Smartphone Fundus Camera

Intro: Smartphone Fundus Camera

Intro

Most of us have two of the three major components of fundus camera in out pockets at all times, a CCD camera and a LED light. These of course are on our smartphones. What would happen if we found a way to add the third piece of this equation to our phone, the right lens. This was the central focus of my time as an Artist in Residence at Autodesk's Pier 9.

Inspiration

My inspiration for the project was my late grandma Mimi. Watching her gradually lose her vision to glaucoma was really painful, and building this project proved very cathartic. Glaucoma is traditionally diagnosed through checking eye pressure, however there are a whole plethora of other diseases detectable through fundus photography. So without further ado lets begin our journey into the back of the eye.

STEP 1: Research, Research & More Research

Optical Physics

Is really hard! Of all the engineering disciplines out there, I've heard this one be referred to as "black magic" the most often. Before undertaking this project I had zero optics knowledge and I would still place my self in the beginner category. Arm yourself with as much knowledge as possible, Modern Optics is a good place to start but gets a little to advanced for what we need. Throughly understand the Lens Makers Equations is a must and being able to to Ray Tracing would also be a huge boon.

STEP 2: First Prototype

Just a Stick

My first prototype was just the lens mounted on a stick mounted to an iPhone, very technologically advanced. However, it allowed me to place the lens at difference distances from the phone camera, experimenting with the optics before I understood the physics behind focal distances, and where images are made.

STEP 3: Optical Test Stand

Theory into Practice

I designed an built an optical test stand to help turn the theory and research I've been rapidly ingesting into practice. Giving me the ability to test various lenses and rapidly reposition the focal length was super useful when trying to find the optimal distance of the lens.

Fake Eyes

The Ophthalmologic Test eye allowed me to simulate various lighting conditions through a constand pupil diameter. When light shines into your eye, your pupil will constrict, which is good for your eye but bad for trying to see your retina. However this eye has a fixed pupil dilation at 6mm which is actually slightly smaller than a real dilated eye.

STEP 4: Second Prototype

Flat Pack

I was inspired by two other Artist in Residence's Prisca Visbol who was working on what was essentially flat pack fashion. Could you design this device to be shipped in mass quantities, like IKEA, without taking up a lot of space? Using a laser cutter I went and explored this idea. Through a couple iteration the answer appeared to be mostly yes, if not accounting for the lens.

STEP 5: Raspberry Pi Prototype

Using Raspberry Pi Camera

My thought was that an infrared camera would allow testing without the use of dialating drops. Allowing light into the eye that did make the pupil constrict. While I love the case I designed for this piece the overall design was flawed from the beginning, because of one main factor.....Auto Focus.

Every persons eye is a little different, their myopic error creates images that focus on different planes. The Autofocus in your camera helps get rid of that easily, but with the raspberry pi camera it was a very manual process that was constantly in flux.

STEP 6: Final Prototype: Part 1

Form Model

Using foam I carved out a basic rectangle and then slowly started carving away the corners. I made a couple different sizes and a couple different shapes. Then I gave the models to friends of both genders to see how the prototypes felt in their hands. Shockingly both sets of friends preferred the same smaller, rounded edges model. With this in mind I went to CAD.

STEP 7: Final Prototype: Part 2

Filling

It took a couple tries to get this printed properly but once done I turned to Prototyping and Modelmaking for 3D printing finishing techniques. I used bondo for fill in the really large filament marks, especially on the first layer. Use an extremely small amount of filler. I've found that just smoothing out the print through high grit sanding was better than immediately going to body filler.

Painting

I did two rounds of primer with minimal sanding in between, and then a final coat, followed by some high grit sand paper to give the final piece a more plastic feel. The goal was to imitate an injection molded piece.

STEP 8: Final Prototype: Part 3

Testing

The first test of this final prototype went so much better than I ever could have imagined. Using the Filmic Pro app to lock focus and exposure I was able to finely tune the retina pictures we were getting on our smartphone. Zooming in to approximately 2x we lost a bit of resolution because of the digital zoom but having the retina fill up the phone screen was pretty awesome.

Shoot at 30fps had some interesting benefits, one being that I could go back into very clear sections of the video and use photoshop to stitch them together. It was pretty amazing to see the noise drain out of the images and veins you could barely see in initial photographs became uniquely visible. It was a very cool experience to say the least.

Wrapping it up

For me this project is far from over. Eventually creating a $10 eye exam just seems like a project I could sink my teeth into for many years to come. Thank you to everyone at Pier 9 for being helpful and amazing, none of this would be possible without you all :)

Comments

[sudhirkothari]

hi..fantastic ida. Has anyone made it?

[Gilius]

Great work! Will you be sharing the CAD files or at least the calculations?

[zacharyianhoward]

Gonna definitely share the calculations, have a ton of work on my plate, but will be perfecting this instructable as often as I can

[daniel.delarco]

Still waiting LOL

[BenoitM8]

Where can u download 3d printing parts plz

[daniel.delarco]

In thingiverse LOL

[PeterB464]

Great Project! what type of lense did you use for the final design? Did it differ from the one you used trying the rasperry pi?

[mhasan12]

Can I use other 10/12Diopter lens?

[hammondtmk]

Hi, what is the distance of the 20D lens from the iPhone. We do a lot of vision screening and this would be of great help to us.

[hammondtmk]

Hi, what is the distance of the 20D lens from the iPhone. We do a lot of vision screening and this would be of great help to us.

[MerlinMakes]

i find it funny that someone here calls it lazy to link us to a web page on wikipedia expressly explaining what a fundus camera is..... and yet they are too lazy to click the dang link....

seriously, dude, if you want an explanation, you're going to get a paragraph or three, regardless of whether it's here or there. if that's above your head, then how do you hope to read the rest of the instructable?

author, what are you using for the lenses?

[fbonneau13]

Great idea indeed, and a lot of family physician would be interested in an easy to use, cheap but reliable device that can be paired to an iPhone like this one! Keep us informed, and consider a Kickstarter if you plan to go in production...!

[shallnot]

Is it so difficult to write a one sentence summary of a 'fundus camera' instead of taking the lazy route and forcing all of us who don't know to click on a link and reading what's there to form our own summary? Better that 1 person--the author--take the time to do it than n readers.

Yes, you could say that in the "Inspiration" section you mention glaucoma so that one could infer that this has something to do with providing aid to those with compromised vision.

In general, the first paragraph of this comment could be said of any "instructable" dealing with an uncommon thing.

[GreedyGoat]

I agree with Shallnot, I still don't know what "Fundus Camera" means, don't have time to waste nor desire to look it up.

[Dwargh]

I helped myself by googling "fundus photography" in my mother language ;)

[LowerT1]

I'll assume, until you correct me, that you do know what a camera is.

The "fundus" is the interior of the eye (which is hollow). It includes the retina, which is the back portion that deflects the light and color passing through the pupil and lens. Being able to visualize and document what the fundus looks like is very important in the diagnosis of various eye diseases, expecially those that cause blindness. Currently, the equipment that can do this costs thousands of dollars.

[GreedyGoat]

Thank you for the explanation. Now I have learned something new today.

[zacharyianhoward]

LowerT1 you are winning. Thanks for clarifying this for other members of the community :)

[gdriver]

I am surprised you had time to express your dissatisfaction.

[zacharyianhoward]

The links are for inspired individuals to learn more about the complex optical physics and eye anatomy required for a fully grok this instructable.