So why would an ophthalmologist be interested in neuroimaging– the results of a CT scan or MRI of the brain? First, the brain and eye work together closely and are actually attached. Secondly, to make the discussion straightforward, to take away the fog surrounding scans- after all, eye doctors are good at bringing things into focus.
Patients with significant head trauma (after a motor vehicle accident, for example) will usually get a CT scan of the brain during the emergency room evaluation.
A CT scan is readily available in almost all emergency rooms (ERs), and is easy to perform.
MRI scans, which can provide more detailed clinical information, are often not available all hours of the day and require more patient cooperation. A CT scan can rapidly detect most significant abnormalities immediately after head trauma. Most of these findings involve some type of bleeding in the brain. Minor bleeding may only require observation. Immediate neurosurgical intervention is not usually necessary in mild or even moderate traumatic brain injury (TBI), but emergency surgery can be life saving, so ER doctors don’t want to miss big bleeds, and scans are usually ordered.
What does this have to do with the eye? Well, the eye is really an extension of the brain. The eyeball is often seen in CT scans of the brain. So radiologists get an automatic peak at the eyeball, bones around the eye, and optic nerve. Subtle abnormalities may be detected and more detailed scans and an eye exam may be necessary. Broken bones around the eye are often difficult to detect during a physical examination, but can show up on a scan.
If even small amounts of bleeding in the brain are discovered, this will almost always require admission to the hospital for observation. Even if these patients fully recover, any initial bleeding on a scan can be a red flag for chronic problems.
Much of the brain is involved in the processing of visual information, so scans are not only useful to neurosurgeons and neurologists but ophthalmologists as well.
Particular parts of the brain are of extreme importance to the eye doctor. The optic chiasm, which is right behind the eyeballs in the brain, is where the optic nerves cross and is a critical spot in neuroanatomy.
Damage to that small area can be devastating and produce visual field (or peripheral vision) loss. The eye doctor plays a critical role in assessing visual fields.
Also, damage to the occipital lobes in the back of the head are also critical. These lobes are at the back of the skull and are the primary vision processing centers of the brain and are particularly vulnerable to whiplash-type injuries.
Newer radiological imaging techniques are at the forefront of diagnosing chronic TBI in athletes, and these techniques are frequently being employed in TBI cases from falls and auto accidents.
Optical Coherence Tomography (OCT) is a routine imaging test employed by ophthalmologists in their offices and may become a standard non-invasive way to measure chronic TBI.
Neuroimaging can be very expensive and needs to be used prudently to control health care costs. Not every patient with mild head trauma needs a scan.
Ophthalmologists are gradually becoming part of the team associated with good care in TBI cases. I actually leave my office and often see head trauma victims in the hospital. Bedside eye exams are not as thorough as an office-based evaluation- instruments used to examine the eye are not always transportable. But waiting until a patient is discharged from the hospital is not always an option.
The ophthalmologist is part of the trauma team. Eye doctors, as myself, are quite comfortable ordering various CT or MRI scans of the brain. Future blogs may discuss cutting-edge scans valuable in measuring subtle findings of patients with chronic TBI- I hope this blog is useful in summarizing the basics of neuroimaging in a common sense manner.
