Transcript Target IOP

Target Intraocular pressure
What is new?
Prof Dr Sayed S. E. H. Saif, MD ;
Professor of Ophthalmology, Cairo University
•
• B) The initial IOP is related to the cup disc changes as
well as the field in four grades using a simple formula
[(max. IOP - % reduction) – Z] and Z depends on the
disc or field damage
• C)Traverso C E, proposed to add a further 3% IOP
lowering for each risk factor or for each decade of life
expectancy; no more than four factors are to be
added, however.
• D) other methods described take in consideration the
risk factors in detail
• It is useful, however, to think in terms of an algorithm
to rationalize the need for individualized IOP goals in
each eye of each patient. A better definition of true risk
factors for progression and of life expectancy are
mandatory for the application of this algorithm.(
Traverso C E)
What is new?
• We are providing in this study a proposal for
estimation of the target IOP individualized for each
eye, determined accurately in advance as demanded
by Traverso . how ?
• The risk factors for getting glaucoma include
age, race, sex, heredity, family history ,
systemic (Diabetes, Obesity, Hypertension,
Hypotension, arteriosclerosis and smoking)
and socioeconomic factors as well as local
factors (myopia, corneal thickness and scleral
rigidity) all will channel into the resultant level of
IOP and disc damage . So calculation of the
combined probability of getting glaucoma for
these 2 factors alone will include all the above
mentioned variables. Table
Web Page: www.sayedsaif.com
Lecturer of Ophthalmology, Beni Sweif University
Figure 1 demonstrates the probability of getting glaucoma (Y1)in
relation to the IOP(X) and its derived equation
Y1=Y0+A1eX/T1
Dr Ahmed T.S. Saif, MD
Lecturer of Ophthalmology, Fayoum University
Subjects and methods
The cases introduced will scan most of our clinical need to estimate
the target IOP
1.0
Data: Data1_B
Model: ExpGrow1
Chi^2 = 0.00375
y0
0
±0
x0
15.81756
±11625096.92989
A1
0.027 ±71633.40731
t1
4.38096
±0.31175
probablity of primary
open angle glaucoma
0.8
0.6
0.4
0.2
0.0
18
20
22
24
26
28
30
32
34
Intraocular pressure (mmHg)
Y1= the probability of the incidence of POAG in the next 5 years when
the IOP = x1 ( modified from Davanger M, Ringvold A, Bilka S. The
probability of having glaucoma at different IOP levels. Acta
Ophthalmol. 1991;69:565-8)9
Figure 2 : demonstrates the probabilty of getting glaucoma (Y2) in
relation to the C/D ratio (X)
12/13/2004 23:21:51
Y2=Y0+A1eX/T1
1.0
B
B1
0.8
Incidenc of glaucoma %
• The target IOP is the mean IOP obtained with
treatment that prevents further glaucomatous damage
in the eye of the individual under consideration.
• The main problems of target IOP assessment are:
• • it must be individualized to the patient and to each
eye;
• • it should be an accurate estimate
• • it needs to be determined in advance.
• Estimation of the target IOP
• A) For any individual who has unquestionable damage
as a result of glaucoma, but in the early stage (see
Hodapp's grading system),“ a_20% decrease in IOP is
advisable. For moderate and advance damage, a 30
and 40% decrease of IOP from baseline, respectively,
is proposed. In addition to glaucoma damage stage,
one can also consider recognized risk factors for
further progression.
Dr M. Yasser S Saif, MD ;
Data: Data1_B
Model: Boltzman
Chi^2 = 0.00033
A1
0.02039
A2
4.01044
x0
1.38331
dx
0.34255
0.6
±0.04556
±4.12614
±0.54959
±0.08887
0.4
Target IOP
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
c/d(mm)
Y2= the probability of the incidence of POAG in the next 5 years when
the C/D ratio = x2 8 (formulated from the results of Wensor MD,
McCarty CA, Stanislavsky YL, Livingston PM, Taylor HR. The
prevalence of glaucoma in the Melbourne Visual Impairment Project.
