EyeWitness

Winter 2017

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W hat is the anatomy of a contact lens? We know anatomy refers to the scientific study of the shape, structure and parts of living organisms like plants, animals and humans. It can also be described as the study of internal workings of things not living. So let's look at the anatomy of a contact lens and see what we find. A contact lens consists of a round piece of plastic having base curve(s), paracentral curve(s), posterior curve(s), and peripheral curve(s). It has a front optic zone and a back optic zone. It can be spherical or toric on the front and/or back. It can be spheric or aspheric. The peripheral curves can be standard geometry or reverse geometry. It can be single vision, bifocal, trifocal or multifocal, with toricity or without. I could go on and on with different combinations, all of them contained on a bit of plastic ranging from approximately 7.5 to 18mm in diameter. Contact lenses for uncomplicated corneas consist of a few of the "parts" listed above. But for the cornea with disease, trauma and/or high amounts of toricity, we need many "parts" to design a well fitted lens that provides the best possible vision. Leonardo Di Vinci saw such a patient and, after some postulation, put the man's face into a bowl of water and found, with the water surrounding the irregular areas of the cornea, the man could see better. That very first profile was quite important but equally impractical. However, it did lead to Leonardo sketching the first form of a new refracting surface for a cornea. This idea helped produce a device that would be a future treatment of optical defects on the cornea. In the following years, other attempts were made to design a contact lens, changing its anatomy, but the designs were not practical and were discarded. In 1884, anesthesia was introduced. Now a mold of the cornea could be produced so the shape could be duplicated. Wow! What's old is new again – a scleral contact lens, first made of glass! Fic, Kault and Muller designed the early scleral lenses. Now the fun began as new "parts" were invented to improve vision and comfort. In 1934, Obrig developed plastic scleral lenses that were easier to machine. Fluorescein could now be used to evaluate the morphology of a lens fit. The anatomy of these lenses changed many times. Fenestrations were added to The Bottom Line A Profile of the Anatomy of a Contact Lens By Nick Siviglia, Ph.D., Sc.D., FCLSA(H) 6 CLSA EyeWitness Winter 2017 Nick Siviglia, Ph.D., Sc.D., FCLSA(H), is founder and CEO of Lancaster Contact Lens, Inc. in Lancaster, Pennsylvania. He specializes in fitting and manufacturing contact lenses for the diseased, the disasters, and the difficult. Memberships include CLSA, CLMA, and CLAO. He has been a clinical instructor at Wills Eye Hospital, Osteopathic Hospital of Philadelphia, and Milton S. Hershey Medical Center of PA. Nick holds 18 patents – including the original patent for reverse geometry design and his Ni-Cone for keratoconus and post-PK. His specialty contact lens practice also includes fitting and manufacturing artificial eyes and scleral shells. eliminate edema and increase wearing time. The first scleral lenses were 23 to 26mm in diameter. Today, we average 13.8 to 18mm using high Dk materials producing a thinner lens with better vision and more comfort. Today's sophisticated manufacturing lathes allow researchers to invent better designs and materials. Yes, these lenses cost more than standard lenses. But they should cost more. The raw material and equipment to manufacture comes at a higher price. Greater expertise is required to manufacture a quality product. On the practitioner's side, more expertise and time is necessary to provide a proper fit that doesn't compromise the cornea. Back when I began my career, a slit lamp and a keratometer were the best tools we could ask for. The manufacturing was done entirely by hand using manual lathes and polishers. Today, we have incredible corneal topography equipment that can explain, even to the patient, the degree of complication with which we are faced. I strongly urge the use of corneal topography to improve the success of your contact lens fitting and shorten the number of visits required to obtain the best fit. Yes, new and better equipment costs money but it can pay for itself if you use it properly. Learn to use the best equipment and best contact lens products on the market to set yourself apart from the guy down the street or across town. Remember, the lab can only make a lens using the information you provide. In order to get all the parts, the anatomy, of the contact lens fitting properly, you must provide exact and accurate information. That's the Bottom Line! EW

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