Management of Glaucoma w/ SLT or Trabecular Stent Bypass Microsurgery Using the Diopsys VEP/PERG Protocols

Objectives:

To establish electrophysiological benchmarks, using the Diopsys Visual Evoked Potential/
Pattern Electroretinogram (VEP/PERG) protocols of populations with Glaucoma before and after
either Selective Laser Trabeculoplasty (SLT) or Trabecular Stent Bypass Microsurgery.

Study Rationale/Background:

The VEP and PERG have been proven and accepted as a viable clinical tool in the assessment
of diseases of the retina ganglion cells. The Diopsys Neuro Optic Vision Assessment Vision
(NOVA) Testing System generates a battery of retinal responses evoked by viewing
horizontal/checkerboard grating patterns with optimized contrast levels and visual field
sizes.

Electrophysiological tests evaluate the function of the different structures constituting
the visual nervous pathways (retina, optic nerve, optic tract, and chiasm, radiation and
cerebral cortex). Among the various electrophysiological examinations, two very important
tests are Electroretinograms (ERGs), which study the various retinal components, and Visual
Evoked Potentials (VEPs) which study the visual pathway. These tests provide objective
information on the function of the visual system even in those cases in which opacities of
dioptric means (cataract, corneal leukoma) do not allow the direct observation of the retina
and optic nerve, and may provide functional information in advance of structural changes.

The first recorded electrophysiological waveform of the inner retina, the precursor to a
PERG, was successfully recorded from normal eyes in 1964 by Riggs et al and clinically
utilized in 1973 by Lawwill et al. Groneberg and Teping in 1979 observed a complete loss of
the PERG signal on a patient with an injured optic nerve leading to the conclusion that the
PERG originates from the proximal retinal structures. Maffei and Fiorentini in 1981 and 1982
established the foundation for PERG as its known today and determined that the source of the
PERG was from the ganglion cells and were not originated from the outer retinal layers.
Finally, Maffei and Fiorentini made the following conclusions: PERG represented the
electrical activity of the ganglion cells; PERG could be generated by stimulating the cone
system; and the PERG signal was eliminated in ganglion cell disease due to the "cascade
effect" in macular disease. The localization of the PERG signal to central vision is due to
90% of the eye's ganglion cells being located within the central 10 degrees of the retina.

PERG can also be used to help the clinician in the decision of "when to treat" and "when not
to treat". Bach et al has found that PERG can be used as an indicator of early glaucoma in
Optic Nerve Head (OHT) patients, therefore, the clinician will know if there is any Retinal
Ganglion Cell (RGC) dysfunction loss prior to commencing treatment.

Evaluation of the structure and function of the visual pathway is critical in the clinical
decision and/or diagnostic process of diseases affecting this system. The objective
structural analysis of the retina and intraocular segment of the optic nerve has had
significant development in the past decade, especially with the introduction of scanning
laser ophthalmoscopy (SLO), scanning laser polarimetry (SLP) and optical coherence
tomography (OCT). The evaluation of the function of the visual pathway still relies on
subjective visual field (VF) assessment. Although the evolution of VF techniques (e.g. Short
Wavelength Automatic Perimetry and Frequency Doubling Technology), it remains as a
subjective analysis of visual function.

Maculopathy and neuropathies are included in the long list of diseases of the visual pathway
that permanently impair visual function. As there are considerable evidences related to the
nature and evaluation of maculopathy and glaucomatous neuropathy, objective and reliable
techniques are needed for visual function evaluation. By using PERG recordings, doctors are
able to differentiate between normal subjects and subjects with ocular hypertension
notwithstanding a normal optic disc and VF. PERG can provide important diagnostic
information regarding the functional integrity of the macula and ganglion cells.

Based on a longitudinal study from Bascom Palmer Eye, abnormal retina function was recorded
by PERG eight years before structural damage to the RNFL was detected. The study suggests
that for glaucoma suspects it takes two years for a 10% change in PERG amplitude while it
takes ten years for 10% change in RNFL.

