I want to detect iris and measure its diameter in python opencv?

Question

enter image description hereI used mediapipe for detecting iris in python ,it detects and the problem is if eye closed means circle found around the iris and how to overcome this and measure the iris diameter
It detects iris in realtime ,i used web cam for detecting iris ,if any movement happened two circles found and how to overcome this error

And this is my code

import cv2 as cv
import numpy as np
import mediapipe as mp

mp_face_mesh = mp.solutions.face_mesh

LEFT_EYE = [362, 382, 381, 380, 374, 373, 390, 249, 263, 466, 388, 387, 386, 385, 384, 398]
RIGHT_EYE = [33, 7, 163, 144, 145, 153, 154, 155, 133, 173, 157, 158, 159, 160, 161, 246]

# irises Indices list
LEFT_IRIS = [474, 475, 476, 477]
RIGHT_IRIS = [469, 470, 471, 472]

cap = cv.VideoCapture(0)

with mp_face_mesh.FaceMesh(
        max_num_faces=1,
        refine_landmarks=True,
        min_detection_confidence=0.5,
        min_tracking_confidence=0.5
) as face_mesh:
    while True:
        ret, frame = cap.read()
        if not ret:
            break
        frame = cv.flip(frame, 1)

        rgb_frame = cv.cvtColor(frame, cv.COLOR_BGR2RGB)
        img_h, img_w = frame.shape[:2]
        results = face_mesh.process(rgb_frame)
        mask = np.zeros((img_h, img_w), dtype=np.uint8)

        if results.multi_face_landmarks:
          

            mesh_points = np.array([np.multiply([p.x, p.y], [img_w, img_h]).astype(int)
                                    for p in results.multi_face_landmarks[0].landmark])

       

            (l_cx, l_cy), l_radius = cv.minEnclosingCircle(mesh_points[LEFT_IRIS])
            (r_cx, r_cy), r_radius = cv.minEnclosingCircle(mesh_points[RIGHT_IRIS])
            center_left = np.array([l_cx, l_cy], dtype=np.int32)
            center_right = np.array([r_cx, r_cy], dtype=np.int32)
            cv.circle(frame, center_left, int(l_radius), (0, 255, 0), 2, cv.LINE_AA)
            cv.circle(frame, center_right, int(r_radius), (0, 255, 0), 2, cv.LINE_AA)

            cv.circle(mask, center_left, int(l_radius), (255, 255, 255), -1, cv.LINE_AA)
            cv.circle(mask, center_right, int(r_radius), (255, 255, 255), -1, cv.LINE_AA)

        cv.imshow('Mask', mask)
        cv.imshow('img', frame)
        key = cv.waitKey(1)
        if key == ord('q'):
            break
cap.release()
cv.destroyAllWindows()