There are many complications that the contact lens wearer may experience; complications that are either directly induced or complications that represent existing problems aggravated by the contact lens wear. The mechanisms by which the contact lenses induce alterations are: trauma, decreased corneal oxygenation, reduced corneal and conjunctival wetting, stimulation of allergic and inflammatory responses, and infection.
- Pain: all chronic patients using contact lenses may have hypoesthesia.
- Decreased visual acuity: irregularity of the anterior surface of the cornea.
- Conjunctival hyperemia
- Contact lens intolerance
Contact lenses alter the physiology and morphology of the epithelium and can influence corneal integrity. Signs include the following: punctuate epithelial keratopathy, epithelial abrasions, foreign body tracks, dellen, microcysts, vacuoles, mucin balls, dimple veiling. The presence of epithelial defects should be monitored closely, and they may require both temporary cessation of contact lens wear as well as possible prophylactic antibiotic therapy, refitting of contact lenses, and patient education.
This may result from either acute or chronic hypoxic corneal conditions, contact lens materials, and contact lenses that are inadequately fitted. To treat this condition one should select a lens material with higher oxygen permeability, decrease contact lens wearing time, and ensure an optimal contact lens fits.
Alteration of the corneal curvature that results from a molding effect produced by contact lens wear. Treatment consists in making sure there is no irregular astigmatism, contact lens refitting, and change material of lens.
All contact lenses reduce corneal sensitivity. Although the exact mechanism for corneal hypoesthesia remains elusive possible mechanism include:
- Sensitization to the mechanical trauma produced by contact lenses
- Corneal metabolic changes that affect corneal nerves.
Represent an immunologic reaction, and are the greatest diagnostic dilemma to early keratitis. It may result from contact lens wear itself, from endotoxins created by bacteria or from combination of two. Treatment usually consists of topical steroid drops along with prophylactic antibiotic coverage. Close follow-up care, especially early in treatment, should be provided to prevent inappropriate treatment of an early microbial keratitis and to monitor for improvement.
Develops in response to the same inciting factors that causes neovascularization in non-contact lens wearer, corneal hypoxia and inflammation. Treatment involves removing the inciting stimuli, and depending on the severity, a pulse of topical nonsteroidal anti-inflammatory drug or corticosteroids to aid in vessel regression.
It is one of the most serious potential complications from contact lens wearing. The incidence is low but contact lens wear is the primary risk factor for developing microbial keratitis, and risk varies based on the type of lens and the wearing schedule.
Pseudomonas Aeruginosa is the most common pathogen, also Staphylococcus, Streptococcus and Serratia are common microorganisms found in these patients. Another pathogen that is closely related to the use of contact lenses is Acanthamoeba. 88% of patients with Acanthamoeba keratitis wore contact lenses. This may be diagnosed through cultures, smears biopsy and confocal microscopy.
Treatment of microbial keratitis requires immediate and frequent antibiotic coverage with agents susceptible to the offending microorganism. Treatment is based on the severity of the corneal ulcer and whether it appears to be sight threatening or not. Sight threatening ulcers usually include the presence of any of the following characteristics:
- Anterior chamber response of grade 2+ or greater.
- Corneal infiltrate of > 2 mm in size.
- Corneal infiltrate < 3 mm from the visual axis.
- Worsening of clinical course following 48 hours of treatment.
Corneal ulcers that are not sight threatening are empirically treated with fluoroquinolones agents, sight threatening corneal cultures and Gram stain should be performed, and broad spectrum antibiotics and cyclopegics should be initiated while culture and specificity results are pending. Treatment should be modified as appropriate based on laboratory results. Traditionally cefalozin and fortified aminoglycosides are prescribed hourly alternating every 30 minutes. The antimicrobial agents are tapered as wound healing improves.
Treatment of Acanthamoeba keratitis involves a multidrug regimen of antiamebic drugs, which include polyhexamethylene biguanide, propamidine isethionate and neomycin.
- Mannis M. & Zadnik K (2003) Contact lenses in ophthalmologic practice Second edition Springer- Verlag
- Milton M. & Adrian S. (2006) Manual of contact lens prescribing and fitting Third edition, Eslseiver
- Millis E. (2005) Medical Contact Lens Practice First Edition Elseiver
- Franklin A. & Franklin N (2007) Rigid Gas Permeable Lens Fitting First Edition Elseiver