550235 research-article2014
PRF0010.1177/0267659114550235PerfusionTan et al.
Letter to the Editor
Choroidal thickness after cardiopulmonary bypass
Perfusion 2014, Vol. 29(6) 573–574 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0267659114550235 prf.sagepub.com
CSH Tan,1,2 JC Chan1 and KX Cheong1
Sir, We read with interest the article by Pekel et al.1 describing the changes in subfoveal choroidal thickness, ocular pulse amplitude and intraocular pressure following cardiopulmonary bypass. The authors reported that there were no significant changes in either subfoveal choroidal thickness or ocular pulse amplitude one week and one month after surgery. These findings provide important insights into the potential long-term effects of significant systemic hemodynamic changes on ocular parameters. In this study, the authors measured choroidal thickness at a single point (subfoveally), which may represent a potential limitation of this study. The choroid is a complex three-dimensional structure with a highly anastomosed network of vessels. Several studies have reported considerable topographic variation of the choroid at the macula.2–5 Many studies have reported that the choroid is thickest either subfoveally or in the temporal or superior sectors, while the region nasal to the fovea is usually thinnest.2–5 It is possible that some regions of the choroid may be more sensitive to systemic hemodynamic changes compared to the subfoveal region and these regions may manifest observable changes in choroidal thickness when subjected to hemodynamic stress while the thickness remains relatively unchanged subfoveally. It may be useful in subsequent studies to assess the choroidal thickness at different regions of the macula, for example, by measuring the choroid at different distances from the fovea, both horizontally and vertically. It is also useful to measure the mean choroidal thickness within pre-defined sectors, such as the Early Treatment Diabetic Retinopathy Study grid, as this may give a more comprehensive reflection of the choroidal topography compared to a single-point thickness measurement.2 The authors observed a significant increase in choroidal thickness one week postoperatively for the subgroup of patients who had valve repair only and speculated that this may be due to the low number of participants in that sub-group (n=11).1 While this explanation is certainly possible, the observed difference could also be due to diurnal variation of choroidal
thickness. A few studies have demonstrated significant and repeatable patterns of diurnal variation of choroidal thickness throughout the day.6,7 It would be interesting to know if the time of the optical coherence tomography scans at the pre-operative and follow-up visits of these patients were standardized or if the examinations occurred at different times of the day. Since the amplitude (difference between the maximum and minimum choroidal thickness) has been reported to be as high as 67 µm,6 the observed difference at one week could partly be accounted for by diurnal variation. In the same way, intraocular pressure has also been shown to vary throughout the day and any differences in the time of measurement may also affect the comparison of intraocular pressure at different follow-up periods. In summary, we congratulate the authors on their results, and look forward to further studies elucidating the effects of systemic hemodynamic changes on choroidal thickness and intraocular pressure. Declaration of conflicting interest The authors declare that there is no conflict of interests.
Funding Dr Tan receives research funding from the National Healthcare Group Clinician Scientist Career Scheme Grant. (Code: CSCS/12005). Dr Tan also receives conference support from Bayer (South East Asia) Pte Ltd (Code: R), Heidelberg Engineering and Novartis. Mr Chan and Dr Cheong do not receive any funding. The authors have no financial or proprietary interests in the subject of this manuscript.
1Department
of Ophthalmology, Tan Tock Seng Hospital, Singapore Image Reading Center, National Healthcare Group Eye Institute, Singapore
2Fundus
Corresponding author: Colin SH Tan National Healthcare Group Eye Institute Tan Tock Seng Hospital 11 Jalan Tan Tock Seng, 308433 Singapore. Email: [email protected]
Downloaded from prf.sagepub.com at UCSF LIBRARY & CKM on April 3, 2015
574
Perfusion 29(6)
References 1. Pekel G, Alur I, Alihanoglu Y, et al. Choroidal changes after cardiopulmonary bypass. Perfusion 2014; 29: 560–566. 2. Tan CS, Cheong KX, Lim LW, et al. Topographic variation of choroidal and retinal thicknesses at the macula in healthy adults. Br J Ophthalmol 2014; 98: 339–344. 3. Tanabe H, Ito Y, Terasaki H. Choroid is thinner in inferior region of optic disks of normal eyes. Retina 2012; 32: 134–139. 4. Agawa T, Miura M, Ikuno Y, et al. Choroidal thickness measurement in healthy Japanese subjects by three-dimensional high-penetration optical coherence
tomography. Graefes Arch Clin Exp Ophthalmol 2011; 249: 1485–1492. 5. Hirata M, Tsujikawa A, Matsumoto A, et al. Macular choroidal thickness and volume in normal subjects measured by swept-source optical coherence tomography. Invest Ophthalmol Vis Sci 2011; 52: 4971–4978. 6. Tan CS, Ouyang Y, Ruiz H, et al. Diurnal variation of choroidal thickness in normal, healthy subjects measured by spectral domain optical coherence tomography. Invest Ophthalmol Vis Sci 2012; 53: 261–266. 7. Usui S, Ikuno Y, Akiba M, et al. Circadian changes in subfoveal choroidal thickness and the relationship with circulatory factors in healthy subjects. Invest Ophthalmol Vis Sci 2012; 53: 2300–2307.
Downloaded from prf.sagepub.com at UCSF LIBRARY & CKM on April 3, 2015
PRF0010.1177/0267659114550235PerfusionTan et al.
