Uveitis Intro

Someone mentioned Uveitis the other day and I realised that I didn't remember much about it save that it was inflammation of the uveal tract and caused a painful red eye, reduced VA and photophobia. So i'm going to learn a bit more about it.

In fact the term uveitis is now used to describe all kinds of ocular inflammation involving the uvea (choroid [between retina and sclera], iris, ciliary body [connects iris to choroid and includes ciliary muscles which change shape of lens]) and adjacent structures. It's classified anatomically, clinically and aetiologically (is that even a word?).

Anatomical Classification

• Anterior uveitis - Iritis or iridocyclitis where the anterior part of the ciliary body is equally involved
• Intermediate uveitis - posterior part of ciliary body, extreme periphery of the retina and the underlying choroid
• Posterior uveitis - inflam. of the choroid and retina posterior to the vitreous base
• Panuveitis - entire uveal tract

Clinical Classification

• Acute - sudden, symptomatic onset. Persists up to 3 months. If inflammation recurs following the initial attack then it's 'recurrent acute'
• Chronic - persists for longer than three months, with a more insidious asymptomatic onset. Acute/subacute exacerbations may occur though

Aetiological Classification

Exogenous uveitis is caused by external injury to the uvea or invasion by micro-organisms. Endogenous uveitis is caused by micro-organisms or other agents from within the patient.

• Assoc. w/systemic disease
• Infections w/bacteria (tuberculosis), fungi (candidiasis) & viruses (herpes zoster)
• Infestations w/protozoa (toxoplasmosis) or nematodes (toxocariasis). Worms!
• Idiopathic specific uveitis entities - group of unrelated disorders w/underlying system disease that need special descriptions of their own (Fuch's uveitis syndrome)
• Idiopathic non-specific uveitis entities - none of the above. 25% of cases.

ANTERIOR UVEITIS

Symptoms

Acute a.u. - photophobia, pain, redness, decreased vision, lacrimation
Chronic - asymptomatic, mild redness, perception of floaters

Signs

1. Circumcorneal (ciliary) injection in acute a.u. which may have a purple/blue hue

1. Keratic precipitates - cellular deposits on the corneal endothelium, most commonly form in mid and inferior zones of cornea thanks to convection currents in the ant. chamb. In Fuchs uveitis they're scattered throughout the endothelium.

• Endothelial 'dusting' - acute/subacute chronic
• Medium sized - most types of acute & chronic
• Large 'mutton fat' greasy/waxy. In graulomatous uv.
• Old KP are pigmented and may develop a 'ground glass' appearance

1. Cells

• <5>
• 5-10 = +1
• 11-20 = +2
• 21-50 = +3
• >50 = +4
• Hypopyon
• If you compare aq. cells with those of the ant. vitreous they should far exceed the number of vitreous cells if it's iritis.

1. Aq flare - due to scattering of light by proteins that have leaked into the aq humour thru damaged iris bv. On its own in absence of cells not indicative of active inflammation and doesn't need treatment. Faint/moderate/marked/intense.

1. Iris Nodules - feature of granulomatous inflammation

• Koeppe nodules - small, @ pupillary border
• Busaca - less common, away from the pupil

Anterior uv can result in complications. Posterior synechiae are adhesions between the iris and the anterior lens capsule which may form in acute a.u. or moderate to severe chronic a.u. If the synechiae go 360 degrees around then they prevent passage of aq humour from the posterior to the anterior chamber and you get iris bombé where the iris looks all stretched and bowed outwards. This in turn can lead to closure of the anterior chamber angle by the peripheral iris with 2ary elevation of the IOP. Glaucoma! Other complications include cataract and macular oedema.

INTERMEDIATE UVEITIS

Initially px sees floaters and later VA is impaired due to cystoid macular oedema. A sign of I/uv is cellular infiltration of the vitreous with fewer cells in the ant. chamb. Complications include cystoid macular oedema, cyclitic membrane formation and tractional retinal detachment.

POSTERIOR UVEITIS

Px sees floaters and vision is impaired. Visual impairment is minimal if the inflammatory lesion is in the periphery. On the other hand if it's in the fovea central vision will be lost and the patient won't notice floaters.

Signs

• Vitreous - cells, flare, opacities, PVD. Posterior hyaloid face may have inflammatory precipitates comparable to KP.
• Retinitis - retina has a white cloudy appearance with obscuration of retinal vessels. The outline of the inflammatory focus is indistinct so it's hard to tell where affected retina ends and healthy begins.
• Choroiditis - Deep, yellow or greyish patches with well demarcated borders. Inactive (old) lesions appears as white well defined areas of chorioretinal atrophy with pigmented borders
• Vasculitis - most commonly involves retinal veins and less commonly arteries. You get a fluffy white haziness surrounding the blood column and extending outside the vessel wall.
• Spill over anterior uveitis is common.

