Differentials are giving eye pain

Hi , my son 10yrs old has a current prescription of right eye -5.0 /-0.5 cly and left eye -4.0 / -0.5 cyl , tested one month back with a proper dilation / retina and squint test .I never got new glasses for him as I felt he got over prescribed. The reason for my assumption was he was claiming that he is was good with his old glasses prescribed as right eye -4.5 / no cyl and left eye -3.50/-0.75 cyl with no blur challenge at all. Considering that I discarded the current prescription.(did I do a mistake?)I have got him differentials as per his ergonomic close up distance ,but not by his cm measurements ,and from his arm/ neck comfortable close up distance which was approx 40 cm (2.5 diopter). This reduction I did on his previous prescription and reduced 2.5 diopter on each eye making right eye -1.5 and left eye -1 . But for the cyl I don’t know if I did a mistake . I took from the current prescription which was -0.5 cyl for both eyes and just reduced by - 0.25 cyl and keeping the axial same as per the prescription for both the eyes. So the differentials are now right -1.5/-0.25(130 degrees) and left eye -1.0/-0.25(40 degrees). This he is trying from past 2 days for his close up which is 3-4 hrs of computer and 3-4 hrs of school home work. He complains of eye pain for this.I haven’t got him any normalised yet and he uses his old glasses without any complain.

Did I do something wrong in calculating his differential?I am scared because of the eye pain he is having.

He has been getting some good outdoor time in the morning and day may be around 2 hrs/per day and practising active focus without glasses indoors( 1 hr per day) from past 1 month.I have been taking eye measurements in cm which is roughly 46 cm both , right 40 cm and left 43 cm.

I have 20/20 vison and none in my family are myopic. I try to validate my sons vison claims thorough lot of trials.

Any insight on this would be a real help

If his prescription is - 5 and - 4 sph then those differentials are too low. His eye pain COULD be well explained by strain in that case. This happened to me as well when reducing differentials too much. After a few hours strain eye pain and headache develop on dominant eye side.
Is it just his dominant eye or both?

Anyhow most likely increasing his differentials should help. Cant tell you exact diopters but for me around 1.75D less than full prescription. And better to reduce less aggressively then when he is used to one reduction with no pain, reduce again

See also

Yes he gets a pain in his left (-4.0) more than the right(-5.0).I will try to get him tested again from an opto for his close up and get the differential. This will be more proof.

Just one more thing, do u think I need to work on his cyl corrections( which is currently -0.5 in both eye with different axis) or leave it for now.?

Thank you so much for the insight

Hi! Welcome to the forum!

And maybe cross check against your own measurements as well.

How does he practice active focus? Could this be straining his eyes?

Maybe not an insight just a few questions from my side

Is he aware of his “number” i.e. prescription? Is he stressed out about his vision?

What screen is he using for his school work?

Is the screen placed to one side? How is the lighting in the room? From which direction?

Outdoor time - always a good idea! What does he do during his outdoor time?

How has his journey been so far? Is he onboard with the whole thing? How does he communicate when asked questions like is this better? Or that is better? with the test lens exam?


I did that but I am really confused- his close up measurements are 43 cm both, rt 40 cm and lt 43 cm currently. But with the snellen it’s at 10 ft , even 20/100 is blurred ( edge of blur).Both don’t match up to the same diopter. And prescription is matching to the snellen chat . Which one should I count for the differential?

He does with out glasses. In daylight for distance to look at sign board texts and with snellen’s for indoor. I am not sure of eye strain because he doesn’t complain of that after doing it, which he is doing with the differential.

He is too young to be stressed out. I am rather stressed on his rapidly progressing myopia. I suppose that was the question and I answered.

Strictly laptop at a distance of 40-50 cm which is his egonomic distance.

Lighting is not the best but not the worst either . He sits near a window ( Which is not strong sunlight kind of shade)facing his back which means light falls on the computer and he should be having good vison.

In the morning it’s just the distance vision from the terrace and some active focus, with little workouts like jogging hopping and stuff for about an hr. Before evening we go for an walk for an hr which is purely distance vision

I am not sure if I am going in right direction as I am depending on his description which sometimes contradicts. Cannot blame him as he is not that matured to understand the rules and principles of EM by his own. I think it will take time for him and me . But as I said I just need some insight if I am doing right

I read some of your other posts. If it were my son I would try the following for distance: -4D SPH in both eyes (no cylinder) and for near work -2D SPH no cylinder.

