Current Developments in Corneal Topography and Tomography

Piotr Kanclerz, Ramin Khoramnia, Xiaogang Wang, Piotr Kanclerz, Ramin Khoramnia, Xiaogang Wang

Abstract

Introduction: Accurate assessment of the corneal shape is important in cataract and refractive surgery, both in screening of candidates as well as for analyzing postoperative outcomes. Although corneal topography and tomography are widely used, it is common that these technologies are confused. The aim of this study was to present the current developments of these technologies and particularly distinguish between corneal topography and tomography.

Methods: The PubMed, Web of Science and Embase databases were the main resources used to investigate the medical literature. The following keywords were used in various combinations: cornea, corneal, topography, tomography, Scheimpflug, Pentacam, optical coherence tomography.

Results: Topography is the study of the shape of the corneal surface, while tomography allows a three-dimensional section of the cornea to be presented. Corneal topographers can be divided into large- and small-cone Placido-based devices, as well as devices with color-LEDs. For corneal tomography, scanning slit or Scheimpflug imaging and optical coherence tomography may be employed. In several devices, corneal topography and tomography have been successfully combined with tear-film analysis, aberrometry, optical biometry and anterior/posterior segment optical coherence tomography.

Conclusion: There is a wide variety of imaging techniques to obtain corneal power maps. As different technologies are used, it is imperative that doctors involved in corneal surgery understand the science and clinical application of devices for corneal evaluation in depth.

Keywords: cornea; keratograph; optical coherence tomography; pentacam; scheimpflug imaging; tomography; topography.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Corneal topography in the Oculus Keratograph 5 M.
Figure 2
Figure 2
The Tracey iTrace device allows corneal aberrations to be analyzed.
Figure 3
Figure 3
Scheimpflug corneal tomography in the Mediworks Scansys tomographer.
Figure 4
Figure 4
Corneal tomography in a swept-source optical coherence tomography device, the Anterion (Heidelberg Engineering).

References

    1. Moshirfar M., Duong A., Ronquillo Y. StatPearls. StatPearls Publishing; Treasure Island, FL, USA: 2021. Corneal imaging.
    1. Fan R., Chan T.C., Prakash G., Jhanji V. Applications of corneal topography and tomography: A review. Clin. Experiment. Ophthalmol. 2018;46:133–146. doi: 10.1111/ceo.13136.
    1. Khoramnia R., Rabsilber T.M., Auffarth G.U. Central and peripheral pachymetry measurements according to age using the pentacam rotating scheimpflug camera. J. Cataract Refract. Surg. 2007;33:830–836. doi: 10.1016/j.jcrs.2006.12.025.
    1. Swartz T., Marten L., Wang M. Measuring the cornea: The latest developments in corneal topography. Curr. Opin. Ophthalmol. 2007;18:325–333. doi: 10.1097/ICU.0b013e3281ca7121.
    1. Oliveira C.M., Ribeiro C., Franco S. Corneal imaging with slit-scanning and scheimpflug imaging techniques. Clin. Exp. Optom. 2011;94:33–42. doi: 10.1111/j.1444-0938.2010.00509.x.
    1. Shih K.C., Tse R.H.-K., Lau Y.T.-Y., Chan T.C.-Y. Advances in corneal imaging: Current applications and beyond. Asia-Pac. J. Ophthalmol. 2019;8:105–114. doi: 10.22608/APO.2018537.
    1. Grzybowski A., Kanclerz P. Recent developments in cataract surgery. In: Grzybowski A., editor. Current Concepts Ophthalmology. Springer International Publishing; Basel, Switzerland: 2020. pp. 55–97.
    1. Ambrósio R., Jr., Belin M.W. Imaging of the cornea: Topography vs. Tomography. J. Refract. Surg. 2010;26:847–849. doi: 10.3928/1081597X-20101006-01.
    1. Nayak B.K., Dharwadkar S. Corneal topography and tomography. J. Clin. Ophthalmol. Res. 2015;3:45. doi: 10.4103/2320-3897.149379.
    1. Gatinel D. Corneal topography and wave front analysis. In: Albert D.M., Miller J., Azar D., Young L.H., editors. Albert Jakobiec’s Principles and Practice of Ophthalmology. Springer International Publishing; Basel, Switzerland: 2008. pp. 921–963.
    1. Grzybowski A., Kanclerz P. Beginnings of astigmatism understanding and management in the 19th century. Eye Contact Lens. 2018;44:S22–S29. doi: 10.1097/ICL.0000000000000449.
