Visual accommodation, fatigue, drugs of ocular application and influence in driving

Visual accommodation

In daylight conditions and in a relaxed state, the crystalline lens is focused on infinity. In dim light conditions, the relaxed position of the crystalline lens is at a focal point of about two meters, which is known as nocturnal presbyopia.

If while driving we shift our gaze tot the dashboard to check one of the instruments, the change in focus from far to near and back to far will take us about 3 seconds, which means that if we are driving at 100 km/hour, we will have traveled 78 meters.

In this regard, speed limiters and acoustic alarms are useful so that we don’t have to constantly glance down at the speedometer to confirm that we are not exceeding the permitted speed limits.

Visual fatigue

Prolonged use of the computer, increasing frequent in the workplace and during leisure time, forces the eye to focus at a short distance, and will cause a large increase in the number of nearsighted persons.

In fact, it is estimated that a third of young persons will be nearsighted within 15 years as a result of excessive use of the computer.

Another problem brought by excessive use of computers is the visual fatigue syndrome, which is suffered by nearly 85% of users.

The main symptoms are reduced blinking, dry or burning eyes, sensitivity to light, and blurred vision.

It is very similar to visual fatigue from driving because the gaze is fixed on a point in front of us, without the possibility of reducing the width of the palpebral fissure as is done when reading with a downward gaze.

When our gaze is fixed in front of us, the eye is opened very wide and the exposed surface is large, and when our attention is fixed, we blink less and our eyes become dry.

Driving at the end of the workday after many hours at the computer, added to the tiredness from work and the day’s responsibilities, makes the driver more vulnerable to the unexpected on the road home, with the risk of suffering an accident en route.

If the driver also suffers from refractive defects, particularly astigmatism, phorias or chronic eye dryness, visual fatigue will be very marked and will cause somnolence.

The symptoms become more pronounced depending on the length of driving time, the use of contact lenses that dry out and become damaged, air conditioning, tobacco smoke, as well as during night driving and in heavy traffic.

Tips

While driving we must try not to look for data in the dashboard, unless essential, because the far-near-far accommodation process makes that we do not control vision for a long distance, in addition to the added distraction occurring.
Physicians at workplaces should recommend to blink for reducing eye dryness, not smoking, low use of air conditioning, avoiding air currents, and sometimes indicate the use of artificial tears in patients at risk.
These measures are applied also during driving, resting the eyes several times a day.
It should be highlighted that there are multiple drugs that induce lachrymal hyposecretion, increasing the existing ocular dryness and its symptoms. Physicians should warn the patients about this.
It is the case of beta-blockers in patients with hypertension or heart disease and in the treatment of glaucoma, oral isotretinoin for the treatment of acne, tricyclic antidepressants, phenothiazines, and anxiolytics in psychiatric diseases and diuretics in the treatment of hypertension.

Drugs of ocular application and recommendations

The instillation of any ophthalmic solution can cause transient blurred vision.
It is the case of eye-drops and non-steroidal antiinflammatory ointments and corticoids combined with antiinfectious agents. Accordingly, it is recommended not to drive until vision is clear.
Sympathicomimetics (brimonidine) in the treatment of glaucoma can cause fatigue and/or somnolence.
Carbonic anhydrase inhibitors (brinzolamide, dorzolamide) cause transient blurred vision and can cause dizziness and visual disturbances that can affect the ability to drive.
Patients with seasonal allergic conjunctivitis are likely to experience lacrimation and eye itching that can affect vision.
It is unlikely that the light occasional irritation that can be experienced after the application of antiallergic eye drops such as azelastine, lodoxamide, levocabastine, emedastine, affects vision more substantially. These eye drops do not cause sedation, nor interfere with psychomotor activity.
Povidone-based ophthalmologic agents can cause blurred vision and it is recommended not to drive.