Vision First July 2018 English

Focus on
Refractive Error
1. What are refractive errors?
In an ideal situation light rays that pass through the pupil of the eye are focused by the eye onto the nerve layer of the
eye (the retina) thus producing a clear image for the brain to process. Refractive errors are caused due to changes in
the length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens.
The main types of refractive errors are myopia (near-sightedness), hyperopia (farsightedness), presbyopia (loss of
near vision with age), and astigmatism.
In myopia or short-sightedness, light from a distant object forms an image before it reaches retina. This could be
because of longer length of eye ball or cornea and lens being more curved.
In hypermetropia or long-sightedness, light from a distant object forms an image behind the retina. This could be
because of smaller length of eyeball or cornea and lens not refracting light enough.
2. Possible manifestation of refractive errors
Blurring of vision
Headache on prolonged reading
Eye strain/ heaviness
Glare
Child goes close to the screen to see clearly
Squinting
3. Refractive error tests
Refractive error tests are done to access the best corrected vision for a person.
Ideal distance vision of a person is 6/6 (On a distance vision chart) and normal near vision is N6
Refractive error can be tested using different vision testing charts in different age groups of children. Some of the
tests require putting dilating drops in the eye.
Any person with an uncorrected vision less than 6/6 for distance and less N6 for near has a refractive error and
may require spectacles or contact lens to correct.
4. Optical outcomes of Refractive surgery
Refractive surgery decreases the need of spectacles and / or contact lenses. It improves the quality of vision in
individuals especially those with high myopia (short sightedness) and astigmatism.
7. How to prevent vision loss among children and adolescents due
to refractive errors?
Uncorrected refractive errors in children can cause lazy eye. One of the key ways to avoid vision loss in children is
the early detection of refractive errors . This can be achieved if there is enough awareness about paediatric refractive
errors amongst parents and caretakers. Regular eye check-up’s , evaluation for even minor degrees of squinting , good
compliance to patching therapy for the lazy eye can avoid vision loss amongst children and adolescents .
8. Can you be short and long sighted at the same time?
The same eye can’t be long-sighted and short-sighted at the same time. The confusion arises from mistaking presbyopia
with long-sightedness. Presbyopia can affect your distance and reading vision and usually occurs after the age of 40
years
9. What is Laser Vision Correction? What are the benefits of Laser Vision Correction?
Laser Vision Correction is a type of surgery which is done by applying a laser to reshape the cornea, the clear front part
of the eye, so that light traveling through it is properly focused onto the retina located in the back of the eye.
10. What is astigmatism?
An irregularly shaped cornea or lens prevents light from focusing properly on the retina, the light-sensitive surface at the
back of the eye. As a result, the image seen is perceived as blurred or distorted by the eye because of altered focusing
of light in a particular axis(meridian). This is known as astigmatism.
Due to imperfection of the Cornea, farsightedness (hyperopia) and short sightedness (myopia) occurs, and can co exist
with astigmatism.
11. What is Anisometropia of the eye?
Anisometropia is the condition in which the two eyes have significantly unequal refractive power.
12. What is presbyopia? What are the symptoms, causes, diagnosis, treatment, cure, correction,
surgery, prevention & excercises?
Presbyopia is a process of aging of the eye wherein the lens loses its flexibility and is now unable to focus near objects
.Inability to read comfortably and needing to keep the material at an increased distance, are the main symptoms of
presbyopia. Normally it starts after 40 years of age.
Near vision testing using different charts like Snellen’s near vision chart can pick up this. Eye glasses with bifocal or
progressive lenses would be the usual and most common resolution to these issues. If people do not prefer to wear
glasses they have the option of contact lenses. Refractive surgery for presbyopia is also available for people who do not
wish for either glasses or contact lenses.
5. The Impact of Corrected and Uncorrected Refractive Error on
Visual Functioning
Refractive errors are prevalent in a large population and are very often undiagnosed. When left uncorrected they can
lead to irreversible decrease in vision in one eye, especially in children.
Patients report symptoms of eye strain with difficulty in prolonged reading.
Patients with corrected refractive errors have a better quality of vision thus improving quality of life.
6. Prevalence of refractive error in India
Highly common and often undiagnosed with an equal prevalence in rural and urban areas.
6 Narayana Nethralaya | Ranked Among The Top 10 Eye Hospitals in India Since A Decade www.narayananethralaya.org Narayana Nethralaya | Ranked Among The Top 10 Eye Hospitals in India Since A Decade www.narayananethralaya.org 7