    1. Placido A. Novo instrumento de esploracao da cornea. Period. D’Oftalmol. Pract. 1880;5:27–30.
    1. Placido A. Neue instrumente. Cent. Fur Prakt. Augenheilkd. 1881:30–31.
    1. Ventura B.V., Al-Mohtaseb Z., Wang L., Koch D.D., Weikert M.P. Repeatability and comparability of corneal power and corneal astigmatism obtained from a point-source color light–emitting diode topographer, a placido-based corneal topographer, and a low-coherence reflectometer. J. Cataract. Refract. Surg. 2015;41:2242–2250. doi: 10.1016/j.jcrs.2015.11.003.
    1. Klein S.A. Axial curvature and the skew ray error in corneal topography. Optom. Vis. Sci. 1997;74:931–944. doi: 10.1097/00006324-199711000-00027.
    1. Iskander D.R., Davis B.A., Collins M.J. The skew ray ambiguity in the analysis of videokeratoscopic data. Optom. Vis. Sci. 2007;84:435–442. doi: 10.1097/OPX.0b013e3180590654.
    1. Kanellopoulos A.J., Asimellis G. Distribution and repeatability of corneal astigmatism measurements (magnitude and axis) evaluated with color light emitting diode reflection topography. Cornea. 2015;34:937–944. doi: 10.1097/ICO.0000000000000476.
    1. Kanellopoulos J. Asimellis comparison of placido disc and scheimpflug image-derived topography-guided excimer laser surface normalization combined with higher fluence CXL: The athens protocol, in progressive keratoconus. Clin. Ophthalmol. 2013;7:1385. doi: 10.2147/OPTH.S44745.
    1. Klein S.A. Corneal topography reconstruction algorithm that avoids the skew ray ambiguity and the skew ray error. Optom. Vis. Sci. 1997;74:945–962. doi: 10.1097/00006324-199711000-00028.
    1. Alonso-Caneiro D., Szczesna-Iskander D.H., Iskander D.R., Read S.A., Collins M.J. Application of texture analysis in tear film surface assessment based on videokeratoscopy. J. Optom. 2013;6:185–193. doi: 10.1016/j.optom.2013.07.006.
    1. King-Smith P.E., Begley C.G., Braun R.J. Mechanisms, imaging and structure of tear film breakup. Ocul. Surf. 2018;16:4–30. doi: 10.1016/j.jtos.2017.09.007.
    1. García-Marqués J.V., Martínez-Albert N., Talens-Estarelles C., García-Lázaro S., Cerviño A. Repeatability of non-invasive keratograph break-up time measurements obtained using oculus keratograph 5M. Int. Ophthalmol. 2021;41:2473–2483. doi: 10.1007/s10792-021-01802-4.
    1. Wang M.T.M., Craig J.P. Comparative evaluation of clinical methods of tear film stability assessment: A randomized crossover trial. JAMA Ophthalmol. 2018;136:291–294. doi: 10.1001/jamaophthalmol.2017.6489.
    1. Rozema J.J., Van Dyck D.E.M., Tassignon M.-J. Clinical comparison of 6 aberrometers. Part 1: Technical specifications. J. Cataract Refract. Surg. 2005;31:1114–1127. doi: 10.1016/j.jcrs.2004.11.051.
    1. Rozema J.J., Van Dyck D.E.M., Tassignon M.-J. Clinical comparison of 6 aberrometers part 2: Statistical comparison in a test group. J. Cataract. Refract. Surg. 2006;32:33–44. doi: 10.1016/j.jcrs.2004.11.052.
    1. Piñero D.P., Sánchez-Pérez P.J., Alió J.L. Repeatability of measurements obtained with a ray tracing aberrometer. Optom. Vis. Sci. 2011;88:1099–1105. doi: 10.1097/OPX.0b013e3182223788.
    1. Belin M.W., Litoff D., Strods S.J., Winn S.S., Smith R.S. The PAR technology corneal topography system. Refract. Corneal Surg. 1992;8:88–96. doi: 10.3928/1081-597X-19920101-18.
    1. Belin M.W., Zloty P. Accuracy of the PAR corneal topography system with spatial misalignment. CLAO J. 1993;19:64–68. doi: 10.1097/00140068-199301000-00012.
    1. Jindal P., Cheung S., Pirouzian A., Keates R.H., Ren Q. Evaluation of the PAR corneal topography system. Ophthalmic Technol. V. 1995;2393:10–16.
