CORNEA
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CORNEA
The cornea is the eye’s outermost layer. It is the clear, domeshaped surface that covers the front of the eye. It plays an important role in focusing your vision.It covers the pupil, iris and anterior chamber.
FUNCTION
The clear cornea allows light to enter the eye for vision. It provides approximately 50 percent of the focusing power of the eye. It helps to shield the rest of the eye from germs, dust, and other harmful matter.The cornea shares this protective task with the eyelids, the eye socket, tears, and sclera
KERATOCONUS is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape.
This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision.
Keratoconus can occur in one or both eyes and often begins during a person's teens or early 20s.
In some cases, it appears to be genetic (passed down in families). About 1 out of 10 people with keratoconus have a parent who has it too.
Double Vision
Distorted Vision
Image-Ghosting
Increased sensitivity to light and glare
Eye Redness
Frequent change of spectacles
Uncomfortable Contact Lenses
Blurred Vision
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1. Speciality Contact Lenses: a) Soft Lens/Soft Toric lenses
1. Speciality Contact Lenses: b) Semi-soft/ Hybrid lenses: Rose-k, Supercone
1. Speciality Contact Lenses: c) Scleral lenses
1. Speciality Contact Lenses: d) Rigid lens: RGP
1. Speciality Contact Lenses: e) Piggyback lenses
2.Corneal collagen crosslinking (C3R)
3. INTACS
4. Phakic IOL’s
5.Keratoplasty(Cornea Transplant)
CORNEAL INFECTION is an infection of the anterior most part of the eye (cornea) most likely seen after any trauma to the eye .
It can be of bacterial, viral, fungal or parasitic origin.
Usually it happens post trauma to the eye, unhygienic contact lens wear, foreign/vegetable matter entry into the eye, insect fall into the eye, immunocompromised individual, surgical procedures etc.
Patient can present with symptoms of pain, redness of the eye, watering, coloured discharge and whitish discolouration of the cornea.
CORNEAL DYSTROPHIES are a group of genetic, often progressive, eye disorders in which abnormal material often accumulates in the clear (transparent) outer layer of the eye (cornea).
Corneal dystrophies may cause significant vision impairment.
The age of onset and specific symptoms vary among the different forms of corneal dystrophy.
Most forms of corneal dystrophy affect both eyes, progress slowly, do not affect other areas of the body, and tend to run in families.
EPITHELIAL DYSTROPHY: This disorder affects the outermost layer of the cornea
Recurrent erosion syndromes/ Anterior Basement membrane dystrophy: It is a commonly seen condition usually seen secondary to trauma wherein the patient presents with
Mild pain on awakening
Blurred vision/ image ghosting
It happens due to the weak adhesions between the superficial epithelium and the underlying basement membrane
Management: It is treated by topical lubricants, patching, debridement, soft contact lens.
Surgical intervention is done in severe cases like anterior micropuncture and excimerlaser ablation(PTK)
STROMAL DYSTROPHY: This disorder affects the mid portion of the cornea (i.e. stroma) in which typically an abnormal substance gets accumulated .
ANTERIOR MEMBRANE DYSTROPHIES:
REIS BUCKLER DYSTROPHY
HONEYCOMB DYSTROPHY
STROMAL DYSTROPHIES:
LATTICE DYSTROPHY
GELATINOUS DROP LIKE DYSTROPHY
GRANULAR DYSTROPHY
MACULAR CORNEAL DYSTROPHY
SCHNYDER CRYSTALLINE DYSTROPHY
CONGENITAL HEREDITARY STROMAL DYSTROPHY
ENDOTHELIAL DYSTROPHY: This disorder affects the innermost layer of the cornea(i.e. endothelium)
FUCHS DYSTROPHY:
Progressive loss of endothelial cells
More common in females
Presents in middle age and vision loss is progressive
Guttae are seen in the central corneal endothelium
TREATMENT :
Hypertonic solutions/ointments in the initial stages, BCL(bandage contact lens), anterior stromal puncture
DSEK(Descmets stripping endothelial keratoplasty) in the latter stages
POSTERIOT POLYMORPHOUS DYSTROPHY
CORNEAL ABRASION is a disruption in the superficial layer of the cornea (epithelium) secondary to fingernail trauma, pen injuries etc
MANAGEMENT:
Antibiotic drops, eye patching, bandage contact lens
CORNEAL TEAR is a disruption in ¾ to full thickness of the layers of cornea
Can be associated with internal injuries like cataract formation, internal tissue prolapse, entry of foreign particles into the eye, infection of the wound, retinal detachment with or without loss of vision.
