Question

Epidemiology subject

A study was conducted to determine long-term consequences of surgical treatment of patients with cataracts. For 174 patients who underwent surgery and 103 other patients with cataracts who did not, periodic interviews were conducted to assess whether they had been in a motor vehicle accident (MVA) and to estimate the number of hours spent driving a vehicle during the 2-year follow-up period. The results of the study are as follows:

Group	Number of Patients	Number of Patients in a MVA	Number of Hours of Driving
Surgery	174	27	126,174
No Surgery	103	23	57,103

1. Calculate a measure of association to assess whether cataract surgery is associated with a MVA and interpret your answer numerically.

2. What is the excess risk of MVA among persons not undergoing surgery compared to those who have the surgery? Interpret your answer numerically.

   A study was conducted to determine long-term consequences of surgical treatment of patients with cataracts. For 174 patients who underwent surgery and 103 other patients with cataracts who did not, periodic interviews were conducted to assess whether they had been in a motor vehicle accident (MVA) and to estimate the number of hours spent driving a vehicle during the 2-year follow-up period. The results of the study are as follows:

   Group	Number of Patients	Number of Patients in a MVA	Number of Hours of Driving
   Surgery	174	27	126,174
   No Surgery	103	23	57,103

3. Calculate a measure of association to assess whether cataract surgery is associated with a MVA and interpret your answer numerically.

4. What is the excess risk of MVA among persons not undergoing surgery compared to those who have the surgery? Interpret your answer numerically.

Answer 1