Advancement in tonometry

1. Implantable IOP Sensors
PRESENTED BY:
Kartik Kumar Gupta
BV(DU)MC School Of Optometry-2nd year

2. Presentation Layout
1. Introduction on IOP and Tonometry
2. Different Implantable IOP Sensor
3. Pros and Cons of implantable IOP Sensor
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3. Intraocular Pressure:
The intraocular pressure (IOP) refers to the pressure exerted
by intraocular contents on the coats of the eyeball.
Tonometry:
Tonometry is a clinical technique that provides a
measurement of the tension of the eye, which includes the
combined resistance to deformity of its coat and the IOP.
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4. Implantable IOP Sensors
1. Contact lens sensors:
In the study a smart contact lens sensor could help monitor
biomarkers for IOP, diabetes mellitus, and other health
conditions.
Despite numerous studies in the last several decades, the
biggest drawback with conventional contact lenses was thought
to be poor wearability.
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5. Contact Lens Sensor
The electrodes used were opaque, and therefore obscure
the view when wearing it.
Professor Park and research team solved these issues by
developing a sensor based on transparent and flexible
electrodes made of transparent graphene sheets and metal
nanowires.
This electrode is glucose monitoring sensors.
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6. Contact Lens Sensor
IOP measurement can be achieved using dielectric layer.
The thickness of this layer decreases as IOP increases and
vice-versa.
The IOP sensor, embedded in contact lenses senses this and
transmits the information to the wireless antenna.
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7. Contact Lens Sensor
According to research team, the sensor characteristics are
not affected by components of tear and the contact lens
deformity.
It was observed that the live rabbit did not show any
abnormal behaviour when wearing the contact lens sensor.
This study can be used to diagnose diseases (diabetes and
glaucoma) by implementing two types transparent electronic
sensors in the production of smart contact lens sensor said
professor Park.
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11. 2. IOP-IOL Probe
The intraocular lens implant can be looked upon as a probe
into the space of the eye.
A sensor is presented for continuous monitoring of IOP
incorporated in the haptics of an IOL.
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12. IOP-IOL Probe
The sensor consist of a capacitative spiral circuits, needing
no energy, correlating its resonance frequency to the actual
IOP.
This resonance frequency is remotely and non-invasively
detected by an external device located in spectacle frame.
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14. 3. Choroid-IOP Sensor
Small changes in IOP can be measured by a sensor in contact
with the surface of the choroids.
The sensors have been tested in two modes:
Fixed: Using the sensor in contact with choroid at 0-2mm
depth of sclera surface.
Sutured: Sensor sutured to the surface of the sclera with the
probe touching the choroidal surface.
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15. Intraocular Pressure Measurement At The
Choroid Surface: A Feasibility Study With
Implications For Implantable Microsystems
Raed N Rizq, Woo-Hyek Choi, David Eilers, Martha M Wright,
Babak Ziaie
Abstract:
 Aims—To demonstrate that a sensor, which is inserted
through the sclera and placed in intimate contact with the
choroid, can reliably detect changes in the intraocular
pressure (IOP).
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16. Methods:
A manometer was used to control the IOP of three cadaver
eyes in steps of 7 mm Hg.
 A piezoresistive pressure sensor was used to measure the
pressure at the choroid through a 2.5 mm diameter hole that
was surgically removed from the sclera.
 Data were collected for two configurations; with the sensor:
(i) rigidly attached to a miniature positioning stage, and
(ii) sutured to the sclera.
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17. Results:
Both configurations accurately tracked the manometer
pressure from 10 mm Hg to 47 mm Hg.
 For the fixed sensor cases, the average divergence between
the pressure measured at the choroid and in the anterior
chamber was 0.8 mm Hg for the three eyes.
For the sutured sensor case, the average divergence was 2.1
mm Hg—although a significant portion of this was attributed
to an initial onset.
The standard deviations at each pressure level for all of the
choroid measurements were under 1.0 mm Hg.
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18. Conclusions:
Small changes in IOP can be accurately measured by a
sensor in contact with the surface of the choroid, for both a
fixed sensor configuration and for a sensor sutured to the
sclera.
 These results are the first step in the realization of a
surgically implantable microsensor to monitor IOP for
patients suffering from low tension and other difficult to
manage forms of glaucoma.
(Br J Ophthalmol 2001;85:868–871)
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19. References:
1. Anatomy and physiology of eye – AK Khurana
2. Clinical procedure in optometry – J.Boyd
3. Wearable smart sensor systems integrated on soft contact
lenses for wireless ocular diagnostics. Nature
communication, 2017;8: 14997 DOI:
10.1038/ncomms14997
4. Svedbergh B, et al. Acta Ophthalmol (Copenh). 1992.
5. Diagnosis and management of glaucoma – R Ramakrishan
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