I am Optometrist Surendra Prasa Sah (M.OPTOM).

1. REFRACTIVE ERRORS
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2. EMMETROPIA
 The parallel rays of light coming from infinity are focused at
sensitive layer of retina with the accommodation at being at
rest
 Good visual acuity (6/6 or better) at 6 m testing distance
 If accommodation amplitude is adequate ,equally good visual
acuity at the near testing distance of 40 cm
 Axial length =24mm
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3. CONT
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4. Refractive sate of eye
 Corneal refractive power
 Anterior chamber depth
 Lens refracting power
 Axial length
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5. AMETROPIA
 The parallel rays of light coming from infinity are focused
either in front or behind the sensitive layer of retina in one or
both meridian when accommodation at rest
 Refractive Status And Aging
o Hyperopic (infant)
o Emmetropic (10 years old)
o Myopic (25 years old)
o Hyperopic (60 years old)
o Less hyperopic (80 years
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6. TYPES OF REFRACTIVE ERRORS
Hypermetropia
Myopia
Astigmatism
Aphakia
pseudophakia
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7. HYPERMETROPIA
 The parallel rays of light coming from infinity are focused
behind the sensitive layer of retina with accommodation
being at rest
 Back focal point is behind retina
 It is also called far/long sightedness
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8. AETIOLOGY
Axial hypermetropia:-the antero-posterior diameter of
eye is too short & retina is too near to optical system,1mm-3D
Curvature hypermetropia:-curvature of cornea or
lens may be too small,1mm-6D
Index hypermetropia:- due to change in refractive
index of lens ,aqueous humour ,vitreous humour or diabetes
Positional hypermetropia:-if the crystalline lens is
dislocated backwards
Absence of crystalline lens:- aphakia
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9. CLINICAL TYPES
simple hypermetropia:- normal biological variations in
development of eyeball
Pathological hypermetropia:-outside biological
variations of development ,include:-
 Senile :- curvature &index
 Positional
 Aphakia
Functional hypermetropia:-paralysis of
accommodation -third nerve paralysis &internal
ophthaloplegia
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10. OPTICAL CONDITION
 Parallel rays of light come to a behind the retina
 Parallel rays of light are brought to a focus upon the
retina by increasing the refractivity by
accommodation .the normal lens becomes more
convex
 Parallel rays of light are brought to a focus upon the
retina by increasing refractivity by a convex
spectacles lens .the degree of hypermetropia is given
by power lens
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11. ACCOMMODATION IN HP
 Latent hypermetropia (LH):-
 This is a condition in which all or part of hypermetropia is compensated or corrected by
the tonicity of the ciliary muscle.
 Latent hypermetropia becomes manifest when the amplitude of accommodation
decreased significantly.
 Manifest hypermetropia (MH): It has two parts.
 Facultative hypermetropia (fH) – The amount of hypermetrropia that can be
corrected by the effort of accommodation.
 Absolute hypermetropia (aH) – T he amount of hypermetropia that can not be
corrected by the effort of accommodation.
 Thus the total amount of hypermetropia (tH) is the sum of
latent and manifest hypermetropia.
tH=LH+MH=LH+(fH+aH).
