THE UVEA:
Dr. Ziyad K. Aljenabi
Anatomy of Uveal tract:
The middle layer of the eye, the uva (uveal tract), is composed of three
regions (from front to back): the iris, ciliary body, and choroid. The uvea
sometimes is called the vascular layer because its largest structure, the
choroid, is composed mainly of blood vessels, which supply the outer retinal
layers.
The IRIS It is the anterior part of the uveal tract , it is like a diaphragm that
contain central aperture named (pupil ).
Muscles: sphincter pupillae: it is a circular fibers around the Pupillary border
of the iris supplied by (Para sympathetic fibers of 3rd cranial nerve), dilator
pupillae: radially arranged fibers extending from the root of iris, it is supplied
by sympathetic nerve fibers. Sensory nerve supply of iris: Long ciliary nerve
from naso ciliary branch of 5th cranial nerve. Blood supply by: Anterior
ciliary arteries which are branches of muscular arteries and the 2 long
posterior ciliary arteries.Function of iris: It control the amount of light
entering the eye.
The CILIARY BODY It is the intermediate between root of iris and choroid, it
is triangular in shape , the base (anterior) is continuous with iris root and
trabecular meshwork , the apex(posterior) is continuous with the choroid. It
consist of two parts: a/ anterior part (pars plicata ): it carries about 70
ciliary processes, b/ posterior part( pars plana ): it is smooth and ends at orra
serrate.The ciliary body contain ciliary muscle which is divided into 3 parts:
longitudinal, circular and radial parts.
functions:
1- secretion of aqueous humor from ciliary processes. 2- suspension of
crystalline lens by zonular fibers (zonules of zinn). 3- process of
accommodation by contraction of ciliary muscle. 4- help in drainage of aqueous
humor by contraction of longitudinal fibers of ciliary muscle.
The CHOROID extends from the ora serrata to the optic nerve and is located
between the sclera and the retina, providing nutrients to outer retinal layers.
It consists primarily of blood vessels. However, a thin connective tissue layer
lies on each side of the stromal vessel layer.
Developmental anomalies:
1- coloboma :
Results from defect in closure of optic cup during embryonic
closure of embryonic fissure ,it varies from mild defect that is affecting iris
only to a severe defect involving iris ,ciliary body ,choroid , retina and optic
disc. Clinical features: For mild defect :no symptoms only (keyhole) sign pupil,
For severe defect: poor vision
2- aniridia :
It means loss of iris tissue which is either partial or total, it is
either sporadic, autosomal recessive or dominant. In sporadic type, it is
associated with WILMS Tumor kidney and genitourinary problems so when see
aniridia we must examine other members of family, D.N.A analysis and radio
imaging to find if kidney is affected. Clinical features: Photophobia
,nystagmus, cataract , glaucoma , poor vision if associated with disc and foveal
hypoplasia.
3- heterochromia :
It is difference in Colour of 2 iris (one is hypo
pigmented and other is hyper pigmented ), it is usually benign condition, no
treatment is required. Differential diagnosis: congenital Horner syndrome,
siderosis, malignant growth
Tumors of uveal tract:
1- iris: naevus ,malignant melanoma.
2- ciliary body: malignant melanoma, leiomyoma.
3- choroid: naevus , malignant melanoma and haemangioma, metastatic tumors.
Choroid naevus:
It is present in about 5-10% of Caucasians but it is very rare
in dark skinned races. In the vast majority ,it is asymptomatic and discovered
by routine examination
Choroidal melanoma: It is the most common primary intraocular malignancy in
adult and it account for 90% of all uveal melanoma ,its peak incidence at 60
years old, it may be asymptomatic and detected accidentally, or symptomatic
presented with decreased vision, metamorphopsia , visual field defect , It is
presented as elevated ,sub retinal dome shape ,pigmented or non-pigmented
mass. Treatment :1- surgical enucleation and even exenteration. 2-
radiotherapy
Choroidal haemangioma: Could be circumscribed or diffuse. The diffuse type
is associated with STURGE-WEBER Syndrome .it is seen as red shaped tumor
in the posterior pole
Metastatic tumors: Breast cancer is the commonest in females while CA. of
bronchus is the most common primary site in males. it present as creamy white
swelling in posterior pole .Treatment: Radiotherapy, chemotherapy and
enucleation.
Uveitis:
Definition:
it is an inflammation of the uveal tract (Iris, Ciliary body and
choroid) and adjacent structures, most probably the retina.
Classifications:
- Anatomical. - Clinical. - Aetiological.
