You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

Purpose: The purpose of this study was to compare the retinal vascular caliber of COVID-19 patients with that of healthy subjects. Methods: This was a prospective case-control study. Forty-six patients who had COVID-19 were successfully treated, and 38 age- and gender-matched healthy subjects were enrolled in this study. Fundus photography was taken using fundus fluorescein angiography (FA; Visucam 500; Carl Zeiss Meditec, Jena, Germany). Retinal vascular caliber was analyzed with IVAN, a semi-automated retinal vascular analyzer (Nicole J. Ferrier, College of Engineering, Fundus Photography Reading Center, University of Wisconsin, Madison, WI, USA). Central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and artery-vein ratio (AVR) were compared between groups. Results: The mean age was 37.8 +/- 9.5 years in the COVID-19 group (n = 46) and 40 +/- 8 years in the control group (n = 38) (p = 0.45). The mean CRAE was 181.56 +/- 6.40 in the COVID-19 group and 171.29 +/- 15.06 in the control group (p = 0.006). The mean CRVE was 226.34 +/- 23.83 in the COVID-19 group and 210.94 +/- 22.22 in the control group (p = 0.044). AVR was 0.81 +/- 0.09 in the COVID-19 group and 0.82 +/- 0.13 in the control group (p = 0.712). Conclusion: Patients who had COVID-19 have vasodilation in the retinal vascular structure after recovery. As they may be at risk of retinal vascular disease, COVID-19 patients must be followed after recovery.
["Diagnosis", "Treatment"]