An Intraocular Lens Power Calculation Formula Based on Optical Coherence Tomography: A Pilot Study

Department of Ophthalmology, University of California, Los Angeles, Los Ángeles, California, United States
Journal of refractive surgery (Thorofare, N.J.: 1995) (Impact Factor: 3.47). 06/2010; 26(6):430-7. DOI: 10.3928/1081597X-20090710-02
Source: PubMed


To develop an intraocular lens (IOL) power calculation formula based on optical coherence tomography (OCT) that would not be biased by previous laser vision correction.
Twenty-seven eyes of 27 cataract patients without prior laser vision correction who underwent phacoemulsification were included in the study. An optical coherence biometer (IOLMaster, Carl Zeiss Meditec) measured anterior corneal curvature and axial eye length. A high-speed (2000 Hz) anterior segment OCT prototype mapped corneal thickness and measured anterior chamber depth and crystalline lens thickness. Posterior corneal curvature was computed by combining IOLMaster keratometry with OCT corneal thickness mapping. A new IOL formula was developed based on these parameters. One month after phacoemulsification, the manifest refraction spherical equivalent (MRSE) was measured. The prediction error in postoperative MRSE of the OCT-based IOL formula was compared with that of three theoretic formulae: SRK/T, Hoffer Q, and Holladay II.
The mean prediction error in postoperative MRSE of the OCT-based formula was 0.04+/-0.44 diopters (D). The SRK/T was the best of the theoretic formulae, and its prediction error was -0.35+/-0.42 D. Twenty-one (78%) eyes were within 0.50 D using the OCT formula compared to 18 (67%) eyes using the SRK/T. No statistically significant differences were noted among the formulae.
For cataract patients without prior laser vision correction, the OCT-based IOL formula was as accurate as the current theoretic formulae. This new formula is based on direct OCT assessment of the posterior curvature and avoids the calculation errors inherent in conventional IOL formulae.

Download full-text


Available from: David Huang, Aug 17, 2015
  • Source
    • "Corneal power is typically measured using keratometry, Placido-based videokeratography, slit-lamp scanning or Scheimpflug imaging [11]. However, the traditional lack of measurements of the posterior corneal surface has led to approximations (i.e., keratometric index) [5], which do not hold in abnormal corneas [12]. In addition, non-paraxial ray tracing approaches would require complete corneal shape information beyond corneal power. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In vivo three-dimensional (3-D) anterior segment biometry before and after cataract surgery was analyzed by using custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT). The system was provided with custom algorithms for denoising, segmentation, full distortion correction (fan and optical) and merging of the anterior segment volumes (cornea, iris, and crystalline lens or IOL), to provide fully quantitative data of the anterior segment of the eye. The method was tested on an in vitro artificial eye with known surfaces geometry at different orientations and demonstrated on an aging cataract patient in vivo. Biometric parameters CCT, ACD/ILP, CLT/ILT Tilt and decentration are retrieved with a very high degree of accuracy. IOL was placed 400 μm behind the natural crystalline lens, The IOL was aligned with a similar orientation of the natural lens (2.47 deg superiorly), but slightly lower amounts (0.77 deg superiorly). The IOL was decentered superiorly (0.39 mm) and nasally (0.26 mm).
    Full-text · Article · Mar 2013 · Biomedical Optics Express
  • Source
    • "OCT of the anterior segment is valuable for diagnosis of corneal disorders such as keratoconus, and for pre- and post-operative assessment during surgical procedures such as keratomileusis (LASIK), phototherapeutic keratectomy (PTK), astigmatic keratotomy and lamellar keratoplasty [7]. Contact lens fitting and intraocular lens (IOL) power calculation can be performed using volumetric OCT data [8,9]. In addition, OCT is used in anterior chamber angle evaluation for glaucoma diagnosis and management [10]. "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Nov 2012 · Biomedical Optics Express
  • [Show abstract] [Hide abstract]
    ABSTRACT: A full-wave zero-voltage switching quasiresonant converter flyback converter with a novel multiloop control was built which operates over the range of input voltage and load of a typical distributed-system power supply. The maximum converter frequency of 880 kHz is shown to be close to the practical limit for this specific application. Reasonable full-load efficiency is achieved, and the predicted losses agree with actual circuit measurements. The multiloop control scheme provides noise-immune and stable control over the full operating range of the converter. Design guidelines for the control are given, and it is shown theoretical and measured small-signal performance are in agreement. Performance and stress predictions are also very close to measurements
    No preview · Conference Paper · Mar 1988
Show more