Letter to the Editor
Choroidal thickness after cardiopulmonary bypass
Perfusion 2014, Vol. 29(6) 573–574 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0267659114550235 prf.sagepub.com
CSH Tan,1,2 JC Chan1 and KX Cheong1
Sir, We read with interest the article by Pekel et al.1 describing the changes in subfoveal choroidal thickness, ocular pulse amplitude and intraocular pressure following cardiopulmonary bypass. The authors reported that there were no significant changes in either subfoveal choroidal thickness or ocular pulse amplitude one week and one month after surgery. These findings provide important insights into the potential long-term effects of significant systemic hemodynamic changes on ocular parameters. In this study, the authors measured choroidal thickness at a single point (subfoveally), which may represent a potential limitation of this study. The choroid is a complex three-dimensional structure with a highly anastomosed network of vessels. Several studies have reported considerable topographic variation of the choroid at the macula.2–5 Many studies have reported that the choroid is thickest either subfoveally or in the temporal or superior sectors, while the region nasal to the fovea is usually thinnest.2–5 It is possible that some regions of the choroid may be more sensitive to systemic hemodynamic changes compared to the subfoveal region and these regions may manifest observable changes in choroidal thickness when subjected to hemodynamic stress while the thickness remains relatively unchanged subfoveally. It may be useful in subsequent studies to assess the choroidal thickness at different regions of the macula, for example, by measuring the choroid at different distances from the fovea, both horizontally and vertically. It is also useful to measure the mean choroidal thickness within pre-defined sectors, such as the Early Treatment Diabetic Retinopathy Study grid, as this may give a more comprehensive reflection of the choroidal topography compared to a single-point thickness measurement.2 The authors observed a significant increase in choroidal thickness one week postoperatively for the subgroup of patients who had valve repair only and speculated that this may be due to the low number of participants in that sub-group (n=11).1 While this explanation is certainly possible, the observed difference could also be due to diurnal variation of choroidal
thickness. A few studies have demonstrated significant and repeatable patterns of diurnal variation of choroidal thickness throughout the day.6,7 It would be interesting to know if the time of the optical coherence tomography scans at the pre-operative and follow-up visits of these patients were standardized or if the examinations occurred at different times of the day. Since the amplitude (difference between the maximum and minimum choroidal thickness) has been reported to be as high as 67 µm,6 the observed difference at one week could partly be accounted for by diurnal variation. In the same way, intraocular pressure has also been shown to vary throughout the day and any differences in the time of measurement may also affect the comparison of intraocular pressure at different follow-up periods. In summary, we congratulate the authors on their results, and look forward to further studies elucidating the effects of systemic hemodynamic changes on choroidal thickness and intraocular pressure. Declaration of conflicting interest The authors declare that there is no conflict of interests.
Funding Dr Tan receives research funding from the National Healthcare Group Clinician Scientist Career Scheme Grant. (Code: CSCS/12005). Dr Tan also receives conference support from Bayer (South East Asia) Pte Ltd (Code: R), Heidelberg Engineering and Novartis. Mr Chan and Dr Cheong do not receive any funding. The authors have no financial or proprietary interests in the subject of this manuscript.
1Department
of Ophthalmology, Tan Tock Seng Hospital, Singapore Image Reading Center, National Healthcare Group Eye Institute, Singapore
2Fundus
Corresponding author: Colin SH Tan National Healthcare Group Eye Institute Tan Tock Seng Hospital 11 Jalan Tan Tock Seng, 308433 Singapore. Email: [email protected]
Downloaded from prf.sagepub.com at UCSF LIBRARY & CKM on April 3, 2015
574
Perfusion 29(6)
References 1. Pekel G, Alur I, Alihanoglu Y, et al. Choroidal changes after cardiopulmonary bypass. Perfusion 2014; 29: 560–566. 2. Tan CS, Cheong KX, Lim LW, et al. Topographic variation of choroidal and retinal thicknesses at the macula in healthy adults. Br J Ophthalmol 2014; 98: 339–344. 3. Tanabe H, Ito Y, Terasaki H. Choroid is thinner in inferior region of optic disks of normal eyes. Retina 2012; 32: 134–139. 4. Agawa T, Miura M, Ikuno Y, et al. Choroidal thickness measurement in healthy Japanese subjects by three-dimensional high-penetration optical coherence
tomography. Graefes Arch Clin Exp Ophthalmol 2011; 249: 1485–1492. 5. Hirata M, Tsujikawa A, Matsumoto A, et al. Macular choroidal thickness and volume in normal subjects measured by swept-source optical coherence tomography. Invest Ophthalmol Vis Sci 2011; 52: 4971–4978. 6. Tan CS, Ouyang Y, Ruiz H, et al. Diurnal variation of choroidal thickness in normal, healthy subjects measured by spectral domain optical coherence tomography. Invest Ophthalmol Vis Sci 2012; 53: 261–266. 7. Usui S, Ikuno Y, Akiba M, et al. Circadian changes in subfoveal choroidal thickness and the relationship with circulatory factors in healthy subjects. Invest Ophthalmol Vis Sci 2012; 53: 2300–2307.
Downloaded from prf.sagepub.com at UCSF LIBRARY & CKM on April 3, 2015
