COPD negatively affects retina and optical nerve
MedWire News: Chronic obstructive pulmonary disease (COPD) could have negative effects on patients' retinas and optical nerves, say Turkish researchers.
Their study results indicate that COPD patients' standard achromatic perimetry (SAP) and short-wavelength automated perimetry (SWAP) measurements - both markers of visual field assessment - deviated significantly more from the median than did study participants' without the lung condition.
The research team believes that the relationship between COPD and the retina/optical nerve could be explained by hypoxia and its potential to cause neuropathy.
A total of 67 people took part in the study including 38 with COPD, classified according to Global Initiative for Chronic Obstructive Lung Disease 2006 Guidelines, and 29 without the condition (healthy controls).
All participants underwent eye examinations to enable visual field analysis and visual evoked potentials to be extracted.
"Visual field assessment is one of the major diagnostic tools in neuroophthalmologic disorders and glaucoma," write Helin Deniz Demir (Gaziosmanpasa University, Tokat) and colleagues in Acta Opthalmologica.
The team found no significant differences in the mean refractive error of the right and left eyes between the COPD patients and the healthy controls, neither were there differences in mean intraocular pressure, nor cup/disc ratio.
By contrast, the mean deviation, pattern standard deviation, and corrected pattern standard deviation differed significantly for COPD patients versus healthy control participants in both SAP and SWAP measurements.
Specifically, these values were a respective -5.90 versus -3.42, 4.07 versus 3.07, and 3.04 versus 1.80 for SAP, and -9.99 versus -6.74, 4.27 versus 3.59, and 2.74 versus 1.84 for SWAP.
The difference in SAP and SWAP short-term fluctuation was nonsignificant for COPD patients and healthy controls.
In all, 11 COPD patients (28.9%) were current smokers and 24 (63.1%) had quit in the past year, while none of the healthy controls were smokers or had smoked.
Demir and co-investigators note that smoking is a contributing factor to COPD-related neuropathy, as well as a cause of decreased blood flow in ocular and retinal blood vessels, deranged autoregulation, and a reducer of the oxygen-carrying capacity of hemoglobin.
However, despite these recognized associations, "we could not detect a correlation between cigarette smoking and parameters of both visual fields," writes the team.
Previous studies have shown that retinal ganglion cell function is reduced with decreased arterial blood oxygen during mild hypoxia, and ganglion cell death is thought to be caused by the hypoxia-related imbalance between vasoconstrictor endothelin and vasodilator nitric oxide in patients with obstructive sleep apnea syndrome.
Thus, "our study results have suggested that retina and optic nerve seem to be [a]ffected by COPD-related hypoxemia, vascular and endothelial dysfunction," conclude Demir et al.
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By Sarah Guy