Corneal pachymetry in normal and keratoconic eyes

Gherghel, Doina; Hosking, SL; Mantry, Sanjay; Banerjee, Samik; Naroo, Shehzad A.; Shah, Sunil

doi:10.1016/j.jcrs.2003.11.049

Cited by 85 publications

(55 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A second regression analysis (or analysis of residuals from a differences analysis) really needs to be routinely undertaken to quantify any bias (or demonstrate the lack of it), although this is actually rarely reported for comparisons between ophthalmic instruments. For example, just the Bland-Altman plot may be presented, even when the plots suggest a systematic bias [20], and a regression analysis on the difference between the two pachymeters would have been useful. An erroneous conclusion might be drawn that just because the 95% limits of agreement (±1.96 SD about the mean difference) have a narrow range (as in the present example, where the LoA is 0.038 to 0.096 mm, or a range for this of just 0.029 mm), then agreement between the two instruments is acceptable.…”

Section: Discussionmentioning

confidence: 99%

Effect of central corneal thickness on Goldmann applanation tonometry measures—a different result with different pachymeters

Doughty

Jonuscheit

2007

Graefes Arch Clin Exp Ophthalmol

View full text Add to dashboard Cite

show abstract

Section: Discussionmentioning

confidence: 99%

Effect of central corneal thickness on Goldmann applanation tonometry measures—a different result with different pachymeters

Doughty

Jonuscheit

2007

Graefes Arch Clin Exp Ophthalmol

View full text Add to dashboard Cite

show abstract

“…In these situations, scattering from corneal haze and stromal interfaces interferes with the identification of the corneal surface reflections due to the limited resolution of slit scanning. [21][22][23] The main drawback of ultrasound imaging is the inconvenient requirement of immersing the eye in a coupling fluid. Thus, a better method of pachymetric mapping is still needed.…”

mentioning

confidence: 99%

Corneal Pachymetry Mapping with High-speed Optical Coherence Tomography

2006

View full text Add to dashboard Cite

Objective-To map corneal thickness before and after LASIK with optical coherence tomography (OCT).Design-Cross-sectional observational study. Participants-Forty-two eyes of 21 normal subjects undergoing LASIK.Methods-A high-speed (2000 axial scans/second) 1.3-μm-wavelength corneal and anterior segment OCT prototype was used for corneal scanning. The scan pattern consisted of 10-mm radial lines on 8 meridians centered on the vertex reflection. The entire scan pattern of 1024 a-scans was acquired in 0.5 seconds. We developed automated computer processing for 3-dimensional corneal reconstruction and measurement. Corneal thickness was measured normal to the anterior surface and presented as color pachymetry maps and zonal statistics. The maps were divided into a central zone (<2 mm) and 3 annular areas (pericentral, 2-5 mm; transitional, 5-7 mm; peripheral, 7-10 mm), which were further divided into quadrantal zones. The average, minimum, and maximum corneal thicknesses were computed for zones within the 7-mm diameter. Optical coherence tomography and ultrasound pachymetry were measured 3 times at the preoperative and 3-month postoperative visits. Reproducibility was assessed by the pooled standard deviations (SDs) of the repeated measurements.Main Outcome Measures-Optical coherence tomography pachymetric map and zonal statistic, and ultrasound pachymetry.Results-Before LASIK, central corneal thicknesses (CCTs) were 546.9±29.4 μm (mean ± SD) for OCT and 553.3±33.0 μm for ultrasound. After LASIK, CCTs were 513.7±44.5 μm for OCT and 498±46.6 μm for ultrasound. Optical coherence tomography and ultrasound CCT were highly correlated (Pearson correlation r = 0.97 before LASIK and 0.98 afterwards). Optical coherence tomography CCT was slightly less than ultrasound CCT before surgery (mean difference, −6.4 μm; 95% limits of agreement, −23.2 to 10.4 μm) but slightly greater after LASIK (15.7 μm; −1.6 to 33 μm). These differences were statistically significant, but no more than the CCT measurement differences between ultrasound pachymeters. The reproducibility of the OCT zonal pachymetry averages was roughly 2 μm.Conclusions-High-speed OCT provided noncontact, rapid, reproducible pachymetric mapping over a wide area of the cornea. It is equivalent to ultrasound for CCT measurement before and after Correspondence and reprint requests to

show abstract

“…Corneal thickness has been proposed to be a useful parameter for the clinical identification of keratoconus. 36,37 Studies using ultrasound 38,39 or slit-scanning technologies40 have found that the difference (or ratio) between the peripheral and the thinnest (or central) corneal thickness was significantly greater in eyes with keratoconus than in normal eyes. Corneal thickness measurements have some disadvantages.…”

