Haag-Streit Javal-Schiotz Keratometer

Haag-Streit

single-handed

Javal-Schiotz Keratometer

The Haag-Streit Javal-Schiotz Keratometer is a manual, two-position ophthalmometer designed to measure the anterior corneal curvature and assess astigmatism.

Type: Two-position variable mire keratometer, requiring adjustment for each principal meridian.

Measurement Principle: Utilizes a fixed image size with adjustable object size (self-illuminated mires: red square and green staircase design) to determine the radius of corneal curvature. The formula used is \( r = 2ul/o \), where \( r \) is the radius of the reflective surface, \( u \) is the distance between the surface and object, \( o \) is the object size, and \( l \) is the image size.

Measurement Range: Measures corneal curvature in the central 3–4 mm zone, providing corneal power in diopters (D) and radius of curvature in millimeters (mm). Typical corneal power measurements are around 44.3 ± 1.59 D, as reported in studies.Mire

Design: Uses two self-illuminated mires (red square and green staircase) held on a circumferential track to maintain a fixed distance from the eye.

Single-Handed Operation: The Haag-Streit single-handed base (e.g., serial numbers J95014688, J95018095) allows for easier manipulation during measurement, distinguishing it from other models. It is designed for one-handed operation, improving usability.

Illumination: Uses a 6V, 0.5A bulb for mire illumination.Physical

Applications: Primarily used to measure corneal curvature, astigmatism axis, and extent, critical for contact lens fitting, refractive surgery planning, and intraocular lens (IOL) calculations.