Chapter IV-Eye Pathology
A thorough physical examination of the eye includes detailed examination of the eyeball, eyelids, eyelashes, ocular movements, and visual fields, and inspection of the fundus and retina of the eye. The firmness or the intraocular tension is measured by palpation of the eyeballs through closed lids. The lids are inspected for evidence of any deformity, masses, swelling, or discoloration and for disorders of lacrimal apparatus. After this cursory exam, a more detailed examination ensues. The physician can diagnose any abnormalities of lens, iris, cornea, power of accommodation, shape of pupils, opacities of lens, and lesions of cornea with a hand lens.
The sclera is examined for signs of systemic infections and diseases as in jaundice. Extraocular movements of the eyes are checked by holding an object in front of subject and asking the patient to follow its movement with his gaze. An eye examination also includes examining the fundus of the eye. An instrument called funduscope is used by the examiner to look through the pupil. Funduscope has a light source and a set of magnifying lenses. The examiner can clearly inspect the retina, optic disc, retinal artery, retinal vein with the help of ophthalmoscope and can detect any damage to these parts. For clear and proper examination, pupils are priorly dilated by ophthalmic drops to have clear retinal vision.
Pathological Conditions of the Eyes
A cataract is a progressive eye disorder in which the lens becomes cloudy or opaque due to intrinsic physical or chemical changes. The vision of the person suffering from cataract deteriorates, as the clouding of the lens does not allow the passage of the light to the back of the eyeball. Other than the rare cases of the babies being born with congenital cataracts. Cataracts can very well be a normal part of the aging process.
A person with cataract will have blurred or double vision and he will frequently feel the need to change his eyeglasses. He will also experience the scattering of light coming from one single source. Cataracts, even the incipient ones, can be readily detected during the routine eye examinations. The treatment available for the cataract is surgical and is done mostly on an outpatient basis. The urgency of the cataract surgery depends on the severity of the disease and the need of the patient.
There are three different ways pf removing a cataract: extracapsular surgery, phacoemulsification, and intracapsular surgery. Phacoemulsification is a variation of the extracapsular surgery in which only the core of the lens is removed with the help of the ultrasound.
A cataract is an opacification or cloudiness of the eye's crystalline lens due to aging, disease, or trauma that typically prevents light from forming a clear image on the retina. If visual loss is significant, surgical removal of the lens may be warranted, with lost optical power usually replaced with a plastic intraocular lens (IOL). Due to the high prevalence of cataracts, cataract extraction is the most common eye surgery. The two main types of cataract extraction are intracapsular cataract extraction (ICCE) and extracapsular cataract extraction (ECCE).
Intracapsular cataract extraction
Extracapsular cataract extraction
A capsulotomy is a procedure to open a portion of the lens capsule. An anterior capsulotomy refers to the opening of the front portion of the lens capsule, whereas a posterior capsulotomy refers to the opening of the back portion of the lens capsule. In an extracapsular surgery, the surgeon performs an anterior capsulotomy, or capsulorhexis, to create an opening through which the lens nucleus can be removed and the intraocular lens implant inserted. An opacification or clouding of the posterior lens capsule frequently occurs in those who have had an extracapsular cataract extraction procedure, therefore, a laser posterior capsulotomy, or YAG laser capsulotomy, is used to clear the back implant surface.
involves the removal of the lens while the elastic lens capsule is left partially intact to allow implantation of an intraocular lens. There are two main types of extracapsular surgery: conventional ECCE and phacoemulsification. Conventional extracapsular cataract extraction involves manual expression of the lens through an incision made in the cornea or sclera. Although it requires a larger incision and the use of stitches, the conventional method is indicated for patients with very hard cataracts or weak corneal epithelial tissue. Phacoemulsification involves the use of an ultrasonic vibrating handpiece to shatter and break up a cataract, thus making it easier to remove. Because a smaller incision is required, few or no stitches are needed and the patient's recovery time is usually shorter. involves the removal of the lens and the surrounding lens capsule in one piece. The procedure has a relatively high rate of complications due to the large incision required and pressure placed on the vitreous body, thus is rarely performed in countries where operating microscopes and high-technology equipment are readily available . Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogen . Although it is now used primarily for the removal of subluxated lenses, it was the favored form of cataract extraction from the late 1960s to the early 1980s.
