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Gopal Lingam, Valencia Hui Xian Foo; Safe intravitreal injection in eyes with retinoblastoma- development of a model. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):402.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a model of safe intravitreal injection that can be adopted for eyes with retinoblastoma
This experiment was conducted on pig eyes obtained from slaughter house. The eye was stabilised on a holder and the screw tightened till the intra ocular pressure was in the range of 12-15mm/hg as measured by tonopen. A 30 gauge needle entry track was made 1mm internal to the limbus till the anterior chamber was entered. The needle was withdrawn. A 36 gauge needle atttached to a syringe with fluorescein stained saline is threaded through this track and then antero posteriorly through the iris root and zonules into the vitreous cavity. 0.1 ml of the dye stained saline was injected and the needle was withdrawn. Flurotron (ocumetrics, Mountain view, CA) was used to measure fluorescence in the anterior chamber. As a reference fluorescein was applied on corneal surface after epithelial debridement. The cornea and the lens were excised to visibly confirm the presence of significant fluorescein in the vitreous gel.
No fluorescence was observed in the anterior chamber on measurement with Fluorotron. The vitreous was found to be intensely stained with fluorescein on direct examination.
36 gauge needle entry through the iris root and zonules does not permit intra vitreous contents to migrate into the anterior chamber. A 2 step approach of entering anterior chamber through the relatively tough cornea with 30 gauge needle and the subsequent entry through relatively soft iris and zonules with a finer 36 gauge needle, can potentially prevent any exit of tumor cells extra ocularly in eyes with retinoblastoma.
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