Pigment Dispersion Syndrome/Pigmentary GlaucomaDr shylesh B dabkeGlaucoma Fellow Aravind Eye hospital

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OverviewPigment Dispersion syndrome(PDS)Abnormal amount of pigments are liberated from posterior surface of iris, which are deposited throughout the anterior and posterior chamber of the eye.

Pigmentory GalucomaA type of secondary open glaucoma that develops among patients with PDS.

HistoryIn 1940, Sugar briefly described one such case with pigment dispersion and glaucoma.(1)

In 1949 - Sugar and Barbour(2) - Reported details of this entity- Referred this condition as Pigmentary Glaucoma1.Sugar HS. Concerning the chamber angle. I. Gonioscopy. Am J Ophthalmol 1940;23:853-866.2. Sugar HS, Barbour FA. Pigmentary glaucoma: a rare clinical entity. Am J Ophthalmol. 1949;32(1):90-92.

EpidemologyCorresponds to 1-1.5% of all Glaucoma.Onset < 40yrsMale : Female 2:1More frequent in whitesStrong association between Pigmentary Glaucoma and Myopia.

Young White Myopic Male

Usually BilateralNo typical Hereditary Pattern SporadicSignificant linkage between disease phenotype and genetic markers located on 7q 35-36.Probability of PDS converting to PG* 10% in 5 years15% in 15 years* Siddiqui Y.,Hulzen R.D.T.,Cameron J.D.,et al:What is the risk of developing pigmentary glaucoma from pigment dispersion syndrome?. Am J Ophthalmol2003;135:794-799

However autosomal dominant and autosomal recessive patterns are also reported6

PathogenesisAnatomical Predisposition

- Myopia- Deep AC- Posterior insertion of iris into ciliary body

- Mechanical abrasion theory

- Abioptrophy theory

Pathophysiology

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Mechanical Abrasion TheoryD G Campbell This theory is based on finding of slit like trans illumination defect on iris.

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Slit like trans illumination defect

Mechanical rubbing between anterior packets of lens zonules & posterior iris in predisposed eyes

Cause of pigment dispersion.

This finding led to 9

PDS and MyopiaThis association can be explained with mechanical abrasion theory.

Myopic eyes tend to have a slightly concave iris that potentially could press against the zonulesAlthough myopia could explain some cases of pigment dispersion syndrome, it is insufficient in explaining all instances. Not everyone with myopia has PDS, and not everyone with PDS hasmyopia10

PDS and reverse pupillary blockSecond & complementary explanation for iris concavity.

In reverse pupillary block, pressure in the anterior chamber of the eye exceeds that of the posterior chamber. The increased pressure forces the iris over the lens, where it acts like a ball valve in the pupillary opening, preventing the return of aqueous humor to the posterior chamber. As pressure continues to increase, it causes a backward bowing of the iris that accentuates contact between it and the Zonules of Zinn.In normal eyes iris zonular contact is rare11

PDS and BlinkingCampbell proposed blinking initially deforms the cornea

Pushing iris against zonules

Transient increase in IOP

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PDS and AccommodationAccommodation in patients with PDS increased posterior bowing of iris

Forward movement of lens increasing pressure in anterior chamber

Iridotomy abolishes this change13

Abiotrophy TheoryPremature degeneration of cells or tissue, especially when it is due to genetic defect

While mechanical abrasion theory explains several clinical features of pigment dispersion syndrome, key gaps in knowledge still remain.

Cellular degeneration is supported in pigment dispersion syndrome by two lines of evidence.

Primary among these is that liberation of iris pigment can occur in eyes that are not myopic and for which there is little or no evidence of zonule abrasion. For this reason, thinking about PDS has expanded to include the abiotrophy theory.14

Heritable ComponentThere appears to be a clustering of PDS cases in a subset of families

GPDS1has been mapped to chromosome 7

Dominant inheritance pattern

Other gene candidates currently are being investigated.

Microscopic examination of iris tissueWithin tissue disruptions throughout the iris

Pigment-containing cells called melanocyteseither are missing or have ruptured membranes from which pigment extrudes.

Mechanical Abrasion Theory

Abiotrophy Theory

PDSEvidence appears to be mounting that the two represent two distinct disease processes that have a common endpoint of pigment dispersion.

