Onodi cells are the posterior most cells of the ethmoid sinus
It is located superolateral to the sphenoid sinus and is in close relation to the optic nerve
It may sometimes surround the optic nerve

Clinical importance:

Attempt to remove the onodi cells during sinus surgery may cause injury to the optic nerve
The onodi cells are a potential cause for incomplete sphenoidectomy

The anatomical landmarks of the sphenoid sinus correlate with that of onodi cells
Hence, the surgeon may mistakenly believe that the sphenoid sinus has been reached

Reference:
Otorhinolaryngology, Head and Neck Surgery By Matti Anniko, Manuel …

VDTS stands for:

Visual Display Terminal Syndrome

Anterior uveitis

Defective vision is one of the important symptoms of acute iridocyclitis
Initially there is slight blurring of vision with progressive deterioration
There are multiple causes of defective vision in acute iridocyclitis
They are: (from anterior to posterior of eyeball)

corneal oedema and keratic precipitates
Aqueous humour turbidity
Exudates in pupillary area
Myopia as a result of ciliary spasm
Complicated cataract
Cyclitic membrane
Vitreous haze
Macular oedema
Papillitis
Secondary glaucoma

Image credits: The eyes have it

Aphakia literally means absence of crystalline lens
From an ophthalmological point of view, aphakia is the absence of the lens in the pupillary area

Causes of aphakia

Congenital aphakia
Surgical aphakia – removal of lens as in cataract extraction
Aphakia due to absorption of lens – sometimes seen in children after trauma
Traumatic extrusion of lens
Posterior dislocation of lens into the vitreous causes optical aphakia

Optics in aphakia

The lens is important in refraction and hence its removal results in considerable decreased in the refractory power of the eye
The eye becomes highly hypermetropic
The power of eye decreases from …

Telecanthus literally means that the corners of the eyes (canthi) are far away (tele) from each other
It is a condition in which the intercanthal distance is greater than the width of the eye

Normal range of intercanthal distance is 30-35mm

In this, the interpupillary distance remains normal
Telecanthus should be differentiated from hypertelorism (here the interpupillary distance is increased)

Bicanthal plane is the transverse plane joining the 2 canthi
It marks the upper boundary of the mid face

Epicanthus inversus is a fold of skin which passes from the medial part of lower lid –  vertically upwards – covering the medial canthus
It is seen in association with congenital ptosis, blepharophimosis and telecanthus in blepharophimosis syndrome

Intercanthal distance is the distance between the medial canthi of the eye
It’s usually ranges from 30-35mm
For practical purposes, the intercanthal distance is considered to be approximately equal to the width of one eye
In certain conditions, the intercanthal distance increases – telecanthus
Intercanthal distance should not be confused with Interpupillary distance

Canthus is the area where the upper and lower eyelids meet
There are 2 canthi – medial and lateral

Alternate names (synonyms):

Palpebral commissures

BPES stands for:

Blepharophimosis Ptosis Epicanthus Inversus Syndrome (Ophthalmology)