Your eyes are incredibly complex and it is almost a certainty that each of your eyes are unique.

You may have seen spy movies or science-fiction programmes where the eye is scanned to access certain areas and, believe it or not, there is some truth to this idea. This blog article looks at how your eyes are as unique to you as your fingerprints.

Retinal Scanning

Jumping straight in with the undercover spy theme, retinal scanning is a process where a scanner looks at the back surface of your eye and identifies the layout of the blood vessels as they spread across the retina1. The arrangement of blood vessels is unique to that eye and formed as the eye developed. This configuration is usually constant throughout life making it one of the most secure methods of identification (approximately 20,000 times that of fingerprint identification2).

Iris Scanning

The coloured part of your eye, the iris, is also exclusive to each eye3. The colours are genetically influenced by your parents and how much pigment your iris holds4, leading to a wide range of colours. You may have blue, green or brown eyes, but each colour can be in many shades and combinations. This means colour combinations on the iris can reach into the thousands or even millions.

Not only does it vary in colour between individuals, the texture is also unique – having been formed as the eye developed as an embryo. The pattern of this texture is different for everyone and seeing this rich tapestry of ridges and crypts across the iris surface makes it easy to understand why the iris is considered the “fingerprint of the eye”.

It is the individuality of each iris that makes it another great tool for biometric security, with iris scanners also being used for identification purposes. However, as the iris is easily seen and can be imaged with a simple camera, it is less secure than retinal scanning and it is possible to fool some scanners with a high-resolution image of the required eye5.

A Multitude of Optical Prescriptions

There are many factors that can influence the power of glasses you need to see clearly. Genetics, eye length, eye shape and diseases can provide a variety of prescription combinations. Without going too much into optical prescriptions, each eye requires the main correction (the sphere), the astigmatic correction (the cylinder) and the direction the cylinder sits in the glasses (the axis)6.

With relatively low prescriptions, from 2 dioptres of hyperopia (long-sightedness) to 2 dioptres of myopia (short-sightedness) with up to 2 dioptres of cylinder creates up to 335 million glasses combinations between the eyes. Optometrists often see prescriptions of up to 10 dioptres and, keeping the cylindrical component the same, gives a massive 26.3 billion combinations! Keeping in mind that cylinders are often higher than 2 dioptres and some prescriptions are in excess of 20 dioptres, that leads to an almost infinite combination of lens powers that make up your pair of glasses! It is a good job that our optometrists can work out which combination your eyes need out of all those combinations!

It is for this reason why optometrists and dispensing opticians don’t recommend over-the-counter “ready-readers” as the powers rarely exactly match the prescription needed7 to give you your best possible vision. It is also the reason why things may be blurry if you look through somebody else’s glasses.


Pathology is the scientific term for disease, and like most parts of the body, the eye is also susceptible to disease. There are hundreds of different conditions that can affect the eyes and the severity of the disease can affect people in a variety of ways. Whether your eyes are healthy or are showing signs of pathology can also differentiate your eyes from other people.

Throughout life, the eyes are exposed to a wide range of dangers. The sun emitting ultraviolet light can lead to a quicker development of cataract and increase the risk of macular degeneration8,9. The team at Haine & Smith Opticians therefore recommend UV-blocking sunglasses to help prevent these changes occurring. Furthermore, flying debris from DIY projects or the hazards within your job can also pose a physical risk to the eyes. Our dispensing teams are trained and qualified in working out what eyewear is needed to best protect your eyes to ensure that they don’t lead to scars or eye loss!

Your Eyes are One of a Kind, So Why Not Your Eyewear?

As you can see, no two eyes are the same. We here at Haine & Smith Opticians think that this variety should be celebrated by offering your eyes eyewear that highlights this fact. We have a tremendous selection of frames and lenses across our twenty stores, with new frames arriving frequently. Visit us today and let us help you celebrate your eyes by updating your glasses today!


1. Hill RB (1996). “Retina Identification”. In Jain AK, Bolle R, and Pankanti S (eds), Biometrics: Personal Identification in Networked Society. Boston, MA: Springer, pp 123-141.

2. Lacohée H (2008). “Use of Biometric Data”. In Lacohée H, Cofta P, Phippen A, and Furnell S (eds), Understanding Public Perceptions: Trust and Engagement in ICT-Mediated Services. Chicago, Il: International Engineering Consortium, pp 143-170.

3. Daugman J, and Downing C (2001). Epigenetic randomness, complexity and singularity of human iris patterns. The Royal Society 268(1477): 1737-1741.

4. Boyd K (2017). Eye color: unique as a fingerprint. American Academy of Ophthalmology [Online]. Available at: [Accessed on: 16th January 2020].

5. Khandelwal S (2015). Hacker finds a simple way to fool iris biometric security systems. The Hacker News [Online]. Available at: [Accessed on: 16th January 2020].

6. Association of Optometrists. Your prescription explained. Association of Optometrists [Online]. Available at: [Accessed on: 16th January 2020].

7. College of Optometrists. Ready-made spectacles. College of Optometrists [Online]. Available at: [Accessed on: 16th January 2020].

8. Walsh K (2016). UV radiation and the eye. Johnson & Johnson Vision Care Institute. Available at: [Accessed: 21st December 2019].

9. Keirl A (2014). Essential course in dispensing – part 10. Optician Online. Available at: [Accessed: 21st December 2019].

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