2. Introduction
Normal-tension glaucoma (NTG) is a form of open-
angle glaucoma characterized by glaucomatous optic
neuropathy and corresponding visual field defects in
patients with IOP measurements consistently lower
than 21 mmHg
3. Case Presentation
47 Year old, female
Teacher
Mumbai
Visited our institute with primarily for a squint
opinion
4. History
H/o of using glasses
She reported as being a hypotensive patient
Family h/o: Mother – High myopia, ? Glaucoma
5. Examination
BCVA:
1. (RE): -6.00/-0.75x30 add +1.50ds 6/6,N6
2. (LE): -5.00/-1.00x130 add +1.50ds 6/6,N6
(LE) Exotropia
On PBCT: 70 pd base in deviation for distance and
near with good fusion
6. RE LE
Lid N N
Conjunctiva Quiet Quiet
Cornea Clear Clear
AC Deep and quiet Deep and quiet
Iris CPN CPN
Pupil 7mm 7mm
Lens Clear Clear
Fundus CDR=0.85 :1
Inferior Notch
Dull FR
CDR=0.85 :1
Inferior Notch
Dull FR
8. Gonioscopy
BE- PTM seen in all quadrants
Hence, wide open angles were observed.
9.
10.
11.
12. DVT
BP- 94/60 mmhg to 110/70 mmhg
IOP – (RE) 12-18 mmhg
(LE) 10-16 mmhg
For both eyes - Min : 2 am & Max : 2 pm
13. Management
Diagnosed as NTG
Started on e/d Travaprost hs
She underwent B/L Lateral Rectus recession and MR
resection on 24/06/2014
14. Epidemiology
NTG is a disease of the elderly.
Beaver Dam Eye Study:
The prevalence of likely NTG increased from 0.2% in the 43–54
years age group to 1.6% in those over 75 years of age
Below 50 years - 11% to 30% of all glaucoma cases
More prevalent in the female population
Positive family history - 5% to 40% *
Higher prevalence in Japanese population
*1.Miglior M. Low critical tension glaucoma: present problems. Glaucoma 1987;9:77.
*2.Geijssen HC. Studies on normal pressure glaucoma. Amsterdam: Kugler, 1991;1:1.
16. Pressure dependent factors
IOP in NTG : A “risk factor” for the development and
progression of the disease
Impaired optic nerve blood flow or a structurally abnormal
lamina cribrosa, which cannot withstand a normal range
of IOP.
The effectiveness of intraocular pressure reduction in the
treatment of normal-tension glaucoma was studied by:
Collaborative Normal-Tension Glaucoma Study Group
17. Collaborative Normal-Tension Glaucoma Study
Group
PURPOSE: To determine if intraocular pressure plays a
part in the pathogenic process of normal-tension
glaucoma.
METHODS:
1. One eye of each eligible subject was randomized either to be
untreated as a control or to have intraocular pressure lowered by
30% from baseline.
2. Eyes were randomized if they met criteria for diagnosis of
normal-tension glaucoma and showed documented progression
or high-risk field defects that threatened fixation or the
appearance of a new disk hemorrhage.
18. RESULTS:
Sample size: 140 eyes of 140 patients
Groups : Treatment group : 61
Untreated control: 79
Patients reaching end points (specifically defined criteria
of glaucomatous optic disk progression or visual field loss)
1. 28 (35%) of the control eyes
2. 7 (12%) of the treated eyes
Of 34 cataracts developed during the study, 11 (14%)
occurred in the control group and 23 (38%) in the treated
group (P = .0075), with the highest incidence in those
whose treatment included filtration surgery.
19. CONCLUSIONS
Intraocular pressure is part of the pathogenic process in
normal-tension glaucoma.
Therapy that is effective in lowering intraocular pressure
and free of adverse effects would be expected to be
beneficial in patients who are at a risk of progression
21. Systemic Hypotension
Various study show the role of systemic hypotension in
the pathogenesis of the optic neuropathy in NTG :
1. Greater nocturnal decrease and a lower level of diastolic
BP
2. In both NTG and HTG groups, lower BP at night
resulted in pts having progressive disease
3. Overall glaucoma pts, those on antihypertensives who
had a larger nocturnal decrease in systolic pressure
tended to have deteriorating visual fields
22. Abnormal Blood flow
Optic nerve blood vessel diameter may be affected by
vasospasm and the association between vasospastic
disorders
Drance et al found decreased finger capillary flow in NTG
patients suggesting vasospasm as an underlying
aetiological factor
Close associations: Migrainous headache and Raynaud’s
phenomenon
23. Mean Ocular Perfusion Pressure
Ocular perfusion pressure (OPP), the relationship
between systemic blood pressure and IOP
Mean ocular perfusion pressure(MOPP)
MOPP = 2/3 [DBP + 1/3(SBP – DBP)] – IOP
Risk factor for open-angle glaucoma.
Because low blood pressure lets OPP drop, and low OPP is
similar to elevated IOP,hence it has consistently and
strongly been associated with OAG.
24. Misc factors
Other factors include:
Abnormal blood coaguability
Endothelin (ET1), a potent and continuous vasoacting
peptide is associated with NTG.
