This document discusses different types of refractive errors including emmetropia, ametropia, myopia, hypermetropia, and astigmatism. It provides details on: - The definition and normal state of emmetropia - Causes, symptoms, diagnosis and treatment options for myopia and hypermetropia such as prescription lenses, contact lenses, and refractive surgery - Types of myopia including simple, pathological, and congenital myopia - Causes of refractive errors like abnormal eyeball length, corneal or lens curvature, or refractive index - Potential complications of high degrees of myopia like macular degeneration and retinal detachment

1. Refractive Errors
& Their Management
Asim Abhas swain
NIMS UNIVERSITY,RAJASTHAN

2. EMMETROPIA
 It is a condition in which parallel rays of light come from infinity focused on the
retina(fovea),when accommodation is at rest.
 It is a normal state where refractive error is not present or optically normal eye.
 In otherwords, there is no required of any refractive correction in this condition.

3. EMMETROPIZATION
 From 3 to 14 years of age,the axial length increases further by 1mm & the power
of the crystalline lens changes to achieve and maintain emmetropia.
 This entire process from birth onwards is called as “Emmetropization”.
 Components influencing emmetropization ;
(1) Corneal power
(2) Crystalline lens power
(3) Axial length
(4) Anterior Chamber Depth

4. AMETROPIA
 It is a condition in which parallel rays of light come from infinity focused either
infront or behind the retina,when accommodation is at rest.
 Ametropia occurs due to ;
(i) abnormal lenghth of the eyeball [ axial ametropia ]
(ii) abnormal curvature of the cornea or crystalline lens [ curvatural ametropia ]
(iii) abnormal refractive indices of the media [ index ametropia ]
(iv) abnormal position of the crystalline lens [ dislocation of lens ]
 There are three types of refractive errors ;
~ Myopia
~ Hypermetropia
~ Astigmatism

5. MYOPIA
 It is also called as Short sightedness or Nearsightedness.
 It is a condition in which parallel rays of light come from infinity focused in
front of the retina, when accommodation is at rest.
 In this condition, near objects looks cleared,but distance objects looks
blurred.

6. SYMPTOMS OF MYOPIA
 Blurred of distance vision
 Headache
 Eye strain
 Eye Fatigue
 Occasional Watering
SOMEONE MAY HAVE MYOPIA IF
 Have trouble reading to the blackboard at school
 Moves very close to the TV or movie screen
 Difficulty in seeing road signs & faraway objects while driving

7. ETIOLOGY
 AXIAL MYOPIA : When the antro-posterior length of the eyeball is more than
normal.( 1mm axial length elongation will cause = -3.00 DSph )
 CURVATURAL MYOPIA : When the curvature of the cornea or crystalline lens is
more than normal. ( 1mm steepening will cause = -6.00 Dsph )
 INDEX MYOPIA : When the refractive index of the of the crystalline lens is more
than normal.
 POSITIONAL MYOPIA : Anterior displacement of the crystalline lens,i.e. Trauma
 MYOPIA DUE TO EXCESSIVE ACCOMODATION : Patients with excessive
accommodation means Pseudo myopia (fake myopia) is an inability to see clearly
in the distance, because the focusing muscles are unable to relax completely.

8. CLINICAL TYPES OF MYOPIA
 Congenital or developmental Myopia
~ It is very rare
~ This type of myopia generally present at birth
~ May be upto -10.00D at birth.
~ Its progression is quite rare.
~ In this cases choroidal sclerosis,hypopigmentation & myopic crescent are seen
in fundus.
 Simple Myopia
~ It is the most common type of myopia
~ Progress during childhood & adolescence
~ Usually upto 5 to 6 Dioptres
~ Generally stops to progress by the age of 21 years
~ Best corrected visual acuity is 6/6 in this condition
~ In this cases fundus may show myopic cresent at the temporal margin of the
disk

9. Continue..
 Acquired Myopia
 It may be found following trauma to ocular structures,intra ocular lens(IOL)
implantation(over correction of aphakia).
 Administration of certain drugs like acetazolamide,tetracycline,oral
contraceptives,etc.
 Pathological or degenerative Myopia
 Also called as Malignanto Myopia.
 Generally hereditary & more common in women.
 This type of error rapidly increases during growth period & may reach 20-30D by
the age of 25 years.
 Pathological myopia has been linked to genes 18p11.31 & 12q2123.
 pathological curvature myopia is ideally seen in Keratoconus.
 In pathological myopia,the eyes are unusually prominent with slightly dilated
pupils.

