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(1) With persistent symptoms emerging as a possible global consequence of COVID-19, the need to understand, diagnose, and treat them is paramount. This systematic review aims to explore the potential of optical coherence tomography (OCT) and/or optical coherence tomography angiography (OCTA) in effectively diagnosing long COVID. (2) The database PubMed and, to reduce selection bias, the AI research assistant Elicit, were used to find relevant publications in the period between February 2021 and March 2024. Included publications on OCT and OCTA analysis of participants with acute COVID symptoms, those after recovery, and participants with long COVID symptoms were organized in a table. Studies with participants under the age of 18, case reports, and unrelated studies, such as pure slit-lamp examinations and subgroup analyses were excluded. (3) A total of 25 studies involving 1243 participants and 960 controls were reviewed, revealing several changes in the posterior eye. Long COVID participants displayed significant thinning in retinal layers in the OCT, including the macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL). Divergent findings in recovered cohorts featured mRNFL reduction, GCL increase and decrease, and GCL-IPL decrease. Long COVID OCTA results revealed reduced vessel density (VD) in the superficial capillary plexus (SCP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). In recovered patients, SCP consistently showed a reduction, and DCP exhibited a decrease in five out of six publications. The foveal avascular zone (FAZ) was enlarged in five out of nine publications in recovered participants. (4) During various stages of COVID-19, retinal changes were observed, but a comparison between long COVID and recovered cohorts was aggravated by diverse inclusion and exclusion criteria as well as small sample sizes. Changes in long COVID were seen in most OCT examinations as thinning or partial thinning of certain retinal layers, while in OCTA a consistently reduced vessel density was revealed. The results suggest retinal alterations after COVID that are variable in OCT and more reliably visible in OCTA. Further research with larger samples is important for advancing long COVID diagnosis and management. [ABSTRACT FROM AUTHOR]