Cataracts Rainwater et al (2105) reported, in

Cataracts
have been diagnosed and treated with different techniques in a wide variety of captive2,
5,6,7, 9 and wild species; 1, 3, 4, 8 birds have not been the
exception.10, 11,12,13,14,15 Rainwater et al (2105) reported, in a retrospective study, 90 cataracts
identified in 54 birds of 42 species. Of those 90 cases, 18 cataracts were
removed from 12 birds, and phacoemulsification was performed in 16 eyes.16

            There are few reports of cataracts
in flamingo species. Only one exists in a Chilean flamingo; a resorbed cataract
in one eye of a 34.7-year-old individual. Such bird was found to be
serologically positive for West Nile Virus (WNV) in fall of 1999 and was
thought to have recovered from natural infection. 16 Meekins et al report an incipient anterior
cortical cataract OD in an American flamingo (Phoenicopterus ruber) between 2 and 7 years old; this study also
reports mild trauma to the periocular skin and other areas of the head in two
other flamingos without cataracts, these skin abrasions were associated to
trauma from capture or injuries caused by aggression with other birds. 17
In this same species, 3 adult American flamingos between 4- 57 years old were
excluded from an IOP study, two individuals had for bilateral cataracts and one
had unilateral cataracts. 18 The present case shows similarities
with previous reports, since this 32-year-old female Chilean flamingo had a
mature cataract OS, and a Hypermature Resorbed Cataract (posterior Synechia)
OD.

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            Although the presence of lesion in
the periocular skin OS is highly suggestive of trauma, the exact cause for both
cataracts could not be determined. Cataracts in birds have been associated with
skeletal malformations, genetic disorders, nutritional deficiency, infection,
trauma, senescence, toxic effects, and ocular problems such as uveitis and
retinal degeneration. 15 Senile cataracts have been considered to be
the most common classification in aged birds. 34 Blunt traumas were
suggested to be the most common traumatic injury in birds. Labelle et al associated ocular lesions in
hawks and owls primarily to head trauma (86.7%), and less lesions were reported
in the eyes of birds with body trauma (41.9%), systemic disease (50%), or in
healthy birds (20%). 26 The flamingo in the present case is one of
the smallest in the flock and has not been observed coupled with any male.
Although the hierarchy and pairings in this particular captive flock have not
been determined, these features would place her in a relatively low rank
according to some behavioral studies where captive Caribbean27 and
captive Chilean flamingos28 present a semi-linear hierarchy. These
studies show dominant birds, and their pairs more frequently target subdominant
birds. Thus cataracts secondary to a traumatic event with a conspecific are
highly probable.

Lens-induced uveitis (LIU) can be caused by cataract development and
maturation, this process can occur in eyes of mammals and birds. LIU
develops when lens proteins leak from the lens capsule and incite an
immune-mediated inflammatory response, resulting in ocular pain and lesion. Short-term
effects of LIU include corneal edema, aqueous flare, and miosis. Chronic
sequelae may involve rubeosis iridis, posterior synechia, lens instability because
of disintegration of ciliary body attachments, secondary glaucoma, and retinal
detachment. 19 Phacoclastic uveitis can occur as a result of lens
capsule rupture and is characterized by perilenticular fibroplasia.6 LIU
is a major cause of complications in cataract surgery. It can be assumed to be
present in all patients with mature or hypermature cataract. Early treatment
for LIU and treatment of the cataract are essential if optimal results are to
be obtained. Any incipient LIU—indicated by ciliary injection, hypotony,
miosis, aqueous flare, change in iris color, or resistance to mydriasis—must
first be controlled by topical corticosteroids and/or non-steroidal anti-inflammatories
(NSAIDs) under the supervision of the person who will perform the surgery. The
incidence of short- and long-term complications is greater when uveitis is
present preoperatively. 20 Anterior uveitis should delay cataract
surgery until attempts are made to discover the cause of the inflammation and
the inflammation has been treated successfully. 15

            An ophthalmic examination protocol
including slit-lamp biomicroscopy, indirect funduscopy, ocular morphometrics,
B-mode ultrasound, and electroretinography (ERG) has been established for
evaluating raptors 21; a similar process has also been useful in
horses. 31 Apart from ERG, this protocol was implemented and proved
to be useful for diagnosing and establishing a treatment plan for the present
case and is recommended for Chilean flamingos and other avian species.

