PROLIFERATIVE
retinopathy--changes may occur in the presence or absence of clinically
visible background diabetic retinopathy.
Neovascularization and fibrous tissue proliferation occur in
response to hypoxia and may arise on the optic disc (NVD) (#22044) or
elsewhere (NVE) (#9366). New
vessels arise from primitive mesenchymal elements which can then undergo
fibrous metaplasia. Associated changes include retinal wrinkling, macular
heterotropia, thickening and detachment of the posterior hyaloid membrane.
Ultimately, one may get traction from the contracting vitreous body
which has become adherent to the retina via a pre-retinal fibrovascular
membrane(#22047), thus producing vitreous hemorrhage(#22045) (which may
fill the vitreous, directly overlie the macula, or promote formation of a
dense posterior hyaloid membrane over the macula) and/or retinal
detachment.
Diabetes
may also cause changes in OTHER AREAS of the eye. Ischemia may lead to the formation of neovascularization on
the iris which is also called rubeosis iridis.
Pathologically, this is characterized by proliferation of
fibrovascular tissue on the anterior-most surface of the iris(#22050,
#22048). As this tissue
contracts, it may cause eversion of the iris pigment epithelium and
sphincter muscle at the pupillary margin causing ectropion uvea.
This fibrovascular tissue may also grow from the surface of the
iris to the area of the trabecular meshwork in the anterior chamber angle
causing a peripheral anterior synechiae (PAS) and neovascular glaucoma.
In addition, the iris pigment epithelium may show small empty
spaces or lacy vacuolization. Histopathologic
examination of the ciliary body reveals a characteristic diffuse
thickening of the basement membrane of the innermost pigmented ciliary
epithelium(#22053). In
addition, choroidal vessels may also show a diffuse thickening of their
walls. The periodic acid-Schiff
(PAS) stain is an excellent way to look for thickened basement membranes
and vessels.
TREATMENT
of proliferative diabetic retinopathy consists predominantly of panretinal
laser photocoagulation (#22054, #22056).
Panretinal laser is thought to decrease retinal ischemia and thus
lead to regression of retinal neovascularization.
Prompt laser photocoagulation may prevent such complications of
proliferative retinopathy as vitreous hemorrhage and tractional retinal
detachments. Histologically,
areas of laser treatment show a characteristic scar with closure of the
choriocapillaris, disruption of the retinal pigment epithelium, and some
focal loss of the outer layers of the retina(#22057).
-See also
(#22892, #22895, #23174, #23177, #46515) for other slides of
neovascularization.
-(#22904,
#23162)both show micro-aneurysms which often are seen in diabetic
retinopathy. -(#23165) is a
slide showing hard exudates secondary to diabetes.
-(#23192)
shows pre-retinal hemorrhage with neovascularization.
