I'm writing a story about the supernatural, except with as few "explained by magic" elements as possible. In the case of vampires, I want them to look as similar to humans as possible while being able to see at night as well as we can in the day. This rules out slit or hyperenlarged pupils. A taptum lucidum would be cool but it blurs vision. I read that maybe quickening the protein reaction in cones would work, but it wasn't explained whether that would negatively affect vision clarity. Also, I thought it would be interesting to change the cone frequencies so vampires can see red light more intensely, and also UV light. I believe uv vision in vampires would be beneifcial in warning them of the approaching dawn before its too late. If this means sacrificing some color vision between the two spectrum extremes I am perfectly alright with that. But that then raises the question of how the uv light will pass through the cornea and lens.
The human eye is very optimized to do what it does and that is detect various levels of light that you might find throughout the daytime; essentially dusk till dawn (pun intended). The frequencies that are eyes detect (visible spectra of colours) are not random either and are very in tune with sensing relevant information about the world which aids in survival. Likewise the light levels the eye can detect are very optimized for conducting business over the same period of the day.
Starting with the frequencies:
The reason that our eyes cannot see ultraviolet light very well is because these frequencies and are energetic enough to damage our eyes. So the eye contains an internal lens which filters these frequencies out; there are people who are born without these filters or lose them due to surgery report higher sensitivity to short wavelengths including the ability to see light ultraviolet sources, however, these people are at a higher risk of losing their eyesight due to cataracts. For vampires, I'm guessing they would want to avoid sunlight so it might be beneficial to be more sensitive to ultraviolet light, but I wouldn't see why this would necessitate an external change in appearance of the eye.
Infrared detection is a bit of a different case. Infrared wavelengths interestingly enough tend to be absorbed by materials to which visible light is transparent. For instance, Water and Glass allow visible light through, whereas these materials tend to strongly absorb infrared wavelengths. This of course is a general trend and differs on the exact composition of the material in question, but it is important because the eye is filled with water-based fluids which absorb most near-infrared wavelengths of light.
Some animals, like some snakes, can sense mid-Infra wavelengths to detect sources of heat, but these organs do not even remotely resemble an eye and are very short range (within a few meters). There are many reasons for this, part of this is because short wavelengths require extremely small apertures to focus the light, severely restricting the anatomy of the organ, and also because there are much better ways to see (eyes for example).
So while detecting near-ultraviolet may be a useful fairly practical thing for your vampires, without too much of a visual give-away, I do not see much use nor feasibility in detecting near infra-red.
Now to the question of seeing in low-light environments:
This is difficult because the only ways to enhance the ability to see in low-light environments is to either increase the amount of light allowed into eye (larger pupils) or to increase the light reflected within the eyes (taptum lucidum). Both these method will require visual changes to the eyes.
Increasing the concentration of rods over time to adapt to low level environments, would likely work without resulting in a significant change to the visual appearance of eye, but would still be far short of true night vision. Of course this would likely also affect colour vision and possibly visual acuity to some degree.