CCT and Target Pressure

1. EVIDENCE-BASED DECISION MAKING
IN GLAUCOMA MANAGEMENT
ROLE OF TARGET PRESSURE AND
CENTRAL CORNEAL THICKNESS
By
Dr Nkiru Kizor-Akaraiwe
@ South-East Glaucoma symposium
Feb, 2017

2. Background
• IOP is a very important risk factor
• IOP is the only modifiable risk factor
• Aim of glaucoma Rx is to maintain visual
function(by reducing the IOP to such a level that
glaucomatous damage will not continue) while
maintaining quality of life at a sustainable cost.
Treatment Principles & Options. EGS Guidelines, Edition 4. Pg 131-138

3. Evidence – Based Care for IOP
reduction in glaucoma Mx……
The Collaborative Normal-Tension Glaucoma
Study
Collaborative Normal-Tension Glaucoma Study Group(CNGTS).
Effectiveness of intraocular pressure reduction in the treatment of normal-
tension glaucoma. Am J Ophthalmol 1998;126:498-505

4. Evidence – Based Care for IOP
reduction in glaucoma Mx……
The Advanced Glaucoma Intervention Study
Collaborative Normal-Tension Glaucoma Study Group(CNGTS). Effectiveness of
intraocular pressure reduction in the treatment of normal-tension glaucoma. Am J
Ophthalmol 1998;126:498-505

5. Evidence – Based Care for IOP
reduction in glaucoma Mx……
The Collaborative Initial Glaucoma Treatment
Study
Musch DC, Gillespie BW, Niziol LM, et al; the CIGTS Study Group. Intraocular pressure
control and long-term visual field loss in the Collaborative Initial Glaucoma
Treatment Study. Ophthalmology. 2011;118:1766-1773.

6. Evidence – Based Care for IOP
reduction in glaucoma Mx……
The Ocular Hypertension Treatment Study
Kass MA, Heuer DK, Higginbotham EJ, et al. The Ocular Hypertension
Treatment Study: a randomized trial determines that topical ocular
hypotensive medication delays or prevents the onset of primary open-
angle glaucoma. Arch Ophthalmol. 2002;120(6):701-713.

7. Evidence – Based Care for IOP
reduction in glaucoma Mx……
Early Manifest Glaucoma Trial
Heijl A, Leske MC, Bengtsson B, et al; Early Manifest Glaucoma Trial Group.
Reduction of intraocular pressure and glaucoma progression: results from the
Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120(10):1268-1279.

8. What is Target pressure?
• Target pressure is defined as the upper limit of
IOP level at which further glaucomatous optic
neuropathy is unlikely to occur inorder to
maintain patient’s vision related quality of life.
• Target pressure is the IOP goal
• 1st introduced in 1989 by Paul F. Palmberg
Treatment Principles & Options. EGS Guidelines, Edition 4. Pg 131-138

9. Benefits of Target pressure in Mx
1. Gives the Physician a focus(goal) in care (No
‘continue Rx’)
2. Gives patient a focus and wish to keep their
follow-up appointments
3. Gives the patients a goal that makes them take
responsibility for their care & progress
4. Helps patients to appreciate success and non-
success and more agreeable to a change of
therapy (including surgery)
Inder Paul Singh. Setting Target Pressures. Glaucoma Today. September/October 2015

10. Setting Target IOP – Factors to consider
Factors to Consider Low Target IOP Higher Target IOP
1. Glaucoma
Damage
Advanced Early
2. Life
expectancy
Long Short
3. Baseline
(Untreated) IOP
Low High
4. Additional Risk
factors
Yes No
5. Rate of
Progression
Fast Slow
6. CCT Thin Thick
Treatment Principles & Options. EGS Guidelines, Edition 4. Pg 131-138

11. Risk factors for progression that may modify the initial target
IOP range include the following:
• Presence and severity of damage to fellow eye
• Rapid rate of progression of damage to fellow eye
• Family history of or genetic mutation predisposing to early
onset disease or severe disease, or both
• African ancestry
• Vascular risk factors: disc hemorrhage, nocturnal
hypotension, migraine, Raynaud's disease, diabetes
mellitus, previous vein occlusion
• Large fluctuation or instability in IOP (e.g., IOP spikes,
pseudoexfoliation syndrome)
• Poor follow-up
• Axial myopia (speculative)
Damji KF, Behki R, Wang L, for the Target IOP Workshop participants. Canadian
perspectives in glaucoma management: setting target intraocular pressure range. Can J
Ophthalmol 2003;38:189-197.

