Near vision testing on the wards. Iphone or Rosenbaum?

[alesdu1]

I'm a second year medical student beginning to do PEs on the wards. My school gave us all Rosenbaum Pocket Eye Charts to assess visual acuity. Most of the patients I actually perform the test on however (except the really demented ones) are able to remember the short sequence of 5 or 6 numbers, which makes me doubt what I should even put for the second eye's visual acuity.

An app has emerged on the App Store for "pocket" vision testing. It requires that one hold the iphone approximately 4 ft away and have the patient read it in a classic Snellen-like scale. On the bottom is a "randomizer" button; when pressed, all the letters on the chart change, thus eliminating the concern that patients are just reading back to you the numbers on the Rosenbaum #s from memory.

I understand that near vision testing is kind of an imprecise science and the Rosenbaum pocket chart isn't exactly a validated method of assessing visual acuity. But, it seems to be the most commonly performed way of doing the test at the bedside. I guess what I'm wondering is, could I use something as unorthodox as a Snellen scale on an iphone to check for visual acuity at the bedside? Thoughts? Similarly, do ophthalmologists use "randomizers" when testing in the clinic?

Thanks so much!

Also- most ophtho offices still make use of the Snellen or tumbling E chart, yet the Logmar scale has been consistently shown to be a more superior method of assessing visual acuity (and certainly for performing statistical analysis) Why isn't it used more widely in clinical practice?

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[jefguth]

I'm a second year medical student beginning to do PEs on the wards. My school gave us all Rosenbaum Pocket Eye Charts to assess visual acuity. Most of the patients I actually perform the test on however (except the really demented ones) are able to remember the short sequence of 5 or 6 numbers, which makes me doubt what I should even put for the second eye's visual acuity.

An app has emerged on the App Store for "pocket" vision testing. It requires that one hold the iphone approximately 4 ft away and have the patient read it in a classic Snellen-like scale. On the bottom is a "randomizer" button; when pressed, all the letters on the chart change, thus eliminating the concern that patients are just reading back to you the numbers on the Rosenbaum #s from memory.

I understand that near vision testing is kind of an imprecise science and the Rosenbaum pocket chart isn't exactly a validated method of assessing visual acuity. But, it seems to be the most commonly performed way of doing the test at the bedside. I guess what I'm wondering is, could I use something as unorthodox as a Snellen scale on an iphone to check for visual acuity at the bedside? Thoughts? Similarly, do ophthalmologists use "randomizers" when testing in the clinic?

Thanks so much!

Also- most ophtho offices still make use of the Snellen or tumbling E chart, yet the Logmar scale has been consistently shown to be a more superior method of assessing visual acuity (and certainly for performing statistical analysis) Why isn't it used more widely in clinical practice?

The Rosenbaum chart should be just fine, I'm not sure what yours looks like, but mine has plenty of letters such that memorization is not a factor. If that is a problem, you can always ask the pt to read the letters in reverse order. Frankly I don't like paying around with my iphone when I'm around potentially unclean patients.

Logmar is simply a way of annotating acuity findings, it can be applied to any chart used, and I think the Rosenbaum actually has a logmar scale on it. Snellen notation is nice b/c 1)everyone is familiar with it, and 2)it tells you at what distance the patient was able to read a given line.

 

[PBEA]

I'm a second year medical student beginning to do PEs on the wards. My school gave us all Rosenbaum Pocket Eye Charts to assess visual acuity. Most of the patients I actually perform the test on however (except the really demented ones) are able to remember the short sequence of 5 or 6 numbers, which makes me doubt what I should even put for the second eye's visual acuity.

An app has emerged on the App Store for "pocket" vision testing. It requires that one hold the iphone approximately 4 ft away and have the patient read it in a classic Snellen-like scale. On the bottom is a "randomizer" button; when pressed, all the letters on the chart change, thus eliminating the concern that patients are just reading back to you the numbers on the Rosenbaum #s from memory.

I understand that near vision testing is kind of an imprecise science and the Rosenbaum pocket chart isn't exactly a validated method of assessing visual acuity. But, it seems to be the most commonly performed way of doing the test at the bedside. I guess what I'm wondering is, could I use something as unorthodox as a Snellen scale on an iphone to check for visual acuity at the bedside? Thoughts? Similarly, do ophthalmologists use "randomizers" when testing in the clinic?

Thanks so much!

Also- most ophtho offices still make use of the Snellen or tumbling E chart, yet the Logmar scale has been consistently shown to be a more superior method of assessing visual acuity (and certainly for performing statistical analysis) Why isn't it used more widely in clinical practice?

as you said, "I understand that near vision testing is kind of an imprecise science", and is very true. It is innaccurate, and you may as well have a near chart that says good, medium, or bad.....seriously. As a result, the near chart used really doesn't matter.

some snellen charts list LOGMAR equiv, and as jefguth pointed out, LOGMAR can technically be applied to ANY chart.

 

[MstaKing10]

I've downloaded the app and it's not that great. The contrast, lighting, and glare from the screen all make it MORE imprecise in my opinion. Near testing done properly is actually quite precise. A near card with good lighting and appropriate refractive correction (ie. reading glasses for presbyopes) works great and can really give you a good sense of the patients vision. My two cents...