Once pigment is liberated from the iris, it is carried throughout the anterior chamber and is deposited in multiple locations.

Clinical FeaturesEarly - AsymptomaticEpisodes of pain/blurred visionwith haloes following strenuous exerciseAdvanced Loss of central visionLater - Loss of peripheral vision

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SignsCornea Krunkenberg Spindle*Ant Chamber-Deep-Posterior bowing of peripheral iris-Pigments in AC

Iris Slit like/Spoke like transillumination defect*

Doesnt impair vision, doesnt damage corneal endotheliumDifficult to see in dark thick iris stromaInfrared video graphic technique have been developed for TID

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Infrared Videography Technique

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Fine surface pigment granules that may extend onto the lensPartial loss of pupillary ruff (frill)

HeterochromiaAnisocoria

Pigment granule dispersion on iris stroma may make iris progressively darker creating heterochromia in asymmetric cases.Anisocoria Iris with more transillumination defect will have a dilated pupilThe iris heterochromia and anisocoria of PDS may mimic Horner syndrome 22

Gonioscopy - Wide open angle - Mid peripheral iris concavity* - Trabecular hyperpigmentationLens- Annular ring of pigment on posterior lens surfaceScheie Strip/Zentamayer Ring*Fundus- Retinal Breaks & Lattice degeneration(20%)- Retinal detachment (6-7%)

This is particularly useful in black patients as transillumination defects and Trabecular pigmentation in black patients may be misleading23

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Classic Clinical TriadKrukenberg SpindleDense trabecular pigmentationMidperipheral iris transillumination defects

Differential DiagnosisExfoliation Syndrome

Uveitis

Pigment dispersion with PCIOL

POAG

Pigmented Tumors

Other conditions with pigment dispersionAcute angle closure glaucoma

Rhegmatogenous RD

Ocular Haemorrhage

Trauma(Surgical/nonsurgical)

Conditions with iris trans-illumination defectsAlbunism

PDS vs Pseudoexfoliation syndromeTrans-illumination defectTM Pigmenta- tionAgeGranular deposits

InvestigationUBM Posterior iris insertion Iris concavity Iridozonular contact

MedicalMioticsPhysical activityLaser Trabeculoplasty

TreatmentSimilar to POAG

Rx typically begins with medical therapy

All ocular hypotensive medications are effective

PG Analogues are drug of choice*Theoretically of benefit

Decreases iridozonular contact

Facilitates aqueous outflow

Disadvantage Exacerbation of myopia Precipitate RD in Myopia Not well tolerated by young patientsAlfa adrenergic antagonist thymoxamine produces miosis without cyclotropiaExercise increases pigment dispersion and causes IOP spike*

If significant pressure rise is observed, 0.5% Pilocarpine during exercise may be beneficialHeavy trabecular pigmentation allows increased absorption of laser energy

In turn allowing lower energy level for trabeculoplasty

Starting with 300mW per spot if using ALT and 0.4mJ per spot if using SLT

Ritch et al reported 80% success rate at 1yr followup

Trabeculoplasty responds well initially but IOP control tends to decline wit time and surgery is in effective in patients who are older or who had glaucoma for a long time

With hypotensive medication though IOP will be controlled, mechanism of continued pigment dispersion is not eliminated31

Laser IridotomyTrabeculectomy

Theoretical effects - Relives the reverse pressure gradient- Relieves posterior bowing of peripheral iris- Relieves rubbing- Reduces liberation of pigment- Allows meshwork to clear pigment & recover normal outflow function(if changes are not already irreversible) When medical therapy and laser trabeculoplasty have failed to adequately control IOPFiltration surgery is usually successfulUse of adjunctive antimetabolites may improve surgical outcomeHigher percentage of patients with pigmentary glaucoma than POAG and men appear to require it at a earlier stage.Success rates are similar to POAG.Trabeculectomy in young myopic patients warrants extra care - prone for Hypotony Maculopathy

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Temporal Evolution of PDSTransillumination defect may disappearIOP may return to normalTrabecular pigmentation may decreasePigment reversal signburnt out

With age pupil becomes small & lens becomes thickerDecreased iridozonular contactDecreased dispersionOccasionally glaucoma may Burn Out

Look carefully for PDS/PG in patients who present as Normal Tension Glaucoma

Look for Pigment Reversal

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