Diseases of eye

By ; Dr. Bushra Ahmad

GLUCOMA;

Group of diseases characterized by increase intraocular pressure which causes damage of optic nerve resulting in blindness.

CAUSES;

• drainage of aqueous humor thru trabecula is blocked

• Inc. intraocular pressure

• rises above 60 mmHg

• optic nerve fibers at optic disk are compressed

• initially Dec. visual field

• eventually blindness

Early treatment eyes protected otherwise lost

Infants Infantile Glaucoma

Child hood Juvenile Glaucoma

Types ;

Two types

• Primary opera angle glaucoma ( POAG )

• Primary angle closure glaucoma ( PACG )

POAG ;

• Common 80 %

• No visible obstruction

• Cause not known

• Gradual Inc. pressure

PACG ;

• Visible obstruction of drainage

• Iris is pushed against corners preventing drainage of aq. Humor

• Pressure rises over period of few hours

CAUSES ;

• Diabetes

• Inflammation

• Injury

• Drugs

SYMPTOMS ;

POAG :

• Silent chronic disease without any early symptoms

• Later heaviness around eyeball

• Headache

• Visual field reduction

EARLY SYMPTOMS ;

• Pain in eye brows

• Headache

• Nausea

• Blurred vision

TREATMENT ;

No cure but prevent further damage of optic nerve

• Eye drops or Medicine alone

• Laser Treatment

• Surgery

CATARACT ;

Opacity or cloudiness in natural lens of eye.

• Major cause of blindness worldwide

• Develop in old age after 55 to 60 years

• Lens cloudy light rays can’t pass vision blurred

• Lens in sealed capsule old cells die & accumulate within capsule accumulation of fluid + degeneration of pretension lens fiber

CAUSES ;

• Eye injuries

• Previous eye surgery

• Diabetes

• Drugs

• Sunlight

• Alcoholism

• Large quantity of salt

SYMPTOMS ;

• Glared

• Blurred vision

• Poor night vision

• Diplopia in affected eye

• Fading of colors

TREATMENT ;

• Only surgery

Natural lens replaced with permanent plastic IOL implant

2 Methods

1. Extra capsular extraction cold technique

2. Phacoemulsification

NIGHT BLINDNESS ;

Loss of vision when light in the environment becomes dim.

CAUSES ;

• Deficiency of vit. A

Deficiency of vit. A is due to

• Diet

• Dec. absorption of vit. A from intestine

TREATMENT ;

• Vit. A before visual receptors start degenerating

EFFECTS OF LESION AT DIFFERENT LEVELS OF :

ANOPIA ;

loss of vision in one visual field is known as anopia.

HEMIANOPIA ;

loss of vision in one half of visual field is known as hemianopia.

TYPES OF HEMIANOPIA ;

1. Homonymous hemianopia

2. Heteronymous hemianopia

EFFECT OF LESION OF OPTIC NERVE;

Lesion in one optic nerve will cause total blindness or anopia.

CAUSE ;

• Increased intracranial pressure

EFFECT OF LESION OF OPTIC CHIASMA ;

Pressure on uncrossed lateral fibers by aneurgsmal dilation of carotid artery causes blindness in temporal part of retina of same side.

If lateral fibers of both sides are affected the vision is lost in nasal half of both visual fields causing biursal hemianopia.

Compression of nasal fibers i.e. crossed fibers by pituitary tumor causes bitemporal hemianopia

EFFECT OF LESION OF OPTIC TRACT , LAT. GENICULATE BODY & OPTIC RADIATION;

Lesion of optic tract or lat. Geniculate body or optic radiation causes homonymous hemianopia.

EFFECT OF LESION OF VISUAL CORTEX ;

Lesion of upper or lower part of visual cortex leads to inferior or superior homonymous hemianopia

MACULAR SPARING ;

The phenomena in which the muscular vision is retained (unaffected) in conditions of hemianopia is called macular sparing.

Only the bilateral lesion of visual cortex causes total blindness.

ARGYLL ROBERTSON PUPIL ;

Clinical condition in which the light reflex is lost but the accommodation reflex is present. It is common in tertiary syphilis. It also occur bcz of lesion in Edinger Westphol nucleus , diabetes & alcoholic neuropath.

HORNER SYNDROME ;

It is eye disorder caused by damage to cervical sympathetic nerve. It is also called Bernard Horner Syndrome, Claude Bernard Storner Syndrome or oculosympathetic palsy.

SYMPTOMS ;

• Ptosis

• Swelling of lower eyelid

• Meiosis

• Enophthalamus

• Absence of sweating on affected side of face

PRESBYOPIA ;

In old age the amplitude of accommodation is decreased & the near point is a way from the eye. This condition is called presbyopia.

COLOR BLINDNESS ;

CAUSES ;

• Trauma

• Chronic diseases

• Drugs

• Toxins

• Alcoholism

• Aging

CLASSIFICATION OF COLOR BLINDNESS ;

Based on Young Helmholtz Trichromatic Theory , color blindness is divided into 3 types

Monochromatism Dichromatism Trichromatism

• rod monochromatism protanopia protanomaly

• cone chromatism deuteranopia deuteranomaly

tritanopia tritanomly

FIELD OF VISION ;

Part of external world seen by one eye when it is fixed in one direction is called field of vision or visual field of eye.

Binocular Vision;

Vision in which both eyes are used together.

Monocular Vision;

Vision in which each eye is used separately.

DIVISION OF VISUAL FIELD ;

• Temporal field (extend up to about 100 )

• Nasal field (extends up to 60 )

• Upper field (extends up to 60 )

• Lower field (extends up to 75 )

CORRESPONDING RETINAL POINTS;

These are the areas in retina of both eyes on which the light rays from the object falls. It occurs in Binocular vision.

The two images developed on retina of both eyes are fused into single sensation so we see the objects with single image.

DIPLOPIA ;(Means Double Vision)

While looking at an object if the eyeballs are directed in such a way that the light rays from object do not fall upon the corresponding point on the retina of both eyes a double vision occurs i.e. one single object is seen as two

CAUSES;

• Paralysis

• Myasthenia gravis

• Alcoholic intoxication

• Lesion in 3, 4, & 5 cranial nerves, oculomotor nucleus, red nucleus also result in diplopia.

EXPERIMENTAL DIPLOPIA;

Diplopia can be produced experimentally by following methods ,

1. Applying pressure from outer side of one eye.

2. By holding an object like pen or pencil vertically in front of face at about 5cm from roof of nose.

BLIND SPOT ;

Small area of retina where visual receptors are absent.

VISUAL FIELD & RETINA ;

Light rays from different halves of each visual field do not fall on same halves of the retina. Light rays from temporal part of visual field falls on half of retina of that eye.

MAPPING OF VISUAL FIELD ;

The shape & extent of visual field is mapped out by means of an instrument called Goldman Perimeter & this technique is called perimetery.