Undergraduate ophthalmology lectures

1. The two Principal Meridians (of highest & lowest power) are NOT at right angle
to each others, and change of power from one meridian to the other is NEITHER
gradual NOR regular
• Corneal scars
• KCN

2. • Accommodative asthenopia; continuous attempts of the ciliary muscle
to compensate the error
• Blurred vision; near & far
• Running letters
• Distorted objects

3. • Cornea: scars, stitches, …
• Lens: subluxation
• Retina: Staphyloma
• e.g. Oil droplet in KCN (Charleux)
• Oval optic disc (different refraction along the
two principal meridians)
• Tilted optic disc (Retinal astigmatism)

4. • Scissoring reflex in KCN
• Different dioptric power in the two principal
meridians
• Measure Objectively the
refractive error of the eye
• Measures the corneal
curvature & dioptric power

5. • Irregular corneal circles
• Pseudo-colour
mapping of
corneal
curvature,
power &
thickness

6. • The patient sees the line in one meridian sharper than that on the
perpendicular meridian

7. Cylindrical Lenses
With its axis perpendicular to the
ocular axis to be corrected

8. Sphero-Cylindrical Lenses
The spherical lens renders the
error as simple astigmatism
The cylindrical lens corrects the
residual astigmatic error

9. For low astigmatic errors
In KCN

10. • A corneal flap is fashioned by an
automated keratome
• Excimer laser is used to ablate the steep
corneal meridian
• The flap is re-positioned

11. • Partial thickness corneal incisions at the steeper corneal meridian
• Applied in low astigmatic errors

12. Indications:
A. KCN

13. A mark on the IOL
denotes the axis of
astigmatism to be
corrected

14. Using a toric IOL

15. • Physiological recession of near
point of accommodation
• Increased lens stiffness
• Weak ciliary muscle

16. • Usually starts around the age of 40 years (earlier in
hyperopes)
• Poor near vision e.g reading, sewing
• Good far vision
• Accommodative asthenopia

17. • Monfocal: Reading
glasses separate from
distant glasses
Convex Lens

18. • Bifocal glasses
• Progressive Addition Lenses (PALs)

19. • 1st Correct vision for FAR
• Measure the Near Point of Accommodation (PP)
• Calculate Amplitude of Accommodation; (1 / PP)
• Keep 1/3 accommodation as reserve to give the presbyope range for reading
• Correct only the remaining 2/3
• Measure the working distance (usually 33 cm)
• Calculate lens power needed to focus at the working distance (1/0.33 = 3D)
• Determine the power of the lens needed for correction of Presbyopia (Power at
working distance - Power at PP)
• Add this power to the power needed for far correction
RAF Rule

20. • A 45 year old presbyope with + 2D for far
• PP at 40 cm
• Amplitude of Accommodation = 1/0.40 = 2.5D
• 1/3 is kept as reserve i.e 1/3 2.5 = 0.75 D)
• Correct only the remaining 2/3 (2.5 - 0.75 = 1.75 D)
• Measure the working distance (usually 33 cm)
• Calculate lens power needed to focus at the working distance (1/0.33 = 3D)
• Determine the power of the lens needed for correction of Presbyopia (3 -
1.75 = 1.25 D))
• Add this power to the power needed for far correction (1.25 + 2 = 3.25 D)

22. Convex Lens
• Bifocal lenses

23. • Excimer laser is used to changes the shape of the cornea to create
different power zones for seeing at varying distances

24. • Partial thickness scleral pockets are made in each of the 4 eye quadrants
• PMMA (PolyMethyl MethaAcrylate) bands are injected into theses pockets
• The aim is to expand the scleral ring at the zone of ciliary body, thus
stretching the zonules

26. • Absence of the crystalline lens
• Rare
• Trauma
• Post operative

27. • Defective far vision; because of hypermetropia
• Defective near vision; due to loss of accommodation
• History of surgery or trauma

28. • Scar of cataract extraction surgery
• Scar of ruptured globe
• Only two Purkinje Sanson images
absence of the two Purkinje Sanson
images formed by anterior &
posterior surfaces of the lens

29. • Deep AC

30. • Tremulous
(Loss of
support by the
lens),
Iridodonesis

31. • Jet black
colour
(Normally
a greyish
hue
appears in
phakic
clear
lenses)

32. • High hypermetropia (+ 10
D or more)
• Astigmatism Against the
rule (Because of
contraction of the corneal
scar at 12 o’clock position,
causing flattening of the
vertical meridian)
• Anisometropia (In
unilateral aphakia)

