ABSTRACT
Perfect vortex beams (PVBs) have intensity distributions independent of their topological charges. We propose an alternative formulation to generate PVBs through Laguerre-Gauss beams (LGBs). Using the connection between Bessel and LGBs, we formulate a modified LGB that mimics the features of a PVB, the perfect LGB (PLGB). The PLGB is closer to the ideal PVB, maintaining a quasi-constant ring radius and width. Furthermore, its number of rings can be augmented with the order of the Laguerre polynomial, showing an outer ring independent of the topological charge. Since the PLGB comprises a paraxial solution, it is closely related to an experimental realization, e.g., using spatial light modulators [Phys. Rev. A100, 053847 (2019)PLRAAN1050-294710.1103/PhysRevA.100.053847].
ABSTRACT
PURPOSE: To perform a pilot study of the neuro-peripapillary retinal tissue deformation during the cardiac cycle among healthy eyes, ocular hypertensive (OHT), open angle glaucoma suspect (OAG-S), and early open angle glaucoma (EOAG) patients using video rate optical coherence tomography (OCT) image series. METHODS: OCT line scan sequences of the same region of the optic nerve head (ONH) were obtained from 15 EOAG, 6 OHT, 10 OAG-S, and 10 healthy age-matched eyes. One eye per patient was studied. Changes in the axial distance between the inferotemporal peripapillary retina and the prelaminar tissue, in time, were determined using an automated custom made algorithm. Linear correlations between this neuro-peripapillary retinal (N-PP) deformation and variables measured during the full ophthalmic examination are analyzed. RESULTS: Healthy eyes showed larger N-PP deformation (4.8 ± 1 µm) than the OHT (3.5 ± 0.3 µm, p = 0.015), OAG-S (3.8 ± 0.8 µm, p = 0.045), and EOAG (3.2 ± 0.7 µm, p < 0.001) groups. Eyes with lower ocular pulse amplitude, thinner RNFL's, or worse visual fields showed smaller N-PP deformation, depending on the diagnosis. A linear model to explain deformation within the EOAG group with intraocular pressure and systolic perfusion pressure as predictors was found to be significant (R2 = 0.767, p < 0.001). CONCLUSIONS: Smaller mean N-PP deformation was observed in the EOAG, OAG-S, and OHT groups compared to healthy eyes in this pilot study. The measured deformation correlated with risk factors for the glaucomatous optic neuropathy, but these correlations varied depending on the diagnosis. The role of pulsatile neuro-peripapillary retinal deformation in the pathophysiology of OAG remains to be determined.
Subject(s)
Choroid/blood supply , Glaucoma, Open-Angle/physiopathology , Intraocular Pressure/physiology , Optic Disk/physiopathology , Pulsatile Flow/physiology , Retina/physiopathology , Adult , Aged , Aged, 80 and over , Biomechanical Phenomena , Female , Healthy Volunteers , Humans , Male , Middle Aged , Nerve Fibers , Ocular Hypertension/physiopathology , Optic Disk/diagnostic imaging , Pilot Projects , Retina/diagnostic imaging , Retinal Ganglion Cells , Risk Factors , Tomography, Optical Coherence , Visual FieldsABSTRACT
Optical coherence tomography (OCT) imaging has become a standard diagnostic tool in ophthalmology, providing essential information associated with various eye diseases. In order to investigate the dynamics of the ocular fundus, we present a simple and accurate automated algorithm to segment the inner limiting membrane in video-rate optic nerve head spectral domain (SD) OCT images. The method is based on morphological operations including a two-step contrast enhancement technique, proving to be very robust when dealing with low signal-to-noise ratio images and pathological eyes. An analysis algorithm was also developed to measure neuroretinal tissue deformation from the segmented retinal profiles. The performance of the algorithm is demonstrated, and deformation results are presented for healthy and glaucomatous eyes.