To me it sounds like his eyes are pretty close to one another in terms of myopia, the astigmatism correction is probably doing him more harm than good. I would guess that he’ll feel better with the same correction in front of each eye, and life will be a lot easier going forward if you reduce the prescription complexity now.

I think the current differentials don’t have enough correction, and having different lenses in front of each eyes is probably bothersome, especially with the astigmatism correction.

My guess is that he would probably see quite well at distance with -4D glasses and get used to having a little bit of focus challenge and also get used to having the same lens in front of each eye. The -2D differentials should make it easy to see the books or computer screens and at least won’t be as bad as wearing his distance glasses for close up. So they shouldn’t make things worse. After a few months you could try differentials of -1.75, and if he’s seeing clearly at distance with the minus -4D, try -3.75D in six months or so.

It sounds like he’s basically at -4.25 or -4.5D of myopia, his eyes will get used to whatever kind of astigmatism correction are in front of them and whichever different lenses are in front of each eye and over time that will just lead to more astigmatism and more difference between eyes.

So I think you might as well keep it very simple at the start. -4 SPH for distance, -2 SPH for near, and see if he can tolerate that. I think that will be more comfortable for him than the current adjustment based on his current prescription that leads to very different lenses in front of each of his eyes.

I hope that makes sense to you, I feel like it’s worth a try and would save you a lot of frustration with trying to deal with ever-changing cylinder and axis and different prescriptions for each eye. Complicating things with astigmatism correction and minute differences in lenses for each eye doesn’t really benefit him.

I would also try to find some more outdoor activities for him, maybe he can try soccer or tennis or walking around the park or anything that gets him spending a few more hours a day out in the sun.

Your eyes are fine, nobody in the family has myopia; there’s no reason to think there’s anything wrong with your son’s eyes other than that he’s been spending too much time indoors doing near-work on computers and books and that he got prescribed glasses.

Good luck!


Nice of you to help in such detail, but for what it’s worth, i don’t agree with simply putting the same lens in front of each eye if the eyes are different. I think, at least in my experience, it’s much more important that each eye gets the same acuity from the glasses else one eye will get strained more and get left behind.

It is not a coincidence that in his famous prescription complexity blog post jake recommends dealing with equalization LAST

As currently 2.5d reduction is giving him eye pain for differential , I will get him tried for 2 or 1.75 which ever he feels better. And I am planning to add .25 more to spherical for his -0.5 astigmatism .
will update on the latest and how he feels

one more question: did he have cyl in his first ever prescription or was it added later? If later, it COULD just be lens induced which means you can probably do as you say and replace with sph eq

There is some personal preference with such decisions of course. But in general, I’d rather have equal lenses in the correction and have the natural difference in acuity (natural difference can easily be up to 0.5D) than correcting to same acuity and kick off a lens induced process of an always increasing gap…

With Endmyopia the general recommendation is for the parents to improve their eyesight first and then with that understanding apply it to their children. You are lucky with the 20/20, so to compensate for own experience here are my thoughts:

Kids’ eyes can change easier than adults’. Both ways. If they get absolutely overprescribed by an opto based on a measurement on a “bad eye day” or just a dark opto room, they will get used to that too much prescription relatively easily. Similarly, they tend to tolerate bigger drops because they often still have memory on using their eyes to adjust far and near. Though this is most typically true with the first pair of glasses or up to 2 or 3 diopters. But it is possible with any corrections

With cyl up to -1D especially if first prescription (cyl not worn for years yet), it is preferable not to add cyl.
It is because the cyl correction gives a rugby ball like distortion to the images. So a circle becomes an oval along the axis and then the brain corrects it back to a circle. It means that the difference between natural image and the full corrected image with cyl will be significant and after wearing it for a longer period on regular basis, the brain won’t be able to switch between translating a circle to circle when not wearing glasses and an oval to circle when wearing glasses. Also, optos tend to overcorrect for cyl (add when it is not needed) and that can result in lens induced cyl increase, too. Separately from the lens induced sph increase.