10. DIAGNOSIS
 It can be easily diagnosed during a complete comprehensive eye examination by
an Optometrist & Ophthalmologist.
 During refraction procedure, retinoscopic exam & autorefractometry give a vast
details about myopia.
TREATMENT
[1] PRESCRIPTION EYEWEAR OR OPTICAL LENSES
~ Concave or minus (-) lens is prescribed for myopic correction.
~ It is the most common & acceptable treatment option for myopia.
~ Myopia should never be over-corrected.
~ Weakest possible concave lens with which the patient maintains normal vision(6/6)
is prescribed for constant wear.

11. Rough Estimate Of VA in Myopia
-0.50 6/9-6/12
-1.00 6/18
-1.50 6/24
-2.00 6/36
-3.00 6/60
-4.00 4/60
-5.00 3/60
-6.00 2/60
Degree Of Myopia Rough Estimate of VA

12. [2] CONTACT LENS
 It is an another option for myopia management.
 It give a wider field of vision than glasses.
 These are applied directly to the corneas of the eyes.
 The eye’s natural tears give contact lenses their ability
to float on the cornea.
 Like prescription glasses,contact lenses are also
customizable for different prescriptions.
[3] SURGICAL TREATMENTS
 Refractive surgery is the term used to describe surgical procedures that correct common
visual problems.
 Currently a laser procedure called LASIK(Laser assisted in situ keratomileusis) is most
popular & acceptable.
 This technique used for the correction of myopia between 1 to 9 Dioptre.
 Other surgical options like Radial Keratotomy & Photorefractive Keratectomy,Phakic
lens implantation are also available.

13. OTHER MYOPIA MANAGEMENT OPTIONS
ATROPINE EYE DROP
 Now-a-days Atropine is the most effective therapy for myopia control.
 A low dose of Atropine(0.01%) can significantly slow the progression of myopia in
children.
ORTHOKERATOLOGY(Ortho-k)
 It is the process in which custom made
gas permeable lenses are worn overnight.
 It temporarily reshape the cornea.
~ The lenses work by flattening the center
of cornea.
 When these lenses are removed,the cornea
stays flattened for a while & vision is corrected
without the need of any glasses.
INTACS/CORNEAL RINGS
 These are implanted into the eye to alter the shape of the cornea.
 These are designed for permanent placement in the eye.
 Approved for the correction upto -3.50D .

14. COMPLICATIONS
 Myopia has been associated with complications,such as;
1) Myopic Macular Degeneratin[MMD]
2) Retinal Detachment[RD]
3) Cataract
4) Open Angle Glaucoma[OAG]
 These complications can lead to irreversible visual impairment later in life.

15. HYPERMETROPIA
 It is also called as Hyperopia,Farsightedness or Longsightedness.
 It is a condition in which parallel rays of light come from infinity focused behind
the retina(fovea),when accommodation is at rest.
 In this condition, distance objects looks clear bur near objects looks blurred.

16. SYMPTOMS OF HYPERMETROPIA
 Blurring of Near Vision
 Headache
 Eye Strain
 Eye Fatigue
 Occasional watering
N.B. Fatigue or headache after some close-up work such as reading.
ETIOLOGY
 AXIAL HYPERMETROPIA : When the antero-posterior lenth of the eyeball is shorter
than normal.
 CURVATURAL HYPERMETROPIA : When the curvature of the cornea or crystalline
lens is flatter than normal.
 INDEX HYPERMETROPIA : When the refractive index of the crystalline lens is less
than normal.

17. Continue…
POSITIONAL HYPERMETROPIA : A backward dislocation of the lens produces
hypermetropia.
APHAKIA : Absence of the crystalline lens is an example of high degree of
hypermetropia.
CONSECUTIVE HYPERMETROPIA : Due to surgically overcorrected myopia.
CLINICAL TYPES OF HYPERMETROPIA
SIMPLE HYPERMETROPIA :
~ It is the common type of hypermetropia.
~ It may be hereditary.
~ It includes axial & curvatural hypermetropia due to biological variations in the
development of the eye.
PATHOLOGICAL HYPERMETROPIA :
~ Results due to either congenital or acquired conditions of the eyeball.
~ It includes,Index,positional,aphakia(Positional) & consecutive hypermetropia.
FUNCTIONAL HYPERMETROPIA :
~ Results from paralysis of accommodation as seen in patients with third nerve palsy.

18. DIAGNOSIS
 The Optometrist or an Ophthalmologist can diagnose hypermetropia during
comprehensive eye check-up.
 By using retinoscope & refraction technique doctor measures the amount of
hypermetropia in the eyes.
TREATMENT
(1) PRESCRIPTION EYEWEAR & OPTICAL LENSES
~ Convex or plus(+) lenses are used to treat the
hypermetropic eyes.
~ It is most useable & safest method for treatment.
~ In young children with hypermetropia,examination should be conducted under
cycloplegic.
~ In young patients with active accommodation,hyperopia should be undercorrected.
~ But in advanced age,when all the manifest hypermetropia becomes absolute &
accommodation is poor,then full correction is advised.

