The Pigment Dispersion Syndrome (PDS) and the Pigmentary Glaucoma (PG) are characterized by loss of pigment from the posterior surface of the iris in the mid-periphery and nearly always both eyes are affected, although asymmetry of involvement maybe present. The released pigment is deposited on intraocular structures such as the cornea endothelium forming the Kruckenberg spindle, the anterior surface of the iris stroma, the anterior and posterior lens surface at the zonular attachments, and of course the anterior chamber angle and the trabecular meshwork.
Pigmentary glaucoma (and PDS) is more common in men than women and typically affects young myopic men 20 - 45 years of age. A typical case of Pigmentary Glaucoma is presented.
It must be noted that PDS without elevated IOP can occur and such patients are being followed as "pigmentary glaucoma suspects". Tonography may be of prognostic value revealing those patients at greater risk for future glaucoma development.
The diagnosis of pigmentary glaucoma will be based on the following:
- Kruckenberg Spindle:
A corneal endothelium pigmentation that is usually the first clue to the disease. The aqueous currents deposit the pigment on the endothelium, which later phagocytizes the pigment. It is not a pathognomonic sign for PDS or PG and it can be seen also in exfoliation or in healthy myopic patients.
- Iris transillumination defects:
They are slit-like, radial defects, in the mid periphery of the iris and for many physicians are considered as the pathognomonic sign for PDS or PG. And indeed, in the absence of this finding it is difficult to make a definite diagnosis of PDS or PG. This typical transillumination pattern can be seen using a fiberoptic transilluminator or slit-lamp examination. In the case reported the defects are more prominent in the left eye of the patient than in the right eye.
- Trabecular pigmentation:
The most essential feature in the anterior chamber angle is a dark-colored pigment band at the filtration portion of the trabecular meshwork around the whole circumference of the angle.
- Elevated IOP:
Another characteristic of PG is that the level of IOP is subject to wide fluctuations. The pigment particles in the aqueous humor may increase rapidly, spontaneously, or as a result of exercise or mydriasis, causing acute IOP rises called "pigment storms".
Ultrasound Biomicroscopy (UBM, Humphrey Instruments Inc) with a resolution of 50 microns, reveals the anatomy of the anterior segment and it can be very useful in demonstrating the prominent peripheral iris concavity seen in PG and PDS.
In the differential diagnosis of PG, one should consider the following conditions:
- Exfoliation Glaucoma:
It must be noted that there is also a possibility of coexistence of PDS or PG and exfoliation syndrome or glaucoma.
- Uveitic glaucoma:
Pigment particles circulating in the aqueous humor may be mistaken for inflammatory cells and the glaucoma can then be erroneously attributed to uveitis, or glaucomatocyclic crisis (Possner Schlossman Syndrome).
- Elderly people:
Pigment in various amounts in the angle is a common finding in the elderly.
- Malignant melanoma
of the anterior uvea tract causing melanomalytic glaucoma. As mentioned before PG aRGEnd PDS are almost always bilateral.
None of these conditions produce the characteristic slit-like transillumination pattern of iris mid-periphery, observed in PG or PDS.
In evaluating patients response to medical treatment keep in mind that the IOP in PG is subject to large fluctuations, particularly in younger individuals. Also keep in mind that there are patients with PDS who do not have elevated IOP and they dont need to be treated.
Another fact is that eyes with PG can show spontaneous improvement in IOP control with time, and medications can be reduced or even discontinued. The iris transillumination defects may also decrease or disappear probably by adjacent cells migration.
Robert Ritch described a "pigment reversal sign", when the trabecular meshwork begins to recover and the normal pigment pattern reverses, so that the pigment band bocomes darker superiorly rather than inferiorly in the angle.
Because the patients with PG are usually young and myopic, as in the case presented, the use of miotics may cause spasm of accommodation and blurring of vision. However, pilocarpine Ocuserts are often well tolerated.
Another solution to this problem is to use low concentration of pilocarpine (e.g. pilocarpine 1%) once daily or two to three times weekly, in the evening. The concept is to keep the pupil in constriction (miosis) and to eliminate the iris concavity, responsible for the release of pigment. Such a treatment we applied to the left eye of the patient presented. Ultrasound biomicroscopy of patients left eye, before and after miotic treatment, shows a more convex iris configuration after treatment. Patients IOP after treatment was 14 - 19 mmHg.
Laser Treatment
Karichoff and Campell have observed that the concave iris contour present in PG reverts to a planar configuration after laser iridectomy, probably eliminating the reverse pupilary block mechanism. Such a treatment we applied to the right eye of the patient presented. Ultrasound biomicroscopy before and after laser iridectomy of patients right eye shows an almost planar iris configuration after treatment. Patients IOP though, remained at the high twenties after treatment, confirming the opinion that it is not yet appropriate to apply laser iridectomy as a treatment in PG.
Laser trabeculoplasty can often produce dramatic IOP lowering in PG, but the results are less stable and it is possible that patients with PG eventually exhibit acute and prolonged IOP rise.
Glaucoma
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Page Created: 03/02/2002, Updated: 26/10/2002