Significance:

The Diopsys NOVA-PERG is a retinal biopotential that is evoked when a temporally
phase-reversed horizontal/checkerboard grating pattern of constant total luminance is
viewed. The contrast and viewing angle of the stimulus is optimized to elicit detection of
dysfunction of the macula or the retinal ganglion cells selectively. The two NOVA-PERG
reporting protocols are Contrast Sensitivity (CS) and Concentric Stimulus Fields (CSF). CS
is optimized to detect dysfunctions of the retina that are sensitive to discrimination
between different contrast levels while the CSF is optimized to localized pathologies in
specific regions of the retina such as central vision and macula. Currently both protocols
utilize steady-state technology.

The Diopsys NOVA-ERG is a retinal biopotential that is evoked when a temporally
phase-reversed pattern of constant total luminance or flashes are viewed. The contrast and
viewing angle of the stimulus is optimized to elicit detection of dysfunction of the retina.

The advantage of the Diopsys ERG as compared to traditional PERG is that it is non-invasive.
The electrodes are attached to the eyelid and not to the patient's conjunctiva. The Diopsys
ERG takes ten minutes to perform instead of 45 minutes. Patients also do not need to be
dark-adapted.

Methodology Observational, Prospective Case

Number of Centers Study will be conducted at one center—UPMC Eye Center.

Assignment of Groups Participants will be assigned to only 1 study group (Glaucoma; N = 60).
There are two treatment groups: Glaucoma patients undergoing Selective Laser Trabeculoplasty
(SLT) (N = 30) and Glaucoma patients undergoing Trabecular stent bypass microsurgery (N =
30). Both treatment groups will undergo the same procedures.

Procedures:

Procedures/Timeline of Events

All the participants will be evaluated at the UPMC Eye Center and undergo the following
procedures:

Post-Op (Baseline):

- Ophthalmic Eye Examination

- Best Corrected Visual Acuity (BCVA)

- Intraocular Pressure Measurement

- Slit lamp Biomicroscopy of the Anterior Segment (includes Dilated Stereoscopic Fundus
Examination of the Retina & Optic Nerve Head)

- Visual Field

- Optical Coherence Tomography

- Fundus Photography

- Diopsys Visual Evoked Potential/ Pattern Electroretinogram (VEP/PERG)

Follow-up: 1 Month follow-up

• Diopsys Visual Evoked Potential/ Pattern Electroretinogram (VEP/PERG)

Follow-up: 6 Month follow-up

- Ophthalmic Eye Examination

- Best Corrected Visual Acuity (BCVA)

- Intraocular Pressure Measurement

- Visual Field

- Slit lamp Biomicroscopy of the Anterior Segment (includes Dilated Stereoscopic Fundus
Examination of the Retina & Optic Nerve Head)

- Fundus Photography

- Diopsys Visual Evoked Potential/ Pattern Electroretinogram (VEP/PERG)

Visual Evoked Potential/ Pattern Electroretinogram (VEP/PERG) Recording:

VEPs will be generated using a commercially available Diopsys Neuro Optic Vision Assessment
Vision (NOVA) System utilizing a fixed protocol. The stimulus will be presented on a 17-inch
LCD monitor, running at 75 frames/s. Luminance output over time will be verified using a
luminance meter MavoSpot 2 USB (Gossen, GmbH, Nurembert, Germany). Commercially available
skin preparation and Electroencephalogram (EEG) paste will be used for recording of the
Short-duration transient visual evoked potentials (SD-tVEP). Synchronized single-channel
VEPs will be recorded, generating a time series of 1024 data points per analysis window. The
room luminance will be maintained at scotopic conditions (<0.3 NITS). Preadaptation will be
unnecessary for the SD-tVEP recordings. Each phase reversal is 500 ms. Each phase reversal
will be monitored for blinking and eye movement. The device utilizes an automatic artifact
rejection algorithm to detect uncorrelated EEG data that distorts the VEP response. Artifact
rejection will be used during SD-tVEP data recording. If 50% or more of the phase reversals
are rejected, then the entire run will be rejected. The maximum run time for a single test
will be limited to 15 seconds. Multiple tests are run to comprise one SD-tVEP protocol. One
complete NOVA-VEP (FP) presents a stimulus for a maximum of 1 minute and 46 seconds.

