ocular diseases

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Management of Ocular Disease in Exotic 
Species 
Nicholas J. Millichamp, B VMed, PhD, Dip.A CVO 
Ophthalmic diseases in exotic species present various 
challenges. Although some conditions are identical to 
those encountered in domestic species, there are condi- 
tions that are unique to particular groups of exotic 
animals. Interspecific differences in ocular anatomy, 
physiology, and the pathological responses of the eye 
influence the type of diseases seen and affect the 
approach to therapy. The stress and risk of injury to the 
animal or care provider associated with repeated re- 
straint for management of ocular disease in exotic 
species make it necessary to use innovative medical 
and surgical treatments whenever possible. 
Copyright �9 1997 by W. B. Saunders Company. 
Key words: Exotic animal, eye disease. 
xotic species offer numerous challenges for 
he veterinarian entrusted with their care. 
This is as true of ocular disease m a n a g e m e n t as 
for any other aspect of the veterinary care of 
these animals, a l though there are certain addi- 
tional considerations which must be accounted 
for with ophthalmic diseases. 
Exotic species may be encounte red in the wild 
or in professional or private collections. The 
situation in which the animal is kept may affect 
the decisions which must be made with regard to 
treating ocular disease. In most cases, animals 
encounte red in the wild are going to be beyond 
the scope of cont inued veterinary supervision 
a l though some a t tempt may be made to facilitate 
the resolution of ocular disease even when the 
animal may only be examined on one occasion. 
In the zoological or private collection, the ani- 
mal may be continually available for therapy 
al though numerous factors will influence whether 
effective therapy can be provided. 
From the Department of Small Animal Medicine and Surgery, 
College of Veterinary Medicine, Texas A & M University, College 
Station, TX. 
Address reprint requests to Nicholas J. Milliehamp, BVMed, 
PhD, Dip.AVCO, Department of SmaU Animal Medicine and 
Surgery, College of Veterinary Medicine, Texas A &M University, 
College Station, TX 77843. 
Copyright �9 1997 by W. B. Saunders Company. 
1055-937X/97/0603-000655.00/0 
The decision to pursue diagnosis and treat- 
men t of ocular disease in exotics will be influ- 
enced by the value and rarity of the animal and 
its purpose. A rare specimen in a zoological 
collection may appear to be a more likely candi- 
date for extensive veterinary care, a l though the 
loss of an eye is insignificant compared with the 
loss of the animal caused by the stress of han- 
dling or immobilization. Conversely, a relatively 
c o m m o n animal in a private collection may be 
more effectively treated because of the concern 
of the owner and the owner 's ability to provide 
intensive nursing in a situation where few exotic 
animals are being kept. 
Typically, the cost and labor involved in treat- 
ing ocular disease in exotics will be greater than 
for their domestic counterparts . The additional 
complications of providing safe restraint or immo- 
bilization and the fur ther cost of special tech- 
niques to deliver drugs or surgery can signifi- 
cantly increase the cost of therapy. In some 
instances, the cost of therapy and safety consider- 
ations for animal and keeper may significantly 
affect the decision to treat an ocular disease. In 
other words, it may be more appropr ia te for the 
animal to incur loss of vision ra ther than jeopar- 
dize the animal or keeper by a t tempting therapy. 
For an animal which can be mainta ined off 
exhibit in a limited space, this may be acceptable 
if the animal has considerable value because of 
its rarity a n d / o r is needed for a captive breeding 
program. 
Many species simply may be too difficult to 
work with to provide any meaningful therapy. 
The size and nature of the animal will largely 
dictate what is safely practical for the animal, the 
keepers, and veterinarian. Even animals that are 
regularly handled may become difficult to evalu- 
ate and medicate when treating ocular disease. 
Conversely, some species with limited vision 
may become too much of a hazard in captivity 
for keepers working with them (eg, one-eyed 
elephants) . 
Some species may function perfectly well 
152 Seminars in Avian and Exotic Pet Medicine, Vol 6, No 3 @ly) , 1997: pp 152-159 
Ocular Disease in Exotics 15 3 
(especially in a limited and known environment) 
with one eye and therefore the decision to treat 
or simply enucleate the diseased eye may be 
influenced by the need for binocular vision to 
function or cosmetic factors for display animals. 
