python django latitude longitude filter in queryset

Question

I have a field like

class MyModel(models.Model):
    latitude = models.CharField(max_length=100, db_index=True)
    longitude = models.CharField(max_length=100, db_index=True)

Lets say I have lat long value like

myval = (27.66469717424158, 85.30983049711507)

Here I want to find all the objects in MyModel which are less than 10 KM in distance from myval

I looked into geopy library. I think it is useful after I get the data from queryset.

How to achieve this ?