Obstructive sleep apnea/hypopnea syndrome
(OSAHS)- Prevalence overall : 5.7% & In severe: 7.1%
25. Systemic Associations
Patients with normal-tension glaucoma have been noted to have
A higher prevalence of hemodynamic crises
Hypercoagulability;
Hypertension/Hypotension
Increased blood viscosity
Elevated blood cholesterol and lipids
Carotid artery disease
Slowed parapapillary, choroidal, and retinal circulations
Peripheral vasospasm
Migraine.
26. Main Criteria
A mean IOP off treatment <=21 mm Hg on diurnal testing,
with no single measurement greater than 24 mm Hg
Open drainage angles on gonioscopy
Absence of any secondary cause for a glaucomatous optic
neuropathy
Typical optic disc damage with glaucomatous cupping and
loss of neuroretinal rim
Visual field defect compatible with the glaucomatous
cupping (disc/field correlation)
Progression of glaucomatous damage.
27. Work Up for NTG
History
Physical Examination
Diagnostic Procedures
DDx
Manangement
28. History
Neurologic symptoms :
Headache, weakness, dizziness,
diplopia, or loss of
consciousness
Ocular trauma or
inflammation:
Possible prior intraocular
pressure elevation or other
causes of optic neuropathy.
Medications:
Systemic, topical, inhaled, or
nasal steroids, that can elevate
intraocular pressure
Compromised ocular
perfusion:
Sleep apnea, syncope,
Raynaud’s phenomenon,
anemia, hypotension, blood
transfusions.
Systemic hypertension
or hypotension
and any current
treatments for these.
29. Examination
Visual acuity
Color vision testing (to help differentiate from non-glaucomatous
optic neuropathies)
IOP measurement also Diurnal and if possible supine
Pachymetry
Afferent pupillary response testing
Gonioscopy
Complete slit lamp examination of the anterior segment
Dilated fundus examination with optic nerve head and retinal nerve
fiber layer (RNFL) assessment
30. Signs
The following features may be more frequently seen in
NTG compared to POAG:
- Flame shaped hemorrhages of the optic nerve rim
(Drance hemorrhage)
- Deep, focal notching of the rim
- Peripapillary atrophy
31. Optic nerve in NTG
Optic nerves with a larger surface area and with thinner
inferior/inferotemporal rims
PPA in a crescent or halo configuration
PPA: adjacent to areas of greatest disc thinning and
corresponding visual field loss
While thinning of the optic nerve rim is observed in all
POAG, focal thinning or ‘notching’ is more commonly
observed in NTG.
32. Acquired pits of optic nerve
Acquired pits of optic nerve [APON] which are
thought to be due to focal loss of neuroretinal rim
tissue and shown as localised excavations of the
lamina cribrosa, are more frequent in NTG.
More prevalent in lower pressure glaucoma than in
higher pressure glaucoma.
Inferior part of disc> Superior
Acquired pits of the optic nerve in glaucoma: prevalence and associated visual field loss.
Nduaguba C1, Ugurlu S, Caprioli J.
33. Disc Hemorrhages
Flame or splinter shaped, often with feathered ends, and is radially
oriented and perpendicular to the disc margin
Extends from within the optic nerve head to the adjacent retina,
crossing any peripapillary zone of absent or disrupted retinal pigment
epithelium
13.8 to 28.0% in NTG
Soares AS, Artes PH, Andreou P, Leblanc RP, Chauhan BC, Nicolela MT. Factors associated with optic disc hemorrhages in
glaucoma. Ophthalmology. 2004;111:1653-7.
. Diehl DL, Quigley HA, Miller NR, Sommer A, Burney EN. Prevalence and significance of optic disc hemorrhage
in a longitudinal study of glaucoma. Arch Ophthalmol. 1990;108:545-50
34. Disc Hemorrhages
Nerve fiber layer hemorrhage and arteriolar narrowing
were found more frequently
Optic disk hemorrhages showed significantly higher
percentages of progressed points within the 10-degree
area compared with the group without optic disk
hemorrhage
Comparative optic disc analysis in normal pressure glaucoma, primary open-angle glaucoma, and
ocular hypertension.
Tezel G1, Kass MA, Kolker AE, Wax MB.
Disk hemorrhage is a significantly negative prognostic factor in normal-tension glaucoma.
Ishida K1, Yamamoto T, Sugiyama K, Kitazawa Y
35. Symptoms
Asymptomatic until very advanced.
Subjective scotoma near fixation as these defects can
occur early on in the disease process of NTG
36. Diagnostic Tests
Visual Field testing
Pachymetry
Optic Disc imaging
OCT
24 Hr IOP evaluation
37. Visual field testing
Visual field defects may include those common to
POAG including nasal step and arcuate scotoma.
However, defects noted in NTG tend to be more focal
and occur closer to fixation early in the disease
Dense paracentral scotomas may characteristically be
noted at initial diagnosis
38. Role of Corneal Thickness in NTG
Patients with NTG have a thinner CCT than do patients
with POAG or controls.
Underestimation of the IOP in patients with POAG who
have thin corneas may lead to a misdiagnosis of NTG,
while overestimation of the IOP in normal subjects who
have thick corneas may lead to a misdiagnosis of OHT.