33. Convex
Lenses
In Bilateral aphakia
Prescribe separate glasses for
distant & near correction or
use bifocals or PALs
Convex
Lenses
In Bilateral or Unilateral aphakia
Prescribe Bifocal Lenses, or Monofocal
lenses with reading glasses

34. It is the best option (Least image
magnification)
Might be used in Unilateral or Bilateral
aphakia
Implant monofocal IOLs with additional
reading glasses, or implant multifocal
IOL

35. • Reading ADD in aphakic eyes is + 3D
(Accommodation is lost)
• Disadvantages of Glasses in correction of
Aphakia:
1. Image magnification (30%); Anisometropia in
unilateral cases
2. Peripheral abberation
3. Visual field constriction
4. Thick heavy lenses with poor cosmoses

36. • A difference of refractive power between the two eyes of 4 D or
more
• Common
• Aphakia

37. Anis-eiokonia
Different
image size in
both eyes
(>30%)

38. Binocular Diplopia
Anisometropic Amblyopia
Amblyopic Squint

39. • Causes less change in image size
(10%)
• LASIK
• IOL Implantation (1% change in image
size)

40. • Objective method for assessment of
refractive state of the eye by:
Illuminating the eye
Observation of the direction of
movement of red reflex

41. Retinoscope
Direct
Ophthalmoscop
e

42. • Put Cycloplegic E.D
• Back of the eye is
illuminated with a
streak light coming
out of the retinoscope
• The Examiner moves
the retinoscope from
side to side & up and
down, observing the
red reflex
• WITH movement
indicates Hyperopia
(Put plus lenses)
• AGAINST movements
indicates Myopia (Put
minus lenses)
• NO movement
indicates emmetropia
(Neutral Point)
• Subtract Working
distance at the end

43. + 0.5 DS,
+ 2.00
DC,
Axis 180
+ 1.5 DS,
- 5.00 DC,
Axis 90
- 3.5 DS,
+ 5.00
DC,
Axis 180

44. • Automated, Objective method for assessment of refractive state of
the eye
• Myopia: Prescribe the lowest minus lens that gives the best VA
• Hyperopia: Prescribe the highest plus lens that gives the best
VA
• Astigmatism: High cylinder lenses causes image distortion
• Reading Correction is added to the spherical component only

45. • Automated, Objective method for assessment of refractive power, Curvature &
thickness of the cornea

46. ASSESSME
NT OF
REFRACTIV
E ERRORSMOHAMED ABDELZAHER MD, FRCS

48. Diminution of
vision
Defective night
vision
Difficult near
vision
Headache Running
letters
Frowning to see
better
Ocular
Deviation

49. History
Age

50. History
Systemic
Diseases
Drugs
The prescription of spectacles
should be delayed until a stable
refraction is obtained, if possible.
Chronic hyperglycaemia myopia
Chronic hypoglycemia hyperopia
Acute changes in
plasma glucose level
hyperopia
Fukimi O et al Refractive changes in diabetic patients during intensive glycemic control. Br
J Ophthalmol 2000;84:1097–1102.

51. History Previous
Prescriptions
Ocular
Surgery

52. Exam
UAVA

53. Exam
UAVA

54. WHY IS THE PATIENT COMPLAINING?!! 😏
To Declare that the patient is seeing a line, he must read
at least ½ of the line correctly.

55. More evident in Amblyopia

56. Pin Hole
Vision improves
Vision worsensNo changeRefractive error
Corneal opacity
Cataract
Vitreous hemorrhage
Macular lesion

57. Thorough Ocular Exam

58. • Objective method for assessment of
refractive state of the eye by:
Illuminating the eye
Observation of the direction of
movement of red reflex

59. • Automated, Objective method for assessment of refractive state of
the eye
• Myopia: Prescribe the lowest minus lens that gives the best VA
• Hyperopia: Prescribe the highest plus lens that gives the best
VA
• Astigmatism: High cylinder lenses causes image distortion
• Reading Correction is added to the spherical component only
View through an autorefractor

60. Cycloplegic Refraction
Infant
Young Age
Uncooperative

61. Subjective
Refraction
Adjust the IPD
Phoropter

62. Spherical
Equivalent

63. Transposition
+ 0.50 DS, - 0.50 DC / 85
0.00 DS, + 0.50 DC / 175
Equals

64. Hyperopia
Pseudo-myopia
Anisometropic Amblyopia

65. If you are not willing to learn, No one can help you.
If you are willing to learn, No one can stop you.