MANAGEMENT:
Corneal tear repair needs to be handled as early as posible
KERATOMALACIA is an eye disorder that results from vitamin A deficiency.
Vitamin A is required to maintain specialized epithelia (such as in the cornea and conjunctiva).
CAUSES:
Delayed weaning
Inadequate nutrition
Non breast fed babies with poor maternal malnutrition
Vitamin absorption disorders
SYMPTOMS:
Night blindness, or difficulty adjusting your vision in dim or dark light
Extreme dryness of the eyes
Cloudiness in your corneas
Bitot’s spots, or a buildup of debris that lodge in your conjunctiva
The spots appear as foamy, light gray, patches
MANAGEMENT:
Vitamin A injection 200000 IU
BULLOUS KERATOPATHY refers to an irreversible corneal edema(swelling) and endothelial cell damage that occurs commonly after cataract extraction with or without IOL(Intra Ocular Lens) implantation.
CAUSES:
Prexisting low endothelial cell count prior to surgery
Surgical endothelial trauma
Descemets membrane detachment during surgery
SYMPTOMS
The swelling leads to the formation of fluid-filled blisters on the surface of the cornea.
Sensitivity when looking at bright lights and significant blurring of vision can result.
The blisters can rupture, causing severe pain, often with the sensation of a foreign object trapped in the eye, and can further impair vision.
MANAGEMENT
It is aimed at reducing discomfort and/or increasing visual acuity
Hypertonic drops/ointment, extended wear contact lenses
SURGICAL:
In eyes with good visual potential DSEK(Descmets membrane endothelial keratoplasty) is performed
BAND SHAPED KERATOPATHY refers to a condition in which calcium salts are precipitated on the surface of cornea, either due to local or systemic causes
The cornea bears a grayish- white plaque in the Bowmans membrane and superficial stroma
CAUSES:
Chronic ocular disease (usually inflammatory) such as uveitis in children, interstitial keratitis, severe superficial keratitis, and phthisis bulbi
Hypercalcemia caused by hyperparathyroidism, vitamin D toxicity, milk–alkali syndrome, sarcoidosis, and other systemic disorders
Elevated serum phosphorus with normal serum calcium, which sometimes occurs in patients with renal failure
Chronic exposure to mercurial vapors or to mercurial preservatives (phenylmercuric nitrate or acetate) in ophthalmic medications
Silicone oil instillation in an aphakic eye
TREATMENT:
Chemical Chelation-EDTA solution is used to soak the cornea and then calcium particles are scraped over the cornea
Severity of the chemical injury depend on the nature of the chemical and time of contact with the eye.
a)ACID: assaults and industrial accidents
b)ALKALI: household cleaners, bleaches and construction components
c)Thermal: hot metals or kitchen accidents
If any chemical injury the patient should wash the eyes with clean drinking water and rush to the doctor immediately
Immediate profuse irrigation for 30 mins
Examination is done under microscope
Meticulous removal of all embedded chemical material is done
Antibiotic prophylaxis is started
Profuse lubrication, steroids, vit c
Surgical: Amniotic membrane transplantation, SLET(Simple limbal epithelial transplantation) as and when needed
Foreign body entering the eye(ex-stone, metal particle, Insect parts) can get embedded into the cornea
SYMPTOMS:
Pain
Watering
Foreign body sensation
Redness
Corneal infection
MANAGEMENT:
Foreign body needs to be removed immediately
The eye is anaesthetised using topical anaesthetic drops and foreign body is removed with the needle under the slitlamp view
It is commonly known as cornea transplant.
It is a full thickness transplant procedure wherein all the layers of the cornea are replaced with a donor cornea, done to restore clarity of the vision(scarred cornea) in various conditions.