19. (2) CONTACT LENS
 Contact lenses are often prescribed in unilateral hypermetropia(anisometropia) to
avoid diplopia & amblyopia.
 For cosmetic resons,contact lenses should be prescribed once the prescription has
stabilized.
 These lenses increased field of vision than glasses.
(3) SURGICAL CORRECTION
LASIK :
 It is a laser surgical procedure that produces steepening of the central cornea.
 It corrects the hypermetropia up to 4D.
LASER THERMAL KERATOPLASTY :
 Holmium laser is used in this procedure.
 This is an infrared laser that shrinks the corneal stromal collagen fibers for
reshaping the cornea.
CONDUCTIVE KERATOPLASTY : ~ This procedure preferred over LASIK & PRK,due to
its better safety margin.
~ It is a painless procedure that involves neither cutting nor removal of tissue.
~ Generally recommended for the treatment of mild to moderate hypermetropia
ranges between +0.75D to +3.00D .

20. Continue…
KERATOPHAKIA :
 It is a procedure in which a donor corneal lenticule is placed into intralamellar
pocket fashioned in the corneal stroma.
INTRAOCULAR LENS IMPLANTATION :
 It is a method to correct of aphakic hypermetropia.
COMPLICATIONS
 Amblyopia
 Accomodative convergent squint
 Development of primary narrow angle glaucoma
 Recurrent styes,blepharitis & chalazion due to frequent rubbing of the eye.

21. ASTIGMATISM
 It is a condition in which parallel rays of light come from infinity doesn’t focus on a
point due to refraction varies in different meridians,when accommodation is at rest.
SYMPTOMS OF ASTIGMATISM
~ Distorted or blurred vision at all distances
~ Headache
~ Squinting eyes
~ Eye irritation
~ Difficulty in seeing at night
~ Head tilt in oblique astigmatism in children

22. ETIOLOGY
CORNEAL ASTIGMATISM : Also called as Curvatural astigmatism that happens when the
cornea is misshapen.
LENTICULAR ASTIGMATISM : Also called as Index astigmatism that happens when the
crystalline lens is misshapen or due to inequalities in the refractive index of different
sectors of the lens.
POSITIONAL ASTIGMATISM : Due to oblique placement of IOL occasionally or traumatic
subluxation of the lens.
RETINAL ASTIGMATISM : Due to oblique placement of macula may also be seen
occasionally.
TYPES OF ASTIGMATISM
(1) REGULAR ASTIGMATISM
The two principle meridians are at right angles & are therefore susceptible to
correction
~ With the rule astigmatism
~ Against the rule astigmatism
~ Oblique astigmatism
~ Bi-oblique astigmatism

23. (IRREGULAR ASTIGMATISM)
 In irregular astigmatism, the principal meridians are separated by any angle other than
90 degree ,i.e. they are not perpendicular to each other.
 In this type,the curvature at each meridian is not uniform but changes from one point
to another across the entrance of the pupil.
 Cannot be corrected adequately by spectacles.
TYPES OF REGULAR ASTIGMATISM
1 WITH THE RULE ASTIGMATISM
 In this type,the two principal meridia
are placed at right angles to one another,
but the vertical meridian is more curved
than the horizontal.
 That means the greatest refractive power is at 90 degree(+/-20 degree)
 Corrected by Convex cylinder at 90degree(+/-20 degree) or concave cylinder at 180(+/-
20 degree).

24. 2 AGAINST THE RULE ASTIGMATISM
 In this condition, the horizontal meridian
is more curved than the vertical meridian.
 That means the greatest refractive
power is at 180degree(+/-20degree).
 Corrected by convex cylinder at
180 degree(+/-20degree) or concave
cylinder at 90degree(+/-20degree).
3 OBLIQUE ASTIGMATISM
 The two principal meridian are not
horizontal or vertical though they
are at right angle to each other.
4 BI-OBLIQUE ASTIGMATISM
 The two principle meridians are not at
right to each other but are crossed obliquely.

25. Regular Astigmatism can furter be classified as ;
SIMPLE ASTIGMATISM
 One of the foci falls upon the retina while
the other falls infront of or behind the retina.
COMPOUND ASTIGMATISM
 Neither of the foci fall upon the retina but
both are placed in front of or behind the retina.
MIXED ASTIGMATISM
 One focus is in front of the retina while the
other is behind so that the refraction is
hypermetropic in one direction & myopic in
the other direction.

