high oxygen permeability; which makes it possible to apply the lens on extended wear bases or overnight wear schedule  Overnight wear of ortho-K lenses advantages include: convenience for patient as no optical devices are required during the course of the day; better ocular health as the wearing time decreased; little adaptation to lens is required; increased effectiveness because there is an increased eyelid pressure from closed eyes & rapid eye movement during sleep. & could retard myopia progression in children.  Ortho-K has been found in some clinical trials to correct or 6.00 diopters of myopia & little or no astigmatism

5 ….  Some patient discontinue ortho-k use because of: residual astigmatism; poor comfort; treatment failure; poor motivation; unideal lens fit  Overnight ortho-k could have some complications e.g. corneal staining; corneal ulcer; CL adherence  these are relatively similar to complications of using conventional CLs..  Good candidates: patients with one to six diopters of myopia; & who have less than two diopters of with-rule-astigmatism; & who have pupil with small-or-average-diameter

6 Ocular complications related to contact lens wear…………………..

7 Complications of CL wear:::  Corneal vascularization  Immunologic complications  Infectious keratitis  Mechanical complications

8 Corneal vascularization CV  Vascularization i.e. neovascularization is the appearance of new vessels within a tissue  In general its not uncommon  CL wear is the major risk factor for CV  The risk of CV is not the same for all CL types; e.g. RGP lens < soft  When firstly detected; new vessels is a warning sign for further damage,

9  CV could scatter incident light & reduce corneal transparency; there could be a potential for visual interference  CV is an indicative sign for immune privilege within anterior the chamber  this could increase the risk of infection or inflammation  Hypoxia, epithelial injury (could affect the integrity of tear film)& wearing time (longer wearing time is associated with higher risk for CV), significance of limbal hyperaemia are risk factors that can be associated with CV

10  Treatment outcomes are better when CV is detected early…. firstly should remove the causative factor in this case CL Evaluate lens fitting characteristics ; material properties; cleanliness (deposits); lens parameters Advice: reduce wearing time; switch to another lens material; water content; DK

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12 Infectious keratitis  Causes of non-infectious keratitis: tear film abnormalities; immune reaction; chemical injuries etc.  Causes of infectious include: bacteria; protozoa; fungi; viruses  Risk factors in infectious keratitis: alteration of ocular normal flora (e.g. staphylococcus epidermidis; S aureus, propionibacterium acnes); noncompliance with standard CL disinfection and storage (mostly pseudomonas); virulent organisms (e.g. Serratia & Bacillus in CL solutions); contaminated CL (mostly pseudomonas); diabetes mellitus

13  Bacterial keratitis non-related to contact lens wear mainly caused by gram-positive bacteria e.g. Staphylococcus, Streptococcus  Bacterial keratitis related to CL wear mainly caused by Gram-negative bacteria e.g. Pseudomonas; Serratia.  Protozoal keratitis related to CL wear: e.g. Acanthamoeba ; usually from contaminated lens solution  Viral infections related to CL wear are rare but could enhance other microbial infections of the cornea

14  Common symptoms for infective keratitis: pain; photophobia; tearing; blepharospasm; reduced vision, discharge (watery, or purulent)  Treatment could include :antimicrobial agents (e.g. neomycin; chloramphenicol); steroids; penetrating keratoplasty

15 Final exam: all the course material’s except the 1 st material Good Luck with your finals