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1
Health Power to the People
2
NETRA: Interactive Display for Estimating Refractive Errors
and Focal RangeVitor Pamplona Ankit Mohan Manuel M. Oliveira Ramesh Raskar
3
Millions have poor vision, but are not getting corrected…
Kenya
India
6.5 Billion people
4.5B have a cell phone
2B haverefractive errors
0.6B have URE
Photography in 1960s
Photo: Illana TamirPhoto: Roboppy
Today, cameras are everywhere
Photo: Derek K. Miller
Photo: Tyler
Photo: John Kannenberg
Corneal TopographerWavefront Aberrometer
Phoropter
Optometry Today
Snellen chartTrial set of lenses Lasers
NETRA: low-cost easy-to-use clip on for cell phones
Do the test at home, by yourself, in 2 minutes
8
Shack-Hartmann Wavefront Sensor
Expensive; Bulky, Requires trained professionals
Wavefront aberrometer
Shack-Hartmann Wavefront Sensor
Laser
Sensor Microlens Array
Planar Wavefront
Spot Diagram
10
Laser
Sensor
Displacement = Local Slope
of the Wavefront
Spot Diagram
Shack-Hartmann Wavefront Sensor
11
NETRA = Inverse of Shack-Hartmann
Spot Diagram on LCD
Cell Phone Display
Eye Piece
12
Spot Diagram on LCD
Inverse of Shack-HartmannUser interactively creates the Spot Diagram
Displace 25 points but 3 parameters
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Spot Diagram on LCD
Inverse of Shack-HartmannUser interactively creates the Spot Diagram
Displace 25 points but 3 parameters
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Human Eye
Human EyeCornea(~40D) Crystalline lens
(10~20D)
Retina
15
Human Eye
Human EyeCornea(~40D) Crystalline lens
(10~20D)
RetinaAccommodation
16
Infinity
Perfect Vision System
Human Eye
Infinity
Subject can focusat infinity
10cm
Normal Vision
Accommodation Range
17
Myopia (nearsightedness)
Infinity
Subject cannot focusat far distances
10cm
Normal Vision
Myopia
Wrong focal point
Accommodation Range
Infinity
Human Eye
18
Myopia Correction
Infinity
Subject can focusat infinity
10cm
Normal Vision
Myopia
Divergent Lens
Corrected Myopia
Accommodation Range
Infinity
Human Eye
19
Hyperopia (farsightedness)
Infinity 10cm
Normal Vision
Myopia
Hyperopia
Wrong focal point
Accommodation Range
Infinity
Human Eye
20
Hyperopia Correction
Infinity
Accommodation Range
10cm
Normal Vision
Myopia
Hyperopia
Convergent Lens
Corrected Hyperopia
Infinity
Human Eye
22
Refractive Errors and Shifted Range
Perfect vision
Myopia
Hyperopia
10cmInfinity
Need to measure
1m 33cm Distance
23
Refractive Errors and Shifted Range
Perfect vision
Myopia
Hyperopia
10cmInfinity
-10D0D
Diopter = 1/Distance
-3D-1D
1m 33cm
+1D+3D
Distance
Diopter
24
Eye
Relaxed Eye with Myopia
Blurred point
Red pointat infinity
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
25
Eye
Relaxed Eye with Myopia
Distinctimage points
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Pinholes
Red pointat infinity
Scheiner’s Principle
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Eye
Relaxed Eye with Myopia
Virtual red pointat infinity
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
A
B
Distinctimage points
Display
27
Relaxed Eye with Myopia
A
B
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Virtual red pointat finite distance
Move spots towards each
other
Display
Eye
Distinctimage points
28
B
A
Points overlap
Relaxed Eye with Myopia
Display
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Eye
Virtual red pointat finite distance
Move spots towards each
other
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B
A
Points overlap
Relaxed Eye with Myopia
Display
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Eye
Virtual red pointat finite distance
Move spots towards each
other
d
30
Points overlap
Relaxed Eye with Myopia
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Eye
d
d
1
Point at infinity
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Distinctimage points
Relaxed Eye with Hyperopia
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
A
B
Display
Virtual red pointat infinity
Eye
33
Points overlap
Relaxed Eye with Hyperopia
Virtual point“beyond” infinity
Move spots away from each other
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Display
A
B
Display
34
Points overlap
Relaxed Eye with Hyperopia
Virtual point“beyond” infinity
Move spots away from each other
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
35
NETRA: Using pinholes
Patterns on an LCD
Pinhole array
36
f
Patterns on an LCD
Microlens array
NETRA: Using Lens to Increase Light
tda
fc
2
t
a
Pixel Pitch
Virtual Depth
37
Interactive Method
Farthest Focal Point(myopia, hyperopia)
38
Interactive Method
Farthest Focal Point(myopia, hyperopia)
39
Interactive Method
Farthest Focal Point(myopia, hyperopia)
40
Overview• Inverse of Shack Hartmann Wavefront Sensor• Hi-res displays + interaction
• Measuring Spherical Error• No moving parts, lasers• Blur -> Alignment problem• ~ Lightfield Display for Single Eye
• Astigmatism• Novel Patterns• Focal Range• User Study
41
Astigmatism: angle-dependent refractive error
http://www.elizabethpope.co.uk/eyeinfo/astigmatism.html
42
Astigmatism: angle-dependent refractive error
http://www.elizabethpope.co.uk/eyeinfo/astigmatism.html
43
Astigmatism: angle-dependent refractive error
http://www.elizabethpope.co.uk/eyeinfo/astigmatism.html
44
Refractive Power as a Function of Angle
Cylinder SphereAxis Cyl.Unknowns:
SCP )(sin( 2
45
Astigmatism
Cross or points may never meet with a 1d search !
