How does eye colour affect vision

It is important to clarify what we mean by “eye colour”. Eye colour refers to the pigment present in the iris, the coloured part of our eye, and is the result of genetic inheritance. While 79% of the world's population has brown eyes, which is the most common colour, other tones like blue, green, and hazel are also quite common. In addition to these usual eye colours, some people have rarer shade including grey, amber, or even violet. These extraordinary colours often arise from unique combinations of genetic factors, emphasising the intricate genetic diversity governing our eye colours.

Genetics of eye colour

Our eyes’ captivating and distinctive colour is not just a cosmetic feature but a result of complex genetic processes. Genetics, specifically the presence and distribution of pigments, namely melanin, in the iris, is what fundamentally determines our eye colour. The wide range of eye colours we see every day is due to genetic variations of two key genes, the OCA2 and HERC2. These genes control the amount and type of pigments produced in the iris. Different variations in these genes lead to different eye colours, ranging from the most common brown eyes to the striking blues and enchanting greens. The simplified theory governing inherited eye colour says that if you’ve inherited two “big Bs” (denoting the brown eye colour allele), your kids will invariably have brown eyes or “BB”. However, genetics rarely adheres strictly to simplicity. If you have brown eyes, you might also possess a genetic makeup of one dominant brown allele (B) and one recessive blue-eyed allele (b), leading to the genetic combination “Bb” and, consequently, a blend of brown and blue tones in your iris. This also means that two people with this “Bb” mix can have children with a “bb” genotype (representing two recessive blue alleles), resulting in their kids having lighter eye colours.

It's crucial to remember that changes in melanin levels in the iris can cause changes in eye colour throughout a person's lifespan, especially during infancy.

The Role of Eye Pigments

The presence and nature of pigments in the iris have a significant impact on the colour of our eyes. Melanin, the main pigment responsible for our eye colour, comes in two forms: eumelanin and pheomelanin. Eumelanin, which is prevalent if you have brown or black eyes, scatters and absorbs light less due to its dark colour. These darker eyes have a trait that makes them better suited to sunny, bright environments because they lessen glare and excessive light scattering, which enhances vision. In contrast, lighter eye colours like blue and green are predominantly influenced by pheomelanin, which allows more light to pass through the iris. As a result, if you have lighter eyes you may be more sensitive to bright light, frequently needing shades to shield yourself from direct sunshine.

Low Light Adaptation

When it comes to adjusting to low light, people with darker eye colours, such as brown or black, often have an advantage due to the higher concentration of melanin in their irises. In darker eyes, melanin functions as a naturally occurring pigment that effectively absorbs and disperses incoming light, minimising the effects of glare in low-light conditions. This allows people with darker eyes to see more clearly and comfortably in dim light, which reduces squinting and discomfort brought on by light. In contrast, those with lighter eye colours, such as blue or green, may be more sensitive in low-light conditions. Due to the lower concentration of melanin in lighter irises, people with lighter eyes may find it difficult to adjust quickly to low-light conditions, making it more difficult to distinguish details and manoeuvre through dimly lit environments. The intriguing relationship between heredity and vision is shown by this variation in low light adaption, which is a prime example of how eye colour can directly affect one's daily visual experiences.

Perception of Colour

Another intriguing way that eye colour might affect our vision is how we perceive colour. According to research, people with various eye colours may have slightly varied perceptions of colour. For instance, research has indicated that individuals with lighter eye colours, such as blue or green, may be more sensitive to subtle changes in colour tones. This heightened sensitivity might allow them to discern finer distinctions in shades, making them more attuned to variations in the colours of objects and scenes. On the other hand, people with darker eyes might see colours in well-lit environments with greater vibrancy and saturation. This is due to the increased melanin in their irises absorbing more light and lessening light dispersion. As a result, especially in strong, natural daylight, those with darker eyes may perceive colours as being more vivid. It's crucial to remember that the variations in colour perception are typically minor and might not significantly impact day-to-day life. Nevertheless, they reveal an intriguing insight into how our individual perceptions of the visual world can be shaped by our eye colours, emphasising the complex connection between heredity and our perception of colour.