Some animals in confined spaces, particularly 
lower vertebrates which may rely on o ther senses 
to an equal extent with vision, may be able to lose 
both eyes without significantly affecting their 
ability to survive and live useful lives in captivity. 
Animals kept primarily for breeding purposes 
might fall into this category. Conversely, some 
species rely heavily on binocularity for safe move- 
men t in the enclosure and feeding. Species 
which use their eyes extensively in hunt ing live 
prey (for instance, raptors and lizards) may be at 
a significant disadvantage for main tenance in 
captivity and especially when rehabili tation and 
release is desired. 
There are added probiems seen in various 
exotic species with regard to diagnosis and 
therapy of ocular diseases because of differences 
in ocular anatomy compared with domestic spe- 
cies. 1 Some species have evolved modifications of 
the eyelids which make access to the eye difficult. 
In chameleons, the palpebral fissm-e is consider- 
amy reduced in size. Snakes and some lizards 
have eyelids that are completely fused to fo rm a 
tertiary spectacle. The spectacle limits drainage 
of exudate, which may build up benea th the 
spectacle in certain infectious conditions, and 
limits access to the eye for collection of diagnos- 
~tic specimens and effective delivery of topical 
medications. In some species, deep orbits and 
deve lopment of strong extraocular muscles may 
make effective surgical t rea tment of even simple 
corneal lacerations difficult. Even under general 
anesthesia, species such as elephants can retract 
the globe deep into the orbit, making suturing of 
corneal lesions difficult. 
L imi ted knowledge of the compara t ive 
anatomy of the innervat ion of eyelid muscles in 
most nondomest ic species makes nerve blocks to 
paralyze eyelid muscles to allow adequate exami- 
nat ion of the globe a hit-and-miss affair. Aquatic 
exotic species live in an envi ronment which 
effectively precludes any a t tempt at topical appli- 
cation of medications unless they can be kept out 
of water for a per iod of t ime to allow drug 
absorption. 
To fur ther c o m p o u n d the difficulties, some 
ocular diseases in exotics are still very poorly 
understood. I t is for tunate that at least among 
mammals , there are several well-recognized ocu- 
lar diseases shared by domestic species and their 
wild relatives. ~ Diagnostic methods tend to paral- 
lel those carried out in domestic species and 
therapy, may in many cases, be considered an 
empirical shot in the dark. 
Species Variations in Ocular 
Pathological Response 
There are well-documented studies which show 
that among several laboratory species of mam- 
mals, there is considerable variation in the re- 
sponse of the eye to injury. ~-5 The underlying 
basis for this variation is poorly unders tood 
although, apar t f rom anatomical differences, 
there are definite biochemical differences in the 
ocular response. It is well known that the types of 
inf lammatory mediators p roduced in different 
species appear to have different roles and signifi- 
cance in the response of the eye to irritation. 
The ocular irritative response and deve lopmentof uveitis in response to ocular injury varies 
considerably in different species. This has a 
p ro found influence on the type of inf lammatory 
response which might be expected to accom- 
pany corneal or intraocular surgery. The capac- 
ity of the cornea to heal also varies considerably. 
Feline and bovine corneas appear to be more 
resilient to inf lammation and bacterial infection, 
whereas the canine and equine corneas are more 
p rone to severe ulceration associated with bacte- 
rial infection. 
The presence of striated iris sphincter muscles 
in birds and reptiles requires that drugs other 
than parasympatholytic agents be used to achieve 
ei ther diagnostic or therapeutic mydriasis. Drugs 
such as non-depolarizing neuromuscular block- 
ing agents (vecuronium, d-tubocurarine) have 
been used for this effect diagnostically, a l though 
no studies have been carried out to assess their 
efficacy in achieving mydriasis in the inf lamed 
eye. In reptiles with spectacles, the only effective 
means to achieve mydriasis is ei ther by intracam- 
eral injection of the neuromuscular blocking 
agent or use of general anesthesia to induce 
centrally media ted mydriasis. 
154 Nicholas J. Millichamp 
Restraint 
To conduct an eye examination, the animal 
must be effectively restrained. Some species can 
be trained to accept diagnostic procedures with- 
out becoming stressed (for instance, elephants). 
