Structural damage from glaucoma can be detected in the optic nerve head (ONH) before functional vision loss occurs. Examination of the ONH is important for early detection of glaucoma, monitoring progression, and determining the type of glaucoma. Key aspects to examine include disc size and shape, cup-to-disc ratio, neuroretinal rim width and contour, retinal nerve fiber layer visibility, and presence of hemorrhages. Localized or diffuse changes in these structural parameters over time compared to baseline indicate glaucomatous progression.

1. ARAVIND EYE CARE SYSTEM
Aravind Eye Hospital
& Postgraduate Institute of Ophthalmology
Tirunelveli, India
ONH EVALUATION IN GLAUCOMA
Dr. Devendra Maheshwari
Glaucoma Service

2. Glaucoma
Optic neuropathy
characterized by
progressive injury to
retinal ganglion cells
and their axons
Specific pattern of
optic atrophy
(“cupping”)
Associated visual
function deficit

3. Structural Damage Precedes
Functional Change
 NFL injury can be observed up to 6 years
before
VF defects1
◦ Mean number of axons2 in normal ON ~800,000–
1,200,000
◦ 25-40% of ON fibers can be lost from an eye that
retains
a normal visual field2,3
1. Sommer A et al. Arch Ophthalmol. 1991;109:77-83.
2. Quigley HA et al. Arch Ophthalmol. 1982;100:135-46.
3. Kerrigan-Baumrind LA et al. Invest Ophthalmol Vis Sci. 2000;41:741-748.

4. Structural Damage Precedes
Functional Change (contd.)
VF loss by SAP does NOT mean early
disease
◦ By the time VF loss is detected by SAP,
substantial
structural damage may exist1,2
◦ Functional loss may be detected earlier using
selective tests
(eg, FDT, SWAP)2
FDT=frequency doubing technology; SAP=standard automated perimetry; SWAP=short
wavelength automated perimetry.
1. Sommer A et al. Arch Ophthalmol. 1991;109:77-83.
2. Bowd C et al. Invest Ophthalmol Vis Sci. 2001;42:1993-2003.

5. ONH ASSESSMENT IS USEFUL TO
Detect glaucomatous ONH damage early
Follow up - progression
To differentiate various types of glaucoma
Hints about pathogenesis.

6. EXAMINATION TECHNIQUES
DIRECT OPHTHALMOSCOPY
INDIRECT OPHTHALMOSCOPY
SLIT LAMP TECHNIQUES
◦ GOLDMAN THREE MIRROR LENS
◦ HRUBY LENS
◦ PLUS 78 AND 90 D LENS
◦ PHOTOGRAPHIC TECHNIQUES

7. ONH IN GLAUCOMA
Normal ONH
Glaucomatous ONH
D.D of glaucomatous
disc

8. NORMAL OPTIC DISC
Size and shape
Neuro retinal rim
Optic cup
Vessels
Lamina cribrosa
Peripapillary region
NFL

9. Surfacee
AAnnatomatomyy
Disc
margin
NRR
CLV
NASAL
Cup margin
TEMPORAL
INF
SUP

10. OPTIC DISC - SIZE
Not constant
Inter – individual variability
Small to larger optic disc
Slight change in size with +5.0 D to – 5.0 D
High myopia & hyperopic marked change
(1. JonasJ.B etal – Surv.oph.1999.43
2. Romrattenr.S etal ophthal 1999.106)

11. OPTIC DISC - SIZE
Varies with race
Caucasian have smaller disc
Asian & afro – American have larger disc
( Chit,Ritch . R , Arch of oph. 1989 - 107 &
Varma . R etal Arch of oph. 1994 – 112)

12. NORMAL OPTIC DISC
DIAMETER
AREA
1.70 - 1.80mm(H)
1.85mm - 1.95mm(V)
LARGER IN BLACKS
1.67 S.M - 2.69mm Sq.mm.
12% LARGER IN BLACKS
MEN HAS LARGER DISC (3%)
NRR AREA 1.90 - 1.92 Sq.mm.
Vertically oval

13. OptiOpticc
DiDissccSSii
ze
Horizontal
disc diameter
Vertical
disc
diameter
Scleral
ring

14. size withf opopttiicc
ddiiscsc
moscooscope
pe
ddeeggrreeee))ooff
tt
Measurement o
direct ophthal
Small aperture (5
Welch-Allen direc
ophthalmoscope
Optic Disc Size
Size of light spot ~ size of average optic disc

15. Measurement of optic disc size with
biomicroscopy
Volk lens
Measure length of slit beam
Avg vertical diameter: 1.8 mm
Correction factors
Volk 60D – x 1.0
Volk 78D – x 1.1
Volk 90D – x 1.3
Avg horizontal diameter: 1.7 mm
Optic Disc Size

16. Size of cup varies with size of disc
Large discs have large cups in healthy eyes
1.4
Small Average
Identify small and large optic discs
Small discs: avg vertical diameter <1.5 mm
Large discs: avg vertical diameter >2.2 mm
1.9
Large
2.4
Optic Disc Size

