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Indian J OphthalmolIndian J OphthalmolIJOIndian Journal of Ophthalmology0301-47381998-3689Medknow Publications & Media Pvt Ltd India IJO-66-122810.4103/ijo.IJO_431_18Letters to the EditorComparison of central corneal thickness measurement with Sirius Topographer and Nidek Axial Length Scan Mansoori Tarannum Sita Lakshmi Glaucoma Center, Anand Eye Institute, Hyderabad, Telangana, India
Correspondence to: Dr. Tarannum Mansoori, 7-147/1, Anand Eye Institute, Hyderabad, Telangana, India. E-mail: tarannummansoori@yahoo.com8 2018 66 8 1228 1229 Copyright: © 2018 Indian Journal of Ophthalmology2018This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.
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Sir,

I read with interest the article by Duman et al.[1] on “Comparison of anterior segment measurements using Sirius Topographer® and Nidek Axial Length-Scan® (AL-scan) with assessing repeatability in patients with cataract” (mean age, 71.79 ± 7.91 years). We would like to mention a few points in relation to central corneal thickness (CCT) measurement in their study.

The study reports mean CCT of 523.46 ± 40.58 μm with AL-scan and 545.32 ± 41.38 μm with Sirius Topographer in 43 eyes, for the first measurement. Using the same devices, we found lower mean CCT with AL-scan and Sirius Topographer, which was 507.43 ± 33.54 and 512.08 ± 33.1 μm, respectively, in 127 healthy eyes (mean age, 35.91 + 7.7 years).[2] The present study[1] found a mean difference of 19.759 for CCT measurement and poor agreement with 95% limits of agreement (LoA) to be 17.220–22.299 (P = 0.00) between the 2 devices. Our study reported a mean difference of − 4.6 μm for CCT and high level of agreement (95% LoA: -12.2 to 2.9, P = 0.26) between the 2 devices.

One of the reasons for the significant mean difference in CCT between the 2 devices in the present study could be because of the fact that the measurements were taken between 10 am and 5 pm which could have affected the diurnal variation in CCT, when compared with our study where the CCT measurements were obtained between 3 pm and 5 pm. Furthermore, the difference in mean CCT between the 2 studies could be because of the difference in age, sample size, and ethnicity[3] of the population studied.

Financial support and sponsorship
Nil.

Conflicts of interest
There are no conflicts of interest.
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1 Duman R  Çetinkaya E  Duman R  Dogan M  Sabaner MC   Comparison of anterior segment measurements using sirius topographer® and nidek axial length-scan® with assessing repeatability in patients with cataracts Indian J Ophthalmol 2018 66 402 6 29480251 
2 Mansoori T  Balakrishna N   Repeatability and agreement of central corneal thickness measurement with non-contact methods: A comparative study Int Ophthalmol 2017 doi: 10.1007/s10792-017-0543-1 [Epub ahead of print] 
3 Shimmyo M  Ross AJ  Moy A  Mostafavi R   Intraocular pressure, goldmann applanation tension, corneal thickness, and corneal curvature in Caucasians, Asians, hispanics, and African Americans Am J Ophthalmol 2003 136 603 13 14516799