Original article
Comparison of Three Methods of Measuring Corneal Thickness and Anterior Chamber Depth

https://doi.org/10.1016/j.ajo.2005.08.048Get rights and content

Purpose

To compare three different methods of measuring corneal thickness (CT) and anterior chamber depth (ACD).

Design

Prospective clinical trial (Medical University of Vienna, Austria).

Methods

Central CT (CCT), CT at four peripheral points, and central ACD were measured in 88 eyes of 44 healthy subjects with the Pentacam (rotating Scheimpflug camera; Oculus, Wetzlar, Germany), Orbscan I (scanning-slit topography system; Orbtek Inc, Salt Lake City, Utah, USA), and AC-Master (partial coherence interferometry; Zeiss Meditec, Jena, Germany), and the results were compared.

Results

The upper (lower) limits of agreement for CCT measurements were 7.9 (−22.2) μm between AC-Master and Pentacam, 17.6 (−32.5) μm between AC-Master and Orbscan, and 25.2 (−25.9) μm between Pentacam and Orbscan. Correlation was high between all three methods (r = 0.94 to 0.97). The upper and lower limits of agreement for ACD were 0.174 (−0.251) mm between AC-Master and Pentacam, 0.406 (−0.004) mm between AC-Master and Orbscan, and 0.384 (0.095) mm between Pentacam and Orbscan. Correlation was high between the three methods (r = 0.96 between Orbscan and Pentacam; others 0.92). Correlation was lower for the CT measurements at the four peripheral points.

Conclusions

The CCT and ACD values obtained by Pentacam, Orbscan, and AC-Master measurements correlated well and showed few outliers. The two new systems (Pentacam, AC-Master) provide a reliable, easy-to-use, noncontact method of measuring CCT and ACD. Larger differences occurred only when measuring peripheral CT values, especially between AC-Master and the other two methods.

Section snippets

Methods

Eighty-eight eyes of 44 young volunteers were included in this prospective study. The subjects had to be healthy except for myopia/hyperopia and/or astigmatic ametropia. Exclusion criteria were other ocular diseases such as glaucoma and retinal pathology, or any history of ocular surgery, including (refractive) laser surgery. The volunteers were informed about the purpose of the study and had to give informed consent before inclusion. The study was performed in adherence to the Declaration of

Results

The mean age of the 44 subjects was 23.6 years (range, 21–32 years). The mean spherical equivalent was −2.15 D (range, −8.5 to +3.0 D). 13. There were seven contact lens wearers who removed the lenses at least 12 hours before the study. Both eyes of all subjects (88 eyes) could be measured with the three instruments. Mean total examination time was 25 minutes per subject (approximately 15 minutes for Pentacam and Orbscan, and 10 minutes for the AC-Master measurements including scan evaluation).

Discussion

Accurate measurement of CT and ACD has become important with the rapidly increasing popularity of corneal refractive surgical procedures and with the implantation of new (phakic) intraocular lenses. In this study, we have compared three different noncontact optical methods of measuring CT and ACD. Two of these instruments, the AC-Master and the Pentacam, have been made commercially available only quite recently. The Orbscan is an already established method and was made commercially available

Reporting visual acuities

The AJO encourages authors to report the visual acuity in the manuscript using the same nomenclature that was used in gathering the data provided they were recorded in one of the methods listed here. This table of equivalent visual acuities is provided to the readers as an aid to interpret visual acuity findings in familiar units.

Table of Equivalent Visual Acuity Measurements

Snellen Visual AcuitiesEmpty CellEmpty Cell
4 Meters6 Meters20 FeetDecimal FractionLogMAR
4/406/6020/2000.10+1.0
4/326/4820/1600.125+0.9
4/256/38

Wolf BUEHL, MD

Department of Ophthalmology

Medical University of Vienna

Waehringer Guertel 18-20, Vienna 1090, Austria

[email protected]

phone: +43-1-40400-7944

Date of birth: 24.5.1974

2000: PhD Thesis (“Fully automated analysis of PCO”)

2000–2002: Research fellow in Ophthalmology, Medical University of Vienna

Since 2002: Clinical fellow in Ophthalmology, Medical University of Vienna

Primary research interests:

  • Cataract surgery

  • Intraocular lenses

  • Posterior capsule opacification (PCO)

  • Biometry

References (20)

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Wolf BUEHL, MD

Department of Ophthalmology

Medical University of Vienna

Waehringer Guertel 18-20, Vienna 1090, Austria

[email protected]

phone: +43-1-40400-7944

Date of birth: 24.5.1974

2000: PhD Thesis (“Fully automated analysis of PCO”)

2000–2002: Research fellow in Ophthalmology, Medical University of Vienna

Since 2002: Clinical fellow in Ophthalmology, Medical University of Vienna

Primary research interests:

  • Cataract surgery

  • Intraocular lenses

  • Posterior capsule opacification (PCO)

  • Biometry

  • Digital imaging of the anterior segment

1

W.D. is a consultant for Carl Zeiss Meditec (Jena, Germany).

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