Eye Colour Development in Cats
From newborn shades to Dominant Blue Eye and Odd-Eyed expression.
All kittens are born with blue eyes.
Every kitten starts life with blue eyes. This is not rare, not a sign of DBE, not proof of anything. The iris has no pigment at birth, so light passes through and the eyes look blue.
True colour only appears later.
Around 3–6 weeks pigment starts to form, and by 3–4 months the final colour is set.
True colour only appears later. Around 3–6 weeks pigment starts to form, and by 3–4 months the final colour is set.
Cats have a reflective layer in the eye called the tapetum lucidum. It’s what makes their eyes glow at night. In newborn kittens it is not ready. Studies show it develops gradually over the first four months of life [Wolff 1976, Bergmanson 1980]. While it’s immature, reflections are unstable and meaningless. Even in adult cats with genetically confirmed blue eyes, red reflex can vary between the same individual’s eyes or change with lighting conditions, proving it depends on physical factors like light angle and tapetal structure, not eye colour genetics. The so-called “red reflex” simply shows the state of tapetum development, not the future eye colour.
The critical period for vision.
The first 1–8 weeks of life are the most sensitive for a kitten’s vision. Research by Hubel, Wiesel and many others shows that this is the “critical period” – the brain is wiring itself for sight. At 4–5 weeks the vulnerability is at its peak [Daw 1992]. Disruptions in this stage – abnormal light, flashing light, too much light – can cause permanent damage to the visual cortex [Cynader & Chernenko 1982; Freeman & Olson 1982; Hirsch & Spinelli 1971]. Even a few hours of wrong visual exposure in this window have been shown to cause measurable brain damage.
On top of this, kittens’ eyes are physically immature. Pupils cannot constrict properly for 2–3 days after opening [Freeman & Tsumoto 1983]. The optical quality is poor [Bonds & Freeman 1978]. Young kittens even avoid bright light naturally, because their eyes cannot yet handle it.
The “flash test” myth.
Some breeders claim flash can predict blue or odd eyes in new born kittens:
• One red eye = odd-eyed
• Two red eyes = blue
• Two blue eyes = “double DBE”
This is false. The red reflex is nothing but light bouncing off blood vessels at the back of the eye. Humans get it too. It depends on camera angle, flash strength, lighting. The same kitten can show one red eye in one photo, two in another, none in the next. If the same animal can show all possible “results,” the test is worthless.
Why flash is harmful?
Taking a flash photo of a 1-2-week-old kitten to confirm DBE means blasting its unprotected eye with intense light, during the very period when the visual system is most fragile. Professional photography guidelines confirm that flash can cause temporary blindness, and in young animals even permanent retinal damage. Doing this to newborns for marketing photos is not just pointless – it is potentially cruel.
DBE genetics don’t change this.
A cat can carry the DBE gene but show two blue eyes, one blue eye, or no blue eyes at all. Some breeders claim red reflex in kitten has “hidden” DBE even without blue eyes.
This makes no sense. Red reflex happens in all newborn kittens because their eye structure is not finished growing. It has nothing to do with whether they carry DBE genes or not. A kitten with red reflex might end up with 0, 1, or 2 blue eyes. The flash tells you nothing about which it will be.
Why this practice is pseudoscience?
The biology is clear:
• All kittens are born blue-eyed.
• Eye colour only settles months later.
• Tapetum develops for 4 months.
• Red reflex depends on tapetum maturity and light, not genetics.
• The first 1–8 weeks are the most vulnerable period for vision.
• Flash can harm.
Using flash as a “diagnostic tool” in newborn kittens is pseudoscience. It ignores decades of research in neurology and ophthalmology. It puts kittens at risk. And it misleads buyers with fake “evidence”. The only valid way to identify DBE is genetic testing and waiting for eye colour to fully develop.
Daw N.W., Fox K., Sato H., Czepita D. Critical Period for monocular deprivation in the cat visual cortex. J Neurophysiol. 1992;67(1):197–202.
Cynader M., Chernenko G. Experimental evidence that rearing kittens in stroboscopic light retards maturation of the visual cortex. Dev Brain Res. 1982;4(4):451-456.
Freeman R.D., Olson C.R. Brief periods of monocular deprivation in kittens. J Neurophysiol. 1982;48(1):1-12.
Hirsch H.V., Spinelli D.N. The effects of early visual experience on the cat’s visual cortex. J Physiol. 1971;312:673-716.
Buisseret P., Gary-Bobo E., Imbert M. Plasticity in the kitten’s visual cortex. Brain Res. 1982;256(4):417-426.
Wolff H.H. The development of the rods in the tapetal cells of the cat. Histochemie. 1976;47(1):1-16.
Bergmanson J.P., Townsend W.D. The morphology of the cat tapetum lucidum. Am J Optom Physiol Opt. 1980;57(3):138-44.
Coles J.A. Some reflective properties of the tapetum lucidum of the cat’s eye. J Physiol. 1971;212(2):393-409.
Bonds A.B., Freeman R.D. Development of optical quality in the kitten eye. Vision Res. 1978;18(4):391-398.
Freeman R.D., Tsumoto T. Eye alignment in kittens. J Neurophysiol. 1983;49(4):917-928.
Ollivier F.J., Samuelson D.A., Brooks D.E., Lewis P.A., Kallberg M.E., Komaromy A.M. Comparative morphology of the tapetum lucidum. Vet Ophthalmol. 2004;7(1):11-22.
The Cat Care Clinic Veterinary Services. Feline Eyes and Vision.
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