This is probably the most common cause of temporary prescription changes. In general, if a patient has high blood sugars, they will experience a myopic shift (become more nearsighted). When their blood sugars stabilize, I will see the opposite change, there will be a hyperopic shift (become more farsighted). Both of these shifts will normalize. The time it takes depends on how quickly we can get the blood sugars back to normal. I usually wait until a patients HbA1c levels (anyone who is diabetic will know what a HbA1c is) have normalized before I finalize their glasses prescription. This can occur over one month but can be up to three months. The root cause of this change is from a change in how well the lens inside of our eye bends light also known as the refractive index.
Hyperbaric chambers were initially used to treatment decompression sickness and is now used to treat soft tissue degenerative conditions such as osteoradionecrosis (damage caused by cancer treatment) or treating wounds that will not heal. It is believed that hyperbaric chambers change the refractive index of the lens inside your eye because of the high concentrations of oxygen. The average result of this treatment is a 0.50 diopter myopic or more near-sighted shift. This is temporary and usually resolves after 12 weeks.
As if your body is not already going through a ton of changes. Your eyes can change as well. Some pregnant women undergo a myopic shift while pregnant and even while breastfeeding. I usually wait until after a patient is done breast feeding before I can truly finalize their glasses prescription. The myopic change usually occurs near the end of the pregnancy and averages around 1 diopter. This change is temporary and usually returns back to normal, pre-pregnancy levels. Although, in my experience I have seen prescriptions change permanently following pregnancy.
Some medications have been known to cause transient myopic changes. This list is by no-means comprehensive but Sulfa based drugs seem to be the most common drugs to cause of this. Some examples include acetazolamide (Diamox), indapamide and sulphasalazine. The mechanism or cause of this temporary change, is thought to be caused by the focusing muscles in our eye continually firing. This leads to this change our eyes over-focusing or becoming more near-sighted. By stopping the medication this issue will usually self resolve (It should be noted that you should never stop any medications without consulting with your doctor first).
This does not necessarily cause a change in your glasses prescription. However, it can wreak havoc on how well you see. The best analogy for dry eyes, would be like “looking through a dirty windshield”. Often times it is best to get the dry eyes under control before we finalize the glasses prescription.
Brent Hopfauf BSc OD