Optic Nerve Head Structural Response to IOP Elevation in Patients With Keratoconus

Study Overview
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Brief Summary
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The mechanism by which vision loss in glaucoma occurs is still unknown, but it is clear that increased Intraocular Pressure (IOP) is a major risk factor. It is also thought that the lamina cribrosa (LC) is a site of primary damage during the pathogenesis of the disease. The changes caused by intraocular pressure (IOP) modulation at the level of the optic nerve head and LC will be evaluated in the present study. Subjects with keratoconus exhibit abnormal collagen properties that can impair their LC behavior. By evaluating their lamina biomechanical response we can advance our understanding on the role of the lamina in glaucoma pathogenesis. A better understanding of the process will ultimately lead to improved detection and management of glaucoma. It is hypothesized that subjects with keratoconus have an abnormal biomechanical response of the lamina cribrosa in response to IOP modulation.

Official Title
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Optic Nerve Head Structural Response to IOP Elevation in Patients With Keratoconus

Conditions
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Keratoconus, Glaucoma

Intervention / Treatment
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* Device: Ophthalmodynamometer
* Device: Goldmann applanation tonometer
* Device: Pentacam
* Device: ORA
* Device: Optical Coherence Tomography (OCT)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Candidates must meet the following inclusion criteria in order to participate in the study. Ability to provide informed consent and to understand the study procedures Keratoconus: Clinical diagnosis of keratoconus Central thinning of the cornea Abnormal posterior ectasia. Glaucoma: Glaucomatous ONH abnormality: rim thinning, notching, undermining (excavation) or diffuse or localized RNFL defects that are characteristic of glaucoma. Two consecutive abnormal SITA standard perimetry tests with GHT outside normal limits. Exclusion Criteria: Candidates that meet any of the exclusion criteria at baseline will be excluded from study participation. Media opacity (e.g. lens, vitreous, cornea). Strabismus, nystagmus or a condition that would prevent fixation. Diabetes with evidence of retinopathy. Previous intraocular surgery or ocular trauma (with the exception of laser procedures and subjects that have undergone uneventful cataract surgery more than 6 months from enrollment date). Neurological and non-glaucomatous causes for visual field damage. Any intraocular non-glaucomatous ocular disorders.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 90 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Subjects With Keratoconus<br> | Device: Ophthalmodynamometer<br>* The ODM (Baillart ophthlmodynamometer) is a disc attached to a piston that induces a controlled force on a fixed area. The device will be used to apply a pressure within the range of 10 mmHg - 50 mmHg 4 times to each eye. Each increase of pressure will last approximately 30 seconds. The device is FDA approved and will be used as routinely used in clinical practice<br>Device: Goldmann applanation tonometer<br>* The Goldmann applanation tonometer (Haag-Streit, Basel, Switzerland) measures the IOP after the eye is numbed with a drop of anesthetic (proparacaine), which is approved by the FDA. Proparacaine is part of routine patient care using a tonometer regardless of participation in this study. The instrument's tip lightly touches the surface of the cornea and the IOP is measured. The device is FDA approved is routinely used in clinical practice.<br>Device: Pentacam<br>* This device maps the cornea and provides pachymetry, topography and corneal aberration maps. The device is FDA approved and routinely used in clinical practice.<br>Device: ORA<br>* ORA is an air puff tonometer that applies controlled force to flattens the cornea and provides the corneal hysteresis and corneal resistance factor. The device is FDA approved and routinely used in clinical practice.<br>Device: Optical Coherence Tomography (OCT)<br>* OCT is a non-contact,real-time, high resolution, and reproducible imaging modality that provides in-vivo optical cross-sectional scanning of the retina, the ONH and of the anterior segment structures including the cornea. Clinical staff will perform subject testing, not research coordinators. Information about these non-FDA approved OCTs and the multi-modal adaptive optics system can be found in appendices A, B, C, and D. With all devices, the participant sits in a slit lamp like frame. A low power laser light is projected toward the back of their eyes while the subject fixates on a target. None of the systems produce harmful radioactive radiation.<br>|
| Active Comparator: Subjects with Glaucoma<br> | Device: Ophthalmodynamometer<br>* The ODM (Baillart ophthlmodynamometer) is a disc attached to a piston that induces a controlled force on a fixed area. The device will be used to apply a pressure within the range of 10 mmHg - 50 mmHg 4 times to each eye. Each increase of pressure will last approximately 30 seconds. The device is FDA approved and will be used as routinely used in clinical practice<br>Device: Goldmann applanation tonometer<br>* The Goldmann applanation tonometer (Haag-Streit, Basel, Switzerland) measures the IOP after the eye is numbed with a drop of anesthetic (proparacaine), which is approved by the FDA. Proparacaine is part of routine patient care using a tonometer regardless of participation in this study. The instrument's tip lightly touches the surface of the cornea and the IOP is measured. The device is FDA approved is routinely used in clinical practice.<br>Device: Pentacam<br>* This device maps the cornea and provides pachymetry, topography and corneal aberration maps. The device is FDA approved and routinely used in clinical practice.<br>Device: ORA<br>* ORA is an air puff tonometer that applies controlled force to flattens the cornea and provides the corneal hysteresis and corneal resistance factor. The device is FDA approved and routinely used in clinical practice.<br>Device: Optical Coherence Tomography (OCT)<br>* OCT is a non-contact,real-time, high resolution, and reproducible imaging modality that provides in-vivo optical cross-sectional scanning of the retina, the ONH and of the anterior segment structures including the cornea. Clinical staff will perform subject testing, not research coordinators. Information about these non-FDA approved OCTs and the multi-modal adaptive optics system can be found in appendices A, B, C, and D. With all devices, the participant sits in a slit lamp like frame. A low power laser light is projected toward the back of their eyes while the subject fixates on a target. None of the systems produce harmful radioactive radiation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| LC measurements measured in microns | These micron measurements will be obtained from in vivio OCT images | 1 Day | 
| Anterior laminar displacement measured in microns | These micron measurements will be obtained from in vivio OCT images | 1 Day |