Over-corrected following cataract operation

Many thanks.  My left eye op was in mid October, and the right eye will be operated on probably around February.  The decision is whether to a) have both eyes balanced at +0.5, then have them reduced to 0.0 or slightly less with laser, or b) whether to have the right eye set lower than the first from the outset ?

Obviously, you need to have a discussion with your opthamologist. But, if I were in your shoes, I will aim to have the right eye at -0.25. There is no advantage in having the 2 eyes balanced. Aiming for about -0.25 will hopefully give a margin so that you don't end up with farsightedness on the right eye also. Even if you end up with -0.5 in the right eye, you may not have to do anything for that eye (unless you end up with lot of astigmatism), because that just gives you mini-monovision which has its advantages.

re at201's comment: "26 inches (that is off by about 1.00 diopter"

Actually 26 inches is a focal point of about -1.51D diopters.  The formula is focal_point_centimeters = (100 / -diopters_focus). 

I'm hoping the suggestion of "both eyes balanced at +0.5" was miswritten or a misunderstanding of what the doctor said, since there is 0 reason for making the 2nd eye +0.5D vs. 0D, there is absolutely *nothing* gained by doing so and no remotely rational or competent doctor would propose such a thing, run from any doc clueless enough to do so. Leaving an eye farsighted with an IOL reduces visual quality at all distances. 

If you are going to want a laser tweak on the eye you've already had done, the question is whether you want the other eye set for full distance or nearer in. If you don't mind wearing glasses for full distance it may make sense to set both eyes for a bit nearer in.  The formula would be diopters = -(100 / focal_point_in_cm). Of course your eye sees some distance inward and outward from its best focal point.  You might consider one eye set for walking around distance and the other eye a bit nearer in for dealing with basic household arms length tasks and computers.

Your statement that "Actually 26 inches is a focal point of about -1.51D diopters" is correct.

Perhaps, I should have made my statement that "I intended to use my left eye for reading after cataract surgery, but the best viewing distance was about 26 inches (that is, off by about 1.00 diopter)" clearer. For reading at 16 in, I needed to have the focal point at -2.5 D, but it was actually at -1.5 D (26 in), that is, it was off by 1.0 D from the intended focal point.

I also agree with the rest of your input to r28706.

The optician suggested requested asking for the iols to be balanced, then adjustments made with spectacles.   My reservation at having the iols different strengths is that might complicate things with spectacles (fixed focus or varifocus), also that over-the-counter readers would not work, if ever needed, eg as a temporary solution if spectacles were damaged or mislaid.

I think that the optician is giving you the wrong advice.

Your first priority is to have good vision without the glasses (at least at some of the distances) if you can.

Unless the difference in the prescriptions is significantly more than 1.0D, there should not be any vision problem in using the glasses.

Even with the over-the-counter readers, there should not be a problem, unless your astigmatism is significant. If the astigmatism is high, you won't be able to use the over-the-counter readers any way.

I will consider having slight difference in prescriptions for the two eyes to be actually an advantage.  As an example, if you have the right eye at -0.25 and the right eye at 0.5, then if you use a prescription reader of 2.0 power, you should be able to see clearly over the 17 to 27 inch range instead of just 17-19 inches for the case of the same prescription.

Any way, you should not give a high priority to the ability to use the over-the-counter readers in making your decision.

Thanks for your message.   The astigmatism reading for the left eye (that has been operated on) is: cyl: -0.75, axis: 10. 6/6+   Does that mean that, overall, the eye is over-corrected by less than the +0.50 sphere ?    It seems best to arrange a pre-op appointment to discuss this. Perhaps best to request the right eye to be set at -0.5, then the left eye subsequently tweaked with laser to be -0.25 ?    

The team explained last time, that although they try to be as accurate as possible, it is not possible to guarantee an exact prescription.  The NHS may not cover the laser treatment, but it is probably worth the cost of having it done privately.

Now that I know your astigmatism value, my advice will change a little bit.

If I am clear on this, your prescription is: spherical correction is +0.5 and astigmatism correction is cyl: -0.75, axis: 10. (6/6+ indicates how good you can see with that eye)

Thus, the equivalent spherical correction is only +0.125, which is equal to the spherical correction plus half of cylinderical correction. It is good to look at the equivalent spherical correction because in USA, many (but not all) opthamologists would have written your prescription as:  spherical correction is -0.25 and astigmatism correction is cyl: +0.75, axis: 100.

Any way, the main point is that your equivalent spherical correction is not that far off from 0. Your main issue is the small amount of astigmatism. LASIK can be used to corrrect that. Limbar Relaxing Incision is another option for correcting your astigmatism, since you don't really need much of a required adjustment in spherical correction. However, none of the two options will make both the corrections zero any way. So, you may want to just the leave the left eye alone if your vision is otherwise good.

Back to the right eye, I will go for miniMonovision like your doctor seems to have suggested by offering mid-distance correction for this eye. if you get a spherical correction of -0.5 for the this eye, you will be able to see better down to about 6 feet. You should probably do that first and depending on the results of that, decide on what to do with the left eye. You may decide that the minor tweaking required at that time is not worth it.

As I am not keen on having a different prescription in each eye, would you  suggest requesting -0.5 in the right eye, then having the left eye adusted with laser of piggy back lens to match the right eye, once that settles ?    (NB I think the surgeons don't work in 0.25 steps).   

