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Application of Nonlinear Microscopy in Life Sciences
Published in Lingyan Shi, Robert R. Alfano, Deep Imaging in Tissue and Biomedical Materials, 2017
Zdenek Svindrych, Ammasi Periasamy
An alternative approach to excite and collect fluorescence from deep within a live tissue is to use GRIN objective lenses. Instead of having direct the excitation and emission photons through thick layers of scattering tissue or to remove large parts of the tissue, a thin (down to 0.35 mm) GRIN lens can be inserted up to 10 mm into the tissue and relay the image plane deep inside the tissue to a plane just outside the protruding end of the lens [64]. A common 2P microscope (with suitable objective lens) is then used to image this relayed plane. While the observed animal still needs to be rigidly connected to the microscope, this approach is less invasive than, for example, a cranial window; and images with subcellular resolution can be obtained from very deep layers of tissue. Moreover, adaptive optics can be used to correct for any optical aberrations introduced by the GRIN lens [65].
Adaptive optics ophthalmoscopes
Published in Pablo Artal, Handbook of Visual Optics, 2017
All optical systems are affected by optical aberrations that degrade imaging performance. Correcting the lower-order aberrations of the eye’s optics such as defocus and astigmatism provides most people with good vision. However, in order to better understand the function of the normal retina and the pathophysiology of retinal disease, one needs to look into the eye. This can, of course, be accomplished by studying histological preparations ex vivo, but the retina has to be studied in vivo in order to diagnose and monitor retinal disease and evaluate efficacy of medical treatment. This was facilitated by the independent inventions of the ophthalmoscope by Charles Babbage in 1847 and the indirect ophthalmoscope by Hermann von Helmholtz in 1851. The functionality and usability of the ophthalmoscope were greatly advanced by the invention of the handheld direct-illuminating ophthalmoscope by Francis Welch and William Allyn in 1915. Modern-day versions of the Welch–Allyn ophthalmoscope are routinely used in eye examinations today.
Corectopia grading: A novel classification system
Published in Seminars in Ophthalmology, 2022
Natalia Anisimova, Lisa Arbisser, Argyrios Tzamalis, Beáta Éva Petrovski, Natalya Shilova, Goran Petrovski, Sergey Anisimov, Boris Malyugin
The pupil is a critical element of the eye’s optical system. Its exact size and location are important in forming the visual axis. The threshold of visually significant optical aberrations increases with pupil dilation.13 Normally, the pupil is located about 0.5 mm inferonasal from the center of the iris and is characterized by an average pupil non-circularity of 0.016614. The tendency for mirror symmetry of the pupil shape and location is present between left and right eyes in healthy individuals during both constriction and dilation in response to lighting variation.14 Pupil constriction is associated with an average movement of approximately 0.2 mm nasally and superiorly with respect to the limbus center.14,15 However, larger shifts in pupil decentration up to 0.6 mm have been shown in normal individuals when the reference point was set at the initial position of the pupil center.16 Age-related changes of the iris include the phenomenon of senile miosis over a wide range of ocular illuminance levels,17 and non-circularity is known to increase with age (0.0015/decade) (ref. 14).
Correlation between Keratoconus and Pollution
Published in Ophthalmic Epidemiology, 2021
Tristan Jurkiewicz, Anne-Sophie Marty
Keratoconus is a corneal ectasia most often bilateral and asymmetrical.1 It mainly occurs during puberty and tends to affect active people, which explains its strong impact on patients’ quality of life. During the progression of the disease, the cornea slowly changes from an ellipsoid to an irregular, conical shape. This leads to myopization of the eye and an increase in astigmatism.2 Evolution of keratoconus also induces a progressive increase in cornea power and its thinning, making it a contraindication for refractive surgery. It is a multifactorial disease, meaning it comes from multiple potential causes. The corneal changes observed are due to disorganization of collagen and extracellular matrix (including a reduction in inter-proteoglycan molecular bridges) as well as an increase in keratocyte apoptosis.3 These changes in corneal structure result in high-grade optical aberrations that are detrimental to patients and directly impact their quality of life. Today, the doctor’s decision about the treatment offered is based on the stage of the keratoconus, its evolution, as well as the possible gain in visual acuity.
The short term effect of trehalose and different doses of sodium hyaluronate on anterior corneal aberrations in dry eye patients
Published in Cutaneous and Ocular Toxicology, 2021
Yener Yildirim, Cemal Ozsaygili, Bekir Kucuk
HOAs refers to all 3rd- and 6th-order aberrations, but especially the 3rd- and 4th-order aberrations were thought to play important role in the visual quality27. In this present study, all artificial tears that are statistically significant reduced the RMS of the total, LOA, HOAs, and SA. In addition, 0.15% and 0.20% SH further reduced these aberrations more than 0.15% SH + Trehalose, but this was not significant. Apart from corneal scarring and superficial punctate keratopathy, recent studies suggested that a decrease in visual quality could be related to the higher optical aberrations4,17,28. Yamashita et al.29 reported that HOAs of the cornea decreased and the optical characteristics improved after 0.1% SH in the dry eye patients. However, in another study, SH showed no statistically significant difference between treatment and control groups in total high-grade aberrations, coma, and spherical aberrations during the study in dry eye patients19. These differences may relate to the grade of dry, using different viscosity of artificial tears, and elapsed time after the application of the artificial tear.