Latanoprost-induced iris darkening: a morphometric study of human peripheral iridectomies.
OBJECTIVE
This microscopic study was undertaken to compare the melanocytes of peripheral iridectomy specimens from two eyes that had latanoprost-induced iris darkening (LIID) with iridectomies taken from the fellow untreated eyes.


METHODS
The two patients in this study were the ones who underwent LIID in the latanoprost treated eye from a series of 17 patients requiring bilateral trabeculectomy. The first trabeculectomy procedure provided a control peripheral iridectomy for each patient, whereas the second eye was treated with once daily 50 microg ml(-1) latanoprost drops for 6 months. The four peripheral iridectomy specimens from the two LIID patients were subjected to quantitative morphometric analysis by light microscopy of iris cellularity, and electron microscopy of iris melanocyte immature melanosomes and mature melanin granules.


RESULTS
There was no significant difference in stromal cellularity between the LIIDs and their respective controls nor were there significant differences in the numbers of immature melanosomes or melanin granules in the melanocytes. However, there was a significant increase in the diameter of melanin granules that was more pronounced in the anterior border layer than the deeper stroma. With the anterior border melanocytes, the increase in melanin granule size was associated with significant increases in granule area and the percentage of cell cytoplasm occupied by melanin (granularity).


CONCLUSIONS
The only morphological change identified in two peripheral iridectomies that had LIID when compared to untreated fellow eye specimens was a modest increase in the size of stromal melanocyte melanin granules that was more pronounced in the cells of the anterior border region.
Cracknell
Kathryn P B
KP
St Paul's Unit of Ophthalmology, Department of Medicine, Royal Liverpool University Hospital, Liverpool L69 3GA, UK.
Grierson
Ian
I
Hogg
Penny
P
Appleton
Paul
P
Pfeiffer
Norbert
N
D000959:Antihypertensive Agents; D017889:Exfoliation Syndrome / Q000473:pathology / Q000601:surgery; D005902:Glaucoma, Open-Angle / Q000473:pathology / Q000601:surgery; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D032801:Iridectomy; D007498:Iris / Q000473:pathology; D007499:Iris Diseases / Q000473:pathology* / Q000601:surgery; D000077338:Latanoprost; D008543:Melanins / Q000032:analysis; D008544:Melanocytes / Q000473:pathology; D020460:Melanosomes / Q000473:pathology; D008854:Microscopy, Electron / Q000379:methods; D010859:Pigmentation Disorders / Q000473:pathology* / Q000601:surgery; D011461:Prostaglandins F, Synthetic; D017154:Stromal Cells / Q000473:pathology; D014130:Trabeculectomy
D000959:Antihypertensive Agents; D008543:Melanins; D011461:Prostaglandins F, Synthetic; D000077338:Latanoprost