Steps of the procedure:
1. Initially a trephine is used to make a cut in the host cornea 360 degress
2. The host cornea is cut all through out
3. The donor cornea is then cut with a size increase of 0.5mm
4. The donor cornea is then sutured to the residual host cornea with 10-0 nylon sutures
THERAPEUTIC KERATOPLASTY:
It is basically a penetrating keratoplasty (full thickness transplant ) procedure (described above) done in cases to salvage the eye , reduce the load of infection in the eye.
INDICATIONS:
Corneal ulcers
Painful blind eye
DALK –
DEEP ANTERIOR LAMELLAR KERATOPLASTY:
Similar to a cornea transplant but only the superficial layers of the cornea (i.e epithelium, bowmans and part of the stroma) are transplanted.
DESCMETS STRIPPING ENDOTHELIAL KERATOPLASTY:
This is also a part of cornea transplant wherein only the innermost layer of the cornea(i.e endothelium, dua and part of the stroma) is transplanted .
No corneal sutures are required for this procedure
DESCEMETS MEMBRANE ENDOTHELIAL KERATOPLASTY:
This is also a part of cornea transplant wherein only the innermost layer of the cornea(i.e endothelium,descmets) is transplanted .
No corneal sutures are required for this procedure
SIMPLE LIMBAL EPITHELIAL TRANSFER:
It is a surgical technique done in cases of 360 degree limbal stem cell loss to restore the ocular surface and renew the corneal epithelium.
In this procedure stem cells from the healthy (other) eye of the patient is transferred to the stem cell deficient eye.
Indications:
Chemical burns
Thermal burns
Immunologic diseases (Steven Johnson’s Syndrome, TEN syndrome, Ocular Cicatricial Pemphigoid)
It is a procedure wherein the superficial layers of the cornea (Epithelium, Bowmans and part of the anterior stroma)are ablated using excimer laser.
This procedure is done in corneal surface irregularities, superficial scars,epithelial instability etc
Indications:
Spheroidal degeneration
Salzmann nodular degeneration
Calcium band keratopathy
Recurrent corneal erosion syndrome
Keratitis
Bullous keratopathy
Anterior corneal dystrophies (Cogan, Meesman, Reis-Bückler, etc)
Superficial scars (leukomas)
It is a cosmetic procedure done to alter their eyes following corneal infection, trauma, scarring causing corneal opacities.
It helps to alter a discoloration, blending an opacity into the normal eye color.
The procedure is usually performed on patients who have lost their vision.
Corneal tattooing is sometimes performed on patients who still have vision to reduce symptomatic glare in certain conditions.
PROCEDURE:
The ink is applied onto the cornea stroma by multiple punctures, covering the needle with ink each time
Also lamellar pockets are made in the stroma and the ink is stuffed inside the cornea
Indian ink is the most commonly used, providing safe and long-lasting effects
It is a procedure wherein an artificial cornea(prosthesis) is fitted to the eye.
The Keratoprothesis is usually performed when a standard corneal transplant has failed or when such a transplant would be unlikely to succeed.
Its optical system can provide normal vision if the rest of the eye is undamaged
Indications for Keratoprosthesis include:
• Failed corneal graft with poor prognosis for further grafting
• Vision less than 20/200 in the affected eye and compromised vision in the opposite eye
• No end-stage glaucoma or retinal detachment
PROCEDURE:
The device is inserted into a corneal graft, which is then sutured into the patient’s cornea as in standard transplantation.
If the natural lens is in place, it is also removed.
In this procedure a neutral solution of disodium ethylenediaminetetraacetic acid (EDTA; usual concentration 0.5%–1.5%), is used to remove the calcium
PROCEDURE:
The epithelium overlying the calcium needs to be removed prior to applying the chelating solution
EDTA solution is applied over the cornea in a waterbath or using soaked cotton tipped applicator for 5 minutes
Scraping with the blade will remove the calcium particles and clear the visual axis
What is Contact lens?
Contact lens are thin lens placed directly on the surface of cornea. These are aids which are worn to correct vision , for cosmetic or therapeutic reasons.
