Dual interferometer for dynamic measurement of corneal topography

Abstract

Abstract. The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman-Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates.

Biometric Measurement of Anterior Segment: A Review

“…In 2005, Licznerski et al [ 75 ] developed a double path shearing interferometer for corneal topography measurement. In 2016, Micali and Greivenkamp [ 76 ] designed a dual interferometer system for measuring the dynamic corneal topography using two aligned simultaneous phase-shifting polarization-splitting TGIs.…”

“…These technologies can be employed to achieve the accuracy of several micrometers but only cover the corneal region [ 43 ]. Moreover, it is imperative to instill fluorescein to the tear film as a diffusing agent for distinctly imaging the anterior corneal shape [ 67 , 76 , 80 ]. Additionally, the major drawback is that the low-pass filter should be inevitably applied during the interference fringe processing.…”

“…Head motion can be minimized by placing the subject’s head in a restraining fixture, such as a chin cup and forehead rest. Voluntary eye motion can be reduced by asking the subject to fixate on and track a stationary target [ 76 ]. However, the eyes remain in motion even during conscious fixation, referred as the involuntary motion [ 76 , 199 ].…”

Perangkat Fotokeratoskopi dengan Analisa Citra Digital untuk Deteksi Awal Astigmatisme

“…Metode yang digunakan pada topografi korena dapat dibagi menjadi dua kategori: metode berbasis refleksi dan metode berbasis proyeksi. Metode berbasis refleksi diantaranya adalah penggunaan pola lingkaran Placido, keratometer, dan videokeratoskopi, sedangkan contoh topografi kornea berbasis proyeksi adalah Scheimpflug pattern, slit photography, rasterstereofotografi, dan beragam metode interferometry [4], [11], [12] .…”

Optical methods for measuring corneal topography: A review

“…Recently D. Micali et al [55] reported the reconstruction of the corneal topography using a pair of polarization-splitting Twyman-Green interferometers by polarization division. This interferometer had a dynamic range of surface of 256…”