Retina and Vitreous

Retina

Retina

The innermost layer of the eyeball.

It is extremely thin and transparent (0.5mm)

It contains visual receptors of the eye

The retinal neurons transmit the picture through the optic nerve fibers to brain for perception

Layer of retina

There are 10 layers in the retina

Retinal pigment epithelium Layer of rods and cones External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve fibre layer Internal limiting membrane

Retinal receptors

* The retinal receptors are divided into two main populations

* Rods* Cones

Rods

Function best in dim light There are 125million rods

in the retina Rods are relatively poor in

visual details

Cones

Function best in daylight There 6 million cones in

the retina Cones enable us to see

small visual details Helps to visualize the

colors

Fovea and ora serrata

The cones form a concentrated area in the retina known as fovea

It lies in the center of the macula lutea The junction of the periphery of the retina and ciliary body

is called ora serrata

Vitreous

The Vitreous humour is a transparent gel that provides a clear optical medium.

It is helps to keep the three layers apposed to each other It occupies approximately 80% of the volume of the globe. The vitreous consist of water, collagen fibrils, molecules of

hyaluronic acid, peripheral cells and mucopolysacharides forming a gel like material.

It nourishes lens, ciliary body and the retina.

Examination of vitreous

Examination of the anterior vitreous can be carried out with slit-lamp.

The vitreous should be observed for cells and any opacities.

Changes in the vitreous with age

Between 40 and 70 years of age in most individuals and earlier in myopes, vitreous liquefaction or syneresis occurs.

The vitreous mass gradually shrinks and collapse, causing its separation from the retina, a condition known as posterior vitreous detachment .(PVD).

Condensation of the vitreous fibrils are present within this liquefied vitreous are visible as floaters.

Retinal Diseases

Diabetic Retinopathy

It is now a major cause of blindness in retina.

Patient who is suffering from diabetic mellitus

Classification– Non proliferative diabetic retinopathy

(NPDR) Micro aneurysms Hemorrhages Hard exudates Retinal odema

– Proliferative diabetic retinopathy (PDR) New vessels at the disc Fibrovascular bands Vitreous detachment Vitreous hemorrhage

Investigations and Treatment

– Urine and Blood Sugar examination– FFA (Fundus flourescein angiography)

Management

Medical Treatment : Good diabetic control

Laser Treatment : Photocoagulation to stop leaking from retinal vessels and bleeding

from new vesselsSurgical Treatment : Vitrectomy is done in case of

vitreous hemorrhage, traction retinal detachment

Hypertensive Retinopathy

Vascular Changes in the retina associated with systemic hypertension

Grade I - Mild generlaised narrowing of arterioles in small branches

Grade II - Marked generalized narrowing associated with focalnarrowing of arterioles

Grade III - Grade II changes and also hemorrhage cotton wool spots and hard exudates

Grade IV - All changes of grade III plus papillodema

Management:

No special management is required for the retinopathy as most of the changes are reversible with adequate control of blood pressure

Retinal detachment

Separation of retina from the retinal pigment epithelial layer

Myopia Retinal Degeneration Trauma

Floaters Flashes of light Sudden painless loss of vision

Scleral buckling procedure

Retinitis pigmentosa

It is a hereditary condition of the retina affecting the rods

Features

– Night blindness– Tubular vision : advanced cases

Fundus changes:– Waxy pallor of disc– Narrowed vessels– Bony spicule pigmentation

Treatment

No permanent cure at present Supportive treatment

– Vitamin A– Low vision aids – Visual rehabilitation– Genetic counselling– Affected individuals discouraged to have kids

Central Serous retinopathy (CSR)

IT id due to detachment of retina in the macular region due to accumulation of fluid resulting in defective vision

Sudden onset of painless loss of vision Central scotoma Micropsia (object appears small) Metamorphopsi (object irregularity)

Mild elevation of macular area Foveal reflex absent

Reassurance Long standing cases : laser

photocoagulation

Retinoblastoma

It is a malignant tumour of the retina occuring in children under 5 years

White reflex over the pupil Squint

Radiation therapy, chemotherapy Photocoagulation Cryotherapy Enucleation/excentration

Vitreous hemorrhage

Bleeding into the vitreous Blood vessels in to retina Causes Trauma to the eye Diseasea of the blood

vessels Diabetic retiopathy Inflammation of the retinal

veins Diseases of retina Retina tears Retinal detachment