In all cases, the display will be viewed through natural pupils (undilated) with optimal
refractive correction in place. The viewing distance will be set to 1 m, yielding a total
display viewing angle of 15.5 degrees. The square black/white checkerboard pattern reversal
stimulus has a height and width of 27 cm with a red circular ring used as a fixation target.
The diameter of the target is approximately 1.5 cm with a ring thickness of 1.5 mm. The
target ring will be centered on the stimulus. The check size will be 29.0 minutes of arc.
Two pattern contrasts will be used in the study, based on earlier studies that suggested
that differential contrast stimulation could affect the NOVA-VEP (FP) waveforms. The first
pattern will have a Michelson contrast of 15%. The second pattern will have a Michelson
contrast of 85%. These two patterns are referred to as LC (Low contrast) and HC (High
contrast) respectively.

During a recording session, the contrast polarity of each stimulus check will be temporally
modulated at a reversal frequency of 1 Hz (2 pattern reversals equates to 1 reversal cycle);
therefore, each reversal occurs at 2 Hz or twice per second. This stimulus is termed a
pattern reversal stimulus and has a duty cycle of 50%. The 15% and 85% contrast stimuli will
be presented for each eye (the fellow eye was covered) for 15 seconds. The right eye will be
the first one to be tested for all patients.

In preparation for recording, the skin at each electrode site will be scrubbed with Nuprep
(D.O. Weaver & Co, Aurora, CO) using a cotton gauze pad. Electrodes will be fixed in
position with Ten20 conductive paste (D.O. Weaver & Co, Aurora, CO) and secured with a small
gauze pad with conductive paste applied. Electrode impedance will be maintained below 10 kΩ
and typically kept below 5 kΩ. The gain of the EEG analog amplifier/filter module (Diopsys
Enfant Amp 100, Diopsys, Inc, Pine Brook, NJ) is 10,000 and the band-pass of the filtered is
0.5 to 100 Hz. The EEG signal will be sampled at 1024 Hz using the NOVA System's Analog to
Digital converter. As a note, the 10,000 gain is the only gain in the entire data
acquisition path, including the A/D 12-bit convertor. The A/D convertor offers a series of
bipolar voltage ranges. For this study, the voltage range of the A/D is programmed to (-)
1.25V to (+) 1.25 V with a resolution of 610 mV/quantum.

The Pattern Electroretinogram (PERG) will be recorded using a commercially available system
Diopsys NOVA (Diopsys, Inc. Pine Brook, New Jersey). The testing protocol will include the
Concentric Stimulus Field (CSF).

Subjects will be fitted with the appropriate correction for a viewing distance of 24 inches
and will be instructed to fixate on a target at the center of stimulus monitor. The test
will be performed in a dark room to standardized environment luminance, free of visual and
audible distractions. The subject will be comfortable seated facing the stimulus monitor.
The patient's seated height will be adjusted so the eye stays in a horizontal plane with the
center of the monitor. The test will be performed without pupil dilation and subjects will
be allowed to blink freely.

The PERG will be recorded from the study eye by means of hypoallergenic skin sensors
Silver/Silver Chloride ink (Diopsys proprietary Skin Sensor) on the lower eyelids. The
reference sensor will be located in the contralateral eyelid and ground sensor in the
central forehead area (Fz). The skin will be prepared by cleaning with eyelid cleanser
(OCuSOFT) to ensure good and stable electrical conductivity, keeping the impedances bellow 5
kΩ.

