WHY YOU NEED TO PAY ATTENTION TO YOUR EYES/REFRACTIVE ERRORS; MYOPIA

I have been busy for a while now, hence, my being unable to post. I had a tooth extraction, and anyone who has had those will understand the pain and discomfort that comes with it. Anyways, I'll be having another soon, but I hope it doesn't keep me away. In high school, I enjoyed reading novels and I read a lot of them. The stories really captivated me to the point where I didn't notice the distance between the book and my eyes had become almost insignificant. My classmates kept asking why I had to take the book so close to my eyes before reading but I completely ignored and laughed over it. I wasn't one to seat in front, but I found myself moving to the front of the class to get a better view. I went to a boarding school, when I got home for holiday, it continued. My mum, being a nurse, noticed it almost immediately I got home and asked me certain questions about my eyes. Then, I knew, I had to see a doctor. I currently wear spectacles. If you have ever used a camera or even taken a close look at one, you'll see that the eye is like a camera.

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.

ERRORS OF REFRACTION

1. Myopia
2. Hypermetropia
3. Astigmatism
4. Aphakia
5. Anisometropia
6. 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

1. Basic ophthalmology
2. PUBMED
3. Wikimedia commons