17. Optic Disc Size
Be cautious with myopic discs

18. OPTIC DISC - SHAPE
Usually slightly vertically oval
Not correlated with age, sex etc
Abnormal O.D. shape – corneal
Astigmatism, Amblyopic
Keratometry & Retinoscopy

19. The optic disc cup is the difference between
the number of axons going through and the
available size of the hole (scleral canal)
OPTIC
CUP

20. OPTIC CUP
In smaller disc – obviously no cup
ONH change may be erroneously overlooked in small
disc
Small disc often show glaucoma Abnormalities in the
P.P region such as
- Decreased visibility of RNFL
- Diffuse or focal diminished diameter of retinal
arteriole
- PPCR Atrophy

21. Area 0.72 sq.Mm
◦ Shape - correlate with size
of the disc
◦ Horizontally oval
◦ Difference between the
number axons going
through and available area
of the hole.
PHYSIOLOGIC CUP

22. NEURO RETINAL RIM
Size:
 Intrapapillary equivalent of RNFL & O.N. fibers
Main target
Considerable inter- individual variability
Correlated with optic disc area
Larger disc larger RIM
(Jonas etal Survey Oph. 1999)

23. Rim width
Distance between
border of disc and
position of blood
vessel bending
S
N T
ISNT rule
Inferior >
Superior >
Nasal >
Temporal
I
ISNT RULE

24. NRR -SHAPE







Broader inferiorly  supuriornasal
Narrower temporally
ISNT- rule of Elliot Werner
Early glaucoma – predominantly
IT & ST regions involved
Moderately advanced glaucoma – temp.H.D
Very advanced – nasal disc sector
Sequence of disc sectors correlate with the progression of
visual field defects.
(IT,ST,TH,IN&SN)
(R.Hitchings,G.Spaeth BJO 1977,BJO 1980
Schwartz - Survey 1980)

25. RNFL visibility
Appear as fine, feathery, silvery striations
In RNFL defect the striations is reduced or
absent
Appear as a darker band
Better visualized with green light.
In healthy eyes blood vessels appear blurred,
because they are buried in deeper layers of NF.
In defective area marked and sharp.

26. 1. Inferior temporal
2. Superior temporal
3. Temporal
4. Nasal
NERVE FIBER LAYER VISIBILITY

27. ONH CHANGES IN GLAUCOMA
Structural changes
Contour changes
Colour changes

28. ONH CHANGES IN GLAUCOMA
Quantitative
Qualitative

29. ONH CHANGES IN GLAUCOMA
I. Quantitative




Optic disc size (vdd)
Cup / disc ratio (vertical)
Rim / disc ratio
Rnfl height

30. ONH CHANGES IN GLAUCOMA
II. Qualitative
Contour of NRR
O.D. Haemorrhage
Peripapillary atrophy
BCLV
RNFL defects
Pallor

31. Disc evaluation
A Intrapapillary characteristics
• Disc size and shape
• Cup size and symmetry
• NR Rim configuration & cup size
• Vascular changes (Vessel signs)

32. Disc evaluation
B Parapapillary characteristics
• RNFL
• Hemorrhages
Vessel diameter
• Parapapillary atrophy (alpha and beta)

33. THE HALLMARK OF GLAUCOMATOUS
DISC DAMAGE IS EXCAVATION

34. Step I
Optic disc size
Is it a small, medium, or large disc?

36. Step II
Is it a round, oval or abnormal
disc shape?

37. Disc shape
vertically oval
• variations (“tilted disc”)
• secondary elongation in high myopia
Disc shape influences rim shape

38. Step III
Cup size and Asymmetry
Is cup size/rim size appropriate for disc
size?

39. CUP TO DISC RATIOS
CD ratio in normal – larger horizontally
Depend on the size of the optic disc cup
Inter individual variability
CD ratio in normal range from 0.0 to almost
0.9

40. DISC CUP SIZE
Smaller canal = small cup
Fibers bunched together
Larger canal = large cup
High myopes

41. CDR VARIES WITH :
Size
Race
Age ?

42. CUP DISC RATIO







Ratio of the disc diameter to cup
diameter
Less than 10% of normal population - 0.5
or greater
C.D ratio genetically determined
Inter observer / intra observer variability
Lichter “an inexact method of recording
the status of the disc “
Blacks have + C.D ratio
Horizontal CD is more

43. CD Ratio
6% havin g greater than 0.5
CD(ArmRaalyteitoalDoc. Oph. 1969)
Difference in CD ratio > 0.1 in only 8%
>0.2 in less than 1% of normal population

44. Normal
C/D = 0.77
POAG
C/D = 0.4

45. ASYMMETRICAL CUP
0.2 disc diameter or more
In either axis in discs
Discs of equal size
Discs of different size

46. Asymmetric disc
and cup
RE LE

47. CUP AND NEURAL RIM ALTERATION
A) Increased cup size (focal or concentric)
B) Increased C.D ratio
C) Alterations in cup shape (V-H disproportion)
D) Asymmetry of cup.
ONH IN GLAUCOMA

48. CUP ENLARGEMENT
UNIPOLAR
BIPOLAR

49. Localized
Diffuse - generalized
Change in normal
topographic
configuration (selective
narrowing in inferior and
superior quadrants)
DIFFUSE LOSS OF NEURAL RIM

50. Step IV
NRR configuration
Where is the smallest rim
width?

51. 1
2
1
2

52. Notching
Localized Rim
Thinning/Notching

53. Notch

55. Diffuse pallor
Cup
Pallor > cup
Non-glaucomatous
neuropathy
Pallor

56. Step V
RNFL evaluation
Look with red-free illumination.
Are there localized RNFL defects? Is there
an overall decrease in RNFL visibility?

