The Iris of the Eye: A Masterpiece of Individuality

Anuska Chakraborty B. Optom Student

NSHM Knowledge Campus – Kolkata, India

 

At the beginning of our optometry journey, we all cherish the moment of achieving the first clear focus through the slit lamp, and our fascination peaks with the artistry of the Iris. It is only natural to be curious about the iris; after all, each iris is so uniquely patterned in every individual. Beautiful colours and well-crafted texture make one’s iris different from others. In this blog, we will explore the uniqueness and usefulness of the Iris Pattern.

Uniqueness in Iris Features

Complex morphological features make irises so unique that even identical twins have uncorrelated iris patterns (Figure 1). ⁽¹⁾

Figure 1: Iris Features; 1. Fuch’s crypt, 2. Contraction furrow, 3. Pigmented spot, 4. Wolfflin nodule, 5. Ciliary zone, 6. Collarette, 7. Pupillary zone

Fuch’s Crypts:

Most irises have substantial hypoplasia (absence of tissue) around the collarette, which can extend into the ciliary zone and form diamond-shaped lacunae, known as Fuch’s crypts.⁽¹⁾

• Contraction Furrows: Furrows are produced by the contraction and dilation of the pupil. They are wrinkles like depressions that lie around the outer periphery of the iris.⁽¹⁾
• Pigment Spots: These are small regions of hyperpigmentation in the anterior border layer of the iris. Several types of pigmented spots can present; the commonest are iris freckles and⁽¹⁾
• Wolfflin Nodules: The nodules are small bundles of collagen distributed along the outer border ciliary zone. Wolfflin nodules are highly associated with iris colour and are much more common in light-eyed individuals.⁽¹⁾
• Pigmented Ring: It is the accumulation of melanin around the pupil.

GWAS (Genome-Wide Association Studies) findings, ⁽²⁾ have shown that human iris patterns have some interesting connections with genes. Neurodevelopmental aspects of those features have been thoroughly studied, according to which, the Fuch’s Crypts with SEMA3A, the Contraction Furrows with TRAF3IP1, the Wolfflin Nodules with DSCR9 (and some other genes also) and the Pigmented Ring with SLC24A4 gene are found to be associated.

Usefulness of Iris Recognition

Using the iris features, Iris Recognition Technology (IRT) has been developed to create one of the most accurate biometric identification systems. This newly developed technology, IRT, is positioned to replace traditional user verification systems.

Companies like Iridian technologies (formerly IriScan) have developed automated IRT, enabling contactless & real-time identification. ⁽³⁾ The device by IriScan can scan the iris from 3.5” to 1 metre of distance. An optical unit captures multiple images of the iris, and the image that best meets the focus and clarity requirements of the system is then analysed. A dynamic feature of the system automatically adjusts to the width of the pupillary boundary-to-limbus zone to maximise the amount of iris analysed. The iris features are digitised into an IrisCode record, half of which describes the features and the other half controls the comparison process. The IrisCode is a binary pattern represented by a sequence of bits, where each bit corresponds to specific characteristics. For same-alike bits and for dissimilar bits, the system is assigning the value of zero and one, respectively. Finally, a mathematical comparison process is functioned for the final acceptance or rejection decision.

Conclusion

Iris recognition, with its unparalleled stability and resistance to fraud, is pivotal in ensuring highly secure and accurate identification. Its significance is evident in critical sectors such as national security, financial services, and infrastructure protection. The non-invasive and hygiene-friendly nature of iris scanning further underscores its importance, serving as a valuable tool for reliable and convenient identification processes across various domains.

 

References

1. Edwards M. The genetic architecture of iris colour and surface feature variation in populations of diverse ancestry. University of Toronto (Canada); 2016.
2. Larsson M, Duffy DL, Zhu G, Liu JZ, Macgregor S, McRae AF, Wright MJ, Sturm RA, Mackey DA, Montgomery GW, Martin NG. GWAS findings for human iris patterns: associations with variants in genes that influence normal neuronal pattern development. The American Journal of Human Genetics. 2011 Aug 12;89(2):334-43.
3. Williams GO. Iris recognition technology. In1996 30th Annual International Carnahan Conference on Security Technology 1996 Oct 2 (pp. 46-59). IEEE.