    1. Vos F.M., van der Heijde G.L., Spoelder H.J.W., van Stokkum I.H.M., Groen F.C.A. A new instrument to measure the shape of the cornea based on pseudorandom color coding. IEEE Trans. Instrum. Meas. 1997;46:794–797. doi: 10.1109/19.650775.
    1. Klijn S., Reus N.J., Sicam V.A.D.P. Evaluation of keratometry with a novel color-LED corneal topographer. J. Refract. Surg. 2015;31:249–256. doi: 10.3928/1081597X-20150212-01.
    1. Sicam V.A.D.P., van der Heijde R.G.L. Topographer Reconstruction of the Nonrotation-Symmetric Anterior Corneal Surface Features. Optom. Vis. Sci. 2006;83:910–918. doi: 10.1097/01.opx.0000250018.82043.a6.
    1. Kanellopoulos A.J., Asimellis G. Clinical correlation between placido, scheimpflug and LED color reflection topographies in imaging of a scarred cornea. Case Rep. Ophthalmol. 2014;5:311–317. doi: 10.1159/000365962.
    1. Kanellopoulos A.J., Asimellis G. Forme fruste keratoconus imaging and validation via novel multi-spot reflection topography. Case Rep. Ophthalmol. 2013;4:199–209. doi: 10.1159/000356123.
    1. Molina-Martín A., Piñero D.P., Caballero M.T., de Fez D., Camps V.J. Comparative analysis of anterior corneal curvature and astigmatism measurements obtained with three different devices. Clin. Exp. Optom. 2020;103:618–624. doi: 10.1111/cxo.13002.
    1. Hidalgo I.R., Rozema J.J., Dhubhghaill S.N., Zakaria N., Koppen C., Tassignon M.-J. Repeatability and inter-device agreement for three different methods of keratometry: Placido, scheimpflug, and color LED corneal topography. J. Refract. Surg. 2015;31:176–181. doi: 10.3928/1081597X-20150224-01.
    1. Ferreira T., Ribeiro F. Comparability and repeatability of different methods of corneal astigmatism assessment. Clin. Ophthalmol. 2017;12:29–34. doi: 10.2147/OPTH.S146730.
    1. Ferreira T.B., Ribeiro F.J. A novel color-led corneal topographer to assess astigmatism in pseudophakic eyes. Clin. Ophthalmol. 2016;10:1521–1529. doi: 10.2147/OPTH.S113027.
    1. Klijn S., Reus N.J., van der Sommen C.M., Sicam V.A.D.P. Accuracy of total corneal astigmatism measurements with a scheimpflug imager and a color light-emitting diode corneal topographer. Am. J. Ophthalmol. 2016;167:72–78. doi: 10.1016/j.ajo.2016.04.011.
    1. Piñero D.P., Camps V.J., de Fez D., García C., Caballero M.T. Validation of posterior corneal curvature measurements with color light-emitting diode topography. Eur. J. Ophthalmol. 2020;30:1261–1267. doi: 10.1177/1120672119870738.
    1. García-García Á., Melián R., Carreras H., Rodríguez-Hernández V., Reñones J., Estévez B. Corneal dioptric power and astigmatism: A comparison between colour light-emitting diode based (cassini) and scheimpgflug technology (pentacam) topography. Arch. Soc. Esp. Oftalmol. 2019;94:273–280. doi: 10.1016/j.oftal.2018.11.014.
    1. Cui X.-H., Yoo Y.-S., An Y., Joo C.-K. Comparison of keratometric measurements between color light-emitting diode topography and scheimpflug camera. BMC Ophthalmol. 2019;19:98. doi: 10.1186/s12886-019-1106-1.
    1. Piñero D.P., Molina-Martín A., Camps V.J., de Fez D., Caballero M.T. Validation of corneal topographic and aberrometric measurements obtained by color light-emitting diode reflection topography in healthy eyes. Graefes Arch. Clin. Exp. Ophthalmol. 2019;257:2437–2447. doi: 10.1007/s00417-019-04453-5.
    1. Auffarth G.U., Wang L., Völcker H.E. Keratoconus evaluation using the orbscan topography system. J. Cataract Refract. Surg. 2000;26:222–228. doi: 10.1016/S0886-3350(99)00355-7.
    1. Ambrósio R., Jr., Valbon B.F., Faria-Correia F., Ramos I., Luz A. Scheimpflug imaging for laser refractive surgery. Curr. Opin. Ophthalmol. 2013;24:310–320. doi: 10.1097/ICU.0b013e3283622a94.
