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Choroidal coloboma
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Choroidal colobomaPresenter :Dr. RahulModerator: Dr. Archis
Coloboma
Coloboma (kolobomos :Greek for mutilation)
Indicates “a condition where a portion of the structure of the eye is lacking”
Epidemiology Incidence is 5 per 1,00,000 newborns
Prevalence is 1 in 10,000
60% are bilateral
Molecular genetics deletion in gene which maps to chromosome 7q26. a mutation in the PAX6 g # Warburg M
J Med Genet. 1993 Aug;30(8):664-9
Types
According to site of genesis
Typical Atypical
As an isolated anomaly with or without microophthalmia
Unilateral or Bilateral
Phenotypic classification
It may help the clinician to give a systematic description of the anomalies
Two major classesTotal Partial
Aetiological classification
• The aetiological classification consists of three classes: • Genetic• Prenatally acquired • Associations
• The aetiological classification can be applied to other congenital birth defects and improves counselling of families
#
# Warburg M J Med Genet. 1993 Aug;30(8):664-9Classification of microphthalmos and coloboma
Embryonic OriginThe eye is derived
from the neural tube (neuroectoderm), from which arise the retina proper
The neural crest cells produce the corneoscleral and uveal tunics
From the surface ectoderm, lens.
The earliest stage of eye development is the formation of the paired optic vesicles on either side of the forebrain.
These growing diverticula expand laterally into the mesoderm of the head and develop a stalk-like connection to the main portion of the rudimentary central nervous system
In humans, this process begins at about 22 days of development
The vesicles continue to grow, their connection to the brain becomes progressively narrower and more stalk-like.
This stalks will eventually become the rudiments of the optic nerves.
There is a seam at the bottom of each stalk, where blood vessels originally run.
This seam is known as the optic fissure or choroidal fissure or embryonic fissure.
The closure starts roughly in the middle of the developing eye, and runs in both directions.
This process is start at five week & finished by the seventh week of gestation.
If, for some reason, the closure does not happen, a uveal coloboma is formed
Depending on where the closure did not happen, the baby can have an iris coloboma (front
of the fissure) a chorio-retinal
coloboma (back of the fissure)
any combination of these.
).
Uveal coloboma can affect one eye (unilateral) or both eyes (bilateral)
A uveal coloboma may go from front to back continuous or have “skip lesions”.
The fact that the seam runs at the bottom of the stalk is the reason why uveal coloboma is always located in the lower inside corner of the eye.
PathophysiologyFusion or closure of
the fissure begins in its central portion in the 11-mm embryo and proceeds anteriorly and posteriorly.
Closure of the fissure is complete by the sixth week (13-mm stage).
Pathophysiology
In the normal eye, optic fissure closes 33 to 40 days after conception.
Failure of the embryonic fissure to close along the inferonasal aspect of the optic cup and stalk
That causes Retinal neurosensory elements and RPE
precursors fail to become confluent.
Due to which underlying choroid fails to differentiate That results in bridge of bare sclera or a cyst formation
Pathophysiology
Anteriorly defects in the neuroectodermally derived iris
pigment epithelium produce iris coloboma
PosteriorlyThe entire optic nerve head may be involved in a
colobomatous malformation
Typical/atypical
Colobomas are called typical if they are located inferonasally in the region of the fissure
Typical colobomas can involve the iris, ciliary body, choroid, or any of the three, and also may involve the optic nerve
Atypical colobomas are not related to closure of the fissure
Multi-system involvement A single-gene disorder
with multisystem involvement
Aicardi's syndromeLenz
microphthalmia syndrome
Meckel's syndromeWarburg's
syndrome
Aicardi's syndrome
Absence of corpus callousm
Consist of triad -Agenesis of the
corpus callosum infantile spasms.morning glory
syndrome
Multisystem disorder without known genetic cause
CHARGE association of anomalies
colobomatous Microphthalmos heart defects choanal atresia retarded growth genital anomalies ear anomalies or
deafness (At least three of
the features are necessary for the diagnosis)
Iris colobomaTotal if they involve a whole
sectorof the iris up to the
ciliarybody“keyhole” defectPartialif they do not involve awhole sector of the irismay appear as a notch
at thepupillary margin
Histological Complete coloboma
involves the whole thickness of the iris
Incomplete coloboma involves either the pigment epithelium or the
stroma
Bridge coloboma mesectodermal tissue forms a pupillary
membrane that stretches across the defect
Lens colobomaColoboma of the lens is not a true coloboma.
No lens tissue is missing
An absence of zonular fibers from an underlying colobomatous ciliary body
Results in a lack of tension on the lens capsule in that region
Notched equator/ Flattening of the inferior lens
Lens notches can occur wherever zonules are absent or deficient
zonular rupture during early surgery
Ida Manns classification(1937)Ida Manns classification(1937)
1-above the optic disc
2-superior border of optic disc
3-seperated from the optic disc by normal narrow area of retina
4-inferior crescent below the disc
5- isolated gap in the line of fissure
6-area of pigmentary disturbance
7-extreme peripheral coloboma
1)area of pigmentary disturbance
2) isolated gap in the line of fissure
3) above the optic disc
Retinal detachment in colobomaRetinal detachment in coloboma
40% develop RD , accounts for 0.5% of RD in
young.
