Page 276 - WSAVA2018
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 25-28 September, 2018 | Singapore
Optimal treatment relies upon identification and removal or reduction of the causative antigen; however this is rarely possible. Additionally, all patients with uveitis need their intraocular inflammation controlled rapidly and completely, since it is painful and produces vision- threatening sequelae. Thus, immunomodulating drugs form the mainstay of therapy for uveitis. The major decisions are therefore which immunomodulating drugs should be given, via what route and, at what dose.
Immunomodulatory therapy
Corticosteroids are commonly used for uveitis. Their systemic use should be reserved until a definitive cause responsive to corticosteroids has been found
or, failing this, until causes known to be worsened by glucocorticoids have been adequately eliminated. In particular, the systemic mycoses must be adequately eliminated as potential causes. Likewise, patients in which lymphoma is possible and which would benefit from a multidrug chemotherapeutic regimen should
not be treated with systemic corticosteroids alone.
By contrast, topical administration of corticosteroids may be employed safely even when an infectious or neoplastic cause might prevent systemic administration of the same drugs. Prednisolone acetate (1% or
0.125%) and dexamethasone (0.1%) will penetrate
intact corneal epithelium and reach the anterior uveal tract. Hydrocortisone (as found in many combined antibiotic–corticosteroid ophthalmic preparations)
does not penetrate intraocularly and should not be used. The frequency of application should be tailored
to the severity of the uveitis; starting as frequently as
q 2 hours and tapering as a clinical response is noted. When safe, corticosteroids should be administered systemically for posterior uveitis and when more significant immunomodulation is necessary, or when corneal ulceration prohibits their topical use. Typical doses of prednisolone range from 1 mg/kg q 12 hours when notable inflammation is present to 0.5 mg/kg once daily when a more moderate anti-inflammatory effect is desired. As with topical corticosteroids, dose and dose frequency of systemically administered glucocorticoids should be carefully reduced based entirely upon clinical evidence of waning disease.
Compared with corticosteroids, non-steroidal anti-inflammatory drugs (NSAIDs) are not immunosuppressive, and may be more expensive, sold in smaller volumes (as topical ophthalmic solutions),
and sometimes unavailable in ointment form. These limitations must be borne in mind for dogs and cats
with uveitis; however they may be preferred over corticosteroids in patients with diabetes or other endocrinopathies in which corticosteroid use may not be wise. They can also be administered systemically instead of corticosteroids when systemic infectious disease
is suspected or proven, or until lymphosarcoma is
eliminated as a differential consideration. And they may be given in conjunction with a topical steroid. As such, they may make an excellent choice for initial control of inflammation while likely causes are being ruled in or out. The same general comments regarding dose frequency and route made for corticosteroids apply equally to NSAIDs.
Iridocycloplegic agents
Atropine has multiple favorable actions in eyes with uveitis and form a critical component of treatment. It paralyzes the iris sphincter and ciliary body muscles causing mydriasis and cycloplegia, respectively. Pupil dilation reduces leakage of vascular elements into the aqueous humor by causing radial blood vessels within the iris stroma to “concertina” upon themselves (thus providing a physiological tamponade); decreasing iris surface area (from which inflammatory mediators and vascular components originate); reducing uveal vascular endothelial permeability; and by reducing chances
and consequences of posterior synechiation. However “bunching” of the iris in the periphery does increase the chance of anterior synechia and potentially obstruction of the iridocorneal angle. Cycloplegia reduces ocular pain but also increases resistance to aqueous outflow. Therefore, pupil dilation and cycloplegia are desirable in all cases of uveitis except those where secondary glaucoma is present or likely. This is more likely in some dg breeds predisposed to primary glaucoma
but can also occur in cats and non-predisposed dogs The effect of mydriasis upon IOP can be tested by a single application of the short acting drug tropicamide followed by tonometry when the pupil is fully dilated.
If IOP is increased by tropicamide, atropine should not be administered. If atropine is initiated, IOP should be rechecked regularly and application discontinued if IOP increases above normal. In cats, atropine should be applied as an ophthalmic ointment rather than a solution because it is bitter and passage down the nasolacrimal duct can cause violent salivation and frothing that is harmless but disturbing to the cat and its owner.
Monitoring and Sequelae
Prompt specific treatment of uveitis with tapering of therapy based upon reduction of clinical signs may
result in some sequelae but these are usually mild and should be static. If they are not, this suggests chronic or recurrent uveitis and further investigations and treatment are necessary. Classic sequelae include corneal fibrosis, cataract, or posterior synechia. None of these changes should result in pain or, unless severe, vision disturbance. By contrast, more severe, unrecognized, persistent,
or recurrent uveitis frequently results in a blind and sometimes painful globe. The most common sequelae (and their prevalence in cats) include cataracts in 20-36% of eyes, lens luxation in 11-18%, glaucoma in 16-46% and enucleation in 29%. Many patients experience more than

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