Nearsightedness (myopia) is a common vision condition in which near objects appear clear, but objects farther away look blurry. It occurs when the shape of the eye — or the shape of certain parts of the eye — causes light rays to bend (refract) inaccurately. Light rays that should be focused on nerve tissues at the back of the eye (retina) are focused in front of the retina. Nearsightedness usually develops during childhood and adolescence, and it usually becomes more stable between the ages of 20 and 40. Myopia tends to run in families. A basic eye exam can confirm nearsightedness. You can compensate for the blurry vision with eyeglasses, contact lenses or refractive surgery.

1. MYOPIA

2. LAYOUT
• Introduction
• Optics
• Classification
• Treatment of myopia

3. EMMETROPIA
• When parallel rays of light coming from infinity are focused on
sensory retina with accommodation being at rest.
• Components that maintain emmetropia are:
a. Axial length
b. AC depth
c. Corneal curvature

4. AMETROPIA
• State of refraction wherein the parallel rays of light coming from
infinity are focused either in front or behind the sensitive layer of
retina in one or both the meridian with accommodation at rest.
• Further classified into:
a. Myopia
b. Hypermetropia
c. Astigmatism

5. MYOPIA
• Also called short sightedness.
• It is a type of refractive error in which parallel rays of light coming
from infinity are focused in front of the retina when accommodation is
at rest.

7. TYPES OF MYOPIA
ETIOLOGICALLY:
a. Axial myopia
b. Curvatural myopia
c. Index myopia
d. Positional myopia
e. Myopia due to excessive accommodation

8. CLINICALLY:
a. Congenital myopia
b. Simple or developmental myopia
c. Pathological or degenerative myopia
d. Acquired myopia

9. AXIAL MYOPIA
• Commonest form
• Increase in antero-posterior length of the eye ball
CURVATURAL MYOPIA :
• Increased curvature of cornea , lens or both
POSITIONAL MYOPIA :
• Produced by anterior placement of crystalline lens in eye

10. • MYOPIA DUE TO EXCESSIVE ACCOMODATION :
• Spasm of accommodation
• INDEX MYOPIA :
• Increase in refractive index of crystalline lens associated with nuclear
sclerosis

11. CONGENITAL MYOPIA :
• Since birth
• Diagnosed by 2-3 years
• Mostly unilateral
• Manifests as anisometropia
• Child may develop convergent squint in order to preferentially see clear at its
far point (10-12cms )
• Associated with cataract , microphthalmos, aniridia , megalocornea ,
congenital separation of retina

12. SIMPLE MYOPIA
• Developmental myopia – commonest variety
• School myopia ( school going age 8-12 years )
ETIOLOGY
Axial type :
physiological variation in length of eye ball
precocious neurological growth during childhood

13. • Curvatural type: Underdevelopment of eye ball
• Role of diet in early child hood
• Role of genetics : prevalence of myopia
 both parents myopic(20%)
 one parent myopic (10%)
 no parent myopic (5%)
• Theory of excessive work :
Myopia is aggravated by close work, watching television, smart phones,
computer for long duration of time.

14. SYMPTOMS:
Poor vision for distance:
• Main symptom of myopia
Half shutting of eyes:
• To achieve greater clarity of stenopic vision
Asthenopic symptoms:
• Occurs in patients with small degree of myopia
• Develops due to dissociation between convergence and accommodation

15. Change in psychological outlook:
• Common in uncorrected myopic children.
• Takes poor far vision for granted and concentrate on indoor activities.
• They become introvert , studious and have little interest in outdoor
activities.

16. SIGNS
• Prominent eyeballs.
• Deep anterior chamber.
• Pupils – large and sluggishly reacting to light.
• Fundus- normal to large disc , temporal myopic crescent may be seen.
• Magnitude of error usually – 6 to 8D
• Diagnosis is made by retinoscopy.

17. PATHOLOGICAL MYOPIA
• Also known as progressive or degenerative myopia.
• Starts in childhood at 5-10 yrs of age and results in high myopia
during early adult life.
• Associated with degenerative changes in eye.
• Prevalence: 2-3%

18. ETIOLOGY
HEREDITARY(major role):
• Familial
• More common in Chinese, Japanese, arabs and jews.
• Uncommon in negroes, Nubians and Sudanese.
General growth process(minor role)

20. SYMPTOMS:
Defective vision:
• Error is usually high.
• Uncorrectable visual loss may occur due to progressive degenerative changes.
Muscae volitantes:
• Floating black opacities d/t degenerated liquefied vitreous.
Night blindness:
• Can occur in high myopes having marked chorioretinal degenerative changes.

