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IOP presentation

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Rajeev Raut

The document summarizes an experiment measuring pressure in goat eyes using an applanation tonometer. The experiment found that increasing vitreous pressure in the eye did not consistently increase or could decrease anterior chamber pressure, but increasing anterior chamber pressure did raise vitreous pressure. The conclusions were that anterior chamber pressure measurements do not correlate with vitreous pressure, vitreous pressure may be high even when anterior chamber pressure is normal, and glaucoma damage is caused by high vitreous pressure rather than anterior chamber pressure.

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Tonopen applanation tonometer with small tip, ultrasound verifies applanation.
Freshly enucleated goat’s eyes
Pressure checked on deep sclerectomy
drawbacks 1. Dead eye with inactive metabolism 2. Test performed with eye out of socket. 3. Deep sclerectomy depth was not uniform in all eyes .
Instrument takes many measurements and averages them.
Showing how pressure was changed
When vitreous pressure was increased anterior chamber (ac)pressure did not increase or it even dropped. But when ac pressure was increased, vitreous pressure went up hand in hand. 0 5 10 15 20 25 30 35 40 45 50 1 2 3 4 Series1 Series2 0 5 10 15 20 25 30 35 40 45 1 2 3 4 Series1 Series2
conclusions 1. Anterior chamber (AC) pressure as is measured clinically today does not corelate with vitreous pressure.AC pressure values may be low or normalbut vitreous pressure may be very high. 2. Glaucoma damage happens because of pressure effects on the nerve head, namely the vitreous pressure. 3. The findings agree with a previous french study in its findings, though pressure measurement method in the french study was different.( acta ophthalmologica , Hernandez and Bolivar2010) 4. This may explain pathogenesis of low pressure glaucoma. 5. Instruments to measure vitreous pressure are required.Surgeries /implants/drugs designed to lower anterior chamber pressure may not help a patient.

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IOP presentation

  • 1. Tonopen applanation tonometer with small tip, ultrasound verifies applanation.
  • 3. Pressure checked on deep sclerectomy
  • 4. drawbacks 1. Dead eye with inactive metabolism 2. Test performed with eye out of socket. 3. Deep sclerectomy depth was not uniform in all eyes .
  • 5. Instrument takes many measurements and averages them.
  • 6. Showing how pressure was changed
  • 7. When vitreous pressure was increased anterior chamber (ac)pressure did not increase or it even dropped. But when ac pressure was increased, vitreous pressure went up hand in hand. 0 5 10 15 20 25 30 35 40 45 50 1 2 3 4 Series1 Series2 0 5 10 15 20 25 30 35 40 45 1 2 3 4 Series1 Series2
  • 8. conclusions 1. Anterior chamber (AC) pressure as is measured clinically today does not corelate with vitreous pressure.AC pressure values may be low or normalbut vitreous pressure may be very high. 2. Glaucoma damage happens because of pressure effects on the nerve head, namely the vitreous pressure. 3. The findings agree with a previous french study in its findings, though pressure measurement method in the french study was different.( acta ophthalmologica , Hernandez and Bolivar2010) 4. This may explain pathogenesis of low pressure glaucoma. 5. Instruments to measure vitreous pressure are required.Surgeries /implants/drugs designed to lower anterior chamber pressure may not help a patient.