First, I would suggest that for purposes of your study, you compare binocular acuity at both ages. Second, given that there is no way for a child to do recognition acuity testing at 1 year of age, there is no way to avoid comparing different tests modalities when comparing these two age groups. That said, my experience has been that for a child with normal visual functioning, their acuity should improve, as the result of the visual maturation process, as they get older. So, I would expect better recognition acuity at 5 years of age, they resolution acuity at one year of age. I hope this helps.

You may look at the correlations between your results or you can split your group into better and worse performers by Teller test results and see if it predicts the performance in the age of 5. I assume that you can get some reasonable results.

Concerning another design to compare personal development/maturation you can use an electrophysiological test (VEP).

In this thought, you forget that visual function in that age (from 1 to 6 yrs of age) is "under construction" and may vary in speed and completition, developing of receptive fields and their specializzation in spatial frequencies or other functions deos not allow to compare the results even if recorded with same method. In my opinion each test is useful to assess visual, retinal and brain function. Moreover infant compliance may vary also with the maximum of technologic system, so that this discussion dose not reflect reality.

Dear Mark, Jan and Enzo,

Thank you so much for the comments. I agree with Mark that we should compare binocular acuities at both ages but was wondering how useful will it be in determining conclusion from the findings. Also, I agree that their acuity will improve but might not be to the adult level. Will the the binocular acuity make any sense for someone who has amblyopia or any other visual disorders? Can we call the binocular acuity in children the acuity of the better eye and compare the finding from the better eye while child is a bit older , which might make the results more comparable? I like the idea from Jan of correlating the findings or split the findings according to normal and abnormal performance and see whether it predicts performance at 5 years. However, we haven't included VEP in our protocol this time but might use for our future research. I agree with Enzo but ,in the current situation while we have limited resources we need to put together the findings in the way we can so that they can give some reasonable explanation how visual acuity develops in children and what might be the effects of certain systemic and metabolic conditions on children's visual development.

I hope to hearing from you more.

Kindest regards,

Nabin

Nabin

I believe the information will be useful, because viewing binocularly is the normal state of function for most individuals.

I am not sure what you are hoping to determine by your research when you mention amblyopia and/or other visual disorders. Are you testing a random or selected group of children.

We know that visual acuity in general improves as the child matures. That research has already been done and proven. Are you now trying to predict how much vision improves over time for children with different systemic and metabolic conditions? If yes, and these conditions affect cognition, then you have another variable to deal with when testing the older children; their ability to understand and perform the test.

As you have seen in your career, even people with very poor vision in one eye, often have better binocular acuity then monocular acuity. For this reason, I do not think you can assume the acuity in the better eye is equal to the best binocular acuity.

You could certainly attempt monocular Teller acuity on the young children. If you do this, for purposes of your study, I would suggest that you test the binocular acuity first in both age groups. This is because with 1 year olds, you often only get one chance at acuity testing and binocular testing is going to give you the best response to compare to over time.

I hope this helps.

Regards,

Mark

Nabin, as you seem to be aware, comparing results that were obtained with different tests is a bit like comparing apples and oranges. But, if you have normative data for each of the methods involved, then you can express all your data in units *relative to mean normal for that test*, and then proceed with your comparisons. (E.g., for the Teller acuity cards, age-dependent normative data are available in the literature; for the other tests possibly as well.)

HTH, Joost

Hi Mark, Thank you so much for those wonderful comments. That makes sense that binocular acuity is the most natural and practical visual status. Yes, we are trying to see if there is any influence of certain metabolic and systemic conditions on the rate of visual development. We will have certain at risk populations of metabolic conditions ( but all of them might not have suffered from the condition), and we will be blinded. This metabolic condition might affect the cognition of the child and we will also have that variable measured. At this point comparing binocular acuities looks the best option but as mentioned earlier, we will not be able to say who developed amblyopia or any other visual disorders based on the acuity measurements and it might look there is not much of change in VA during those years as better vision in one eye will mostly contribute for the binocular acuity, please advise me if I am wrong. Subtle changes in VA during that period might not be detected.