Anatomical Classification:
1- Anterior uveitis: which is subdivided into:
a- Iritis: in which inflammation predominantly affects the iris.
b- Iridocyclitis: in which both the iris and anterior part of the ciliary body
(pars plicata) are equally involved.
If the number inflammatory cells was equal in both the aqueous and vitreous, it
is iridocyclitis, while if the number was larger in aqueous, it is iritis.
2- Intermediate uveitis: It is characterized by involvement predominantly of
the posterior part of the ciliary body (pars plana), periphery of the retina
and the underlying periphery of the choroid.
3- Posterior uveitis: Inflammation of the choroid and retina posterior to the
equator of the eye.
4- Panuveitis: Involvement of the entire uveal tract.
Clinical classification:
1- Acute uveitis: usually has a sudden, symptomatic onset and persists for up
to 3 months. If the inflammation recurs following the initial attack it is
referred as recurrent acute uveitis.
2- Chronic uveitis: the onset is frequently insidious and may be asymptomatic.
It usually persists for longer than 3 months. Acute or subacute exacerbations
on chronic may occur.
Aetiological classification:
1- Idiopathic: which forms more than 50% of cases of uveitis.
2- Associated with a systemic disease, e.g.:
a- Spondyloarthopathies: ankylosing spodylitis, Reiter's syndrome, psoriatic
arthritis and chronic juvenile arthritis.
b- Inflammatory bowel disease: ulcerative colitis, Crohn's disease,
Whipple's disease.
c- Nephritis.
d- Non-infectious multi-system disease: sarcoidosis, Behçet's disease.
e- Infectious systemic disease: e.g. TB, syphilis
f- Diabetes.
3- Infections:
a- Bacterial: tuberculosis.
b- Fungal: Candidiasis.
c- Viral: Herpes Zoster.
4- Infestations:
a- Protozoa: Toxoplasmosis.
b- Nematodes: Toxocariasis.
Anterior uveitis:
Symptoms:
1- Acute anterior uveitis: Photophobia, pain, redness, decreased visual acuity
and lacrimation.
In acute anterior Uveitis, the pain is due to spasm of ciliary muscle, and
decrease visual acuity is due to turbidity of aqueous by inflammatory cells,
leakage of proteins which are present due to break down of blood-aqueous
barrier. There may be normal or increased IOP (if the angle are closed by cells
and proteins), but more commonly is decreased IOP or hypotony due to ciliary
shutdown.
2- Chronic anterior uveitis: may be asymptomatic or give rise to mild redness
and the perception of floaters.
Signs:
1- Circumcorneal injection: acute anterior uveitis has a violaceous hue.
2- Keratic precipitates: deposition of inflammatory cells into corneal
endothelium. Their characteristics and distribution may indicate the probable
cause of uveitis.
3- Cells: indicative of acute inflammation: it is graded from grad 1 to grad 4
according to the number of these cells.
a- Aqueous cells. b- Anterior vitreous cells.
4- Aqueous flare: is seen due to scattering of light by proteins that have
leaked into aqueous humour by break down of blood-aqueous barrier. It is
graded from 1 to 4 according to its haziness or obscuration to the details of
iris.
5- Iris nodule: which is a feature of chronic granulomatous inflammation.
Complications of anterior uveitis:
1- Posterior synechiae: 360° (seclusio pupillae) causes iris bombé that leads to
closure of the angle of anterior chamber and ends with secondary angle
closure glaucoma.
2- Cataract.
3- Glaucoma: inflammatory or secondary angle closure glaucoma.
4- Cyclitic membrane formation which leads to traction and then detachment
of the Ciliary body which causing phthisis bulbi
Intermediate Uveitis:
Symptoms: Initially, floaters (inflammatory cells in anterior vitreous) and
later, decreased visual acuity due to macular edema (due to associated
vitritis).
Signs: Cellular infiltration of vitreous (vitritis).
Complications:
1- Cystoid macular oedema if there is chronic macular edema.
2- Cyclitic membrane and phthisis bulbi.
3- Cataract.
4- Tractional retinal detachment duo to vitreous gliosis and fibrosis.
Posterior uveitis:
Symptoms:
1- Floaters (due to cells and flare in the vitreous).
2- Impairment of visual acuity (due to macular oedema).
Signs:
1- Cells, flare, opacities and posterior vitreous detachment: inflammatory
process of vitreous (vitritis) leads to its shrinkage and then separation of
posterior vitreous face from the retina (posterior vitreous detachment).
2- Retinitis: ill-defined, focal, white, cloudy appearance of retina with
obscuration of retinal vessels.
3- Vsculitis: acute vasculitis, which is characterized by a fluffy white haziness
surrounding the blood column.
