Question
QUESTION: My child has been seen by an optometrist and an ophthalmologist both diagnosed astimatism but with different prescriptions.
Optometrist's prescription
Spere Cylinder Axis
OD +1.50 -2.25 007
OS +1.25 -2.00 173
Opthalmologist's prescription
Sphere Cylinder Axis
OD Plano +3.50 100
OS +2.00 +2.50 83
It looks to me like these prescriptions are quite different.
Both claim they have given prescription for far-sightedness. Ophthalmologist states that Optometrist's prescription (tested without dilation) is incorrect and is for near-sightedness. And that without dilation the astigmatism can lead to misleading diagnosis such as near-sightness.
I can even understand different diagnosis. But what I can't understand is each one has a different opinion on whether a particular prescription is for far or near sightedness ? Isn't there a deterministic mapping between prescription and whether it is far or near sighted ?
Can dilation (or lack thereof) cause such a difference in prescription ?
Optometrist converted Ophthalmologist's reading to her system and says it translates to
+3.50 -3.50 x10
+4.50 -2.50 x173
And that her readings were about 3 points less than that, but since it is for a child she cut back prescription to +1.50 -2.25 x7 so it easier for child to start with and in 3 months she will re-test with dilation and likely up the prescription. Starting with a high prescription as recommended by ophthalmologist will be hard for child to even see with those glasses!
That (almost) made sense till the ophthalmologist stated that the optometrist's prescription is in fact not for far-sightness but for near-sightedness!! Her translation of optometrist's prescription is as follows
-0.75 +2.25 97
-0.75 +2 83
And that the negative numbers indicate near-sightedness.
Both professionals specialize in treating children.
Primary questions:
- Are indeed both prescription for far-sightness ? Or is optometrist's for near-sightedness ?
- Is it better to go with dilation based diagnosis (ophthalmologist's) ?
- Is it typical for young children to be given full prescription of finding ? Or typical to cut-back finding to a lower power prescription and then re-test in 3 months and step up slowly towards the full finding ?
-Can dilation (or lack thereof) cause such a difference in prescription ?
- Which one's advice should we follow ?
Thanks a bunch!
ANSWER: This is an excellent question and you provided alot of significant information.
Here's the scoop: Cycloplegic refraction employs the use of pharmaceutical agents such as atropine, tropicamide, or cyclopentolate to paralyze the ciliary muscles of the eye in order to stabilize the refraction of the eye so that a definitive end point may be measured. It is useful in young patients like your 4 year old with highly active accommodation (focusing) in order to ensure complete relaxation of that accommodation so that all the ametropia i.e. farsightedness, nearsightedness, and astigmatism is revealed and uncovered (manifest). Children of that age are often not reliable with their subjective reponses to an eye examination and therefore, the optometrist or ophthalmologist relies heavily on his/her objective findings. Having that said, a rule of thumb is that in a 3 -4 year old, visual acuity of 20/40 or worse should be corrected and if there's a 2 line difference in best visual acuity, amblyopia needs to be considered and treated. If there is a tropia (an eye turn), then treatment with glasses is often the preferred method of treatment, especially if the eyes turn inward and there exists much hyperopia (accommodative esotropia).
Also as a rule, dilated exams do in fact reveal higher amounts of farsightedness (and astigmatism) and the approach to underprescribe the first Rx is reasonable with follow-up exams 3-4 months later. The philosophies of both OD and MD are both acceptable techniques. In my 35 years of experience with kids of that age, I often prescribe 3/4 of the "full" prescription and sometimes place the balance in a progressive (no line) bifocal to aid in the child's accommodation, because quite frankly, most of what a 4 year old focuses on is at close range. I cannot comment intelligently as to why each of your doctors prescribes as they do but would venture a guess that if you sought the opinion of 5 other doctors, you may very well get five different prescriptions: WHICH IS WHY THE EYECARE PROFESSION IS CONSIDERED TO BE AN ART OF PRACTICE, NOT AN EXACT SCIENCE I HOPE THIS HELPS YOU IN SOME WAY. DR. KEN
NOTE: In my private clinical Practice , I take the results of the "wet" (cycloplegic) refraction with drops and the results of the total "dry" refraction without drops, and split the difference, that is take the midway point as the child's first Rx. In this way , I am sure to not "overplus" the child and fog his distance vision. This technique has worked well for me over the past three decades
---------- FOLLOW-UP ----------
QUESTION: Thanks much for your response Dr Berger.
Could you also comment on whether the prescriptions given by the doctors are for far-sightness or near-sightedness ?
Does the negative number (for Sphere) indeed indicate near-sightedness ?
The optometrist's prescription is as follows
Spere Cylinder Axis
OD +1.50 -2.25 007
OS +1.25 -2.00 173
The ophthalmologist says optometrist's prescription is for near-sightedness (because sphere becomes negative when translated to ophthalmologist's system). Optometrist claims her prescription is for far-sightedness. This is the biggest disconnect I am trying to understand. If both were prescribing for far-sightedness with one being a cut-back version I could understand that at least.
If indeed the ophthalmologist's prescription is for far-sightedness, and the optometrist's is for near-sightedness, then is it common that a cut-back prescription becomes near-sighted though the original reading was far-sighted ? That seems strange.
I do understand that different doctors can choose a different treatment approach. But how can two professionals look at the same Prescription and one say it is for far-sightedness and one say it is for near-sightedness ? Isnt there a deterministic way to interpret the same Prescription ?
As a side question- how does an optician know in which system the prescription was written in ? Seems like for prescriptions with astigmatism the meaning of the two systems are quite different.
Thanks much.
Answer
The best way to answer this question is that ophthalmogists are taught to write prescriptions in Plus cylinder form whereas Optometric Physicians are taught to write presriptions in minus cylinder form. They are both correct and can easily be transposed to the other form. For example; an Rx of +1.00=-2.00 x 90 is the EXACT SAME presription as -1.00=+2.00x180. ALL Opticians, optometrists, and ophthalmologits know this and how to transpose one to the other. The prescription that you listed above is actually farsighted with astigmatism that is greater then the farsightedness and is often referred to as "mixed" astigmatism.
An Rx of say +4.00 = -1.00 x 90 is an Rx to treat farsighted astigmatism
An Rx of say -4.00 = -1.00 x 90 is an Rx to treat nearsighted astigmatism and..
An Rx of say +1.00 = -1.50 x 90 is an Rx to treat mixed astigmatism
