Tuesday, March 20, 2012

Multifocal Lens Implants & Extreme Nearsightedness

Question: I have extreme nearsightedness and am considering multifocal lens implants. I am 52 year old male and have worn gas permeable contacts since age 15 and monovision for 10 years. I am extremely nearsighted with 18 diopters for right eye and 16 diopters in my left, as well as dry eyes and long eyeballs, from the extreme myopia. I work in an office, fish and hunt. Are multifocal lens implants a viable option? What about monovision? I would love to be able to see at all distances and not have to wear contacts or glasses but I understand that is probably very unrealistic. Given my particulars, what type of lens should I consider?

Answer: Being as nearsighted as you are most likely means that you do in fact have a very axially elongated eye. When this happens, it is not unusual to have some slight degree of retinal thinning and "stretching". When this occurs in the macula or the "center" of vision-even to a slight degree that does not directly impact visual acuity-it can cause a mild decrease in contrast sensitivity.

Multifocal Lens Implant designs are very complex and some may in fact provide a decrease in contrast sensitivity by their very design. Any reduction in contrast sensitivity from a Multifocal Lens Implant could pose a compounding effect and leave you with some annoying visual problems such as difficulty seeing in dim illumination or at dusk or even in inclement weather with cloud cover. While this may sound trivial, it can be pretty annoying. Not all Multifocal Lenses have this effect, but a conservative approach would be to provide the best possible optical Lens Implant solution given the optical complexity of your eyes. That said, the fact that you have been successful with monovision contact lenses could be a strong indication that you could also be successful with Monovision Lens Implants and thus enjoy a "glasses free" state for most activities. 
Creating a monovision correction, using either monofocal spherical, monofocal aspheric or monovision toric IOLs-if you have astigmatism-is potentially a "simpler" solution. One word of caution is that you will need to fully de-adapt from your Rigid Gas Permeable (RGP) contact lenses and will have to achieve stable corneal curvature and thickness, as well as adequate tear film quality and quantity. In some instances the long term wear of RGP contacts can alter the corneal shape and thus impacts the precision of the measurements and computations for the Lens Implants.
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