2. • Short-sightedness
• Parallel rays of light coming from infinity are
focused in front of the retina
when accommodation is at rest
DEFINITION
3. ETIOLOGICAL CLASSIFICATION
Axial myopia
• increase anteroposterior length
Curvatural myopia
• increase curvature of cornea, lens or both
Positional myopia
• anterior placement of lens
Index myopia
• increase refractive index
Myopia due to excessive accommodation
4. OPTICS OF MYOPIA
• Image of distant object on the retina is made up of the circles of
diffusion formed by the divergent beam
• far point of a myopic eye is a finite point between infinity and the
cornea
• from which divergent rays focus on the retina without
accommodation
5. • In emmetropic eye far point is at infinity for myopic eye – finite
distance
• Higher myopia shorter the distance
• Far point is 1 mt. from the eye ,there is 1D of myopia
• Angle alpha- negative resulting apparent convergent squint
6. • a near object situated at the far point is focused without an effort of
accommodation
• Nodal point in a myopic eye is further away from the retina.
• Therefore the image formed will be appreciably larger than it would
be in the emmetropic eye and in spectacle corrected eye
7. • Accommodation in uncorrected myopes -not developed normally
• As they need not accommodate to see near objects clearly.
• may suffer from convergence insufficiency
• exophoria
• early presbyopia as they grow older.
8. Depending upon the age of onset
• Congenital myopia - since birth.
• Youth-onset myopia - under the age of 20 yrs (simple myopia).
• Early adult onset myopia - between 20- 40 yrs of age (acquired index
myopia due to early nuclear sclerosis).
• Late adult onset myopia - >40 years of age (acquired index myopia
due to age related nuclear sclerosis).
9. CLINICAL TYPES OF MYOPIA
• Congenital myopia
• Simple or developmental myopia
• Pathological or degenerative myopia
• Acquired myopia.
10. CONGENITAL MYOPIA
• ↑ axial length & globe size
• Premature babies
• -Marfan's syndrome -Homocystinuria
• Since birth, diagnosed at age 2-3 years
• High error 8-10 D, remain constant
• Bilateral- difficulty in distant vision, hold things very close
• If unilateral, as anisometropia, may develop amblyopia
11. Associated conditions
• Convergent squint
• Cataract
• Microphthalmos
• Aniridia
• Megalocornea
MANAGEMENT
• Early Correction is desirable
• Retinoscopy under full cycloplegia
• Early full correction desirable
• Poor prognosis
12. SIMPLE MYOPIA
• Developmental / Physiological myopia
• Not associated with any disease of the eye
• Onset (8-12 yrs) school myopia
ETIOLOGY
• Axial type
physiological variation in length of eyeball
precocious neurological growth during childhood.
13. • Curvatural type
due to underdevelopment of the eyeball.
Role of genetics
both parents myopic (20%)
one parent myopic (10%)
no parent myopic (5%)
• Inheritance - autosomal dominant.
• recessive mode of inheritance is more common.
14. • Role of diet in early childhood
• Theory of excessive near work in childhood
myopia is aggravated by close work, watching television, smart
phone, computer and by not using glasses
15. • Clinical course
Begins (7-10 yrs) ↑ during growth stabilises by 21 yrs (not > -6 D)
SYMPTOMS
Poor vision for distance
Half shutting of eyes
Asthenopic symptoms
16. SIGNS
Predominant eyeballs
Deep AC
Pupil – large & sluggish reaction to light
Fundus – normal ; temporal myopic crescent
Error: 6-8 D
Diagnosis – confirmed by retinoscopy
18. ETIOLOGY
• Rapid axial growth of the eyeball outside normal biological variations
• Role of heredity linked retinal growth
• Role of general growth process (nutritional, hormonal, debilitating
disease)
19.
20. SYMPTOMS
• Defective vision
• Muscae volitantes / floating black opacities
• Night blindness marked chorioretinal changes
21. Signs
• Prominent eyes
• Large cornea
• AC deep
• Pupils large and react sluggishly to light.
• refractive error increases – 4D/yearly
• stabilises at 20 yrs
• May progress to 30-40 D
22. Optic disc
• Elongation separation of retina & choroid from temporal margin of
disc sclera seen as white area : MYOPIC CRESCENT
• on nasal side – retina extends over edge of disc : SUPERTRACTION
CRESCENT
23. • Generalised atrophy – retina &choroid
• tigroid appearance of the fundus
• atrophy of retinal pigment epithelium visible
prominent large choroidal vessels
24. • Patches of choriodal atrophy
• later stages - total disappearance of choroidal tissue
• white atrophic patches due to visible sclera
• with heaping up of pigment around them.
