S E E K

A Seniors' Eye Examination Kit for home use

7 months (October 2019 - April 2020)

Solo Project

Design Brief:

Development of a personalized smart product (personalized ophthalmic device) for ageing people/elderly

Specifically as a final year project, I was tasked to utilize the existing lab resources and external resources to undertake smart product development including: 1) Conceptual Design, Embodiment Design and Detail Design of the mechanical part in CAD environment, 2) Rapid prototyping of components by a 3D printer, 3) Equip the physical prototype with built-in sensors and embedded systems (purchase from market), 4) Realize at least one smart functionality of the product together with smartphone communication (i.e. mobile app development), 5) Employ design thinking processes backed by scientific theories and concepts to formulate a device design.

Motivations

World Health Organization (WHO) states that the proportion of the world’s population over 60 years will increase from 12% to 22% between 2015 and 2050. According to the Department of Statistics Singapore, the number of elderly residents aged 65 and above living alone will increase from 41,200 in 2015 to 83,000 by 2030. These projections form a clear problem statement: How can we improve the accessibility to eye care for our seniors?

Background

The eye can be split into its anterior segment (which consists of the iris, cornea, lens and more), and its posterior segment (which consists of the retina, optic nerve and more). There are 4 major leading causes of blindness due to age-related eye diseases such as 1) Cataract, 2) Age-related Macular Degeneration, 3) Glaucoma, and 4) Diabetic Retinopathy. Fortunately, these diseases can be prevented or treated with early diagnosis of the eye using today’s technology.

Current Eye Imaging Techniques:

There are 3 main methods to capture ocular images:

1) External Ocular Photography: to capture external eye structures and features (using a DSLR)

2) Direct and Indirect Ophthalmoscopy: to capture the fundus of the eye (using a direct and indirect ophthalmoscope)

3) Slit Lamp Examination: to capture the anterior and posterior segment of the eye with a beam of light (using a slit lamp microscope)

Current Smartphone-based Ophthalmic Devices:

Currently, there are at least 10 known smartphone-based ophthalmic device on the market. However, they are mostly built and designed to serve the communities of developing nations and expensive equipment used by health professionals (and hence not elderly-friendly).

Conceptualization

The principle of familiarity design in product design are employed to guide the form factor and style of interactions of the device. Form factors similar to a binoculars or goggles are explored. The style of interaction of a camera is adapted onto the proposed device. A thorough Function Analysis and Morphological Chart were generated to analyze the critical functions and features of the device.

System Design

Lens Configuration:

The most typical condensing lens used in indirect ophthalmoscopy and external ocular photography is a +20 Diopters lens. For this project, a +20D aspherical PMMA condensing lens from oDocs was used as the First Lens. This 20D PMMA lens has a working distance of 50mm and comes with anti-reflective coating. As most smartphones are equipped with a 26mm-equivalent lens for its main camera, the focal length of the Second Lens is assumed to be 26mm.

LED Illumination:

The white LED provides sufficiently bright and homogenous light with less heat produced. With a low power consumption, it is a durable light source which can last more than 100 000 hours without replacement. White LEDs have a wavelength of 400nm-700nm while IR LEDs have a wavelength of 940nm. As the human eye cannot perceive a wavelength of 850nm, pupillary constriction will not occur prior to the white flash when the infared (IR) LEDs are in use, and the camera can focus on the eye with the IR LEDs. A white light can then be flashed to illuminate the eye and capture a coloured photograph before the pupil can constrict. Thus, a combination of white and IR light is possible to enable non-mydriatic photography of the eye.

How does it works?

Four 3V white LEDs (connected in parallel) and four 1.6V IR LEDS (connected in series) are placed alternatively in a ring around the main condensing lens to provide the IR and flash illumination on the user’s eye. By creating a ring of LEDs, the angle of reflection will not coincide with the angle of incidence. When the circuit is powered, the IR LEDs will light up by default. Upon every release of the push button, the white LEDs flashes at a 80ms pulse and turns off the IR LEDs momentarily.

To test the flash illumination system of the prototype, the circuit is controlled by an Arduino Nano and powered by a 9V battery. To connect the device to the smartphone, an existing shutter remote is disassembled, and its internal PCB is used in the design of the circuitry. The intensity of the flash can be further controlled by adjusting the rotary potentiometer to fit different individuals’ comfort, eye colour and ambient illumination. Having an external flash illumination can ensure consistent illumination for each image taken.

As the flash exposure time is short, the area around the eye can be sufficiently lit without pupil constriction and the smartphone camera can capture the image with clarity.

App Interface

A prototype app with an elderly-friendly user interface is designed for easier navigation and controls. The app also helps to integrate related tele-ophthalmology services into SEEK.

Prototype Testing

The lens and LED configurations were assembled in a 3D-printed enclosure. The smartphone used in this experiment is a Samsung A30s smartphone. As a proof of concept, the sliding occluder was replaced with an opaque permanent occluder. Only the left eye is tested in this prototype. The colour of the prototype is not emphasized and the silicone outer cover is not included as well.

Three human subjects were then voluntarily recruited to test the device on actual human eyes. The images taken are generally well-lit. To prevent uneven lighting, it is observed that the eye examination procedure with this device needs to be done in a dimly lit environment. The low intensity flash illumination did not cause a reflection on the eyeball due to reflective miosis, but there are visible blue reflections from the lens for some images as shown. Images taken from Subject 2 and 3 are generally clear enough to observe the external features and anterior structures of the eye. However, without pharmacologic pupil dilation, the image quality is significantly affected by the pupil size.

Product Visualization

1/6

Conclusion

A longer life brings more opportunities and contributions for the aged, but the extent of these is heavily dependent on their health.

In conclusion, this project proposes a design of an ophthalmic device for the elderly, based on existing imaging and illumination systems. An adapted methodology using the principles of Familiarity Design and Analytical Hierarchy Process is employed for evaluating user preferences in product design. The assembly of the proposed ophthalmic device proves the feasibility of building a tele-ophthalmoscopic device for in-home use. Anterior segment imaging of the eye can be achieved by building an optical system (consisting of a lens, an external light source and a smartphone) with off-the-shelves components.