Intravitreal triamcinolone acetonide induced changes in the anterior segment in a pig model of branch retinal vein occlusion.
BACKGROUND
Triamcinolone acetonide (TA) has applications for the treatment of a large range of intraocular vascular diseases. The present study in pigs was performed to investigate histopathological and histochemical changes in the levels of myocilin deposition in the anterior segment in a model of branch retinal vein occlusion (BRVO) after vitreal administration of TA.


METHODS
After ophthalmoscopic examination, intraocular pressure (IOP) measurement and fundus photography, a BRVO was created photothrombotically in each eye of six pigs, using argon green photocoagulation. The left eye was then injected intravitreally with 4 mg/0.1 ml TA. After 11 weeks, the eyes were re-examined, animals sacrificed, and eyes enucleated and processed in paraffin and epoxy resin. Immunofluorescence cytochemistry on paraffin sections was performed to localise the distribution of myocilin in the anterior segment and histology by light and transmission electron microscopy on epoxy resin sections on TA-treated and untreated eyes.


RESULTS
Histology revealed pathological changes in the TA-treated eye, including swollen mitochondria, layered long endoplasmic reticulum, pleomorphic nuclei, dense fibrillar extracelluar deposits and aggregates of unusual cell inclusions. Myocilin levels were significantly higher in the TA-treated eyes in the trabecular meshwork (p = 0.001), ciliary process (p = 0.011) and iris (p = 0.030) than in the untreated eyes.


CONCLUSIONS
This study suggests that increased myocilin synthesis and related ultrastructural changes in the anterior segment after treatment with intravitreal TA in a porcine model of retinal oedema in BRVO may contribute to IOP elevation.
Vijayasekaran
Sarojini
S
Lions Eye Institute, Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Perth, WA, 6009, Australia.
McAllister
Ian L
IL
Morgan
William H
WH
Mendis
Kanishka R
KR
McMenamin
Paul G
PG
Cringle
Stephen J
SJ
Yu
Dao-Yi
DY
D000818:Animals; D000869:Anterior Eye Segment / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002924:Ciliary Body / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004195:Disease Models, Animal; D005136:Eye Proteins / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005938:Glucocorticoids / Q000008:administration & dosage / Q000633:toxicity*; D006023:Glycoproteins / Q000378:metabolism; D007429:Intraocular Pressure / Q000187:drug effects; D058449:Intravitreal Injections; D007498:Iris / Q000187:drug effects / Q000648:ultrastructure; D012170:Retinal Vein Occlusion / Q000188:drug therapy*; D013552:Swine; D014129:Trabecular Meshwork / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D014222:Triamcinolone Acetonide / Q000008:administration & dosage / Q000633:toxicity*; D000099179:Myocilin
D003598:Cytoskeletal Proteins; D005136:Eye Proteins; D005938:Glucocorticoids; D006023:Glycoproteins; D014222:Triamcinolone Acetonide; D000099179:Myocilin