Astigmatic Vector Analysis of Posterior Cornea - a Comparison Among Healthy, Forme Fruste and Overt Keratoconus Corneas

Keratoconus Clinical Trial

Official title:

Astigmatic Vector Analysis of Posterior Corneal Surface - a Comparison Among Healthy, Forme Fruste and Overt Keratoconus Corneas

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT02698709
• Other study ID #: Clínica Oftalmológica HCFM/USP
• Status: Completed
• Phase: N/A
• First received: February 24, 2016
• Last updated: February 29, 2016
• Start date: May 2015
• Est. completion date: September 2015

Study information

• Verified date: February 2016
• Source: University of Sao Paulo
• Contact: n/a
• Is FDA regulated: No
• Health authority: Brazil: National Committee of Ethics in Research
• Study type: Observational

Clinical Trial Summary

The main purpose of this study is to determine new diagnostic criteria for an eye disease called keratoconus.

Description:

Eyes of patients who distinctly present signs of keratoconus, for both eyes, at corneal tomography (an exam commonly used in such cases), and those who present such signs in only one eye were compared to eyes of unaffected patients. Several characteristics of anterior and posterior corneal astigmatism (special emphasis was given to the latter) were collectively assessed among all patients by a method referred to as vectorial analysis. Statistical tests were then performed, in an attempt to highlight differences among those three groups of patients and, eventually, define new diagnostic criteria.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 698
• Est. completion date: September 2015
• Est. primary completion date: August 2015
• Accepts healthy volunteers: No
• Gender: Both
• Age group: N/A and older

Eligibility

Inclusion Criteria:

• Good-quality Scheimpflug scans (approved by the device in the ''Examination Quality Specification'').

Exclusion Criteria:

• Previous eye surgery or trauma, and any sort of corneal scarring that might interfere with keratometric data acquisition.

Study Design

Observational Model: Case Control, Time Perspective: Retrospective

Related Conditions & MeSH terms

• Keratoconus

Intervention

Other:
• Analysis of anterior and posterior corneal surfaces
Corneal data obtained from a Scheimpflug-based topographer were converted to astigmatic vectors in accordance to the method proposed by Thibos

Locations

Country	Name	City	State
Brazil	Clínica Oftalmológica do Hospital de Clínicas - FMUSP	São Paulo

Sponsors (1)

Lead Sponsor	Collaborator
University of Sao Paulo

Country where clinical trial is conducted

Brazil, 

References & Publications (30)

Alpins N, Ong JK, Stamatelatos G. Corneal topographic astigmatism (CorT) to quantify total corneal astigmatism. J Refract Surg. 2015 Mar;31(3):182-6. doi: 10.3928/1081597X-20150224-02. — View Citation

Ambrósio R Jr, Valbon BF, Faria-Correia F, Ramos I, Luz A. Scheimpflug imaging for laser refractive surgery. Curr Opin Ophthalmol. 2013 Jul;24(4):310-20. doi: 10.1097/ICU.0b013e3283622a94. Review. — View Citation

Baratloo A, Hosseini M, Negida A, El Ashal G. Part 1: Simple Definition and Calculation of Accuracy, Sensitivity and Specificity. Emerg (Tehran). 2015 Spring;3(2):48-9. — View Citation

Bühren J, Schäffeler T, Kohnen T. Validation of metrics for the detection of subclinical keratoconus in a new patient collective. J Cataract Refract Surg. 2014 Feb;40(2):259-68. doi: 10.1016/j.jcrs.2013.07.044. Epub 2013 Dec 18. — View Citation

Eom Y, Rhim JW, Kang SY, Kim SW, Song JS, Kim HM. Toric Intraocular Lens Calculations Using Ratio of Anterior to Posterior Corneal Cylinder Power. Am J Ophthalmol. 2015 Oct;160(4):717-24.e2. doi: 10.1016/j.ajo.2015.07.011. Epub 2015 Jul 26. — View Citation

Galletti JD, Ruiseñor Vázquez PR, Minguez N, Delrivo M, Bonthoux FF, Pförtner T, Galletti JG. Corneal asymmetry analysis by pentacam scheimpflug tomography for keratoconus diagnosis. J Refract Surg. 2015 Feb;31(2):116-23. doi: 10.3928/1081597X-20150122-07 — View Citation

Gilani F, Cortese M, Ambrósio RR Jr, Lopes B, Ramos I, Harvey EM, Belin MW. Comprehensive anterior segment normal values generated by rotating Scheimpflug tomography. J Cataract Refract Surg. 2013 Nov;39(11):1707-12. doi: 10.1016/j.jcrs.2013.05.042. Epub — View Citation

Goebels S, Eppig T, Wagenpfeil S, Cayless A, Seitz B, Langenbucher A. Staging of keratoconus indices regarding tomography, topography, and biomechanical measurements. Am J Ophthalmol. 2015 Apr;159(4):733-8. doi: 10.1016/j.ajo.2015.01.014. Epub 2015 Jan 26 — View Citation

Gomes JA, Tan D, Rapuano CJ, Belin MW, Ambrósio R Jr, Guell JL, Malecaze F, Nishida K, Sangwan VS; Group of Panelists for the Global Delphi Panel of Keratoconus and Ectatic Diseases. Global consensus on keratoconus and ectatic diseases. Cornea. 2015 Apr;3 — View Citation

Koch DD, Ali SF, Weikert MP, Shirayama M, Jenkins R, Wang L. Contribution of posterior corneal astigmatism to total corneal astigmatism. J Cataract Refract Surg. 2012 Dec;38(12):2080-7. doi: 10.1016/j.jcrs.2012.08.036. Epub 2012 Oct 12. — View Citation

