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Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Embryologically, the vitreous is developed in three stages. The primary vitreous fills the space between the invaginating optic cup and the lens placode. It is, in turn, filled by vascularized mesoderm which extends from the optic nerve to the posterior lens and connects with the tunica vasculosa lentis (Figure 16). The secondary vitreous forms around the primary and is secreted by the neuroectoderm. The primary vitreous will eventually degenerate leaving its remnant, Cloquet’s canal, and the secondary vitreous to fill the posterior cavity of the eye. Failure of this atrophy results in a persistent hyaloid artery and possibly an associated cataract. Although the primary vitreous atrophies in all mammals, it does not do so at the same time. In humans, the primary vitreous does not carry blood beyond the seventh month,120 while in the dog and rat, these vessels can remain patent for up to 17 days postpartum.122,123 In addition, it has been estimated that 60% of Sprague-Dawley and 90% of Ola:Wistar rats at 6 weeks of age have a persistence of the hyaloid vessels which may be associated with vitreal hemorrhage.123 The tertiary vitreous is the lenticular zonules.
Pediatric vitreoretinal surgery
Published in A Peyman MD Gholam, A Meffert MD Stephen, D Conway MD FACS Mandi, Chiasson Trisha, Vitreoretinal Surgical Techniques, 2019
The elements of the eight-part eye examination should be documented: visual acuity, pupillary examination, versions and ductions, external examination, tonometry, visual fields, slit-lamp biomicroscopy, and dilated fundus examination. Any ocular abnormalities that might complicate the surgical approach should be noted, including developmental issues (microphthalmia, cataract, and corneal opacity), traumatic sequelae (hyphema, hypopyon, vitreous hemorrhage, conjunctival chemosis, wound leak, iris deformity, and flat anterior chamber), and disease-related problems (tunica vasculosa lentis, retinolenticular adherence, and vitreous hemorrhage). The iris should be evaluated to determine if iris hooks will be necessary. Particular attention should be directed toward the relationship of the retina to the lens in order to avoid inadvertent retinal breaks during the placement of sclerotomies. If the view precludes adequate visualization of the fundus, B-scan ultrasonography is indicated. The ultrasound examination should determine the configuration and type of retinal detachment, the presence of vitreous hemorrhage, the presence of posterior vitreous detachment, the presence of choroidal detachment, any intraocular masses or calcifications, and globe integrity.
Write short notes on the prenatal development of the lens. Use annotated diagrams where possible
Published in Nathaniel Knox Cartwright, Petros Carvounis, Short Answer Questions for the MRCOphth Part 1, 2018
Nathaniel Knox Cartwright, Petros Carvounis
The hyaloid artery gives rise to a series of small capillaries that anastomose with choroidal and long ciliary arteries to form a vascular capsule, the tunica vasculosa lentis, providing the rich nutrient supply necessary for the rapid growth of the lens during development. This capsule regresses shortly before birth.
Combined X-linked familial exudative vitreoretinopathy and retinopathy of prematurity phenotype in an infant with mosaic turner syndrome with ring X chromosome
Published in Ophthalmic Genetics, 2023
Sandra Hoyek, Marlene Wang, Audina M. Berrocal, Ashley Wong, Emily M. Place, Heather Mason-Suares, Angela E. Lin, Shizuo Mukai, Nimesh A. Patel
A 4-month-old girl initially diagnosed by an outside pediatric ophthalmologist with bilateral retinopathy of prematurity (Stage 3, zone II) and a mild temporal dragging in the right eye was referred to Massachusetts Eye and Ear for evaluation. She was born at a gestational age of 26 weeks and a birth weight of 760 g. The neonatal course included oxygen supplementation for chronic lung disease, delayed milestones, and swelling of the kidneys. Screening for ROP was initially performed at 31 weeks post-conceptual age and showed an immature retina without ROP that progressed to stage 3, zone II ROP at 39 weeks post-conceptual age, per the screening physician. At our institution, an ophthalmic examination at age 4 months (42 weeks post-conceptual age) showed that she could fix and follow with each eye and anterior segment with persistent tunica vasculosa lentis in the right eye.
Hyalocyte functions and immunology
Published in Expert Review of Ophthalmology, 2022
Stefaniya K Boneva, Julian Wolf, Peter Wieghofer, J Sebag, Clemens AK Lange
Around the fourth week of gestation during development of the eye, mesodermal cells enter the forming eye cup via the optic fissure, and, together with surrounding fibroblasts, constitute the primordial vitreous. Some of the mesodermal cells exhibit the morphological features of cells destined to be hyalocytes, expressing myeloid cell markers, such as major histocompatibility complex (MHC) and cluster of differentiation 45 (CD45) antigens, and can therefore be considered hyalocyte precursor cells [10,11]. The mesodermal cells further contribute to the anlage of the hyaloid vascular system, which is composed of the vasa hyaloidea propria, tunica vasculosa lentis, the pupillary membrane, and the hyaloid artery (Figure 2). The vasa hyaloidea propria anastomoses with the tunica vasculosa lentis and pupillary membrane to nourish the developing anterior segment. After reaching its zenith at approximately the 10th week of gestation, regression of the hyaloid vasculature is observed [12]. This process is vital for a clear optical axis and failure can result in crucial impairment of vitreo-retinal and ocular development. Changes in the proteomic profile of vitreous from human embryos aged 14 to 20 weeks gestation have suggested cytokine events that may be important in hyaloid vasculature regression [13].
Outcome of 532 nm Nd:YAG laser photocoagulation in retinopathy of prematurity from a referral center
Published in Clinical and Experimental Optometry, 2021
Selcuk Sizmaz, Ebru Esen, Nuhkan Gorkemli, Ayna Sariyeva, Nihal Demircan
The clinical presentation in groups is given in Table 1. There were no significant differences between groups by means of gender, stage of the disease, plus disease, and aggressive posterior ROP cases. In Group 1, with respect to Group 2, significantly more eyes had zone 1 disease (18% vs. 11.5%, p = 0.002). The number of eyes that featured tunica vasculosa lentis were 30 (27%) and 12 (9.2%) in Groups 1 and 2 (p < 0.001), respectively. The rates of additional laser treatment and pars plana vitrectomy—denoted as poor outcomes—were similar between groups. The rate of favourable outcome was 90.1% (100 vs. 118) in both groups (p = 0.997)