Types of cataracts
Classified by etiology
- Age-related cataract
- Congenital cataract
- Secondary cataract
- Traumatic cataract
Classified by location
- Anterior cortical cataract
- Anterior polar cataract
- Anterior subcapsular cataract
- Nuclear cataract
- Posterior cortical cataract
- Posterior polar cataract
- Posterior subcapsular cataract
Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea" but in common usage may refer to any inflammatory process involving the interior of the eye.
Uveitis is estimated to be responsible for approximately 10% of the blindness in the United States. Uveitis requires a thorough examination by an ophthalmologist.
Uveitis is usually categorized anatomically into anterior, intermediate, posterior and panuveitic forms.
Anywhere from two-thirds to 90% of uveitis cases are anterior in location (anterior uveitis), frequently termed iritis - or inflammation of the iris and anterior chamber. This condition can occur as a single episode and subside with proper treatment or may take on a recurrent or chronic nature. Symptoms include red eye, injected conjunctiva, pain and decreased vision. Signs include dilated ciliary vessels, presence of cells and flare in the anterior chamber, and keratic precipitates ("KP") on the posterior surface of the cornea.
- Intermediate uveitis
- Posterior uveitis
Pan-uveitis is the inflammation of all the layers of the uvea.is the inflammation of the retina and choroid.
Glaucoma is a group of diseases of the optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. Although raised intraocular pressure is a significant risk factor for developing glaucoma, there is no set threshold for intraocular pressure that causes glaucoma. One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressures for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.
The most common type, primary open angle glaucoma (POAG), frequently has no symptoms and has been nicknamed "the sneak thief of sight". One factor may be a relative obstruction on the outflow of aqueous humour from the eye. Aqueous humour is produced by the ciliary body of the eye, and then flows through the pupil and into the anterior chamber. The trabecular meshwork then drains the humour to Schlemm's canal, and ultimately to the venous system. All eyes have some intraocular pressure, which is caused by some resistance to the flow of aqueous through the trabeculum and Schlemm's canal. If the intraocular pressure (IOP) is too high, (>21.5 mm Hg), the pressure exerted on the walls of the eye results in compression of the ocular structures. However, other factors such as disturbances of blood flow in the optic nerve head may interact with IOP to affect the optic nerve. In one third of cases of POAG there is statistically normal IOP. This is called normal tension glaucoma (NTG). Because optic nerve examination and perimetry testing are not always done in addition to IOP measurement in those at risk, NTG is under diagnosed and the condition presents late.
Another type, acute angle-closure glaucoma, is characterized by an acute rise in the intraocular pressure. This occurs in susceptible eyes when the pupil dilates and blocks the flow of fluid through it, leading to the peripheral iris blocking the trabecular meshwork. Acute angle-closure glaucoma can cause pain and reduced visual acuity (blurred vision), and may lead to irreversible visual loss within a short time. This is an ocular emergency requiring immediate treatment. Many people with glaucoma experience halos around bright lights as well as the loss of sight characterized by the disease.
Primary congenital glaucoma
Conjunctivitis or pink eye is the inflammation of the conjunctiva, the thin membranous lining on the inner surface of the eyelid and the outer part of the eyeball. During conjunctivitis, the eye becomes reddened and has a runny discharge. This discharge makes the eyelids stick together during sleep and may cause itching and hypersensitivity to light. The causes of conjunctivitis can range from viral infection to bacteria and gonorrhea and Chlamydia.
Keratoconjunctivitis is the combination of conjunctivitis and Blepharoconjunctivitis is the combination of conjunctivitis with blepharitis.
There are three common varieties of conjunctivitis, viral, allergic, and bacterial. Other causes of conjunctivitis include thermal and ultraviolet burns, chemicals, toxins, overuse of contact lenses, foreign bodies, vitamin deficiency, dry eye, dryness due to inadequate lid closure, exposure to chickens infected with Newcastle disease, epithelial dysplasia (pre-cancerous changes), and some conditions of unknown cause such as sarcoidosis.