21. SIGNS:
Prominent eyeballs:
• Elongation mainly affects the posterior pole and surrounding area.
• Part of eye anterior to equator is normal.
Large cornea
Deep anterior chamber
Pupils :large and sluggishly reacting to light.
Magnitude of refractive error:
• Increases by 4D yearly, usually stabilizes at age of 20.
• Occasionally progress until mid 30s resulting in 10-20D ,
may even progress to 30-40D.

22. Fundus examination:
• Optic disc- large, with characteristic myopic
crescent.
Peripapillary crescent encircling the disc may be
present.
A supertraction crescent may be present on nasal
side.
• Degenerative changes in retina and choroid:
Early stage:- tigroid fundus

23. Late stage: changes are more marked in posterior pole.
• Foster-fuch spots
• Cystoid degeneration
• Total chorioretinal atrophy
• Lattice degeneration or snail track lesions.
• Retinal tears, hemorrhage, retinal detachment.

24. Lacquer cracks
Lattice degeneration
Chorio retinal
atrophy

25. Posterior staphyloma- due to ectasia of sclera at posterior pole apparent as
excavation with vessels bending backwards over its margins.

26. Degenerative changes in vitreous:
• liquefaction of vitreous.
• Vitreous opacities.
• Posterior vitreous detachment- Weiss reflex

27. Visual fields:
• Shows contraction.
• Ring scotoma in some cases.
ERG: subnormal due to
chorioretinal atrophy.

28. COMPLICATIONS:
• Retinal tears and detachment.
• Complicated cataract.
• Nuclear sclerosis.
• Vitreous hemorrhage.
• Choroidal hemorrhage and thrombosis.
• Primary open angle glaucoma

29. ACQUIRED MYOPIA:
INDEX MYOPIA:
• Nuclear sclerosis - nucleus becomes more hyper-refringent
myopia.
• Incipient cataract.
• Diabetic myopia- occurs d/t decreases in refractive index of
cortex.

30. CURVATURAL MYOPIA:
• Corneal curvatural myopia- in cases of true increase of
corneal curvature such as keratoconus.
• Lenticular curvatural myopia- due to increase in lenticular
curvature such as anterior and posterior lenticonus
POSITIONAL MYOPIA: anterior subluxation of lens.
CONSECUTIVE MYOPIA:
• Surgical overcorrection of hypermetropias.
• Pseudophakia with overcorrecting IOL.

31. PSEUDOMYOPIA: artificial myopia can occur due to
• Excessive accommodation and spasm of accommodation.
• Full hypermetropic correction in children.
SPACE MYOPIA:
• This condition is seen when the individual has no stimulation for distance
fixation.
• Degree of myopia is never more than 0.75-1.5D

32. NIGHT OR TWILIGHT MYOPIA:
shift from photopic to scotopic vision at twilight
increased sensitivity to shorter wavelengths of light
myopic for shorter wavelengths

33. DRUG- INDUCED MYOPIA:
• Cholinergic drugs- pilocarpine, echothiophate, di-isopropyl fluorophosphate.
• Steroid induced myopia- change in water metabolism of lens.
• Sulphonamides.

34. TREATMENT OF MYOPIA:
OPTICAL TREATMENT OF MYOPIA:
• Prescription of appropriate concave lenses  clear image.
• Basic rule- minimum acceptance providing maximum vision should be
prescribed.
• Modes of prescribing concave lenses:
1. Spectacles.
2. Contact lenses.

35. • In children above 3 years of age:
• Myopia should be corrected fully and instructed to use their glasses
constantly.
• To avoid developing the habit of squinting and to enhance developing a
normal accommodation-convergence reflex.
• Never overcorrect myopia.
• Adults:
• < 30 yrs- accepts full myopic correction.
• > 30 yrs- not able to tolerate full correction over 3D- under correction

36. • Guidelines for correcting high myopia:
• Full correction can rarely be tolerated in case of high
myopia.
• Under correction is always better to avoid problem in near
vision and that of minification of images.