Section: Discussionmentioning

confidence: 99%

Keratokonus ve Subklinik Keratokonusun Tespit Edilmesi için Pentacamla Korneal Hacim Ölçümleri

Çağıl¹,

Uğurlu²,

Çakmak³

et al. 2013

Tjo

View full text Add to dashboard Cite

Sum maryPur po se: To estimate the sensitivity and specificity of corneal volume (CV) measurements in discriminating keratoconus and subclinical keratoconus from normal corneas. Ma te ri al and Met hod: Clinical records and Pentacam measurements of ninety-four patients with keratoconus, 36 patients with subclinical keratoconus, and 166 refractive surgery candidates with normal corneas were evaluated retrospectively. CV within 3, 5, 7, and 10 mm circles around the central cornea was measured in one eye of each patient, using the Pentacam. CV measurements in keratoconus and subclinical keratoconus were compared with normal corneas. Receiver operating characteristic (ROC) curves were used to determine the test's overall predictive accuracy and to identify optimal CV cutoff points to maximize sensitivity and specificity in discriminating keratoconus and subclinical keratoconus from normal corneas. Re sults: Mean CV within a 3.0 mm circle around the central cornea was statistically lower in keratoconus (3.4±0.2 mm 3 , p<0.001) and subclinical keratoconus (3.6±0.2mm 3 , p<0.001) versus normal corneas (3.8±0.3mm 3 ). ROC curve analysis showed high overall predictive accuracy of CV for keratoconus (area under the curve 0.92). Optimal cutoff points were 3.55 mm 3 for keratoconus and 3.65 mm 3 for subclinical keratoconus. These values provided sensitivity and specificity of 83% and 86%, respectively, for keratoconus, and 61% and 74% for subclinical keratoconus. Dis cus si on: CV within a 3.0 mm circle around the central cornea effectively discriminates keratoconus from normal corneas. However, its sensitivity and specificity are lower for subclinical keratoconus diagnosis. (Turk J Ophthalmol 2013; 43: 77-82) Key Words: Corneal volume, keratoconus, pentacam, subclinical keratoconus Özet Amaç: Kornea hacmi (KH) ölçümlerinin keratokonus ve subklinik keratokonusu normal kornealardan ayırt etmedeki duyarlılık ve özgünlüğünün tespit edilmesi. Ge reç ve Yön tem: Doksan dört keratokonus hastası, 36 subklinik keratokonuslu hasta ve 166 refraktif cerrahi adayının klinik kayıtları ve Pentacam ölçümleri retrospektif olarak incelendi. Pentacam kullanarak her hastanın santral kornea etrafındaki 3, 5, 7 ve 10 mm lik dairelerdeki KH'sı ölçüldü. Keratokonus ve subklinik keratokonustaki KH ölçümleri normal kornealarla karşılaştırıldı. Testin tüm tahmini doğruluğunu test etmek ve keratokonus ve subklinik keratokonusu normal kornealardan ayırt etmekte duyarlılık ve özgünlüğü maksimuma çıkaran optimal kesim noktalarının tanımlamak için ROC (Receiver operating characteristic) eğrileri kullanıldı. Sonuçlar: Santral kornea etrafındaki 3,0 mm'lik dairedeki KH; keratokonusta (3,4±0,2mm 3 , p<0,001) ve subklinik keratokonusta (3,6±0,2mm 3 , p<0,001) normal kornealara gore (3,8±0,3 mm 3 ) istatistiksel olarak düşüktü. ROC eğrisi analizi KH'nın keratokonus için yüksek toplam tahmini doğruluğunu gösterdi ( eğri altında kalan alan 0,92). Optimal kesim noktaları keratokonus için 3,55 mm 3 , subklinik keratokonus için ise 3,65 mm 3 idi. Bu değerler, kera...

show abstract

Corneal pachymetry in normal and keratoconic eyes

Abstract: This study suggests that OII and US pachymetry provide similar readings for CCT in normal subjects when an LCF is used. In keratoconus patients, OII provides a valid clinical tool for the noninvasive assessment of CCT when the LCF is not applied.

Cited by 85 publications

References 19 publications

Effect of central corneal thickness on Goldmann applanation tonometry measures—a different result with different pachymeters

Effect of central corneal thickness on Goldmann applanation tonometry measures—a different result with different pachymeters

Corneal Pachymetry Mapping with High-speed Optical Coherence Tomography

Keratokonus ve Subklinik Keratokonusun Tespit Edilmesi için Pentacamla Korneal Hacim Ölçümleri

Contact Info

Product

Resources

About