Corneal Thickness in Ocular Hypertension, Primary Open-angle Glaucoma, and Normal
Tension Glaucoma
René-Pierre Copt, MD; Ravi Thomas, MD; André Mermoud, MD
39. Optic Disc Imaging
Optic nerve head photography is important to
document the status of the optic nerve at baseline and
for future comparisons
40. OCT RNFL
Normally a double-hump pattern with a dual prominence at the
superior and inferior borders.
Pattern lost with superior and inferior RNFL flattening in
glaucomatous eyes
Inferior quadrant> Superior quadrant
The mean RNFL thickness/disc area ratio showed a significantly lesser
value for NTG despite the fact that absolute values for mean RNFL
thickness and disc area was larger for NTG
41. 24 Hr IOP evaluation
24 Hour IOP evaluation helps to determine the
pressure spikes
Normal eyes : between 3 and 6 mmHg and the
variation may increase in glaucomatous eyes
42. Progression
Signs:
Increased disc cupping
Optic nerve disc hemorrahges
Increased peripapillary atrophy
Visual field loss
Monitoring:
Optic nerve head photos
Visual field testing
OCT
43. Neurological Work up
Marked asymmetry or unilateral optic nerve involvement
Unexplained visual acuity loss
Color vision deficits in the absence of visual field deficits
Visual field defects not corresponding or out of
proportion to optic nerve damage
Vertically aligned visual field defects
Atypical neurologic symptoms for glaucoma
Optic nerve pallor in excess of cupping
Age less than 50 years
44. Differential Diagnosis
Glaucomatous etiology
Primary open angle glaucoma with diurnal fluctuation
between normal and elevated IOP
Diurnal Variation Test helps in detecting pressure spikes
throughout the day
45. Intermittent acute angle closure glaucoma – r/o via
Gonioscopy
Tonometric underestimation of actual IOP (e.g. thin
central corneas) - Pachymetry
Resolved corticosteroid-induced, uveitic, or traumatic
glaucoma
Uveitic glaucoma/glaucomatocyclitic crisis (Posner-
Schlossman)
50. Managment
The main focus for treating NTG is on lowering the
INTRAOCULAR PRESSURE
It can be achieved by:
1. Medical Therapy
2. Surgery
51. Medical Rx
Studies suggest a 25%-30% reduction in IOP
Topical Prostaglandin analogues are the preferred
drug
Adjuntive use of Carbonic anhydrase inhibitors and B-
blockers
Though use of B-blockers should be avoided at night
Studies show brimonidine showed less visual field
progression than twice daily use of timolol Low-
Pressure Glaucoma Treatment Study.
A randomized trial of brimonidine versus timolol in preserving visual function: results from the
Low-Pressure Glaucoma Treatment Study.
Krupin T1, Liebmann JM, Greenfield DS, Ritch R, Gardiner S; Low-Pressure Glaucoma Study Group.
52. Surgery
Filteration surgeries with peri/intra operative use of
anti- metabloites like MMC and 5-FU show enhanced
success of surgery
53. Non IOP related Rx
The role of different neuroprotective agents still
remains controversial
Agents under study include
1. Memantine (NMDA blocker)
2. Unoprostone( Prostanoid and synthetic docasanoid)
3. -Statins (HMG-CoA reductase inhibitor)
4. Ginkgo Biloba
5. Resveratrol
Calcium channel blockers use remains doubtful in
cases where vasospasm is a factor
Defect in superior hemifield almost paracentral defects close to fixation was consistent over 2 perimetries
enhanced sensitivity to what would otherwise be physiologic IOP, resulting in glaucomatous damage of the optic nerve
The perfusion pressure changes during the day, but the tissue blood flow should remain stable, to maintain metabolic activity
The relationship between systemic hypertension and hypotension, ocular vascular perfusion pressure, and local regulation of ocular blood flow by vascular tone mediators such as endothelin seem to play a role in maintenance of a constant perfusion of optic nerve tissues.
The implication is that whenever the IOP of an individual is high enough to start the disease, the cascade of pathophysiologic events is the same (such as ischemia, interruption of rapid orthograde and retrograde axonal transport, excessive free radicals, triggering of apoptosis, and collapse of support provided by the lamina cribrosa). the ischemia in glaucoma does not result from simple inadequacy of blood flow, but is due to inadequate regulation of blood flow hypothetically with episodes of transient ischemia and re-perfusion injury
for example, a previously raised IOP following trauma, a period of steroid administration, or an episode of uveitis
A thorough history is important in the evaluation of the glaucoma suspect patient to uncover evidence of the condition, but also to detect other neurologic conditions that may be masquerading as NTG
Retinal Nerve Fiber Layer Analysis by OCT
a. RNFL is measured in the peripapilary region with circular scans of 3.4 mm diameter centered around the optic nerve head b. Measurements of RNFL thickness are shown in a TSNIT orientation and are compared to age-matched controlled individuals. c. The Green area is the 5th -95th percentile by age, Yellow Area is 1st-5th percentile, and Red Area is below the 1st percentile.