Retinal Detachment

An elderly patient presents with worsening vision in one eye over the last 2 days. There is no pain and there has been no trauma.

The patient’s visual acuity is significantly reduced in the affected eye and you question if there is an afferent pupillary defect.

Your differentials here include retinal detachment, so you decide to perform an ultrasound.

How to perform eye POCUS?

Do NOT perform ultrasound on the eye if there is suspicion of a penetrating globe injury

• Use the vascular probe (high frequency linear probe)
• Place a Tagaderm over the shut eye
• Use a lot of gel
  • This not only gives a better view, but also decreases the pressure applied on the eye.
• Use the probe to get a good view of the whole eye including the nerve.

What do we expect to see?

In Retinal Detachment, the hyper echoic line is uniform and doesn’t cross the optic nerve, whereas in vitreous detachment, it does and is usually less uniform due to inflammation and haemorrhage.

https://vimeo.com/514068967

Retinal Detachment vs Vitreous Detachment

A rapid history of the progression of the disease, any relevant past history, including diabetes, is important.

The clinical examination relies as always on the big 3:

1. Visual Acuity: It is helpful to know previous acuity also
2. Visual Field defects:
   1. For example, superior retinal detachment results in an inferior visual field defect. 
3. Pupillary Response including Relative Afferent Pupillary Defect(RAPD)

Note that direct ophthalmoscopy should also be performed, however you may not be able to detect the more peripheral retinal tears or detachments.

Posterior Vitreous Detachment

It occurs when the vitreous degenerates and separates from the retina. It tends to be age related.

Clinically the patient usually presents with:

• Normal Vision
• No visual field defect
• No RAPD
• May have ‘flashes’ that occur due to the vitreous pulling on the retina as it detaches

Retinal Detachment

This can occur following a retinal tear, which allows fluid from the vitreous to enter under the retina, separating it.

Clinically the patient usually presents with:

• Visual field loss
• May describe a curtain coming down over the eye
• RAPD
• Central loss of vision may indicate macular detachment(may not be reversible)

What is the relative afferent pupillary defect(RAFD)?

The RAPD is also called the Marcus-Gunn pupil. It indicates optic nerve or retinal disease. It also requires that the disease be only in one eye ie., bilateral disease may not produce a defect.

It should be performed in a dimly(not dark) lit room, with a strong light source. Swing the light from eye to eye. Shining the light on either pupil should make both pupils constrict. This is the direct and consensual response.

A positive RAPD is diagnosed when the pupil that has the light directed at it, does not constrict, but dilates.

What are the causes of RAPD?

• Optic Nerve Damage
  • Trauma
  • Ischaemia
  • Tumour
• Glaucoma
• Ischaemic disease of the retina
• Retinal detachment
• Severe unilateral macular degeneration
• Intra-ocular tumors
• Retinal infections

These are only some of the causes. Think of anything that causes optic nerve or retinal damage.

References

1. Lahham S, et al. Point-of-care ultrasonography in the diagnosis of retinal detachment, vitreous hemorrhage, and vitreous detachment in the emergency department. JAMA Netw Open. 2019;2(4):e192162.
2. Johnson D, Hollands H. Acute-onset floaters and flashes. CMAJ 2012;184:431.