Granular Corneal Dystrophy in 830-nm Spectral Optical Coherence Tomography

Scanning Acoustic Microscopy Comparison of Descemet's Membrane Normal Tissue and Tissue With Fuchs' Endothelial Dystrophy

Purpose

To describe the application of scanning acoustic microscopy in the GHz-range (GHz-SAM) for qualitative imaging and quantitative characterization of the micromechanical properties of the Descemet's membrane and endothelial cells of cornea tissue.

Methods

Investigated were samples of a normal tissue and a tissue with Fuchs' endothelial dystrophy (FECD, cornea Guttata). Descemet's membranes were fixed on glass substrates and imaged utilizing a focused acoustic lens operating at a center frequency of 1 GHz.

Results

GHz-SAM data, based on the well-established V(z) technique, revealed discrepancies in the velocity of the propagation of Rayleigh surface acoustic waves (RSAW). RSAW were found to be slower in glass substrates with FECD samples than in the same glass substrates (soda-lime) with normal Descemet membrane, which indicates lower shear and bulk moduli of elasticity in tissues affected by FECD.

Conclusions

Noninvasive/nondestructive GHz-SAM, is utilized in this study for the imaging and characterization of Descemet membranes, fixated on glass substrates. V(z) signatures containing sufficient oscillations were obtained for the system of Descemet membranes on glass substrates. The observed variation in the microelastic properties indicates potential for further investigations with GHz-SAM based on the V(z) technique.

Dual band dual focus optical coherence tomography for imaging the whole eye segment

We developed an improved dual band dual focus spectral domain optical coherence tomography (SD-OCT) for in vivo 2D/3D imaging of the whole eye segment, including the whole anterior segment and retina. The system featured two OCT channels with two different bands centered at 840 nm and 1050 nm, which were designed to image the retina and the anterior segments of the eye, respectively. By combing the two probe light beams for co-axial scanning and separating them for focusing at different segments of the eye with a combination of three dichroic mirrors, we not only minimized the loss of the backscattered light from the sample but also improved the imaging depth, scan range and resolution. The full resolved complex (FRC) method was applied to double the imaging depth for the whole anterior segment imaging, with which an imaging depth of 36.71 mm in air was achieved. We demonstrated that this system was capable of measuring the dynamic changes of ocular dimensions, including the asphericity of the cornea and lens, during accommodation.

Spectral-domain OCT with dual illumination and interlaced detection for simultaneous anterior segment and retina imaging

We present Fourier-domain/spectral-domain optical coherence tomography (FD/SD-OCT) using a single spectrometer with dual illumination and interlaced detection at 830 nm, which can provide anterior segment and retinal tomograms simultaneously. Two orthogonal polarization components were used so that both parallel and focused beams could simultaneously be made incident on the eye. This configuration with a polarization-separated sample arm enables us to acquire images from the anterior segment and retina effectively with minimum loss of sample information. In the detector arm, a single spectrometer is illuminated via an ultrafast optical switch for interlaced detection. A graphical user interface (GUI) was built to control the optical switch for imaging the anterior segment and retina either simultaneously or individually. In addition, we implemented an off-pivot complex conjugate removal technique to double the imaging depth for anterior segment imaging. The axial resolution of our FD/SD-OCT system was measured to be ~6.7 μm in air, which corresponds to 4.9 μm in tissue (n = 1.35). The sensitivity was approximately 90 dB for both anterior segment and retina imaging when the acquisition speed was 35,000 A-scans per second and the depth position was near 120 μm from the zero-depth location. Finally, we demonstrated the feasibility of our system for simultaneous in vivo imaging of both the anterior segment and retina of a healthy human volunteer.

[Granular corneal dystrophy treated with deep anterior lamellar keratoplasty: comparing histological analysis and optical coherence tomography]

Granular corneal dystrophy is a rare autosomal dominant disease. It is characterized by breadcrumb-like granular opacities in the central corneal stroma. The mutation has been localized in the TGFβI gene, which codes for keratoepithelin, an adhesion protein found in corneal epithelium and stroma. We report the case of granular corneal dystrophy in a 60-year-old man complaining of reduced visual acuity. Slit-lamp examination revealed multiple opacities in the central stroma of his left eye, and recurrent deposits in his other eye 13 years after penetrating keratoplasty. An anterior segment optical coherence tomography (Visante(®) OCT) was used to determine the location of deposits, then a deep anterior lamellar keratoplasty was performed in his left eye. The depth of the deposits revealed by Visante(®) OCT correlated well with the postsurgical histological findings. Visante(®) OCT can therefore help choose between phototherapeutic keratectomy and lamellar keratoplasty, techniques that are less invasive than penetrating keratoplasty, which is advantageous since this dystrophy is known to recur after surgery.

Full-range imaging of eye accommodation by high-speed long-depth range optical frequency domain imaging

We describe a high-speed long-depth range optical frequency domain imaging (OFDI) system employing a long-coherence length tunable source and demonstrate dynamic full-range imaging of the anterior segment of the eye including from the cornea surface to the posterior capsule of the crystalline lens with a depth range of 12 mm without removing complex conjugate image ambiguity. The tunable source spanned from 1260 to 1360 nm with an average output power of 15.8 mW. The fast A-scan rate of 20,000 per second provided dynamic OFDI and dependence of the whole anterior segment change on time following abrupt relaxation from the accommodated to the relaxed status, which was measured for a healthy eye and that with an intraocular lens.

Confocal microscopy and optical coherence tomography imaging of hereditary granular dystrophy

OBJECTIVES

This case report examines the clinical characteristics of hereditary granular dystrophy through the use of slit lamp digital photography, confocal microscopy (CM) and optical coherence tomography (OCT). A review of the literature describing the histopathological and genetic associations of stromal dystrophies, suggest it may be possible to differentiate dystrophies based on their clinical manifestations, and appearances of CM and OCT images, with or without the use of genetic testing.

CASE REPORT

Two sisters, previously diagnosed with Granular (Groenouw I) Dystrophy, were examined. Examination included the use of digital slit lamp photography, CM and OCT imaging.

RESULTS

"Breadcrumb" opacities were visualized in the anterior two-thirds of the stroma with all three imaging techniques. Opacities were demonstrated in the posterior third of the stroma with the digital photography and OCT techniques.

CONCLUSIONS

The digital photography, CM and OCT images support the sister's diagnosis of Granular (Groenouw I) Dystrophy. Currently, genetic and histopathological testing are the only techniques available to determine exactly which corneal dystrophy and gene mutation are present. The results of this case report demonstrate that slit lamp digital photography, combined with CM and OCT may be capable of providing sufficient diagnostic information to diagnose corneal granular dystrophies in a clinical setting.

Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera

We describe a new ultrahigh speed Spectral OCT instrument making use of a CMOS camera and demonstrate high quality in vivo imaging of the anterior segment of the human eye. The high flexibility of the designed imaging system allows a wide range of imaging protocols. Two- and three-dimensional high quality OCT images of the cornea, the anterior chamber and the crystalline lens are presented. A high acquisition rate, up to 135,000 A-scans/second enables three-dimensional reconstruction of the anterior segment during lenticular accommodation, blinking and pupillary reaction to light stimulus. We demonstrate OCT tomographic real time imaging of the lens dynamics during accommodation and high quality OCT cross-sectional images of the entire anterior segment of the eye from the cornea up to posterior part of the crystalline lens.