Retinal Oxygen Function After Radiation Therapy

Study Overview
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Brief Summary
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The investigators propose using retinal oximetry to assess for abnormalities in regional retinal oxygen consumption in previously- irradiated patients, and relate these abnormalities to changes in regional retinal function (i.e. visual field abnormalities). Since different regions of retina receive different radiation doses, the investigators will assess for a dose response as well.

Detailed Description
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Radiation therapy (RT) is a common treatment for patients with cancers of the sinonasal area, orbit, skull base, nasopharynx, and brain. Because of the close proximity of these targets to the eyes, the retina is often incidentally and unavoidably irradiated. As a result, some patients develop radiation retinopathy and possibly vision loss. Clinicopathologic studies suggest similar microvascular mechanisms for both radiation- and diabetic retinopathy: small vessel occlusion and ischemia that can lead to neovascularization, increased capillary permeability, and visual loss in the regions of retina perfused by damaged vasculature. UNC has a novel, non-invasive retinal imaging technology called a Retinal Oximeter which measures hemoglobin oxygen saturation of retinal vessels. The difference in oxygen saturation between a retinal arteriole and venule pair reflects the oxygen consumption of the retinal region supplied by that vessel pair.

Official Title
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Changes in Regional Retinal Oxygen Extraction and Function After Radiation Therapy

Conditions
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A History of Radiation Therapy for a Tumor in the Vicinity of the Retina(s)

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ≥ 18 years of age at the time of radiation therapy (no upper age limit) History of radiation therapy delivered at UNC-CH or Rex Hospital to the vicinity of the retina(s) ≥ 2 months prior to enrollment Estimated average dose to at least one quadrant of one retina ≥ 30 Gy Exclusion Criteria: History of diabetes, retinal vascular occlusions, glaucoma, retinitis pigmentosa, occipital stroke or any other ophthalmologic or systemic problem that may confound visual field results. Residual tumor within the visual pathway: retina, optic nerves, optic chiasm, optic radiations and brain.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 99 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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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Abnormalities in regional retinal oxygen extraction after incidental irradiation of the retina. | To identify abnormalities in regional retinal oxygen extraction in patients who have had previous incidental irradiation of the retina. | 2 months | 
| Prevalence of vision loss in patients with previous incidental irradiation of the retina | To determine the prevalence of regional retinal dysfunction (i.e. vision loss) in patients with previous incidental irradiation of the retina. | 2 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in retinal oxygen extraction compared to radiation dose | To correlate changes in retinal oxygen extraction to radiation dose. | 2 months | 
| Vision loss amount versus radiation dose. | To correlate retinal dysfunction (i.e. vision loss) to radiation dose. | 2 months | 
| Changes in retinal oxygen extraction as compared to vision loss. | To correlate changes in retinal oxygen extraction to retinal dysfunction (i.e. vision loss). | 2 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Sinus/nasal cancer