Best settings for watching TV

[TillyMack]

Hello, I'm considering near-intermittent bias mini-monovision with targets of -2.0D and -1.0D.  The cataract surgery for my first eye has been completed with a final result of -2.0D.  Would there be a suggested target for the second eye for the purpose of watching TV in a room measuring 10-20'?
Many thanks!

[NightHawkGuy]

Depends on the size of the TV screen too.
I view my 65" OLED TV from about 8feet away and get the sharpest most details view of HD/4K video with my eyes corrected for best distance vision.

[TillyMack]

Good point!  My TV screen is a relatively small one at today's standards (32").

[Ron_AKA]

If you look at Figure 1 at this link below you will find the visual acuity vs distance for a few different amounts of myopia. 20/32 is often considered the limit of good vision. As you can see the curve for -1.0 D intersects this acuity at about 3 meters or 10 feet. At 20 feet it would drop to about 20/40, the same as for longer distances. This is the limit in most jurisdictions for driving without eyeglass correction. So the short answer is that -1.0 would be marginally ok for TV viewing at 10 feet, and not quite as good at 20 feet. It depends on your requirement for sharpness of your TV image.

https://www.semanticscholar.org/paper/Optimal-amount-of-anisometropia-for-pseudophakic-Hayashi-Yoshida/dd8837a9151a536759f195a18d4fa94a0fbf0f90/figure/1

My experience with TV at about 12 feet is that it is very sharp with my -0.4 D eye, and a little fuzzy with my -1.6 D eye. It is kind of like watching standard definition vs high definition. At 20' you may something similar to standard definition if you have a HD TV.

[Ron_AKA]

Oh, and as you can see from the curve for the distance eye the setting for best vision at 10-20 feet would be plano or 0.0 D. It should give vision of 20/20 or better.

[John C Hagan III, MD, FACS, FAAO]

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[TillyMack]

Dr. Hagan, Thank you so much for addressing my concerns!  It is helpful to know that if I decide to choose mini-monovision with near-intermediate bias, I should choose at least -1.0 D.  Otherwise I would choose both eyes the same for the benefits of that configuration.

[TillyMack]

Thanks RonAKA, Is this information referring to my target points of -2.0 and -1.0?

[Ron_AKA]

These are curves for monofocal lenses with no offset and three myopic offsets. If you look at the Figure 1 graphs in the link I gave you above, it shows the visual acuity (snellen) vs distance (meters) for a -1.0 D, -1.5 D, and -2.0 D outcome. If you are at -2.0 D that curve with the square markers represents your current vision. You should see well (20/32) from a bit less than a foot to 2.5 feet. The -1.0 D curve with the round markers represents what you could expect from the second eye if the target is -1.0 D. perhaps about 15" to 10 feet. It does not drop off a cliff after that and you should still have 2o/40 at 20 feet and further. That is on the limit of being legal to drive.

[John C Hagan III, MD, FACS, FAAO]

As for TV and people that don't want to wear glasses, and who have not been left hyperopic post op and have an otherwise normal eye, most problems can be helped by moving closer, or further away, or buying a bigger TV which is cheaper than buying glasses

[TillyMack]

Good point!

[TillyMack]

Thanks Ron for explaining Figure 1.  I'll consider that if my refraction permits.  

[John C Hagan III, MD, FACS, FAAO]

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