While the most common symptom is blurring of the vision, the other symptoms include:

1. Squinting
2. Headaches
3. Double vision
4. Hazy vision
5. Sore or tired eyes due to strain
6. Difficulty in focusing on reading or watching something on a screen
7. Seeing a glare or a halo around bright lights
8. Crossed eyes in children

Refractive errors in the eye could be caused by one of the following:

1. Change in shape of the cornea or length of the eyeballs (shorter or longer) in case of myopia, hyperopia, and astigmatism and
2. Ageing of the lens (shape deteriorates over time in case of presbyopia)
3. A flatter or steeper surface of the eye that is present naturally
4. A thicker or thinner lens than usual
5. The size of the eye in general, like it, might be too long or short than normal

These problems of the parts of the eyes are mostly due to structural changes and rarely due to overstraining of the eyes. Some of the types of refractive errors may be:

1. Inherited - myopia and hyperopia
2. Due to the lens becoming rigid after the age of 40 years
3. Asymmetric curvature in the front surface of the cornea, as compared to the normal cornea with smooth and even curvature in all the directions

In adults:

Your ophthalmologist will diagnose any refractive errors using a dilated eye exam as follows:

1. Visual acuity test: Your ophthalmologist will check how well you can see by making you read alphabets and numbers that are near and far.
2. Visual field test: In this, your ophthalmologist will check how well you can see the objects off to the sides of your eyes. This basically checks your peripheral vision.
3. Eye muscle function test: The test will check for any disorders of the muscles of your eye. The ophthalmologist will move an object around your eyeballs and ask you to follow it with your eyes.
4. Pupil response test: Here, your ophthalmologist will observe how your pupil reacts to the light by shining a small flashlight into your eyes.
5. Tonometry test: This test will check the pressure of your eyes by using a machine to blow a quick puff of air into your eyes. The puff air is very gentle and doesn’t hurt.
6. Dilation: This test is where your ophthalmologist examines the inner parts of your eyes by widening your pupil. The widening or dilation is achieved by using an eye drop that may make your eyes blurry and light-sensitive temporarily. Hence you may want to ask a friend or a family member to go with you to your appointment.

In children:

The refractive errors in children must be caught as soon as possible. Earlier the diagnosis, slower the progression. Your paediatric ophthalmologist will use the following steps to diagnose any refractive errors:

1. A regular eye examination using a dilated eye exam as described for adults
2. In children where standard charts cannot be used, the steps used are
   1. The pupils are dilated using eye drops.
   2. Then, a retinoscopy is performed. This is an examination that observes the reflection of lights off the retina.

Refractive errors can be treated using a variety of methods as discussed below:

1. Eyeglasses – The safest and easiest way to treat refractive errors are through glasses. Your ophthalmologist will prescribe you the exact glass lenses to correct your vision. Thus, by wearing the glasses, you will be able to achieve the clearest vision possible.
2. Contact lenses – Contact lenses are the corrective lenses that can be placed on the surface of the lenses of your eyes to get a clear vision. These again will be fitted to adjust to your vision as prescribed by your ophthalmologist.

1. The treatment, in general, can prevent your eyesight from worsening. 
2. Corrective eyeglasses will help you see clearly and comfortably.
3. Multifocal lenses can slow the progression of near-sightedness or myopia.
4. Orthokeratology/Ortho-k are specialised custom-fit contact lenses that can slow the progression of near-sightedness or myopia when used overnight.

Some of the risks associated if not treated on time are:

1. A higher degree of near-sightedness or myopia may cause retinal detachment requiring surgical repair
2. Untreated refractive errors in children may lead to a condition called a lazy eye (amblyopia), where one dysfunctional eye makes the child depend entirely on the other eye. This leads to the deterioration of the functional eye over time.