- Viral conjunctivitis is spread by aerosol or contact of a variety of contagious viruses, including many that cause the common cold, so that it is often associated with upper respiratory tract symptoms. Clusters of cases have been due to transfer on ophthalmic instruments which make contact with the eye (e.g., tonometers) and have not been adequately sterilized.
- Allergic conjunctivitis occurs more frequently among those with allergic conditions, with the symptoms having a seasonal correlation. It can also be caused by allergies to substances such as cosmetics, perfume, protein deposits on contact lenses, or drugs. It usually affects both eyes, and is accompanied by swollen eyelids.
- Bacterial conjunctivitis is most often caused by pyogenic bacteria such as Staphylococcus or Streptococcus from the patient's own skin or respiratory flora.
Irritant, toxic, thermal and chemical conjunctivitis are associated with exposure to the specific agents, such as flame burns, irritant plant saps, irritant gases (e.g., chlorine or hydrochloric acid ('pool acid') fumes), natural toxins (e.g., ricin picked up by handling castor oil bean necklaces), or splash injury from an enormous variety of industrial chemicals, the most dangerous being strongly alkaline materials.
Xerophthalmiais a term that usually implies a destructive dryness of the conjunctival epithelium due to dietary vitamin A deficiency—a condition virtually forgotten in developed countries, but still causing much damage in developing countries. Other forms of dry eye are associated with aging, poor lid closure, scarring from previous injury, or autoimmune diseases such as rheumatoid arthritis, and these can all cause chronic conjunctivitis.
Redness, irritation and watering of the eyes are symptoms common to all forms of conjunctivitis. Itch is variable.
Conjunctivitis sometimes requires medical attention. The appropriate treatment depends on the cause of the problem. For the allergic type, cool compresses and artificial tears sometimes relieve discomfort in mild cases. In more severe cases, non-steroidal anti-inflammatory medications and antihistamines may be prescribed. Some patients with persistent allergic conjunctivitis may also require topical steroid drops.
Bacterial conjunctivitis is usually treated with antibiotic eye drops or ointments that cover a broad range of bacteria.
Macular degeneration is a medical condition where the light sensing cells in the macula malfunction and over time cease to work. According to the American Academy of Ophthalmology, it is the leading cause of central vision loss (blindness) in the United States today for those over the age of fifty. There are two basic types of the disease: Standard Macular Degeneration (MD) and Age Related Macular Degeneration (ARMD), with ARMD being the most common form of the condition. Macular degeneration that is not age related is most commonly caused by an inherited condition. These forms are sometimes called Juvenile macular degeneration (JMD). In macular degeneration the final form results in missing or blurred vision in the central, reading part of vision. The outer, peripheral part of the vision remains intact.
Age related macular degeneration
ARMD is further divided into a "dry," or non-exudative, form and a "wet," or exudative, form. Eighty five to ninety percent of cases are categorized as "dry" macular degeneration where fatty tissue, known as drusen, will slowly build up behind the retina. Ten to fifteen percent of cases involve the growth of abnormal blood vessels under the retina. These cases are called "wet" macular degeneration due to the leakage of blood and other fluid from behind the retina into the eye. Wet macular degeneration usually begins as the dry form. If allowed to continue without treatment it will completely destroy the macula. Medical, photodynamic, laser photocoagulation and laser treatment of wet macular degeneration are available.
Fluorescein angiography is a special study of the blood vessels in the retina, and it helps the doctor in detecting an overgrowth of the blood vessels. Exudative laser surgery, if carried out in time, can cure the exudative macular degeneration. Newly-formed abnormal blood vessels are sealed off by laser photocoagulation.
? Blurred vision: Those with non-exudative macular degeneration may by asymptomatic or notice a gradual loss of central vision, whereas those with exudative macular degeneration often notice a rapid onset of vision loss.
? Central scotomas
? Distorted vision (i.e. metamorphopsia) - A grid of straight lines appears wavy and parts of the grid appear blank.
? Trouble discerning colors; specifically dark ones from dark ones and light ones from light ones.
