© Borgis - Postępy Nauk Medycznych 12/2013, s. 865-867
*Ewa Czaplicka1, Iwona Grabska-Liberek2, Iwona Rospond1, Jarosław Kocięcki1
Narażenie na dym tytoniowy i jego wpływ na narząd wzroku
Environmental exposure to tobacco smoke and condition of organ of vision
1Department and Clinic of Ophthalmology, Poznań University of Medical Sciences
Head of Department and Clinic: Jarosław Kocięcki, MD, PhD
2Clinic of Ophthalmology, Medical Center of Postgraduate Education, Warszawa
Head of Clinic: Iwona Grabska-Liberek, MD, PhD, assoc. prof.
Dostępne dane epidemiologiczne sugerują, że nikotyna jest odpowiedzialna za wyższy odsetek zejść śmiertelnych związanych z jej zażywaniem niż kokaina, nikotyna i alkohol łącznie.
Palenie czynne i bierne wywołuje istotny wpływ na struktury gałki ocznej , upośledza fizjologiczne procesy i stymuluje powstanie procesów patologicznych , które są odpowiedzialne za powstawanie chorób oczu. Badania przeprowadzone w obrębie nauk podstawowych umożliwiają głębsze zrozumienie mechanizmów wpływu nikotyny na narząd wzroku oraz ich związek z rozwojem i progresją schorzeń okulistycznych.
Autorzy omawiają toksyczny wpływ nikotyny na szereg struktur narządu wzroku i funkcję widzenia. Wyjaśniają rolę palenia i uzależnienia od nikotyny w patogenezie wielu chorób oczu.
According to the most recent epidemiological data, nicotine causes a greater number of addiction-related deaths than cocaine, heroin and alcohol combined. Its toxicity also significantly affects the organ of sight.
Smoking exerts a severe influence on all structures of the eyeball, impairing physiological processes as well as stimulating pathological processes which result in eye diseases. Studies conducted within fundamental science allow for a deeper understanding of the mechanisms of nicotine influence on the organ of sight and its connection to the development and progression of ophthalmic diseases.
The authors comment the toxic effect of nicotine on several anatomical structures of the eye and the visual function and discuss the role of smoking and nicotine abuse in the pathogenesis of several ocular diseases.
Nicotine was named after J. Nicot (1530-1600), a French ambassador in Lisbon who was sending tobacco leaves to France, thus making tobacco smoking popular. According to the most recent epidemiological data, nicotine causes a greater number of addiction-related deaths than cocaine, heroin and alcohol combined (1-3). Its toxicity also significantly affects the organ of sight (2, 3).
As an irritant, the tobacco smoke can cause conjunctival irritation and symptoms of the dry eye syndrome. This disease occurs frequently in industrialised countries. In the USA there are approximately 59 million patients suffering from this disease, and the number has doubled in the last 10 years (4). Demographic data show that approx. 25-40% of employees are exposed to tobacco smoke at work, due to both active and second-hand smoking and 25% of them exhibit symptoms of the dry eye syndrome. Grus et al. conducted research into the chemical composition of tear film in smokers. In comparison to a control group of non-smokers, a significant increase of lower molecular weight protein content in tears was observed, as well as an overexpression of area of 25-40 kDa molecular weight in electrophoresis. According to the authors, these changes are a result of the toxic effect of tobacco smoke which causes oxidative damage to proteins and might potentially increase the concentration of smaller protein fragments present in the tear film. Smoking can also damage or change the blood flow in this area causing transudation of protein molecules. Moreover, there are indicators of damage caused through free radicals in these patients (4).
In histopathological studies, Satici et al. showed a metaplasia of conjunctival epithelium and its keratinization in persons exposed to tobacco smoke. According to the authors, these changes are caused by a change in the stability of tear film in smokers resulting from lipid layer deficiency, which may additionally intensify lacrimation and cause irritation to eye surface tissues. A decrease of lysozyme content in tears caused by its local binding by toxins present in tobacco smoke has also been described (5). Because smoking intensifies the symptoms of dry eye syndrome it can also cause contact lens intolerance (2, 3). Smoking can be also a risk factor for spinocellular carcinoma of the conjunctiva (6).
Smoking is also risk factor for lens opacification. In Reykjavik Eye Study, the influence of different risk factors for lens opacification in Reykjavik inhabitants was assessed. It was demonstrated that apart from ageing, smoking was the most important variable risk factor for opacifications of this type (not demonstrated in cortico-nuclear opacifications) (2, 3, 7).
Smoking is an acknowledged risk factor for the development of many systemic vessels diseases. Nicotine influences the increase of catecholamines level in blood, which manifests as tachycardia and arterial blood pressure increase. Tobacco smoke contains 2-6% of carbon monoxide among other components. Smoking leads to increased level of carboxyhemoglobin, up to 5-15% (0.5% in non-smokers). This increases the accessibility of oxyhaemoglobin, changes its dissociation curve and decreases the oxygen supply to tissues as a result. Oxygen deficit, through regulatory mechanisms, causes dilation of vessels and increase of blood flow velocity. The changes described also apply to eyeball and retrobulbar vessels. Kaiser et al. described that the increase of the blood flow velocity mostly concerns ophthalmic artery, middle artery, central retinal vein and lateral short posterior ciliary artery in comparison to the non-smoking group. The author also observed a lowered diastolic and systolic blood pressure as well as tachycardia in smokers (2, 3, 8).
Smoking also causes changes in microcirculation. Steigerwalt et al. in turn describeda 36% decrease in blood flow velocity in contraction and 52% in decontraction in ophthalmic artery, central retinal artery and posterior ciliary artery. According to the authors, this happens because of a contraction of minute vessels of the retinal and optic disc through sympathetic system excitation. This is why smoking may intensify the course of numerous ophthalmic diseases related to blood flow disorders e.g. diabetes, central retinal vein thrombosis, ischemic optic neuropathy and giant cell arteritis (Horton’s disease) (2, 3, 9).
Apart from cardiovascular factors including arterial hypertension, smoking is an important risk factor for retinal vein thromboses. The most recent studies show that smoking plays an important role in the etiology of thromboses taking place in arteriovenous crossings – in a prospective analysis of 874 eyes such thromboses were the most frequently observed type (2, 3, 10).
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