Intraocular pressure variation (ocular hypertension) in diabetes mellitus

Ocular hypertension (OHT), defined as increased intraocular pressure (IOP, > 21 mmHg) in eyes without optic disc changes or visual field changes, is a condition that puts an eye at higher risk of developing glaucomatous optic neuropathy and may be related to the translaminar pressure gradient, individual differences in IOP-related glaucoma susceptibility, effects of arterial blood pressure on the optic nerve head, and vasospastic factors. IOP remains the most common modifiable risk factor to protect eyes against the development of glaucoma. The association between OHT and diabetes mellitus (DM) is poorly understood, although ocular effects of both conditions are related to vascular compromise of retinal and optic nerve circulation. Increased IOP in diabetic patients is attributable to increased aqueous osmotic gradient and accumulation of extracellular matrix constituents in the trabecular meshwork. Autonomic dysfunction and genetic factors may also play a role. Apart from eyes without diabetic retinopathy (DR) changes, OHT can also be observed in eyes with DR, where it can develop with or without antecedent vitreoretinal intervention. For example, photocoagulation of the retina in earlier stages of proliferative DR protects against the development of OHT, whereas intraocular silicone oil injection promotes it. While IOP has been directly implicated as an independent risk factor for DR, the retinopathy in DM is also related to comorbidities, like hypertension and heart disease, that are also correlated with OHT. All these factors are discussed in a comprehensive review exploring the association of OHT and DM in detail.