Presbyopia implant in eye has been the new revolution in vision restoration. It has eclipsed Lasik as the number one choice to improve vision in people over age fifty years.
A good tailor as well as a good surgeon knows that one size does not fit all. This holds true even with PIE. There are four classes of FDA approved PIE. These are Accommodative, extended depth of field (EDOF), Trifocal and Multifocal.
Accommodative PIE: This class of PIE were the first to be approved by FDA in 2005. They heralded the advent of PIE. Crystalens was the first out of the stable. It had various modifications till it evolved int Crystalens HD. Today we have Crystalens AO and Trulign. They are made of silicone. Crystalens AO has aspheric optics whereas Trulign has aspheric optics and built in astigmatism correction. They work by assuming a curved shape in the eye, increasing the range of focus. This shape and the unique design of the lens may also allow it to move forward and backward mimicking the natural lens. This lens has proved very useful in patients who have had previous eye surgery like lasik vision correction, radial keratotomy and other corneal procedures.
Extended Depth Of Field (EDOF)PIE: They are in a class of their own. They resemble multifocal PIE in appearance but function on a different optic principle. They increase the natural depth of field. It provides a continuous field of vision, though the range is not as extreme as in multifocal. Symfony and Symfony toric are the two contenders here. As you may have guessed from the names, sympfony toric can also correct astigmatism. Hence, they find great use in eyes with astigmatism. Both also are used in eyes where crystalens may not be an option.
Trifocal PIE: These PIE have apodaizations or rings in their center. The unique heights of the rings of this lens allow the incoming light to be split into three foci. One for distance, second for intermediate and third for near. Optical engineers can modulate the height of rings and distance between rings to design varying focal length for each zone. Currently we have Panoptix and astigmatism correcting Panoptix toric.
Multifocal: These are the lenses which arrived earlier than trifocal. They are truly bifocal but were labelled multifocal to distinguish them from bifocal glasses and contact lenses. Their mechanism of action is totally different than bifocal glasses. In bifocal glasses the top segment is for distance and lower for near. These are refractive lenses. This method was tried in the previous century but was not successful. Multifocal PIE are diffractive in construction and have a focal length for distance and one for near with an overlap for middle. They allow more light for far and therefore better distance vision. Restor and Tecnis are the two lenses in this class.
A surgeon who is an PIE expert needs to be proficient in all these types of presbyopia implants. Matching the best PIE to the patients’ after understanding the goals of the patients is paramount to success. This can sometimes involve implanting a different class of PIE in each eye.
Los Angeles Lasik Surgeon Rajesh Khanna MD is a recognized pioneer in Presbyopic Implants for correction of aging eyes. He has popularized Cornea Cross Linking and Intacs forKeratoconus. He is an Expert Cataract, Pterygium Eye Surgeon, A Cornea Specialist he performs Laser Corneal Transplants, DMEK, DSEK and DALK. Rajesh Khanna MD is a well known medical writer. He has published the bestseller "The miracle of Pi in Eye".He is also a columnist for the newspaper Acorn. Dr.Khanna also hosts "Medical Magic". In his spare time he hikes with his family and German Shepard or does yoga. He also plays field hockey and loves swimming.