• more marked at the posterior pole.
25. • Lattice degeneration
• Lacquer cracks
ruptures in the RPE–Bruch membrane– choriocapillaris complex
characterized by fine irregular yellow lines criss-crossing
at the posterior pole
5% of highly myopic eyes
be complicated by CNV
26. Subretinal ‘coin’ haemorrhages
• may develop from lacquer cracks
• in the absence of CNV.
Foster - Fuchs spot
• raised, circular, pigmented lesions
• at macula
• develops after a subretinal haemorrhage
has absorbed
28. • Staphyloma
• about a third of eyes
• peripapillary or macular ectasia of the posterior sclera
• due to focal thinning and expansion myopia.
• as an excavation with vessels bending backward over its margins
29. (Peripapillary) intrachoroidal cavitation
• peripapillary detachment of pathological myopia (PDPM)
• occur adjacent to the nerve, inferiorly
• small yellowishorange peripapillary
• area typically inferior to the disc.
• Visual field defects are common and frequently mimic glaucoma.
30. Degenerative changes in vitreous
• Liquefaction
• vitreous opacities
• posterior vitreous detachment - appearing as Weiss reflex
• not comparable with the degree of myopia
32. COMPLICATIONS
• retinal tears and retinal detachment may occur.
• Complicated cataract.
due to an aberration of lenticular metabolism.
• Nuclear sclerosis - is common in myopics.
• Vitreous haemorrhage.
accompanies a retinal tear.
• Choroidal haemorrhage and thrombosis
33. • CNV
• 10% of highly myopic
• prognosis is better
• Anti-VEGF - treatment of choice. The injection frequency may be less
than that for AMD
• risk of RD higher
35. ACQUIRED MYOPIA
Index myopia
• Nuclear sclerosis
• Incipient cataract
• Diabetic myopia occurs due to a decrease in the refractive index of
cortex
Curvatural myopia
• may be corneal ectasias keratoconus.
• Lenticular curvatural myopia
• lenticonus anterior and posterior.
36. • Positional myopia
anterior subluxation of the lens.
• Consecutive myopia
Surgical overcorrection of hypermetropias
Pseudophakia with overcorrecting IOL
• Pseudomyopia/artificial myopia
Excessive accommodation
Spasm of accomodation
37. • Space myopia
• when the individual has no stimulation for distance fixation.
• eyes tend to choose a near fixation plane which can be very variable.
• degree of myopia due to this is never > 0.75- 1.5 D
• aviators when flying in cloud / fog / at night.
• Night myopia
• shift from photopic to scotopic vision is associated with increased
sensitivity to shorter wavelengths of light.
• emmetropic eye if accommodated for middle range of visual
spectrum - will be slightly myopic for shorter wavelengths
38. • Drug induced myopia
• Cholinergic drugs - pilocarpine, echothiophate and di-isopropyl
fluorophosphate
• Steroid induced myopia - water metabolism changes involving lens.
• Sulphonamides - slight changes in RI of the media
40. • Contact lenses - cases of high myopia
• avoid peripheral distortion and minification produced by strong
concave spectacle lens
• hard contact lenses may slow down progress of myopia.
• full contact lens correction- needs more accommodation for near
work
• develop presbyopia comparatively earlier
41. • Low degree (upto -6 D) young adults – never be overcorrected
full correction – constant use
• For correcting high myopia
• full correction not tolerated in high myopia (> –10 D).
• Undercorrection - better to avoid problem of near vision &
minfication of images
43. PREVENTIVE MEASURES
• THERAPEUTIC INTERVENTIONS
• ATROPINE
• 0.01% e/d instilled nightly- prevent progression of myopia
• by blocking the muscarinic receptors of sclera
• with minimum side effects.
• mydriasis and cycloplegia -some concern.
• ATOM 1 & ATOM 2
• LAMP study
44. • PIRENZEPINE 2% GEL
• twice a day - prevent myopia progression
• selective for the m1 muscarinic receptors
• less likely to produce mydriasis and cycloplegia than atropine
• Genetic counselling
45. GENERAL MEASURES
• balanced diet rich in vitamins and proteins
• early management of associated debilitating disease
• proper posture
• adequate illumination during close work
• Low vision aids
