A new non-contact optical device for ocular biometry

Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Birmingham, UK.
British Journal of Ophthalmology (Impact Factor: 2.98). 05/2002; 86(4):458-62.
Source: PubMed


A new commercially available device (IOLMaster, Zeiss Instruments) provides high resolution non-contact measurements of axial length (using partial coherent interferometry), anterior chamber depth, and corneal radius (using image analysis). The study evaluates the validity and repeatability of these measurements and compares the findings with those obtained from instrumentation currently used in clinical practice.
Measurements were taken on 52 subjects (104 eyes) aged 18-40 years with a range of mean spherical refractive error from +7.0 D to -9.50 D. IOLMaster measurements of anterior chamber depth and axial length were compared with A-scan applanation ultrasonography (Storz Omega) and those for corneal radius with a Javal-Schiötz keratometer (Topcon) and an EyeSys corneal videokeratoscope.
Axial length: the difference between IOLMaster and ultrasound measures was insignificant (0.02 (SD 0.32) mm, p = 0.47) with no bias across the range sampled (22.40-27.99 mm). Anterior chamber depth: significantly shorter depths than ultrasound were found with the IOLMaster (-0.06 (0.25) mm, p <0.02) with no bias across the range sampled (2.85-4.40 mm). Corneal radius: IOLMaster measurements matched more closely those of the keratometer than those of the videokeratoscope (mean difference -0.03 v -0.06 mm respectively), but were more variable (95% confidence 0.13 v 0.07 mm). The repeatability of all the above IOLMaster biometric measures was found to be of a high order with no significant bias across the measurement ranges sampled.
The validity and repeatability of measurements provided by the IOLMaster will augment future studies in ocular biometry.

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Available from: Jacinto Santodomingo-Rubido, Jun 04, 2015
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    • "Therefore, evaluating the instruments that precisely measure anterior corneal curvature is clinically important. Currently, a number of instruments are available for assessing corneal status and measuring corneal curvature, including Scheimpflug topography, optical coherence tomography, optical lowcoherence reflectometry, partial coherence interferometry, and slit-scanning topography/pachymetry systems [1] [2] [3] [4] [5]. The Galilei Dual-Scheimpflug analyzer (Ziemer Group, Port, Switzerland) is a high-precision optical system for evaluating corneal topography; it is different from the Pentacam (Oculus), a Scheimpflug-based system that derives its surface keratometry readings from Scheimpflug images. "
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    ABSTRACT: Purpose. To compare anterior corneal keratometry (K) measurements taken by a dual Scheimpflug analyzer and an auto kerato-refractometer. Methods. Sixty-four normal eyes underwent keratometric measurements with both devices. The repeatability of the auto kerato-refractometer measurements was assessed by calculating the coefficient of variation (COV). The interdevice agreement was evaluated using the Bland-Altman analysis, Pearson correlation coefficient, and paired two-tailed t-test. Results. The COV of the flat K and steep K measurements taken by the auto kerato-refractometer were 0.21% and 0.29%, respectively. There were no significant differences between the steep K and average K measurements for the Topcon and Galilei devices (P = 0.475, and P = 0.137, resp.). The Galilei flat K values were lower than those of the Topcon (P = 0.002). Both of the instruments showed good agreement for all anterior corneal keratometric values. There was a significant linear correlation between the Galilei and Topcon devices for the flat K (r = 0.989, P < 0.0001), steep K (r = 0.987, P < 0.0001), and average K values (r = 0.994, P < 0.0001). Conclusions. The anterior corneal flat keratometric values were not interchangeable between the Galilei and Topcon devices. However, the measurements of the two instruments showed significant linear correlation with each other.
    Journal of Ophthalmology 05/2014; 2014(4):140628. DOI:10.1155/2014/140628 · 1.43 Impact Factor
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    • "Low-coherence interferometry is another technique which is used clinically for ocular biometry, the measurement of intraocular distances [11–13]. This technique is non-contact and allows measurement of the central depth profile of the eye, offering higher resolution than traditional ultrasound. "
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    ABSTRACT: We demonstrate swept source OCT utilizing vertical-cavity surface emitting laser (VCSEL) technology for in vivo high speed retinal, anterior segment and full eye imaging. The MEMS tunable VCSEL enables long coherence length, adjustable spectral sweep range and adjustable high sweeping rate (50-580 kHz axial scan rate). These features enable integration of multiple ophthalmic applications into one instrument. The operating modes of the device include: ultrahigh speed, high resolution retinal imaging (up to 580 kHz); high speed, long depth range anterior segment imaging (100 kHz) and ultralong range full eye imaging (50 kHz). High speed imaging enables wide-field retinal scanning, while increased light penetration at 1060 nm enables visualization of choroidal vasculature. Comprehensive volumetric data sets of the anterior segment from the cornea to posterior crystalline lens surface are also shown. The adjustable VCSEL sweep range and rate make it possible to achieve an extremely long imaging depth range of ~50 mm, and to demonstrate the first in vivo 3D OCT imaging spanning the entire eye for non-contact measurement of intraocular distances including axial eye length. Swept source OCT with VCSEL technology may be attractive for next generation integrated ophthalmic OCT instruments.
    Biomedical Optics Express 11/2012; 3(11):2733-51. DOI:10.1364/BOE.3.002733 · 3.65 Impact Factor
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    • "Corneal power was measured by automated keratometry, which was performed first because the system requires the input of corneal radii to calculate the anterior chamber depth. The ACD was determined by calculating the distance along the visual axis between the corneal epithelium and the lens using lateral slit illumination with high resolution, (±0.01 mm) [11], high precision(≤5 µm) and good reliability [12,13]. "
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    ABSTRACT: To compare the accuracy of intraocular lens (IOL) power calculation formulas in eyes with primary angle closure glaucoma (ACG). This retrospective study compared the refractive outcomes of 63 eyes with primary ACG with the results of 93 eyes with normal open angles undergoing uneventful cataract surgery. Anterior segment biometry including anterior chamber depth, axial length, and anterior chamber depth to axial length ratio were compared by the IOL Master. Third generation formulas (Hoffer Q and SRK/T) and a fourth generation formula (Haigis) were used to predict IOL powers in both groups. The predictive accuracy of the formulas was analyzed by comparison of the mean error and the mean absolute error (MAE). In ACG patients, anterior chamber depth and the anterior chamber depth to axial length ratio were smaller than normal controls (all p < 0.05). The MAEs from the ACG group were larger than that from the control group in the Haigis formula. The mean absolute error from the Haigis formula was the largest and the mean absolute error from the Hoffer Q formula was the smallest. IOL power prediction may be inaccurate in ACG patients. The Haigis formula produced more inaccurate results in ACG patients, and it is more appropriate to use the Hoffer Q formula to predict IOL powers in eyes with primary ACG.
    Korean Journal of Ophthalmology 12/2011; 25(6):375-9. DOI:10.3341/kjo.2011.25.6.375
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