Optic Nerve Head Shape as a Predictor of the Formation of Acquired Pits of the Optic Nerve (APONs)

Study Overview
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Brief Summary
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Acquired pits of the optic nerve (APONs) are an area of focal loss of neural tissue associated with a discrete area of depression/excavation within the optic cup at the level of the lamina cribrosa. It is commonly associated with glaucoma and can be seen on the optic disc when examining the back of a patient's eye. It causes a characteristic visual field defect in the central 5-10 degrees of vision which has a significant impact of a patient's daily activities. There is no treatment to restore vision once it has formed. Previous studies suggest mechanical stress across this part of the eye may have role in the formation of APONs. The investigators therefore hypothesise that if a patient has a more elliptical shaped optic disc, which would have more irregular mechanical stress across it, it may have a higher risk of an APON forming. Patients with glaucoma attending the ophthalmology department at University Hospital of Wales have regular photographs taken of the optic nerve/optic disc as part of their routine clinical care in order to monitor the condition. The research team, who are all practicing ophthalmologists in the department, will review anonymised photographs to find optic discs with APONs, and another group with glaucoma but no APONs to use as a control. The research team will then measure the dimensions of the optic disc to determine if APONs are more common in optic discs with a more elliptical shape. The patients' clinical notes will then need to be accessed to collect data on the age, sex and diagnosis. This data will be anonymised using ID numbers once collected. The final outcomes of the study will the average measured dimensions of the optic disc in each group, and the position that the APON occurs.

Official Title
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Optic Nerve Head Shape as a Predictor of the Formation of Acquired Pits of the Optic Nerve (APONs)

Conditions
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Glaucoma

Intervention / Treatment
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* Other: No intervention. Purely observation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Documented diagnosis of primary open angle glaucoma (POAG) or normal tension glaucoma (NTG) Under the care of the ophthalmology department at University Hospital of Wales Available optic disc photograph Presence of an APON for disease group, no APON for control group Exclusion Criteria: No documented diagnosis of POAG/NTG Other form of glaucoma - e.g. traumatic glaucoma/juvenile glaucoma Poor photograph quality Optic disc tilted so that the margin is obscured and cannot be demarcated Coexisting disc pathology, e.g. congenital optic disc pit

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 110 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| APON<br>Retrospective review of routine clinical images from patients with an acquired pit of the optic nerve (APON), and a documented diagnosis of primary open angle glaucoma or normal tension glaucoma | Other: No intervention. Purely observation<br>* Retrospective image analysis of the shape of the optic nerve head in both groups<br>|
| No APON control<br>Retrospective review of routine clinical images from patients with NO acquired pit of the optic nerve (APON), and a documented diagnosis of primary open angle glaucoma or normal tension glaucoma | Other: No intervention. Purely observation<br>* Retrospective image analysis of the shape of the optic nerve head in both groups<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Optic disc radius ratio | Comparison of the ratio of the maximum/minimum optic disc radius for optic discs with APONs and optic discs with glaucoma but no APON. | 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The percentile rank of the disc radius at the position of the APON | The percentile rank of the disc radius at the position of the APON | 6 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Glaucoma