    1. Faria-Correia F., Ambrósio Júnior R. Clinical applications of the scheimpflug principle in ophthalmology. Rev. Bras. Oftalmol. 2016;75:160–165. doi: 10.5935/0034-7280.20160035.
    1. Rabsilber T.M., Khoramnia R., Auffarth G.U. Anterior chamber measurements using pentacam rotating scheimpflug camera. J. Cataract Refract. Surg. 2006;32:456–459. doi: 10.1016/j.jcrs.2005.12.103.
    1. Łabuz G., Varadi D., Khoramnia R., Auffarth G.U. Central and mid-peripheral corneal astigmatism in an elderly population: A retrospective analysis of scheimpflug topography results. Sci. Rep. 2021;11:7968. doi: 10.1038/s41598-021-81772-w.
    1. Grzybowski A., Kanclerz P. Clarifying the methods of fixation of intraocular lenses. Clin. Anat. 2018;31:2–3. doi: 10.1002/ca.22950.
    1. Grzybowski A., Kanclerz P. Population-based analysis of intraocular lens exchange and repositioning. J. Cataract. Refract. Surg. 2017;43:1484. doi: 10.1016/j.jcrs.2017.09.020.
    1. Gaurisankar Z.S., van Rijn G.A., Luyten G.P.M., Beenakker J.-W.M. Differences between scheimpflug and optical coherence tomography in determining safety distances in eyes with an iris-fixating phakic intraocular lens. Graefes Arch. Clin. Exp. Ophthalmol. 2021;259:231–238. doi: 10.1007/s00417-020-04874-7.
    1. Khalifa Y.M., Goldsmith J., Moshirfar M. Bilateral explantation of visian implantable collamer lenses secondary to bilateral acute angle closure resulting from a non-pupillary block mechanism. J. Refract. Surg. 2010;26:991–994. doi: 10.3928/1081597X-20100521-01.
    1. Yildirim T.M., Khoramnia R., Son H.-S., Mayer C.S., Łabuz G., Munro D.J., Auffarth G.U. Reasons for explantation of phakic intraocular lenses and associated perioperative complications: Cross-sectional explant registry analysis. BMC Ophthalmol. 2021;21:80. doi: 10.1186/s12886-021-01847-0.
    1. Gonvers M., Bornet C., Othenin-Girard P. Implantable contact lens for moderate to high myopia. J. Cataract Refract. Surg. 2003;29:918–924. doi: 10.1016/S0886-3350(03)00065-8.
    1. Winkler von Mohrenfels C., Salgado J.P., Khoramnia R. Keratectasia after refractive surgery. Klin. Monbl. Augenheilkd. 2011;228:704–711. doi: 10.1055/s-0029-1245754.
    1. LaHood B.R., Goggin M. Measurement of posterior corneal astigmatism by the IOLMaster 700. J. Refract. Surg. 2018;34:331–336. doi: 10.3928/1081597X-20180214-02.
    1. Rydström E., Westin O., Koskela T., Behndig A. Posterior corneal astigmatism in refractive lens exchange surgery. Acta Ophthalmol. 2016;94:295–300. doi: 10.1111/aos.12965.
    1. Lawless M., Hodge C., Sutton G., Barrett G. Total keratometry in intraocular lens power calculations in eyes with previous laser refractive surgery: Response. Clin. Exp. Ophthalmol. 2021;49:88–89. doi: 10.1111/ceo.13891.
    1. Lawless M., Jiang J.Y., Hodge C., Sutton G., Roberts T.V., Barrett G. Total keratometry in intraocular lens power calculations in eyes with previous laser refractive surgery. Clin. Exp. Ophthalmol. 2020;48:749–756. doi: 10.1111/ceo.13760.
    1. Fabian E., Wehner W. Prediction accuracy of total keratometry compared to standard keratometry using different intraocular lens power formulas. J. Refract. Surg. 2019;35:362–368. doi: 10.3928/1081597X-20190422-02.
    1. Jędzierowska M., Koprowski R., Wilczyński S., Krysik K. A new method for detecting the outer corneal contour in images from an ultra-fast scheimpflug camera. Biomed. Eng. Online. 2019;18:115. doi: 10.1186/s12938-019-0735-1.
    1. Leão E., Ing Ren T., Lyra J.M., Machado A., Koprowski R., Lopes B., Vinciguerra R., Vinciguerra P., Roberts C.J., Elsheikh A., et al. Corneal deformation amplitude analysis for keratoconus detection through compensation for intraocular pressure and integration with horizontal thickness profile. Comput. Biol. Med. 2019;109:263–271. doi: 10.1016/j.compbiomed.2019.04.019.