Repeated handling and application of even bland 
eye drops such as artificial tears or antibiotics in 
some species which are awaiting surgery may 
facilitate the application of ocular medications 
after surgery. This has tt~e added benefit of 
allowing the clinician to determine how trau- 
matic (for the animal and the clinician) the 
postoperative period is likely to be. Use of 
manual restraint of small species or crushes for 
larger animals may allow enough of a view of an 
eye to make a preliminary diagnosis. Binoculars 
or viewing scopes enable an excellent view of the 
lids, cornea and even anterior uvea in eyes of 
exotics which are either, likely to be severely 
stressed by restraint or which may present a 
hazard to keepers and veterinary staff. 
Ultimately, most exotic species require some 
degree of chemical restraint to conduct a com- 
plete ocular examination (including slit-lamp 
biomicroscopy, tonometry and indirect ophthal- 
moscopy). In some cases, animals in the collec- 
tion without ocular disease have had to be 
restrained and examined where uncertainty ex- 
isted as to the normal state; this may particularly 
apply with funduscopic examination where subtle 
retinal degenerat ion may be difficult to differen- 
tiate from the normal variation which often 
exists in the fundus. Details of restraint methods 
are available elsewhere. 6 Once the animal is 
restrained, it may be necessary to block the 
innervation to the orbicularis oculi muscle, in 
species where this is present, to perform a 
reasonable examination. This applies to species 
with a strong lid closure reflex. Landmarks for 
the course of the auriculopalpebral or palpebral 
branches of the facial nerve may be similar to 
those in domestic species. 7 Alternatively, infiltra- 
tion of local anesthesia in a ring adjacent to the 
latter and upper part of the eyelid part way 
between the lateral canthus and ear may block 
orbicularis innervation adequately to enable ex- 
amination. 
The clinician should select therapeutic agents 
which are safe enough to be repeated in short 
intervals when animals cannot be medicated 
without chemical restraint. Chemical agents 
should preferably not result in increased tone to 
the lids because this may limit visual access to the 
cornea and intraocular structures. Miosis is an 
undesirable effect of some anesthetic or sedative 
agents and should be avoided. Fortunately, in 
felids, ketamine provides a well-dilated pupil and 
does not interfere with other autonomic mydri- 
atic agents. Avoid drugs that elevate intraocular 
pressure because these may result in a false 
diagnosis of glaucoma or may promote corneal 
perforation in eyes with deep corneal ulceration. 
Wherever possible, the restraint must have a 
smooth induction and recovery. Any degree of 
excitement during these events may result in loss 
of a delicate eye. 
Principles of Ocular Therapy 
There are certain principles of therapy for 
ocular disease which must be borne in mind 
regardless of the nature of the patient or its 
anatomical or physiological peculiarities. In recal- 
citrant exotic patients, various approaches are 
used to achieve these principles. 
Topically applied drugs require adequate con- 
tact time between the drug and eye for ocular 
absorption. This can be enhanced by increasing 
the time that the drug remains in the conjuncti- 
val sac through modifications of the formulation 
(for instance, use of ointments rather than solu- 
tions that are rapidly lost through the nasolacri- 
real duct) or by increasing the concentration of 
the drug or the frequency of its application to 
the eye. Many ocular conditions require topical 
applications of drugs at least every 6 hours to 
maintain adequate ocular concentrations. In 
some situations (for instance, severe corneal 
ulceration), application of hourly topical antibi- 
otics may be required. This may be impossible in 
fractious or easily stressed exotics. 
Ointments may be preferred as a means to 
prolong contact time and to reduce the dilution 
effect from the tears and washout into the 
lacrimal duct. Many ophthalmic medications are 
commercially available in ointment formula- 
tions. The frequency of medication with oint- 
ment will still need to be at least three to four 
times daily. Ointments are less easily fortified (in 
concentration) than solutions. 
Both erodible and nonerodible polymeric 
inserts have been developed for use in man. 
These inserts are flexible, elliptical structures 
Ocular Disease in Exotics 155 
that are placed in the conjunctival fornix and 
that contain a drug which is released slowly over 
a per iod of several hours, s In animals, problems 
may be associated with the re tent ion of these 
inserts, especially if placed benea th the nictitans. 
The range of drugs available are also limited 
(primarily pi locarpine for glaucoma therapy and 
carboxymethylcellulose for keratoconjunctivitis 
sicca). 
