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Arie L Marcovich, Alexandra Goz, Jurriaan Brekelmans, Alexander Brandis, Sydney R Cohen, Avigdor Scherz; In vivo stiffening of rabbit sclera by bacteriochlorophyll derivative WST11 and near infrared light. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5882.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate scleral stiffening in vivo in rabbits induced by external impregnation of WST11 and external or transpupillary near infrared (NIR) illumination by atomic force microscopy (AFM).
Five rabbits 12 weeks old were anesthetized by intramuscular injection of ketamine and xylazine. In 3 rabbits the conjunctiva was incised in one eye and a custom cannula with fenestrations on its internal side was introduced into subtenon’s space down to posterior sclera. The treatment area was assessed by indentation with the cannula visualized by an indirect ophthalmoscope and 1ml of WST11 solution 2.5 mg/ml was injected slowly. After 20 minutes, NIR illumination by laser mounted on indirect ophthalmoscope was delivered transpupillary for 10 minutes using a 20 diopter lens. Measured NIR light intensity was 120 mW/cm2 at the corneal plane. Immediately after treatment the rabbits were sacrificed and scleral samples were excised for AFM study. In two rabbits the equatorial sclera in one eye was exposed and impregnated with WST11 solution 2.5 mg/ml for 20 minutes. External NIR laser illumination at 10mW/cm2 was applied for 10 minutes. After 1 month the rabbits were sacrificed and scleral samples were excised. In all 5 rabbits, scleral strips from the treated areas were analysed and compared to the corresponding area in the non treated eyes using JPK Nanowizard 3 AFM. Young's modulus was determined at the sub-micron scale by AFM indentation curves using pyramidal silicon probes and analyzed using a Hertzian model.
AFM measurements showed that the average Young's modulus of the posterior sclera immediately after treatment with transpupillary illumination was 155.7 KPa compared to 35.66 KPa in the controls, an increase of 335.4% (p=0.05). Young's modulus of the equatorial sclera one month after treatment with external illumination was 166 KPa compared to 65 KPa in the controls, an increase of 170%.
Treatment with WST11 followed by transpupillary or external NIR illumination induced scleral stiffening in rabbit eyes in vivo. The safe and penetrative nature of NIR enables frontal illumination through the pupill. This light delivery can avoid the surgical exposure of the sclera that is required for external illumination and simplify the procedure. This novel treatment may be suitable to halt the progression of degenerative myopia.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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