57. R.N.F.L DEFECTS
1. Slit like or groove like defects
2. Wedge shaped defects
3. Diffuse atrophy
4. Total atrophy

58. Split N.F

59. Early NFL Defect

60. WEDGE SHAPED

61. NFL Defect with Prom.. vessel

63. Diffuse loss

64. Small Disc

65. • Normal RNFL: more or less rules out
glaucoma (or any other ganglional damage)
• Local defects in RNFL proof damage
They do not proof glaucoma
(DD: retinal scars, disc drusen, …, …)
Beware: slit-like pseudodefects

66. Step VI
•Vascular signs.
• Disc Haemorrhage
•Bayoneting
• BCLV
• Over pass vessels
• Nasalization

67. Disc hemorrhages:
In glaucoma diagnosis:
Always look for hemorrhages
(You VERY LIKELY miss them!)
In presence of hemorrhage:
Always rule out glaucoma. Patient
suffers from glaucoma until proven
otherwise.

68. DD Disc hemorrhages:
CRVO, DRP, disc drusen, any condition with
disc swelling, idiopathic, …, ...
Hemorrhages in glaucoma
•are adjacent (NOT at) an existing notch
•indicate progression of glaucoma
•occur there, where some rim is left

69. Optic Disc Hemorrhage
Indicative of glaucoma progression
Flame-
shaped
hemorrhage

70. Optic Disc Hemorrhage
Normally disappears after 4-8 weeks

71. Optic Disc Hemorrhage
Detection of disc hemorrhages requires
careful optic disc examination

75. BCLV

76. Parapapillary Atrophy
Alpha zone
• Hypo- and hyper-
pigmented areas
• Present in normal as well
as in glaucomatous eyes

Beta zone
• Atrophy of the retinal
pigment epithelium (RPE)
and choriocapillaris
– Large choroidal vessels
become visible
• More common in
glaucomatous eyes


77. PARA PAPILLARY CHORIO -
RETINAL ATROPHY
Beta zone :-
• Complete loss of RPE & diminished photoreceptors
• Central zone
• Visible sclera & large Chordial vessels
• Corresponds to absolute Scotoma
• Myopic Vs glaucomatous beta zone
• Larger & occur more in glaucomatous eyes

78. Parapapillary Atrophy
Beta zone
Width of beta
zone inversely
correlates with
rim width at same
area
Larger beta zone
 thinner rim
Progression of
beta zone
associated with
progressive
glaucoma
Thin rim
Larger  zone

79. ONH Changes in Glaucoma
Changes over time :-
◦ Extension of cupping
◦ Increasing shift of retinal vessels.
◦ Increasing Asymmetry of cupping
◦ Disc pallor
◦ Disc hemorrhages

80. LARGE BETA ZONE
“Halo glaucomatous”
often associated with
• A marked degree of fundus tessellation
• Shallow Glaucoma cupping
• Relatively low frequency of disc Hge & detectable
NFLD
• Concentric loss of NRR
• Normal IOP
• Location of PPCA is spatially correlated with NRR loss
in intrapapillary region
• Larger in the sector with more marked loss of NRR

81. DIAMETER OF RETINAL
ARTEROLES
Diffuse narrowing
Focal attenuation
FFA shows true Stenosis

82. 1. Determine disc size (Elschnig)
2. Check for unusual disc shape
3. Determine cup/rim size in relation to disc size
4. Evaluate rim shape (smallest rim width?)
5. Check RNFL (red-free illumination)
6. Look for disc hemorrhages:
Rule out glaucoma
High myopia: Rule out glaucoma
Check List

83. Optic Disc/RNFL
Examination
“The 5Rs”

84. 1 Observe the scleral Ring
to identify the limits of the
optic disc and its size
2Identify the size of the Rim
3 Examine the Retinalnerve
fiber layer
4 Examine the Region of
parapapillary atrophy
5 Look for Retinal and optic
disc hemorrhages
Glaucoma or Normal?
Use the 5 Rules
This section was developed by Robert N. Weinreb, MD, Felipe Medeiros, MD,
and Remo Susanna Jr, MD.

85. D.D. OF GLAUCOMATOUS
CUPPING
O.D. Coloboma
Optic pit
Morning glory syndrome
AION
Sellar lesions
Methyl alcohol poisoning
Myopic disc
Tilted disc

86. EARLY DIAGNOSIS OF GLAUCOMA
“Careful assessment of the disc is
probably still the best way of diagnosing
early glaucoma”

87. Thank You