Thank you again. I’m glad I found this site. (Funny detail: I lived in Colorado for eight years but am now back on the East Coast.)

Normally with prism being used Base Out it would be used in front of each eye. Are you sure there is not some vertical prism base up or base down in the glasses? If it is just in front of one eye I would think you should be fine without it at those times but you would need to ask your eye doc for an Rx without it.

Best Wishes

The amount of prism that can be ground into a lens is determined by the frame size, shape, and the amount of prescription in the lenses. Too much prism will not allow the lens to stay in the frame, and the distortion induced by the prism may become excessive. That being said, 5-6 in each eye is probably the upper limit of what is practical. Fresnel press on prism can extend this range but they do significantly reduce the clarity of vision. People that are partially sighted can tolerate higher amounts of prism in specially ground lenses since the distortion of vision form the prism will not be as noticeable. Hope that helps.

Best Wishes

I doubt the snooze had any effect on the prescription other than giving the drops a little more time to work. It can be a little bit of a dilemma with a 4 year old to prescribe lenses they will wear. Depending on the type of drops used, they will alter the amount of prescription shown in the readings. Four year olds have such a large focusing capacity that they can over compensate and give artificially low readings. Once the drops kick in and eliminate a large amount of this focusing, a more true reading can be seen.

Unfortunately, just because its their prescription that doesn’t mean they can tolerate. It is somewhat similar to holding your fist clenched all day then trying to open it at the end of the day-you can’t let go of the tension all at once. My guess would be that is your sons case. If he is tested with adequate drops he probably shows more prescription than without. The end result is starting with the lower prescription should allow him time to adjust and it can probably be made stronger next year. The 20/30 and 20/40 are not out of line for a +3, kids have a lot of ability to compensate and clear vision up when they are farsighted. So both docs are right in a way, but the prescription you can use is always the best one!

Best Wishes

Meniere’s Disease must be rally tough to cope with the dizziness, you have my respect. When the base input from the ears to the brain is imbalanced from asymmetric damage in the ears, jerk nystagmus results. If there is a null zone, or area of gaze where the nystagmus is lessened, prism can be used to keep the eyes turned towards that field of view without turning the head. I presume that is why the prism was prescribed, but usually that would be in the form of “yoked prism”, which entails prism in front of each eye. It is possible there was a small amount of prism placed in your prescription for a vertical eye imbalance that predated the Meniere’s. In that case your eye doc was trying to improve the way your eyes work together overall to try and help them compensate for the nystagmus.

It is normal to have some fluctuation in the nystagmus just like the overall disease. The brain also tends to dampen nystagmus over the course of the first month. Either way (or both combined) it would not be surprising to adapt at first and then have some changes like you have described. Prism can be a very odd thing for the brain and leave funny feelings in your head for a day or so if it is not matched up to what you need. Spatial shifts are induced in the brain and the brain has to reset so to speak.

I would go back and have it rechecked. There are also some optometrists that specialize in neuro-optometric rehabilitation. Sometimes sensitivity to nystagmus can be reduced through vision therapy procedures.

Best Wishes

I was prescribed prism lenses a few months ago to try to cope with chronic nystagmus I have as a result of Meniere’s Disease that was treated with surgery last year (labyrinthectomy). For the first month I felt OK with the new glasses, after an initial week or so of very strange feelings of dizziness. It became better going into the second month, but very recently I’ve felt more eye strain and discomfort, as well as slightly blurred vision.

I’m wondering why I’m not fully accustomed to the lenses at this point, and whether I need to go back to the ophthalmologist. I still feel dizzy every day, too, which was the symptom we hoped the prism lenses would make go away. The prism prescription is very mild, and only on the right lens. My glasses are progressives, with a mild magnification for distance and somewhat stronger magnification for reading.

Any advice or comments would be greatly appreciated.

I would advise letting the eye doctors office know if you are still dilated the next day. I will not usually see the patient at that point as long as there are no other symptoms, but I do want to know. The only real risk is angle closure glaucoma in people who are predisposed with abnormal iris structures. This is a one 250,000 people so it is a fairly low risk. It is the dilation itself and not so much the duration of time that elevates the risk. The problem occurs at mid dilation where the pupil gets stuck. That may make it seem like someone is staying dilated for a very long time when in fact they have angle closure glaucoma. Usually people with this condition are very sick with nausea, headaches, and upset stomachs (not a little but a lot). The other risk from extended dilation is an increase in UV and visible blue light exposure. Without proper sunwear protection this can result in acute injury (snow blindness) and contribute to long term risks for macular degeneration and cataracts. We always have people wear the wonderful looking little roll up sunwear when they are outside until their eyes return to normal. Unless you have high quality dark sunglasses, you should rely on these in addition to your normal sunglasses or to replace them.

Best Wishes

My question is how many prisms can one have in your lenses. I have 4 in my left lense and 2 in my right lense

Kind Regards
Brendan