Hi Joost, Thank you so much for providing a new method of making the variables more comparable to one another which I think is a genuine way of explaining the values. That will be one way to look at our results after we complete collecting data.

The only thing I am a little bit worried about is, we will mostly have binocular acuities at younger age (1year) and monocular as well as binocular at school age,.Will it be like, comparing binocular acuities might not reveal subtle changes during that duration or it might reveal the same as monocular acuities?

Thank you everyone for actively taking part in this discussion.

I would love to hearing more regarding this matter.

Kindest Regards,

Nabin

Nabin

Are you anticipating that these metabolic conditions may result in reduced vision? If yes, the reduced vision would be binocular, not monocular, as in amblyopia. The only way I could see a metabolic condition causing amblyopia, is if that condition would result in asymmetric refractive error or strabismus, both of which would seem unlikely to occur as the result of a metabolic condition.

As for detecting subtle changes in vision, my experience is that every child with normal visual develop will show improved measured acuity as they mature. If the acuity is not getting better, from 1 year of age to 5 years of age, it is getting worse. Research has shown that we learn how to see in the first 5+ years of life. This table of visual acuity norms for Teller Cards (Scheiman) illustrates that point.

Age Binocular VA Monocular VA

1 mo. 20/400-20/1200 20/400-20/1600

4 mo. 20/80-20/300 20/100-20/400

12 mo. 20/50-20/200 20/80-20/300

18 mo. 20/40-20/100 20/50-20/150

24 mo. 20/30-20/80 20/40-20/100

30 mo. 20/20-20/50 20/20-20/50

I am not sure how you are defining subtle changes in visual acuity over the time you are testing. That said, as noted in the table above, you should see improvement in visual acuity from 1 to 5 years of age, with near normal acuity being measurable binocularly at 5 years of age, if the child is able to intellectually understand the acuity test being done at 5 years of age.

Finally, I think it best to compare binocular acuities at both ages because if you don't, you will add another variable to you study. You cannot prevent comparing resolution versus recognition acuity between your two age groups. But you can avoid comparing monocular to binocular acuity.

I hope this helps and makes sense.

Regards,

Mark

Hi Nabin,

Please remember that visual function is so much more than visual acuity. If you are exploring subtle changes due to systemic or metabolic conditions, contrast sensitivity would probably be a more sensitive (!) measure than acuity. You can do this in one year olds with affordable preferential looking tests as well.

Best Regards,

Arnulf

Hi Mark, I am very glad to hearing from you. The data ranges of monocular and binocular visual acuities look very useful and informative. Thank you so much. Well, I am expecting not that much VA difference in those children with metabolic conditions in comparison to normal kids but the maturity of VA might take longer in these kind of children than their normally developing peers. There might be asymmetric development of two eyes in these children as a result of this metabolic condition as a result they might have high prevalence of amblyopia or refractive error (that is one of our hypothesis). At this stage, as mentioned earlier comparing binocular acuities looks to be the best option and we will definitely consider comparing binocular acuity on both ages. I agree with all of the things you say which makes a lot of sense to me. Thank you very much.

Hi Arnulf, we agree that contrast sensitivity might prove to be a more sensitive indicator for visual function to see subtle changes but at this stage we are a little bit far away to consider that option, however, we have a more sensitive indicator ( Global motion perception) test for both the ages. This might prove to be a sensitive indicator. We need to see once we finish collecting data which will still take few more years.

Thank you very much.

Regards,

Nabin

Hi All, on the other note, I also want to see the relationship of Global motion perception from 1 year (objective, which doesn't have any normative data in the literature) to 5 years( behavioural, subjective response) and see whether there is any relationship with the development of psychological parameters ( Cognitive skills, Gross motor, Fine motor) which are also assessed with 2 different tests at 2 different years.

In short, I want to see whether the development of gross motor, fine motor and cognitive skills in children are related to the change in Global motion perception, change in Visual acuity and stereopsis. Any ideas?

Hi Nabin. Guess you are familiar with the work from Atkinson, Braddick and Watam-Bell. If not, I would recommend Janette Atkinson's book "The developing visual brain" as a starting-point. Another book that comes to mind is "The visual brain in action" by Milner & Goodale.