Table 2 Findings from the different studies

Zahn 1981 [41]

CR

A 25-year-old woman who attempted suicide by ingesting quinine vs. a normal control

Quinine (3.8–4.8 g)

Unspecified ERG type

ERG findings recorded on days 1, 2, 3, 6, 9, 10, 12, and at six months

- Day 1: amplitude of the a-wave was greater than that of the control, while the amplitude of the b-wave was less than the control. The implicit time for both the a and b waves was increased. The b-a amplitude ratio decreased with time but was normal only on days 3 to 6.

- Days 3 and 6: a-wave amplitude was normal while b-waves were enlarged (more for the left than the right eye).

- 6 months: b-wave amplitude decreased substantially by this date.

- The a-wave implicit time reached normal by day 2, while the b-wave implicit time increased up to day 12.

- OPs, compared to controls, was completely extinguished on day 9, improved on days 10 and 12 (though still decreased compared to the control) and remained diminished by six months.

- Had a limitation: difficult to accurately identify b-wave peaks

- Depressed ERG was due to damaged bipolar or photoreceptor cells through secondary retinal ischemia

Mindel et al. 1981 [35]

CR

A 20-year-old woman attempted who died by suicide following ingesting of Vacor (a rat poison).

Vacor and Ergotamine (used to treat Vacor-induced orthostatic hypotension)

Unspecified ERG type

ERG performed 5 and 10 weeks after discontinuing ergotamine

- ERG waves were extinguished in both eyes

- The findings were inconclusive on the true cause of extinguished ERG waves, whether from Vacor, Ergotamine, or a combination of the two toxicities

Verdon 2008 [42]

CR

43-year-old woman evaluated nine months after attempting suicide by ingesting quinine

Quinine

Multifocal ERG (mERG)

Full-field (Ganzfeld) ERG (ffERG)

ERG’s performed 9 months after the suicide attempt.

- Subnormal Rod’s responses to dim flash stimuli.

- At both the scotopic and photopic SF - The a-wave amplitude exceeded the b-wave amplitude as the b-wave had selective reductions in both conditions (electronegative waveforms).

- For the scotopic SF – normal a-wave amplitudes, but reduced b-wave amplitudes.

- For the scotopic SF – normal a-wave implicit times and faster than normal b-wave implicit times

- Phototopic SF- abnormal b-wave with a delayed implicit time.

- Scoptopic OPs - abnormal with a single positive peak (corresponding in time to the positive peak in original waveform)

-

Treichel et al. 2004 [40]

CR

A 44-year-old woman attempted suicide in her car by ingesting methanol

An age- and sex-matched control

Methanol

Unspecified ERG type

ERG measurements were performed 8, 18, and 26 h after admission, where patient was missing for 48 h prior to admission.

ERG performed while individual was comatose.

- Postadmission intervals, all ERGs were similar. With a significant diminution of the b-wave, but the a-wave remained stable (apparently normal amplitudes and implicit times).

- Findings were similar to animal models following methanol ingestion

Brinton et al. 1980 [39]

CR

A 25-year-old woman who attempted suicide by ingesting quinine Vs. an age- and sex- matched control

Quinine (3.7–4.7 g)

Flashlight functional ERG

Light perception was lost 14.5 h after ingestion; first ERG was completed 18 h later. Other ERG tests performed day 2, day 12, and 6 months

ERG obtained after 15 min of dark adaptation

- Slowing a-wave that returned to normal after two days.

- a-wave depth increased and returned to normal after several days.

- Loss of OPs with no tendency for recovery

- b-wave decreased in size and returned toward normal after a first few days, but a late progressively decreased in size

- Quinine has direct toxicity to retinal cells. It is known to affect ganglion cells, pigment epithelium, and other retina layers.

- The delayed a-wave (prolonged implicit time) when there was no light perception. Indicates evidence of an acute effect on photoreceptors cell layers.

- The later decline in b-wave shows inner layer damage. This may be through vascular constriction or ischemia due to quinine.

Canning and Hague 1988 [44]

CR

28-year-old woman attempted suicide by ingesting quinine, presented 12 h after ingestion

Quinine (9 g)

Flash ERG (fERG)

Pattern ERG (PERG)

First ERG was completed on day 1, then repeated several times over the course of 66 days

- Day 1: Normal amplitude to blue, red, and white stimuli, but reduced OPs. The pattern ERG was reduced

- Over time, the amplitude reduced, but abnormal flicker response and pattern ERG persisted.

- Quinine must affect the initial electrically silent part of the retina that don’t contribute to the fERG waveforms e.g., the ganglion cells. This is due to having a normal early ERG in the presence of severe visual dysfunction.

- The inner retina was mainly affected because the abnormal pattern ERG and reduced OPs during the same period in the patient.

- “The pattern ERG was markedly reduced, and no pattern visual evoked response (VER) could be recorded.”

Simmons and Good 1998 [33]

CS

Two out of three patients presenting with CO poisoning attempted suicide.

Case 1: a 43-year-old woman who attempted suicide and presented to hospital after three weeks

Case 2: 59-year-old man who attempted suicide and presented ten years following a suicide attempt.

None

Flash ERGs (fERG)

Pattern ERGs (PERG).

- Case 1: ERGs were normal from both eyes, the N95 component increased within the normal range. The P50 / N95 ratios were normal.

- Case 2: The P50/ N95 ratio was significantly elevated and the fERGs were normal in both eyes.

- Normal fERG findings.

Traill et al. 2007 [36]

CR

A 29-year-old woman attempted suicide by ingesting quinine

Quinine (6 g)

fERG

ERG completed 13 years after the suicide attempt.

