A successful cataract surgery requires that the replacement intraocular lens (IOL) is a precise fit. Each eye is defined by specific dimensions, including length, corneal curvature and other variables. These elements must be accurately measured and the eye must have a healthy cornea and tear film in order to provide the sharpest vision possible post-surgery. In order to ensure optimal results, the team at Kelly Eye Centers uses the latest technology. Here are some of the measurement tools and techniques that will be used during your cataract evaluation to achieve success.
Zeiss IOL Master™
The Zeiss IOL Master™ is the gold-standard in instrumentation for pre-operative measurements of patients with cataracts. It quickly and precisely performs the necessary measurements in one session: eye axial length, corneal curvature, anterior chamber depth, and “white-to-white”. The IOL Master™ is a non-contact instrument that maximizes patient comfort.
Immersion Ultrasound A-scan
Occasionally, a patient will have a cataract that is too dense to achieve a reliable axial length measurement via the Zeiss IOL Master™, or a patient may present with a difference in the eye axial length between the two eyes. When either of these situations arises, an independent test called an Immersion Ultrasound A-scan is performed. The Immersion Ultrasound A-scan involves the patient being seated in a semi-reclined position, and an ultrasound probe with a water bath is placed on the corneal surface. The ultrasound unit measures the time it takes for the ultrasound wave to travel from the probe tip to the retina and back. A one-dimensional scan is produced measuring eye axial length.
Optical Coherence Tomography (OCT)
The Zeiss OCT provides Dr. Kelly a non-invasive way to scan the retinal nerve fiber layer (located in the back of the eye) to screen and monitor macular and optic nerve issues. The OCT uses light waves to produce a cross-sectional image of the retina and optic nerve. Pre-operative OCTs of the macula are frequently performed to determine if underlying structural issues (not easily identifiable due to a denser cataract) are present. Dr. Kelly counsels patients and seeks referrals to specialists for patients in which a macular or optic nerve issue may significantly affect vision after cataract surgery.
The Oculus™ Pentacam™ is a form of corneal topography used at the Kelly Eye Center. Corneal topography measures the curvature of the front corneal surface through a combination of computer-assisted video imaging and data analysis. To pictorially quantify corneal astigmatism, Dr. Kelly orders a Pentacam for each cataract evaluation. The Pentacam maps and measures corneal astigmatism by acquiring 50 measurements of both the front and back surface of the cornea in approximately 2 seconds. Dr. Kelly will then compare the Pentacam measurements to the Zeiss IOL Master and Cassini measurements for verification of astigmatism, and to make astigmatism and lens implant recommendations. The Pentacam is also utilized to perform corneal power measurements across different corneal zones in patients who have previously undergone refractive procedures.
The Cassini is another form of corneal topography used at the Kelly Eye Center. The Cassini utilizes 672 LED lights to measure the front corneal surface. Dr. Kelly compares all corneal measurements prior to making surgical treatment recommendations.