1. Assessment of trans-laminar cribrosa pressure gradient and lamina cribrosa thickness in Normal Tension Glaucoma V. V. Volkov, I.L. Simakova, A.N. Kulikov, M.V. Sukhinin, A.S. Kharakozoff
Ophthalmology Department, The Military Medical Academy, St Petersburg, Russia

2. Purpose
Assess the role of trans-lamina cribrosa pressure gradient (TLCPG), lamina cribrosa thickness (LCT) and width of the subarachnoid space (WSAS) of the optic nerve (ON) in the diagnosis of normal tension glaucoma (NTG).

3. Material and Methods
Our pilot study involved 15 patients (30 eyes) aged from 41 to 76 years with suspect NTG. The patient examination included a standard ophthalmic assessment as well as Heidelberg retina tomography (HRT) and optical coherence tomography (OCT) of the optic nerve head (ONH), perimetry on Humphrey Visual Field Analyzer II and our modification of frequency-doubling technology perimetry. To calculate cerebro-liquor pressure (CLP) of the optic nerve (ON) we used the data of ophthalmodynamometry and the formula by R. Firsching et al. [2]. We also used laser ophthalmoscope Nidek F-10 for the registration of retinal vein pulsation. WSAS of the ON was measured in mm on the MRT- images of the ON in the coronal plane with T2-BI mode and fat suppression mode. LCT was measured in µm on the linear scans of the ONH obtained using ОСТ RTVue-100

4. Humphrey II 745i (Germany–USA)
Fig. 1. “Gold standards” for morphofunctional diagnostics of glaucoma [3] +
Progressive narrowing of Rim Volume of ONH
Typical of glaucoma visual field defects
Humphrey II 745i (Germany–USA)
HRT 3 (Germany)

5. Fig. 2. Additional research methods
Noncontacting tonometer (Japan)
Vacuum compression-perimetric test
by V. Volkov et al. (RF)
Threshold
Screening
Our modification of frequency doubling technology (FDT) perimetry and recording of results

6. Fig. 3. Examination of retinal venous pulsation on the ONH
The Baillart ophthalmodynamometer modification (USSR)
Assessment of retinal venous pulsation on the ONH performed with ophthalmodynamometer and slit lamp ophthalmoscopy
Modern vacuum ophthalmodynamometer (RF)
Registration of retinal venous pulsation on the ONH by scanning laser ophthalmoscope Nidec F-10 (Japan)
Widening of the lower branch of the central retinal vein
Narrowing of the lower branch of the central retinal vein

7. Calculation of trans-lamina cribrosa pressure gradient (TLCPG)
1. Intraocular pressure (IOP, mm Hg) was measured with noncontacting tonometer, taking it for P0.
2. During slit lamp ophthalmoscopy ophthalmodynamometer was used to increase IOP until venous pulsation appeared on the ONH.
3. Based on the data obtained, pressure in central retinal vein (Pcrv, mm Hg) was calculated from the formula:
Pcrv = IOP + ODF,
where ODF is the value of the ophthalmodynamometric force (mm Hg) at which the central retinal vein pulsation occurs.
4. Based on the regression analysis, сerebro-liquor pressure (CLP, mm Hg) of the ON was calculated from the formula by R. Firsching et al. [2]:
CLP = x Pcrv
5. TLCPG was calculated as the ratio IOP:CLP (Norm: ) [1]. 
*Градиент

8. 3 mm posterior to the globe
Fig. 4. The study of LCT of the ONH and WSAS of the ON using
OCT and MRI
3 mm posterior to the globe
Horizontal OND*
Vertical ONSD**
Vertical OND*
LCT of the ONH
Horizontal ONSD**
ОСТ RTVue-100 (USA)
MRI Siemens Simphony 1,5T (Germany)
* OND – optic nerve diameter
** ONSD – optic nerve sheath diameter