One of the most exciting aspects of the Tonkinese breed are the different eye colours that define the breed. The eye colour is determined not by the colour of the cat, but by the 'pattern' that dictates how the colour is expressed on the body of the cat. As there are 3 different patterns associated with each colour, ie; Point, Mink & Solid, there are thus 3 different eye colours that are specific to each pattern.

Therefore it's the second part of the colour and pattern description that determines eye colour - ie; Seal-Mink, Lilac-Point or say a Chocolate-Solid.

The eye-colour most usually associated with the breed is Aquamarine, or Aqua, essentially a blue/green and is the result of Mink-Pattern expression. The Mink pattern was the defining pattern of the breed originally, until quite recently many registries did not accept the Point and Solid patterns, and thus aquamarine eyes were also the defining eye-colour of the breed itself. 

The expression of 'Aqua' is due to the blending of eye-colours of the Burmese and Siamese that occurs - much like the blending of coat patterns that happens when a Point-patterned cat is bred with a Solid-patterned cat.

But that's not where the story ends, the eye colour of a 'Pointed' or 'Solid' Tonkinese is specific to the coat pattern displayed and results in 3 distinctive eye colours.

The 3 Eye Colours associated with the Tonkinese

I like to compare the Tonkinese eye-colours to gemstones, in order to describe the 3 different eye-colours that define the Tonkinese breed. In breeding Tonkinese and selecting for eye colour, it is my intention to aim for similar eye-colours to those seen here in the gemstones depicted.

There are many factors that influence the expression of eye-colour and the genetics that give rise to eye-colour and pattern are complex and multi-faceted. Just like the gemstones there is significant variation in the expression of colour, tone and intensity seen in the eyes of the Tonkinese.

• The Green-eyed 'Solid' The eye-colour expressed with the solid patterned cats is a yellow-green or frequently described as 'chartreuse' in tone.
  
  Compared to the eyes of the Burmese, whose expression of coat colour should be identical to that
  of a Solid Tonkinese, the eye colour is very different, the gold tone of the Burmese is expressed more as a green whne seen in the solid-patterned Tonkinese.

  The Aqua-eyed 'Mink' The eye-colour expressed
  with the intermediate pattern of Mink is an aqua colour, and therefore is a blend of the colours we would expect to see if we mixed the green eyes of
  the Solid and the blue eyes of the Point.
  
  The aqua colour eyes vary greatly in depth and intensity.

  The Blue-eyed 'Point' The eye-colour expressed with the Colourpoint pattern is a blue/violet and is reflective of Siamese eye colour whose coat pattern is shared.
  
  The tone of blue does seem to vary according to the coat colour - with the darker coat colours tending to produce stronger darker eye colour.
  The tone of blue will also vary somewhat from the Siamese expression which can be a stronger purer blue.

     

 'Pointed' Tonkinese Eye-Colour - a comparison of how coat colour affects eye colour

 

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The inheritance of Eye Colour
The inheritance of eye-colour is a complex process and good eye-colour does not always get passed on to the offspring of the parents - It is common to see a range of eye colour expression within a litter. Sometimes two parents with great eye colour will not replicate this is their offspring.

Here at Anniesong, some of the best eye colour and expression have derived from parents that have a more average expression of eye colour. The challenge therefore is to 'fix' good eye colour in the collective gene pool. 

The images below depict the resulting eye colour & shape that Sienna has produced in her offspring from matings to 3 different studs. The images all depict adult expression of eye shape and colour in 'Mink'-patterned cats, and therefore the eye colour for each is aqua.

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Fixing good eye-colour

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ne of the many challenges I've faced in terms of breeding Tonkinese has been establishing and then fixing strong eye colour, particularly in regard to the aqua colour that defines the 'mink' pattern. The inheritance of good eye colour is therefore not always predictable. How Aqua eyes appear in the 'Mink' - patterned Tonkinese is perhaps the most variable - or at least that is what I've experienced within the gene pools I'm working with.