Macular Vessel Density and Foveal Avascular Zone Changes in Exfoliation Glaucoma vs Primary Open Angle Glaucoma vs Exfoliation Syndrome: An Optical Coherence Tomography Angiography Study

Glaucoma is an eye disease that results in damage to cells in the back of the eye known as the retina and poses a major risk to global public health. Primary open angle glaucoma (POAG) is the most common type of glaucoma in the United States. Exfoliation syndrome (XFS) is an age-related systemic disorder of the extracellular matrix in which white fibrillary material (exfoliation material, XFM), is deposited in different tissues of the body, including the anterior chamber of the eye. XFS is associated with many systemic vascular and ischemic issues. It is the most common recognizable cause of open-angle glaucoma worldwide. This is called exfoliation glaucoma (XFG) and accounts for the majority of cases of glaucoma in some countries. Glaucomatous damage to the macula which is responsible for central vision located in the retina is has been well documented in recent studies. Optical coherence tomography angiography (OCTA) is a new noninvasive imaging modality that can measure blood vessel density at the macula by detecting red blood cell movement in the eye. Previous OCTA studies have demonstrated decreased vessel density around the macula in patients due to damage from POAG. To date, there have been no published studies of XFS or XFG using OCTA. Due to the systemic vascular issues associated with XFS and XFG we have chosen to investigate the possible vascular differences that exist between POAG, XFG, XFS, and healthy controls using OCTA. We will use OCTA to look specifically changes at the vessels at the macula.

Inclusion Criteria:

- Age ≥40

- No gender preference

- BCVA 20/50 or better and refractive error < ±6.00 diopters.

- Written informed consent.

- Eyes with primary open angle glaucoma, exfoliation syndrome, exfoliation glaucoma, and a control group will be enrolled in the study.

- POAG eyes are defined by clinical findings consistent with glaucomatous optic neuropathy- vertical cup-to-disc ratio ≥ 0.6, asymmetry of cup-to-disc ratio ≥ 0.2 between eyes, and presence of localized retinal nerve fiber layer (RNFL) or neuroretinal rim defects in absence of any other abnormalities that could explain such findings on fundus examination 31. Eyes will have open anterior chamber angles and history of elevated IOP (>24 mmHg).

- Exfoliation glaucoma eyes will have glaucomatous optic neuropathy as defined above but have signs of exfoliation material deposition at the anterior lens capsule and/or pupillary margin.

- Exfoliation syndrome eyes will have signs of exfoliation material deposition without demonstrable glaucomatous damage to the optic nerve or RNFL/GCC.

- Glaucoma hemifield test (GHT) result outside normal limits on at least two consecutive reliable examinations or presence of at least three contiguous test points on pattern standard deviation (PSD) plot with P< 1%, with at least one of P < 0.5%, not including points at edge of field or those directly above or beneath blind spot.

- Reliable and reproducible visual field defects on Visual Field examination with criteria of fixation losses of ≤ 30%, false positives ≤15%, and false negatives ≤ 20%.

- Controls will have IOP < 21 mmHg with no signs of glaucomatous optic neuropathy as defined above and normal retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) noted on OCT.

Exclusion Criteria: 

- Medical conditions that will impact VF examination such as intracranial lesions, or retinal vaso-occlusive diseases like retinal vascular occlusion. History of other optic diseases that can cause optic nerve head defects.

- History of retinal disease such as hypertensive retinopathy, diabetic retinopathy, or age related macular degeneration. 

- Pathological myopia with epiretinal membrane, macular hole, or retinal detachment.

- BCVA worse than 20/50 and/or refractive error >±6.00 diopters. 

- Unreliable and nonreproducible visual fields- fixation loss of ≥ 30%, false positives ≥15%, and false negatives ≥ 20%.

- Eyes with poor OCTA image quality: Images not used if poor fixation causing motion artifact, media opacity blocking vessel signal, or segmentation error causing poor outline of vascular network.

Conditions:
• Primary Open Angle and Exfoliative Glaucoma