Smell Sensitivity in Primary Open-angle Glaucoma and Pseudoexfoliation Glaucoma

PRCIS

This cross-sectional study of 20 patients with primary open-angle glaucoma (POAG), 20 with exfoliative glaucoma (XFG), 20 with exfoliation syndrome (XS) showed that exfoliative group had a significantly lower smell identification level as compared with the control groups.

PURPOSE

To investigate smell sensitivity in POAG, XFG, and XFS in comparison with healthy controls.

MATERIALS AND METHODS

This prospective, cross-sectional study included 20 patients with POAG, 20 with XFG, and 20 with XFS. The control group consisted of 20 age-matched and sex-matched healthy subjects with no evidence of ocular disease. The Sniffin' Sticks smell test was used to determine the, threshold values, and to assess the ability of smell identification, and differentiation in all patients One eye per patient was included for statistical purposes. One-way analysis of variance was used to compare the differences between the groups. Tukey honestly significant difference was used as a post hoc test when significant differences were detected among the 3 groups.

RESULTS

The XFG, POAG, and control groups showed a significant difference in the odor discrimination, odor identification, and threshold discrimination identification scores. The median (minimum-maximum) smell threshold levels for the POAG, XFG, and XFS groups and healthy controls were 4.5 (0 to 7.5), 4 (0 to 7.5), 5 (4.5 to 6), and 5.5 (4 to 7.5), respectively. The smell differentiation values for the POAG, XFG, and XFS groups and healthy controls were 12 (2 to 14), 8 (0 to 13), 11 (10 to 13), and 12 (9 to 14), respectively. Smell sensitivity for the POAG, XFG, and XFS groups and healthy controls were 26 (4 to 30.5), 19 (0 to 29.5), 28.3 (22.8 to 30.5), and 29 (26.5 to 32), respectively. The smell sensitivity and differentiation were significantly different among the groups (P<0.001). The XFG group had a significantly lower smell identification level than the POAG, XFS, and control groups.

CONCLUSION

Patients with XFS and XFG revealed reduced smell sensitivity and identification compared with patients with POAG and those without glaucoma. These findings provide new insights into neural degeneration and pseudoexfoliation.

Neuroimmunoendocrine Link Between Chronic Kidney Disease and Olfactory Deficits

Chronic kidney disease (CKD) is a multifactorial pathology that progressively leads to the deterioration of metabolic functions and results from deficient glomerular filtration and electrolyte imbalance. Its economic impact on public health is challenging. Mexico has a high prevalence of CKD that is strongly associated with some of the most common metabolic disorders like diabetes and hypertension. The gradual loss of kidney functions provokes an inflammatory state and endocrine alterations affecting several systems. High serum levels of prolactin have been associated with CKD progression, inflammation, and olfactory function. Also, the nutritional status is altered due to impaired renal function. The decrease in calorie and protein intake is often accompanied by malnutrition, which can be severe at advanced stages of the disease. Nutrition and olfactory functioning are closely interconnected, and CKD patients often complain of olfactory deficits, which ultimately can lead to deficient food intake. CKD patients present a wide range of deficits in olfaction like odor discrimination, identification, and detection threshold. The chronic inflammatory status in CKD damages the olfactory epithelium leading to deficiencies in the chemical detection of odor molecules. Additionally, the decline in cognitive functioning impairs the capacity of odor differentiation. It is not clear whether peritoneal dialysis and hemodialysis improve the olfactory deficits, but renal transplants have a strong positive effect. In the present review, we discuss whether the olfactory deficiencies caused by CKD are the result of the induced inflammatory state, the hyperprolactinemia, or a combination of both.

Cortical Plasticity and Olfactory Function in Early Blindness

Over the last decade, functional brain imaging has provided insight to the maturation processes and has helped elucidate the pathophysiological mechanisms involved in brain plasticity in the absence of vision. In case of congenital blindness, drastic changes occur within the deafferented “visual” cortex that starts receiving and processing non visual inputs, including olfactory stimuli. This functional reorganization of the occipital cortex gives rise to compensatory perceptual and cognitive mechanisms that help blind persons achieve perceptual tasks, leading to superior olfactory abilities in these subjects. This view receives support from psychophysical testing, volumetric measurements and functional brain imaging studies in humans, which are presented here.