    1. Wojtkowski M., Srinivasan V., Fujimoto J.G., Ko T., Schuman J.S., Kowalczyk A., Duker J.S. Three-dimensional retinal imaging with high-speed ultrahigh-resolution optical coherence tomography. Ophthalmology. 2005;112:1734–1746. doi: 10.1016/j.ophtha.2005.05.023.
    1. Kanclerz P., Hoffer K.J., Rozema J.J., Przewłócka K., Savini G. Repeatability and reproducibility of optical biometry implemented in a new optical coherence tomographer and comparison with a optical low-coherence reflectometer. J. Cataract Refract. Surg. 2019;45:1619–1624. doi: 10.1016/j.jcrs.2019.07.002.
    1. Kanclerz P., Hoffer K.J., Przewłócka K., Savini G. Comparison of an upgraded optical biometer with 2 validated optical biometers. J. Cataract Refract. Surg. 2021;47:859–864.
    1. Wang C., Xia X., Tian B., Zhou S. Comparison of fourier-domain and time-domain optical coherence tomography in the measurement of thinnest corneal thickness in keratoconus. J. Ophthalmol. 2015;2015:402925. doi: 10.1155/2015/402925.
    1. Kanclerz P. Optical biometry in a commercially available anterior and posterior segment optical coherence tomography device. Clin. Exp. Optom. 2019;102:533–534. doi: 10.1111/cxo.12880.
    1. Xu B.Y., Mai D.D., Penteado R.C., Saunders L., Weinreb R.N. Reproducibility and agreement of anterior segment parameter measurements obtained using the CASIA2 and spectralis OCT2 optical coherence tomography devices. J. Glaucoma. 2017;26:974–979. doi: 10.1097/IJG.0000000000000788.
    1. Chen S., Gao R., McAlinden C., Ye J., Wang Y., Chen M., Huang J., Sun Y., Yu A.-Y. Comparison of anterior ocular biometric measurements using swept-source and time-domain optical coherence tomography. J. Ophthalmol. 2020;2020:9739878. doi: 10.1155/2020/9739878.
    1. Porporato N., Baskaran M., Tun T.A., Sultana R., Tan M., Quah J.H., Allen J.C., Perera S., Friedman D.S., Cheng C.Y., et al. Understanding diagnostic disagreement in angle closure assessment between anterior segment optical coherence tomography and gonioscopy. Br. J. Ophthalmol. 2020;104:795–799. doi: 10.1136/bjophthalmol-2019-314672.
    1. Ortiz S., Siedlecki D., Remon L., Marcos S. Optical coherence tomography for quantitative surface topography. Appl. Opt. 2009;48:6708–6715. doi: 10.1364/AO.48.006708.
    1. Karnowski K., Kaluzny B.J., Szkulmowski M., Gora M., Wojtkowski M. Corneal topography with high-speed swept source OCT in clinical examination. Biomed. Opt. Express. 2011;2:2709–2720. doi: 10.1364/BOE.2.002709.
    1. Kim J.S., Rho C.R., Cho Y.W., Shin J. Comparison of corneal thickness measurements using ultrasound pachymetry, noncontact tonopachy, pentacam HR, and fourier-domain OCT. Medicine. 2021;100:e25638. doi: 10.1097/MD.0000000000025638.
    1. Reinstein D.Z., Yap T.E., Archer T.J., Gobbe M., Silverman R.H. Comparison of corneal epithelial thickness measurement between fourier-domain OCT and very high-frequency digital ultrasound. J. Refract. Surg. 2015;31:438–445. doi: 10.3928/1081597X-20150623-01.
    1. Srivannaboon S., Chotikavanich S., Chirapapaisan C., Kasemson S., Po-ngam W. Precision analysis of posterior corneal topography measured by visante omni: Repeatability, reproducibility, and agreement with orbscan II. J. Refract. Surg. 2012;28:133–138. doi: 10.3928/1081597X-20111122-03.
    1. Gjerdrum B., Gundersen K.G., Lundmark P.O., Aakre B.M. Repeatability of OCT-based versus scheimpflug- and reflection-based keratometry in patients with hyperosmolar and normal tear film. Clin. Ophthalmol. 2020;14:3991–4003. doi: 10.2147/OPTH.S280868.
