2. Myopia is a refractive defect or error in visual focusing. Images are focused in front
of the retina and not on it, making distance vision difficult. When the visual error
exceeds eight dioptres, it is referred to as high myopia
3. High myopia is a relatively severe level of nearsightedness that can be associated
with significant eye health complications.
The term high myopia generally used to describe nearsightedness of -6.00 to -8.00
D or higher, which produces uncorrected visual acuity of 6/60 or worse.
In other words In a healthy eye, light enters the lens of the eye and is refracted
onto the retina to form an accurate, sharp image that the brain can decode. In
short-sighted people, the refraction doesn’t work properly; the light is bent so that
it focuses in front of the retina, creating a blurry image. This happens if the eye is
the wrong shape – the eye may be too long, or the cornea might curve at the
wrong angle
4. Inheritance
In almost all cases, heredity plays a role in the development of high myopia.
If both parents are quite nearsighted, their child has a greater risk of developing high
myopia.
But developing myopia isn’t purely a case of genetic inheritance. Our living
environments play a part in determining whether the genes we carry will actually be
triggered. The more we understand about these environmental factors, the more we can
do to prevent myopia in future generations. There’s still a lot of work to be done in this
area, but there are some factors that do seem to be linked to elongated eyeballs, which
can lead to myopia.
Scientists have found that time spent indoors, doing close-up work such as reading, is
linked to a higher risk of short-sightedness, although researchers are yet unsure
whether it’s the lack of daylight or the close-up work that is more of a factor. In any
case, this is a risk factor that can be minimized in early childhood
5. Possible Etiologies of Myopia by
Classification
Nocturnal Myopia
Significant levels of dark focus of
accommodation
Simple Myopia
Inheritance
Significant amounts of near work
Unknown
6. Pseudomyopia
Accommodative disorder
High exophoria
Cholinergic agonist agents
Induced Myopia
Age-related nuclear cataracts
Exposure to sulfonamides and other
pharmaceutical agents
Significant variability in blood sugar
level
Degenerative Myopia
Inheritance
Retinopathy of prematurity
Interruption of light passing through
ocular
media
Unknown
7. Nocturnal Myopia
Occurring under conditions of darkness or very dim illumination,
Nocturnal myopia is due largely or entirely to an increase in accommodation
associated with the decreased accommodative cues in darkness.
The accommodative dark focus appears to be relatively stable, at least over a
period of days.
In nocturnal myopia, the results of retinoscopy in a dark room may be shifted in the
minus direction, compared with the standard manifest refraction. Patients who have
nocturnal myopia often complain of difficulty driving at night and/or blurred
distance vision at night.
8. Pathological myopia
Degenerative or pathological myopia is generally high myopia that is congenital or
of early onset. Corrected visual acuity may be reduced as a result of pathological
changes in the posterior segment.
Abnormal or adverse ocular changes in degenerative myopia can include:
Vitreous liquefaction and posterior vitreous detachment
Peripapillary atrophy appearing as temporal choroidal or scleral crescents or rings
around the optic disc
Lattice degeneration in the peripheral retina.
9. Tilting or malinsertion of the optic disc, usually associated with myopic conus
Thinning of the retinal pigment epithelium with resulting atrophic appearance of
the fundus
Ectasia of the sclera posteriorly (posterior staphyloma)
Breaks in Bruch's membrane and choriocapillaris, resulting in lines across the
fundus called "lacquer cracks"
Fuchs' spot in the macular area.
12. High myopia itself does not generally lead to vision loss. However, people with the
condition have a greater risk of developing several other vision-threatening
conditions, including.
Retinal detachment
Glaucoma
Cataracts
13. The retina's center (macula) thins with age. While this does not affect side (peripheral)
vision, the ability to focus on a particular object (like reading a sign) diminishes and is
eventually lost.
Retinal thinning can also lead to tears and holes, which can cause the retina to detach.
(Learn more about retinal detachment.)
The retina can split, a condition called myopic retinoschisis (MRS).
Layers of the eye under the retina can degenerate or crack, allowing new, faulty blood
vessels to grow under the retina (a process called choroidal neovascularization, or CNV).
The vessels can bleed and scar, with small scars causing minor macular damage and
larger ones more significant problems.
Increased eye pressure may lead to glaucoma.
Cataracts are more likely to develop.
The eyes become more susceptible to injuries and other traumas.
14. Progressive high myopia generally does not lead to permanent vision loss or
blindness, however axial elongation of the eye accompanied by progressive high
myopia can lead to thinning of the light sensitive tissue known as the retina, which
in turn can lead to retinal tears and retinal detachment. It can also lead to
pathological myopia, where thinning of the macula occurs which can lead to
permanent, even devastating vision loss.
15. Management of high myopia
Spectacle correction
Contact lens
Refractive surgeries
Clear lens extraction
And in the last the most latest technique is
ORTHO K
16. Orthokeratology (orthok) has been shown to have the greatest effect..
Orthokeratology is one of a class of therapies known as vision shaping treatments.
OrthoK involves wearing orthokeratology lenses (ortho k lenses) during sleep,
which gently reshape the surface of the cornea of the eye. Upon removal in the
morning, clear vision is achieved which often lasts the entire day into the evening.