            One challenge that was encountered
during the decision-making process was the lack of species-specific ocular
parameters. Even though there are published values of ophthalmic diagnostic
tests and ocular findings in American flamingos17 and other avian
species22, 23,24, 25. The variability in results emphasizes the need
for specific values for un-described species like this one.

            One of the main objectives of
cataract surgery is returning visual capacity to the patient. If the bird is
healthy, no uveitis is present, and the bird’s personality and temperament will
tolerate aggressive topical therapy and repeat postoperative ophthalmic
examinations, the bird is a good candidate for unilateral and bilateral
cataract surgery. The patient must be amenable to intensive postoperative
therapy. 15 The anatomic considerations mentioned initially that are
specific to birds, were taken into account for the diagnostics, surgery and treatment
of a mature cataract in this flamingo. Particularly, the corneal incision was
made caudo-ventral since it
would be difficult to suture cornea
to bone (scleral osscicles), and to reduce iris prolapse due to the narrow
anterior chamber peripherally.

            Phacoemulsification has
become the technique of choice for cataract removal in veterinary
ophthalmology. Even though there is a reported short-term success rate that
exceeds 90%, many complications may arise in different postoperative periods. Posterior capsule
opacification (PCO) is the most common postoperative complication in dogs.
 30 In horses such complications
include corneal edema, fibrin in the anterior chamber, postoperative ocular
hypertension and synechia/dyscoria. 31 In birds, Postoperative
complications include persistent iridocyclitis and plasmoid aqueous,
fibropupillary membranes, synechiae, iris bombe, corneal ulceration, corneal
edema, corneal fibrovascular infiltrates, posterior capsular opacification,
retained lens cortex, wound leakage, vitreous presentation into anterior
chamber, retinal degeneration, retinal detachment, and infectious
endophthalmitis. 15 PCO was also the most commonly reported
postoperative complication in birds in a zoological setting. 16

            The
persistent uveitis the patient presented is thought to be a consequence of
returning the individual to soon to her enclosure (7 days post surgery). The
behavioral and feeding habits (filter feeders) 33 of flamingos make
submersion and contact with water inevitable in their daily activities. This
presented a constant source of contamination to the incision site and an immunologically
compromised eye, resulting in constant uveitis. Reports of recovery times from
cataract surgery in bird species are broad, but the 3 months described here are
considered to be within the time limits. 10,11,12,13,14,16

Of the treatment that was implemented pre, peri and post-operatively,
the only medication with pharmacokinetic (PK) and pharmacodynamics (PD) studies
in flamingo species is meloxicam. Oral administration (3 mg/kg PO) resulted in
a greater persistence of drug exposure than a subcutaneous dose (1.5 mg/kg). 29
This study proved that marked changes in drug absorption and elimination could
also be seen within a species when dose extrapolations or different routes of
administration are used, highlighting the importance of PK and PD research for
specific avian species. The most common category of ophthalmic
medication used postoperatively in removal of cataracts in birds were an
antibiotic-steroid combination administered topically. 16

Hypermature cataracts are an important risk factor for the development
of postoperative glaucoma. Eyes with these types of cataracts presented an
increased risk for failure of PE in dogs. 30 Although such risks
exist in dogs, birds can also regain sight once the cataract has progressed to
the resorbed stage. Cataract removal was not recommended in many birds with
resorbed cataracts because they were able to move around their enclosures and find
food with aphakic vision. Development of retinal detachment was not associated
to the progression of cataracts in these avian cases. 16

 

Conclusions

 

The present case exemplifies two different approaches for cataract
management and treatment in a Chilean flamingo. The clinically evident mature
cataract and LIU identified OS was confirmed with specialized Ophthalmologic
equipment. The medical management of that eye followed recommendations from the
boarded Veterinary Ophthalmologist and previously reported approaches. 15,20,34
The hypermature resorbed cataract OD was an incidental finding but
reinforces that proposed by Rainwater et
al in which the cataract advanced undetected to a hypermature state and did
not interfere with the individual’s daily activities. 16 Both eyes
in this patient are considered to be aphakic but the bird shows no
abnormalities and is considered to be clinically visual based on subjective
observation of behavioral changes and an increase in weight (2.5 kg in October,
2017).

            This is the first report of a
unilateral phacoemulsification of a mature cataract in a Chilean Flamingo, as
well as the diagnosis of a hypermature resorbed cataract. This case emphasizes
the need for integrating the use of specialized and relatively new diagnostic
techniques and equipment, as well as Board Certified professionals in
Veterinary Ophthalmology to guarantee the best possible care for birds that
present with ocular diseases.