Method of testing a surgical system
View Patent ↗A method for direct indication of the IOP level without requiring an additional pressure transducer being introduced into the irrigation path. The method of the present invention estimates resistance ratio for a particular setup, and thus does not assume a typical value; the estimation is performed in a pre-operational configuration that is the closest possible to the surgical configuration.
1. A method for determining an irrigation path resistance ratio in an irrigation system having an irrigation pressure sensor, comprising the steps of:
a) connecting a source of irrigation fluid to a surgical handpiece through an irrigation line, the source of irrigation fluid under control of a surgical system;
b) connecting a source of aspiration vacuum to the surgical handpiece through an aspiration line, the source of aspiration under the control of the surgical system;
c) installing a test chamber on the surgical handpiece so as to provide a closed fluid path from the source of irrigation fluid to the source of aspiration vacuum;
d) exposing the test chamber to a vacuum generated by the source of aspiration vacuum by aspirating a known fluid volume, while closing the irrigation line;
e) refilling the test chamber by opening the irrigation line;
f) monitoring a pressure recovery profile in one of the irrigation or aspiration lines;
g) detecting a characteristic test chamber refill segment in the monitored pressure recovery profile;
h) determining an irrigation line pressure during the detected test chamber refill segment, as an irrigation pressure sensor (IPS) reading during the refilling of the test chamber;
i) determining a pressure drop from the source of irrigation fluid to the irrigation pressure sensor during the detected test chamber refill segment;
j) determining a pressure drop from the irrigation pressure sensor to the test chamber during the detected test chamber refill segment; and
k) using the pressure drop from the source of irrigation fluid to the irrigation pressure sensor during the detected test chamber refill segment and the pressure drop from the irrigation pressure sensor to the test chamber during the detected test chamber refill segment to determine the irrigation path resistance ratio (K R ) of a resistance to irrigation flow from the source of irrigation fluid to the irrigation pressure sensor to a resistance to irrigation flow from the irrigation pressure sensor to the test chamber.
2. The method of claim 1 , wherein the resistance ratio K R is calculated using the following equation:
K
R
=
R
ADMIN
R
IRR
=
Δ
P
ADMIN
Δ
P
IRR
=
P
SOURCE
0
-
P
IPS
0
P
IPS
0
-
P
TIP
0
=
P
SOURCE
0
-
P
IPS
0
P
IPS
0
-
0
=
P
SOURCE
0
P
IPS
0
-
1
Where
:
P
SOURCE
0
-
irrigation
source
pressure
during
the
test
,
P
IPS
0
-
IPS
reading
during
the
test
chamber
refill
,
P
TIP
0
-
pressure
at
the
handpiece
tip
during
test
chamber
refill
,
≈
0
mm
Hg
.
3. A method for estimating intraocular pressure (IOP) during ophthalmic surgery, comprising the steps of:
a) connecting a source of irrigation fluid to a surgical handpiece through an irrigation line, the source of irrigation fluid having a pressure under control of a surgical system and a pressure in the irrigation line being monitored by an irrigation pressure sensor (IPS);
b) connecting a source of aspiration vacuum to the surgical handpiece through an aspiration line, the source of aspiration vacuum under the control of the surgical system;
c) installing a test chamber on the surgical handpiece so as to provide a closed fluid path from the source of irrigation fluid to the source of aspiration vacuum;
d) exposing the test chamber to a vacuum generated by the source of aspiration vacuum by aspirating a known fluid volume, while closing the irrigation line;
e) refilling the test chamber by opening the irrigation line;
f) monitoring a pressure recovery profile in one of the irrigation or aspiration lines;
g) detecting a characteristic test chamber refill segment in the monitored pressure recovery profile;
h) determining an irrigation line pressure during the detected test chamber refill segment as an irrigation pressure sensor reading during the refilling of the test chamber;
i) determining a pressure drop from the source of irrigation fluid to the irrigation pressure sensor during the detected test chamber refill segment;
j) determining a pressure drop from the irrigation pressure sensor to the test chamber during the detected test chamber refill segment;
k) using the pressure drop from the source of irrigation fluid to the irrigation pressure sensor during the detected test chamber refill segment and the pressure drop from the irrigation pressure sensor to the test chamber during the detected test chamber refill segment to determine the irrigation path resistance ratio (K R ) of a resistance to irrigation flow from the source of irrigation fluid to irrigation pressure sensor to a resistance to irrigation flow from the irrigation pressure sensor to the test chamber; and
l) estimating the intraocular pressure in an eye during surgery based on the determined irrigation path resistance ratio, the irrigation source pressure and a monitored irrigation pressure sensor reading.