12. Setting Target IOP
– Numbers or Percentages?
Stage of
Glaucoma
Evidence IOP percentage
reduction
Range of IOP Findings from study
OHTN OHTS ≥20% 18-21mmHg 5% progression at
20% reduction
Mild Glaucoma EMGT
CIGTS
≥25% < 18mmHg 30% reduction no
progression in 7yrs
Moderate
Glaucoma
CIGTS
AGIS
≥30% 14-16mmHg
Severe
Glaucoma
AGIS ≥35% 10- 12mmHg IOP average =12;no
progression x 14yrs

13. Principle for Setting Target pressure:
IOP
TgP = ------------------------------------------------
Level of function loss + RoP + Factors
Treatment Principles & Options. EGS Guidelines, Edition 4. Pg 131-138

14. Target pressure ….Points to note
• Always note down in the folder the set target
pressure with date.
• Target pressure is set separately for each eye
• Refer to it each visit – result of visit’s evaluation.
• Not static - change constantly depending on
whether the glaucoma is stable or shows signs of
progression.

15. Central Corneal Thickness
In
Glaucoma Management

16. Background
• IOP is a very important risk factor
• IOP is the only modifiable risk factor
• IOP is measured by either indenting or
applanating the central cornea therefore its
thickness will affect the reading.
Treatment Principles & Options. EGS Guidelines, Edition 4. Pg 131-138

17. Evidence – Based Care for CCT
measurement in glaucoma Mx……
The Ocular Hypertension Treatment Study
Kass MA, Heuer DK, Higginbotham EJ, et al. The Ocular Hypertension
Treatment Study: a randomized trial determines that topical ocular
hypotensive medication delays or prevents the onset of primary open-angle
glaucoma. Arch Ophthalmol. 2002;120(6):701-713.

18. CCT Values
• The normal distribution of CCT is 540µm ± 30
• Blacks generally have thinner corneas
• Screening population of normals @ The Eye
Specialists hospital, Enugu, Nigeria = 526µm ± 75
(Range of 458-608)
Rahman ML, Bunce C, Healey PR et al. Commingling analyses of central corneal
thickness and adjusted intraocular pressure in an older Australian population.
Invest Ophthalmol Vis Sci 2010;51(5) 2512-8

19. CCT differences among patient groups
• The mean central corneal thickness was:
» Controls = 554 µm
» POAG = 550 µm
» NTG = 514 µm - lowest
» OHT = 580 µm
Shah S, Chatterjee A, Mathai M, et al. Relationship between corneal thickness
and measured intraocular pressure in a general ophthalmology clinic.
Ophthalmology. 1999;106:2154-2160.
Copt RP, Thomas R, Mermoud A. Corneal thickness in ocular hypertension,
primary open-angle glaucoma, and normal tension glaucoma. Arch
Ophthalmol. 1999;117:14-16.

20. Differences among Diff races
Findings:
• Caucasians, Chinese, Filipinos & Hispanics = 0.550mm
> Japanese = 0.531mm
> African Americans = 0.521mm
Central corneal thickness of Caucasians, Chinese, Hispanics, Filipinos,
African Americans, and Japanese in a glaucoma clinic.
Aghaian E1, Choe JE, Lin S, Stamper RL. Ophthalmology 2004 Dec;111(12):2211-9

21. Why is CCT important?
• A Risk factor
• Misdiagnosis
• Uncertain-target pressure setting

22. CCT as a Risk Factor
• For development:
The Ocular Hypertension Treatment Study
(OHTS) showed that CCT is an important risk
factor for a change from ocular hypertension
to primary open-angle glaucoma.
Kass MA, Heuer DK, Higginbotham EJ, et al. The Ocular Hypertension
Treatment Study: a randomized trial determines that topical ocular
hypotensive medication delays or prevents the onset of primary open-angle
glaucoma. Arch Ophthalmol. 2002;120(6):701-713.

