How to find by model if the model is not complete?

Question

Laravel

On the main page there is a Request that receives data from the form

public function index(Request $request)
    {
        if ($request->surname != null || $request->first_name != null || $request->second_name != null || $request->birthday != null) {
            $patient = new Patient();
            $patient->surname = $request->surname;
            $patient->first_name = $request->first_name;
            $patient->second_name = $request->second_name;
            $patient->birthday = $request->birthday;
            $patients = Patient::orWhere('surname', $patient->surname)
                ->orWhere('first_name', $patient->first_name)
                ->orWhere('second_name', $patient->second_name)
                ->orWhere('birthday', $patient->birthday)
                ->get();
            return view('staff_doctor.patient.index', compact('patients', 'patient'));
        } else {
            $patients = Patient::all()->sortBy('surname')->sortBy('first_name')->sortBy('second_name')->sortBy('birthday');
            return view('staff_doctor.patient.index', compact('patients'));
        }
    }

If the entire form is filled out, then it finds the patient in the database, if part of it does not find anyone.
How to make it so that only the last name and birthday fields are filled in and search for all matches in the database.
For example, if I search for 01/01/1911, then it will return:
Ivanov Ivan Ivanovich 01/01/1991
Petrov Petr Petrovich 01/01/1991
And if Ivanov:
Ivanov Ivan Ivanovich 01/01/1991
Ivanov Ivan Ivanovich 02/01/1991