lenticular abnormalities

LENTICULAR ABNORMALITIES

OPTOM FASLU MUHAMMED

Shape abnormalities

a. Anterior lenticonusb. Posterior lenticonusc. Microspherophakiad. Coloboma of the lens

The surface capsule in the pupillary zone with the underlying cortical fibres exhibit spherical or conoid transformation

Anterior lenticonus

Predominantly affect boys often bilaterally

There may be associated systemic anomalies - alport's syndrome

Posterior lenticonus

Seen in girls as solitary unilateral condition

It may be seen associated with Lowe's syndrom

The oil globule reflex in the pupillary area is the main clinical feature.

The site of the cone shows a thin basement membrane (capsule)

Decrease in nucleated cells in the anterior form

Posterior cone is composed of abnormally nucleated cells (which are generally absent)

Microspherophakia

In this condition, the lens is spherical in shape (instead of normal biconvex) and small in size.

Microspherophakia may occur as an isolated familial condition or as a feature of other syndromes e.g., Weil-Marchesani or Marfan’s syndrome.

Coloboma of the lens

It is seen as a notch in the lower quadrant of the equator .

It is usually unilateral and often hereditary

Transparency abnormalities

a. Flecksb. Vacuolesc. Opacification (cataract) - Primary - secondary

Flecks

Focal lenticular opacification occurs due to adhesion of pupillary membrane anteriorly and hyaloid vessel posteriorly.

The are sub capsular or superficial cortical.

Vacuoles

Vacuoles of different sizes may appear in sub capsular or cortical zones.

They represents hydropic degenerator.

A number of agents, metabolic chemical may produce vacuolar change.

Cataract

Morphological classification 1. Capsular cataract. It involves the

capsule and may be: i. Anterior capsular cataract ii. Posterior capsular cataract 2. Sub capsular cataract. It involves the

superficial part of the cortex (just below the capsule) and includes:

iii. Anterior sub capsular cataractiv. Posterior sub capsular cataract

3. Cortical cataract. It involves the major part of the cortex.

4. Supranuclear cataract. It involves only the deeper parts of cortex (just outside the nucleus).

5. Nuclear cataract. It involves the nucleus of the crystalline lens

6. Polar cataract. It involves the capsule and superficial part of the cortex in the polar region only and may be:

i. Anterior polar cataract ii. Posterior polar cataract

Polar cataract

The cataracts are often stationary Attenuation or loss of epithelial cells

followed by fibrous metaplasia of sub capsular region.

New epithelial cell may be laid down underneath the fibrous plaque.

Senile cataract

The cataract developing elderly is called senile cataract.

They are idiopathic in nature These are account for 55% of

curable blindness in india

Clinical recognisable forms of senile cataract

1. Cortical (soft cataract)2. Nuclear (hard cataract)

There is fibre fragmentation , loss of epithelial cells and disturbance in the epithelial configuration noticed in the bow region.

Hypermature cataract show vacuolation.

Associated nuclear alteration such as pigmentation and hardening.

Stages of maturation

[A] Maturation of the cortical type of senile

Cataract1. Stage of lamellar separation. The earliest senile change is demarcation of

cortical fibres owing to their separation by fluid.

This phenomenon of lamellar separation can be demonstrated by slit-lamp examination only.

These changes are reversible.

2. Stage of incipient cataract. In this stage early detectable

opacities with clear areas between them are seen.

Two distinct types of senile cortical cataracts can be recognised at this stage:

(a) Cuneiform senile cortical cataract It is characterised by wedge-shaped

opacities with clear areas in between. These extend from equator towards centre

and in early stages can only be demonstrated after dilatation of the pupil.

They are first seen in the lower nasal quadrant.

These opacities are present both in anterior and posterior cortex and their apices slowly progress towards the pupil.

On oblique illumination these present a typical radial spoke-like pattern of greyish white opacities .

On distant direct ophthalmoscopy, these opacities appear as dark lines against the red fundal glow.

Since the cuneiform cataract starts at periphery and extends centrally, the visual disturbances are noted at a comparatively late stage.

(b) Cupuliform senile cortical cataract a saucershaped opacity develops just below

the capsule usually in the central part of posterior cortex (posterior subcapsular cataract), which gradually extends outwards.

There is usually a definite demarcation between the cataract and the surrounding clear cortex.

Cupuliform cataract lies right in the pathway of the axial rays and thus causes an early loss of visual acuity.

3. Immature senile cataract (ISC). In this stage, opacification progresses further. The cuneiform or cupuliform patterns can be

recognised till the advanced stage of ISC when opacification becomes more diffuse and irregular.

The lens appears greyish white but clear cortex is still present and so iris shadow is visible.

In some patients, at this stage, lens may become swollen due to continued hydration. This condition is called ‘intumescent cataract'.

Intumescence may persist even in the next stage of maturation.

Due to swollen lens anterior chamber becomes shallow.

4. Mature senile cataract (MSC). In this stage ,opacification becomes

complete, i.e., whole of the cortex is involved.

Lens becomes pearly white in colour.

Such a cataract is also labelled as ‘ripe cataract’

5. Hypermature senile cataract (HMSC).

When the mature cataract is left in situ, the stage of hypermaturity sets in.

The hypermature cataract may occur in any of the two forms:

(a) Morgagnian hypermature cataract: In some patients, after maturity the whole

cortex liquefies and the lens is converted into a bag of milky fluid.

