The aim of this study was to evaluate structural and functional improvement after lowering intraocular pressure (IOP) in patients with glaucoma using Spectral Domain Optical Coherence Tomography (SD-OCT), Visual Field (VF) testing, and Visual Evoked Potential (VEP).
Glaucoma exhibits characteristic changes to the optic nerve in the back of the eye. The optic nerve is formed when fibers that overlay the retina come together. This layer is called the retinal nerve fiber layer (RNFL). Optical Coherence Tomography (OCT) is a machine that scans eyes and has the capability of measuring thickness of various layers in the retina and RNFL. This provides important anatomical information. VEP (visual evoked potential) is an imaging system that measures electrical signals from the eye to the brain by using electrodes placed on the forehead and back of head. This is similar in principal to an electrocardiogram of the heart. Visual field testing is done to evaluate the extent of side vision loss caused by various diseases of the eye, including glaucoma. This testing is performed as you stare at a small light directly in front of your eye while lights flash one at a time in every direction on a screen surrounding the central light. You push a button each time you see a flash out of the corner of your eye. Lowering intraocular pressure (IOP) in the eye has been shown to result in reversal of glaucoma changes of the optic nerve in some patients. It has also been suggested that improvement in function (visual field) has been associated with improved optic nerve appearance. This study seeks to provide evidence for reversal of disc appearance and visual function following IOP lowering interventions.
Study Type
OBSERVATIONAL
Enrollment
61
Optical Coherence Tomography (OCT) is a machine that scans eyes and has the capability of measuring thickness of various layers of the retina and nerve fiber layer (NFL).
Visual Evoked Potential (VEP) is an imaging system that measures electrical activity from the eye to the brain by using electrodes placed on forehead and back of the head similar to electroencephalogram (EEG).
Humphrey Visual Field (HVF) is a test done to evaluate how much peripheral (side) vision has been lost due to glaucoma.
Visual Field Mean Deviation
Visual field mean deviation as measured in decibels (dB) is the amount of visual field loss compared to age matched controls (people with no eye diseases or visual field loss). Brightness of the flashes of light used to test peripheral vision during a visual field test is measured in decibels. Brighter light has lower number in decibels. The dimmer the light, the higher the number in decibels with a range of 0 to 40 dB.
Time frame: 12 months
Retinal Nerve Fiber Layer (RNFL) Thickness Measurement
Retinal nerve fiber layer (RNFL) thickness in different quadrants of optic nerve and macula are measured pre and postoperatively to evaluate structural changes.
Time frame: 12 months
Average Cup to Disc Ratio
Cup to disc ratio is used to evaluate structural changes comparing the size of the cup to the size of the disc during dilated ophthalmic examination. High eye pressure can cause the cup to enlarge, closer to the size of the disc. This measurement is used to follow progression in glaucoma. A normal range for cup to disc ratio would be 0.0 to 0.4. Advanced glaucoma would be 0.8 to 0.9 cup to disc ratio.
Time frame: 12 months
Visual Evoked Potential Amplitudes
VEP amplitudes at high contrast as measured in microvolts (μV). Electroencephalogram (EEG) measures electrical activity in the brain. VEP measures electrical activity in areas of the brain responsible for vision by using EEG electrodes. The amplitude measurement is the peak of the energy generated (strongest strength of the signal) from the eye's response to the visual stimulus during the VEP.
Time frame: 12 months
Visual Evoked Potential Latency
VEP latency at high contrast as measured in milliseconds (ms). Electroencephalogram (EEG) measures electrical activity in the brain. VEP measures electrical activity in areas of the brain responsible for vision by using EEG electrodes. VEP latencies measure the duration in time of the energy generated (duration of the signal) from the eye's response to a visual stimulus during the VEP.
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Time frame: 12 months
Visual Field
Visual field pattern standard deviation in decibels (dB). Visual field results compare visual field loss to age matched controls (people with no eye diseases or visual field loss). Brightness of the flashes of light used to test peripheral vision during a visual field test is measured in decibels. With a localized defect in the visual field, pattern standard deviation (PSD) quantifies amount of loss and progression of glaucoma when in the beginning stages of the disease.
Time frame: 12 months