Increased episcleral venous pressure in a mouse model of circumlimbal suture induced ocular hypertension

Viral Vector-Induced Ocular Hypertension in Mice

Viral transduction of the mouse trabecular meshwork using a variety of transgenes associated with glaucoma generates an inducible and reproducible method for generating ocular hypertension due to increased aqueous humor outflow resistance of the conventional outflow pathway. Both adenovirus serotype 5 (Ad5) and lentiviruses have selective tropism for the mouse trabecular meshwork with intraocular injections. Accurate intraocular pressures are easily measured using a rebound tonometer, and aqueous humor outflow facilities can be measured in anesthetized live mice.

An inducible rodent glaucoma model that exhibits gradual sustained increase in intraocular pressure with distinct inner retina and optic nerve inflammation

Glaucoma is a chronic and progressive neurodegenerative disease of the optic nerve resulting in loss of retinal ganglion cells (RGCs) and vision. The most prominent glaucoma risk factor is increased intraocular pressure (IOP), and most models focus on reproducing this aspect to study disease mechanisms and targets. Yet, current models result in IOP profiles that often do not resemble clinical glaucoma. Here we introduce a new model that results in a gradual and sustained IOP increase over time. This approach modifies a circumlimbal suture method, taking care to make the sutures 'snug' instead of tight, without inducing an initial IOP spike. This approach did not immediately affect IOPs, but generated gradual ocular hypertension (gOHT) as the sutures tighten over time, in comparison to loosely sutured control eyes (CON), resulting in an average 12.6 mmHg increase in IOP at 17 weeks (p < 0.001). Corresponding characterization revealed relevant retinal and optic nerve pathology, such as thinning of the retinal nerve fiber layer, decreased optokinetic response, RGC loss, and optic nerve head remodeling. Yet, angles remained open, with no evidence of inflammation. Corresponding biochemical profiling indicated significant increases in TGF-β2 and 3, and IL-1 family cytokines in gOHT optic nerve tissues compared to CON, with accompanying microglial reactivity, consistent with active tissue injury and repair mechanisms. Remarkably, this signature was absent from optic nerves following acute ocular hypertension (aOHT) associated with intentionally tightened sutures, although the resulting RGC loss was similar in both methods. These results suggest that the pattern of IOP change has an important impact on underlying pathophysiology.

Posterior ocular structural changes and glaucoma susceptibility in patients with hemifacial spasm

PURPOSE

To evaluate the changes in the posterior ocular structures and glaucoma susceptibility in patients with hemifacial spasm (HFS).

STUDY DESIGN

Prospective observational clinical study.

METHODS

This study included 46 long-standing HFS patients with a minimum follow-up of 12 months. The participants' eyes were divided into three groups: (1) 46 affected eyes of patients with clinical HFS; (2) 46 unaffected fellow eyes and, (3) 46 eyes of healthy sex and age-matched controls. All participants were assessed by a detailed clinical examination and optical coherence tomography (OCT) with enhanced depth imaging (EDI). EDI-OCT images were binarized using ImageJ software. Peripapillary retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), choroidal thickness (CT), and choroidal vascularity index (CVI) were used to compare the structural characteristics of the affected eyes with fellow and control eyes. The CT measurements were performed from the subfoveal and locations at 750 μm and 3000 μm intervals from the foveal center, and the average of CT measurements at 5 locations was accepted as mean CT.

RESULTS

The demographic and clinical characteristics among the groups were similar (for all, P > 0.05). Mean peripapillary RNFL thickness of the inferior quarter was significantly lower in affected eyes, compared to fellow eyes (P = 0.023) and control eyes (P = 0.040). Mean GCC thickness significantly decreased in affected eyes, compared to fellow eyes (P = 0.019) and healthy controls (P = 0.008). Mean CT thickness significantly decreased in affected eyes, compared to fellow eyes (P = 0.002) and healthy controls (P < 0.001). Mean subfoveal CVI (65.94% ± 1.46) was found to be significantly thinner than the unaffected fellow (68.19% ± 1.84, P = 0.011) eyes and control eyes (67.23% ± 0.84, P = 0.044).

CONCLUSIONS

This study's outcomes show that long-standing HFS is associated with glaucoma-associated morphological OCT findings and decreased both CT and subfoveal choroidal vascularity. These findings may be related to the fact that the posterior ocular structures are affected by long-lasting paroxysmal orbicularis contractions.