4. The method of claim 3 , wherein the resistance ratio K R is calculated using the following equation:
K
R
=
R
ADMIN
R
IRR
=
Δ
P
ADMIN
Δ
P
IRR
=
P
SOURCE
0
-
P
IPS
0
P
IPS
0
-
P
TIP
0
=
P
SOURCE
0
-
P
IPS
0
P
IPS
0
-
0
=
P
SOURCE
0
P
IPS
0
-
1
Where
:
P
SOURCE
0
-
irrigation
source
pressure
during
the
test
,
P
IPS
0
-
IPS
reading
during
the
test
chamber
refill
,
P
TIP
0
-
pressure
at
the
handpiece
tip
during
test
chamber
refill
,
≈
0
mm
Hg
.
5. The method of claim 3 wherein the intraocular pressure is estimated using the following equation:
P
IOP
=
P
IPS
-
Δ
P
IRR
=
P
IPS
-
Δ
P
ADMIN
K
R
=
P
IPS
-
P
SOURCE
-
P
IPS
K
R
=
(
K
R
+
1
)
P
IPS
-
P
SOURCE
K
R
Where
:
P
IOP
-
current
IOP
,
P
SOURCE
-
current
irrigation
source
pressure
,
P
IPS
-
current
IPS
reading
.
6. An ophthalmic surgical system, comprising:
a surgical handpiece;
a source of irrigation fluid coupled to the surgical handpiece through an irrigation line, wherein the surgical system is configured to control a pressure of the source of irrigation fluid;
an irrigation pressure sensor coupled to the irrigation line, wherein the irrigation pressure sensor is configured to measure a pressure in the irrigation line; and
a source of aspiration vacuum coupled to the surgical handpiece through an aspiration line, wherein the surgical system is configured to control the source of aspiration vacuum;
wherein the surgical system is configured to estimate an intraocular pressure (IOP) in an eye during surgery based on a determined irrigation path resistance ratio of the surgical system, an irrigation source pressure of the source of irrigation fluid, and a monitored irrigation pressure sensor reading from the irrigation pressure sensor.
7. The ophthalmic surgical system of claim 6 , wherein the irrigation path resistance ratio is determined during a priming cycle of the surgical system.
8. The ophthalmic surgical system of claim 6 , wherein the irrigation path resistance ratio is determined using a test chamber by aspirating the test chamber, refilling the test chamber, detecting a characteristic test chamber refill segment in a monitored pressure recovery profile during the refill, and using a determined pressure drop from the source of irrigation fluid to the irrigation pressure sensor during the detected test chamber refill segment and a determined pressure drop from the irrigation pressure sensor to the test chamber during the detected test chamber refill segment to determine the irrigation path resistance ratio (K R ) of a resistance to irrigation flow from the source of irrigation fluid to irrigation pressure sensor to a resistance to irrigation flow from the irrigation pressure sensor to the test chamber.
9. The ophthalmic surgical system of claim 6 , wherein the resistance ratio K R is calculated using the following equation:
K
R
=
R
ADMIN
R
IRR
=
Δ
P
ADMIN
Δ
P
IRR
=
P
SOURCE
0
-
P
IPS
0
P
IPS
0
-
P
TIP
0
=
P
SOURCE
0
-
P
IPS
0
P
IPS
0
-
0
=
P
SOURCE
0
P
IPS
0
-
1
Where
:
P
SOURCE
0
-
irrigation
source
pressure
during
the
test
,
P
IPS
0
-
IPS
reading
during
the
test
chamber
refill
,
P
TIP
0
-
pressure
at
the
handpiece
tip
during
test
chamber
refill
,
≈
0
mm
Hg
.
10. The ophthalmic surgical system of claim 6 , wherein the intraocular pressure is estimated using the following equation:
P
IOP
=
P
IPS
-
Δ
P
IRR
=
P
IPS
-
Δ
P
ADMIN
K
R
=
P
IPS
-
P
SOURCE
-
P
IPS
K
R
=
(
K
R
+
1
)
P
IPS
-
P
SOURCE
K
R
Where
:
P
IOP
-
current
IOP
,
P
SOURCE
-
current
irrigation
source
pressure
,
P
IPS
-
current
IPS
reading
.
11. The ophthalmic surgical system of claim 6 ,
wherein the surgical system further comprises a drainage bag and a pump; and
wherein, during surgery, the surgical handpiece is configured to be held within the eye such that there is continuous fluid communication from the source of irrigation fluid to the drainage bag through the irrigation line, surgical handpiece, aspiration line, and pump.