Belgian Shepherd Dog - Complete blindness by eight weeks old. Cone degeneration
Alaskan Malamute - Temporary loss of vision in daylight (hemeralopia) at eight to ten weeks old. There is a purely rod cell retina by four years old. Cone-rod dystrophy
Glen of Imaal Terrier - CRD3 results in gradual blindness with onset around 4 years of age (often detectable as retinal thinning as early as 3 years of age). Caused by a mutation in gene ADAM9, the disease is analogous to CRD9 in humans. A genetic test is now available from Optigen, LLC, that will identify whether a dog is affected, a carrier (heterozygous), or clear. Progressive rod-cone degeneration (PRCD)
This is a disease with normal rod and cone cell development but late onset degeneration of the rod cells that progresses to the cone cells. It is inherited as an autosomal recessive trait and has been linked to the ninth canine chromosome. Poodle - Night blindness by three to five years old, blind by five to seven years old. English Cocker Spaniel - Occurs late in life, usually at four to eight years old. American Cocker Spaniel - Night blindness by three to five years old, blind one to two years later. Labrador Retriever - Night blindness by four to six years old, blind at six to eight years old. Portuguese Water Dog
Chesapeake Bay Retriever
Australian Cattle Dog
American Eskimo Dog
Nova Scotia Duck Tolling Retriever

X-linked PRA
This condition is linked to the X chromosome. Siberian Husky - Night blindness by two to four years old.
Nasal congestion is the blockage of nasal breathing usually due to membranes lining the nose becoming swollen from inflamed blood vessels. Background
In about 85% of cases, nasal congestion leads to  mouth breathing rather than nasal breathing. According to Jason Turowski, MD of the Cleveland Clinic, "we are designed to breathe through our noses from birth—its the way humans have evolved." This is referred to as "obligate nasal breathing. "Nasal congestion can interfere with hearing and speech. Significant congestion may interfere with sleep, cause snoring, and can be associated with sleep apnea or upper airway resistance syndrome. In children, nasal congestion from enlarged adenoids has caused chronic sleep apnea with insufficient oxygen levels and hypoxia, as well as right-sided heart failure. The problem usually resolves after surgery to remove the adenoids and tonsils, however the problem often relapses later in life due to craniofacial alterations from chronic nasal congestion. Causes
Allergies, like hay fever, allergic reaction to pollen or grass
Common cold or influenza
Rhinitis medicamentosa, a condition of rebound nasal congestion brought on by extended use of topical decongestants (e.g., oxymetazoline, phenylephrine, xylometazoline, and naphazoline nasal sprays)
Sinusitis or sinus infection
Narrow or collapsing nasal valve
Pregnancy may cause women to suffer from nasal congestion due to the increased amount of blood flowing through the body. Nasal polyps
Gastroesophageal reflux disease (theorized to cause chronic rhinosinusitis- the "airway reflux paradigm")
COVID-19

Nasal obstruction
Nasal obstruction characterized by insufficient airflow through the nose can be a subjective sensation or the result of objective pathology.