| Value | Category | Cases | |
|---|---|---|---|
| 1 | No, no difficulty at all | 20863 | 
                                                                 
                                    
                                    99.1%
                                 
                                                             | 
                                                        
                    
| 2 | Yes, some difficulty | 140 | 
                                                                 
                                    
                                    0.7%
                                 
                                                             | 
                                                        
                    
| 3 | Yes, a lot of difficulty | 31 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             | 
                                                        
                    
| 4 | Cannot see at all | 16 | 
                                                                 
                                    
                                    0.1%
                                 
                                                             |