Sometimes, we are diagnosed with a very low refractive error in our eyes and ophthalmologist/ optometrist prescribe the eyeglasses with a very low strength lens such as minus 0.25.
People often ask us whether it is mandatory to have such lens power incorporated in the glasses. Well we will not say that you should not have minus 0.25 power incorporated but practically it is not much required to have such a low strength power. Some opticians do push the customers to buy such lenses in order to charge more than plano/ zero power lenses. The good news is that at Zebriana, there are no extra charges as long as the total lens power falls within the range of – 6 Dioptre.
Now let’s understand what does it mean to have minus 0.25 lenses in your eyeglasses. Kindly note that we are talking about minus 0.25 spherical and not 0.25 cylinder.
You must have heard of 20/20 vision or 6/6 vision. They both are same and if luckily you have that vision, you are blessed. 20/20 means a person can read out the 8th line of the Snellen chart without any problem with each eye by standing at an exact distance of 20 feet.
However if your prescription mentions minus 0.25 SPH it simply means that a person with normal eyesight can read the 7th line of Snellen chart from a distance of 25 feet but you must be positioned 20 feet from Snellen chart to read the same line. In that case your Snellen score will be 20/25.
Then why did the doctor prescribed that lens power?
That is an interesting question. The answer is he has just reported what he observed. Consider the example of a person who goes to a doctor for his routine health checkup. Doctor checks his body temperature and reports 1 degree higher than normal temperature i.e 97°F. Now does it mean that the he should consume medicines? He may or he may prefer not to take any medicine as it is just a mild deviation from the base line.
Same way it is up to the person whether he wants to have such power incorporated in the glasses or not. You should be concerned about having this power if it is important for you to read small text (usually half an inch) at a distance of 20 feet.
You should also note that the medical diagnosis may also slightly deviate from the actual position, if you are suffering from fever or are tired or have worked in front of digital screen for long hours or have reached the clinic by travelling through a dusty/ air polluted area. Before getting your eyes examined, always make sure that you & your eyes are feeling completely normal. If possible then wash your eyes with water 10 minutes before eye examination.
Let us close this article by concluding that a person who is diagnosed with minus 0.25 refractive error is not likely to feel any significant difference with or without wearing prescription glasses with that power.