[ eyes like a Hawk]

Crystalgem dragons have keen and sharp eyesight. They see in color like humans do but their eyes can pick up more details when focus, they can see great distance when their eyes are focused, this helps them when flying.

They also able to hold a Stare a long time without blinking
[ I can see the light~]

Gemehstedy is a very bright world with all its shiny Reflected surfaces, To help with the brightness of their world the Crystalgem pupils can adjust to lighting, their pupils gets smaller if there to much light so they can see better without getting so blinded.

The other thing that helps is if you notice all Crystalgem dragons have light patch with dark outlines around their eyes, these markings help reflect and absorb lights, drawing the light to the markings instead of the eye itself much like the markings of Cheetah
( Athletes put black markings on their cheeks for the same reason) this helps protect the eyes from bright lights.
Having both Adjustable pupils and Cheetah like markings let the Crystalgem dragons have really good eyesight when its bright.

-

[ hello darkness my old friend~]

Crystalgem dragons do dig and burrow, they do this for many reasons, looking for Mineral deposits and earth magic, nesting, some even live underground. There a species of the Earth but in the depth of the earth it can be very dark, the Crystalgem pupils can also widened to absorb more light making it easier to see in dark places.
But keep in mind that their eyes only let them be able to see in the dark so much, if there no light for their eyes to absorb then they can not see.

Usually the Crystalgem dragons will make their gemstones glow to make light in dark place so they can see.

[ were your safety glasses]

A fun fact is the Crystalgem dragons don't cry, it's not that they can't show emotions because they can and do, its just how they eyes are.

Instead of having tear ducts like Mammals do the Crystalgem eyes have a thin membrane layer that covers their eyes much like snakes have.
Crystalgem dragons do produce tears their tear ducts are between the eyes itself and the thin layer of membrane but this thin layer is attached to the skin and is why there tears never overflows, the excess moisture follows the thin layer into nasolacrimal ducts that drain the fluid into spaces in the roof of the mouth, this helps keep Special glands on the roof of their mouth that lets them taste magic moisturized but this is why Crystalgem dragons do not shed tears.
Fun fact: this is why Crimson is known as the 'dragon who crys' because he is able to shed tears like Mammals do, there are very few Crystalgem dragons who can shed tears and they all have the blue marks under their eyes, that is called 'Tearstains'

The thin layer over the Crystalgem dragons eyes also protects the eyes from dirt, dust, grit and wind burn, its like moist safety glasses.

This thin layer can get damaged but is replaced each time the Crystalgem dragons sheds its skin, it starts off getting cloudy kinda like when the dragon sick but it have a tent of color to it like their gemstones, as the shedding process continues it turns more and more into crystal as a new layer has been forming Underneath.

Even with all this eyes can be damaged both Naturally by birth defects or unnaturally by Injurys, Crystalgem dragons are at a level of Advancement were eye care is a thing, glasses and Lenses can be used to help a dragon see who wouldn't have normal eyesight otherwise.

[ Staring contest! ]

Because of the thin layer over the Crystalgem dragons eyes they don't blind very often.
They do have eyelids but the thin layer help keep the eye moist so they don't need to blink as often as a human.

-

[ your eyes tell a lot about you]

Even though Crystalgem don't cry that doesn't mean they're eyes don't show emotions, its actually the opposite, Crystalgem dragons tend to give away their feelings by the look in their eyes, happy their eyes sparkle a bit more and are brighter, their look more glossy and less bright if sad, or if their sick or mad, their eyes are very Expressive.

[ you wouldn't like me when I'm Angry ]

When a Crystalgem dragon get angry their pupils will get thinner ( but not Nightmare thin ) but its easy to tell if they upset or just to much light in their eyes, if upset their
magic Flares making their Iris gain a glowy texture to them, this menacing glow is Complimented by their sclera become darker (but not black ) given their glowy Irises an even more Intimidating, this is to let other know this is not one happy dragon.

-

[ you don't look so good]

When a Crystalgem gets sick their eyes will show it, depending on what it is and how Severe the infection is the Symptoms will be different. If its something Minor the thin layer over the eyes might dry some given the eyes a Cloudy look, if something a bit more Serious the Crystalgem Irises will dull and faded in color, if its something really serious the sclera will be darker and bloodshot and all Previous mention Side effects on top of this.

[ a powerful glare ]

When Crystalgem use their element magic their eyes will Radiate and energy the same color as their gemstones, their pupils will be the brightest spot.

-

[ cat eyes]

Female Will usually have darker markings around the edges of their eyes that give them a eyeliner look and some female even have the 'cat eye' look ( makeup term ) around their eyes that males do not have

That all!

I forgot the Numbers!

(1) is Natural
(2) is wide pupil (in dark places)

(3) is slit pupil (glowy when Angry )

(4) sick or just about to shed skin

(5) using magic (color depends on gemstones)

(6) halfway through shedding process
(7) almost at the end of shedding their skin.
Then Male and female eye differences