WHY YOU NEED TO PAY ATTENTION TO YOUR EYES/REFRACTIVE ERRORS; MYOPIA
Eye | Camera |
---|---|
Lens | Lens |
Retina | Film |
Pupil | Aperture |
Iris | Diaphragm |
By File:Greeneyes.jpg: Original uploader was Laurinemily at en.wikipediaLater versions were uploaded by Lilallisun, AED at en.wikipedia.derivative work Luhmann - File:Greeneyes.jpg, CC BY-SA 3.0, wikimedia commons
By User:Jean François WITZ - This is a modification of Reflex_camera_numeric.svg, CC BY-SA 3.0, wikimedia commons
By Cancer Research UK - Original email from CRUK, CC BY-SA 4.0, wikimedia commons
In my previous post, I discussed the anatomy of the eye. It'll be helping us understand subsequent discussions so you can click here to go over it.
Refraction or bending of light Ray's occur when light passes from a medium of one density to a medium of a different density.
Images formed on the retina are inverted, but becomes re-inverted in the brain
The normal optical condition of the eye is EMMETROPIA.
Light Ray's from infinity come to focus on the retina, with accommodation at rest.
The average power of a normal eye is +58D to +60D, and the normal eye is approximately 24mm in length.
- Myopia
- Hypermetropia
- Astigmatism
- Aphakia
- Anisometropia
- Presbyopia
In this post, our focus will be on MYOPIA. This is to avoid it being lengthy.
MYOPIA (a.k.a nearsightedness) is a refractive condition of the eye in which light rays focus anterior to the retina.
A study showed a Prevalence of about 80% to 90%, in young adults in East Asia. This study also showed myopia to be the leading cause of blindness in that area.
By National Eye Institute, National Institutes of Health -, CC BY 2.0, Wikimedia commons
A study done in 2020, showed that it affects all population, and could be caused by both genetic and environmental risk factors.
Another study showed that it is a public health issue, mainly due to incread axial length of the eyeball.
Other causes includes; abnormal curvature of the eyeball, too high refractive index or forward displacement of the lens.
Myopia can be Congenital, simple or pathological.
Congenital | Simple | Pathological |
---|---|---|
Present at birth | Most common type | Strongly hereditary |
Usually stationary | No degenerative changes in the fundus | Degenerative and progressive |
It may be bilateral (associated with convergent squint) or unilateral | It does not progress after adolescence when a degree of -5 or -6D is attained | Begins at age 5-10years and increases steadily |
The most common presenting complaint is indistinct distant vision, while other features includes, black spots floating before the eyes, discomfort after near work, flashes of light, prominent eyes, large pupil, deep anterior chamber and apparent divergent squint.
If it is not corrected, it could lead to vitreous degeneration, retinal detachment, complicated cataract, chronic simple glaucoma, e.t.c.
The prognosis is good in simple myopia.
It is adviced that two high myopes should not get married if possible.
We often overlook eye hygiene, sounds strange right?
To make accurate diagnosis, several test must be done. These tests also help to determine the possible cause. Two methods are used; objective methods and subjective methods.
The objective methods include; retinoscopy, auto-refractometer, keratometer. While the subjective is the postmydriatic test.
Eye hygiene has to do with proper position, good illumination and correct distance from the book (about 25cm) while reading.
By Gumenyuk I.S. - Original artwork made specially for Wikipedia, CC BY-SA 3.0, Correction of myopia using concave lens
Myopia is treated by prescribing suitable correcting spherical concave lenses for constant use. In low degree myopia, spectacles are rarely required.
In more severe cases, operative options are available, such as, Radial keratotomy, Excimer laser, Epikeratophakia, Keratomileusis, LASIK (Laser Assisted in situ Keratomileusis).
According to a 2016 study in Asia, Pharmacological agents and optic interventions such as low-concentration atropine and orthokeratology may slow progression in myopic children.
Thanks for your
That brings us to the end of this discussion. Stay tuned for next post.
REFERENCES
- Basic ophthalmology
- PUBMED
- Wikimedia commons
Here is a great post about our vision and the disease that could arise from it. You did a lot of work putting this together.
Thank you.
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