What is Refractive Error? 

Refractive errors are a type of vision problem which occurs when the eye cannot clearly focus image on the retina which causes vision to become blurred. About 40% of the world population have significant refractive error and different eye conditions that lead to different errors; as there are various types of refractive errors. 

It is the second major cause of visual impairment. Though it can be corrected simply by a pair of glasses, millions of people remain blind or visually impaired. This is due to uncorrected refractive error. 

Uncorrected refractive error which affects people of all ages and ethinic groups is a major cause of visual impairment. This error affects vision and requires corrective lenses or surgery for correction.

Axial length of eye, corneal curvature, position and refractive index of crystalline lens determines the refractive status of the eye. If your child shows any signs of eye problems, you should take them to eye centers for eye examination. 

Causes of refractive errors 

Exact cause is being studied so far. But various evidence suggests that there might be genetic involvement. 

Refractive error is mainly associated with the shape of the eye. Even small changes/ variations in the shape of the eye increases the risk refractive error. These small variations are quite unnoticeable without proper eye examination. These variations are significant enough to affect how light is focused on the retina. 

Retina helps to convert light into signals which are carried  to the brain via optic nerve enabling us to process vision. For clear and accurate vision, light rays need to be focused properly. Variations may be seen in the shape of the eye due to ocular trauma or after eye surgery. 

Family history as well as developmental factors play a vital role for this. As for instance, Babies born prematurely are at higher risk. 

Symptoms 

  • Blurry vision ( distance or near or even both) 
  • Diplopia (Double vision) 
  • Glare issues : seeing glare or halos around bright light) 
  • Squinting 
  • Headache, Eye strain 
  • Frequent eye rubbing and tilting head often 

Sometimes, people may not face symptoms. So it can be a wise decision to check the eyes regularly. Similarly, if you are still experiencing symptoms even after wearing glasses or contacts then visit an eye doctor immediately. You might require a new prescription. 

Types of Refractive Errors 

Basically there are three types of refractive errors i.e myopia, hyperopia and astigmatism. Some consider presbyopia as a refractive error too. But presbyopia is just a physiological change that occurs in the eye after the age of 40. 

Myopia 

Also known as shortsightedness or nearsightedness. 

It occurs when light rays focus in front of the retina causing blurred distance vision. Myopia is usually inherited and often discovered in childhood. It usually occurs between 5-15 years of age and often progresses till mid-twenties. 

This happens when the eyeball is too long or the cornea too curved which causes rays of light to focus in front of the retina. 

Different Research suggests that too much close-up working can cause myopia. Decreased outdoor activity is also one of the major risk factors. Myopia can also be developed in later life too, in some cases like cataract. 

Hypermetropia 

Commonly known as hyperopia or longsightedness or farsightedness. 

Hyperopia occurs when light rays are focused behind the retina. Close objects seem to be blurry than distant one. It can also be inherited. Children often have hyperopia which may lessen in adulthood. In mild hyperopia, distance vision is clear while near vision is blurry. But in advanced cases, vision can be blurred at all distances. 

It happens when the eyeball is too short or the cornea is a little flat which causes rays of light to focus behind the retina. 

It is seen that some hyperopic people do not wear glass until they get older, as they can use additional focusing power to clear vision when they are young. 

Babies are often born with some degree of hyperopia but grow out of it till age of two as their eyes develop. If not, there can be increased risk of squint or amblyopia

Astigmatism 

Conditions in which rays of light that pass to the eye do not focus at the same point on the retina. Abnormal corneal curvature or lens of the eye causes two focal points to fall in two different points which causes distorted vision. 

It may cause eye strain, headache and often can occur in combination with myopia and hyperopia. In this condition, straight lines may appear wavy. 

It is common at birth but often corrects itself as the eye develops. If not corrected, then there might be problems. It can be developed in adulthood or later; basically after eye trauma, excessive rubbing or after eye surgery.

Presbyopia 

Basically, it is physiological changes that occur in an eye after the age of 40. The crystalline lens of the eye becomes rigid and less flexible. Then the eye loses its focusing ability and it creates problems while reading or seeing at arm’s length. 

This is linked to ageing and occurs almost universally. Regardless of refractive error, it may occur in all people. 

How can you diagnose refractive error? 

Generally, Eye care practitioners perform comprehensive eye examination and series of tests to diagnose refractive error. They may ask you about the symptoms you are experiencing as well as medical history and medications.

Test is quite simple. Mostly they will ask you to read letters or symbols in the vision chart at distance and near. 

Furthermore, children may not be aware about the issues. So it will be important to look out for possible signs that a child may be showing. As if a child is struggling to clear an object or not. Similarly, we can observe if a child is sitting close to the TV Screen. In addition we can see if a child is tilting their head or rubbing eyes frequently. 

Treatment options 

Treatment options basically include prescription glasses, contact lenses or with refractive surgery such as LASIK. 

Correction is often given in different forms according to the defect, age and requirements in terms of work of activity performed. 

Glasses 

One of the easiest and simplest ways to correct refractive errors. Eye care professionals will provide prescription lenses to give you possible clear vision. 

Contact Lenses 

Thin transparent lenses placed on the surface of cornea to correct refractive errors. It is the second best alternative to correct refractive errors. As well they can be used for cosmetic or therapeutic purposes too. 

Eye care professionals will fit the exact lenses and will give you proper information about contact lenses. They will provide prescription and other parameters required. Furthermore, you can get care and maintenance tips from professionals, as it requires a lot of care and maintenance. 

Refractive Surgery 

Refractive surgery such as LASIK can be performed by changing the shape of cornea to fix the refractive errors. 

Eye care professionals will perform a certain series of tests to confirm if you are fit for surgery. 

Presbyopia in absence of refractive error can be corrected simply by prescribing reading glasses. There is no way to slow down or reverse presbyopia. 

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