The document discusses the various types of refractive errors, specifically focusing on emmetropia and hypermetropia, their causes, classifications, symptoms, and treatment options. It explains the differences between normal and pathological hypermetropia and highlights the impact of age on vision quality. Additionally, treatment methods such as optical approaches (spectacles and contact lenses) and surgical interventions (like LASIK) are covered.

1. ERRORS OF REFRACTION

2. EMMETROPIA
State of refraction where parallel rays of light
coming from infinity are focussed at the sensitive
layer of retina with accommodation being at rest

3. Normal variation with age
• Eyeball is relatively short
• +2 to +3D hypermetropia is present which
gradually reduces
At birth
• Eye is emmetropic and remains so till the
age of about 50 ideally
• In 50%of the population emmetropia is not
reached and some degree of hypermetropia
persists
• On the other hand, the mark maybe
overshot, and the eye may become myopic
By the age
of 5 – 7
years

4. Normal variation with age
After 50 years of age
• Tendency to develop hypermetropia again
• It due to 2 factors, both associated with lens
• Outer cortical fibres have lesser curvature, decreasing
the converging power
• Old age index of refraction of cortex increases and lens
becomes homogenous decreasing the converging
power (index hypermetropia)
• In early life unless the error is unusually large the
accommodative power can correct it all
• After 65 all of the hypermetropia becomes absolute due
to loss of accommodation

5. AMETROPIA
State of refraction wherein parallel rays of light
coming from infinity are focussed either in front or
behind the sensitive layer of retina in one or both
meridian
 Myopia
 Hypermetropia
 Astigmatism

6. Components of ametropia
Corneal power
Anterior chamber depth
Crystalline lens power
Axial length

7. HYPERMETROPIA
Refractive state of the where parallel rays of light
coming from infinity are focussed behind the
retina with accommodation being at rest

8. classification
Aetiological
types
Clinical types
Classification
by extent of
error

9. Aetiological types
Axial hypermetropia
Curvatural hypermetropia
Index hypermetropia
Positional hypermetropia
Absence of crystalline lens
Consecutive hypermetropia

10. Axial hypermetropia
 By far the commonest form
 Axial shortening of the eyeball
 About 1 mm shortening in the eyeball results in 3D of
hypermetropia
 Can also occur pathologically
 Orbital tumour or orbital mass may indent the
posterior pole and displace the macular region
forward
 Retinal detachment

11. Curvatural hypermetropia
 Curvature of the cornea or lens or both is flatter than
the normal
 Cornea plana
 Trauma
 About 1mm increase in the radius of curvature
results in 6D of hypermetropia

12. Index hypermetropia
Occurs due to change in the refractive index of the lens
Mostly due to old age
Can also occur in diabetics
In youth the refractive index of cortex is considerably less than that of the nucleus, and this inequality results in the formation of combination of
central lens surrounded by 2 converging menisci
In old age the refractive index of the cortex increases, lens becomes more homogenous and acts as single lens, consecutively power of the lens as
a whole decreases
However in nuclear sclerosis the refractive power of the nucleus increases which maintains or even increases the difference between nucleus and
the cortex

13. Positional hypermetropia
 Results from posteriorly placed crystalline lens
 Can be congenital or due to trauma

14. Absence of crystalline lens
 Congenital or acquired
 Aphakia, condition of high hypermetropia

15. Consecutive hypermetropia
 Overcorrected myopia after refractive surgery,
implantable contact lens
 Underpowered IOL in cataract surgery

16. Clinical types
Simple hypermetropia
Pathological
hypermetropia
Functional hypermetropia

17. Simple hypermetropia
 Commonest form
 Results from normal biological variations in the
development of the eyeball
 Can be hereditary
 It includes
 Axial hypermetropia
 Curvatural hypermetropia

18. Pathological hypermetropia
 Results due to congenital or acquired conditions to
the eyeball which are outside the normal biological
variations of development
 Types
 Congenital
 Acquired

19. Congenital pathological
hypermetropia
 Microphthalmos
 Microcornea
 Congenital posterior subluxation of lens
 Congenital aphakia

20. Acquired pathological
hypermetropia
 Senile hypermetropia
 Curvatural
 Index hypermetropia
 Positional hypermetropia
 Aphakia
 Consecutive hypermetropia
 Retrobulbar orbital tumours, by pushing the
posterior wall of the eyeball anteriorly

21. Functional hypermetropia
 Results from paralysis of accommodation as seen in
patients with 3rd
nerve palsy and internal
ophthalmoplegia

22. Classification on extent of
error
 Low – refractive error of +2D or less
 Moderate – refractive error of +2.25 to +5.0D
 High – refractive error of +5.25D or more

23. Components of
hypermetropia
 Total hypermetropia
 Total amount of refractive error which is estimated
after complete cycloplegia with atropine
 It consists of latent and manifest hypermetropia

24. Latent hypermetropia
 Implies the amount of hypermetropia ( 1D) which is
≈
normally corrected by the inherent tone of the ciliary
muscle
 Degree of latent hypermetropia is high in children
and gradually decreases with age
 Latent hypermetropia is exposed when refraction is
carried out after abolishing the tone with atropine

25. Manifest hypermetropia
 Remaining portion of the hypermetropia which is
not corrected by ciliary tone
 Consists of 2 components
 Facultative hypermetropia
▪ Constitutes that part which can be corrected by patient’s
accommodative effort
 Absolute hypermetropia
▪ Residual part of the manifest hypermetropia which cannot be
corrected by patient’s accommodative efforts
TOTAL HYPERMETROPIA = LATENT + MANIFEST (FACULTATIVE + ABSOLUTE)