The stimulus will be presented on a gamma corrected Acer V173BM 17-inch LCD monitor, having
a refresh rate of 75 frames / second. Luminance output over time will be verified using a
luminance meter MavoSpot 2 USB (Gossen, GmbH, Nuremberg, Germany). The CSF pattern stimulus
will consist of black/white horizontal gratings (24° and 16° circular field, 98% contrast
and 102.28 candelas/m2 mean luminance), reversing at 15 reversals/second) with a duration of
25 seconds. A red spinning ring will be used as a fixation target with a diameter of 1 cm
and 1 mm of thickness. This target ring will be at the corner of four checks, centered on
the stimulus field.

Signals will band pass filtered (0.5-100 Hz), amplified (gain = 20,000), and averaged (at
least 300 sweeps). The voltage range of the analogue to digital (A/D) converter will be
programmed to (-) 1.25 V to (+) 1.25 V. Sweeps contaminated by eye blinks or gross eye
saccades will be rejected automatically over a threshold voltage of 50 μV. Synchronized
single-channel will be recorded, generating a time series of 384 data points per analysis
window (200 ms).

An automatic discrete Fourier transformation (FFT) will be applied to the PERG waveforms to
isolate the desired component at 15 rps. Other frequencies, such as those originating from
eye muscles will be rejected. The noise will be simultaneously isolated by multiplying
alternate sweeps by +1 and −1. The recording time will be approximately 1 minute and 40
seconds per eye. A test will be categorized as non-reliable if SNR < 3 and/or more than 4
artifacts. The PERG test results will be saved in an SQL database and presented in a report
form to be used for analysis.

The stimulus will be presented on a Diopsys mini-ganzfeld. Luminance output over time will
be verified using a luminance meter MavoSpot 2 USB (Gossen, GmbH, Nuremberg, Germany). The
MF stimulus will consist of white flashes flickering at 32Hz over a yellow background. The
onset and offset time will be of 10ms and 21.25ms respectively. White flash luminosity will
be 3.12 cd*s/m2 (312 cd/m2) over a yellow background of 28 cd/m2. A green dot with a
dimension of 1x1 mm will be used as a fixation target.

Signals will band pass filtered (0.5-100 Hz), amplified (gain = 20,000). The voltage range
of the analogue to digital (A/D) converter will be programmed to (-) 1.25 V to (+) 1.25 V.
Signal contaminated by eye blinks or gross eye saccades will be rejected automatically over
a threshold voltage of 50 μV. Synchronized single-channel will be recorded, generating a
time series of 128 data points per analysis window (62.5 ms).

An automatic discrete Fourier transformation (FFT) will be applied to the PERG waveforms to
isolate the desired component at 32Hz. Other frequencies, such as those originating from eye
muscles will be rejected. The recording time will be 20 seconds per eye.

A test will be categorized as non-reliable if Phase Variance is greater than 0.4 and/or if
the Magnitude Variance to Magnitude Ratio (VMR) is greater than 2.9 and/or if more than 4
artifacts are detected. The FERG test results will be saved in an SQL database and presented
in a report form to be used for analysis.

Inclusion Criteria:

- Both Male and Female.

- 18 and older (N/A).

- Patients will have repeatable abnormal SAP results (pattern standard deviation with p
≤5% and/or Glaucoma Hemifield Test outside normal limits), and glaucomatous optic
disc appearance (those with cup to disc area ratio, rim thinning or RNFL defects
indicative of glaucoma) and/or repeatable intraocular pressure ≥23 mmHg, in at least
one eye. The last SAP test of all participants will be classified following the
Glaucoma Staying System (GSS).

Exclusion Criteria:

- Younger than 18 years of age.

- A spherical refraction outside + 5.0 D and cylinder correction outside + 3.0 D.

- Intraocular surgery in the study eye (except non-complicated cataract or refractive
surgery performed less than 1 year before enrollment).

- Any prior vitrectomy

- Any prior macular or pan retinal photocoagulation laser

- History of neurologic condition known to affect visual function.

- Inability to obtain a reliable PERG/VEP test.