Contact lenses - Optometrists Association Australia：隐形眼镜的验光师协会澳大利亚.pptVIP

Contact lenses Contact lens fact Contact lenses were thought of as early as 1508 when Leonardo da Vinci sketched and described several forms of them Contact lens technology Contact lenses are a changing area of optometry with new lenses constantly being developed What do contact lenses do? Contact lenses correct refractive errors Contact lenses are placed directly on the cornea lid margin iris cornea conjunctiva sclera pupil Diagram of the eye Normal focus Short sightedness (Myopia) Distance vision blurry, near vision usually ok Short sighted focus Short sighted correction Long sightedness (Hyperopia) Difficulty seeing clearly and comfortably up close Long sighted focus Long sighted correction Astigmatism The eye is shaped more like a football than a basketball Focusing error that causes blur in one direction Types of contact lenses Rigid gas permeable (RGP) lenses Soft lenses Disposable or non-disposable Coloured or clear Spherical or toric Extended wear Multifocal RGP lenses (rigid gas permeable) Smaller than size of cornea May be less comfortable than soft lenses initially Very effective in correcting astigmatism Soft lenses Most commonly used (90%) Made from hydrogel plastic material containing water 1-2mm larger than cornea Easy to adapt to Spherical lenses Correct short or long-sightedness Cheapest, most comfortable lenses Available in disposable form Toric lenses Correct astigmatism Lens is specially weighted to fit the shape of an irregular cornea More expensive than spherical lenses Available in disposable form Disposable lenses Daily, two-weekly or monthly replacement Very simple cleaning (if any) Latest designs and materials Very popular Coloured lenses Handling tint Useful when inserting or removing Enhancing tint Makes light coloured eyes more vivid Opaque tint Can change brown eyes to blue Extended wear lenses New technology Made from silicone material which transmits oxygen well Wear for up to thirty days without removing Wi