CHOOSING THE BEST PRESBYOPIC IMPLANT OR Pie (Pi in Eye)
Mirror, mirror on the wall, which lens is the best of all
Presbyopic Implant in Eye or PIE is the cure for presbyopia. This method reverse the effect of aging eyes. PIE cures presbyopia and prevents cataract formation. With one procedure you are able to tackle multiple handicaps. You can correct astigmatism, nearsightedness and farsightedness. Presbyopia is corrected and cataracts are prevented.
An important part of the Pi in Eye(Pie) surgery is the artificial biocompatible presbyopic artificial lens, which allows one to see far and near in each eye. These are known as Presbyopic implants or Pi. They are made by artificial means and not taken from cadavers. These lenses do not propel any allergic response when situated in the eye.
ZONES OF VISION
As one may note PIE has many advantages over Lasik. PIE gives vision at all distances.Distance, Middle and Near Lasik affords vision at one focal length.When a long person has lasik they are able to accommodate to bring the other two zones in focus.For people in presbyopic age Blend Or Monovision Lasik eye surgery has been a compromise.
Types of (Pi) Presbyopic Implants (FDA Approved)
Crystalens is an accommodating back chamber intraocular lens made of silicone. It is also a modified foldable plate haptic lens with hinges across the plates and includes two flexible colored polyamide loops attached extremity of the plates. The opic zone is small at 4.5mm. This lens should not be placed in the ciliary sulcus. Also it should not be implanted if there is a zonular rupture or if the bag is not intact. Additionally, YAG capsulotomies should be delayed for a minimum of four weeks after the lens implant surgery. Moreover the capsulotomy should be smaller than the optic size or the lens can get dislocated. The cryalens does not drastically absorb UV light from the sun so protective UV sunglasses should be worn after surgery. This lens moves mechanically to yield 1.0 diopter of monocular space. Lens safety for this lens is good as hinge movement of one billion cycles at ten cycles per second has been documented. Roughly 95% of visible light is transmitted. This lens has undergone several refinements and currently the 5th generation Crystalens and Crystalens AO changes are available. Crystalens HD was lately stopped as AO has proven to be better.
Figure 1. A Crystalens
Crystalens transmits 100% of light rays regardless of the eye pupil size. Its aberration-free aspheric lens permits great contrast sensitivity. In addition, individuals who have an astigmatism can accept this lens better. It also permits some torque without upsetting vision. Patients display better vision seven years post surgery than at the time of surgery.
Restor is an acrylic IOL that partakes the fundamental construction of a central optic and two arms or haptics for stabilization. This lens can be a one or three-piece foldable lens that is implanted into a bag or ciliary sulcus. It consists of nine steps of decreasing heights giving energy for certain lighting conditions and activities. This lens does not require any ciliary muscle or movement to function. The +3.0 diopter on the lens yields a power on the cornea equal to wearing +2.5 readers, which allows for near vision. A refractive region that leads light to distal focal point encompasses the diffractive region. The asphencity of the optic counteracts for the corneal circular irregularities. The chromophore filters blue light without impacting color vision or the quality of vision. Certain optical effects may be expected including halos around light during low light or in nighttime settings.
Tecnis lens is designed of a UV blocking hydrophobic acrylic. It is like a magnifying glass in that it is biconvex shaped with diffractive rings on the back surface. The addition of the lens is that it is a plus 4 diopter. It is mad in a patented diamond cryolathing process which means the material and the shape are formed in the one step. The Tecnis lens is a clear transmitting more light although the increased number of rings can sometimes cause glare.
Comparing the PIE
The Restor lens offers vision at all distances retaining the natural three-dimensional visions. The most popular lens is this lens and fits the necessities of most patients. Seldom though some patients are bothered by glare, haloes, or lack of crispness of vision. Also individuals with the Restor lens need more light in dark settings. The Tecnis lens on the other hand does not require extra light in dark settings. Therefore it is popular in individuals employed in low light conditions. The downside of the Technis lens is that it may cause glare and haloes while driving and vision for computers is not flawless. The Crystalens has the least glare and is the best choice for computer use. Yes, it can be confusing but not one lens is best. If one lens were best then only one lens would exist. It is the job of the doctor to fit each individual with the best lens for his or her lifestyles. Here are some overall Advantages and Disadvantages of each lens:
- Advantages:Clear vision for 2.5/3 zone
- Disadvantages: May need glasses occasionally
- Advantages: Full range of vision (3/3)
- Disadvantages: Extra light for reading
- Advantages: See well for distance, middle and near
- Disadvantages: Glare
If you want to look at some examples to clarify how the ideal lens should be chosen: Call us (661) 495 2020
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By Rajesh Khanna, MD