Hydrophil ic soft-contact lenses may be used to 
concentrate and act as slow-release reservoirs for 
ophthalmic drugs. Soaking a contact lens in a 
water2soluble drug solution before application to 
the cornea can enhance contact time between 
the drug and cornea. This has particular value in 
administer ing topical fortified antibiotics. Vari- 
ous sizes of contact lens are now available for 
dogs and horses which may be used in exotic 
species or comparable eye size (eg, Biolens, 
N N Q Inc, Diamond Springg, CA). 
Collagen shields (eg, Bio-Cor Collagen Shields, 
Bausch and Lomb, Tampa, FL) have been devel- 
oped for use in man (and to a more limited 
extent in domestic animals). Various antibiotics 
and ant i- inf lammatory drugs have been applied 
to the eye with a corneal collagen shield in place 
and may pro long the contact t ime with the 
cornea. 
Other approaches rely upon the use of subcon- 
junctival or subtenonal injections of drugs to 
provide a similar reservoir for slow release of the 
d rug (diffusion or leakage f rom the injection 
.site) onto the cornea and pro longed absorption. 
Most ophthalmic textbooks list dosages for sub- 
conjunctival antibiotics, s,9 It should be remem- 
bered, however, that some of the dosages recom- 
m e n d e d are for humans or adult domestic 
mammals . The m a x i m u m r e c o m m e n d e d sys- 
temic dose of any drug should be calculated to 
ensure that a potentially toxic dose is not give 
subconjunctivally. This is especially impor tan t 
for aminoglycosides. 
Althoughsubconjunctival injections are a good 
me thod to pro long the contact t ime of the drug 
with the eye, in most cases, the drug may still 
need to be injected at least daily to achieve 
adequate concentrations. This can be avoided by 
using depot (long-acting) formulat ions of drugs. 
This will practically only apply to long-acting 
corticosteroids, because many other drugs (for 
instance, most antibiotics) in long-acting formu- 
lations are too irritating to be injected unde r the 
conjunctiva. Another concern regarding the use 
of depot corticosteroids is the potential risk of an 
animal with a depot corticosteroid developing 
corneal ulceration or fungal keratitis. In these 
cases, the depo t steroid may significantly retard 
healing or even potent iate the corneal infection 
with loss of the eye in severe cases. Nevertheless, 
this complicat ion must be weighed against the 
potential advantage of reduced frequency of 
drug application in dangerous or easily stressed 
species where some risk of loss of the eye may be 
favorable compared with loss of the animal or 
injury to personnel. A combinat ion of betametha- 
sone acetate and be tamethasone sodium phos- 
phate provides a good depo t of corticosteroid for 
inf lammatory disease in the absence of corneal 
erosion or ulceration. 
Various techniques have been used to facili- 
tate administrat ion of medicat ion in liquid fo rm 
without having to topically apply drops to the 
eye. Most notably, a subpalpebral lavage may 
allow relatively easy and f requent application of 
drugs to the eye of head-shy animals with less risk 
to the animal or the keeper. The technique for 
p lacement of a subpalpebral lavage is simple, 
requiring, at most, sedation in most species 
where it is practical. 7 However this me thod may 
not work in all cases. Although subpalpebral 
lavage has been used successfully in ratites and 
ungulates of various types, it has not been used in 
carnivores or species such as primates or el- 
ephants which would be able to remove the 
lavage easily. The main benefi t lies in use with 
large fractious animals that are at least approach- 
able. In animals which cannot be handled, they 
have limited application. 
Fortified antibiotics are essential for treating 
many forms of ocular surface disease, in particu- 
lar corneal ulceration. Formulas for fortification 
of commercial ly available preparat ions of formu- 
lation of antibiotics in artificial tears are available 
in most ophthalmology textbooks. 9 
In some animals the only effective way to 
medicate is by using systemic drugs, preferable 
mixed with food, because the repeated use of 
injectable drugs, ei ther by dart or application, in 
a restrained animal results in an even more 
difficult situation for safe restraint and may be in 
no way superior to topical d rug administration. 
Systemic administrat ion of drugs would be neces- 
sary for diseases affecting the poster ior segment 
of the eye, but may not be effective in reaching 
156 Nicholas J. Millichamp 
adequate tear concentrat ions for therapy for 
corneal disease. An example of a suitable use of 
systemic drugs would be the injection of oxytetra- 
cycline to treat infectious bovine keratoconjunc- 
tivitis in hoofstock. 
