ACHOO Syndrome

Autosomal Dominant Compelling Helioopthalmic Outburst Syndrome is characterized by uncontrollable sneezing in response to the sudden exposure to bright light, typically intense sunlight.

This type of sneezing is also known as photic sneezing, also known as photoptarmosisa condition of uncontrollable sneezing in response to numerous stimuli. About one in four individuals who already have a prickling sensation in their nose will sneeze in response to sunlight, but pure photic sneezing is far less common.

Sneezing is usually triggered by contact with infectious agents or after inhaling irritants, but the cause of photic sneezing is not fully understood. It may involve an over-excitability of the visual cortex in response to light, leading to a stronger activation of the secondary somatosensory areas.

“I like to write when I feel spiteful. It is like having a good sneeze.”
– D. H. Lawrence

Sneezing usually feels good because, much like an orgasm, sneezes are reflexes involving tension and release. Also, like climaxes, they sometimes feel like they are about to happen, but do not; and like the final throes of sex, they can erupt as loud crescendos or pop off like a string of firecrackers.

Some evidence suggests that sneezing, like orgasms, also releases endorphins. Unlike orgasms though, sneezes can travel at about 100 miles per hour.

Ross: I was in the shower, and I felt something.
Chandler: Was it like a sneeze, only better?
Friends (1996) Season 3, Ep. 23; “The One with Ross’s Thing” [No. 71]

Curiously, in English, it is common to say “Bless you”; in German, “Gesundheit”; in Hindu, one person says “Live” and the other responds “With you”; and in Zulu people say “I am now blessed”. The ancient Greeks and Romans said “Banish the Omen”.

Depth Perception

The human eye uses three methods to perceive and determine distance:

“The more I see, the less I know for sure.”
– John Lennon

The size a known object has on your retina – if you have knowledge of the size of an object from previous experience, then your brain can gauge the distance based on the size of the object on the retina.

“There are things known and there are things unknown, and in between are the doors of perception.”
– Aldous Huxley

Moving parallax – when you move your head from side to side, objects that are close to you move rapidly across your retina. However, objects that are far away move very little. In this way, your brain can tell roughly how far something is from you.

“All things are subject to interpretation. Whichever interpretation prevails at a given time is a function of power and not truth.”
– Friedrich Nietzsche

Stereo vision – each eye receives a different image of an object on its retina because each eye is about 2 inches apart. This is especially true when an object is close to your eyes. This is less useful when objects are far away because the images on the retina become more identical the farther they are from your eyes.

“What you see and what you hear depends a great deal on where you are standing. It also depends on what sort of person you are.”
– C.S. Lewis, ‘The Magician’s Nephew’


Synesthesia is a perceptual condition of mixed sensations.

A person who suffers from synesthesia can experience a stimulus in one sensory modality which in turn elicits an involuntarily sensation or experience in another modality. For instance, the hearing of a sound can elicit the sensation of a patient’s vision being coloured in a certain way.

Likewise, the perception of a shape or form may induce an unusual perception in the same modality. A letter in black font may, for instance, become coloured in a certain way, whereas another letter in the same black font may not. This kind of synesthesia is usually called grapheme-colour synesthesia.

Increased cross-talk between regions in the brain which are specialized for different functions may account for the many types of synesthesia. For example, the additive experience of seeing colour when looking at graphemes might be due to cross-activation in and around the grapheme-recognition area of the brain. An alternate possibility is disinhibited feedback, or a reduction in the amount of inhibition along normally existing feedback pathways in the brain.

Whatever the main cause of this neurological phenomenon may be, research has shown the occurrence of synesthesia has nothing to do with the use of stimulants like alcohol or caffeine.

Well known synesthetes include: Leonard Bernstein, David Hockney, Billy Joel, Marilyn Monroe, Vladimir Nabokov, Itzhak Perlman, Nikolai Rimsky-Korsakov, Jean Sibelius, Eddie Van Halen, and Stevie Wonder.

Heterochromia Iridis

In anatomy, heterochromia refers to a difference in colouration, usually of the iris but also of hair or skin.

Heterochromia eyes blue on the outside with or...

An eye with partial heterochromia

Heterochromia is a result of the relative excess or lack of melanin; a pigment. It may be inherited, or caused by genetic mosaicism –  the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg – other disease, or injury.

Heterochromia iridis is a heterochromia of the eye. There are two main kinds:

  • Complete heterochromia, one iris is a different colour from the other.
  • Partial heterochromia, part of one iris is a different colour from its remainder.

Eye colour, specifically the colour of the irises, is determined primarily by the concentration and distribution of melanin. The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic).

English: Heterochromia: Female cat with eyes o...

A cat with complete heterochromia

In humans, usually, an excess of melanin indicates hyperplasia (an increase in number of cells/proliferation of cells) of the iris tissues, whereas a lack of melanin indicates hypoplasia (a decrease in number of cells/proliferation of cells).

Although infrequently seen in humans, complete heterochromia is more frequently observed in other species, where it almost always involves one blue eye. The blue eye occurs within a white spot, where melanin is absent from the skin and hair.

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