All Measurements related to AN EYE

All the Dimension of an Eye

Eyeball occupies 1/5^th volume of an orbit.

Orbit	Horizontal	40mm
	Vertical	35mm
	Volume	30ml/cc
	Depth	45-55mm
Optic Canal	Length	8-10mm
Interpupillary Distance		60mm
Optic Nerve	Intraocular	1mm
	Intraorbital	30mm
	Intracanalicular	6-9mm
	Intracranial	10mm
Optic Canal	Length	8-10mm
	Width	5-7mm
Sclera	Thickness (posteriorly)	1mm
	Thickness (at the insertion of EOM)	0.3mm
Lens	Diameter	9-10mm
	Thickness	3.5mm-5mm
	Anterior radius of Curvature	10mm
	Posterior radius of Curvature	6mm
	Capsule (Equator)	14µ
	Capsule (pole)	3µ
Cornea	Horizontal Diameter	11.7mm
	Vertical Diameter	11mm
	Thickness (peripheral)	1-1.2mm
	Thickness (central)	0.5-0.6mm
	Radius of curvature (anterior)	7.8mm
	Radius of curvature (Posterior)	6.5mm
Retina	Foveola	0.35mm
	Fovea	1.5mm
	Parafoveolar	2.5mm
	Perifoveolar	5mm
	Macula lutea	5.5mm
	FAZ (Fovealar avasacular zone)	0.8mm
	Number of Rods	120million
	Number of Cones	6.5million
Eye ball	AP Diameter	24mm
	Horizontal Diameter	23.5mm
	Vertical	23mm
	Circumference	75mm
	Volume	6.5mm
	Weight	7g
Uvea	Pars Plicata	2mm
	Pars plana	4mm
	Cilairy body (diameter)	0.5mm
	Ciliary body (length)	2mm
Anterior Chamber	Depth	2.5mm
	Volume	0.25ml
Posterior Chamber	Depth
	Volume	0.06ml
Vitreous	Volume	4ml
Intraocular pressure		10-21mm of Hg
Aqeous Humor	Rate of production	2µl/min
	Rate of outflow	0.22 µl/min/ mm of Hg
	Diurnal variation in pressure	< 5mm og Hg (>8 glaucomatous)
	Diastolic BP-IOP	>55 mm of Hg
Cup Disc	Ratio	0.3 (<0.2 assymetrical cups)
Lid	Aperture (Vertical Height)	10-20mm (8-12mm in female 7-10mm in male)
	Aperture (Horizontal )	28-30mm
	Lidmargin thickness	2mm
	Lateral canthus	2mm higher than medial canthus
	Upper lid crease	10mm (female) 8mm (male)
Meibomian gland	Number Upperlid	30-40
	Number Lower Lid	20-30
Lacrimal apparatus	Puncta (upper )	6mm temporal to innercanthus
	Puncta (lower)	6.5mm temporal to inner canthus
	Canaliculi Vertical	1-2mm
	Canaliculi Horizontal	6-8mm
	Lacrimal Sac (Length)	12-15mm
	Lacrimal sac (breadth)	5-6mm
	Nasolacrimal Duct	15-18mm
	Height of marginal tear strip	1mm
Refractive Index	Cornea	1.37
	Lens	1.42
	Aqueous + Vitreous humor	1.33
Refractive Power	Cornea	45-47
	Lens	15-13

Collected from Comprehensive ophthalmology 5e AK Khurana

Difference between Preseptal and Orbital Cellulitis

Difference between Preseptal Cellulitis and Orbital cellulitis

		Preseptal Cellulitis	Orbital Cellulitis
Anatomical Location		Anterior to orbital septum	Behind orbital septum
		Only periorbital skin and eyelid involved	Orbit is involved
Causes		Internal Herdeolum Acute Dacrocystitis Lid Trauma Insect Bite	Infected Sinus Spread of infection from teeth, face and lid
Age group			Common in Children
Clincal Features	Proptosis	absent	Axial Type
	Extraocular Movement	Normal	Restricted and painful
	Conjuctival congestion	Absent	Present and Necrotic
	Fever	Present	Present with vomiting and Prostation
	Vision	Normal	May be lost
	Pupillary reaction	Normal	May be lost
Complications		Orbital Cellulitis	Orbital: Subperiosteal and orbital Abscesses
			Ocular Blinding, Optic Neuritis, CRAO, Exposure keratitis
			Temporal, Intracranial or systemic Infection
Management	Medical	Oral Systemic Antibiotics	Ocular emergency Hospital Admission Intensive Broad spectrum antibiotic Therapy
	Surgical		STRONGLY CONTRAINDICATED Needle Aspiration and I and D
		Exploration and debridement	Canthotomy/Cantholysis

Various Types of cellulitis in Eye