I have had cataracts removed from both my eyes and new lenses put in and my far away and middle distance is fine. I can see good. My problem is with my reading. I cannot see close to read ect. I got a pair of 3.25 glasses at a local store and I can see through them but I cannot see through my progressive glasses purchased from my optometrist for around $400.00. They tried several times with different glasses and told me that was all they were willing to do. I told my dr that I needed at least a 3. 0 from the store and he said he didn't want me to have that strong and gave me a 2.5. I cannot see to read or do anything like that and I am stuck with this pair of expensive glasses that don't work. What should I do. I want to be able to read to my grandson and do needlework ect. Please advise. Thankyou.

Your eye condition may require more discussion rather than a simple answer. I will suggest opening a new discussion topic.

The surgeon who did my left eye cataract operation said, at my last appointment, it is possible to use lasek to adjust the prescription and astigmatism (I think this will probably have to be done privately, not on the UK National Health Service, but will ask him - he works in both fields).

The current prescription is +0.5 (or it has also been measured at +0.75), the astigmatism is -0.75 x 172 6/6+ (or it has also been measured at -0.5)

I will have an appointment with him in a week or two and am wondering if there are any particular questions I should ask, and whether it is wise to have this adjustment.  The main reason is to improve the astigmatism (only really noticeable when reading text on the television), and to slightly reduce the overall strength, to improve focus in the mid distance, while maintaining clear full distance vision.       

My main concern is how exact the adjustment will be.  For instance, if he targets 0 and the result is -0.5, perhaps that would be too low for night driving, and it would be a safer option to leave the strength as it is ? 

Your counter spectacles prescription is about what I had guessed.

Just to repeat a little what I stated earlier, if you get a spherical correction of -0.5 for the right eye as part of the cataract surgery, there is a good chance that when using both eyes, you will be able do fine from about 6 feet to long distances and you will not need any glasses for long distance. So, that should be your first step. After that eye becomes stable, then you will be in a much better position to decide the tweaking which will make the most sense.

 

Thanks again.  This sounds a practical and safe decision.

I had a second eye test from a different optician - there the reading for the left eye is Sphere: +0.50   Cyl -0.50   Axis 10     Does this indicate the eye is slightly over-corrected ?

I have been experimenting using my left eye without specs, but it is uncomfortable for every activity except driving (and the dashboard is only just readible with difficulty).  

I realise I will need specs (?varifocals or ?bifocals) for reading, smart phone (17ins) using the laptop and playing the organ (both 20ins) and for teaching,17/48ins, but would like to be able to manage without specs for eg household tasks including cooking, television watching, shopping, art galleries, the inevitable tidying of music and papers, and of course museums and art galleries - rather than only being spec-free for driving and walking out of doors.

 

The equivalent spherical correction with the new eye test is also small at +0.25. The two prescriptions are within the tolerance of the eye tests; i.e. most people will have difficulty in distinguishing the effect on vision of that small a change. Also, most eyes can have more variation than that between different times of the day.

I think that if your opthamologist achieves -0.5 spherical value in the right eye with no significant astigmatism, you will have a good chance of being able to do the various household tasks as well as driving without any glasses and without any tweaking of the eyes.

 

I should add that another advantage of doing the right eye surgery first (before doing anything to the left eye at this stage) is that depending on what you actually achieve in the right eye may determine the best choice for tweaking the 2 eyes. For example, if you actually get -0.25 or 0 in the right eye (even though it was being aimed for -0.5), you may be better off doing nothing to the right eye and tweaking the left eye to -0.75 to -0.5 to achieve the ability of doing the househole tasks as well as driving without glasses.

Thank you.  I am wondering whether to request -0.25 or -0.5 for the righb eye - given there is a margin of error that I think is 0.5 of a diopter ?

The surgeon originally advised against going for the 'mid' option as he said I would then need to wear specs all the time - but perhaps this was a slight over-simplification, and does not factor in the possibility of subtle mini-monovision ? 

My suggestion will be to let the surgeon know that your first choice will be having the equivalent spherical prescription of the right eye at -0.5, but that you will be satisfied in the -0.25 to -0.75 range (which will meet your desires). When he is trying to figure out the IOL prescription, he can keep that in mind.

That looks a safe option, without any risk of being over-corrected (which would be the least good outcome) but not leaving the right eye too different from the left.  

Incidentally, is the left eye in fact over-corrected, taking into consideration the cylindrical readings of -0.5 to -0.75?  

Your spherical and the cylinderical corrections taken together mean that with the first prescription, the different parts of the eye are between -0.25 and +0.5, while with the second prescription, they are between 0 and +0.5. That is not much of a difference. Both readings show that on the average (and over a major part of the eye), the corrections are positive (even though it is only by small amounts). With a monofocal IOL, one has only limited range for good viewing to start with, so even the small positive values take away from that range. That is why even though you can see fine at a distance, you don't see very well at even 12 feet.

With my left eye, the depth of focus for reading music 19 to 20 ins away is only 2 inches, which means it is not always in focus if I move a little - making it rather critical. Will this depth of focus increase if the prescription in the right eye is -0.5 ? 

The prescription in the right eye of -0.5 will by itself not make a difference in the depth of focus at 19-20 inches. Irrespective of what the prescription in the right eye ends up, you should have the music-reading glasses which will provide you best focus for the 2 eyes couple of inches apart.Thus, you can set one for about 18 ins while the other is set for 20 ins, which will probably give you a good range from 17 to 21 ins. It will need an adjustment of about 0.25 diopter on one of the eyes compared to when they are designed to focus at the same point.