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Concept

Glaucoma

Summary

Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye remains open, with less common types including closed-angle (narrow angle, acute congestive) glaucoma and normal-tension glaucoma. Open-angle glaucoma develops slowly over time without pain. Peripheral vision may begin to decrease, followed by central vision, resulting in blindness if not treated. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from glaucoma, once it has occurred, is permanent. Eyes affected by glaucoma are referred to as being glaucomatous. Risk factors for gla

Official source

https://en.wikipedia.org/wiki/Glaucoma

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Glaucoma is one of the leading causes of blindness in the world. It results in an increase of the aqueous humour (AH) outflow pathway which leads to an increase of the intraocular pressure (IOP). Many treatments exists to reduce and stabilize the IOP such as medications, filtering surgery and Glaucoma Drainage Devices. So far computational fluid dynamics (CFD) modeling of the eye drainage system has not yet been well studied. Therefore our goals was to numerically simulate the AH outflow pattern in a model of the eye to further simulate a healthy and glaucomatous eye and various forms of glaucoma surgery. In order to do so, a 3D CDF model of the eye was created based on real geometries. Two methods were tested to this aim. The first one consisted in the injection of a CT contrast agent in an enucleated rabbit eye and visualization by a CT scan. A segmentation process was then achieved on the resulting scans to reconstruct the eye structures. The second one was based on microphotography stacks of histology of human eye whereof digital processing of the eye structure images and 3D reconstruction of a numerical model were performed. Due to resolution limitations several ocular structures could not be extracted from the segmentation process. In the second method, simulations of pressure and flow velocity distribution in healthy eye gave results comparable to physiology. Modeling the glaucomatous eye led to an increase in the IOP around 37 mmHG. We have been able to model the 3D structure of the eye based on real geometry. Flow simulations gave interesting results for the IOP and the flow velocity on a healthy eye. Mimicking glaucoma conditions led to an increase of the IOP from normal range, which went down to lower values after a filtering procedure. Further refinements in the boundary conditions for the filtering procedure shall improve the precision and efficacy of this innovative tool for modeling glaucoma surgery

2010

Comparison of acute non-visual bright light responses in patients with optic nerve disease, glaucoma and healthy controls

Lorette Leon

This study examined the effect of optic nerve disease, hence retinal ganglion cell loss, on nonvisual functions related to melanopsin signalling. Test subjects were patients with bilateral visual loss and optic atrophy from either hereditary optic neuropathy (n = 11) or glaucoma (n = 11). We measured melatonin suppression, subjective sleepiness and cognitive functions in response to bright light exposure in the evening. We also quantified the post-illumination pupil response to a blue light stimulus. All results were compared to age-matched controls (n = 22). Both groups of patients showed similar melatonin suppression when compared to their controls. Greater melatonin suppression was intra-individually correlated to larger post-illumination pupil response in patients and controls. Only the glaucoma patients demonstrated a relative attenuation of their pupil response. In addition, they were sleepier with slower reaction times during nocturnal light exposure. In conclusion, glaucomatous, but not hereditary, optic neuropathy is associated with reduced acute light effects. At mild to moderate stages of disease, this is detected only in the pupil function and not in responses conveyed via the retinohypothalamic tract such as melatonin suppression.

Nature Publishing Group2015

Design and validation of a telemetrically drived implantable glaucoma drainage device

Adan Villamarin

Glaucoma is one of the leading cause of irreversible blindness in the world and it usually occurs when the pressure inside the eyes gradually rises, permanently damaging the optic nerve. Medications and filtering surgery are two possible therapies available for patients suffering from this disease. In the same perspective, glaucoma drainage devices allowing a better outflow of the aqueous humor have been developed to address most of the problems present with the classic surgical techniques. However none of the implants currently available on the market have been able to date to address the problems related to the postoperative hypotony, the long-term fibrosis formation as well as the requirements to adjust filtration to the specific needs of the patients. In this context a new adjustable glaucoma drainage device is being currently developed that allows a continuous control of the outflow resistance. Its optimization and validation depends on previous outflow facility and resistance measurements. Thus 5 enucleated eyes from white New-Zealand rabbits have been perfused with a saline solution using a micropump before surgery and after implantation of a microtube (V-50

{Ex-PRESS}^{TM}

). The resulting outflow facilities were respectively 0.35 and 1.31

\mu

l/min/mmHg when the compliance was not altered by the filtering surgery and the microtube insertion. The tube composing the device showed a resistance equivalent to

23\times{10}^{-3}

mmHg/

\mu

l/min with an internal diameter equal to 250

\mu

m. From a theoretical point of view the linear relation between the adjustment of the resistance and the intraocular pressure has been verified. This relation was obtained by crushing the tube with a disc acting within the implant. The energy required to crush the tube was estimated to be at least

{10}^{-6}

Nm. These results support the idea that the construction of an adaptable glaucoma drainage device is possible opening the doors to an automatically driven sensor device

2009