Eye movement and facial nerve disorders, and their influence on driving
Paralysis of the III cranial pair
The causes are very varied including CNS diseases, mechanical diseases, myopathies, and axonal diseases.
Weakness or complete paralysis of the common ocular motor nerve occur as palpebral ptosis and external lateral deviation of the eye.
If the parasympathetic fibers have lost their functional capacity, the pupil movement is affected, with non-reactive mydriasis.
If ptosis does not affect the pupillary area, it will not affect vision or the visual field, and the driver should adopt compensating positions such as hyperextension of the head and raising the eyebrows.
A ptosis of 4 mm or more is considered serious.
Paralyses of cranial pairs IV and VI
The weakness of the upper oblique muscle for affectation of the IV cranial pair causes diplopia that is compensated by the patient bending the head to the side contralateral to the paralyzed muscle.
Weakness of the external ocular motor nerve or VI cranial pair causes internal strabismus of the paralyzed eye.
Abnormal conjugated eye movements
Eye coordination in the gaze requires a perfect adjustment of the slow and fast eye movements, of reflex, automatic and voluntary eye movements, and in the direction by the extraocular muscles.
All neurological disorders affecting the CNS, paths or nerves can lead to abnormalities in the gaze conjugated with presence of nystagmus, strabismus, diplopia, paralysis of gaze, etc.
Advice on paralysis of the III cranial pair, paralysis of cranial pairs IV and VI and disorders of conjugated eye movements
- Pupillary areflexia that hinder the visual capacity established by the law leads not to driving.
- The patient with diplopia must not drive.
- The patient who suppresses the image of one of the eyes to prevent diplopia should be considered a monocular driver in legal terms, provided the condition is stabilized and with a minimum period of adaptation of 6 months.
- The appearance of a disease in the ocular motility leads to highly diverse adaptation mechanisms depending on the age of the patient and the time from the onset of the problem to the medical assessment.
- Adults who have been able to adapt develop an activity very similar to with normal binocular vision. At the moment, medical assessment and judgment are not easy.
- It must be highlighted that these compensated patients appear to be normal, in periods of stress, tiredness, night driving, with some drugs or large meals, can be decompensated and it would be advisable that the physician notified these drivers of their limitations in these situations.
- The physicians should inform driver patients of this risk. These advices are compulsory in the companies for all professional drivers, and the control of these workers should be very strict.
- Eye movement can be affected by some drugs, including: chlordiazepoxide, nalidixic acid, diazepam, sulfonamides, piperazine, quinine, tetracycline, phenytoin and vitamin A. In these cases, the patient should be warned of the possible risk while driving.
- Many symptoms can be masked, so it is recommended to devote time to our patient and give him confidence when binocular vision disturbances are suspected.
- We should convey him our interest in protecting him and his relatives when driving, and explain in each case their problem, to reduce it and that he can drive without risks.
- With diplopia or nystagmus, if the visual capacity levels legally defined for each group are not reached, the patient cannot drive.
- The surgical correction of ptosis invalidates the current limitations until that moment in the driving license.
- Health professionals should play an essential role in the prevention of the rate of accidents of the traffic in people with visual disturbances.
- In the populations at risk we should advise frequent ophthalmologic examinations that allow for diagnosing the visual disease in the beginning and act accordingly.
- In the cases of anxiety, stress, night driving, or driving against the sun, physical or mental weariness, somnolence, large meals intake of alcohol and therapy with some drugs, visual fatigue increases, while the capacity of adaptation of the optically compensated patients is reduced.
- The physicians should know how to explain to the driver the list of these circumstances with their visual problem, and remind him not to drink alcohol.
- The physician should be attentive to the possible masking and simulation by the patient during the examination, making him understand that a wrong assessment can involve an avoidable worsening that can have impact for his health.
Facial nerve disorders
Unilateral peripheral facial paralysis of sudden onset and unknown cause, called Bell’s paralysis, can be preceded by retroauricular pain during some hours.
The patient is frightened by the sprained deformity of half the face to the healthy side.
In serious cases the palpebral fissure is wide and the eye cannot be closed. It can be associated with very troublesome hyperacusis.
Frequently, the temporal occlusion is required in the affected exposed eye. Most patients with Bell facial paralysis usually recover in a period ranging between some days and two months.
Lagophthalmos involves the secondary risk of promoting keratopathy by exposure, associated with corneal ulcers that can leave scars that affect visual acuity.
If weakness for the closing the eye, tarsorrhaphy may be required. In cases of permanent facial paralysis or sequels neurosurgical treatment may be required.
Advice on facial nerve disorders
- The patient with unilateral peripheral facial paralysis should rest the first days that are associated with significant anxiety and worry, and should not drive.
- He cannot be led when the palpebral cleft is broad and the eye cannot be closed.
- The temporal occlusion of the affected eye is disabling for driving.
- When the clinical condition subsides completely, the patient can drive again without restrictions.
- The driver with persistent lagophthalmos can ask the ophthalmologist about its influence on the visual capacity, and with the issued report request the driving license.
- The surgical correction of the lagophthalmos invalidates the current limitations until that moment in the driving license.