- Flat photopic response and a scotopic response with an absent b-wave

Meshi et al. 2015 [38]

CR

A 59-year-old woman with a diagnosis of borderline personality disorder, benzodiazepine and alcohol use disorder attempted suicide by ingesting quinine and alcohol and arrived at the hospital three days after attempting suicide.

Quinine (12 g), benzodiazepine, alcohol.

High dose beta-carotene was given 10 days post ingestion (and taken daily for 3 months), after the first ERG (day 6) but before ERGS completed on day 6, 39, and 142.

Full-field ERG (ffERG)

ERG were obtained 6-, 39, and 142-days post-ingestion.

- The amplitude and pattern for the scotopic and photopic responses in both eyes were diminished.

- A significant reduction in both a-wave and b-wave indicating a primary insult to the photoreceptors.

- During treatment, the ERG responses showed mild improvement in the a-wave amplitude in both eyes in the maximal scotopic conditions. Following treatment discontinuation, the a-wave of both eyes decreased.

- The b-waves had no similar pattern and continued to deteriorate during follow-up.

- Only the left eye single flash photopic responses demonstrated some improvement during treatment but decreased after treatment ceased.

- ERG showed transient increase in a-wave amplitude. A-wave decreased after treatment.

o This improvement may be attributed to a positive effect of 9-cis beta-carotene treatment on the photoreceptors and the retinoid cycle

- A limited, slow recovery of the ERG responses after they were almost completely absent over a 2-year follow-up. Thus, a short-term increase in the a-wave amplitudes may be the direct effect of treatment.

- These changes may represent the natural course of ERG responses in quinine toxicity.

- The lack of consistent increase in ERG b-wave responses during treatment

o This may be because 9-cis beta-carotene impacts photoreceptors, which are not responsible for b-waves

Kohli 2021 [45]

CR

A 45-year-old man who attempted suicide by hanging and presented to the hospital after six months

Ganzfield ERG

Patient was initially dark-adapted (DA) for 30 min and then Light Adapted (LA) ERGs were performed

ERG completed six months after suicide attempt

- Recording of the right eye done at DA 0.01 cd s m-2 showed a reduced amplitude a-wave; reduced b/a wave amplitude ratio at DA 3.0 and DA 10.0 cd s m-2.

- The OPs on the DA 3.0 wave showed reduced amplitudes.

- Light-adapted ERG also showed a reduced b/a wave amplitude ratio along with a reduced amplitude 30-Hz flicker.

- The dysfunction was post-phototransduction (at the level of the inner bipolar cells of the retina) due to having an electronegative ERG in the presence of a normal electrooculography (EOG).

- Reduced OP waves suggest amacrine cells dysfunction

- The cause of the inner retina cell dysfunction could be due to hypoperfusion.

Chen 2022 [34]

CR

A female, aged 19-year with a history of depression had a suicide attempt byg ingesting lorazepam and magnesium valproate

Lorazepam (19 mg) and Magnesium valproate (VPA) (60 g)

Multifocal ERG (mfERG)

- Based on the mfERG, P1 amplitude in the right was lower than in the left eye (more damage to right eye)

- Findings were inconclusive with ERG, and mingling was thought

- Unable to ascertain which drug (lorazepam, VPA, or a combination of the two) led to these ERG findings

Miura 2022 [43]

CR

A 23-year-old man presented 3 months after attempting suicide by ingesting sildenafil

Sildenafil (2 g)

Full field photopic ERG (ffERG)

Multifocal ERG (mfERG)

ERGS obtained 3 and 6 months after overdose

DA 0.01, DA 3.0, LA 3.0, and LA 30 Hz flicker were performed

A slightly reduced amplitudes of full-field photopic ERGs; But normal amplitudes of the scotopic, maximum combined, and flicker ERGs.

- Reduced multifocal ERGs (mfERGs), especially in the bilateral paracentral areas.

- Complete normalization of ERG did not occur six months following treatment

- PDE5 inhibition in bipolar and ganglion cells and PDE6 inhibition at the photoreceptors may be associated with Sildenafil-induced visual impairment.

Bacon et al. 1988 [37]

CR

A 47-year-old man who presented 24 h after attempting suicide using quinine sulfate and flurazepam.

Quinine sulfate (10 g) and Flurazepam (600 mg)

Unspecified ERG type

Dark-adapted ERG was done 4 and 10 weeks after the overdose.

- Week 4: The left eye dark-adapted ERG was subnormal with the absence of the b wave. This suggested a proportionately greater loss of postsynaptic electrical activity than photoreceptor activity.

- Week 10: b-wave amplitude had a small improvement.

- Within three days, the ERG approached normal values, but by the ninth day, the b wave had started to decrease and, six months later, remained essentially unchanged. Similar findings have been found in rabbit experiments.

Fountoulakis et al. 2004 [7]

Cx

A total of 52 patients (15 males, 35 females, mean age of 41.0 ± 11.4) with major depressive disorder (MDD)were enrolled in the study. The participants were divided into three groups, (1) No thoughts of death (n = 17), (2) nonspecific thoughts of death (n -= 23), and (3) suicidal ideations (n = 10)

Among these, five participants had attempted suicide

Individuals free from medication for at least two weeks before initial assessment

All 5 suicide attempts were performed by swallowing pills, drugs, or poison, but the type and quantity are unknown.

Flash ERG (fERG)

- No significant difference between the groups.

- a-wave latency was lowest among individuals with suicidal ideation.

- b-wave latency was highest among individuals with suicidal ideations