Change text size: A | A | A

Preoperative Biometry Basics

Understanding IOL Calculations

Accurate preoperative biometry is essential to attaining optimal results with the AcrySof^® IQ ReSTOR^® IOL. These precise measurements of the shape and size of the eye help ensure that proper IOL power is implanted, potentially providing freedom from glasses. Preoperative biometry measurements include axial length and corneal curvature.

Axial Length

Axial length is the distance from the cornea to the retina. Use of a standard immersion A-scan is recommended during preoperative biometry because it involves no direct corneal contact or compression. An A-scan uses ultrasound echolocation to locate the internal structures of the eye, which are then mapped as a one-dimensional sonogram. This method gives a true axial length and is generally considered operator-independent.

Keratometry

Another stage of preoperative biometry is the measurement of corneal curvature and power, also called keratometry. This plays a critical role in the accuracy of the IOL power calculation. Keratometry detects and measures astigmatism by determining the steepest and flattest meridians of the corneal surface. K readings may be obtained manually or by an automated method. These readings are typically expressed in diopters, while millimeters (mm) serve as an alternate unit of measurement.

Optical Biometry

Optical biometers, such as the Carl Zeiss Meditec IOLMaster^†, perform a new method of preoperative biometry where infrared light is used to calculate axial length, keratometry and anterior chamber depth. This precise, rapid method reduces technical variance and eliminates physical contact with the cornea. However, optical biometry may not perform consistently with patients who have dense cataracts.

† The IOLMaster is a registered trademark of Carl Zeiss Corporation.

Focus^™ Magazine

Get the full story on cataract surgery – request your complimentary copy now!

Practice Performance

This Practice Performance Zone is the online companion to the Premium Lens practicePAK. Here you will find electronic versions of all the items discussed in the practicePAK as well as new items as they become available.

Home Invite a Colleague Site Map CataractSurgery.com

Copyright © 2010 Alcon, Inc. a global company based in Hünenberg, Switzerland. The information and materials within this section pertain to the U.S. market only. Not all products are approved in every market, and approved labeling and instructions may vary by local country. See Privacy Policy and Terms & Conditions for the use of this site.

This Website may contain general information relating to various medical conditions and their treatment. Such information is provided for informational purposes only and is not meant to be a substitute for advice provided by a doctor or other qualified healthcare professional. You should not use the information contained herein for diagnosing a health or fitness problem or disease. You should always consult with a doctor or other healthcare professional.

Other Alcon Informational Websites:

Glaucoma Eye vitamins Allergy eyes Nasal allergies Ear infection treatment Cataract surgery Dry eye Contact lens solution

CAUTION: Federal law restricts this device to sale by or on the order of a physician.

INDICATIONS: The AcrySof® IQ ReSTOR® Apodized Diffractive Optic Posterior Chamber Intraocular Lens (IOL) is intended for primary implantation for the visual correction of aphakia secondary to removal of a cataractous lens in adult patients with and without presbyopia, who desire near, intermediate and distance vision with increased spectacle independence. The lens is intended to be placed in the capsular bag.

WARNINGS: Careful preoperative evaluation and sound clinical judgment should be used by the surgeon to decide the risk/benefit ratio before implanting a lens in a patient with any of the conditions described in the Physician Labeling. Some adverse reactions that have been associated with the implantation of intraocular lenses are: hypopyon, intraocular infection, acute corneal decompensation, macular edema, pupillary block, retinal detachment, and secondary surgical intervention (including but not limited to lens repositioning, biometry error, visual disturbances or patient dissatisfaction). As a result of the multifocality, some visual effects (halos or radial lines around point sources of light at night) may also be expected due to the superposition of focused and unfocused multiple images. A reduction in contrast sensitivity may also be experienced by some patients, especially in low lighting conditions such as driving at night. In order to achieve optimal visual performance with this lens, emmetropia must be targeted. Patients with significant preoperative or expected postoperative astigmatism >1.0D may not achieve optimal visual outcomes. Care should be taken to achieve IOL centration, as lens decentration may result in a patient experiencing visual disturbances under certain lighting conditions.

PRECAUTIONS: Do not resterilize. Do not store over 45° C. Use only sterile irrigating solutions such as BSS® or BSS PLUS® Sterile Intraocular Irrigating Solution. Clinical studies with the AcrySof® IQ ReSTOR® IOL indicated that posterior capsule opacification (PCO), when present, developed earlier into clinically significant PCO. Studies have shown that color vision discrimination is not adversely affected in individuals with the AcrySof® Natural IOL and normal color vision. The effect on vision of the AcrySof® Natural IOL in subjects with hereditary color vision defects and acquired color vision defects secondary to ocular disease (e.g., glaucoma, diabetic retinopathy, chronic uveitis, and other retinal or optic nerve diseases) has not been studied. The long-term effects of filtering blue light and the clinical efficacy of that filtering on the retina have not been conclusively established.

ATTENTION: Reference the Physician Labeling/Directions for Use for a complete listing of indications, warnings and precautions.