Ophthalmology. 1998 Apr;105(4):733-9.)6
The combined probability will take in consideration the IOP (Y1) and
the C/D (Y2) ratio as the resultant outcome as shown in table1. 8
Y1+Y2
2
Early diagnosis
Accordingly people are classified after calculation of the probability of
getting glaucoma into the following:
Normal up to 0.10 on the probability scale with normal IOP up to 21
mmHg and C/D ratio up to 0.5: (Nothing to be done)
Ocular hypertension in whom the rise of IOP above 21 mmHg is the
only sign with normal C/D ratio and their management will follow the
general scheme of possible , probable, or definite as will be
demonstrated.
Possible up to 0.20 on the probability scale with rise of IOP more than
21 mmHg and increase of C/D ratio but the combined probability will
not exceed 0.20 .(Observation)
Probable up to 0.30 on the probability scale (these has to be treated
and observed) a monotherapy may be sufficient to achieve the target
IOP
Highly probable up to 0.40 on the probability scale (treatment
vigorously and observe) a bi-therapy may be needed to achieve the
target IOP
Definite more than 0.40 on the probability scale (full tolerable
treatment, laser or surgery and observe to achieve the target IOP)
Email: [email protected] , [email protected]
• In cases in whom treatment is necessary we have to achieve the
target IOP
• Our target IOP is to reduce the pressure to a probability of 0.10 or
maximally 0.20 if it is possible taking in consideration that the IOP
has to be corrected for any change in the corneal thickness or
scleral rigidity . The target pressure in our study is related to the
C/D ratio (corrected). (table 2)
• Management
• Normal:
nothing to be done
• Possible :
observe
• Probable:
treat and observe
• Highly probable: treatment vigorously & observe
• Definite: full tolerable treatment, laser or surgery & observe
• References:
1. . Carlo E Traverso . Identifying the target intraocular pressure and adjusting treatment In Robert N Weinreb,
Yoshiaki Kitazawa, Günther K Krieglstein, ; Glaucoma in the 21st Century ; Mosby International Ltd 2000 published
by Harcourt Health communication
2.Collaborative Normal-Tension Glaucoma Study Group. Comparison of glaucoma progression between untreated
patients with normal tension glaucoma and patients with therapeutically reduced intraocular pressures. Am J
Ophthalmol 1998;126:487-497.
3. Collaborative Normal-Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the
treatment of normal-tension glaucoma. Am j Ophthalmol 1998;126:498-505.
4. Traverso CE, Semino E, Morescalchi S, et al. Is the visual field of patients with advanced POAG protected by
lowering the IOP? In: Mills RP, Wall M, eds. Perimetry update 1994/1995. Amsterdam: Kugler; 1995:309-312.
5. Devindra Sood, NN Sood ‘ primary open angle glaucoma, Modern Ophthalmology 3rd Edition , Editor LC Dutta ,
publisher Jaypee. Vol 1 Ch 66 page 494
6. Saif SSEH, Saif MYS, Saif ATS. Early Detection of Glaucoma , A New Scoring System; Bull. Ophthalmol. Soc.
Egypt,2005;vol 98,number 3, 351-358
7. Davanger M, Ringvold A, Bilka S. The probability of having glaucoma at different IOP levels. Acta Ophthalmol.
1991;69:565-8
8. Wensor MD, McCarty CA, Stanislavsky YL, Livingston PM, Taylor HR. The prevalence of glaucoma in the
Melbourne
Visual
Impairment
Project.
Ophthalmology.
1998
Apr;105(4):733-9.
Mao LK, Steward LC, Shields MB. Correlation between intraocular pressure control and progressive glaucomatous
damage in primary open-angle glaucoma. Am J Ophthalmol 1991;111:51-55.
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