Stable oxime-crosslinked hyaluronan-based hydrogel as a biomimetic vitreous substitute

Vitreous substitutes are clinically used to maintain retinal apposition and preserve retinal function; yet the most used substitutes are gases and oils which have disadvantages including strict face-down positioning post-surgery and the need for subsequent surgical removal, respectively. We have engineered a vitreous substitute comprised of a novel hyaluronan-oxime crosslinked hydrogel. Hyaluronan, which is naturally abundant in the vitreous of the eye, is chemically modified to crosslink with poly(ethylene glycol)-tetraoxyamine via oxime chemistry to produce a vitreous substitute that has similar physical properties to the native vitreous including refractive index, density and transparency. The oxime hydrogel is cytocompatible in vitro with photoreceptors from mouse retinal explants and biocompatible in rabbit eyes as determined by histology of the inner nuclear layer and photoreceptors in the outer nuclear layer. The ocular pressure in the rabbit eyes was consistent over 56 d, demonstrating limited to no swelling. Our vitreous substitute was stable in vivo over 28 d after which it began to degrade, with approximately 50% loss by day 56. We confirmed that the implanted hydrogel did not impact retina function using electroretinography over 90 days versus eyes injected with balanced saline solution. This new oxime hydrogel provides a significant improvement over the status quo as a vitreous substitute.

Severe retinal vasculitis in systemic lupus erythematosus leading to vision threatening paracentral acute middle maculopathy

Systemic lupus erythematosus can affect any organ system at presentation and throughout its course. Lupus retinal vasculitis is responsible for the visual loss of variable severity and typically ascribed to the involvement of pre-capillary superficial arterial vasculature. Using multimodal imaging techniques and electrophysiology, we demonstrate the first-ever case of severe lupus retinal vasculitis resulting in the rare association of paracentral acute middle maculopathy. The findings showcase the involvement of both superficial and deep retinal capillary vasculature and the localisation of retinal dysfunction. This precise evaluation facilitated the timely use of combination immunomodulatory therapy with localised pan-retinal laser photocoagulation, resulting in the preservation of vision.

Special considerations for pediatric vitreoretinal surgery

In this review, the authors present special considerations a vitreoretinal surgeon should take into account before embarking on surgery in a pediatric eye. First, the anatomy of a pediatric eye is different from an adult and changes as the child grows. This is important especially in relation to the placement of transconjunctival ports. The structural characteristics of the sclera are also different, with lower scleral rigidity found in pediatric eyes. When considering vitrectomy, a posterior pars plicata lens-sparing technique should be considered. However, this may not be possible in complicated total detachments where anterior translimbal vitrectomy may be the method of choice. Scleral buckles are preferred for certain cases, and division of the encirclage is advocated in children below the age of 2 years, once the retina has stabilized. Enzymatic vitreolysis has been described as a preoperative adjunct to enhance complete detachment of the posterior hyaloid and reduce iatrogenic retinal breaks. However, its use in pediatric eyes has been limited, and larger studies are warranted. Finally, postoperative visual rehabilitation and treatment of amblyopia are key to maximizing functional outcomes in the pediatric patient. Co-management with a pediatric ophthalmologist and enlisting the co-operation of the parents are essential.

Multi-Spectral Imaging of Circumscribed Choroidal Hemangioma Introduction

BACKGROUND AND OBJECTIVE

To illustrate the features of a circumscribed choroidal hemangioma (CCH) using Annidis RHA multi-spectral imaging (MSI) technology (Annidis Corporation, Ottawa, Canada). This novel imaging technique uses non-overlapping, narrow-band LED light sources ranging from 520 nm to 940 nm to create a monochromatic series of en face fundus images and oxy/deoxyhemoglobin contrasted maps of the retina and choroid.

PATIENTS AND METHODS

Annidis RHA MSI images were taken of a 67-year-old Chinese male with CCH. These en face fundus images are presented alongside the traditional fundus photograph, optical coherence tomography, and fluorescein and indocyanine green angiograms.

RESULTS

Multi-spectral en face images of the outer retina and choroid demonstrated a clearly delineated lesion with a disorganized choroidal vascular network and increased reflectance/ oxyhemoglobin levels within.

CONCLUSION

MSI technology is a noninvasive imaging technique that can depict the vascular features and choroidal oxygenation of CCH lesions and has a potential role in monitoring its growth complications. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:572-575.].