37. A. Kerato Refractive Procedures
1.Incisional refractive techniques
• Radial keratotomy
• Astigmatic keratotomy(AK)
• Hexagonal keratotomy
• Limbal relaxing incision (LRI)
• Opposite clear corneal incision(OCCI)
2.Lamellar corneal refractive
procedures
Freeze keratomileusis
Epikeratophakia
Non freeze keratomileusis
Keratomileusis in situ
Automated lamellar keratoplasty
(ALK)
Small incision lenticule extraction
Corneo plastique
CLASSIFICATION OF REFRACTIVE PROCEDURES

38. 3. Laser ablation corneal procedures
• PRK(Photo refractive keratectomy)
• Laser subepithelial keratomileusis (Lasek)
• LASIK( Laser insitu keatomileusis)
• E-LASIK
• C-LASIK
4. Corneal shrinkage refractive
procedure
• Thermal laser keratoplasty (TLK)
• Conductive keratoplasty (CK)
5.Corneal Implants
Intracorneal contact lenses (ICL)
Intrastromal corneal ring segments
(Intacs)
6.Corneal tissue moulding
B. Lens-based refractive procedures
Phakic refactive lenses (PRL)
Refractive lens exchange(RLE)
C. Combined lens and corneal
refractive procedures :-
Bioptics ,Trioptics

39. PRK
• In PRK a laser is used to remove a thin layer of tissue mechanically
from the surface of the cornea in order to change its shape and refocus
light entering the eye.
• There is a limit to how much tissue can safely be removed .
• So therefore the amount of near sightedness can be corrected .
• Nowadays there is resurgence of surface ablation procedures in the
form of Advanced Surface Ablation (ASA) : d/t
• There utility in thinner corneas
• Avoidance of flap related complications
• Less haze and regression bcoz of adjuvant Mitomycin C .

40. LASIK
• Lasik(Laser in situ keratomileusis) combines precision of excimer
laser photoablation with advantages of an intrastromal procedure that
maintains the integrity of BOWMANS LAYER & overlying corneal
epithelium.
• A section of the outer corneal surface is cut folded back to expose the
inner tissue
• Then a laser is used to remove the precise amount of corneal tissue
needed to reshape the eye
• Then the flap of outer tissues is placed back in position to heal.

41. • The amount of near sightedness that LASIK can correct
is limited by the amount of corneal tissue that can be
removed in a safe manner .
LASIK is used to correct :
• Myopia of < 8D
• Astigmatism of <6D
• Hyperopia of <4D
Laser used are : Excimer laser, solid state UV laser,
infrared femtosecond laser.

44. Visual hygiene :
• To avoid asthenopic symptoms
• Proper posture and adequate illumination.
• The clarity of print should be good.
Low vision aids:
• Indicated in patients with progressive myopia with advanced
degenerative changes.
• Vision cannot be obtained with spectacles and contact lenses.

45. PREVENTIVE MEASURES:
Therapuetic interventions:
• Atropine – 0.01% eye drops at night  slow progression of myopia by
blocking muscarinic receptors of sclera.
• Pirenzepinre 2% gel – twice a day.
• General measures- balanced diet rich in vitamins and proteins
early Mx of associated debilitating disease.
• Genetic counselling.

46. SUMMARY
• Refractive error in which parallel rays of light coming from infinity are
focused in front of the retina when accommodation is at rest.
• SYMPTOMS:- Defective vision, night blindness, floaters etc
• SIGNS :-prominent eye balls, large cornea, deep AC, pupils are large and
sluggishly reacting,
• Fundus – optic disc : large and pale ,myopic crescent.
tigroid appearance, foster-fuch spots, lattice degeneration,
posterior staphyloma.
• Visual fields- contraction or ring scotoma.
• ERG- subnomal

47. CLASSIFICATION
• ETIOLOGICAL
• Axial myopia
• Curvatural myopia
• Positional myopia
• Index myopia
• Myopia d/t excessive
accommodation
• CLINICAL
• Congenital myopia
• Simple/developmental
• Pathological/degenerative
• Acquired
 Consecutive myopia
 Pseudomyopia
 Night myopia
 Drug induced myopia

48. TREATMENT
• Optical treatment- concave lenses
• Surgical treatment
• Preventive measures
• Visual hygiene
• Low vision aids