Proliferative diabetic vitreoretinopathy

Proliferative diabetic vitreoretinopathy (PDR) is characterised by the growth of blood vessels into the vitreous and neovascularisation of the retina. These neovascularisations lead to vitreous haemorrhage, creating additional fibrous epiretinal proliferations. 

J.S. Rinkoff, E. de Juan Jr, B.W. Me Cuen, Silicone oil of retinal detachment with advanced proliferative vitreoretinopathy following failed vitrectomy for proliferative diabetic retinopathy. Am. J. Ophthalmol. 101 (1986) 181-186. 

A heavier-than-water fluorinated silicone oil was used in the treatment of 30 selected cases of complicated retinal detachment due to proliferative vitreoretinopathy (n = 19), proliferative diabetic retinopathy with traction detachment (n = 2), giant retinal tears (n = 5), ruptured globe with retinal detachment (n = 2), massive choroidal effusion with retinal detachment (n = 1), and acute retinal necrosis with retinal detachment (n = 1) (13). Initial retinal reattachment was achieved in all cases. Complications included redetachment (n = l), cataract (n = 6), raised intraocular pressure (n = 4), hypotony (n = 4), keratopathy (n = 3), uveitis sjme-chia formation (n = 3), phthisis (n = 2), choroidal hemorrhage (n — 1), and vitreous hemorrhage n = 1). 

The use of intravitreal corticosteroids was first popularized by Machemer in 1979 (33) in an effort to halt cellular proliferation after retinal detachment surgery, and Graham (34), McCuen (35), Tano (36), and others have studied its use in both animal models and humans. In contrast to other corticosteroids with short half-lives following intravitreal injection, triamcinolone acetonide is an effective and well-tolerated (35,37) agent for intravitreal injection in conditions such as uveitis (38,39), macular edema secondary to ocular trauma or retinal vascular disease (40), proliferative diabetic retinopathy (41), intraocular proliferation such as proliferative vitreoretinopathy (42), and choroidal neovascularization from AMD (43,44). 

Despite the recent development of microsurgical techniques, intraocular surgery can still fail because of postoperative complications, such as fibrin formation and proliferative vitreoretinopathy (PVR). Fibrin formation tends to be more severe in eyes with increased vascular permeability after vitrectomy in endophthalmitis, proliferative diabetic retinopathy... 

Disorders of the posterior segment of the eye are particularly difficult to treat. The efficient clearance mechanisms at the front of the eye reduce the concentrations of drug able to diffuse to the back of the eye. Futhermore, many of these disorders are chronic conditions, requiring continuous therapy. The diseases of the back of the eye include Cytomeaglovirus retinits (CMVR), Proliferative vitreoretinopathy (PVR), diabetic retinopathy, age-rated macular degeneration, endophthalmitis and retinitis pigmentosa. 

Fredj-Reygrobellet D, Baudouin C, Negre F, Caruelle JP, Gastaud P, Lapalus P. Acidic FGF and other growth factors in preretinal membranes from patients with diabetic retinopathy and proliferative vitreoretinopathy. Ophthalmic Res 1991 23 154-161. 

Figure 1 Schematic diagram of the eye in horizontal section indicating each ocular component, a, corneal epithelium b, keratocyte c, corneal endothelium d, aqueous humor e, conjunctiva /, sclera g, trabecular meshwork h, iris i, lens /, ciliary zonule and body k, vitreous /, retina m, interphotoreceptor matrix n, retinal pigment epithelium o, Bruch s membrane p, choroid q, optic nerve head r, lamina cribrosa extraocular muscles and tissues. The candidate glycosaminoglycans involved in the ocular components of each eye disease described in this chapter are as follows macular corneal dystrophy (b, c KS, CS/DS, HA), glaucoma (d HA g CS/DS, HS, HA q, r CS, HS, HA), cataract r. CS/DS, HS, HA), diabetic retinopathy (fc HA / HS), retinal detach-ment/proliferative vitreoretinopathy k, I, m, n CS/DS, HS, HA), myopia (f, p CS), thyroid eye disease (s CS, HA), pseudoexfoliation syndrome (c, d, g, h, i, j KS, CS/DS, HA). KS, keratan sulfate CS/DS, chondroitin sulfate/dermatan sulfate HS, heparan sulfate HA, hyaluronan.

CS/DS Macular corneal dystrophy, glaucoma, cataract, retinal detachment/proliferative vitreoretinopathy, myopia, thyroid eye disease, pseudoexfoliation syndrome HS Glaucoma, cataract, diabetic retinopathy, retinal detachment/proliferative... 

On the other hand, the maximum tolerated dose of enoxaparin, a low-molecular-weight heparin, during vitrectomy for rhegmatogenous retinal detachment with proliferative vitreoretinopathy and severe diabetic retinopathy was determined (103). The study was able to achieve the 6.0 lU/ml maximum dose in the infusion fluid, and enoxaparin dose escalation did not result in a dose-dependent increase in acute side effects. 

This chapter (27 pages) presents the modern concepts in the pathophysiologic mechanisms of vitreous diseases, and in the clinical conditions involving the vitreous (detachment, macular holes and membranes, diabetes, proliferative vitreoretinopathy, hyalosis, amyloidosis). Aspects such as separation of the vitreous from the retina and traction of the vitreous by hypocellular gel contraction are explained according to the most recent findings. 

---