Improving distance to blur but not reducing on Snellen

Hello to all group members, I am here for my 6 y-o daughter who has high cylinder Diopter and low spherical.
Lately I have seen her improve her distance to blur from 60 cms to 67 cms, but I do not see any improvement on the Snellen Chart. She is 20/40 constantly.
Just want to know if I am missing out on something…? Would be grateful if anyone could offer their insights…!

I would say a bit of patience :smiley: it is common for measurements to be ahead of each other. If she shows improvement on even one measurement, then you should be on the right track! I think that eventually the improvement will translate in other ways.
High cylinder can make things tricky too. There are lines I can’t read on the Snellen even though they don’t seem blurry at all, so maybe that’s why Snellen improves slower for her.

1 Like

Perfectly normal, I would say. Keep up with the good work, she’ll thank you later.

Both cm measurement and Snellen reading translate to diopters in glasses at the end of the day.

Cm:
https://endmyopia.org/focal-calculator/calc.html
47 to 53cm = -2.00D
53 to 61.5cm = -1.75D
61.5 to 72.8cm = -1.50D
72.8 to 88.9cm = -1.25D
88.9 to 114cm = -1.00D

Above that – if you are using a screen – you are simply get ridiculously far from it. I guess it is the same with a book and printed text.
So your daughter started from the upper end of -1.75D (almost -1.5D already).
To experience a real 0.25D improvement she should get to around 70cms - the upper end of -1.5D…

Snellen:
I don’t know what Snellen chart you have, but I’d assume you have the 20/___ values next to the lines.
Mine is the E - FP- TOZ one…
E – this is 20/200 = -2.50D
(a full diopter missing!)
FP – 20/100 = -1.50D
(half a diopter missing!)
TOZ – 20/70 = -1.25D
LPED – 20/50 = -1.00D
Based on cms she is below -2.00D already, so of course she will see the 20/200 line perfectly, but she will struggle with seeing the 20/100 with the same clarity as that is 1 full(!) diopter less.

Hope it helps.

Edit:
Note: As a low myop I measure Snellen without corrections, too. Hence the focus on the missing lines

1 Like

That is about .25D of improvement and may not yet translate to adding a line on the Snellen. It is also possible that she has memorised the 20/40, making this easier for her to read. You could ask her if she can read any of the letters on the 20/30 line. There is quite a jump in letter size between the two, as there is no 20/35 line. To get over this problem, you could let her take a step or two forward until she can read the 20/30, measure this distance, and see if she can move back a little as she improves more. This might be more fun for her as well.
Great to hear that there is some improvement. :grinning:

2 Likes

With her glasses she can read PECFD (20/40) - difficulty in reading the P and F
and without glsses LPED (20/50).
I am using a book to take her distance to blur…

What glasses does she wear?
The difference between reading PECFD with difficulty and LPED easily is less than 0.25D…

The good news: she is definitely not overcorrected
The slightly bad news: most probably she never gets perfectly clear vision and may get adapted to blur long term (but hey you’re working on it so there will never be “long term” with her glasses…)

Having said that, with kids who never wore glasses for long periods of close-up work before, this could be ok and still improve gradually - as your daughter does - if good habits are introduced and maintained

IMHO, but then I’m just a fellow EM reader / believer…

1 Like