Several forms of ocular disease, especially 
conditions affecting the eyelids, cornea, and 
glaucoma, may be most effectively treated surgi- 
cally to try to minimize the need for f requent 
medicat ion of the eye. Exolic species more than 
domestic animals should undergo early surgical 
therapy wherever possible because this may be a 
far more effective means of therapy that topical 
applications of medications. 
Specific Diseases of the Eye 
Eyelids 
Anatomical abnormali t ies of the eyelid of 
exotic species appear to occur rarely, probably 
because the selection pressures which have re- 
sulted in eyelid defects in pu reb red dogs have 
not had a chance to prevail in zoological collec- 
tions. Obviously, if encounte red problems such 
as entropion, ectropion, or cilia abnormali t ies 
(distichiasis) can be easily corrected surgically 
without the need for cont inued medical therapy. 
Eyelid tumors may occur sporadically and should 
be subjected to surgical biopsy/Jcesection. Al- 
though other modalities o f t h e r a p y may be 
useful (cryosurgery, radiation therapy) in valu- 
able animals, any risk of metastasis or local 
invasion should call for early removal of as much 
neoplastic tissue as possible and often, in view of 
the nature of the patients, complete lid resection 
and enucleation; the loss of the eye is prefer red 
to save the animal. Blepharitis may be a signifi- 
cant challenge depend ing on cause. Parasitic 
blepharitis may respond to appropr ia te systemic 
medications. Bacterial blepharitis often requires 
a lengthy per iod of t rea tment with appropr ia te 
systemic antibiotics after culture and sensitivity is 
p e r f o r m e d f rom within lid granulomas. Fungal 
btepharitis also requires long-term systemic medi- 
cations for effective therapy. In these instances, 
medications can be given in the feed for danger- 
ous species or parenteral ly for animals which can 
be moderately restrained. 
Conjunctiva 
Conjunctivitis may occur in exotics associated 
with the diseases which cause the same signs and 
clinical disease in domestics. For instance, in big 
cats feline herpesvirus may cause significant 
morbidity with the same outcomes seen in domes- 
tic cats (eg, recur ren t keratitis, symblepharon) . 
Systemic antibiotic therapy coupled ~*Ath subcon- 
junctival injections of antibiotics are indicated in 
difficult animals. Parasitic conjunctivitis in equids 
caused by Habronema sp can easily be treated with 
ivermectin and a subconjunctival corticosteroid. 
Cornea 
Ulcerative keratitis is not c o m m o n in exotic 
species, almost invariably precipitated by trauma. 
Secondary bacterial infections may result in 
severe corneal ulceration or perforation. Al- 
though superficial abrasions to the corneal epi- 
thel ium may heal rapidly without treatment, in 
most cases it is advisable to apply topical antibiot- 
ics, and, at least in mammals , a parasympatho- 
lytic agent to reduce the secondary uveitis which 
may develop. In a dangerous species, it may be 
appropr ia te to chemically restrain the animal to 
fully evaluate the cornea, rule out any inciting 
cause (such as lid defects or foreign bodies) and 
decide whether to apply medical therapy or 
p roceed directly to surgery. 
For a small superficial ulcer which can be 
observed closely and for which administration of 
topical antibiotics every 6 hours is impossible, 
subconjunctival antibiotics and atropine should 
be given while the animal is restrained. Avoid 
third eyelid flaps or tarsorrhaphies for any case 
of ulcerative keratitis because these methods 
limit the ability to examine the eye (even f rom a 
distance with binoculars). 
If a superficial ulcer fails to heal within 3 days, 
the animal should be restrained and the cornea 
examined again. I f the ulcer appears to be 
showing signs of becoming indolent (superficial 
but with fluorescein diffusing beneath the edge 
of the ulcer or with epi thel ium loosely attached 
around the edge of the ulcer) or if the ulcer 
appea r deeper than at the first examination, 
consideration should be given to placing a con- 
junctival flap (either a pedicle or bridge) should 
be applied to the cornea to cover the defect. 
