Correlation of central and peripheral corneal thickness in healthy corneas
Introduction
Morphometric data on central corneal thickness (CCT) has assumed considerable clinical importance in relation to refractive [1] and non refractive corneal surgery and glaucoma [2], [3]. The depth of incisions and of ablations in refractive surgery and the thickness of the cut in lamellar corneal surgery, all require fairly precise measurement of corneal thickness. Some incisions are made at the mid-periphery (arcuate incisions) [4], at the periphery (limbal relaxing incisions) [5] or from the edge of the optical zone to the periphery as in radial keratotomy [6]. In manual preparation of donor material for the DSEK procedure the depth of the initial peripheral incision in the donor sclerocorneal disc can be estimated by the CCT. By implication, the CCT data is used as a surrogate for peripheral corneal thickness (PCT) in some instances.
Ultrasound pachymetry has been reported to give very accurate, clinically reliable and reproducible data [7], [8], but determination of the actual points to apply the probe is operator dependent and can lead to inaccuracies when mapping the corneal thickness. The advent of devices such as the Scheimpflug rotating camera (Pentacam; Oculus, Inc., Wetzlar, Germany), slit-scanning optical pachymetry (Orbscan; Bausch & Lomb, Rochester, New York, USA) and high speed optical coherence tomography (OCT; Carl Zeiss Meditec, Inc., CA, USA) has allowed accurate mapping of corneal thickness at multiple points on the cornea [9]. The Pentacam for example collects information from up to 25,000 data points [10]. Using such data we have been able to correlate CCT to the PCT and establish a comprehensive thickness profile of the normal cornea. This information is reported in this paper.
Section snippets
Methods
This prospective clinical study enrolled 67 eyes of 40 patients. Inclusion criteria were healthy corneas with a best corrected visual acuity of 6/6 or better. The following exclusion criteria were applied: amblyopia, previous history of ocular disease or trauma, previous ocular surgery including refractive surgery and contact lens wear. Thirteen eyes of 13 patients were thus excluded. The study was performed according to the Tenets of the Declaration of Helsinki. We certify that all applicable
Results
Of the 40 patients studied 24 were males (60%) and 16 were females (40%). The mean age was 38.65 years ± 14.58 (range 19–76 years). Keratometry readings (K) measured in dioptres (D) were as following: flat meridian (43.12 ± 1.43 D, range 40.3–47.4 D), steep meridian (44.18 ± 1.54 D, range 41.3–49.3 D) and average K (43.65 ± 1.44 D, range 41.1–48.4 D).
Discussion
Corneal thickness measurements are essential in the work up of patients for laser or incisional refractive surgery [1], assessment of glaucoma [14] and monitoring certain corneal diseases such as keratoconus [15], [16] and Fuchs endothelial dystrophy [17]. For all of the above indications, reliance is placed on measurement of the central corneal thickness by manual placement of the ultrasound probe. Clinically this has proven to be reasonable and reliable. Relatively newer instruments have
Conflict of interest
None of the authors have any financial or other conflict of interest.
References (30)
Ocular hypertension and central corneal thickness
Ophthalmology
(1995)- et al.
Standardized arcuate keratotomy for postkeratoplasty astigmatism
J Cataract Refract Surg
(2005) - et al.
Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach
Surv Ophthalmol
(2000) - et al.
Corneal thickness indices discriminate between keratoconus and contact lens-induced corneal thinning
Ophthalmology
(2002) - et al.
Corneal thickness measurements in normal and keratoconic eyes: Pentacam comprehensive eye scanner versus noncontact specular microscopy and ultrasound pachymetry
J Cataract Refract Surg
(2006) - et al.
Central and peripheral corneal thickness measured with optical coherence tomography, Scheimpflug imaging, and ultrasound pachymetry in normal, keratoconus-suspect, and post-laser in situ keratomileusis eyes
J Cataract Refract Surg
(2009) - et al.
Central corneal thickness measurements using Orbscan II, Visante, ultrasound, and Pentacam pachymetry after laser in situ keratomileusis for myopia
J Cataract Refract Surg
(2007) - et al.
Corneal-thickness spatial profile and corneal-volume distribution: tomographic indices to detect keratoconus
J Cataract Refract Surg
(2006) - et al.
Central and peripheral pachymetry measurements according to age using the Pentacam rotating Scheimpflug camera
J Cataract Refract Surg
(2007) - et al.
The relationship of central corneal thickness (CCT) to thinnest central cornea (TCC) in healthy adults
Cont Lens Anterior Eye
(2009)
Comparison of four corneal pachymetry techniques in corneal refractive surgery
J Refract Surg
The ocular hypertension treatment study: baseline factors that predict the onset of primary open-angle glaucoma
Arch Ophthalmol
[Para-limbic relaxing incisions for reduction of astigmatism within the scope of catarct surgery]
Klin Monbl Augenheilkd
Radial keratotomy for the purpose of reducing glasses power in high myopia
Korean J Ophthalmol
The repeatability of corneal thickness measures
Cornea
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