The Eye - Challenge Activity suitable for higher achievers - metacognitive deep thinking

This is a very effective activity for higher achievers that need to stretch their thinking.
The questions develop higher order thinking skills and has a metacognitive facet that works best when, while walking the floor, you ask students to identify the skill that they are using.
The resource is made up of a key word and definition match, deep thinking questions, labeling activity and prioritising (diamond 9 style) activity.
How to run the activity:

After teacher input, either reading text or teacher explaining. Students complete question 1.
It is very important that, at this point, the work is corrected so that any misconceptions can be cleared up
Using only information in question 1 and their recall skills they attempt to complete the rests of the worksheet – this is best done in pairs.
The plenary should consist of questions such as:
What part of the activity did you find the hardest?
why was it difficult?
how did you overcome the difficulty?