What is Vision disease?What Problems causes Vision Disease?
Problems in an Human Eyes is Reffers to as Vision Disease.
The Eye is a Special Organ of the Sense of Sight.The Adult Human Eyeball is a Hollow , Spherical Structure, 24 mm in Diameter and Situated in the Orbital Cavity.Only 1/6 th of the Eyeball is Visible outside.The walls of the Eyeball contain 3 Principal Layers: The Outer Fibrous layer ; The Middle Vascular Layer; and Inner Nervous Layer, the Retina. In addition , It also Contains the Lens, the Aqueous Humour and Vitreous Humour.
The main Functions of the Human Eye is focusing of light waves and stimulation of Photoreceptors of th e Retina.
This Requires 5 basic Processes i.e.
- Transmission of Light waves through transparent media of the Eyeball.
- Refraction or Bending of Light waves/Sunlight through different Refractive media of different Densities.
- Accommodation of the Lens to focus the Light waves.
- Regulation of amount of Light entering the Eye throught pupil by iris diaphragm.
- Convergence of Eyeballs.
List of Eye/Vision Disease with Pictures
1#Strabismus/Squint Vision Disease
Medical term for crossed eyes is Strabismus / Squint.
What is the cause of Strabismus?
Strabismus/Squint is Caused by the Unilateral Paralysis of an Individual muscle .Muscle is paralysed due to invovement of the Nerves produces Strabismus /Squint that is Deviation of Eyes to the opposite side and may results in Diplopia or Double vision.
In Diplopia , the light from an object is not focused on the Identical Areas of both Retinae.The Real Image falls on the Macula ( See above Figure – Eye Diagram & It’s Finctions) of the Unaffected Eye and False image on the peripheral part of the Retina of the Paralyzed eye.
|Muscle Paralyzed||Nerve Involved||Effects|
|Lateral Rectus Muscle||Abducent||Medial Squint|
|Medial Rectus Muscle||Oculomotor||Lateral Squint|
2#Ptosis Vision Disease
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What is the cause of Ptosis?
Ptosis( Drooping Eyelids) is Caused by the Paralysis of Levator Palpebrae Superiosis muscle due to involvement of the Occulomotor Nerve leads to Complete Ptosis( Drooping of Upper Eyelid.
The Lesion of Cervical Sympathetic Chain leads to Partial ptosis (partial Drooping of upper eyelid) as it affects only Smooth muscle part of LPS.
The periphery of the Cornea Frequently displays a Whitish Ring in older persons, owing to Fatty Degeneration . This Whitis Ring is Termed Arcus Senilis.
The Centre part of the Cornea receives Oxygen From the outside air. Therefore , the Soft Plastic Contact lenses worn for long periods must be permeable to the air so that Oxygen can reach the Cornea.
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The injury to Cornea may cause Opacity that may interfere with vision.The most common injuries of the Eye are the cuts or tears of the Cornea caused by Foreign bodies.
The Normal lack of Vascularity and of Lymph vessels Accounts for Great Success or Corneal Grafts.The Cornea is Successfully Grafted from one Person to the Other.
The Corneal Reflex is Elicited Clinically by Gentle Touching of the Cornea with wisp of Cotton wool. As the Cornea is Touched both the eyes are Closed.
Pathway:Opthalmic Nerve(Afferent Limb) ➡ Main Sensory Nucleus of Trigeminal Nerve ➡ Reticular Formation ➡ Both the Facial Nerve(Efferent Limbs)
In Retinal Detachment there is Separation of two layers of Retina that is Pigment and Neural Layers.
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If the drainage of Aqueous Humour is Blocked, There occurs an Abnormal increase in the Intraocular Pressure a condition Called Glaucoma.As a Result, there is Severe Pain in the eye due to pressure on the highly sensitive Cornea.
The Glaucoma may Cause variety of Visual Problems,viz. Blindness due to Compression of Retina and its Blood Supply.
The intraocular pressure which normally is about 15mmHg can be measured on Anesthetized Cornea (tonometry).
The lens plays an Important role in Accommodation .The lens Absorbs much of the Ultraviolet light and becomes increasingly Yellowish with age .It also Becomes Harder with age .As a Result of which the power of Accommodation is Lessened in Old Age producing a Clinical Condition Called Presbyopia.
The Opacity of the Lens is Termed Cataract. with Increasing age and in Certain Diseases states, the lens Becomes Opaque . The increasing Opacity leads to Inceasing visual impairment. This can be Treated Surgically by Excision of Opaque lens and Replacement with an Artificial Lens.
11#Night Blindness or Nyctalopia
Night Blindness means Blindness in Dim Light . This condition is characterized by decreased sensitivity ( that is increased Visual threshold) of the eye to light due to Vitamin A Deficiency.
Vitamin A is Required for the Synthesis of Retinene, Vitamin A produces Viisual Abnormalities; the earliest to appear is Night Blindness .
Insensitive to Colours that is Inability on the part of an Individual to Recognise the Colours is Called Colour Blindness.
- In Males: Red- Green Defect occurs in about 2-2.5% of the Population.
- In Females: The Defect is Present in only 0.4% of the Population.
When a Subject’s Gaze is Fixed at a Stationary Objects, the Eyeballs are not Still (Without Motion) , There are Continuous Jerky Movements. This is called Physiological Nystagmus.