There are several reasons for your eyes becoming smaller than usual. First of all, it may because that you cried the night before, so that the overabundance of water as well as the salinity in the tears will lead to the angioneurotic edema in the eyes, which means that the blood vessels and nerves in the eyes get edema. If in this kind of case, you can just use ice bag to do cold compress on the eyes, and after a while, the eyes will recover gradually. Secondly, it can be drinking too much alcohol that leads to the eyes becoming smaller than usual. It can be alcohol interaction or alcohol allergy. If in this case, you can take some cetirizine and vitamin C to reduce the edema in the eyes, and pay attention not to eat allergic foods such as durian, nor should you eat spicy foods, and you should have light diet. However, in some cases it can be disorder of liver function, and you should go to the doctor's to have a examination. Inadequate sleep and rest can also lead to eye edema. Therefore, getting good and enough sleep and rest is very important.
Normally, there are two reasons can cause eyes smaller than usual. First, you maybe drank too much water last night, and next day your eyes will affect by edema. To solve this problem, you had better not drink water before sleep. Second, you sleep late or lack of rest. And this will cause series of problems, such as dark cycles, dried eyes, and puffy eyes. You can put cold towel or tea leaf on your eyes, this can remit your problem for temporarily.
You may not have the good sleep which makes you still sleepy. That is the reason why your eyes look smaller than usual. Thus, you'd better have the sound sleep. Or else, you will have no spirit during the daytime. You could also drink more milk before you go to sleep which will be helpful. You could also use some eye drops to moisture the eyes to make them become normal.
Well, generally speaking, your situation will not occur. So we can say that it is not normal. And in common, if you do not have an allergic reaction to your eyes, then your eyes are the same. So I have to say that your eyes may suffer from allergy in some degree. And that just make your eyes look smaller than normal. And for your situation, you can go and see the eye doctor, and he may give some eye exam. In that way, you can know what happens to your eyes.