The small brownish nucleus settles at the bottom, altering its position with change in the position of the head. Such a cataract is called Morgagnian cataract.

Sometimes in this stage, calcium deposits may also be seen on the lens capsule.

(b) Sclerotic type hypermature cataract: Sometimes after the stage of maturity, the

cortex becomes disintegrated and the lens becomes shrunken due to leakage of water.

The anterior capsule is wrinkled and thickened due to proliferation of anterior cells and a dense white capsular cataract may be formed in the pupillary area.

Due to shrinkage of lens, anterior chamber becomes deep and iris becomes tremulous (iridodonesis).

[B] Maturation of nuclear senile cataract

In it, the sclerotic process renders the lens inelastic and hard, decreases its ability to accommodate and obstructs the light rays.

These changes begin centrally and slowly spread peripherally almost up to the capsule when it becomes mature;

however, a very thin layer of clear cortex may remain unaffected.

The nucleus may become diffusely cloudy (greyish) or tinted (yellow to black) due to deposition of pigments.

In practice, the commonly observed pigmented nuclear cataracts are either amber, brown (cataracta brunescens) or black (cataracta nigra) and rarely reddish (cataracta rubra) in colour.

Secondary cataracts

Lenticular opacification following an intraocular inflammation or neoplasm.

The anatomical site of lens damage is based on the location of primary disease process.

Anterior segment disorder such as uveitis produce anterior cataract

Vitreo retinitis or melanoma affects posterior lens.

Complications of cataract1. Phacoanaphylactic uveitis. A hypermature cataract may leak

lens proteins into anterior chamber. These proteins may act as antigens

and induce antigen antibody reaction leading to uveitis.

2. Lens-induced glaucoma. It may occur by different

mechanisms e.g., due to intumescent lens (phacomorphic glaucoma) and

leakage of proteins into the anterior chamber from a hypermature cataract (phacolytic glaucoma).

3. Subluxation or dislocation of lens.

It may occur due to degeneration of zonules in hypermature stage.

Basement membrane abnormalities Lenticular capsule is thin basement

membrane of underlying epithelial cells. It is the thickest one in the body, elastic

in character and resist entry bacteria or any particulate matter.

1. Thinning2. Thickening3. Exfoliation - true - pseudo

Thinning

It may occur in mature cataracts

Thickening

It may occur focally or diffusely. Diffuse basement membrane

thickening, as an ageing process, may accompany senile cataract.

Focal thickening is noticed in lowe’s syndrome (oculo cerebral renal syndrome).

Exfoliation

They are of two types1. True exfoliation It is rare and occurs due to laminar

separation of capsule , which scrolls over anterior surafce.

The disease may be related to infrared exposure

2.Pseudo exfoliation It is a disease characterised by

deposition of white fluffy dandruff-like material over anterior surface of lens, iris, zonules, etc.

Biochemically , it is glycoprotein with sialo and oligosaccharide side chains.

The disease occurs in 50-60 yr old individuals with involvement of both eyes in over 50% cases.

The material in 5-10% cases is known to affect outflow channels leading to ocular hypertension.

Ultrastructurally , it is filamentous in nature similar to basement membrane.

Zonular abnormalities

Displacement of the lens from its normal position (in patellar fossa) results from partial or complete rupture of the lens zonules.

Topographically, displacements of the lens may be classified as subluxation and luxation or dislocation.

I. Subluxation It is partial displacement in which

lens is moved sideways (up, down, medially or laterally), but remains behind the pupil.

It results from partial rupture or unequal stretching of the zonules.

II. Dislocation or luxation of the lens In it all the zonules are severed from the

lens. A dislocated lens may be incarcerated

into the pupil or present in the anterior chamber , the vitreous (where it may be floating – lens nutans; or fixed to retina – lens fixata), sub-retinal space, subscleral space or extruded out of the globe, partially or completely.

Congenital displacements(a) Simple ectopia lentis In this condition displacement is

bilaterally symmetrical and usually upwards.

It is transmitted by autosomal dominant inheritance.

(b) Ectopia lentis et pupillae It is characterised by displacement

of the lens associated with slit-shaped pupil which is displaced in the opposite direction.

Other associations may be cataract, glaucoma and retinal detachment.

(c) Ectopia lentis with systemic anomalies

1. Marfan’s syndrome2. Homocystinuria3. Weil-Marchesani syndrome

Marfan’s syndrome

Mesodermal dysplasia with several ocular cardiovascular anomalies characterises marfan’s syndrome.

The disorder is autosomal dominant with metabolic abnormality related to collagen synthesis.

The ocular lesions include iris hypo -pigmentation,subluxation of lens.

In this condition lens is displaced upwards and temporally (bilaterally symmetrical).

Homocystinuria

It is an autosomal recessive,inborn error of metabolism.

Absence or deficiency cystathionine synthetase which results in increase in homocystine.

The abnormality associated with formation of short segment of zonules and PAS positive material accumulation over ciliary epithelium.

In it the lens is usually subluxated downwards and nasally.

Weil-Marchesani syndrome

It is condition of autosomal recessive mesodermal dysplasia.

Ocular features are spherophakia, and forward subluxation of lens which may cause pupil block glaucoma.

The eye may also be myopic.