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

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# 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

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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

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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