May or may not be due to coloboma
Vitreous traction cause breaks outside coloboma
RD due to coloboma is break along edge of coloboma
It is difficult to visualise breaks because they are under edge or close to haemorrhage
Treatment modalitiesTreatment modalities
Cryo to anterior margin and photocoagulation to
posterior margin
Radial buckles (Patnaik et al,1961)-may extend
to disc if large.35-57% success rate
Management of RD with ColobomaManagement of RD with Coloboma
Prophylactic laser delimitation of the coloboma
margins
If RD is due to peripheral coloboma-conventional
scleral buckling surgery &Vitrectomy with
endophotocoagualation with silicon oil injection
Management of RD with ColobomaManagement of RD with Coloboma
Lensectomy may be required in cases of difficulty
in visualizing inferior retina
Breaks usually identified
AFE easily done as sclera is concave
Prolonged inferior tamponade needed-silicon oil \
gas.
SRNVM in retinochoroidal coloboma
Pathology-absence of choroid with breach in bruch’s membrane leading to vessels entering sub-retinal space.
Also RPE abnormalities stimulate budding of choriocapillaris endothelial cells.
Laser photocoagulation is advised modality of treatment.
Cataract in colobomatous eyes
Clinically significant cataract develops at a younger age compaired with age-related nuclear sclerotic cataract.
Cataract more likely to be denser.Cuniform opacities are more likely to
occur earlier.Increased no. of subluxated lens due to
associated zonuler deficiency
Michael L. Nordlund, Alan Sugar, Sayoko E. Moroi, J Cataract Refract Surg 2000; 26:1035-1040
Microophthalmos in colobomatous eyesPrevalence 21 per 100,000
82% at least >+7.00D of hypermetropia
Coloboma is the second MC association after cataract (22% v/s 44%)
Microophthalmos with coloboma may or may not be associated with microcornea
Mark J etalAetiology of severe visual impairment and blindness in MicroophthalmiaBJO 1994(78);332-334
Microophthalmos in colobomatous eyesA person with coloboma with microophthalmos
with microcornea has a poorer visual prognosis than a person with coloboma with microophthalmos without microcornea
Further a newborn with a corneal diameter<5mm has a very poor prognosis
Mark J etal Aetiology of severe visual
impairment and blindness in Microophthalmia BJO 1994(78);332-
334
Microcornea in colobomatous eyes
The term microcornea implies a corneal diameter of less than 10 mm.
It thought to occur secondary to an arrest in corneal growth after the fifth month of fetal development.
It often occurs with ocular abnormalities such as colobomata and microophthalmos may be present
Microcornea accompanies anterior microphthalmos, with crowding of the anterior segment structures
ManagementSystemic evaluationOcular examination.Investigations
Axial lengthKeratometryIOL MasterUSGUBM
Management Clinically significant cataract develops at a
younger age
If a coloboma involves the macula Axial length will be varied so earlier refraction will be important or Axial length may be obtained by locating the preferred fixation point
Coloboma with microophthalmos with microcornea –ECCE not a viable option
The crystalline lens has been reported to be of normal or slightly larger than normal size
#
Management
The lens:eye volume ratio is greater (10 to 32 percent) in these eyes compared with emmetropic eyes (3 to 4 percent)
So Phaco-emulsification / manual phaco (SICS) is a viable option
Phaco-emulsification—e.g. Slit Nucleotomy, Wooden boot, Petalloid etc.
Manual phaco (SICS) —e.g. Sandwich technique, Quarters technique, Phacotrisection etc.
Michael L. Nordlund, Alan Sugar, Sayoko E. Moroi, J Cataract Refract Surg 2000; 26:1035-
1040#
Management
Minimal mydriasis or reactive miosis should be anticipatedIris retractors / multiple sphicterotomies
CCC run-off or tear can occurRecommendations for CCC
Eccentric capsulorhexis Increased magnification with dye assistanceOblique illuminationTwo stage CCCGood chamber maintainence with viscoelasticNucleus sculpting / Nucleus cracking at opposite meridian + PCIOL@90° to
tearEndothelial losses
Shell technique can be used
Michael L. Nordlund, Alan Sugar, Sayoko E. Moroi, J Cataract Refract Surg 2000; 26:1035-
1040
#
Management Anterior vitrectomy
Vitreous loss –Prolapse through PC rentProlapse through colobomatous area without PC rent
Optimal centeration of the optic with the ectopic pupil to avoid post-op mono-ocular diplopia
Puppiloplasty may be required
Avoid silicon material IOLsAs future VR surgery may entail the use of silicon oil
# Michael L. Nordlund etalPhacoemulsification and intraocular lens placement in eyes with cataract and congenital coloboma: visual acuity and complicationsJ Cataract Refract Surg 2000; 26:1035-1040
PrognosisThe prognosis for vision depended on the
phenotype of the better eye Microphthalmos with cyst has the worst prognosis Coloboma with microcornea and microphthalmos a poor
prognosis Coloboma with only microcornea has an intermediate
prognosis Simple coloboma has the best prognosis
A corneal diameter <6 mm had a poor visual prognosis whereas a corneal diameter >10 mm had a good prognosis
Time of surgeryType of surgery
Hornby SJ, etal Ophthalmology. 2000 Mar;107(3):511-20Visual acuity in children with coloboma
Michael L. Nordlund, Alan Sugar, Sayoko E. Moroi, J Cataract Refract Surg 2000; 26:1035-1040