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http://eyenetra.com
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Shack-Hartmann Wavefront Sensor
Expensive; Bulky, Requires trained professionals
Wavefront aberrometer
6
Laser
Sensor
8
Displacement = Local Slope
of the Wavefront
Spot Diagram
Shack-Hartmann Wavefront Sensor
10
Spot Diagram on LCD
Inverse of Shack-HartmannUser interactively creates the Spot Diagram
Displace 25 points but 3 parameters
11
Spot Diagram on LCD
Inverse of Shack-HartmannUser interactively creates the Spot Diagram
Displace 25 points but 3 parameters
Eye
Relaxed Eye with Myopia
Blurred point
Red pointat infinity
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
12
Eye
Relaxed Eye with Myopia
Distinctimage points
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Pinholes
13
Red pointat infinity
Scheiner’s Principle
Eye
Relaxed Eye with Myopia
Virtual red pointat infinity
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
14
A
B
Distinctimage points
Display
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
15
Distinctimage points
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
16
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
17
d
Points overlap
Relaxed Eye with Myopia
perfect vision
myopia
hyperopia
~10cminfinity
Focusing Range
Eye
18
d
d
1
Point at infinity
Limitations
• Children
• Ability to align lines
• 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
25
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 -3.00 -1.00 1.00 3.00 5.00
Net
ra (D
)
Retinoscopy (D)
13 adults
-7.00
-5.00
-3.00
-1.00
1.00
3.00
5.00
7.00
-7.00 -2.00 3.00
Net
ra (D
)
Retinoscopy (D)
29 adults
LVPEI (India)NETRA vs Retinoscopy
Validation: Side by Side Trials
Unique, quantitative lens mapping
CATRA: Quantitative Cataract Maps
with: Erick Passos, Jan Zizka, Everett Lawson, Esteban Clua , Manuel M. Oliveira, Ramesh Raskar
Testing the Presence of Cataracts
34
Blin
kin
g p
atte
rns
on
Scr
ee
n
Cell Phone Display
Pinhole
Lens
36 years old female with Posterior Sub-Capsular (10%)
CATRA’s Opacity MapSlit-lamp
Retro-illumination
For the Future
• Ophthalmology 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
Corneal TopographerWavefront Aberrometer
Phoropter
Optometry Today
Snellen chartTrial set of lenses Lasers
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
Retinoscope w/
Lenses
Auto-refracto-
meter
Chart with
Lenses
In-Focus: Focometer Optiopia
Solo-health: EyeSite
NETRA
Technology Shining Light plus lenses
FundusCamera
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
Infinity
Perfect Vision System
Human Eye
Infinity
Subject can focusat infinity
10cm
Normal Vision
48
Accommodation Range
Myopia (nearsightedness)
Infinity
Subject cannot focusat far distances
10cm
Normal Vision
Myopia
Wrong focal point
49
Accommodation Range
Infinity
Human Eye
Myopia Correction
Infinity
Subject can focusat infinity
10cm
Normal Vision
Myopia
Divergent Lens
Corrected Myopia
50
Accommodation Range
Infinity
Human Eye
Hyperopia (farsightedness)
Infinity 10cm
Normal Vision
Myopia
Hyperopia
Wrong focal point
51
Accommodation Range
Infinity
Human Eye
Hyperopia Correction
Infinity
Accommodation Range
10cm
Normal Vision
Myopia
Hyperopia
Convergent Lens
52
Corrected Hyperopia
Infinity
Human Eye
Refractive Errors and Shifted Range
Perfect vision
Myopia
Hyperopia
10cmInfinity
Need to measure
54
1m 33cm Distance
Refractive Errors and Shifted Range
Perfect vision
Myopia
Hyperopia
10cmInfinity
55
-10D0D
Diopter = 1/Distance
-3D-1D
1m 33cm
+1D+3D
Distance
Diopter
Astigmatism: angle-dependent refractive error
http://www.elizabethpope.co.uk/eyeinfo/astigmatism.html 56
Astigmatism: angle-dependent refractive error
http://www.elizabethpope.co.uk/eyeinfo/astigmatism.html 57
Astigmatism: angle-dependent refractive error
http://www.elizabethpope.co.uk/eyeinfo/astigmatism.html 58
Measuring the Accommodation Range
62
Perfect vision
~10cmInfinity
Myopia
Hyperopia
Step 1: Far limit Step 2: Near limit
Measuring the Accommodation Range
63
Perfect vision
~10cmInfinity
Myopia
Hyperopia
Step 1: Far limit Step 2: Near limit
Measuring the Accommodation Range
64
Perfect vision
~10cmInfinity
Myopia
Hyperopia
Step 1: Far limit Step 2: Near limit
Points overlap
A
B
Display
Accommodated Eye
66
Virtual pointgetting closer
Move points towardseach other
Subject Accommodates to fix the “blur”
Points overlap
A
B
Display
Accommodated Eye
67
Virtual pointgetting closer
Move points towardseach other
Subject Accommodates to fix the “blur”
Points overlap
A
B
Display
Accommodated Eye
68
Virtual pointgetting closer
Move points towardseach other
Subject cannot accommodate more than the previous point
Patterns for Alignment Task
Displayed
Subject view
Displayed
Subject view
69
Visual Cryptography
A B A B A B A B A B
A B A B A B A B A B
[NaorShamir94]
Patterns for Alignment Task
Displayed
Subject view
Displayed
Subject view
70
Visual Cryptography
A B A B A B A B
A B A B A B A B A B
A B
[NaorShamir94]