Sometimes I wondered if I was seeing the same things through my eyes that the rest of the world was seeing through theirs.

1. through 是介词，“通过；借助于；用”，这里跟with 用法相同。through my eyes = with my eyes，介词短语作方式状语。

2. that the rest of the world was seeing through theirs —— 这是 that 引导的定语从句，that 指代the same things，关系代词that 作从句seeing 的宾语。

又如：

This is the same watch that I lost. 这是我丢失的那块表。

（same 表示强调“一模一样”，有无same 意思相同）