Power 10.5 D

[Luytin]

1. For a monofocal IOL: is there an equivalent in the language  of optometry (the numbers an optometrist uses in contact lenses) for an IOL of 10.5?  My left eye is to be corrected for distance, the best I could achieve for me. I am
very nearsighted, -9.50.  Is the model SN60WF of the Acrysof IQ IOL at 10.5 D about the same, stronger or weaker, than a -9.50 contact lens?  

2. What is the approximate length of time after cataract surgery for the eye to recover and see at the power
intended, given no other problems in the eye?  

[JohnHaganMD]

That's the long answer. The short answer is 1. No there isn't  2. It varies considerably some people read 20/20 the day after surgery other people it can take days to weeks. We generally consider the eye recovered (off medicines and stable refraction) 4 weeks after surgery.

JCH MD

[SoftwareDeveloper]

re: "same, strong, or weaker than a -9.5 contact lens"

Unfortunately there is no way to tell the IOL power from a contact lens power. The contact lens is correcting the focusing power of the whole eye, and the eye's  focusing power comes mostly from two different sources: the cornea's power and the internal lens power (whether thats a natural lens or an IOL). Two different people who wear a -9.5D contact lens may have entirely different corneal and lens powers that merely led them to need the same contact lens on top of the eye. For cataract surgery one person with a -9.5D contact lens who doesn't want distance correction afterwards might need a 10D IOL, another might need an 11D IOL, it depends on other eye measurements.

People who are highly myopic  have too strong a natural  lens power, e.g. perhaps their natural lens is 19D which then required  a negative powered contact  lens needs to be placed on top of it to bring things into focus. So when an IOL is placed, the IOL power will be less than the natural lens was, e.g. 10.5D to avoid the need for correction.

They can't actually directly measure the power of the IOL you will need, there unfortunately isn't an exact formula. Someone who had the exact same eye measurements as you would likely need the same lens power. So   what they do is take a variety of measurements of things like axial length, chamber depth and corneal measurements. They keep databases of the results of surgery for people with different measurements and the IOL power that would have worked best for them. They use statistical methods to  to create formulas that approximate what IOL power would work best for people given the measurements of their eyes. It isn't an exact science, there are a few different competing formulas based on different data and different statistical techniques.

Usually for most people of average vision the lens power is accurate, but  for high myopes unfortunately there is more of a risk the power may be off a bit. I suspect that part of the issue is that really high myopes are rare and so there is less data for them to rely on. There is some indication the issue may be a result of measurement issues, this page discusses the issues a bit though it may be too technical for most:

http://www.doctor-hill.com/iol-main/extreme_axial_myopia.htm

Usually with a monofocal lens you should see at the power intended when the bandage comes off. Unfortunately however the exact position of the lens can vary backward or forward and changes its power a bit. Usually they wait 3-4 weeks before giving a prescription for correction after cataract surgery if someone needs it, though sometimes they can wait another few weeks if it hasn't stabilized. I suspect usually any change is pretty minor.

The problem with predicting lens power accurately is what has led to the development of a Light Adjustable Lens where the power of the lens can be adjusted after surgery using a special UV light to fine tune it.  I don't know where you are located, the lens is available in many places outside the US but is still in the process of seeking FDA approval within the US. It is an inconvenient process it sounds like since for the first several days you need to wear special glasses to protect your eyes from UV light exposure until they have finalized the lens power. I don't know how much of a concern lens movement after that may mess up the power, but it gets things closer than a regular monofocal lens.

If you are set on using a monofocal lens, you might consider other brands. The Alcon lenses have been reported to have issues with glistenings compared to other lenses. The Tecnis lenses are made with a material with a higher Abbe that reduces chromatic aberration, as this opthalmology publication discusses which lists the abbe of different lenses:

http://eyeworld.org/supplements/EW-December-supplement-2014.pdf
" Cataract surgery with an IOL with an Abbe number greater than that of the natural lens (47) can improve CA, so that our cataract patients could actually experience better vision quality than they did as young adults. "

There are other monofocal lenses which claim to have a larger depth of focus, a bit more near vision, than a standard monofocal, like the Lenstec SoftecHD and the Hoya iSert Gemetric (which might not be on the market yet even though its FDA approved already). I don't know how those compare to Tecnis in terms of other factors.

If you don't like the idea of a multifocal, the Crystalens is a single focus lens which might accommodate to give more near vision. The Symfony  (not available in the US) gives an extended depth of focus with reportedly similar risk visual side effects to a monofocal, similar risk of halos and similar contrast sensitivity.