Corneal Edema Presented by: Dr. Omar Abdulrazzak Supervised by: Dr. Buraa kubaisi
Corneal Edema
Presented by: Dr. Omar Abdulrazzak
Supervised by: Dr. Buraa kubaisi
Thickness of the cornea in the center 0.52 mm while at periphery is 0.67 mm
Epithelium is 50-90 micrometer
thick BM is 8-14 Mcirometer
Stroma is 0.5 mm thick and
constitute most of the cornea DM is 10-12 Micrometer
Endothelium is 18-20
Micrometer with 2400-3000 cells/mm2
Cornea
To perform its primary function of refraction of light the cornea must be relatively thin and dehydrated with smooth anterior surface
In normal cornea, optical transparency is directly related to the state of hydration of the tissue
If cornea swells, it increases its thickness, its surface becomes irregular both changes downgrades its optic properties.
Corneal hydration
Cornea is relatively in dehydrated state for its transperancy.
Water content of cornea is 80% which is highest of any connective tissue in the body
thickness increases and % its central 80 aboveIf hydration becomes transperancy reduces
Cornea swells only in the direction of its thickness therefore, corneal thickness and hydration are linearly related
hydration
Factors draw water into the cornea
swelling pressure of sromal matrix
intraocular pressure
Factors prevent water to flow into the cornea
Mechanical barriers
Na+/ K+ pump of Endothelium
Stromal swelling pressure A.
Pressure exerted by corneal stroma mainly GAGs is stromal pressure (SP) SP is 60 mmhg, is a keystone of corneal biophysics Anionic charges on GAGs molecule expands the tissue, draws fluid with
equal but negative pressure called imbibation pressure. In vivo imbibation pressure is reduced by IOP, so IP = IOP – SP IP = 17-60 = -43 mmhg In vitro IP=SP SP generates interfibrillar tension may be biophysical mechanism to
maintain fibrils normal arrangement Cornea has an swelling pressure, which is maintained by endothelial
metabolic pump
B. barrier mechanism
Both epithelium and endothelium acts as a barrier for excessive flow of water and diffusion of electrolytes into stroma
As compare to endothelium, epithelium offers twice resistance Endothelium allows diffusion of small solutes like Nacl and urea, while
epithelium produces hypertonicity of the solution bathing the cornea Endothelial cells are attached to each other by discontinuous tight
junction i.e maculae occludentes Endothelial barrier function is mainly calcium dependent A calcium free solution will reduce the barrier function and cause
stromal edema
C. NA+/ k+ pump
Present in endothelium, several fold more active than its epithelium counterparts
Activated ATPase mediates active extrusion of NA from stroma to the aqueous
It causes diffusion gradient for water NA conc. in aqueous is more compare to stroma, which draws water from
the stroma
Bicarbonate dependent ATPase has also been reported in the endothelial cells
Depletion of bicarbonates induces swelling
Carbonic anhydrase enzyme has also been implicated in fluid transport, CAE inhibitors decreases flow of fluid from stroma to aqueous (found only in the endothelium)
D. Evaporation
Evaporation of water from precorneal tearfilm increases its osmolarity relative to cornea
Hypertonicity of tear film could draw water from cornea However this water loss is readily replaced by aqueous, it results in only a
little corneal dehydration
E. intra ocular pressure
Most of early writers assume corneal edema is due to mechanical forcing of aqueous into the cornea
But exoerimental event found out that to achieve this effect pressure required is 200 mmhg
More likely explanation is that the determining factors is endothelial damage
Edema
Word edema is derived from Greek word means swelling Formerly known as dropsy or hydropsy which means
accumulation of excessive fluid Etiology of corneal edema: Primary causes Secondary causes
Secondary causes A. Mechanical trauma
1. blunt non penetrating injury causes edema by injury to endothelium,
mostly it is reversible 2. Perforating injuries cause direct damage to the cornea, intra ocular FB
in AC can cause edema in inferior periphery where FB mainly settles 3. Forceps delivery cause pressure on globe, may cause edema due to DM
tear
4. Noxious chemicals mainly alkalies which penetrates cornea cause endothelium damage
5. Brown McLEAN syndrome : peripheral edema with brown black
discolouration of underlying endothelium seen in ICCE, ECCE, CCPE, pars plana vitrectomy
6. Cold induced reversible corneal edema has been reported trigeminal nerve dysfunction
7. Certain systemic medications like amantadine and cefaclor can cause
edema 8. Lasers used for iridotomy can cause focal corneal edema 9. High altitude corneal decompensation has been reported causing
hypoxia induced corneal edema
B. Glaucoma
Acute rise in IOP which exceeds swelling pressure of stroma causes epithelial edema
Hypoxic endothelial decompensation occurs due to diminished aqueous flow
When corneal endothelium is compromised, edema occurs even at lower level of IOP
Chronic elevation of IOP permanently damages the endothelium Irreversible corneal edema may occur.
