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Ocular vasodynamic changes in light and darkness in smokers
Ulf Havelius1, Flemming Hansen
1Department of Ophthalmology, Malmö University Hospital, Lund University, S-205 02 Malmö, Sweden. ulf.havelius@oftal.mas.lu.se
Investigative Ophthalmology & Visual Science
|April 27, 2005
Summary
Smokers show a reduced ability to increase retinal blood flow in darkness, potentially explaining impaired night vision. This impacts ocular blood flow regulation in cigarette users.
Area of Science:
- Ophthalmology
- Vascular Physiology
- Cardiovascular Research
Background:
- Smoking is a known risk factor for various vascular diseases.
- Impaired dark vision has been anecdotally reported in smokers.
- Understanding the impact of smoking on ocular hemodynamics is crucial for preventative eye care.
Purpose of the Study:
- To investigate the effect of smoking on the dynamic regulation of retinal blood flow velocity.
- To determine if smokers exhibit a diminished capacity for increased retinal blood flow in low-light conditions.
Main Methods:
- Color Doppler ultrasound was used to measure peak systolic (V(S)) and end-diastolic (V(D)) flow velocities.
- Measurements were taken in the ophthalmic and central retinal arteries under light and dark conditions.
- Resistive index (RI) was calculated to assess vascular resistance.
Main Results:
- Nonsmokers demonstrated significant increases in V(D) and decreases in RI in darkness, indicating enhanced blood flow.
- Smokers showed no significant changes in V(S) or V(D) between light and dark conditions in the ophthalmic artery.
- Changes in V(S) and V(D) in the central retinal artery were significantly smaller and not significant in smokers compared to nonsmokers.
Conclusions:
- Smokers have a markedly reduced capacity for increasing central retinal artery blood flow velocity in darkness.
- This impairment in ocular blood flow regulation may underlie the reduced dark vision experienced by smokers.
- Potential contributing factors include increased blood viscosity, nicotine's vasoconstrictive effects, and reduced oxygen transport due to carbon monoxide.