Venous oxygen saturation is reduced and variable in central retinal vein occlusion

Self Cite

Dear editor;We want to thank Yolcu et al. for their insightful letter about our study. We fully agree with their opinion on pertinence for oximetric results of central retinal vein occlusion (CRVO) eyes with and without macular edema or retinal ischemia to be compared with each other. We also agree that its results can be compared with fluorescein angiography and optical coherence tomography findings in different sectors of the retinal fundus. This is important in order to explore the clinical utility of the oximeter.Our study [1] demonstrates variable retinal hypoxia in CRVO eyes that in general seems to get better with time, treatment and improving clinical symptoms.Our preliminary findings suggest a correlation between retinal oximeter measurements and clinical signs and symptoms. Hypoxia measurements in retinal venules were consistent with capillary nonperfusion on fluorescein angiography [1].We agree that assessing patients by optical coherence tomography and fluorescein angiography and comparing with retinal oximeter measurements will provide valuable information for the pathogenesis and management of CRVO. We have started a multicenter study in order to answer the aforementioned questions and pursue the clinical utility of retinal oximetry in CRVO. Conflict of interest

“…Hypoxia measurements in retinal venules were consistent with capillary nonperfusion on fluorescein angiography [1].…”

Section: Dear Editor;supporting

confidence: 61%

“…Our study [1] demonstrates variable retinal hypoxia in CRVO eyes that in general seems to get better with time, treatment and improving clinical symptoms.…”

Section: Dear Editor;supporting

confidence: 53%

supporting

confidence: 53%

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Response to the letter to the editor: Venous oxygen saturation is reduced and variable in central retinal vein occlusion

Eliasdottir

Bragason

Hardarson

et al. 2015

Self Cite

“…

Dear Editor;We thank Gokce et al for their comments on our article about reduced and variable venous oxygen saturation in central retinal vein occlusion (CRVO) [1]. They suggest that environmental chronic cold exposure of our subjects, which is not mentioned in the study, might have affected the results by modifying hematologic and cardiovascular risk factors for CRVO.

We would be careful of making any assumptions about the impact of climate on hematological and cardiovascular risk factors in our study population.

…”

mentioning

confidence: 98%

Venous oxygen saturation is reduced and variable in central retinal vein occlusion

Eliasdottir

Bragason

Hardarson

et al. 2015

Self Cite

Dear Editor;We thank Gokce et al. for their comments on our article about reduced and variable venous oxygen saturation in central retinal vein occlusion (CRVO) [1]. They suggest that environmental chronic cold exposure of our subjects, which is not mentioned in the study, might have affected the results by modifying hematologic and cardiovascular risk factors for CRVO.We would be careful of making any assumptions about the impact of climate on hematological and cardiovascular risk factors in our study population. In Iceland, the average winter temperature is about 0°C (32°F), and during the months when the study was performed, the average temperature was 5°C (ranging from 0 to 12.7°C). Plenteous geothermal natural resources provide relatively inexpensive space heating, which is abundantly used by the nation, and indoor temperatures are 20-25°C. The oximetry measurements were made in this temperature range.To the best of our knowledge, there is no evidence that links cold exposure to the pathogenesis and prevalence of CRVO, and we do not consider our study subjects susceptible to cold temperature eye injury. Intraocular temperature has been related to the core temperature of the body [2]. Both in vitro and in vivo experiments at an ambient air temperature of −40°C indicate the role of corneal tissue in limiting heat conductivity between the corneal surface and intraocular environment, thus providing a stable temperature of about +37°C in the anterior chamber compared with +24.3°C on the corneal surface [2].In our study, we used comparable images of the fellow unaffected eye of the same patient, which is exposed to the same temperature and risk factors, to measure oxygen saturation in retinal arterioles and venules for comparative statistical analysis. We think the most likely reason for the marked reduction in venular oxygen saturation in CRVO eyes (p<0.0001, paired t-test) is stagnation of blood due to the venous occlusion. We also suggest that the apparent variability in retinal venous oxygen saturation in CRVO eyes (both within each eye and between eyes) reflects individual differences in the severity of the venous obstruction [3], which may partly be explained by the various compensatory mechanisms against the venous occlusion. Conflict of interest

“…

Dear Editor, We congratulate Eliasdottir et al [1] for their study entitled 'Venous oxygen saturation is reduced and variable in central retinal vein occlusion'. The authors used a non-invasive spectrophotometric retinal oximeter for measuring hemoglobin oxygen saturation in retinal vessels.

…”

mentioning

confidence: 99%

Venous oxygen saturation is reduced and variable in central retinal vein occlusion

Yolcu

İlhan

Gündoğan

et al. 2015

Dear Editor, We congratulate Eliasdottir et al. [1] for their study entitled 'Venous oxygen saturation is reduced and variable in central retinal vein occlusion'. The authors used a non-invasive spectrophotometric retinal oximeter for measuring hemoglobin oxygen saturation in retinal vessels. They concluded that central retinal vein occlusion (CRVO) eyes are hypoxic compared to fellow eyes, and hemoglobin oxygen saturation is increased between arterioles and venules. We would like to share our reservations about the study.Fundus fluorescein angiography (FFA) and optical coherence tomography (OCT) are widely used for evaluation of CRVO cases. The authors also shared a patient's FFA and OCT results in figure legend 4. Retinal oximetry is a recently developed diagnostic tool. We think that assessing the patients by OCT and FFA and comparing them with retinal oximetry results can provide precious clues for the pathogenesis and management of CRVO.If available, we wonder if oximetric results of CRVO eyes with and without macular edema or CRVO eyes with or without retinal ischemia may be compared with each other. We think that its results also can be compared with FFA and OCT results in concordant and/or discordant sectors. We believe that these additional analyses will make it easy to reach reasonable inferences from the findings of the oximeter and increase the reliability of it. Conflict of interest