Bilateral posterior dislocation of the crystalline lens after a head injury sustained during a seizure

Abstract

This article presents a case of bilateral posterior dislocations of the crystalline lens in a patient with epilepsy who presented with reduced vision and anisocoria 2 weeks after having sustained head injuries during a seizure. The possibility of lens dislocation was raised only at this time, and subsequently confirmed on computed tomography. Such patients may require prompt referral to the ophthalmologist to treat complications such as functional aphakia, uveitis and more seriously pupillary block glaucoma. This case highlights the importance of ocular examination of head injuries to rule out possible ophthalmological pathology.

A 51‐ year‐old man presented to the emergency eye clinic, complaining of reduction in vision and glare after a tonic–clonic seizure 2 weeks previously. He had sustained a head injury during the event and had been admitted to hospital for observation. He was known to have epilepsy and was taking epilepsy drugs. He had no ocular history. There was no known history and he had no clinical features of Marfan syndrome, homocystinuria, Ehlers–Danlos syndrome or pseudoexfoliation. The seizure was unwitnessed and he had no exact recollection of the mechanism of injury.

On examination, there were extensive periorbital ecchymoses, with numerous superficial lacerations to the face. Septal deviation and a small septal haematoma were noted on the right. Radiograph of the skull, including occipitomental views, performed on admission failed to disclose any bone deformity.

The best corrected visual acuity was recorded as 6/36 on the right and hand movements in the left eye. Both pupils were dilated (the left greater than the right) and sluggish to react to light or accommodation. No relative afferent pupillary defect was found and ocular motility was normal. Slit‐lamp examination showed bilateral iridodonesis and the presence of vitreous in the anterior chamber of both eyes. The intraocular pressures were normal (14 mm Hg in the right and 16 mm Hg in the left eye). Fundal views were difficult because of vitreous haemorrhages, but ultrasonographic examination showed no retinal detachment. Further neurological examination was unremarkable.

To further investigate the decline in vision and anisocoria, an urgent computed tomography scan of the head and orbits was requested. This showed bilateral posterior dislocated lenses, with no other intracranial or intraorbital abnormality (fig 1).

Figure 1 Axial computed tomography scan showing bilateral dislocated lenses (arrows).

Blunt trauma during the seizure may have led to disruption of zonular fibres, causing bilateral lens dislocations. Once the blood in the vitreous cavity cleared, his vision improved to 6/18 in each eye with aphakic glasses. He was referred to the vitreoretinal surgeons and found to have bilateral superior operculated retinal tears, but no retinal detachment. The tears were treated with laser. His dislocated lenses were floating freely in the vitreous cavities and causing no complications other than the refractive consequence of aphakia. It was planned to continue with aphakic glasses.

Trauma is the leading cause of dislocation or subluxation of the crystalline lens.¹ Blunt trauma in an anteroposterior direction is believed to lead to equatorial expansion, which may disrupt the zonules and lead to lens dislocation or subluxation.² Patients may present with symptoms such as a red eye, pain, glare, reduced vision or diplopia. Systemic associations include Marfan syndrome, homocystinuria, Weill–Marchesani or Ehlers–Danlos syndromes. Patients with these conditions may be at increased risk of lens dislocation or subluxation even with minor ocular trauma.

Lens dislocation is a rare complication of head injuries. It may, however, lead to serious complications such as pupillary block glaucoma. Prompt referral to the ophthalmologist is therefore imperative. Cases of bilateral lens dislocations after blunt injuries including airbag deployment have been previously documented.³ Incidental finding of a dislocated lens on magnetic resonance imaging in a 66‐year‐old patient with epilepsy has also been reported.⁴ However, to our knowledge, this is the first case of bilateral lens dislocations after a history of a tonic–clonic seizure leading to serious head injury. It highlights the importance of a thorough ophthalmic examination in such patients and the value of further imaging as an adjunct to diagnosis making.