Li X, Yang H, Rabinowitz YS. Keratoconus: classification scheme based on videokeratography and clinical signs. J Cataract Refract Surg. 2009 Sep;35(9):1597-603. doi: 10.1016/j.jcrs.2009.03.050. — View Citation

Lopes B, Ramos I, Ambrósio R Jr. Corneal densitometry in keratoconus. Cornea. 2014 Dec;33(12):1282-6. doi: 10.1097/ICO.0000000000000266. — View Citation

McGee S. Simplifying likelihood ratios. J Gen Intern Med. 2002 Aug;17(8):646-9. — View Citation

Montalbán R, Piñero DP, Javaloy J, Alio JL. Correlation of the corneal toricity between anterior and posterior corneal surfaces in the normal human eye. Cornea. 2013 Jun;32(6):791-8. doi: 10.1097/ICO.0b013e31827bf898. — View Citation

Montalbán R, Piñero DP, Javaloy J, Alió JL. Scheimpflug photography-based clinical characterization of the correlation of the corneal shape between the anterior and posterior corneal surfaces in the normal human eye. J Cataract Refract Surg. 2012 Nov;38(1 — View Citation

Moreira LB, Bardal RA, Crisigiovanni LR. Contact lenses fitting after intracorneal ring segments implantation in keratoconus. Arq Bras Oftalmol. 2013 Jul-Aug;76(4):215-7. — View Citation

Muftuoglu O, Ayar O, Ozulken K, Ozyol E, Akinci A. Posterior corneal elevation and back difference corneal elevation in diagnosing forme fruste keratoconus in the fellow eyes of unilateral keratoconus patients. J Cataract Refract Surg. 2013 Sep;39(9):1348 — View Citation

Piñero DP, Alio JL, Tomás J, Maldonado MJ, Teus MA, Barraquer RI. Vector analysis of evolutive corneal astigmatic changes in keratoconus. Invest Ophthalmol Vis Sci. 2011 Jun 8;52(7):4054-62. doi: 10.1167/iovs.10-6856. — View Citation

Qin B, Chen S, Brass R, Li Y, Tang M, Zhang X, Wang X, Wang Q, Huang D. Keratoconus diagnosis with optical coherence tomography–based pachymetric scoring system. J Cataract Refract Surg. 2013 Dec;39(12):1864-71. — View Citation

Raiskup F, Theuring A, Pillunat LE, Spoerl E. Corneal collagen crosslinking with riboflavin and ultraviolet-A light in progressive keratoconus: ten-year results. J Cataract Refract Surg. 2015 Jan;41(1):41-6. doi: 10.1016/j.jcrs.2014.09.033. — View Citation

Ramos IC, Correa R, Guerra FP, Trattler W, Belin MW, Klyce SD, Fontes BM, Schor P, Smolek MK, Dawson DG, Chalita MR, Cazal JO, Ruiz M, Randleman JB, Ambrósio R Jr. Variability of subjective classifications of corneal topography maps from LASIK candidates. — View Citation

Randleman JB, Akhtar J, Lynn MJ, Ambrósio R Jr, Dupps WJ Jr, Krueger RR, Klyce SD. Comparison of objective and subjective refractive surgery screening parameters between regular and high-resolution Scheimpflug imaging devices. J Cataract Refract Surg. 201 — View Citation

Read SA, Collins MJ. Diurnal variation of corneal shape and thickness. Optom Vis Sci. 2009 Mar;86(3):170-80. doi: 10.1097/OPX.0b013e3181981b7e. — View Citation

Ruiseñor Vázquez PR, Galletti JD, Minguez N, Delrivo M, Fuentes Bonthoux F, Pförtner T, Galletti JG. Pentacam Scheimpflug tomography findings in topographically normal patients and subclinical keratoconus cases. Am J Ophthalmol. 2014 Jul;158(1):32-40.e2. — View Citation

Saad A, Gatinel D. Topographic and tomographic properties of forme fruste keratoconus corneas. Invest Ophthalmol Vis Sci. 2010 Nov;51(11):5546-55. doi: 10.1167/iovs.10-5369. Epub 2010 Jun 16. — View Citation

Saunders LJ, Zhu H, Bunce C, Doré CJ, Freemantle N, Crabb DP; Ophthalmic Statistics Group. Ophthalmic statistics note 5: diagnostic tests—sensitivity and specificity. Br J Ophthalmol. 2015 Sep;99(9):1168-70. doi: 10.1136/bjophthalmol-2014-306055. Epub 201 — View Citation

Shi R, Conrad SA. Correlation and regression analysis. Ann Allergy Asthma Immunol. 2009 Oct;103(4 Suppl 1):S35-41. — View Citation

Smadja D, Santhiago MR, Mello GR, Krueger RR, Colin J, Touboul D. Influence of the reference surface shape for discriminating between normal corneas, subclinical keratoconus, and keratoconus. J Refract Surg. 2013 Apr;29(4):274-81. doi: 10.3928/1081597X-20 — View Citation

Thibos LN, Horner D. Power vector analysis of the optical outcome of refractive surgery. J Cataract Refract Surg. 2001 Jan;27(1):80-5. — View Citation

Torricelli AA, Bechara SJ, Wilson SE. Screening of refractive surgery candidates for LASIK and PRK. Cornea. 2014 Oct;33(10):1051-5. doi: 10.1097/ICO.0000000000000171. — View Citation

* Note: There are 30 references in all — Click here to view all references

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Astigmatism corneal vectors (based on keratometric readings at the three millimeter optical zones for both corneal surfaces).	Corneal tomography at an Scheimpflug-based tomographer	Through study completion, an average of 6 months.	No