? Pigmentary alterations
? Exudative changes: hemorrhages, hard exudates, subretinal/sub-RPE/intraretinal fluid
? Atrophy: incipient and geographic
? Visual acuity drastically decreasing (two levels or more) ex: 20/20 to 20/80.
? Holes visible in fundus photographs.
occurs as a complication of various medical conditions such as eye surgery, advanced cataracts, eye injuries, some eye tumors, uveitis, diabetes or use of corticosteroid drugs. or buphthalmos is a rare genetic disease affecting infants. Newborns present with enlarged globes and clouded corneas. It is thought that reduced trabecular permeability is the cause of increased intraocular pressure. Surgery is the treatment.
consists of vitritis - inflammatory cells in the vitreous cavity, sometimes with snowbanking, or deposition of inflammatory material on the pars plana.
Glaucoma Conjunctivitis Macular Degeneration
Retinopathy or retinitis pigmentosa is a general term designating the diseases affecting the retina with loss of vision and often due to systemic disorders.
The two major kinds of retinopathy are hypertensive and diabetic. People with chronic hypertension undergo degenerative retinal changes due to the impairment of the blood supply to the retina. As a result, arteriosclerosis develops, and there are other apparent physical changes due to the vascular damages.
As for diabetic retinopathy, it can be proliferative as well as non-proliferative. Proliferative retinopathy is characterized by the neovascularization of the retina enhancing the chances of vitreous hemorrhage and retinal tears.
Physicians make use of fluorescein angiography to detect the retinopathy, and the treatment is done through the laser coagulation or surgery. Non-proliferative retinopathy is characterized by retinal edema, venous dilation, microaneurysms, hard exudates, and retinal hemorrhages. This is treated with laser coagulation.
Strabismus, also known as "heterotropia", "squint", "crossed eye", "wandering eye", or "wall eyed", is a disorder in which the eyes do not point in the same direction. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space, preventing proper binocular vision, which may adversely affect depth perception. The cause of strabismus can be a disorder in one or both of the eyes; for example, nearsightedness or farsightedness, making it impossible for the brain to fuse two different images.
When strabismus is congenital or develops in infancy, it can cause amblyopia, in which the brain ignores input from the deviated eye although it is capable of normal sight. Since strabismus can cause amblyopia, which is sometimes referred to as lazy eye, it is sometimes itself inaccurately referred to as lazy eye.
Strabismus may be concomitant or incomitant. Concomitant strabismus means that the strabismus is equal regardless of which direction the gaze is targeted. This indicates that the individual extraocular muscles function individually, but that they may simply not be aimed at the same target. Concomitant strabismus in a child under the age of 6 rarely indicates serious neurologic disorder. Blindness in one eye usually causes concomitant strabismus, with the eye of a child turning inward, and that of an adult turning outward.
Incomitant strabismus occurs when the degree of misalignment varies with the direction of gaze. This indicates that one or more of the extraocular muscles may not be functioning normally. Types of strabismus include:
- Esotropia, or one eye turning inward;
- Exotropia, or one eye turning outward;
- Hypertropia, or one eye turning upward.
- Hypotropia, or one eye turning downward.
- Medial strabismus manifests as the inability to abduct (move laterally) one's eye. This is usually caused by damage to the abducens nerve or abducens nucleus. The result is that the eye in its normal resting state deviates medially, as the movements of the medial rectus muscle are less opposed by the denervated lateral rectus muscle.
As with other binocular vision disorders, the primary therapeutic goal for those with strabismus is comfortable, single, clear, normal binocular vision at all distances and directions of gaze. If minor and detected early, strabismus can often be corrected with enforced use of an eye patch on the dominant eye and/or vision therapy. Advanced strabismus is usually treated with a combination of eyeglasses or prisms, vision therapy, and surgery, depending on the underlying reason for the misalignment. Surgery attempts to align the eyes by shortening, lengthening, or changing the position of one or more of the extraocular eye muscles, and is frequently the only way to achieve cosmetic improvement. Glasses affect the position by changing the person's reaction to focusing. Prisms change the way light, and therefore images, strike the eye, simulating a change in the eye position.
is the false appearance of strabismus. It generally occurs in infants and toddlers whose bridge of their nose is wide and flat. This causes the appearance of strabismus.