Penetrating keratoplasty is the only treatment of choice in irreversible corneal edema, but IOP must be first controlled
In hypotony, AC is shallow or flat Mechanical trauma by cornea iris or
iris cornea touch leads to edema Normal human volunteers experiment study can be explained by
hypotony induced edema, (Corneal edema occurs in tightly patched eye)
C. Contact lenses
Most common cause of corneal edema is prolonged use of contact lens It is mainly due to insufficient supply of oxygen to eithelium Edema presents as microcystic epithelial edema near the center of
resting position of the lens If allowed to continue, it will cause stromal edema, descemet’s
membrane folds Edema easily clears if contact lens is removed Even altering the fit of contact lens is also successful in reducing edema
if it provides sufficient oxygen to the epithelium The response and recovery from edema is independent of age
D. ICE Syndrome
Iridocorneal endothelial syndrome is basically spectrum of disorders that includes : 1. progressive iris atrophy 2. chandler’s syndrome 3. iris nevus syndrome (Cogan Reese)
1. Iris atrophy: Essential iris atrophy
characterised by distortion of pupil, peripheral anterior synechie and iris atrophy with full thickness holes
Glaucoma commonly present in
the involved eye Unilateral, occurs in 4th and 5th
decades of life in Caucasians
2. Chandler Syndrome: Corneal endothelial abnormalities (hammered silver) Presents with blurred vision and haloes due to corneal
edema Corectopia may be mild to moderate Glaucoma may be less severe but at presentation IOP
may be normal Chandler syndrome have more severe edema
3. Cogan resse syndrome: Characterised by diffuse naevus which
covers iris or iris nodule Iris atrophy may be absent in 50% of
patients but corectopia and glaucoma may be severe
E. Essential corneal edema Idiopathic, episodic and often cyclic may be unilateral Presents with typical features of corneal edema like FB sensation,
diminished vision and haloes which persists for months then disappears Recurrent erosions on cornea may be noted It may be progress to the formation of bullae with ciliary injection and
urgent symptoms of pain and photophobia Pupils may be semidilated and sluggishy reacting to light If secondary infection does not set up attack passes of and the condition
eventually cleans up Some of these cases may be early presentation of dystrophic changes like
Fuch’s dystrophy
F. Metabolic disorders
Some vague concepts suggested by corneal edema occuring in some metabolic conditions like myxedema
It has also seen in hypercholesterolemia In malaria mainly in patients taking mepacrine for its treatment, in this
condition edema is limited to basal layer of epithelium and superficial layer of stroma
Primary Causes
Primary endothelial dystrophy : dystrophies involving endothelium and descemet’s membrane causes symmetrical marked stromal edema which is gradually progressive over a period of years, Congenital hereditary endothelial dystrophy Posterior polymorphous dystrophy
Primary endothelial dystrophy which develop later in life Fuch’s dystrophy
1. Congenital hereditary endothelial dystrophy: characterised by diffuse edema at birth or soon thereafter, without
significant anterior segment abnormalities
2. Posterior polymorphous dystrophy: B/L vesicular or linear lesions at the level of descemet’s membrane and
endothelium is present, it presents with congenital corneal edema
3. Fuch’s dystrophy: AD pattern of inheritance, earliest changes are limited to posterior cornea and presents with central bilateral asymmetrical corneal guttata
In Fuch’s dystrophy endothelial cells transform into fibroblast like cells capable of secreting collagen fibrils
Contribute to BM thickening
Progressive endothelial decompensation leads to stromal and epithelial edema Fluid in the stroma permeates the epithelial layer causes microcystic epithelial edema Individual epithelial cells burst, intercellular edema occurs and typical blisters or bullae formed These changes are confined to centre of cornea initially
Bullous keratopathy it represents the terminal stage of severe or prolonged epithelial
edema.
In the affected area the epithelium is steamy irregular and on its surface one or more large bullae appears, raised in the form of blebs.
