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Testing for Your Eye Glass Prescription

When you experience having vision problems for the first time, […]

By Published On: 10 August 20123.3 min read

When you experience having vision problems for the first time, the first thing that will come to your mind would most probably be that you need to get eye glasses. You may think that it is as easy as going to a grocery and getting the glasses that you want. You may even be excited about the prospect of having to choose from many stylish designs.

However, when you learn that you need to undergo an eye exam to determine the prescription for your eye glasses, you may no longer be that excited. You may even be daunted that you still need to go through a test. You don’t have to worry though because it is not as difficult as you think. Here are some things to guide you if you are about to get your eye glasses for the first time.


  • The exam is conducted to test your vision and to determine if you are suffering from any eye disease or condition. It aims to evaluate different aspects of your vision.
  • There are different methods of performing the eye exam. Different instruments may be used for this purpose. Bright lights may be aimed at your eyes and you may be asked to look at different lenses to determine what type to use for your eye glasses.
  • Your doctor will assess your visual acuity and he will discuss with you any conditions you may be suffering from, if any. If necessary, he will provide you with the prescription for your contact lenses or eye glasses.

Understanding Your Results

  • Diopter Rating. This refers to the degree to which your eye can focus. Your diopter rating is equivalent to the length in meters that you can focus on. For instance, if your rating is 1, this means that you can focus at a length of 1 meter or 39 inches. The higher the rating, the higher the magnification needed to focus. Normally, a child has a diopter of 40 but it declines as he ages which can go down to 1 when you reach the age of 50. A diopter rating of 1 indicates presbyopia or the condition where images up close are blurred. Diopter strength refers to the magnification in your eye glasses.
  • Visual Acuity. This is the common result you obtain when you have your eyes checked. This is represented by numbers like 20/20 which is normally associated with perfect vision. When you have a 20/20 vision, this means that the smallest letter you can read is 20 feet away. The lower the bottom number, this means that you have better visual acuity. In most cases, a person is classified as legally blind if his visual acuity is 20/200 or higher. Most governments require a vision of at least 20/40 for securing a driver’s license.
  • PERRLA Rating. Your Pupils Equal Round Reactive to Light and Accommodation (PERRLA) rating refers to the degree to which the pupils react to dark and light. Normally, your PERRLA should be 2 to 4mm in diameter in light and 4 to 8mm in the dark.  Your optometrist may deem it necessary to measure this when you need to get your eye glass prescription… why? It is a test of optic nerve function, macula function and neurological function.
  • Viewing and Imaging of the Retina. It is critical that an expert optometrist also assess the back of your eyes called your retina, whenever you have your eye glasses tested. Eye Diseases such as glaucoma and macular degeneration do not influence you vision through eye glasses until very late in the process.  It is imperative that eye diseases are screened for as being proactive here can avert disaster.
  • What does the Future Hold? Testing vision for a new pair of glasses in the future is likely to get very sophisticated for those of us that want to maximize their vision potential.  Using technology that designs multimillion dollar astronomy telescopes we will be able to customize eye glass prescriptions to another level using technology called wavefront aberration control optics.  This technology will also have application to contact  lenses.


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