Correlation Between Intraocular pressure(IOP)and Intracranial pressure(ICP) inDog
Intraocular*pressure*(IOP)*measuring*devices*–from*the...
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Intraocular pressure (IOP) measuring devices – from the past to the future Frances MeierGibbons, MD 1 ; Sylvain Roy, MD, PhD 2, 3 1 Glaucoma Prac>ce, Rapperswil, Switzerland, 2 Montchoisi Clinic, Lausanne, Switzerland, 3 Swiss Federal Ins>tute of Technology, Lausanne, Switzerland Purpose The purpose of this presenta>on is to give an overview of the IOP measuring devices from the medieval >mes to the future. Main focus on the comparison of Goldmann Applana>on Tonometry (GAT) with Pascal Tonometry with the presenta>on of a new clinical study. Methods A clinical prospec>ve monocentric study: Office based study of consecu>ve 144 pa>ents (271 eyes) suffering from glaucoma or ocular hypertension. The IOP measurements were performed using GAT and Pascal tonometers. Central corneal thickness (CCT) was also measured. Introduc;on The importance of the intraocular pressure (IOP) is known since the medieval >mes. In the 19. century Albert von Graefe (182870) invented the first device that measured approxima>vely the IOP. It was an indenta>on tonometer measuring the eye pressure through the closed eye lid. Schiotz (1905) and Maklakoff (1885) further refined the concept. In 1957, Goldmann and Schmidt published the revolu>onary inven>on of an applana>on tonometer (Goldmann applana>on tonometer „GAT“) that became – and s>ll is the gold standard for measuring the IOP worldwide. Because of the progress in corneal surgery since the end of the 1970 and the growing knowledge that the corneal thickness and the corneal structure vary individually, the accuracy of the GAT was more and more ques>oned. It took another decade un>l other devices for measuring the IOP independently of the the cornea were developed. One of the most accurate measuring devices is the dynamic contour tonometer, (DCT) which will be presented in an overview of the new IOP measuring devices worldwide. Results From the 144 pa>ents (271 eyes) included in this office based clinical study the mean IOP GAT was 16.2 mm Hg, whereas the mean IOP Pascal was 19.5 mm Hg. The pa>ents treated with Prostaglandin analogs alone (93 eyes) or Prostaglandinanalogs in combina>on with other medica>ons (178 eyes) had a mean difference GATPascal of 3.2 mmHg and 3.3 mm Hg, respec>vely. The mean CCT of the 271 eyes was 544 micrometers. Conclusions The GAT is s>ll the gold standard but in the future IOP measuring devices, which are measuring the IOP independent of the CCT (for example Pascal Tonometry), will become more important in the glaucoma prac>ce. Caveat: The so called „Triggerfish“ contact lens measures a change of an eye and probably not the IOP! Too many ques>ons persist and need to be answered before this device can be used. Indenta;on tonometry by Von Graefe (1828 – 1870) Picture Ch Kniestedt, MD Indenta;on tonometry by Schiotz (1905) First tonometry by Alexei Maklakoff (1885) W = Counterpressure A = Flafened surface P = Pressure in the ball S = Tension of the surface of the tear liquid B = S>ffness of the cornea An external force indents a ball filled with a liquid. The indenta>on is deeper when the pressure in the ball is lower Goldmann H, Schmidt T: Ueber Applana>onstonometrie. Ophthalmologica 134, 221242, 1957 Goldmann and Schmidt (1957) Applana>ontonometry: W + S = P x A + B, but W=PxA With diameter A = 3.06 mm applana>on area 7.35 mm2 corneal thickness = 500 µm A plunger indents the cornea and the IOP is determinded by measuring how much the cornea is indented by a given weight Ocular Response Analyzer The cornea biomechanic proper>es, the corneal hysteresis is es>mated by measuring the force to indent the cornea in a double fashion with a pulse of 100 µs using a burst of air. The difference between the onward and backward applana>on reflects the corneal hysteresis. Y Robert, H Kanngiesser, Ch Kniestedt The applana>on is performed using a steady force. The measured area is converted into the IOP, a small area corresponds to a high IOP Dynamic Contour Tonometry (DCT) In the center of the >p a piezo electric pressure sensor measures IOP 100 x/sec. The DCT is adapted to the slitlamp and shows a dynamic con>nous IOP recording The ocular pulse amplitude is recorded The measurement of the IOP is independent of the cornea thickness and biomechanics proper>es Glaucoma diagnosis Primary Open Angle Glaucoma Pseudoexfolia>on Glaucoma Primary Angle Closure Glaucoma Other types of Glaucoma An>glaucoma medica>on Number of eyes Prostaglandin analogues 93 Beta blockers 12 Prostaglandin analogues/Beta blockers 45 Carbonate anhydrase inhibitor 4 Carbonate anhydrase inhibitor/Beta blockers 19 Alphaagonists 2 Alphaagonists/Beta blockers 2 Other Prostaglandin analogues/ combina>on 39 None 55
Transcript of Intraocular*pressure*(IOP)*measuring*devices*–from*the...
