keratometer


Also found in: Dictionary, Encyclopedia, Wikipedia.
Related to keratometer: Pachymeter, Lensometer

keratometer

 [ker″ah-tom´ĕ-ter]
an instrument for measuring the curves of the cornea.

ker·a·tom·e·ter

(ker'ă-tom'ĕ-tĕr),
An instrument for measuring the curvature of the anterior corneal surface.
Synonym(s): ophthalmometer
[kerato- + G. metron, measure]

ker·a·tom·e·ter

(ker'ă-tom'ĕ-tĕr)
An instrument for measuring the curvature of the anterior corneal surface.
Synonym(s): ophthalmometer.
[kerato- + G. metron, measure]

keratometer

An optical instrument used to measure the radius of curvature of the cornea. See also KERATOMETRY.

keratometer

Optical instrument for measuring the radius of curvature of the cornea in any meridian. By measuring along the two principal meridians, corneal astigmatism can be deduced. The principle is based on the reflection by the anterior surface of a luminous pattern of mires in the centre of the cornea in an area of about 3.6 mm in diameter. Knowing the size of the pattern h and measuring that of the reflected image h′ and the distance d between the two, the radius of curvature r of the cornea can be determined using the approximate formula.
r = 2d (h′/h)
In addition, a doubling system (e.g. a bi-prism) is also integrated into the instrument in order to mitigate the effect of eye movements, as well as a microscope in order to magnify the small image reflected by the cornea. This instrument is used in the fitting of contact lenses and the monitoring of corneal changes occurring as a result of contact lens wear (Fig. K2). The range of the instrument can be extended approximately 9 D by placing a +1.25 D lens in front of the objective to measure steeper corneas. The range in the other direction can be extended by approximately 6 D using a −1.00 D lens to measure flatter corneas. Syn. ophthalmometer. See fitted on K; keratoscope; liquid lens; photokeratoscopy; Wollaston prism; Javal's rule; Topogometer; videokeratoscope.
Fig. K2 Schematic diagram of the Reichert keratometerenlarge picture
Fig. K2 Schematic diagram of the Reichert keratometer

Table K2 Extended keratometer range
with 21.00 Dwith 11.25 D
actual drum reading (D)extended value (D)actual drum reading (D)extended value (D)
36.0030.8745.0052.46
36.5031.3045.5053.05
37.0031.7346.0053.63
37.5032.1646.5054.21
38.0032.5947.0054.80
38.5033.0247.5055.38
39.0033.4548.0055.96
39.5033.8848.5056.55
40.0034.3049.0057.13
40.5034.7349.5057.71
41.0035.1650.0058.30
41.5035.5950.5058.88
51.0059.46
51.5060.04
52.0060.63

keratometer

an instrument for measuring the curves of the cornea.
References in periodicals archive ?
Keratometry Reading: Using Keratometer, HAAGSTREIT instrument (Jawal modle), KR was done by measuring the corneal curvature radius at two meridians, each 90deg apart.
The course of postoperative astigmatic changes was determined by keratometry performed with a standard calibrated keratometer (Bausch and Lomb).
Mahashewari and Yousuf using keratometer, corneal topography and automated refraction, found that the cornea became more regular following removal of the pterygium.
Although the traditional way of performing keratometry measurements was through manual keratometer, automated refractokeratometers are used practically.
Designed with simplicity and quality in mind, devices such as the Visuref 100 autorefractor/ keratometer, Visulens 500 digital lensmeter and Visuplan 500 non-contact tonometer ensure that you have diagnostic quality you can rely on, right from the start of the patient workflow.
An Optimized Refractive Keratometer (ORK) WAVEFRONT ANALYZER--Complete Ophthalmic Analysis System (COAS) version 1.
The instruments used in this study were: Auto refractor and Auto keratometer for measuring refractive error and corneal curvature respectively.
Their refraction was carried out and their readings noted using an auto refractive keratometer.
Seemless vision testing device integration gives instant access to diagnostic patient results from ophthalmic instruments; including oculur fundus images, OCT scans, autorefractor, keratometer, visual fields and more.
Pre-regs should, if using a keratometer, ensure they find the principal meridians, but also ensure that they know the theory on both one and two-step design keratometers.
Manual keratometry was done by keratometer (baush & lomb) and IOL power calculation by AScan (Biomedix).
Profilerplus combines an autorefractor, keratometer, aberrometer and corneal topography in a single system.