Sir,

We report suspicious glaucomatous field changes improving with continuous positive airway pressure (CPAP) in a patient diagnosed with obstructive sleep apnoea syndrome (OSAS).

Case report

A 49-year-old man reported difficulty in focusing for near, intermittent diplopia and blurred vision. He complained of snoring, hypersomnolence, and a family history of glaucoma. Right visual acuity was 6/4 with +0.75/+0.50 × 55, Left 6/5 with +1.50 DS. N5 for near with +2.00 add.

Intraocular pressure on applanation tonometry was 17 mmHg in both eyes. Discs were healthy with 0.4 cup–disc ratio. Cover tests and ocular motility were normal. Automated Humphreys 24-2 visual field (VF) test showed a bilateral glaucomatous upper arcuate scotoma with good reliability indices, test duration of 10 min (Figure 1) that was reproducible. Gonioscopy did not show evidence of narrow angles. Thyroid function tests and MRI were normal.

Figure 1
figure 1

Humphrey's Visual field–pattern deviation: right eye before treatment (test duration: 10 min 16 s); left eye before treatment (test duration: 9 min 37 s).

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Oximetry diagnosed severe obstructive sleep apnoea with a 58% lowest desaturation point. CPAP relieved symptoms immediately. Over the next 2 years, right VF improved with reduced test duration (Figure 2).

Figure 2
figure 2

Humphrey's Visual field–pattern deviation: right eye after treatment (test duration: 3 min 49 s); left eye after treatment (test duration: 3 min 54 s).

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Comment

Obstructive sleep apnoea is characterized by intermittent pharyngeal airway closure with cessation of breathing during sleep, terminated by arousal. It presents as excessive daytime fatigue with decreased cognitive abilities.

OSAS is diagnosed by overnight polysomnography and calculating respiratory disturbance index, that is, total apnoeas and hypopnoeas divided by the hours of sleep. Patients are treated with CPAP during sleep. Early recognition and treatment of SAS avoids cardiovascular and neurological complications.1 OSAS has been reported in association with primary open angle glaucoma.1 Geyer et al2 found equal prevalence of glaucoma in OSAS as in the general population. Ophthalmic findings in OSAS are floppy eyelid syndrome,3, 4 keratoconus,5 papilloedema,6 and ischaemic optic neuropathy.7 Optic nerve vascular dysregulation secondary to OSAS-induced arterial hypertension and arteriosclerosis or the imbalance between nitric oxide (a vasodilator) and endothelin (a vasoconstrictor) has been suggested to contribute to optic neuropathy.7, 8 There have been no reports of VF changes in OSAS patients before or after treatment. Improved VF could be due to improved cognitive ability and alertness following CPAP. Patients with OSAS, visual symptoms, and suspicious VF should be tried with CPAP.