Color vision checkup
The biggest issues I see with this code is naming of Classes/Properties/Methods and proper separation of concerns.

I find the best way to think about separation of concerns is to think in terms of "has a" relationships to see if they make sense. For example, you might question whether a "Checkup has an employment status". When you put it that way, it's pretty clear that a Checkup doesn't make sense to have an employment status, but a Person might. It's pretty easy to fall into the trap of saying "I don't need to make a Person class because it's not that complex yet". This will come back to bite you later whether it's another developer that can't understand your code (maybe even yourself) or wishing you could more easily modify functionality because the elements are so tightly coupled.

Here's an example of how you might better organize your classes:

public class CheckUp
{
    public DateTime AppointmentTime { get; set; }
    public DateTime StartTime { get; set; }
    public DateTime EndTime { get; set; }

    public Clinician Clinician { get; set; }
    public Patient Patient { get; set; }

    // A type of test might be a ColorVisionTest.
    public List&lt;Test&gt; TestsRun { get; set; }
}

public class Person
{
    public String FirstName { get; set; }
    public String LastName { get; set; }
}

public class Clinician : Person
{
    public List&lt;Licenses&gt; Licenses { get; set; }
}

public class Patient : Person
{
    public List&lt;Checkups&gt; Checkups { get; set; }
}

public static class DatatableTestParser
{
    public static List&lt;Test&gt; ParseTests(DataTable dt)
    {
        // Parsing logic here.
    }
}


To keep harping on the separation of concerns, let's talk about a comment of yours:


  I am racking up my brain on how to create a Checkup Class, that can
  load the basic data form the data table


Typically you don't want to have something like a Checkup class also be concerned with parsing from things like a datatable. Again, a Checkup should only be concerned with being a Checkup and nothing more. You could have another class that did parsing from a DataTable or other data source, but the key is to separate it from the Checkup itself. Hopefully this helps.