Sleep apnoea is risk factor for NTG

Obstructive sleep apnoea syndrome is a significant risk factor for normal-tension glaucoma (NTG), according to a research article newly published by BMC Ophthalmology.

Study author Dr Gorkem Bilgin, of Hacettepe University Gün Hospital, recommends that ophthalmologists obtain sleep histories from all their patients who have NTG - asking questions about snoring, night-time gasping and choking, daytime sleepiness and morning headaches - and refer patients for polysomnography (PSG) testing and nasal continuous positive airways pressure therapy.

The investigation included 24 patients with NTG and 24 age- and sex-matched controls who had similar systemic risk factors for diabetes mellitus, hypertension and hypercholesterolemia. All study participants underwent overnight PSG testing so that sleep apnoea could be diagnosed and the Apnoea-Hypopnoea Index (AHI) could be calculated.

Sleep was continuously measured according to standardized criteria from the American Academy of Sleep Medicine. Apnoea was defined as a 90% decrease in the amplitude of airflow signal compared with baseline airflow that lasted 10 or more seconds. Hypopnoea was defined as a decrease in airflow of at least 50% that lasted 10 or more seconds and was associated with a decrease in oxygen saturation from baseline of at least 3%. The AHI was calculated using the total number of apneas and hypopneas per hour of sleep.

Dr Bilgin found no statistically significant differences between the study’s patients and controls regarding age, gender, systemic risk factors, smoking, neck circumference and body mass index (P > 0.05). Ten (41.7%) patients with NTG and 3 (12.5%) of the controls had sleep apnoea; this difference between the two groups was statistically significant (P

Previous research has suggested that optic nerve head perfusion and oxygenation may be affected by the transient hypoxemia and increased vascular resistance created by sleep apnoea, causing glaucomatous optic neuropathy, Dr Bilgin noted. Other studies have examined the prevalence of sleep apnoea in those with NTG, but the author believes this study was the first to use age- and sex-matched controls. Also, because this study used a cutoff point of 20 for the AHI, Dr Bilgin said, false-positive findings were reduced, providing a more accurate assessment of the association between sleep apnoea and NTG.

To read the full study, click here.