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LETTER TO THE EDITOR
Year : 2019  |  Volume : 67  |  Issue : 7  |  Page : 1252-1253

Interocular asymmetry in choroidal thickness in healthy Indian population using swept-source optical coherence tomography


Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India

Date of Web Publication25-Jun-2019

Correspondence Address:
Dr. Vinod Kumar
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Instituteof Medical Sciences, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_8_19

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How to cite this article:
Bhayana AA, Kumawat D, Kumar V, Chandra M, Chandra P, Sihota R, Kumar A. Interocular asymmetry in choroidal thickness in healthy Indian population using swept-source optical coherence tomography. Indian J Ophthalmol 2019;67:1252-3

How to cite this URL:
Bhayana AA, Kumawat D, Kumar V, Chandra M, Chandra P, Sihota R, Kumar A. Interocular asymmetry in choroidal thickness in healthy Indian population using swept-source optical coherence tomography. Indian J Ophthalmol [serial online] 2019 [cited 2019 Jul 16];67:1252-3. Available from: http://www.ijo.in/text.asp?2019/67/7/1252/261056



Dear Sir,

The assessment of choroidal thickness (CT) is of paramount importance in diagnosis and management of various ocular disorders. The inter-ocular asymmetry in CT should be kept in mind while analyzing the results of different studies. The authors had previously reported the normative data for sub-foveal CT (SFCT) in 119 healthy Indian patients (age 19–45 years, refractive error −6 to +4 diopters, best corrected visual acuity 20/20) using swept-source optical coherence tomography (SS-OCT, DRI-OCT, Topcon Japan).[1] The CT was further compared between the fellow eyes in different regions of the macular area based on the ETDRS (early treatment diabetic retinopathy study) grid.

The mean CT in the right eye was significantly greater than the left eye in all EDTRS regions except the temporal inner and outer regions [see [Table 1]], with the maximum difference in the nasal outer region (mean 14.39 μm, P = 0.0001, Student t test). The individual difference in the subfoveal CT (SFCT) between the right and left eye ranged from +133 to −125 μm. The SFCT was greater in the right eye as compared to left eye in 59% of the cases (n = 70).
Table 1: Details of mean choroidal thickness (in microns) in all 9 ETDRS zones; comparison of right and left eyes (mean±1SD)

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The inter-ocular asymmetry in CT may arise from the difference in ocular blood flow. The right ophthalmic artery receives blood from the brachiocephalic trunk which itself is more proximal to the left ventricle than the left common carotid artery which branches into the left ophthalmic artery.[2] The reason for maximum difference in the nasal macular region is not clearly understood. We hypothesize dominance of 1 eye in an individual to have some contribution to the asymmetry but this could not be confirmed retrospectively as this was a cross sectional study.

Similar inter-ocular differences in CT have been previously reported in Caucasian and Middle-Eastern patients using enhanced depth spectral domain OCT (SD-OCT).[3],[4],[5] As SS-OCT provides a better delineation of the CSI than SD-OCT, it may be superior in evaluating the CT. Ruiz-Medrano et al. had used SS-OCT for studying the inter-ocular CT difference in Spanish population.[2] The present study is the first to report the inter-ocular asymmetry in CT on SS-OCT in the Indian population.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Bhayana AA, Kumar V, Tayade A, Chandra M, Chandra P, Kumar A. Choroidal thickness in normal Indian eyes using swept-source optical coherence tomography. Indian J Ophthalmol 2019;67:252-5.  Back to cited text no. 1
[PUBMED]  [Full text]  
2.
Ruiz-Medrano J, Flores-Moreno I, Peña-García P, Montero JA, Duker JS, Ruiz-Moreno JM. Asymmetry in macular choroidal thickness profile between both eyes in a healthy population measured by swept-source optical coherence tomography. Retina 2015;35:2067-73.  Back to cited text no. 2
    
3.
Spaide RF, Koizumi H, Pozzoni MC. Enhanced depth imaging spectral-domain optical coherence tomography. Am J Ophthalmol 2008;146:496-500.  Back to cited text no. 3
    
4.
Chen FK, Yeoh J, Rahman W, Patel PJ, Tufail A, Da Cruz L. Topographic variation and interocular symmetry of macular choroidal thickness using enhanced depth imaging optical coherence tomography. Invest Ophthalmol Vis Sci 2012;53:975-85.  Back to cited text no. 4
    
5.
Al-Haddad C, El Chaar L, Antonios R, El-Dairi M, Noureddin B. Interocular symmetry in macular choroidal thickness in children. J Ophthalmol 2014;2014:472391.  Back to cited text no. 5
    



 
 
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