Here are some of our past articles published.

In view of Miss N.’s question in the Questions & Answer Mailbox page, a good start to the article section is an essay on contact lenses and the cornea. Many people treat the two separately. This is wrong!!

Anatomically, the cornea comprises of 5 layers, from the external to the internal, (1) epithelium, (2) Bowman’s membrane, (3) stroma, (4) Descemet’s membrane, and (5) endothelium. The epithelium consists of some 4 to 5 layers of cells which are constantly generated from the innermost layer next to Bowman’s membrane. The outermost cell layers are being shed off continuously. Clinically, the epithelium is the first line of defence against bacteria and other organisms. Bowman’s membrane is a thin structure separating the epithelium and the stroma. The stroma takes up some 90% of the entire thickness of the cornea. It consists of fibrous tissues arranged in a regular fashion. This regularity helps in maintaing the corneal transparency. Descemet’s membrane is a thin membrane that separates the stroma from the endothelium. Finally, the endothelium is a single layer of cell in contact with the aquous humour. To prevent excessive water entering the cornea from the aquous humour, endothelial cells have "pump mechanisms" to maintain the water content of the entire cornea.

When a contact lens is worn on the cornea, it becomes a barrier to oxygen and essential nutrients. The fit is of paramount importance irrespective of material, soft or hard. A well fitted lens will have fulfilled a number of criteria, namely, (1) good visual acuity, (2) comfortable, and (3) healthy eye tissues which include the cornea, limbus and the conjunctiva.

On the other end of the scale, a poorly fitted lens usually compromise any or all the 3 criteria. Due to the warm climate here, these criteria have to be met even more stringently. When compromise occurs, there are certain changes that take part on the eye, some permanent, whilst others are reversible. One of the most common signs are the red "veins" surrounding the cornea. These "veins" are actually arteries. Arteries send in fresh blood whereas veins carry the waste and carbon dioxide away. These arteries are grown from the surrounding tissue into the stromal layer of the cornea. Due to the badly fitted lens, there is hardly any oxygen and nutrient supply to the cornea. The arteries are grown as a "defence mechanism" to furnish the cornea with the neccessary oxygen as well as nutrients. If the badly fitted lens is used regardlessly, the area where the new atrteries are grown will become cloudy, and the cornea becomes oval in appearance since the upper and lower areas are most susceptible. Serious injuries can occur when more corneal layers are involved. The epithelial layers are easily damaged by suffocation. The cell walls weaken and the cornea is open to attacks by microbes which include bacteria, viruses and fungi. When the endothelium is jeopardised, grave harm occurs and the cornea becomes cloudy. Obviously, due to space concerns, this is a simplified version of corneal pathology involved by contact lenses.

So, you will probably think, what brand of contact lenses is best? Well, it is actually what lenses that SUIT you best. This is DEFINITELY NOT the common mantra of changing to another brand of lenses should you have problems with one brand of contact lenses.

How much knowledge of the cornea does one need to have to choose one brand of contact lenses over another? Compare that question to how much knowledge one needs to have to fit a most suitable pair of lenses on your cornea. The answer to the first question is NONE or very little. Today, contact lenses are commonly sold over the counter based on power alone, without any eye examination. Anyone can simply conduct that sale. On the other hand, to fit a proper pair of contact lenses requires knowledge regarding the anatomy and physiology of the cornea, biochemistry, contact lens materials, microbiology, bacteriology and other related fields.

There are many different types/designs of lenses available today. Consult an optometrist to determine what lenses suit your eyes best.