A stye (also spelled sty) is an inflammation of the sebaceous glands at the base of the eyelashes. They are harmless but can be very painful. They are generally caused by a Staphylococcus bacteria infection. They are particularly common in infants.
The stye may form on either the inside or the outside of the eyelid.
An external stye (
An internal stye (
Most styes will drain on their own though this may be accelerated with a hot or warm compress. Medical professionals advise that patients not attempt to squeeze or apply excessive pressure to styes.
external hordeolum) will show as a tender, red swelling on the edge of the eyelid and will tend to drain itself quickly. internal hordeolum) will also be tender and may show external red swelling. Internal styes often take longer to heal because the abscess cannot drain as easily. These types of styes can also cause blurred vision and irritation.
A scotoma (Greek: darkness) is an area or island of loss or impairment of visual acuity surrounded by a field of normal or relatively well preserved vision.
Every human eye has a scotoma in its field of vision, usually termed its blind spot. The presence of this normal scotoma does not intrude into consciousness because it is very small, but it can be demonstrated to oneself by the simplest of clinical methods.
Symptom-producing or pathological scotomata may be due to a wide range of disease processes, affecting either the retina (in particular its most sensitive portion, the macula) or the optic nerve itself. A pathological scotoma may involve any part of the visual field and may be of any shape or size. A scotoma may include and enlarge the normal blind spot. Even a small scotoma that happens to affect central or macular vision will produce a severe visual handicap, whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer.
Common causes of scotomata include demyelinating disease such as multiple sclerosis (retrobulbar neuritis), toxic substances such as methyl alcohol and quinine, nutritional deficiencies, and vascular blockages either in the retina or in the optic nerve. Less common, but important because sometimes reversible or curable by surgery, are scotomata due to tumors such as those arising from the pituitary gland, which may compress the optic nerve or interfere with its blood supply.
Hemianopsia is the loss of half the vision in both eyes. It is categorized in to
- Binasal hemianopsia
- Bitemporal hemianopsia
In binasal hemianopsia vision is missing in the inner half of both the right and left visual fields.
- Binasal hemianopsia can be broken down as follows:
- bi-: involves both left and right visual fields
- nasal: involves the nasal visual field
- hemi-: involves half of each visual field
- anopsia: blindness
Bitemporal hemianopsia is the medical description of a type of partial blindness that is associated with lesions of the optic chiasm, the area where the optic nerves from the right and left eyes cross near the pituitary gland.
The absence of vision in half of a visual field is described as hemianopsia.
The visual field of each eye can be divided in two vertically, with the outer half being described as temporal, and the inner half being described as nasal.
In bitemporal hemianopsia vision is missing in the outer half of both the right and left visual fields. Pituitary adenomata are associated with this kind of visual deficit, as are certain injuries.
Bitemporal hemianopsia can be broken down as follows:
- bi-: involves both left and right visual fields
- temporal: involves the temporal visual field
- hemi-: involves half of each visual field
- anopsia: blindness
A pinguecula is a common, nonmalignant growth of the mucous membrane that lines the eyeball and underside of the eyelids, conjunctiva. It appears as a small, yellowish lesion derived from the conjunctiva. It can appear on either side of the cornea, but usually appears on the nasal side. It may increase in size over many years. The cause is unknown, but chronic sunlight exposure and eye irritation is shown to contribute in its development. Welding is a significant occupational risk.
The chief symptom is a yellow or white nodule on the conjunctiva near the cornea. An eye examination is often sufficient to diagnose this disorder. This condition is benign and often no treatment is required except for lubrication with artificial tears and temporary use of mild steroid eye drops. Rarely, it may need to be excised.
is the medical description of a type of partial blindness that is associated with certain lesions of the eye, and of the central nervous system, such as congenital hydrocephalus. The absence of vision in half of a visual field is described as hemianopsia. The visual field of each eye can be divided in two vertically, with the outer half being described as temporal, and the inner half being described as nasal.
- Macular Degeneration
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Chapter IV-Eye Pathology