Changes in oxygen saturation and the retinal nerve fibre layer in patients with optic neuritis associated with multiple sclerosis in a 6-month follow-up

Correlation between retinal oxygen saturation and the haemodynamic parameters of the ophthalmic artery in healthy subjects

PURPOSE

The aim of the study was to obtain the values of oxygen saturation in retinal vessels and ophthalmic blood flow parameters in a healthy Caucasian population and assess whether the oximetry parameters are affected by the flow rate or the vascular resistance.

METHODS

The spectrophotometric retinal oximetry and colour Doppler imaging (CDI) of retinal vessels were successfully performed with 52 healthy subjects (average age 29.7 ± 5.6 years). The retinal oximeter simultaneously measures the wavelength difference of haemoglobin oxygen saturation in retinal arterioles and venules. The arteriolar and venular saturation in both eyes was measured. The peak systolic (PSV) end diastolic (EDV) velocities, resistive (RI) and pulsatility (PI) indices were obtained for both eyes using CDI in the ophthalmic artery. A paired t-test and two sample t-tests were used for statistical analyses. The correlation was assessed using the Pearson coefficient correlation.

RESULTS

The mean oxygen saturation level was 96.9 ± 3.0% for the retinal arterioles and 65.0 ± 5.1% for the retinal venules. The A-V difference was 31.8 ± 4.6%. The mean of the measured haemodynamic parameters was PSV 46.6 ± 9.4 cm/s, EDV 12.0 ± 3.5 cm/s, PI 1.68 ± 0.38 and RI 0.74 ± 0.05. No significant difference in oxygen saturation and haemodynamic parameters was found between the left and the right eyes or the dominant and non-dominant eye. The oximetry and ultrasound values were sex independent. The Pearson correlation coefficient demonstrated a significant yet weak negative correlation between A-V difference and RI (r = -0.321, p = 0.020).

CONCLUSIONS

A negative correlation between A-V difference and resistance index was observed, suggesting that reduced oxygen consumption may reflect the increased vascular tone of the ophthalmic vessels, which is likely determined by autoregulatory mechanisms.

Clinical Analysis of Color Doppler Ultrasound Diagnosis of Senile Cataract Based on Intelligent Processor

In order to improve the effect of on-the-spot diagnosis of senile cataract, this paper combines the intelligent processor to explore the application of color Doppler ultrasound in the clinical analysis of senile cataract. Moreover, this paper measures and calculates the diameter, perimeter, area, volume, or velocity of blood flow reflected by color Doppler ultrasound images. In addition, this paper adopts the measurement method provided by composite measurement to design the intelligent processor. Each measurement analysis package is defined as an independent class, and the data, properties, and methods are encapsulated in a class, which is beneficial to the modular design of the program and the overall management of the system. The experimental results verify that the intelligent processor proposed in this paper has a certain effect in the clinical analysis of color Doppler ultrasound diagnosis of senile cataract.

Retinal imaging biomarkers of neurodegenerative diseases

The timely detection of neurodegenerative diseases is central to improving clinical care as well as enabling the development and deployment of disease-modifying therapies. Retinal imaging is emerging as a method to detect features of a number of neurodegenerative diseases, given the anatomical and functional similarities between the retina and the brain. This review provides an overview of the current status of retinal imaging biomarkers of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Lewy body dementia, frontotemporal dementia, Huntington's disease and multiple sclerosis. Whilst research findings are promising, efforts to harmonise study designs and imaging methods will be important in translating these findings into clinical care. Doing so may mean that eye care providers will play important roles in the detection of a variety of neurodegenerative diseases in future.

Clinical implications of retinal oximetry in retinal vein occlusion: a review

PURPOSE

To review retinal vein occlusion (RVO) and its relationship with retinal oxygen saturation via automated retinal oximetry in eyes with RVO.

METHODS

A literature review was performed in PubMed and Medline until October 2021 utilizing specific keywords and cross-matched reference lists.

RESULTS

This review found RVO to be associated with risk factors including age, hypertension, cardiovascular and metabolic conditions, male gender, and glaucoma. These may be attributed to a breakdown of regulatory processes in the retina. Retinal venous oxygen saturation (SvO₂ ) and arteriovenous difference in eyes with central RVO have been found to be reduced and elevated, respectively. The literature indicates variable and contradictory findings in regard to branch RVO and retinal oxygenation. Additionally, ischaemic eyes have been found to have elevated retinal arterial oxygen saturation; however, the literature reports variable results regarding SvO₂ levels. Medications have been suggested to increase SvO₂ in RVO eyes, which may represent an important mechanism for disease management. Ranibizumab is currently the most studied drug for retinal oxygenation in RVO and has been suggested to increase SvO₂ in RVO eyes. In comparison, dexamethasone was found to decrease SvO₂ .

CONCLUSION

The current literature on retinal oxygenation in ischaemic subtypes of RVO and in drug therapies is minimal, and further work is required to expand upon our understanding of how ischaemia and drugs influence retinal oxygenation and clinical outcomes.