H o o d or 360 ~ flaps should be avoided because 
Ocular Disease i'~ Exotics 15 7 
they are often difficult to dissect and appose and 
because they will limit the view of the cornea (Fig 
1). At the time of surgery, subconjunctival antibi- 
otics should be injected along with atropine. I f 
the ulcer is very deep or "mel t ing," the choice of 
antibiotic should be based uponcytology of a 
scraping f rom the edge of the ulcer, or the use of 
a b road spec t rum agent especially effective 
against gram-negative bacteria. For deep ulcers 
and descemetocele, corneal grafting methods 
are ideal means of therapy for exotic species. All 
corneal surgeries require postoperative subcon- 
junctival antibiotic and atropine and systemic 
nonsteroidal ant i- inf lammatory drugs (in spe- 
cies where they can be used safely) to aid healing 
and reduce the pain f rom secondary uveitis. 
Lacerations of the cornea are commonly seen 
in exotic species. Principles for evaluation and 
surgical t rea tment are the same as for domestic 
species. Surgical access to" the cornea may be 
difficult in some enophthalmic species with strong 
extraocular muscles, even under quite deep 
surgical anesthesia. Closure of corneal lacera- 
tions may require far thicker suture material in 
some species than we are used to in domestic 
corneas (Fig 2). Involvement of an ophthal- 
mologis t for these surgical p rocedu re s is 
r ecommended . 
In animals that will allow minimal restraint or 
approach without becoming stressed or major 
hazard to personnel, a subpalpebral lavage is an 
ideal me thod of medicat ing the eye frequently 
,with fortified solutions of antibiotics. 7 This sys- 
tem has been successfully used with ratites and 
hoofstock (such as llamas). 
Figure 1. A corneoscleral transposition was used to 
provide a blood supply and support to a deep corneal 
ulcer in this wild horse. See Figure 35 on page 120. 
Figure 2. Retraction of the globe during surgery 
made access to this elephant's eye difficult during 
repair of a corneal laceration. Apposition of the 
wound margins required use of 4:0 absorbable suture, 
far thicker than ever used in domestic species. The 
cornea healed well and the eye was visual. See Figure 
36 on page 120. 
Lesions resembling infectious bovine keratitis 
have been seen in several species of wild hoofs- 
Lock. Although it is unclear whether the same 
infectious agent is involved in all species, the 
similar therapy may be indicated. In recalcitrant 
animals, the use of systemically administered 
antibiotics may be effective in treating the dis- 
ease. Tetracycline has been used systemically 
with good results. Subconjunctival antibiotic in- 
ject ions (with a wide range of drugs) is also a very 
effective way to treat these cases. 
Chronic superficial keratitis (pannus) may 
occasionally occur in wild canids. Although it 
can be controlled by f requent (monthly) subcon- 
junctival corticosteroid injections, the need for 
cont inued therapy th roughout the animal 's life 
makes this approach less than desirable. Al- 
though the condit ion may eventually be blind- 
ing, it is rarely painful and may therefore, in 
some dangerous species, be best left unmedi- 
cated. 
Corneal dystrophies will rarely warrant therapy. 
Stromal lipid dystrophies are usually painless 
and often minimally affect vision. Epithelial dys- 
trophies (such as indolent or recur ren t ulcer- 
ations) may be treated by application of a con- 
158 Nicholas J. Millichamp 
junctival flap with or wi thout superficial 
keratectomy. Endothelial dystrophies may be 
presumed to occur on some species of wild felids 
and canids and would, in advanced cases, pre- 
sent a significant therapeutic challenge just as in 
domestic animals. 
Uveitis and Chorioretinitis 
Inflammation of the materior or posterior 
segment can be treated with systemic medica- 
tions coupled with subconjunctival injections of 
corticosteroids and atropine (the latter applies 
to use in mammals). Efforts should obviously be 
made to determine any underlying systemic 
causes for uveitis which may respond to paren- 
teral or oral therapy and aid resolution of the 
uveal inflammation. Use of depot preparations 
of corticosteroids may be used to minimize 
repeated chemical restraint. 
