How Does a Tonometer Work?

Glaucoma is one of the leading causes of permanent blindness around the world.  More than 3 million people suffer from this condition in the U.S. alone.  A tonometer offers a succinct and accurate way to diagnose glaucoma, and then identify treatment options. Tonometry is a practice in which the eye’s intraocular pressure (IOP) is measured.  This is determined by the eye surface’s firmness or tone.  Normal IOP readings typically register around 15.  Readings at 21 or higher often indicate a likelihood for glaucoma development. THERE ARE FOUR COMMON TYPES OF TONOMETERS 1. Non-contact This type of tonometer has been popularized by eyewear retailers like LensCrafters.  Non-contact tonometry is often called the “air puff” test.  Here, a small blast of air is shot into the eye, flattening the cornea. 2. Goldman The Goldman tonometer is the most well-known, and it’s considered by many to be the most accurate.  This tonometer involves the use of eye drops and dye Read More

Zeiss IOL Master

The Zeiss IOL Master was approved by the United States FDA in 2000. A non-contact optical device that measures the distance from the corneal vertex to the retinal pigment epithelium by partial coherence interferometry, the Zeiss IOL Master is consistently accurate to within ±0.02 mm or better. The IOL Master is the first such device to be widely used in clinical ophthalmology. Calibrated against the ultra-high resolution 40-MHz Grieshaber Biometric System, an internal algorithm approximates the distance to the vitreoretinal interface, for the equivalent of an immersion A-scan ultrasonic axial length. Considering the fact that axial length measurements by A-scan ultrasonography (using a standard 10-MHz transducer) have a typical resolution of 0.10 mm to 0.12 mm, axial length measurements by the IOL Master represent a fivefold increase in accuracy. The IOL Master allows fast, accurate measurements of eye length and surface curvature, necessary for cataract surgery. The IOL Master Read More

Haag-Streit Lenstar LS900

While the introduction of optical biometry revolutionized cataract surgery in the late 1990s, Haag-Streit has introduced the latest technology in biometry with the release of the Lenstar LS 900. The Lenstar provides highly accurate laser optic measurements for every section of the eye − from the cornea to the retina − and is the first optical biometer on the market that can measure the thickness of the crystalline lens. With its integrated Olsen formula, one of the latest generation multivariable IOL calculation methods, the Lenstar provides the user with the best possible IOL prediction. Dual zone keratometry, with 32 measurement locations or topography measurement with the optional T-Cone, provides reliable and precise measurements for the K values, axis, and astigmatism which are essential to the sophisticated planning of toric lenses. The Lenstar LS 900 offers the optimal planning platform for superior refractive outcomes in cataract surgery, both now and in the future. Read More

LASIK Excimer Lasers

LASIK and other forms of laser refractive surgery, such as PRK and LASEK, all use a highly specialized excimer laser to reshape the cornea and correct refractive errors including myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. Excimer lasers have revolutionized the field of laser eye surgery, and over the decades have greatly increased in safety, efficacy and predictability of corneal refractive surgery outcomes. LASIK Excimer lasers have the ability to remove, or "ablate," microscopic amounts of tissue from the cornea's underlying stromal layer, with a very high degree of accuracy, and without damaging the surrounding corneal tissue. Several FDA-approved excimer lasers are on the market, but one is not necessarily "better" than another. A few of these lasers include the Alcon EX500, AMO VISX S4 IR, Bausch & Lomb Technolas TENEO 317, & Zeiss MEL 80 Excimer Laser, just to name a few. The most suitable excimer laser for a practice will depend on th Read More

OCT Technology

Optical Coherence Tomography (OCT) is a fundamentally new type of optical imaging modality. OCT performs high-resolution, cross-sectional tomographic imaging of the internal microstructure in materials and biologic systems by measuring backscattered or back reflected light. OCT images are two-dimensional data sets which represent the optical backscattering in a cross-sectional plane through the tissue. Image resolutions of 1 to 15 µm can be achieved one to two orders of magnitude higher than conventional ultrasound. Imaging on the OCT can be performed in situ and in real time. The unique features of this technology enable a broad range of research and clinical applications. OCT, imaging the internal cross-sectional microstructure of tissues using measurements of optical backscattering or back reflection, was first demonstrated in the early nineties. OCT imaging was performed in vitro in the human retina and in atherosclerotic plaque as examples of imaging in transparent, weakly sca Read More