Redefinition of the disease is the easy part, according to Dr. Pasquale.
When measuring IOP, the value is elevated in most patients, although notably 90% of Japanese patients have normal values.
However, the slit lamp examination does not show the secondary cause of elevated IOP. Importantly, there is progressive excavation of the neural retinal rim with associated visual field loss.
Dr. Pasquale pointed to the importance of IOP in POAG. Compared with individuals with IOP less than 17 mm Hg, those with IOP of 35 mm Hg or higher have a 39-fold increased risk of POAG.
Similarly, when the body mass index (BMI) is 33 or higher (indicating obesity), the risk of type 2 diabetes also is 39-fold compared with someone with a BMI below 22.
“This very high effect on size suggests IOP is in the causal pathway of the disease,” he said.
Ophthalmologists must stop equating high IOP and optic nerve damage with POAG, Dr. Pasquale suggested. In addition, the term “low-pressure glaucoma” is confusing and should be abandoned. The situation seems to be much more complicated.
While POAG equals high-tension glaucoma and normal-tension glaucoma, his discomfort lies in the fact that suggests the two conditions are separate entities.
“They are not,” he said. “There is clear overlap between the two.”