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

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

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.

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.