26. Clinical picture
Asymptomatic (<1D) in young patients is corrected by
mild accommodative effort
Aesthenopic symptoms (1-2D), patients develops
aesthenopic symptoms due to sustained
accommodative efforts
• Tiredness of the eyes
• Frontal and frontotemporal headache
• Watering
• Mild photophobia
• Symptoms are aggravated as the day progresses and also by
prolonged near vision use

27. Clinical picture
Defective vision with aesthenopic symptoms
• 2-4D
• It is not corrected fully by accommodative efforts
• Patients complains of defective vision, more for near than
distance
• Associated aesthenopic symptoms due to sustained
accommodative efforts
Defective vision only
• >4D
• Patient usually do not accommodate, aesthenopic symptoms are
minimal
• Marked defective vision for near and distance

28. signs
Reduced visual acuity
Size of the eyeball may be normal or may appear small as a whole. A
scan may reveal short Anteroposterior length of the eyeball
Cornea may be slightly smaller than normal, maybe cornea plana
Anterior chamber is comparatively shallow since the eyeball is small
and the size of lens varies very little, and angle is narrow
(predisposition to narrow angle glaucoma)

29. Fundus examination
Optic disc may appear small and hyperaemic with ill-defined
margins and may mimic papillitis
The vascular reflex maybe accentuated and the vessels may
show undue totuisity and abnormal branchings
Foveal reflex may be situated at greater distance from disc
margin. It may cause large positive angle kappa (producing
apparent divergent squint)
The retina as a whole may shine due to greater brilliance of light
reflection (shot silk appearance)

30. complications
 Recurrent styes, blepharitis or chalazion due to
constant rubbing of the eye, done to get relief
from fatigue and tiredness
 Accommodative convergent squint may
develop in children (aged 2-3 years) due to
excessive use of accommodation
 Amblyopia may develop in some cases
 Predisposition to develop primary angle closure
glaucoma due to small size of the eye and
shallow ac

31. TREATMENT
 Optical treatment
 Surgical treatment
 Visual hygiene

32. Optical treatment
 Basic principle is to prescribe convex lenses, so that
the light rays are brought to focus on the retina

33. Modes of prescription of
convex glasses
 Spectacles
 Comfortable, safe and easy method
 Contact lenses
 Indicated in unilateral hypermetropia
 Should be prescribed once the prescription has been
stabilized
 Advantages over spectacles
▪ Cosmetically better
▪ Increased field of vision
▪ Less magnification
▪ Elimination of aberration and prismatic effect

34. Surgical treatment
Conductive keratoplasty/corneal refractive therapy
• Rarely done
Laser thermal keratoplasty
• Procedure done using laser energy to heat the cornea (contraction of collagen) and
increase its curvature
Photorefractive Keratectomy and their variants
• Direct laser ablation of corneal stroma after removal of corneal epithelium mechanically
• Done using EXCIMER LASER
Hyperopic LASIK
• Anterior flap of cornea lifted with keratome and excimer laser is used to sculpt the
stromal bed to change the refractive error of eye
• It can correct up to 4D of hypermetropia
Phakic IOLs
Refractive lens exchange

35. VISUAL hygiene
While reading or doing intensive near work,
take a break about every 30 mins
Maintain proper reading distance
Sufficient illumination
Limit to be set on time spent watching TV,
videogames
Sit 5 – 6 feet away from TV

36. aphakia
 Absence of crystalline lens from the eye
 From optical point of view, it may be considered a
condition in which the lens is absent from the
pupillary area and does not take part in refraction
 Aphakia produces high degree of hypermetropia

37. causes
 Congenital
 Surgical aphakia
 Aphakia due to absorption of lens matter, it is noticed
rarely after trauma in children
 Traumatic excursion of the lens from the eye
 Posterior dislocation of the lens in vitreous
 Heritable disorders with dislocation of lens
 Disorders leading to subluxation of lens

38. Image formation in aphakia
 Due to decreased converging power of the
eye parallel rays of light after refraction
converge beyond the retina

39. Image magnification
Average image magnification reported by different methods of
aphakia correction
 Spectacle : 33%
 Contact lens : 10%
 Anterior chamber IOL : 2-5%
 Posterior chamber IOL : 0%

40. Clinical features
Limbal scar may be seen in surgical aphakia
Anterior chamber is deeper than normal
Iridodonesis
Pupil is jet black in colour
Purkinje’s image test shows only 2 images
Absence of lens in patellar fossa is best elucidated on slit lamp examination
Fundus examination shows hypermetropic small disc
Retinoscopy reveals high hypermetropia

41. treatment
 Optical principle – to correct the error by convex lens
of appropriate power so that the image is formed on
retina
 Modalities
 Spectacles
 Contact lens
 IOL
 Refractive corneal surgery

42. spectacles
 Most commonly employed in the past
 Roughly +10D sph with cylindrical lenses for
surgically induced astigmatism are required to
correct aphakia in previously emmetropic patients,
however exact power will differ in individual cases
 An addition of +3 to +4D is required for near vision
to compensate for loss of accommodation

43. Disadvantages of spectacles
Image magnification
Spherical aberration
Prismatic aberration
Restricted field of vision
Coloured hue in vision
Cosmetic blemish
Cumbersome to use
Problem of near vision

44. Intraocular lens
implantation
Best available method
Commonly employed nowadays
In unilateral cases, primary implantation is indicated as
soon as the patient is fit for anesthesia, ideally between 2
and 3 months of age

45. Refractive corneal surgery
Keratophakia
• A lenticule is prepared from the donor cornea and placed between two lamellae
of patient’s cornea
Epikeratophakia
• Lenticule prepared from donor cornea is stitched over the surface of patient's
cornea after removing the epithelium
Hyperopic LASIK
• Corrective eye surgery in which a flap of the corneal surface is raised, and a thin
layer of underlying tissue is removed using a laser