26. DIAGNOSIS OF ASTIGMATISM
 Eye care professionals like Optometrists & Ophthalmologists diagnosed astigmatism by
comprehensive eye examination.
 Through three primary tests like visual acuity,refraction & keratometry, doctor
determine this.
 With the current technological advances,the diagnosis of astigmatism is becoming more
accurate by help of the equipment called Corneal topography that measures the shape
& curvature of the cornea.
 Astigmatic fan test,Fogging technique using astigmatic fan is a sensitive test for finding
out the astigmatism.
 JCC or Jackson Cross Cylinder is very useful in confirming the power & axis of
cylindrical lenses.
TREATMENT OF REGULAR ASTIGMATISM
OPHTHALMIC CONTACT LENS/PRESCRIPTION EYEGLASS
 Prescribing Appropriate cylindrical lenses after accurate refraction.
 Toric soft contact lenses or toric rigid gas permeable contact lenses are used for higher
degrees.
 Hard contact lenses may correct upto 2-3D of regular astigmatism.

27. GUIDELINES FOR OPTICAL CORRECTION
 Small astigmatism like 0.5 or less should be treated only if there is visual
deterioration or asthenopic symptoms.
 High astigmatism should be fully corrected.
 Change in the axis of the lenses in patients used to the previous axis should be done
cautiously.
 New astigmatism correction in adults is not tolerated.In such cases it is better to
undercorrect & give full correction gradually.
 Bi oblique astigmatism,mixed & high astigmatism are better treated by contact
lenses.
 Spherical component should also be correct.

28. SURGICAL CORRECTION FOR ASTIGMATISM
(1) ASTIGMATIC KERATOTOMY
 Transverse keratotomy.
 Accurate keratotomy incisions are placed in the cornea at 7mm optical zone to the
steepest corneal meridian.
 Can correct upto 4-6D of astigmatism.
(2) LIMBAL RELAXING INCISIONS
 Incision is given at the limbus.
 Correct -1 to -2D of astigmatism.
(3) ASTIGMATIC LASIK
 This procedure can corrects the astigmatism upto 6-8D.
 Wave front guided C-LASIK is presently the best technique to take care of the post
keratoplasty astigmatism.
(4) INTRAOCULAR LENS
 Angle supported AC phakic IOL
 Toric inta ocular implant

29. TREATMENT OF IRREGULAR ASTIGMATISM
 Spectacles though may not provide full correction some amount of correction can be
attempted.
 Prescribing contact lenses which replace the anterior surface of the cornea for
refraction.
 Surgical correction by Phototherapeutic Keratectomy(PTK) or Keratoplasty.
ISOMETROPIA
 The condition in which both eyes have same or equal refractive power.
ANISOMETROPIA
 It means that the two eyes have a
different refractive power.
 In otherwords, there is unequal focus
between the two eyes.
 This is often due to one eye having slighty
different shape or size from the other causing
asymmetric curvature(astigmatism),asymmetric
hypermetropia or asymmetric myopia.

30. Continue…
 It is the most common causes of Amblyopia or Lazy eye.
 Individuals with untreated anisometropia may experience ;
> Poor depth perception
> Headaches
> Dizziness
> Nausea
> Visual discomfortness
DIAGNOSIS
 Retinoscopy examination
 Testing for state binocular vision
~ Friend Test
~ Worth’s Four Dot Test
FRIEND

31. TREATMENT
 Glasses
 Contact Lenses
 Anisometropic spectacle
 Phakic refractive lenses
 Refractive lens exchange
PRESBYOPIA
 Presbyopia is not a refractive error but an age related condtion that affects generally
after 40years.
 But the symptoms of hypermetropia or presbyopia are similar,often involving
problems with near vision.
 It occurs when your the eye lens loss its flexibility & became hard or its due to
insufficiency of accommodation.

32. DIAGRAM
DIAGNOSIS
Presbyopia is diagnosed by a basic comprehensive eye examination which
includes a refraction assessment.

33. TREATMENT
BIFOCAL LENSES
~Used for both Near vision
& Distance Vision.
TRIFOCAL LENSES
~It has two lines on the
lens that separates the
lens into three distinct Prescriptions.
~corrects 3 types of
Vision like close,intermediate & distance.
PROGRESSIVE LENSES
~Also called as no line multifocal
lenses that looks exactly as single
vision lenses.
~In other words,these
lenses will help one to see clearly at
all distances like near/close,intermediate
& also distance.

34. According to Donder’s Age Related
Estimated Correction

35. CONTACT LENSES
 Some people prefer to use contact lenses rather than eyeglasses.
 Generally,there are 2 types of contact lenses that helpful in presbyopia.
Monovision Contact lens
In these type correct one eye for distance vision & the other for closeup vision.
Multifocal Contact lens
These lenses have several rings or zones set at different powers.
SURGICAL CORRECTIONS
 Scleral Ciliary surgery
~Incisional
~Segments,bands
 Presby-LASIK
 Inta corneal lays
 Multifocal IOL

36. ------THANK YOU-------