A Model of a Quantitative Corneal Haze Meter Using the ASL-1000 Confocal Microscope

Abstract

Abstract: : Purpose: To develop a protocol for measurement of corneal hazeutilizing the ASL-1000 scanning confocal microscope, in conjunctionwith a standard scattering material to maximize instrument sensitivityand responsiveness in the region of clinical interest.Methods:The ASL-1000 confocal microscope was modified and adapted toestablish mathematical relations for the integration of opacitiesanterior to a given depth in a corneal cross-section. Measurementswere conducted to test the feasibility of various calibrationmaterials with regard to the dynamic range of scattered hazeintensity in order to identify the optimal material for thesimulation of corneal scattering. Stepped dilutions for eachmaterial were tested using the modified ASL-1000 system.Results:Using the modified ASL-1000 system, a corneal haze calibrationsystem and mathematical relation were successfully established.A standard preparation of 4000 NTU formazin was found to serveas an optimal non-biological calibration reference material.Its dynamic range for opacity density was found to adequatelycoincide the haze density range of clinical interest for thecornea.Conclusion: The ASL-1000 confocal corneal microscopecan be appropriately modified and adapted to measure cornealhaze. The 4000 NTU nephelometric formazin preparation is theoptimal calibration standard, with a haze intensity dynamicrange covering the range of clinical interest for the cornea.The modified ASL-1000, when calibrated with the 4000 NTU formazin,offers a novel system for objective quantification of cornealhaze. 

 

Keywords: 471 microscopy: confocal/tunneling • 374 cornea: stroma and keratocytes • 431 imaging/image analysis: non-clinical