An optometrist is trained to recognise abnormalities in your eyes. They examine the internal and external structures of your eyes to detect causes of vision changes such as structural abnormalities. They can also detect papilledema which signifies an elevated pressure in your brain (like seen with IIH) diabetes and many other serious conditions.
An optometrist should be seen annually like you would a regular check up for your primary care doctor. By obtaining a full history and performing a complete eye exam, even a minor change can be appreciated by an eye specialist. Many optometrists are the first to diagnose IIH because peripheral vision loss or papilledema can be detected without you even noticing.