''Cyanopsia'' is a

medical Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...

term for seeing everything tinted with

blue Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when obs ...

. It is also referred to as ''blue vision''. Cyanopsia often occurs for a few days, weeks, or months after removal of a

cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...

from the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

. Cyanopsia also sometimes occurs as a

side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...

of taking

sildenafil Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is unclear if it is effective for treating sexual dysfunction in women. It is taken by ...

tadalafil Tadalafil, sold under the brand name Cialis among others, is a medication used to treat erectile dysfunction (ED), benign prostatic hyperplasia (BPH), and pulmonary arterial hypertension. It is taken by mouth. Onset is typically within half a ...

, or

vardenafil Vardenafil is a PDE5 inhibitor used for treating erectile dysfunction that is sold under the brand name Levitra among others. Medical use Vardenafil's indications and contraindications are the same as with other PDE5 inhibitors; it is closel ...

."Viagra and Vision". (n.d.). Author. Retrieved January 31, 2008
/ref> Cyanopsia is a medical

symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...

and not a

sign A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm, or me ...

. It is a purely subjective state and can be caused by a physical or functional abnormality of the eye, a physical or functional abnormality of the brain, or be purely psychological. Cyanopsia, if unaccompanied by any other sign or symptom, is not an indication of any disease or disorder. Unless it causes an impairment or significant distress, it is not in and of itself diagnostically relevant.

Cyanopsia after cataract removal

The eye's

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

is normally tinted

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the R ...

. This reduces the intensity of blue

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

reaching the

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

. When the lens is removed because of

, it is usually replaced by an artificial

intraocular lens Intraocular lens (IOL) is a lens implanted in the eye as part of a treatment for cataracts or myopia. If the natural lens is left in the eye, the IOL is known as phakic, otherwise it is a pseudophakic, or false lens. Such a lens is typically i ...

; these artificial lenses are clear, allowing more intense blue light than usual to fall on the retina, leading to the phenomenon. Hayashi and Hayashi (2006) compared visual function in people given yellow-tinted intraocular lenses with that in people given non-tinted intraocular lenses. Those with the yellow-tinted lenses were less likely to report cyanopsia than those with the clear lenses. Hayashi and Hayashi found no differences in

visual acuity Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal ...

or in

contrast sensitivity Contrast is the contradiction in luminance or colour that makes an object (or its representation in an image or display) distinguishable. In visual perception of the real world, contrast is determined by the difference in the colour and brightn ...

between the two groups. They also found that no one reported cyanopsia three months after the cataract operation, suggesting that some form of

neural adaptation Neural adaptation or sensory adaptation is a gradual decrease over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus. For example, if a hand is rested on a table, the tabl ...

colour constancy Color constancy is an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. A green apple ...

had taken place.Hayashi, K., & Hayashi, H. (2006). Visual function in patients with yellow tinted intraocular lenses compared with vision in patients with non-tinted intraocular lenses. British Journal of Ophthalmology, 90, 1019-1023.

Cyanopsia from sildenafil

The author of ''Viagra and vision'' attributes cyanopsia after taking sildenafil to diminished enzyme activity, thereby sensitizing the retinal

rod cells Rod cells are photoreceptor cells in the retina of the eye that can function in lower light better than the other type of visual photoreceptor, cone cells. Rods are usually found concentrated at the outer edges of the retina and are used in per ...

. Rod cells are most sensitive to light of wavelengths near 498 nm; such light appears blue-green. When light levels are low enough for both rods and

cone cell Cone cells, or cones, are photoreceptor cells in the retinas of vertebrate eyes including the human eye. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cone ...

s to be active (

mesopic vision Mesopic vision, sometimes also called twilight vision, is a combination of photopic and scotopic vision under low-light (but not necessarily dark) conditions. Mesopic levels range approximately from 0.01 to 3.0 cd/m2 in luminance. Most nigh ...

) the enhanced rod activity induces the bluish visual tint.

References

{{reflist

External links

* https://web.archive.org/web/20070524033238/http://www.psych.ucalgary.ca/PACE/VA-LAB/Brian/acquired.htm for illustrations of various colour deficiencies including cyanopsia. Color vision

Cyanopsia after cataract removal

Cyanopsia from sildenafil

See also

References

External links