الفهرس 
Anatomy and Physiology of the VitreousOnly 14 pages are availabe for public view
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Abstract
Vitreous body makes up approximately 80% of the volume of the eye and thus is the largest single structure of the eye.
The vitreous has support function for the retina and filling up function of the vitreous body cavity, acts as a diffusion barrier between the anterior and the posterior segment of the eye, has metabolic buffer function, and functions in maintaining the eye’s optical transparency.
Direct IVI has the obvious advantage of being able to achieve immediate therapeutic concentrations in the eye, bypassing the ocular barriers while largely avoiding adverse effects associated with systemic or topical treatment.
A new and promising application for IVI is the administration of anti-VEGF for the treatment of various retinal vascular disorders including vascular permeability and macular edema due to (RVO, DR, Coats’ disease and CME), CNV due to (AMD, PM, angioid streaks, idiopathic CNV, CO and RAP), and INV.
The advantages of anti-VEGF agents are that they are available, effective, safe, easy to be administered and can be repeated as needed.
Anti-VEGF injections can be used as primary therapy or adjunctive therapy to different treatment approaches such as (laser photocoagulation, PDT, vitrectomy), such combination can minimize the need for repeated injections .
Bevacizumab is now widely used as treatment for neovascular AMD, despite the subsequent licensing of pegaptanib and ranibizumab, because of the low cost of treatment when it is used as an intraocular agent.
IVTA is currently being used successfully for the treatment of macular edema due to (refractory DME, refractory PCME, Uveitis, RVO and Coats’ disease), for the treatment of CNV due to (AMD and angioid streaks). Also it is the best adjuvant for visualizing vitreous in vitrectomy.
IVTA can be used as primary therapy or adjunctive therapy to different therapeutic modalities. Currently, IVTA is not recommended as monotherapy for exudative AMD because studies to date have not shown long-term efficacy in improving visual acuity.
IVI of antiviral (ganciclovir or foscarnet) have been used successfully to control CMV retinitis, ARN and CMV anterior uveitis in some patients, especially those with recurrent or refractory disease. Multiple injections are required due to the short intraocular drug half-life.
It could decrease the duration of the systemic therapy to save cost and lower the risk of systemic side effects.
Viral infections arise from active blood-borne disease, patients receiving IVI remain at risk for recurrent disease, contralateral eye disease, non-ocular end-organ infections, and increased mortality. So both eyes must be closely monitored for 6 weeks after the initial presentation, also systemic therapy must be received.
Early diagnosis and treatment of endophthalmitis are essential to optimize visual outcome. Therapy is usually initiated empirically while microbiologic testing is being performed and it should cover Gram-positive and Gram-negative organisms.
Intravitreal antibiotics need not be supplemented with systemic antibiotics for treatment of exogenous endophthalmitis. In contrast, most cases of endogenous endophthalmitis require systemic antibiotics. Supplementary intravitreal injection may be supportive.
Endophthalmitis Vitrectomy Study advocated intravitreal antibiotics if presenting visual acuity was better than light perception and vitrectomy if presenting visual acuity was light perception or less.
In fungal endophthalmitis, if there is no sign of disseminated infection systemic antifungals can be effective; however, if significant vitreous involvement is present, intravitreal antifungals alone or in conjunction with vitrectomy should be seriously considered.
Currently,IVI of amphotericin B is the drug of choice for suspected fungal endophthalmitis. With increasing resistance to it, other antifungals such as flucytosine, caspofungin and azoles (voriconazole) can be considered.
Although an IVI is an extremely safe procedure, it is not completely devoid of risk. Complications may be related to the surgical procedure such as (corneal abrasions, lens injury, conjunctival hyperemia and subconjunctival hemorrhage, retinal detachment, retinal tears, vitreous hemorrhage and endophthalmitis) or relatrd to the drug injected intravitreally.
The most common side effect is increased IOP, which has been found on rare occasion to increase drastically (up to 50mmHg).Close IOP monitoring is crucial after IVI.