Contact Lens & You

Written by: editor Oct,29 2013 09:28 AM
Making Sure that you are well-informed of what you are getting your eyes into, eye specialist (opthalmologist) Dr Hoh Hon Bing writes on contact lenses and you. 

Contact lenses are used primarily for the correction of refractive errors namely, short-sightedness (myopia), long-sightedness (hyperopia) and astigmatism.  Other uses include cosmetic contact lenses (to change the colour or appearance of the eye) and therapeutic contact lenses (to bandage the eye and reduce pain caused by abrasion or cornea oedema).

 
                                 



There are millions of contact lens users in the world and most users do not have any problems.  Contact lenses were first introduced in 1970s and the popularity increased as the contact lens design and material improved the comfort level for the users.
 
Contact lenses are used primarily for the correction of refractive errors namely, short-sightedness (myopia), long-sightedness (hyperopia) and astigmatism.  Other uses include cosmetic contact lenses (to change the colour or appearance of the eye) and therapeutic contact lenses (to bandage the eye and reduce pain caused by abrasion or cornea oedema).

 
                                 

Contact lenses sit on a layer of fluid tear film on the cornea.  It corrects the refractive error by changing the curvature of the cornea and allowing the image to be focused on the retina.  This solution is temporary and vision becomes blurred again when you remove the lenses.  A more permanent solution is LASIK laser eye treatment which changes the cornea curvature permanently (see www.excelview.com).  

Contact Lense Problem 

Complications associated with contact lenses are uncommon (around 4-5% of users) and are associated with certain risk factors.  These are poor hygiene, over-wearing (including wearing contact lenses during sleep), not adhering to contact lens regulations (using disposable wear contact lenses longer than the advisable time period ie using daily wear for more than 24 hours or monthly wear for more than 30 days). 
 
There are more common symptoms which are associated with contact lens wear but are not serious.  Nonetheless, these symptoms should be treated to prevent them from progressing to more serious complications.  In a way, these symptoms are sort of early warning system and if these problems are treated early by the eye doctor, serious sight-threatening contact lens complications should never occur.

 
 

                                                     

1. Dry eyes
 
Dryness sensation is the most common complaint by contact lens users and is related to both the number of years and number of hours per day of contact lens wear.  It manifest as gritty or foreign body sensation, requiring the user to blink more often and is aggravated by air-conditioner, fan, wind or smoke, worse later in the day or after reading (computer or book) for prolong periods of time.  Those users who have arthritis or auto-immune connective disease (Sjogren’s syndrome) or have undergone chemotherapy will have dry eyes and find difficulty wearing contact lenses.
 
Solution: Apply preservative-free lubricant eye drops on a daily basis (between 4-8 times daily) while wearing the contact lenses and not wait until the eyes hurt before applying.  The lubricant will establish a tear film for the contact lens to sit comfortably on the cornea without hurting the cornea cells.   


2. Neovascularization
 
This is a sign of hypoxia (cornea starved of oxygen) due to prolonged periods of contact lens wear (too many hours per day) and for too many years of wear (usually after 10-20 years).  The user will notice a red rim around the cornea usually towards the end of the day and on closer examination on a microscope, there is growth of new vessels from the periphery towards the centre of the cornea as it tries to deliver oxygen to cornea cells (Figure 1).  Although this condition is reversible (the redness and blood vessels will disappear when the user stops wearing contact lenses), persistence in wearing the lenses may cause the central cornea cells to die and predispose this area to an infective corneal ulcer.
 
Solution: Reduce the duration of contact lens wear to around 3-4 hours (enough for social functions or sports but not enough for a full day’s work at the office).  Alternatively, you could change the lens material to a higher Dk (measure of oxygen permeability) material that will increase the availability of oxygen to the cornea cells.  If neither of this works, you would have to stop wearing contact lenses or consider LASIK laser eye treatment.

                                                           
                                         Fig. 1 Neovascularization on the cornea (sign of cornea hypoxia)

3. Allergy
 
Very rarely, the user may develop itchiness or eye redness as soon as the lenses are in contact with the eye due to allergy to the contact lens material or the preservatives in the solution (Figure 2).  Some develop allergy after many years of wearing lenses in condition called giant papillary conjunctivitis (GPC).  Although treatment using steroid and antihistamine eye drops can provide temporary relief, it is very difficult for the patient to continue wearing contact lenses and they are advised to stop wearing contact lenses permanently.

                                                           
.                                                                 Fig. 2 Contact Lens Allergy

4. Infective corneal ulcer
 

When hypoxia or dryness is severe, the central cornea cells may die resulting in a cornea abrasion or erosion.  If the contact lens is poorly maintained or not cleaned regularly, bacteria may be present and will attack this area of weakness on the cornea causing an infective corneal ulcer (Figure 3).  This results in pain, blurred vision, tearing and light sensitivity and must be treated by an eye doctor urgently.  Any delay in the treatment may result in cornea scarring and permanent loss of vision.

                                                               
                                                      Fig. 3 Contact lens ulcer (white dot on the cornea)

Contact lens is an amazing invention which can correct eye sight and enhance the look of your eyes.  They are very safe provided you use them properly and look after them diligently. 
 
Be safe and always consult an authorized eye care provider and buy original.


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