Complications:
1- Cystoid macular oedema.
2- Macular ischaemia.
3- Epiretinal membrane formation.
4- Vascular occlusion.
5- Retinal detachment (exudative or tractional).
6- Consecutive optic neuropathy (due to ischaemia that affects the ganglion
cells layer, nerve fiber layer and the optic disc itself).
Special investigations for patients with uveitis:
1- X-Ray:
- Sacroiliac joint (for ankylosing spondylitis).
- Chest x-ray (for TB and sarcoidosis).
- Skull calcification: toxoplasmosis.
2- Skin test: histoplasmosis, Mantoux and kveim (sarcoidosis).
3- Serum tests: ANA (Anti-Nuclear Antibodies) as in chronic juvenile
arthritis, VDRL, toxoplasmosis test (IFAT) and ELISA.
4- HLA-typing: HLA-B27 for ankylosing spondylitis and B5, B51 for Behçet's
disease.
Treatment:
1- Mydriatics and cycloplegics:
Short acting:
Tropicamide 0.5% (for <1y) & 1% (for > 1y), the duration of action is 6 hours.
Cyclopentolate 0.5% (for <1y) & 1% (for > 1y), the duration of is 24 hours.
* Both of previous drugs have mydriatic and cycloplegic effects by inhibiting
the sphincter muscles of the iris and inhibition of Ciliary body muscles through
its parasympatholytic action.
Phenylnephrine (sympathetic agonist) 2.5% (up to 16y) & 5%, 10% (adult), the
duration of action is 6 hours, but has no cycloplegic effect. It causes
dilatation of the pupil by stimulation of radial muscles of the iris
(sympathomimetic action). Cautious should be taken when using this drug, as
it elevates blood pressure and causes tachycardia.
Long acting:
Atropine 0.5% (for <1y) & 1% (for > 1y), it is the most powerful cycloplegic
and mydriatic, its duration of action is 2 weeks.
Advantages of using mydriatic and cycloplegic drugs:
a- To promote comfort through muscles paralysis (except phenylnephrine).
b- To prevent formation of posterior synechiae through continuous movement
of the pupil and getting the pupillary margin away from convexity of lens
center.
c- To break down recently formed synechiae.
d- stabilize blood aqueous barrier and decrease inflammation specially
atropine(except phenylnephrine).
2- Steroids:
Topical steroids: only for anterior uveitis, because they do not reach
therapeutic levels behind the lens.
Potent steroids are: prednisolone acetate, Dexamethasone and betamethasone.
Side effects of topical steroids (especially after prolonged use):
a- Rising IOP and Glaucoma.
b- Cataract.
c- Corneal complications: they are rare, e.g. bacterial and fungal keratitis and
recurrence of herpes simplex keratitis.
d- Systemic side effects.
Periocular injection of steroids(sub Tenon's)
Indications:
a- Severe acute anterior uveitis.
b- As an adjunct to topical or systemic steroid in resistant cases.
c- Intermediate uveitis
d- posterior uveitis.
e- Poor patient compliance with topical or systemic steroids.
Intravitreal injection of steroids:
Injection of triamcinolone acetonide (2mg in 0.05ml) in resistant uveitic
chronic cystoid macular oedema. Increase IOP is common side effect of
intravitreal injection of steroid.
Systemic steroids:
Either orally: prednisolone tablets
Or as injections: Adrenocorticotrophin hormone (ACTH) if the patient is
intolerant to oral steroids.
Indications:
a- Intractable anterior uveitis resistant to topical and periocular steroids.
b- Intermediate uveitis unresponsive to preiocular injection.
c- Posterior ueveitis or panuveitis, particularly with severe bilateral
involvement.
3- Immunosuppressive agents:
Either Antimetabolites (cytotoxic) as Azathioprine and Methotrexate, Or T-
cell inhibitors as ciclosporin A.
Indications:
a- Sight (vision)-threatening uveitis:
Which is usually bilateral, non-infectious and has failed to response to
adequate steroid therapy.
b- in patients with intolerable side effect from systemic steroids.
1, 2 and 3 are used to treat cases with undetected etiology (idiopathic).
But if we find a cause, so the treatment is by 1, 2, 3 in addition to:4
4- Treatment of underling cause.
e.g. TB, syphilis, toxoplasmosis, toxocariasis, ect.
ﺎﺑﻲــــــﻨﳉﺍ ﻞﻣﺎﻛ ﺩﺎـــــﻳﺯ .ﺩ
F.A.B.Ophth , F.I.C.O , V.R.S, M.B.ch.B