Types of Contact Lenses
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Rigid gas permeable lenses
They are made of plastics and other materials such as silicone or flouropolymers . They hold their shape, yet allow the free flow of oxygen through the lenses to the cornea. RGP lenses may be the best choice when the cornea has enough astigmatism (is shaped like an egg instead of an orange) that a soft lens will not provide sharp vision.
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soft contact lenses
They are made of plastic materials that incorporate water. This makes them soft and flexible allowing oxygen to reach the cornea.
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disposable wear lenses
Although more expensive, carry a lower infection risk and more convenient. They are replaced daily, weekly, biweekly or monthly basis.
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Extended wear lenses
Most extended wear (EW) contacts are thinner than daily wear lenses and are made of silicone hydrogel. This advanced soft lens material enables EW lenses to "breathe" better than daily wear lenses, allowing more oxygen to reach the cornea. This is especially important when lenses are worn continuously for extended periods of time.
Two brands of silicone hydrogel EW lenses — Air Optix Night & Day (Alcon) and PureVision (Bausch + Lomb) — are the new generation extended wear lenses. -
colored lenses
They are contacts that change your eye color, the appearance of your eye, or both. And in the case of circle lenses they can also make your iris appear bigger. Colored lenses are available by prescription and should only be worn after an eye exam and fitting by a qualified eye care professional.
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toric soft contact lenses
The term "toric contact lenses" usually is used to describe specially designed soft contact lenses that correct astigmatism. Most toric contacts for astigmatism are indeed soft lenses — made either of a conventional hydrogel material or a highly breathable silicone hydrogel.
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bifocal or multifocal lenses
They are available in both soft and RPG varieties. They can correct nearsightedness, farsightedness and astigmatism in combination with presbyopia. Cleaning and disinfection are specific to the lens material. Visual quality is often not as good as with single vision lenses; however, for some people the ability to correct presbyopia is worth it.
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rose k lenses
These are gas permeable lenses designed especially for keratoconus. These lenses are custom fit to each eye to correct myopia and astigmatism resulting from keratoconus.
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Sclera lenses
These are large diameter gas permeable contact lens for keratoconus and irregular corneas. They are also used in patients who are sensitive to RGP lens and require visual correction for higher degrees of astigmatism.
Uses of Contact Lenses
Risks of Contact Lenses
While contact lenses are safely used by millions of people every day, they do carry a risk of eye infection.The single best way to avoid eye infections is to follow proper lens care guidelines as prescribed by your eye care professional. In particular, including a "rub and rinse" step in the lens cleaning process, minimizing contact with water while wearing contact lenses and replacing the lens case frequently can help reduce the risk of infection
Care of Contact Lenses
1. Before handling contact lenses, wash your hands with soap and water, then rinse and dry them with a lint-free towel.
2. Minimize contact with water, including removing lenses before going swimming or in a hot tub.
3. Contact lenses should not be rinsed with or stored in water (tap or sterile water).
4. Do not put your lenses in your mouth to wet them. Saliva is not a sterile solution.
5. Do not use saline solution and rewetting drops to disinfect lenses. Neither is an effective or approved disinfectant.
6. Wear and replace contact lenses according to the schedule prescribed by your eye care professional.
7. Follow the specific contact lens cleaning and storage guidelines from your eye care professional and the solution manufacturer.
8. During cleaning, rub your contact lenses with your fingers, then rinse the lenses with solution before soaking them).
9. Rinse the contact lens case with fresh solution — not water. Then leave the empty case open to air dry.
10. Keep the contact lens case clean and replace it regularly, at least every three months.
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Over 95% of all corneal transplant operations successfully restore the corneal recipient’s vision.
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There is no substitute for human tissue. The transplantation process depends upon the priceless gift of corneal donation from one human to another. Donated eyes are also needed for research and education.
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Cornea transplant has to be done as early as possible. It can be performed up to one week depending upon the method of corneal preservation
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Yes.
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Signs and symptoms of corneal abrasion include pain, tearing, a gritty feeling in the eye, Redness, Sensitivity to the light and Headache.