46
Astigmatism
Lines reduce the problem to a 1d search
47
Interactive Method
Farthest Focal Point(myopia, hyperopia, astigmatism)
48
Interactive Method
Farthest Focal Point(myopia, hyperopia, astigmatism)
49
Interactive Method
Farthest Focal Point(myopia, hyperopia, astigmatism)
50
Interactive Method
Farthest Focal Point(myopia, hyperopia, astigmatism)
51
Interactive Method
Farthest Focal Point(myopia, hyperopia, astigmatism)
52
Measuring the Accommodation Range
Perfect vision
~10cmInfinity
Myopia
Hyperopia
Step 1: Far limit Step 2: Near limit
53
Measuring the Accommodation Range
Perfect vision
~10cmInfinity
Myopia
Hyperopia
Step 1: Far limit Step 2: Near limit
54
Measuring the Accommodation Range
Perfect vision
~10cmInfinity
Myopia
Hyperopia
Step 1: Far limit Step 2: Near limit
55
Points overlap
A
B
Display
Virtual Point at the far limit
Relaxed Eye
56
Points overlap
A
B
Display
Accommodated Eye
Virtual pointgetting closer
Move points towards each other
Subject Accommodates to fix the “blur”
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Points overlap
A
B
Display
Accommodated Eye
Virtual pointgetting closer
Move points towards each other
Subject Accommodates to fix the “blur”
58
Points overlap
A
B
Display
Accommodated Eye
Virtual pointgetting closer
Move points towards each other
Subject cannot accommodate more than the previous point
59
Patterns for Alignment Task
Displayed
Subject view
Displayed
Subject view
Visual Cryptography
A B A B A B A B A B
A B A B A B A B A B
[NaorShamir94]
60
Patterns for Alignment Task
Displayed
Subject view
Displayed
Subject view
Visual Cryptography
A B A B A B A B
A B A B A B A B A B
A B
[NaorShamir94]
61
Summary of Interaction
Farthest Point(myopia, hyperopia, astigmatism)
Nearest Point(presbyopia)
Accommodation Range
Phoropter
Snellen chart
Trial lenses
Reading Charts• Accuracy
– Sharpness Estimation is subjective– Brightness affects results– Pupil size variation and DoF
• Cost– Trial Lens Set > $150– Bulky
Retino scope w/
Lenses
Auto-refracto-
meter
Chart with
Lenses
In-Focus: Focometer Optiopia
Solo-health: EyeSite
NETRA
Technology Shining Light plus lenses
Fundus Camera
Moving lenses + target
Moving lenses + target
Reading chart on monitor
Cellphone + eyepiece
Cost to buy $2,000* ~$10,000 ~$100 ~$495 ~$200 -- $30
Cost per test ~$36 ~$36 ~$5 -- -- -- ~$1
Data capture No Comp. No No No Comp. Phone
Mobility <500g >10Kg 2kg 1kg <5kg >10Kg <100g
Speed Fast Fast Medium Medium -- Fast Fast
Scalability No No No Yes Probably No Yes
Accuracy 0.15 0.15 0.5 0.75 -- -- <0.5
Self evaluation No No Yes Yes Yes Yes Yes
Electricity Req No Yes No No -- Yes No
Astigmatism Yes Yes Yes/No No -- Yes Yes
Network No Yes No No No Yes Yes
Training High High High Medium Medium Low Low
* Phoropter-based: $5,000.00
Needs expert, Moving parts, Shining lasers
64
Limitations
• Children• Ability to align lines
• Single Eye test– Other eye for convergence-forced accommodation
• Resolution is a function of the display DPI– Samsung Behold II – 160 DPI – 0.35D– Google Nexus One – 250 DPI – 0.2D– Apple iPhone 4G – 326 DPI – 0.14D
BBC CNN NBC
MIT News
Gizmodo
O Estado de SP - Brazil
NY Times Time - Wellness
Media Coverage
Confidential 66
NETRA Prototypes Worldwide29 partners in 14 countries.
Clinical Testing Partners
NETRA Team at LVPEI, India
OneSight, Kenya
Tufts U. (Boston) NETRA vs Manifest Refraction
-5.00 -4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
Retinoscopy (D)
Net
ra (D
)
13 adults
-7.00 -5.00 -3.00 -1.00 1.00 3.00 5.00 7.00
-7.00
-5.00
-3.00
-1.00
1.00
3.00
5.00
7.00
Retinoscopy (D)
Net
ra (D
)
29 adults
LVPEI (India)NETRA vs Retinoscopy
Validation: Side by Side Trials
Preventable Blindness
WHO 2004
Unique, quantitative lens mapping for size and density of eye opacities
CATRA: Cataract Screening Tool
Testing the Presence of Cataracts
73
Blin
king
patt
erns
on
Scre
en
Cell Phone Display
Pinhole
Lens
Point Spread Function Mapping
74
Blin
king
patt
erns
on
Scre
en
Cell Phone Display
Pinhole
Lens
Point Spread Function Mapping
75
Blin
king
patt
erns
on
Scre
en
Cell Phone Display
Pinhole
Lens
Traditional User Driven
Mass-use Devices Scientific Instruments
For the Future• Ophtalmology for Masses
– >.5 billion URE. > 2.5 billion RE. -> Devices for all
• Quality of phones (resolution) will increase exponentially
• New features (recently cataracts, next Retinal Netra)
• Smart phones will take over the market in developing world countries like India in next 5 years.
• Hardware store
EHREHR
DeliveryDeliveryDiagnosticDiagnostic EyecareProvidersEyecare
Providers
New Ecosystem
Asynchronous
Medical IT Systems
NETRAhttp://eyenetra.com