Refractive Errors

For people with normal vision, the light which rebounds off objects into the eye is focused onto the retina, meaning that they can see a clear image of that object. However, if that light is focused onto the area in front of or behind the retina, the image will be unclear. Such conditions are referred to collectively as refractive errors.

Refractive errors can be categorized into the following four main forms: short sightedness, far sightedness, astigmatism, and age related far sightedness.

 

Shortsightedness

The result of the light from objects entering the eye and focusing just in front of the retina, short sightedness causes people with this condition to see objects close with clarity while objects that are far away appear blurred.

Short sightedness occurs when the eyes grow longer than they should from front to back or the cornea curvature is greater than normal. There are also other factors which may affect someone’s chances of developing short sightedness, such as genes passed down from parents with short sightedness or certain activities which involve looking at objects at close range for a prolonged period of time, whether that be reading books, using a computer or using a mobile phone.  
 

Farsightedness

This condition is caused by light focusing on the area behind the retina rather than on the retina itself. Causes include eye shape ad size which is shorter than usual or has a corneal curvature which is less than normal, both of which lead to unclear images when viewing objects at close range whereas objects far away appear clearer. However, in severe cases, the patient may also have issues with seeing faraway objects clearly as well as those at close range.
 

Astigmatism

Astigmatism is an imperfection in the curvature of one eye’s corneal lens, meaning that there are two focal points rather than one single image as a point of focus before or after reaching the retina. This condition can occur alongside short sightedness or far sightedness, and those with astigmatism will often see distorted images in that eye.
 

Age Related Farsightedness

A condition that occurs when the muscles in the eye deteriorate with age and the lens becomes less flexible than before, age related far sightedness negatively affects the functionality of the eyes’ focus adjustment, which is used to help the eye see a clear image at close range. The condition usually affects those over the age of 40 years old with sufferers commonly encountering symptoms such as being unable to read or see objects at close range as clearly as before but being able to see objects far away as normal.
 

Diagnosing Refractive Errors

Ophthalmologists perform a sight exam to diagnose refractive errors, alongside asking the patient to wear spectacles which will help them to see more clearly. Regularly undergoing such assessments with an ophthalmologist can help to identify any issues as well as quickly targeting the condition for treatment. Many people are unaware of their eye disorder and lack of clear vision due to their gradual familiarity with the condition, which means that they do not seek treatment as quickly as they should.

 

Treatments Available for Refractive Errors

Treatments come in the form of spectacles, contact lenses, or laser eye surgery, forms of treatment that offer a permanent solution to the problem. Currently, the most popular forms of laser eye surgery techniques are as follows:
  • ReLEx SMILE (Refractive Lenticule Extraction / Small Incision Lenticule Extraction) which is a form of surgery that can cure shortsightedness and astigmatism without the need for scalpels. A femtosecond laser is used to separate the inner corneal tissue, called the lenticule, reshaping the cornea as a result. This lenticule is then removed through a small incision at the corneal surface to alter the corneal curvature in a way that minimally affects the top layer of the cornea or the nerves of the cornea. Furthermore, this is the only form of laser surgery that utilizes a single laser device for the whole procedure. 
  • LASIK eye surgery is a form of laser surgery that opens up the corneal lid with a microkeratome or femtosecond laser so that an excimer laser can be focused into the corneal tissue to alter its curvature.
  • PRK (photorefractive keratectomy) is a form of laser eye surgery. First, the top most layer is removed either manually, by alcohol delamination, or by laser; then the excimer laser is used to remove corneal tissue. The excimer laser is a cool form of laser that is focused onto the corneal tissue underneath in order to adjust the corneal curvature, as well as improving the patient’s vision score. Once the process is completed, the wound is sealed with a special contact lens.

The choice of treatment is dependent on the opinion of the ophthalmologist, who will first carry out a thorough eye examination and advise each individual patient on the form of treatment most suitable for their eyes and sight on a case by case basis.
 

 

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