23. CCT & POAG development
• Subjects with CCT ≤ 555 µm had 3x greater
risk of developing POAG than
Those with CCT ≥ 588 µm
Gordon MO, Beiser JA, Brandt JD, et al. The ocular hypertension
treatment study: Baseline factors that predict the onset of primary
open-angle glaucoma. Arch Ophthalmol. 2002;120:714-720.

24. CCT as a Risk Factor
• For progression:
Powerful predictor of risk of glaucoma progression
- Early Manifest Glaucoma Trial (EMGT) with an 11-
year follow-up, CCT was a significant predictive factor
for glaucoma progression
- In a multivariate model study in Advanced glaucoma
pts by Weizer et al that included IOP, CCT was the
most powerful component of the predictive model.
Weizer JS, Stinnett SS, Herndon LW. Central corneal thickness as a risk factor for
advanced glaucoma damage. Paper presented at: Annual Meeting of The Association
for Research in Vision and Ophthalmology; May 5, 2003; Fort Lauderdale, FL.
Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120(10):1268-1279.Heijl A,
Leske MC, Bengtsson B, et al; Early Manifest Glaucoma Trial Group. Reduction of
intraocular pressure and glaucoma progression

25. CCT & Progression
Findings:
• Eyes with CCT 520 m had significantly
earlier glaucoma progression though the mean
IOP was less in them.
• Chiseliţă D1, Danielescu C, Gagos-Zaharia O, Gherman C.
Central thickness of the cornea in ocular hypertension and open
angle glaucoma Oftalmologia.2007;51(3):98-103

26. 2. Mis-diagnosis of glaucoma
• Variations in measurement of CCT may lead to
mis-diagnosis of glaucoma.
• Thin CCT  Underestimation of IOP/Target IOP
- Glaucoma patients are missed/suspects
- POAG classified as NTG
• Thick CCT  Overestimation of IOP/ Target IOP
- Normal patients receiving Rx as OHT
- NTG managed as POAG

27. The role of central corneal thickness in
the diagnosis of glaucoma
Result:
39% of eyes with ocular hypertension were
found to have a corrected IOP of ≤ 21 mmHg.
Thomas R, Korah S, Muliyil J. India J Ophthalmol 2000
Jun;48(2):107-11

28. 3. Uncertain estimation of Target pressure
• Low CCT  wrongly set higher TgP
E.g CCT = 480µm (+4); TgP = 12mmHg instead
of <9mmHg
• High CCT  wrongly set Lower TgP
E.g CCT 590µm (-4); TgP = 12 instead of
<16mmHg

29. The importance of central corneal thickness
measurements and decision making in general
ophthalmology clinics: a masked observational study
Result:
• CCT and adjusted IOP information led to
different treatment option in 37%(55/152).
- 20.4%(31/152) cases would have been commenced
on additional IOP-lowering medication
- 2.0%(3/152) would have been counseled for
trabeculectomy surgery
- 3.3%(5/152) of the cohort would have been
observed rather than treated
Patwardhan et al; BMC Ophthalmology2008;8:1 DOI: 10.1186/1471-2415-8-1

30. Central corneal thickness and potential error in
Goldmann applanation tonometry of the
Black African patient suffering from primary open-
angle glaucoma: 340 eyes surveyed.
Findings:
• GAT- affected by an error rate estimated at 69.4%
- 57.6% undervaluation
- 11.8% overvaluation
• Pachymetry is therefore a necessity for the
Black African glaucoma patient requiring IOP
adjustment.
• Fanny et al..J Fr Ophthalmol 2008 Apr;31(4):405-8

31. Conclusion…
• Target Pressure is the IOP goal set at
beginning that drives the glaucoma care
&
• CCT measurement (Pachymetry) is an
essential part of glaucoma pt’s evaluation for
determining the real target pressure,
predicting risk of development & progression
of disease thereby ensuring individual pt’s
optimal management.

32. THANK YOU!!!