NM3DPPFC – Onwards and Upwards!
Creating a DIY Retinal Camera: From Ophthalmoscopy to Innovation
My initial idea for creating a camera was to develop something that mimicked indirect ophthalmoscopy. But first, let me take a moment to explain the difference between direct and indirect ophthalmoscopy techniques.
Understanding Direct vs. Indirect Ophthalmoscopy
Direct ophthalmoscopy uses a handheld device called an ophthalmoscope to visualize the retina. This instrument features a peephole for viewing and shines light toward the eye, providing 15x magnification with a relatively limited field of view (FOV) that's typically restricted to the optic nerve and surrounding blood vessels. It's called "direct" because it provides direct illumination of the retina.
Indirect ophthalmoscopy works differently. This technique typically uses a headset that provides illumination, combined with a 20D lens to visualize the retina. The magnification is lower at 3x, but this provides a much wider FOV. It's called "indirect" because the retina isn't directly visualized—instead, a lens (the 20D lens) creates an image of the retina that can be observed.
The Inspiration Moment
I first had the opportunity to perform indirect ophthalmoscopy during my ophthalmology rotation with Dr. Felsted. While I was aware of the technique's existence, I had never tried it before since I didn't have access to the headset, lens, or willing patients needed for practice. My first few attempts weren't very successful, which is typical for beginners.
Dr. Felsted even tried using his smartphone to take a photo of the retina to help me visualize it better, but he wasn’t able to capture a clear image. That moment sparked an idea. I realized that this challenge could serve as the foundation for developing a practical camera solution.
Research and Discovery
After conducting some research and watching multiple YouTube videos, my suspicions were confirmed when I discovered this project on Instructables. The design featured a 3D-printed mount that attached a 20D lens to an iPhone, allowing the phone to capture photos of the retina. The setup used the iPhone's flash as the illumination source, though it did require the use of dilating eye drops.
The Quest for an Affordable Lens
To move forward with this project, I quickly realized I would need a 20D lens. A brief Google search revealed that professional-grade 20D lenses easily cost upwards of $400. At this price point, I turned to eBay to search for a more affordable alternative. For just $23, I became the proud owner of a 20D lens shipped from India.