Complications

• Direct involvement of the macula (macular inflammation), cystoid macular oedema, macular ischaemia, epiretinal membrane formation, vascular occlusions, choroidal neovascularisation, retinal detachment and consecutive optic neuropathy. IE IT IS SERIOUS

Posterior uv can be focal w/ one lesion like in toxoplasmosis, multifocal like birdshot retinochoroidopathy or geographical in which there's a large confluent area of inflammation eg cytomegalovirus retinitis.

TREATMENT

This centres around preventing vision threatening complications, relieving discomfort and treatment of the underlying problem if possible. The drugs used these days are mydriatics, steroids and systemic immunosuppresive agents. Uv that is due to an infection should be treated with the appropriate antimicrobial or antiviral drugs.

1. Mydriatics

Short acting ones include tropicamide 0.5% and 1.0% w/duration of 6hrs, cyclopentolate 0.5% and 1.0% w/duration of 24hrs and phenylephrine 2.5% and 10% which lasts for three hours and doesn't have any cycloplegic effects like thee other twoo doo. Atropine is the sole long acting mydriatic used (1%) and the most powerful, lasting for two weeks.

These are indicated to promote px comfort - relieving spasm of the ciliary muscle and pupillary sphincter. Atropine is used but mostly only once - if after two weeks the inflammation appears to be subsiding then you can sub it for a short acting mydriatic. Short acting mydriatics are used to prevent the formation of posterior synechiae. They keep the pupil mobile so there's less chance of it adhering to the anterior surface of the lens cap. In mild cases it's best to instil the drug before bedtime to prevent difficulties during the day. Also the pupil shouldn't be constantly dilated by these drugs as pos. syn. can still occur if the pupil is dilated and stationary. NB in kids constant uniocular atropinization may cause amblyopia. You can also use atropine or phenylephrine to break down recently formed pos. syn. Subconjunctival injections of mydricaine are also used for that purpose.

2. Steroids

These are the main treatment for this sorta thing. They can be administered topically, by periocular injection, intravitreal injection or systemically. They should generally be started @ a high dose which is tapered as the inflammation becomes under control.

Topical steroids are only useful for ant. uv. They don't reach therapeutic levels beyond the lens. Stronger steroids like dexamethasone and prednisolone are better than wekaer ones like fluorometholone. A solution penetrates the cornea better than a suspension or ointment, although ointment can be inserted at bedtime. The frequency of instillation depends on severity. It varies hugely - from one drop every five minutes to one every other day.

Treatment of acute a.n. is relatively simple. Administration is initially very frequent (like every 15 minutes) and then tapered to q.i.d after several days. Once the inflammation is well controlled the freq is reduced to one drop a week and then discontinued altogether after five or six. Treatment of chronic is more difficult because the inflammation can last for months or even years. Acute exacerbations are treated in the same way as normal acute a.u. Following treatment the px should be examined after a few days to ensure the uv hasn't recurred.

Complications of the topical steroids include glaucoma, cataract, 2ary infection of cornea (uncommon), corneal melting (uncommon) and systemic side effects following prolonged administration, especially in children.

Periocular steroid injections

These allow therapeutic concentrations to be acheived behind the lens. Water soluble drugs that can't normally penetrate the cornea can enter the eye trans-sclerally via this method. A longstanding effect can be achieved with preps like triamcinolone acetonide or methylprednisolone. Injections are indicated in severe acute a.u. especially in px w/ankylosing spondylitis w/exudate in ant chamb/hypopyon. They are also used as an adjunct to topical or systemic therapy in resistant chronic a.u, intermediate uv, px w/poor compliance and at the time of surgery in eyes with uveitis.

First the conjunctiva is anaesthetised with a topical anaesthetic such as amethocaine at one minute intervals for five minutes, then a cotton bud with the same stuff on it is placed into the conj sac at the site of injection and left there for five minutes. The injection can be at the anterior or posterior sub Tenon.

Intravitreal Injection

Under review. Has been used successfully in resistant uveitic chronic cystoid macular oedema.

Systemic Therapy

Oral prednisolone 5mg is the main one. Indicated when the anterior uveitis is intractable - resistant to topical therapy and injections. Also for intermediate uv which has not responded to posterior sub-Tenon injections and certain types of posterior and panuveitis particularly those with severe bilateral involvement. Again it's a case of 'start with a large dose and then reduce'. A reasonable start is 1mg/kg/day in a single morning dose. If steroids are given for less than two weeks a gradual reduction isn't required.

The side effects depend on the duration of administration. Short term you may get dyspepsia, mental changes, electrolyte imbalance and rarely hyperosmolar hyperglycaemic non ketotic coma. Long term could cause osteoporosis, limitation of growth in children, reactivation of stuff like TB, cataract and increase in severity of existing conditions like diabetes and myopathy.