A new digitised screen test for strabismus measurement.

Purpose: Our study presents a digitised tangent screen test for ocular motility analysis according to the Harms and Hess tests (measurement of the squint angle in all fields of vision). This test uses an image beamer to display the tangent screen, a position sensor to measure the patient's head orientation, and a distance sensor to measure the fixation distance. Digital measurement of head orientation allows for a test procedure that eliminates the conventional requirement for a light pointer in the patient's hand.

Extended measuring depth dual-wavelength Fourier domain optical coherence tomography.

In this work an enhanced wide range dual band spectral domain optical coherence tomography technique (SD-OCT) is presented to increase the depth and accuracy of the measurement of optical A-scan biometry. The setup uses a Michelson interferometer with two wide-spectrum Superluminescent Diodes (SLD). The emissions of the SLDs are filtered by a long-pass filter (900 nm) in front of the reference mirror.

Comparison of spherical and aspherical intraocular lenses with decentration and tilt error using a physical model of human contrast vision and an image quality metric.

Purpose: In this study, two intraocular lenses (spherical IOL SA60AT and aspherical IOL SN60WF) are examined in an eye model under conditions of misalignment (defocus, decentration and tilt). The lenses are rated using the contrast sensitivity function (CSF) based on Barten's physical model. The square root integral (SQRI) method is used as a quality criterion comparable to the subjective image quality assessment of the human eye.

New retinal tack designs: an analysis of retention forces in human scleral tissue.

Purpose: The study aimed to construct a new retinal tack design with high retention forces to prevent spontaneous disentanglement in cases of complicated retinal surgery.

Methods: Six new forms for the peak of a retinal tack were developed using computer-aided design (CAD); then a prototype was produced for each model. Finally, standardised design testing was conducted using human (ex vivo) sclera by logging 15 consecutive measurements for each model.

The Cosine Similarity Technique: A new method for smart EXCIMER laser control.

Purpose: To introduce additional steps towards smart laser control in eye surgery, with the use of the cosine similarity technique to analyze the spectra of organic polymers obtained using non-contact photoacoustic spectroscopy (NCPAS).

Methods: The experiments were performed with two organic polymers: polyethylene and polyamide. A 193 nm excimer laser was used for photoablation at a repetition rate of 200Hz.

A systematic comparison and evaluation of three different Swept-Source interferometers for eye lengths biometry.

This study reviews the development of Swept-Source interferometers and compares systematically three different Swept-Source interferometer designs for biometric measurements of the eye. Principles characteristics, conveniences and accessibilities of the three developed systems are presented. The main difference between the three Swept-Source systems is the method of tuning the wavelength at the broadband optical amplifier.

The anatomy of the foveola reinvestigated.

Objective: In the foveola of the eye, photoreceptors and Müller cells with a unique morphology have been described, but little is known about their 3D structure and orientation. Considering that there is an angle-dependent change in the foveolar photoreceptor response for the same light beam, known as the Stiles Crawford Effect of the first kind (SCE I), which is still not fully understood, a detailed analysis of the anatomy of the foveolar cells might help to clarify this phenomenon.

Methods: Serial semithin and ultrathin sections, and focused ion beam (FIB) tomography were prepared from 32 foveolae from monkeys () and humans.

TD-PCI system based on an angle modulation for in vivo measurements of the human eye.

In this study, a "time domain" system based on a partial coherence interferometry method is presented. The classic technique of varying the reference arm using a linear motor is replaced by the use of a rotating glass cube. The theoretical definition of the variation of the optical path length and first measurements in a human model eye and a real human eye are presented.

Length measurement of the eye using a swept-source interferometer.

In this article, a swept-source setup based on a semiconductor optical amplifier at the central wavelength of 1050 nm for measurements of the axial length inside the eye is presented. The large coherence length is achieved using a tunable optical filter, consisting of a reflective diffraction grating, two Littrow prisms, and a scanner. It was possible to achieve a coherence length of 40 mm, which allowed interference measurements in this range to be made.

Biometric measurements inside the model eye using a two wavelengths Fourier domain low coherence interferometer.

We present a setup to measure biometric data of the eye using Fourier domain interferometry. The measuring depth of a Fourier domain system is basically limited owing to the spectral resolution. Combining two spectral domain interferometers with different wavelength ranges creates two measurement sections and allows for a simultaneous biometric measurement in terms of corneal thickness, anterior chamber depth, and axial length.

Real ray tracing simulation versus clinical outcomes of corneal excimer laser surface ablations.

Purpose: To investigate the recently reported discrepancy between theoretical expectations and clinical outcomes of corneal ablations after excimer laser corneal refractive surgery.

Methods: Thirty-four eyes of 25 patients who had laser epithelial keratomileusis (LASEK) for myopia (mean -6.26±2.

Customized aspheric intraocular lenses calculated with real ray tracing.

Purpose: To calculate the exact geometry of custom intraocular lenses (IOLs) for pseudophakic eyes and theoretically predict the residual wavefront error by real ray tracing based on Snell's law.

Setting: Centre for Ophthalmology, University Hospital, Tübingen, Germany.

Methods: Individual computer models were constructed based on measurements, including corneal topography and axial length.

Calculating intraocular lens geometry by real ray tracing.

Purpose: An implementation of real ray tracing based on Snell's law is tested by predicting the refraction of pseudophakic eyes and calculating the geometry of intraocular lenses (IOLs).

Methods: The refraction of 30 pseudophakic eyes was predicted with the measured corneal topography, axial length, and the known IOL geometry and compared to the manifest refraction. Intraocular lens calculation was performed for 30 normal eyes and 12 eyes that had previous refractive surgery for myopia correction and compared to state-of-the-art IOL calculation formulae.