Buys YM, Alasbali T, Jin YP et al. Effect of sleeping in a head-up position on intraocular pressure in patients with glaucoma. Ophthalmology 2010; 117: 1348-51 

In a nutshell

Seventeen eyes of 17 patients with glaucoma and a new disc haemorrhage despite well-controlled IOP were evaluated in a sleep laboratory on two consecutive nights, the first lying flat and the second in a 30-degree head-up position. Intraocular pressures and BP were measured every two hours from 6pm to 8am.

For the awake period (6pm, 8pm, 10pm and 8am) the subjects were sitting for both nights; for the sleep period (midnight, 2am, 4am and 6am) they were supine for the first night and 30-degree head-up for the second night.

 There were no significant differences between the two study visits in IOP during the awake period. During the sleep period the mean IOP was 3.2mmHg lower in the 30-degree head-up position compared with the flat position. This reduction was 20% or more in 35% (6/17) of patients. There was no difference in BP or ocular perfusion pressure.

Second opinion

It has been reported that IOP increases when lying flat by as much as 6mmHg in both normal patients and those with glaucoma. This supine increase may play a role in the progression of glaucoma. Supine increases in IOP are likely to be due to increased episcleral venous pressure.

Optic disc haemorrhages have been associated with glaucoma progression. Glaucoma medication such as timolol has little IOP-lowering effect at night. Prostaglandin analogues are also less effective during the nocturnal period.

The main limitation of the study is the small number examined with normal IOP during office hours. There was no monitoring of intracranial pressure, which may change in the head-up position and influence trans-laminar pressure gradients. 

The verdict

• A 30 degree head-up position lowers nocturnal IOP
• Mean IOP was 20% lower in one-third of patients
• Further studies are required to determine whether positioning can slow or arrest progressive disc damage
• Clinicians should consider recommending simple postural changes to patients with progressive glaucoma despite good IOP readings in office hours.

Joseph A Coleiro
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