visual acuity with nystagmus

My four year old daughter was diagnosed with nystagmus at six weeks old.  I have been told that her vision is 6/18 with both eyes open, This means nothing to me, can anyone tell me if she will be registered as partially sighted.  I dont really know where to go from here as her consultant is no help.  She says that her vision is likely to remain stable at 6/36 each eye what does this mean and can my child lead a reasonably normal life

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it is normal for patients with nystagmus to have reduced acuity...they have retinal development problems as well as eye movement problems.

i have no idea how the standards work where you are.  i can only tell you how they work where i live (Texas, U.S.A.).

6/18 is a standard way of referring to vision.  the "6" means that she was tested at 6 meters.  the "18" on bottom is a way of measuring the smallest letter size she could correctly identify (or picture size or number size or target of some kind: in infants this can be done using gratings called forced preferential looking cards or even just estimated based on known Rx).  its an angular measurement of letter size.  this will likely confuse you, but here goes: 6/18 acuity means the smallest letter she could possibly read subtends 5 seconds of arc at 18 meters.  dont worry too much about it...like i said its a way to measure letter (target) size.  we just measure letter size in angles, not height.  its more accurate that way b/c the distance from the target is less meaningful.  there are 360 degrees in a circle, and each degree has 60 "seconds" in it...hence the "5 seconds" of arc (it has nothing to do with time).

so vision is designated as a fraction.  test distance (6 meters) over angular letter size.  the bigger the bottom number, the worse the vision is.  "normal" vision would be 6/6.  AWESOME better-than-average vision would be 6/3.  6/18 is blurrier than average vision.  6/36 is even blurrier (meaning the letter would have to be even larger for her to identify/see it).

in the U.S. 20/70 or worse is considered "impared" or "legally blind".  that would equate to 6/21 (which i realize is a non-standard acuity/letter size in Europe).  

so *RIGHT NOW* your daughter would NOT be referred to as "impared" if we are going by U.S. standards.  she's 6/18, which is about 20/60 (just under the majic 20/70 number).  but if she were to "stabilize at" 6/36 later, that would, in fact be legally "blind" or "impared" in the U.S. (6/36 = 20/120).

YES she can lead a very normal life if her acuity is 6/18 or even 6/36.  she may or may not be legal to DRIVE depending on the restrictions of the area you live in.  but if she were "stable" at 6/36 as you were told...that is not bad at all.  nor is that "blind".  its just blurrier than normal.  she cant be in the military or have certain jobs like pilot or police officer, but i personally would not consider that to be truly impared or debilitated.  she will most likely have a normal or near-normal life, at least visually.  she can and will learn to read (possibly with special books or devices, but maybe not), can recognize faces and places, can see birds and stars and most of the things you can see.  she will not be walking around in blackness...she will only have blurrier vision than you do.

hope this helps some.