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12. CLINICAL PATHOLOGY
 Cornea is small, AC shallow ,closed –angle glaucoma
 Administration of dilated drugs to dilate pupil
 Developmental aberrations such as colobomata
,microphthalmos
 The retina appears to have peculiar sheen, optic neuritis,
vascular reflex
 Face asymmetrical ,dislocation of macula, divergent squint
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13. CLINICAL FEATURES
 SYMPTOMS:-
 Asymtomatic
 Asthenopic :-tiredness, frontal or frontotemporal headache, watering, mild
photophobia
 Defective vision with asthenopic symptoms
 Defective vision only
 The effect of ageing on vision
 Intermitted sudden blurring of vision
 Crossed – eye sensation
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14. CONT
Signs:-
 Size of eyeball may be normal or small as whole
 Cornea may smaller than normal
 Variation in visual acuity
 Abnormal branching of vessels , swelling of disc, retinal shine is
more than normal
 A –scan ultrasonography may reveal a short anteroposterior length
of eyeball
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15. COMPLICATION
Recurrent styes, blepharitis or chalazia
Accommodative convergent squint
Amblyopia
Predisposition to develop primary narrow
angle glaucoma
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16. TREATMENT
OPTICAL TREATMENT:-CONVEX(PLUS) LENS
 Total amount of HP-complete cycloplegic
 Manifest refractive error is small-1D or less
 Astigmatism should be fully corrected
 Exophoria -1-2D less
 Accommodative convergent squint /amblyopia-full correction
Surgery for Hp:-
 Thermokeratoplasty
 The use of excimer &Holmium lasers is under investigation
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17. APHAKIA
 Condition in which absence of crystaline lens from
pupillary area of eye
CAUSES:-
 Congenital absence of lens
 Surgical aphakia occurring after removal of lens
 Aphakia due to absorption of lens matter
 Traumatic extrusion of lens
 Posterior dislocation of lens in vitreous
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18. OPTICS OF APHAKIA
 Changes in cardinal data of the eye
 Image formation in the aphakic eye
 Visual acuity in aphakia
 Accommodation in aphakia
 Binocular vision
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19. CLINICAL FEATURES
SYMPTOMS:-
 Defective vision for near & distance
 Erythropsia and cyanopsia – due to entry of infrared and ultraviolet rays in
the absence of the crystalline lens
SIGNS:-
 Limbal scar in case of surgical aphakia
 Deep anterior chamber
 Iridodonesis – tremulousness of the iris due to loss of support of
lens
 Jet Black pupil
 Loss of 3rd and 4th purkinje images
 Fundus examination reveals a small hypermetropic fundus
 Retinoscopy shows high hypermetropia
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20. TREATMENT
SPECTACLES:-
 Spectacles should be prescribed with about +10D lens for
correction of aphakia
 It should also include correction for surgical astigmatism and
+3-4D for near vision
 Nowadays spectacles are not preferred for use in aphakia due
to its many disadvantage
 Advantages of using spectacles in aphakia
• Easy to use
• No complications
• cheap
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21. CONT…..
 Disadvantages
The images are magnified – about 30% – hence not useful in unilateral
aphakia as it causes diplopia
• The field of vision in decreased considerably
• Spherical and chromatic aberration of high power lenses
• Roving ring scotoma (Jack in the box phenomenon)
• Prismatic effect of the thick lenses
• High power are cosmetically not acceptable
Contact lenses
Advantages over spectacles:
• Produces less magnification
• Better field of vision
• Less chromatic and spherical aberration
• No prismatic effect
• Cosmetically more acceptable
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22. CONT……
Intraocular lens implantation
• The lens can be implanted in the capsular bag or in the anterior chamber
• It eliminates most of the disadvantages associated with the use of spectacles
or contact lenses
• Disadvantage include the complications associated with surgery
Refractive surgery
 Keratophakia
– a lenticule prepared from the donor cornea is placed within the
lamellae of the patient’s cornea
 Epikeratophakia
– a lenticule prepared form the donor cornea is stitched to the
patients cornea after removing the epithelium
 Hyperopic Lasik
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23. PSEUDOPHAKIA
 The condition of aphakia when corrected with
implantation of an IOL
Refractive status:-
 Emmetropia
 Consective myopia
 Consective ypermetropia
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24. SIGNS
 Surgical limbal scar may be seen
 Anterior chamber is slightly deeper than normal
 Mild iridodonesis of iris may be demonstrated
 Purkinje image test shows fours images
 Pupil is blackish in colour but when light thrown in pupillary
area shining reflexes are observed
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25. MYOPIA
 Shortsightness
 Lengthening of posterior part of eye
