TikZ or symbol eyes for difficulty of examples/exercises

It is very simple to do.

If you get the idea, you can create the other few you want.

The output

The code

\documentclass[12pt]{standalone}
\usepackage{tikz}
\newcommand\straightEye[1][1.2ex]
{%
\begin{tikzpicture}[scale=#1/1cm]
  \draw (0,0) circle (.5);
  \fill (0,0) circle (.25);
\end{tikzpicture}%
}
\newcommand\downwardsEye[1][1.2ex]
{%
\begin{tikzpicture}[scale=#1/1cm]
  \draw (0,0) circle (.5);
  \fill (0,-.25) circle (.25);
\end{tikzpicture}%
}
\newcommand\rightEye[1][1.2ex]
{%
\begin{tikzpicture}[scale=#1/1cm]
  \draw (0,0) circle (.5);
  \fill (.25,0) circle (.25);
\end{tikzpicture}%
}
\begin{document}
\straightEye \downwardsEye \ look at me \rightEye\rightEye
\end{document}

Or like this :

The output

The code

\documentclass[12pt]{standalone}
\usepackage{tikz}
\newcommand\sideEye[2][1.2ex]
{%
\begin{tikzpicture}[scale=#1/1cm]
  \draw (0,0) circle (.5);
  \fill (#2:.25) circle (.25);
\end{tikzpicture}%
}
\begin{document}
\foreach \ang in {0,30,...,360} {\sideEye{\ang}}
\end{document}

I like the answer of marsupilam. For the completeness sake: my idea of reducing the number of images embedded into the pdf file would be to embedd it only once.

Basically save each kind of eyes using a box, then just use these boxes. My current understanding is that the images would be embedded only once and then referenced again and again in the output file.

Update: I was just told than standard boxes don't work like this, but xsavebox does the trick. Thanks to AlexG.