Table 3.

Categorising the published evidence in support of autoregulatory impairment in association with crowded optic discs contributing to the aetiology of transient visual loss in our cohort of young females

	Principal findings
Dysfunctional optic nerve head autoregulation in healthy human subjects
	A significant variation in optic nerve head autoregulatory efficiency is demonstrated between normal subjects13
	A subgroup of young healthy individuals demonstrate abnormal optic nerve head autoregulation15
	Fluctuations in OPP, which should be within the normal autoregulatory plateau, can lead to significant dips in optic nerve head blood flow in healthy subjects with dysfunctional optic nerve head autoregulation22
Dysfunctional autoregulation in young healthy females
	Young females demonstrate a greater latency within the cerebral dynamic autoregulatory response compared with males23
Importance of dynamic autoregulatory dysfunction for the symptomatology of our cohort
	The dynamic phase of autoregulation is more closely associated with neuronal activity than static autoregulation and provides a more sensitive assessment of autoregulatory dysfunction within the optic nerve head24,25
	Pre-existing dynamic autoregulatory dysfunction could predispose patients to ischaemic events26
	Orthostatic hypotensive symptomatology reported to be more common in females although, in a separate study, episodes of orthostatic hypotension were equally common in male and female subjects. Possibility of dysfunctional dynamic autoregulation increasing the probability of manifesting symptoms of orthostatic hypotension, including TVL23,27
Role of autoregulatory dysfunction in the aetiology of NA-AION, a condition associated with crowded optic discs
	Article reviews histological studies suggesting no robust evidence to support either an embolic or thrombotic aetiology for NA-AION28
	32% of NA-AION cohort without hypertension, diabetes mellitus, cardiovascular disease, previous cerebrovascular accident, or migraine29
	In patients with NA-AION and associated medical conditions, one of the commonest conditions is diabetes mellitus, which is associated with vasculopathic risk but is also known to impair autoregulatory function25,30
	Hayreh at al. proposed an aetiology for NA-AION based on an upshift of the autoregulatory plateau in hypertensives31,32
Association between young females and NA-AION
	In subgroup analysis of NA-AION patients under the age of 40, females were affected more frequently than males30
Previously reported associations between anomalous optic discs and monocular TVL
	Retrospective case series of 4 patients with anomalous optic discs reporting monocular TVL precipitated by a change in posture (2 unilateral non-papilloedematous optic disc swelling, 1 optic disc drusen and a 42-year-old female with a unilateral anomalous optic disc). A combined mechanism was proposed with reduced local optic nerve head perfusion combined with systemic hypotensive episodes to explain the relationship between TVL and a change in posture21
	Retrospective case series of 29 patients (mean age 45.5 years, 17% hypertensive, 14% hyperlipidaemic, 10% diabetic) who presented with monocular TVL on waking. 90% were female and 48% had crowded optic discs. One patient had a unilateral crowded optic disc and experienced TVL only in the eye with the crowded optic disc. The authors hypothesised autoregulatory failure within the optic nerve head leading to a failure of function at low light levels2

NA-AION = non-arteritic anterior ischaemic optic neuropathy; OPP = ocular perfusion pressure; TVL = transient visual loss