Normal Values in Ophthalmology

PARAMETER

VALUES

Diameter of eye ball

Antero posterior

24 mm

Lateral (horizontal)

23.5 mm

Vertical

23 mm

Axial length of eye ball

At birth

18 mm

At 3 yrs age

23 mm

At 14 yrs age

24 mm

Circumference of eye ball

75 mm

Volume of eye ball

6.5 ml

Weight of eye ball

7 gm

Diameter of ant surface of cornea

horizontal

11.75 mm

vertical

11 mm

Diameter of posterior surface of cornea

11.5 mm

Thickness of cornea

In the centre

0.52 mm

In periphery

0.67 mm

Radius of curvature of central cornea

anterior

7.8 mm

posterior

6.5 mm

Refractive index of cornea

1.376

Refractive power of cornea

As a whole

+ 43 D

Anterior surface

+ 48 D

Posterior surface

- 5 D

Corneal endothelial cell density

At birth

6000 /mm²

Young adults

2400-3000 /mm²(parson 2800 /mm²)

decompensation

<500 /mm² ( 75% loss)

Thickness of sclera

Posteriorly -thickest

1 mm

EO muscle insertion

0.3 mm

At equator

0.4 – 0.6 mm

Near limbus

0.8 mm

Width of ciliary body

Ant part- pars plicata

2 mm

Post part- pars plana

5 mm temporally and 3 mm nasally

Central depth of ant. Chamber

3 mm (Parson 2.5 mm)

Volume of aqueous humour in anterior chamber

0.25 ml

Volume of aqueous humour in posterior chamber

0.06 ml

Rate of formation of aq. humour

2.3 ml/min (1% of ant ch. vol.)

Refractive index of aqueous humour

1.336

pH of aq. humour in ant chamber

7.2 (acidic)

Normal range of IOP

10.5- 20.5 mm Hg (15.5+/- 2.57)

Equatorial diameter of lens

At birth

6.5 mm

In 2^nd decade for life

9-10 mm

Thickness of lens

At birth

3.5 mm

At extreme of age

5 mm

Weight of lens

135- 255 mg

Radius of curvature of ant surface of lens

Without accommodation

10 mm

With accommodation

6 mm

Radius of curvature of post surface of lens

6 mm

Refractive index of lens

1.39 (nucleus 1.42, cortex 1.38)

Refractive power of lens

16-17 D

Accommodative power of lens

At birth

14-16 D

At 25 yrs of age

7-8 D

At 50 yrs of age

1-2 D

Near point

At 10 yrs

7 cm

At 30 yrs age

14 cm

At 40, 45 yrs age

25, 33 cm

Weight and volume, refractive index of vitreus

4g, 4cc, 1.3349

Thickness of retina at post pole, equator, ora serrata

0.56 mm, 0.18- 0.2 mm, 0.1 mm

Diameter of

Optic disc

1.5 mm

Macula lutea

5.5 mm / 15^o of visual field

Fovea centralis

1.85 mm / 5^o of visual field

Foveola

0.35 mm (2 DD from disc edge)

Foveal avascular zone

0.8 mm (P)

Thickness of ora serrata nasally and temporally

0.7- 0.8 mm and 2.1 mm

Distance of ora serrata from limbus

6mm nasally, 7 mm temporally

Total number of rods and cones

120 million and 6.5 million

Density of cones, length of cone cells in fovea

1,99,000 /mm², 80 mm

Length of optic nerve

Total

47- 50 mm

Intraocular

1 mm

Intra orbital

30 mm

Intracanalicular

6-9 mm

Intracranial

10 mm

Total number and thickness of fibres of optic nerve

1.2 million, 2-10 mm

Size of optic chiasma

12 mm horizontal, 8 mm AP

Visible portion of EM radiation spectrum

400 (violet)- 750 (red)

Dark adaptation time- cone and rod adaptation

5 min (cone) 30 min (rod)

Light adaptation time

5- 10 min

EO muscle insertion distance from limbus by Fuchs, 1884, length of contact arc at primary gaze, length of muscle and tendon length

Medial rectus

5.5 mm, 6 mm, 40 mm, 3.7 mm

Inferior rectus

6.5 mm, 9 mm, 40 mm, 5.5 mm

Lateral rectus

6.9 mm, 15 mm, 48 mm, 8.8 mm

Superior rectus

7.7 mm, 8.4 mm, 42 mm, 5.8

Superior oblique

16.3 mm, 5 mm, 60 mm, 20 mm

Inferior oblique

18.4 mm, 17 mm, 37 mm, 1-2

Centre of rotation of eye ball in primary position

13.5 mm behind apex of cornea

Angle between muscle plane and visual line

Sup and inf recti

23^o in primary position of gaze

Sup and inf oblique

51^o

Angle between axis of eye ball and orbit

23^o

Number of cell layer of different parts of conjunctival epithelium

Marginal

5

Tarsal

2

Fornix and bulbar

3

Limbal

8-10

Number of glands of Krause in the fornices

40-42 upper and 6-8 lower

Number of glands of Wolfring in the tarsal border

2-5 upper, 2-3 lower

Distance of puncta from inner canthus

Upper- 6 mm, lower- 6.5 mm

Lacrimal canaliculus- diameter

0.5 mm

Length of canaliculus

Vertical part

2 mm

Horizontal part

8 mm

Lacrimal sac- length

Total

15 mm

Fundus

3-5 mm

Body

10-12 mm

Lacrimal sac breath and capacity

5-6 mm, 20 c. mm

Length of NLD

Total

18 mm (12-24 mm)

Intraosseous

12.5 mm

Intra meatal

5.5 mm

Diameter of NLD

3 mm (upper end is narrowest)

Rate of secretion of tear

1.2 ml/ min or 10 cu ml/24 hrs

Refractive index and pH of tear

1.357, 7.4 (7.3-7.7) in sleep

Normal BUT, height of marginal tear strip

> 10 sec, 0.5 mm

Length of palpebral fissure

Horizontal

18-21 mm at birth, 28-30 mm adult

Vertical in the centre

8 mm at birth, 9-11 mm adult

Length of LPS muscle and tendon

40 mm, 15 mm

Size of tarsus- length, thickness

29 mm,1 mm

Height of tarsus

Upper lid

10-11 mm

Lower lid

4-5 mm

Number of meibomian glands

20-30 in each lid, single row

Number of glands of Zeis

2 glands associated with each cilia

Number of glands of Moll (modified sweat)

Between the cilia, LL>UL

Normal rate of blinking

12- 20 times/min

Depth of orbit- along medial and lateral wall

42 mm and 50 mm

1 mm change in axial length gives ametropia of

3 D

1 mm change in radius of curvature of cornea gives ametropia of

6 D

Hypermetropia at birth

2.5 D

Listing’s reduced eye

Total dioptric power

+ 60 D

Principal point

1.5 mm behind ant. surface of cornea

Nodal point

7.2 mm behind ant surface of cornea

Anterior focal point

15.7 mm in front of ant surf of cornea

Posterior focal point

24.4 mm behind ant surf of cornea

Ant & post focal length

17.2 (15.7+1.5) & 22.9 (24.4-1.5)