Pathophysiology of myopia

1. PATHO
PHYSIOLOGY
OF
MYOPIA
By, Divya Goyal
BMCO

2. Q&A
Que 1 - Short-sighted people may suffer from tired eyes and severe
headaches by overstraining their eyes.
a. True
b. false
Que 2 - Myopia is seen more commonly in
a. School going children
b. Adults
c. Older Persons

3. cont…..
Que 3 - Peripheral hyperopic defocus triggers myopia.
a. True
b. False
Que 4 - Tendency for short sightedness is inherited from parents.
a. True
b. False

4. MYOPIA
Nearsightedness
(myopia) is a common
vision condition in
which near objects
appear clear, but objects
farther away look blurry.

5. CAUSES OF MYOPIA
➔ Since myopia is rarely present at birth. Most of such patients are
rather born hypermetropic, but during development the normal
mark is overshoot and the child becomes myopic.
➔ Myopia commences at the school going age when a child is put
to close work and progresses throughout the years of life, near
work and reading were considered to be the primary causal
factors.
➔ In myopia, genetic factors play a major role. At present, high
myopia (>6D) is considered to be a recessive inherited disorder.

6. OPTICAL: Peripheral Focus Intense Near Work

7. Not enough time
spent outdoors
Genetics

8. ANATOMICAL FACTORS
1. Axial : It may be axial, in which the eye is relatively too long for it’s refractive
status.
In this the total refractive power of the eye may be same as in any normal eye
but due to increased length of the eyeball the parallel rays are brought to focus
in front of the retina.

9. Cont…..
2. Refractive status in which the dioptric power of the eye is too strong for axial
length; in this case the axial length may be the same as in any normal eye.
The refractive myopia may be further considered as:
(a) Curvature: In which the cornea is more curved than the normal as in
megalocornea or buphthalmos or there may be an increase in the curvature
of the lens.
(b) Index: This may be due to change in index of the lens (diabetes and cataract).
It may be high refractive index of aqueous, lens nucleus and cornea or low
refractive index of lens cortex or vitreous.

10. Cont…..
3. Functional : Myopia which occurs due to the excessive use of
accommodation in patients with spasm of accommodation.
4. Positional : It is produced by anterior placement of crystalline lens in the
eye.

11. Q&A
Que 5 - In Index myopia the refractive index of ________
increases.
a. Core
b. Cortex

12. PHYSIOLOGICAL CHANGES
1. Defective vision for distance

13. 2. Asthenopic Symptoms : Symptoms of eye strain develops due to dissociation
between convergence and accommodation.

14. 3. Change in psychological outlook of the uncorrected myopic children

15. 4. Muscae volitantes

16. 5. Night Blindness

17. PATHOLOGICAL CHANGES
More growth of retina
Stretching of
Sclera
Increased axial length
Degeneration of Choroid
Degeneration of Retina
Degeneration of Vitreous

18. ➔ There is considerable failure in
visual functions. In progressive
myopia the error is usually high
and the vision in not usually
correctable to normal. When
corrected the objects looks
smaller in size, they are well
defined and look brighter than
normal which is annoying and
fatiguing.
➔ The visual inadequacies are
related to choroidal atrophy.

19. CHANGES IN FUNDUS
➔ Optic Disc appears large and
pale and at it’s temporal
edge, a characteristic myopic
crescent is present.
➔ Myopic crescent usually
appears at puberty and in the
early stages it is seen as a
white sharply defined area.

20. DEGENERATIVE CHANGES OF RETINA AND CHOROID.
● Tigroid appearance of the fundus

21. ● Foster Fuch’s spot
(dark red circular
patch) forms an
occasional
characteristic feature
at the macula which is
due to proliferation of
pigment epithelium
and is possibly
associated with
choroidal
haemorrhage.

22. ● Cystoid degeneration

23. ● Retinal tears, haemorrhage and Retinal Detachment

24. ● Posterior staphyloma due
to ectasia of sclera at
posterior pole may be
apparent as an excavation,
with the vessels bending
backwards over it’s
margins.

25. ● Vitreous
degeneration - The
vitreous shows
microfibrillar
degeneration
leading to
liquefaction and
formation of
micellar and
bizarre shaped
floating opacities.

26. ● Primary open angle Glaucoma

28. Q&A
Que - The following complication can occur in long standing severe myopia.
a. Retinal Detachment
b. Glaucoma
c. Cataract
d. All of the above
Que - Rapidly progressive severe myopia is termed
a. Nocturnal myopia
b. Pseudomyopia
c. Degenerative myopia

29. MYOPIA PREVALENCE

32. Q&A
Que - The incidence of myopia is highest in which of the countries.
a. India
b. Singapore
c. China
d. Australia
Que - A person is said to have severe myopia when his myopia is
a. Less than -3D
b. -3D to -6D
c. More than -6D

33. References
➢ LP Agarwal : Optics & Refraction
➢ Theory and Optics of Refraction
➢ Images from google
➢ www.myopiaprofile.com
➢ Healio
➢ All About Vision
➢ American Academy of Ophthalmology
➢ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675264/
➢ Eyewiki
➢ Mayo Clinic
➢ www.frontiersin.org
➢ British Journal of Ophthalmology