 The parallel rays of light coming from infinity are focused in
front of sensitive layer of retina when accommodation is at
rest
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26. AETIOLOGY
Axial myopia:-the antero-posterior diameter of eye is too
long & retina is too far from optical system
Curvature myopia:-the curvature of cornea or lens may
be too great
Positional myopia:-if lens is dislocated forwards
Index myopia:-R.i of aqueous is too high ,vitreous is too
low or lens is too high
 Myopia due to excessive accommodation occurs in patients
with spasm of accommodation
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27. OPTICS OF MYOPIA
 Optical system of a myopic eye is too powerful for its axial length
 Image of distance object on retina is made up of circles of diffusion
formed by divergent beam
 Far point of the myopic eye is a finite point in front of the eye
 Nodal point in myopic eye is further away from retina
 Angle alpha of eye may be negative
 Accommodation in uncorrected myopes is not developed normally
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28. CLINICAL VARIETIES OF MYOPIA
 Congenital myopia
 Simple or developmental myopia
 Pathological or degenerative myopia
 Acquired myopia
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29. CONGENTICAL MYOPIA
The child is born with elongated eyes
The refraction may be upto -10D
Typical fundus changes are seen
Progression is rare
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30. SIMPLE MYOPIA
 Commonest clinical type
 Does not progress much after the adolescence
 May be upto -5 to -6D
 No degenerative changes are seen in the fundus, although
peripheral retinal degeneration may be seen in later life
 Associated with good vision with a good prognosis
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31. PATHOLOGICAL MYOPIA
 It is also called progressive or degenerative myopia
 Myopia appears in childhood &increasing steadily with age upto 25
years or beyond
 The final amount of myopia may be -15Dto -25D or more
 There are typical degenerative changes in the fundus
 Strongly hereditary & more common in female
 Prognosis is usually poor
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32. ACQUIRED MYOPIA
CAUSES :-
 Index myopia
 Curvatural myopia
 Positional myopia
 Consecutive myopia
 Pseudomyopia
 Space myopia
 Night myopia
 Drug –induced myopia
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33. CLINICAL FEATURS
SYMPTOMS:-
 Impaired distance vision
 Eye –strain
 Exophoria or divergent squint
 Delayed dark adaptation
 Sudden loss of vision
 Black floaters
SIGNS:-
 Prominent eyeball, large cornea, deep anterior chamber& a
large pupil, apparent convergent squint, degeneration of
vitreous
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34. COMPLICATION OF MYOPIA
Retinal tear –vitreous haemorrhage
Retinal detachment degeneration of the
vitreous
Primary open –angle glaucoma
Posterior cortical cataract
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35. TREATMENT
Divergent or minus lenses in spectacles or
contact lenses
Cycloplegics
Surgery
Refractive surgery
General hygiene
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36. ASTIGMATISM
 Condition of refraction wherein a point focus of light cannot
be formed upon the retina
 Caused by unequal refraction of light in different meridians
 Curvatures of both axes are unequal & too small is HM ASG &
both unequal & too great is MP ASG
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37. AETIOLOGY
Corneal astigmastism :-abnormalites of curvature of
cornea
Lenticular astigmatism:-
• Small amount of curvature astigmatism due to congenital abnormalities of
curvature of lens
• Position astigmatism due to congenital or traumatic subluxation of lens
• Refractive index of lens in different median
Retinal astigmatism due to oblique placement
of macula
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38. TYPES OF ASTIGMATISM
REGULAR ASTIGMASTIM:-Axis & angle
 With –the –rule :-two principal meridian are placed at right
angles to one another but vertical meridian is more curve
than horizontal
 Against –the rule :-horizontal meridian is more curved than
vertical meridian
 Oblique:-two principal meridian are not horizontal & vertical
@ right angle to one another
 Bi-oblique:-two principal meridian are not @ right angle to
each other
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39. CONT..
REGULAR ASTIGMATISM:-REFRACTIVE TYPES
 Simple:-one meridian focus in front & other behind retina
 Compound :-ray of light in both meridian are focused either
in front or behind retina
 Mixed:-rays of light in one meridian are focused in front &
other behind retina
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40. OPTICS OF REGULAR ASTIGMATISM
 Parallel rays of light are not focused on a point but form two
focal lines
 The configuration of rays refracted through astigmatism
surface is called sturm’s conoid& distance between two lines
is called focal interval of sturm
 The length of this focal interval is a measure of degree of
astigmatism
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