Lens 
Cataracts and lens luxation are occasionally 
seen in exotic species. Lens removal using phaco- 
emulsification and aspiration is the prefer red 
technique for cataract removal in most species 
al though the size of the eye is usually a limiting 
factor. Special phacofragmentat ion techniques 
have been developed for large eyes I~ and used 
successfully in species such as ratites and llamas, 
Although the surgery may be straightforward, 
f requent postoperative administration of anti- 
inflammatory drugs may be problematic. There 
is considerable interspecies variation in the re- 
sponse of the eye to intraocular surgery, which 
will de termine how frequently postoperative 
medications need to be applied. Primate eyes 
respond with less uveitis than eyes of hoofstock; 
hoofstock may need intensive postoperative 
therapy for per iod of 2 to 4 weeks. The subpalpe- 
bral lavage may facilitate topical application of 
anti- inflammatory drugs. In some cases, re- 
peated subconjunctival injections of anti-inflam- 
matory and parasympatholytic drugs may be 
essential to minimize inflammation and prevent 
synechia formation. Systemic anti-inflammatory 
drugs (such as flunixin meglumine in species 
where this can safely be used) given in the feed 
will help minimize postoperative uveitis ancl pain 
and reduce the risk of self-trauma to the oper- 
ated eye. 
Glaucoma 
Elevated intraocular pressure with blindness 
is a difficult disease to control in domestic 
species and certainly more so in exotics. Neither 
medical or surgical management can be sure of 
effective results, especially over a long period of 
time. The need for f requent administration of 
topical and systemic drugs present an almost 
insurmountable challenge when dealing with 
exotic species. In many instances, the presence 
of glaucoma will not be noticed until the disease 
is quite advanced, causing obvious globe enlarge- 
ment or blindness. 
In an animal diagnosed with elevated pres- 
sures, attempts should initially be made to quickly 
reduce the pressure to determine whether any 
potential for vision remains. This may be done 
during a 24-hour period with medical therapy 
(in mammals, use intravenous hyperosmotics 
and carbonic anhydrase inhibitors coupled with 
topical parasympathomimetic, ~-adrenergic ago- 
nists, and ~-adrenergic antagonists). 
In animals where vision is still present, two 
options exist to maintain vision with minimal 
medical therapy. Cyclophotocoagulation, using a 
diode laser or cyclocryoablation, will reduce 
aqueous h u m o r product ion to a level that may 
maintain the intraocular pressures within the 
normal range. In some cases, the surgeon may 
elect to combine one of these procedures with 
placement of a glaucoma valve to increase aque- 
ous outflow. Subconjunctival anti-inflammatory 
drugs will help control the acute uveitis induced 
by these techniques. 
For exotic species blind and painful from 
glaucoma, evisceration of the globe with intraocu- 
lar placement of a silicone prosthesis is an 
excellent me thod to control the pain and main- 
tain a cosmetic appearance. This may be impor- 
tant for animals which remain on exhibit. Ani- 
mals that lose vision slowly and that live in a 
restricted area may accommodate to their blind- 
ness well after this surgery, al though care should 
be taken to ensure that they are unable to sustain 
injury within their enclosures. Silicone prosthe- 
ses come in a range of sizes (millimeter incre- 
ments) to fit the eyes of almost any animal. 
Posterior Segment 
Apart from inflammatory disease of the retina 
and choroid (see uveitis above) retinal detach- 
Ocular Disease in Exotics 15 9 
m e n t m a y r e q u i r e su rg ica l t h e r a p y as in d o m e s t i c 
species . R e t i n a l d e g e n e r a t i o n s o c c a s i o n a l l y oc- 
c u r in e x o t i c spec ies . I n m o s t cases, i t is n o t 
k n o w n w h e t h e r t h e s e a r e i n h e r i t e d o r e n v i r o n- 
m e n t a l ( in fec t ious , n u t r i t i o n a l , e tc . ) . 
Conclusions 
B e c a u s e a p p l i c a t i o n s o f m e d i c a t i o n to t h e eye 
o f e x o t i c spec ies m a y o f t e n b e i m p r a c t i c a l , o t h e r 
t e c h n i q u e s s u c h as sys temic d r u g t h e r a p y a n d 
o c u l a r s u r g e r y s h o u l d b e i m p l e m e n t e d ea r ly in 
t h e c o u r s e o f the rapy . T h e s e m e t h o d s c a n o f t e n 
r e s u l t in a f a v o r a b l e r e s o l u t i o n o f va r i ous o c u l a r 
diseases . I n v o l v e m e n t o f an o p h t h a l m o l o g i s t is 
e s sen t i a l to p r o v i d e a p p r o p r i a t e t h e r a p y f o r valu- 
a b l e spec ies m a i n t a i n e d in m a n y co l l ec t i ons . 
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