Under long exposure to microgravity, hyperopic shift in the vision of astronauts is well documented, which affects near vision—a crucial ability needed to operate a space vehicle. Although the observed hyperopic shift can be corrected with eyeglasses, the time course of this progression is poorly understood and of high interest. A barrier to elucidating this phenomenon is the current approaches used to measure ocular axial length, such as high-frequency ultrasound, which have poor repeatability.

Technologies that are highly repeatable and readily available in the clinic, such as autorefractors and optical biometers, do not meet the portability (desktop form factors, 50 pounds) and durability (sensitive to shock and movement due to internal moving parts) requirements for space flights. QuickSee Nano will help highlight the hyperopic shift and its time course under static and varying microgravity conditions, such as long-duration spaceflight or stationing at a Martian/lunar outpost—data that has not been previously obtained.

Contributions

• Led the mechanical design and prototyping of the next-generation lightweight autorefractor (QuickSee Nano) under a NASA research grant to study eye accommodation in a microgravity environment.

• Implemented Design for Manufacturing (DFM) principles and streamlined the assembly process of QuickSee Nano for batch production for clinical trials.

• Enhanced the patient experience by redesigning the components of the flagship product (QuickSee) to be 17% lighter.

• Designed and prototyped a motorized tunable lens system for rapid astigmatism correction.

• Supervised the manufacturing process in India to implement design changes and regulatory requirements.

• Improved the quality assurance process and created guidelines for troubleshooting mechanical failures.

When I joined PlenOptika in 2018, the initial production run had already been completed, and beta testing was in progress among optometrists in the United States. I was responsible for designing the portable hard case, charging dock, and optical equipment calibration jigs while also conducting product inspections and repairs to identify mechanical issues arising from the initial production run. The main issues included:

• The center of gravity was positioned too far forward, making it difficult for the elderly or children to bring the device close to their faces.

• The excessive use of fasteners in assembly frequently led to loose screws during movement due to vibration.

• The USB charging port was hidden, making connections difficult. This often resulted in excessive force being applied, causing disconnections from the PCB board.

To address these issues, we began new product development using research funds from TRISH (Translational Research Institute for Space Health), an affiliate of NASA. NASA is studying the effects of long-duration space travel on the human body, with the goal of manned exploration. In the case of the eyes, microgravity causes bodily fluids to pool in the head and upper body, leading to a narrow field of vision and difficulty distinguishing colors. This phenomenon is termed Spaceflight-Associated Neuro-Ocular Syndrome (SANS) and is considered a serious issue that can significantly affect the ability of astronauts to perform complex tasks. TRISH provided funding necessary for developing a portable autorefractor that could be sent to the International Space Station (ISS) to measure the impact of SANS on astronauts’ vision. The new device had to meet the following conditions:

• It should be easy to use for astronauts with minimal training without the assistance of a professional optometrist.

• It should withstand the vibrations and accelerations of rocket launches without mechanical failure.

• It should be lightweight.

The requirements for space travel closely matched the improvements needed for the existing product. In particular, the cost of sending 1 kg of mass to low Earth orbit was over $15,000, necessitating significant weight reduction. Initially, we aimed to maintain the existing design while changing materials for weight reduction.

To achieve this, we set the following development goals:

• Remove the built-in screen and integrate with a smartphone for reading measurements and operating the device, targeting over 30% weight reduction.

• Design a monocular system using a single sensor, but modularize it to allow for binocular measurements when needed.

• Apply Design for Manufacturing (DFM) principles to facilitate production and assembly using molds (to be applicable for subsequent products).

The project was conducted from August 2019 to March 2020 and utilized in-house prototyping with 3D printers and CNC milling machines to achieve the final product. Ultimately, the weight was reduced from 1.42 kg to 1.02 kg for the binocular model (a 30% reduction) and down to 323 g for the monocular model (a 77% reduction), achieving the target of 30% weight reduction. Unfortunately, due to the onset of COVID-19 and strict lockdowns, clinical trials using the prototype could not be carried out.

After returning to Korea, I was unable to participate in the further development of the TRISH project. However, I can observe the legacy of my project in the newly released product, 'QuickSee Free,' launched in October 2023. Aimed for use on the ground rather than in space, it incorporated additional features such as a display and a handle for the convenience of optometrists rather than extreme weight reduction. Consequently, the form factor changed to accommodate battery storage in the handle, but the fundamental modular design based on monocular measurements remained.