A team of researchers from Khalifa University in Abu Dhabi have developed a new wearable assistive device that could help people with colour blindness.

Using dyes to develop lenses for glasses to help correct colour blindness is not new, the university stresses, but the research team has developed a method using 3D printing to manufacture customised glasses.

A transparent resin is used to make the device’s lenses, mixed with two wavelength-filtering dyes to provide a tinting effect. The researchers used three different concentrations of the dyes to customise the lenses. They compared their 3D-printed glasses to commercially available products used to treat colour vision deficiency (CVD).

Dr. Haider Butt, Associate Professor of Mechanical Engineering, said: “Patient-specific customisation of glasses for CVD remains a challenge, even though research has significantly advanced the properties and materials of CVD wearables available on the market.”

Problems with distinguishing between shades of certain colours restrict people from working in fields where colour recognition is critical but can also have everyday ramifications as simple as deciding whether a banana is ripe or selecting matching clothes, according to the researchers.

The retina has three types of cones: One perceives blue light, another green, and the third red. These cones work together to allow people to see the whole spectrum of colours, but CVD is an inherited ocular disorder that limits this ability.

Red-green colour blindness is the most prevalent form of CVD, with most sufferers relying on wearables to manage the difficulties in day-to-day tasks. The most common wearable is a form of tinted glass.

Deuteranomaly, which occurs mostly in men, is a condition in which the photoreceptor responsible for detecting green light responds to light associated with red, the research team explains. This can be improved using red-tinted glasses, which make the colours more prominent.

Certain dyes can absorb and filter out some of the wavelengths between green and red that confuse the photoreceptors. With less colour overlap, the brain gets a clearer signal to help distinguish between the problem colours. This concept can also be extended to other forms of CVD.

The Khalifa University team used two dyes: One blocked the undesired wavelengths for red-green patients, while the other filtered unwanted wavelengths for yellow-blue patients. The team used both dyes in their lenses, and, when tested, volunteers with red-green CVD and yellow-blue CVD both benefited from the glasses, suggesting their efficacy in managing both CVD types.

Glasses based on this approach are commercially and readily available, but the University claims that users find the devices ‘bulky’ and can be uncomfortable. The KU research team developed its own frames for their lenses, using 3D printing to optimise the frames for comfort and usability. Inspired by commercially available designs, the assistive glasses can fold like other glasses, making them more usable to the wearer.

Research on CVD management techniques has shown that using dyes can be difficult as leaching and toxicity problems can occur. However, the research team tested this to ensure the glasses were safe for long-term use.

The stability of the dyes within the 3D printed glasses was examined by storing the glasses in water over a week. Results revealed that no dye leaked into the water, indicating their stability. They also left the glasses open at ambient conditions for a further week, proving their stability and long-lasting properties.

The devices’ mechanical properties were also carefully assessed. Flexibility and tensile strength are crucial components in quantifying their longevity and durability, and, when tested, the glasses exhibited excellent durability, without breaking even when subjected to folding or bending.

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