After 2-3 days the Bullae rupture only to
reappear, the cycle associated with considerable irritation and pain
Treatment is extremely difficult, retrobulbar injection of alcohol, removal of endothelium by scraping, cauterisation of cornea by tincture iodine, trichloro-acetic acid
Bandage contact lens to relieve pain Lamellar grafting, if measures of therapy fails and if
recurrence persists treatment is enucleation
Manifestation of edema Depends upon cause and degree of the condition:
Mild discomfort in conditions like Fuch’s dystrophy Severe neuralgic pain is seen in Bullous Keratopathy Colour haloes Severe visual loss
Visual acuity
Small amount of epithelial edema can result in substantial reduction in visual acuity Although 70% stromal edema is compatible with normal visual acuity Decreased acuity is more severe in early morning IOP, iritis glaucoma and optic nerve changes may be contribute to reduced acuity
Pain and discomfort
As edema increases epithelium is detached from basement membrane to form bullae This rupture of bullae causes severe pain, photophobia, epiphora and narrowing of palpebral fissure Photophobia is due to light scattering in the edematous cornea Coloured haloes
Evaluation of corneal morphology
Slit lamp examination
Specular biomicroscopy
Pachymetry
Optical coherence
Scheimpflug camera
orbscan
1. Slit lamp examination
Examination reveals cornea guttata, stromal density, descemet’s membrane folds Bullae are easily observed by slit lamp In case of chronic corneal edema neovascularization, pannus formation or dystrophies are visible In case of stromal edema thickness exceeds 0.6 mm
2. Specular biomicroscopy Measures cell density Normal endothelial cells count is 3000-2000 cells/mm2
cell count less than 1000 poorly tolerate ocular surgery
Used in assesing cells in corneal grafting, LASIK, dystrophies corneal edema
3. Pachymetry: is the process of measuring the thickness of the cornea . It can be done using contact methods, such as ultrasound and confocal microscopy (CONFOSCAN), or noncontact methods such as optical biometry with a single Scheimpflugcamera (such as SIRIUS or PENTACAM), or optical coherence tomography (OCT), and online optical coherence pachymetry (OCP, such as ORBSCAN)
4. Optical coherence tomography: Is an established medical imaging technique It is widely used to obtain high resolution images of the retina and the anterior segment of the eye Corneal thickness can also be measured
5. Scheimpflug camera: Pentacam trade name, is a diagnostic unit able to perform five functions: Images of AS
3D anterior chamber analyzer
Pachymetry
Corneal topography
Cataract analyzer
6. Orbscan II : It analyses the physical shape/ contours of cornea and allows the surgeon to decide if it has suitable shape, is healthy and thick enough for treatment It is the only topographer currently available that measures the shape of both the front and back surface of the entire cornea (other systems only measure the front surface) and can therefore provide acomplete picture of the thickness of cornea
Management
o In all cases of corneal edema if documented IOP is high, its control with topical anti glaucoma drugs or systemic CAE inhibitors are given
o Even in moderately elevated IOP patients control may significantly
reduces epithelial edema o If IOP remains elevated despite maximum tolerated medical therapy
surgical intervention must be considered o Cyclocryotherapy / trabeculectomy are considered
Local therapy
o Early morning reduced vision can be improved by exposing eyes to warm air E.g: hair dryer
o Topical application of hyperosmotic agents like 5% NACL solution or
ointment can reduce edema to a little extend o If inflammation is a contributory cause of corneal edema, topical
application steroids may be very helpful o If the etiology of edema is not apparent 10 days course of topical
steroids can serve as diagnostic as well as therapeutic purpose o In patients with early corneal decompensation and mild edema a careful
refraction may improve vision o Therapeutic hydrophilic contact lens can be used
o Thin hydrophilic lens fitted flat on cornea allow maximum contact between lens and irregular cornea
o Application of radiodiathermy or other forms of electrocautery on
Bowman’s membrane o This produces adhesion between stroma and basal layer of epithelium
preventing formation of Bullae
Management
o Gunderson conjunctival flap with or without lamellar keratectomy can be performed to relieve pain
o Retrobulbar alcohol injection or tarsorrhaphy also may relieve pain o In painful blind eye or in absolute glaucoma enucleation may
represent the optimal procedure
Penetrating keratoplasty
o If visual recovery exists penetrating keratoplasty is performed before cauterisation of BM or conjunctival flap procedure
o In case of multiple graft failure and corneal thickness exceeds 1.5 mm,
the use of keratoprosthesis has been advocated o Keratoprosthesis is considered as an last ditch effort for visual
rehabilitation
Keratoprosthesis
o It causes high rate of failure and complications
o In case of bilateral corneal edema
keratoprosthesis in worst eye and keratoplasty in fellow is performed