 

[PBEA]

in many cases, reading "20/20" on a near chart is misleading, regardless of the method used. It is only a rough indicator of how the eyes and vision are doing.

 

[KHE]

in many cases, reading "20/20" on a near chart is misleading, regardless of the method used. It is only a rough indicator of how the eyes and vision are doing.

I use the iPhone app when seeing some nursing home patients and I have found it to be accurate and easy. In most of these cases, you're not interested in if the vision is 20/70 or 20/80, you're interested in if the vision is catastrophically off and for these cases, iPhone is more than adequate.

 

[Visionary]

Also- most ophtho offices still make use of the Snellen or tumbling E chart, yet the Logmar scale has been consistently shown to be a more superior method of assessing visual acuity (and certainly for performing statistical analysis) Why isn't it used more widely in clinical practice?

logMAR, as has been stated, is actually just a metric. It stands for the log of the minimum angle of resolution, referring to visual angle. You can convert any measure (Snellen feet, Snellen meters, or Decimal--the latter are more common outside the US) to logMAR and vice versa.

The "superior method" you refer to is actually the ETDRS (Early Treatment Diabetic Retinopathy Study) chart. Adapted from a chart designed in the 1970s by Ian Bailey and Jan Lovie, the ETDRS chart set a new standard for visual acuity measurement, particularly for clinical trials. Though represented in logMAR (often with Snellen conversion), this chart is actually preferred because of its uniformity, in numbers of letters (5 per line), spacing of letters, steps in visual angle from line to line (log steps, where every 3 lines represents a doubling of visual angle), and contrast (a backlit screen is used).

Most practices still rely on Snellen, however, because most ETDRS charts are rather unwieldy (though there have been computerized adaptations).

That all being said, I also agree that bedside measurement with a handheld Rosenbaum is fine. You're looking for gross deficits, not doing a clinical trial!

 

[alesdu1]

Ah, very interesting. Thank you for that. I have been helping write up some papers over the last few months and have had to convert Snellen to logmar for statistical purposes and that is when I came across the ETDRS.

logMAR, as has been stated, is actually just a metric. It stands for the log of the minimum angle of resolution, referring to visual angle. You can convert any measure (Snellen feet, Snellen meters, or Decimal--the latter are more common outside the US) to logMAR and vice versa.

The "superior method" you refer to is actually the ETDRS (Early Treatment Diabetic Retinopathy Study) chart. Adapted from a chart designed in the 1970s by Ian Bailey and Jan Lovie, the ETDRS chart set a new standard for visual acuity measurement, particularly for clinical trials. Though represented in logMAR (often with Snellen conversion), this chart is actually preferred because of its uniformity, in numbers of letters (5 per line), spacing of letters, steps in visual angle from line to line (log steps, where every 3 lines represents a doubling of visual angle), and contrast (a backlit screen is used).

Most practices still rely on Snellen, however, because most ETDRS charts are rather unwieldy (though there have been computerized adaptations).

That all being said, I also agree that bedside measurement with a handheld Rosenbaum is fine. You're looking for gross deficits, not doing a clinical trial!

 

[Lux Lucis]

The only reason for LogMAR existence is for statistical purposes. You cannot statistically average Snellen acuities across a group of patients without first converting them to LogMAR values. Nobody measures visual acuities in LogMAR units in the real world.
See Jack Holladay's article published in Journal of Refractive Surgery in July/August 1997 pp 388-391 if interested in further explanations.

 

[Visionary]

The only reason for LogMAR existence is for statistical purposes. You cannot statistically average Snellen acuities across a group of patients without first converting them to LogMAR values. Nobody measures visual acuities in LogMAR units in the real world.
See Jack Holladay's article published in Journal of Refractive Surgery in July/August 1997 pp 388-391 if interested in further explanations.

Holladay also presented a description in an editorial for the 2004 Journal of Cataract & Refractive Surgery (Vol 30, pp. 287-90), for those who are interested.

Lux is correct that the use of actual logMAR units is mainly for research and is not practical in a clinic situation (though, it is possible, if you have a chart that provides the logMAR conversion).

It's much easier to explain your patient's visual acuity to them with Snellen or Metric (e.g., to describe 20/200, you would say "what someone with 'normal' vision can see from 200 feet away, you have to be 20 feet away to see").

Note that there are those who argue that simply converting Snellen acuities obtained from a non-ETDRS chart to logMAR for statistical purposes is not valid. This is because the letters on such charts are not appropriately standardized, so the visual acuity sampling is biased (see my description in an earlier post).

 

[azzarah]

For your purposes, the free chart that the school gave you should be more than adequate. I sometimes even use a photocopy of the chart in trauma cases. Trust me, you don't want to put a VRE/MRSA/blood covered iphone back into your pockets....
When checking vision, just make sure the room is well-lit or hold a flashlight over the card and also make sure they wear their reading glasses if they are over 40 and push them to keep going to the next line. Almost all patients will point out to you if they can't see the 20/20 line and just have the letters memorized.

 

[Visionary]

Trust me, you don't want to put a VRE/MRSA/blood covered iphone back into your pockets....

Ugh, that's nasty.