    1. Szalai E., Berta A., Hassan Z., Módis L., Jr. Reliability and repeatability of swept-source fourier-domain optical coherence tomography and scheimpflug imaging in keratoconus. J. Cataract Refract. Surg. 2012;38:485–494. doi: 10.1016/j.jcrs.2011.10.027.
    1. Savini G., Schiano-Lomoriello D., Hoffer K.J. Repeatability of automatic measurements by a new anterior segment optical coherence tomographer combined with placido topography and agreement with 2 scheimpflug cameras. J. Cataract Refract. Surg. 2018;44:471–478. doi: 10.1016/j.jcrs.2018.02.015.
    1. Li Y., Chamberlain W., Tan O., Brass R., Weiss J.L., Huang D. Subclinical keratoconus detection by pattern analysis of corneal and epithelial thickness maps with optical coherence tomography. J. Cataract Refract. Surg. 2016;42:284–295. doi: 10.1016/j.jcrs.2015.09.021.
    1. Kawamorita T., Uozato H., Kamiya K., Bax L., Tsutsui K., Aizawa D., Shimizu K. Repeatability, reproducibility, and agreement characteristics of rotating scheimpflug photography and scanning-slit corneal topography for corneal power measurement. J. Cataract Refract. Surg. 2009;35:127–133. doi: 10.1016/j.jcrs.2008.10.019.
    1. Corneal Topography—EyeWiki. [(accessed on 9 June 2021)]; Available online: .
    1. Wylęgała A., Mazur R., Bolek B., Wylęgała E. Reproducibility, and repeatability of corneal topography measured by Revo NX, Galilei G6 and Casia 2 in normal eyes. PLoS ONE. 2020;15:e0230589. doi: 10.1371/journal.pone.0230589.
    1. Molero-Senosiain M., Morales-Fernandez L., Saenz-Frances F., Perucho-Gonzalez L., García-Bella J., Garcia Feijoo J., Martinez-de-la-Casa J.M. Corneal properties in primary open-angle glaucoma assessed through scheimpflug corneal topography and densitometry. J. Glaucoma. 2021;30:444–450. doi: 10.1097/IJG.0000000000001770.
    1. Değirmenci C., Palamar M., İsmayilova N., Eğrilmez S., Yağcı A. Topographic evaluation of unilateral keratoconus patients. Turk. J. Ophthalmol. 2019;49:117–122. doi: 10.4274/tjo.galenos.2018.90958.
    1. de Luis Eguileor B., Arriola-Villalobos P., Pijoan Zubizarreta J.I., Feijoo Lera R., Santamaria Carro A., Diaz-Valle D., Etxebarria J. Multicentre study: Reliability and repeatability of scheimpflug system measurement in keratoconus. Br. J. Ophthalmol. 2021;105:22–26. doi: 10.1136/bjophthalmol-2019-314954.
    1. Martin R. Cornea and anterior eye assessment with placido-disc keratoscopy, slit scanning evaluation topography and scheimpflug imaging tomography. Indian J. Ophthalmol. 2018;66:360–366.
    1. Wegener A., Laser-Junga H. Photography of the anterior eye segment according to scheimpflug’s principle: Options and limitations—A review. Clin. Exp. Ophthalmol. 2009;37:144–154. doi: 10.1111/j.1442-9071.2009.02018.x.
    1. Boscia F., La Tegola M.G., Alessio G., Sborgia C. Accuracy of orbscan optical pachymetry in corneas with haze. J. Cataract Refract. Surg. 2002;28:253–258. doi: 10.1016/S0886-3350(01)01162-2.
    1. Ha B.J., Kim S.W., Kim S.W., Kim E.K., Kim T.-I. Pentacam and orbscan II measurements of posterior corneal elevation before and after photorefractive keratectomy. J. Refract. Surg. 2009;25:290–295.
    1. Rio-Cristobal A., Martin R. Corneal assessment technologies: Current status. Surv. Ophthalmol. 2014;59:599–614. doi: 10.1016/j.survophthal.2014.05.001.
    1. Aptel F., Chiquet C., Beccat S., Denis P. Biometric evaluation of anterior chamber changes after physiologic pupil dilation using pentacam and anterior segment optical coherence tomography. Investig. Ophthalmol. Vis. Sci. 2012;53:4005–4010. doi: 10.1167/iovs.11-9387.
    1. Jones L.W., Srinivasan S., Ng A., Schulze M. Contact Lens Practice. Elsevier; Amsterdam, The Netherlands: 2018. Diagnostic instruments; pp. 327–345.

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