Intraocular pressure (IOP) measuring devices – from the past to the future
Frances Meier-‐Gibbons, MD1; Sylvain Roy, MD, PhD2, 3
1Glaucoma Prac>ce, Rapperswil, Switzerland, 2Montchoisi Clinic, Lausanne, Switzerland, 3Swiss Federal Ins>tute of Technology, Lausanne, Switzerland
Purpose The purpose of this presenta>on is to give an overview of the IOP measuring devices from the medieval >mes to the future. Main focus on the comparison of Goldmann Applana>on Tonometry (GAT) with Pascal Tonometry with the presenta>on of a new clinical study.
Methods A clinical prospec>ve monocentric study: Office based study of consecu>ve 144 pa>ents (271 eyes) suffering from glaucoma or ocular hypertension. The IOP measurements were performed using GAT and Pascal tonometers. Central corneal thickness (CCT) was also measured.
Introduc;on The importance of the intraocular pressure (IOP) is known since the medieval >mes. In the 19. century Albert von Graefe (1828-‐70) invented the first device that measured approxima>vely the IOP. It was an indenta>on tonometer measuring the eye pressure through the closed eye lid. Schiotz (1905) and Maklakoff (1885) further refined the concept. In 1957, Goldmann and Schmidt published the revolu>onary inven>on of an applana>on tonometer (Goldmann applana>on tonometer „GAT“) that became – and s>ll is-‐ the gold standard for measuring the IOP worldwide. Because of the progress in corneal surgery since the end of the 1970 and the growing knowledge that the corneal thickness and the corneal structure vary individually, the accuracy of the GAT was more and more ques>oned. It took another decade un>l other devices for measuring the IOP independently of the the cornea were developed. One of the most accurate measuring devices is the dynamic contour tonometer, (DCT) which will be presented in an overview of the new IOP measuring devices worldwide.
Results From the 144 pa>ents (271 eyes) included in this office based clinical study the mean IOP GAT was 16.2 mm Hg, whereas the mean IOP Pascal was 19.5 mm Hg. The pa>ents treated with Prostaglandin analogs alone (93 eyes) or Prostaglandinanalogs in combina>on with other medica>ons (178 eyes) had a mean difference GAT-‐Pascal of 3.2 mmHg and 3.3 mm Hg, respec>vely. The mean CCT of the 271 eyes was 544 micrometers.
Conclusions The GAT is s>ll the gold standard but in the future IOP measuring devices, which are measuring the IOP independent of the CCT (for example Pascal Tonometry), will become more important in the glaucoma prac>ce. Caveat: The so called „Triggerfish“ contact lens measures a change of an eye and probably not the IOP! Too many ques>ons persist and need to be answered before this device can be used.
Indenta;on tonometry by Von Graefe (1828 – 1870)
Picture Ch Kniestedt, MD
Indenta;on tonometry by Schiotz (1905)
First tonometry by Alexei Maklakoff (1885)
W = Counterpressure
A = Flafened surface
P = Pressure in the ball
S = Tension of the surface of the tear liquid
B = S>ffness of the cornea
An external force indents a ball filled with a liquid. The indenta>on is deeper when the pressure in the ball is lower
Goldmann H, Schmidt T: Ueber Applana>onstonometrie. Ophthalmologica 134, 221-‐242, 1957
Goldmann and Schmidt (1957)
Applana>ontonometry:
W + S = P x A + B, but
W = P x A
With diameter A = 3.06 mm
applana>on area 7.35 mm2
corneal thickness = 500 µm
A plunger indents the cornea and the IOP is d e t e r m i n d e d b y measuring how much the cornea is indented by a given weight
Ocular Response Analyzer
The cornea biomechanic proper>es, the corneal hysteresis is es>mated by measuring the force to indent the cornea in a double fashion with a pulse of 100 µs using a burst of air. The difference between the onward and backward applana>on reflects the corneal hysteresis.
Y Robert, H Kanngiesser, Ch Kniestedt
The applana>on is performed using a steady force. The measured area i s converted into the IOP, a small area corresponds to a high IOP
Dynamic Contour Tonometry (DCT)
In the center of the >p a piezo-‐electric pressure sensor measures IOP 100 x/sec.
The DCT is adapted to the slitlamp and shows a dynamic con>nous IOP recording
The ocular pulse amplitude is recorded
The measurement of t h e I O P i s independent of the cornea thickness and b i o m e c h a n i c s proper>es
Glaucoma diagnosis
Primary Open Angle Glaucoma
Pseudoexfolia>on Glaucoma
Primary Angle Closure Glaucoma
Other types of Glaucoma
An>glaucoma medica>on Number of eyes
Prostaglandin analogues 93
Beta blockers 12
Prostaglandin analogues/Beta blockers 45
Carbonate anhydrase inhibitor 4
Carbonate anhydrase inhibitor/Beta blockers
19
Alpha-‐agonists 2
Alpha-‐agonists/Beta blockers 2
Other Prostaglandin analogues/ combina>on
39
None 55
