Study finds drivers with dry eyes have more unsafe driving experiences and greater risk of accidents

Dry eye disease is becoming more common because of our lifestyles. We are increasingly able to diagnose dry eye diseases depending on the criteria we use to diagnose it.
Dry eye disease (DED) is believed to affect between 5 to more than 30% of the population, and it is a significant cause of visual disturbance. DED can degrade the quality of a person’s everyday life and impact on their health.
DED causes subtle damage to the external ocular surface and sufferers have symptoms of ocular discomfort together with an impaired quality of vision and reduced visual acuity.
People with DED get intermittent blurred vision, depending on the time of the day and ambient environmental factors such as lack of humidity, artificial lighting and central heating.
Many people around the world drive and, of course, your vision’s role in driving is crucial. DED is one of the most common diseases causing eye discomfort and affecting vision. People with DED often report vision related difficulties while performing everyday activities including driving, mainly if there is the air conditioning or heating on in the car.

Chinese study finds drivers with dry eye disease to be more dangerous drivers than those drivers with healthy eyes

I have just read a Chinese study on DED and driving from China. In this Chinese research, they looked at patients from the Peking University Third Hospital, between the ages of 20 to 50 years old who were healthy, were licensed drivers and drove at least once a week.
In group A, patients were diagnosed with dry eye disease for the first time who had not had any prior treatment.
In group, B were people treated with tear substitutes only without any anti-inflammatory or cyclosporin type medication and were stable.
Group C was comprised of the healthy subjects with no ocular pathology, treatment of symptoms and no signs of dry eye disease.
Only patients with best-corrected vision of 6/20 at least which is equivalent to 6/6 were included in the study.
DED had been diagnosed based on the association of ocular symptoms and tear film abnormalities on Schirmer’s test, the tear break-up test and with corneal or conjunctival staining according to the DEWS criteria. All of the patients using the Delphi approach had mild severity to moderate severity dry eye disease.
They used ocular surface disease index (OSDI) questionnaire to quantify the specific effect of dry eye disease on vision-targeted health-related quality of life. This disease-specific questionnaire has three divisions or subscales, the first of which is ‘ocular symptoms’ called OSDI symptoms.
The second division is vision-related activities of daily living which called OSDI function, and the third division is environmental triggers. Researchers calculated each subscale between 0 to 100 and arrived at an overall average score. The subjects completed the questionnaire scoring the answers as:

1. Always.
2. Mostly.
3. Sometimes.
4. Seldom.
5. Never.

They combined the OSDI function portion with a 25 item National Eye Institute vision function questionnaire to produce questions about daily life designed to evaluate the effect and impact of dry eye disease including activities such as reading, computer use, watching TV, walking, emotions, sleep and interpersonal relationships.
The dry eye related functional limitations were all drivers, evaluated by autognosis and the answer scored 1-5 as before. They used questionnaires about performance during driving to study the safety of drivers and drivers evaluated their own on-road driving performance by autognosis using the same method as the OSDI questionnaire. They identified dangerous activities that increase the risk of danger during driving such as increased blinking leading to missing signals on the road and traffic lights. Autognosis means self diagnosis.
Researchers found that

• about 40% of DED patients had dangerous driving experiences, and one driver had actually had an accident due to visual disturbance related to his dry eye disease
• the rate of accidents and near accidents was 10.33%
• the rate of missing targets including vehicles, pedestrians, traffic lights and signals was 31.71%
• the dry eye disease related symptoms during driving included soreness 66%, burning 15%, pain 16%, tearing 23%, grittiness 32% and blurred vision 32%
• dry eye disease patients have to use methods to relieve their symptoms whilst driving which included stopping and putting in the eyedrops in 26%, replacing the driver in 17%, wearing sunglasses in 36% and increasing in their blink frequency in 37%
• some of them had to take a comfort stop in 31%, and 8% did nothing
• they found that their driving experience was exaggerated by environmental triggers such as night time driving 48%, haze 40%, air-conditioning hot air 31%, air conditioning cold air 12%

The researchers studied the detailed daily life and driving habits of patients with DED. They compared them to a normal group, and they found that DED was correlated with unsafe driving habits and performance, which increased the risk of danger both to the driver and to the public. They, therefore, suggested that more attention focus on the effect of dry disease in driving performance.
The DED patients in group A who had not had treatment suffered more discomfort than the patients in group B who had artificial tears. Artificial tears are one of the most important treatments of DED because the complicated precorneal tear film plays an important role in clear vision i.e. in ocular and optical quality, as the tear film is the most important refractive surface of the eye sitting in contact with the cornea.
DED patients commonly complain of difficulties in performing daily activities which are vision-related. This has been well-documented using quality of life questionnaires. Researchers concluded that the effect of DED on driving should be emphasised and drivers should receive treatment such as eyedrops to relieve uncomfortable symptoms of dry eye disease. They recommended that using eyedrops or avoiding difficult driving conditions may be the safe best choice for drivers with DED.
Many of us have experienced dry, blurred vision when driving with air conditioning or heating on in the car for some time, but probably never realised that it really could adversely affect the safety of driving. I recommend that drivers keep eye lubricating drops in their bag with them or have them already in the car when driving, and put them in before setting out, then stop and reinstil drops if they need them.
I wrote this blog post after I read a very interesting paper called Characteristics of symptoms experienced by persons with dry eye disease while driving in China, published in Eye, in July 2017, volume 31, pages 1550 to 1555, by Wang Y et al.