Table 4.

Observational studies and case reports evaluating clinical presentation.

Authors	Study	Number of Patients	Substances	Symptoms Description	Onset Perceptual Disorders	Recurrence of Perceptual Disorders	Treatment
Lev-Ran, 2017 [53]	Observational cross-sectional study	40 (27 males); HPPD (DSM-IV-TR)	Previous use of LSD; Lifetime use of Cannabis	HPPD I: mean age 25.5 (3.7), times of LSD consumption: 7.1 (4.3), use of alcohol; perceptual disorders triggered by sexual intercourse, dark environment, and looking at still or moving objects			None of the subjects included in the study received medications particularly targeted at treating HPPD
				HPPD II: mean age 22.1 (2.8), times of LSD consumption 24.6 (1.4), use of SCS, stimulants and inhalants; intentionally triggering perceptual disturbances
Zobor, 2015 [29]	Observational, cross-sectional, control study	Male, 23-year-old	Cannabis, previous 4-year history of heavy consumption (16–20 years)	Visual distortion: visual snow, sperm-like whizzing dot, jittering lights, floaters, photophobia, visual discomfort, positive and negative afterimages, impaired night vision, halos, starburst around lights;	During cannabis use period	Persistence despite cannabis withdrawal	No
				Ophthalmological examination: reduction of phosphene threshold, alteration in the EOG
		4 healthy subjects, mean age 25.5 years	Cannabis: Heavy consumption	Not reported		Not reported	No
Lerner, 2014 [19]	Case report	Male, 24-year-old	Cannabis: Three-year past history of social consumption;	Visual disturbances (halos, color intensification, flashes of colors, distorted perception of distance)	During LSD intoxication	Recurrence one week after completely stopping all substance use: daily visual distortion	Not accepted by the patients
			MDMA, LSD and cocaine (sporadically);
			Social Alcohol drinking			Disappearance after one year
		Female, 25-year-old	Cannabis: Three-year past history of social consumption;	Visual disturbances (positive afterimages, color intensification, flashes of colors, trailing phenomena)	During LSD intoxication	Recurrence four days after completely stopping all substance use: daily visual distortion	Not accepted by the patients
			MDMA, LSD (sporadically);			Improvement after one year;
			Social Alcohol drinking			Trailing phenomena continued to appear intermittently
Gaillard, 2003 [46]	Case reports	Female, 18-year-old	Cannabis: Three-year past history of regular consumption	White dots when looking at a white wall or blue sky, “seeing shadows” on the left side, palinopsia, visual vibration upon awakening	During comatose episode following excessive use of cannabis	Recurrence after stopping all substance use: daily visual distortion
		Male, 25-year-old	Cannabis: Two-year past history of regular and heavy consumption	Visual illusion and dyskinetopsia, difficult in depth perception	After two years of consumption	Symptoms persistence and increase after cannabis withdrawal + memory loss, and concentration deficits
Abraham, 2001 [35]	Observational	38 HPPD cases	LSD: first mean use 18.1 (6.0) years; lifetime use 16 times (median)	7.11 (2.2) different types of visual hallucinations per subject	21 months after first use	Duration of visual hallucinations: 9.67 (7.68) years
					13.5% subjects experienced symptoms within the first month of use, three subjects after a single use
				The majority of subjects reported an intensification of visual hallucinations on emerging into a dark environment
Litjens, 2014 [26]	Case series	31 HPPD cases; Web-questionnaire	MDMA	At least 2 different visual phenomena (visual snow, afterimages, flashes, illusory movement, and increased observation of floaters) with a minimum of one episode of disturbed perception every week (100%);	After a single drug exposure
			Cannabis
			LSD	Anxiety or panic in the weeks before or following the use of drugs (71%)
				Depersonalization (32%)
		assessment	80% serotonergic drugs	Derealization (39%)	After a period of extensive drug use
Lerner, 2015 [55]	Case report	Male, 26-year-old	Cannabis: a Five-year history of occasional consumption;	No distressing macropsia, micropsia, pelopsia and teleopsia, looking at still or moving objects and humans;	LSD intoxication	Recurrence two days after completely stopping all substance use: daily visual distortion	Not accepted by the patients
			Alcohol: Social Consumption;
			LSD: Recreational use	Longer and distressing visual distortion experience with anxiety
						Disappearance after one year
Baggott, 2011 [56]	Observational Web-based questionnaire	2679 subjects	Median of 5 different drugs used by a single subject	224 subjects reported having at least one diagnosis associated with unusual visual experiences;	After exposure to LSD	The probability of experiencing constant or near-constant symptoms was predicted by greater past exposure to drugs and exposure to LSD	104 individuals considered symptoms impairing enough to seek treatment
		89.5% male, aged 21.6 (3.7) years		1487 individuals reported at least one abnormal visual experience;
				587 endorsed at least one experience on a constant or near-constant basis