Same goes for unequal eyes. Natural vision gets the same images without lens created distortion. Cyl adds the oval shape, while the sph diopters make the images smaller. If one eye’s image is made smaller than the other one’s, the brain will need to compensate for it when merging the 2 images into one final image so they overlap perfectly.

This is why EM is all for reducing prescription complexity. So the difference between uncorrected eyes and corrected eyes is as little as possible. Obviously one is blurry but not distorted by lenses or not in an unequal way at least.

The typical screen or sedentary lifestyle created cyl axis is horizontal or vertical (vertical: between 75 and 105; horizontal: between 165 and 180 or 0 and 15. Note 0 = 180. So in other words it is 90 +/- 15 degrees and 180 or 0 +/-15 degrees)
Your son’s cyl - if correctly measured - is between these typical axes and about symmetrical. If the cyl has always been added from the first pair, it may mean that it is an actual unevenness in the eye or vision and it will be a personal call to decide if it is needed or can achieve good vision without the 0.5D cyl. The brain has magical powers in compensating.

I find the below squares and circles the easiest way to decide if there is real astigmatism and how significant is. With high astigmatism the squares work better, with little astigmatism the circles work better. Basically you need to get close enough to see all 4 of them sharp, then increase the distance until one blurs significantly while the others stay clear. With your son’s case, if the astigmatism at 130 and 40 are real, it will be the diagonal lines blurring first and in a different direction per eye. If it is only a little difference between first blurring and all blurring than it is not a well established astigmatism I’d say.

Also note that the first answers are more accurate than the later ones. It is because the more your eyes are looking at the parallel lines the more they start to correct the image “to expected image” in the brain. (I have a lingering tiny astigmatism left and I use these to quickly calibrate my eyes when I’m getting tired. Tells my brain “this is the clarity I expect”.)

Hope you find it useful.


It was there for his first prescription: -0.75 only for left eye. And one more thing to mention is when he is practising AF he has experienced double vison. So I believe there is astigmatism .Any thoughts?

Thank you for the details.

The astigmatism was there since his first prescription and with uneven diopter aswell( OD : -1.0 and OS : -0.5( cyl : -0.75 60dgree)

Then from the second prescription he always has uneven cyl for both eyes with uneven sph.

With the previous prescription from the current one it was again only cyl for left eye -0.75 and no cyl for right

The journey has been crazy till now with no even progression

I will try those images and get back with the real check

matter of preference. I like to make sure each eye is being used the same, hence same acuity is the goal, not same lens.

Jake talks about equalisation last here

but also talks about not correcting occular dominance-based slight differences via lenses, hmm

here Jake talks about the difference in eyes growing

didn’t happen for me. I always had about 0.25 difference and it has stayed that way all through the years, despite being corrected for it by the lenses

I would not introduce cyl for the right eye. That seems to be coming and going. So wouldn’t be a good idea to “plaster” it into the prescription.
For the left one, I also have a cyl measured in one of my eyes between zero and -0.75D. That is just an observation by the opto in my judgement. When my eyes feel good, I can (almost) completely disregard it. On bad eye days or when I’m really exhausted mentally, it is causing some double vision because the brain doesn’t have energy left to align images anymore. When I was at -2D, I had a pair of glasses that had -0.5D cyl added and occasionally I used those for night driving - for lazy and easy sharp vision.

Astigmatism is typically the permanent or transient unevenness of the eye. I believe that when the eyes go worse it doesn’t happen with the same rate all around the eyeball, but one part of the eye can compensate longer for the worsening vision than the other part of the eye. So one part is still on the previous prescription while the other part (a certain axis) could already do with stronger glasses. If the eyesight is measured at that point then there will be cyl prescribed, while in most cases a few months later it would all catch up to the same level of myopia within the eye.
So if the -0.5D cyl has always been there that might be something that will always linger around. But some optos correct cyl so much that people end up with -1D sph and -3.5D cyl which is totally crazy and mostly lens induced in my view.

The reason why I have preference for equal sph eventually (even if giving slightly different acuity) is because that imitates natural uncorrected eyesight best. And that makes it easier with the last diopters to switch between uncorrected and corrected.
For this reason, I would do anything to avoid pushing the gap bigger between the eyes, but if your son is happier with a 0.25D difference than with zero difference, I don’t think it really matters until he reaches the low diopters range.