Latanoprost-induced iris heterochromia and open-angle glaucoma: a clinicopathologic report

[Latanoprost in hypotensive therapy of glaucoma]

The review presents an analysis of therapeutic effectiveness, safety and pharmacokinetics of latanoprost - the reference representative of the prostaglandin group, summarizes the experience of its clinical use in glaucoma as monotherapy and in combination with antihypertensive drugs of other pharmacological groups, its possible effect on the inflammatory process in the anterior segment of the eye, as well as its probable participation in the development of macular edema. The article also gives a recount of relevant local and systemic adverse events.

Anterior Segment Optical Coherence Tomography Analysis of Iris Morphometric Changes Induced by Prostaglandin Analogues Treatment in Patients with Primary Open Angle Glaucoma or Ocular Hypertension

Background:

The study aimed to evaluate iris thickness changes in patients with Primary Open Angle Glaucoma (POAG) or Ocular Hypertension (OHT) under treatment with Prostaglandin Analogues (PG).

Objectives:

Primary outcome measures were iris thickness at the region of Dilator Muscle Region (DMR) and Sphincter Muscle Region (SMR). DMR/SMR ratio was also evaluated. The secondary outcome was the correlation between PG treatment length and iris parameters.

Methods:

The charts of patients with POAG or OHT who underwent Visante OCT were retrospectively selected. The patients were divided in a group using PG for at least 6 months and a group using hypotensive drops not including PG or alpha-adrenergic agonists. A third group included healthy subjects.

Result:

98 subjects were selected. Patients with POAG or OHT using PG eyedrops showed a significant iris thickness reduction at DMR compared to healthy subjects and to patients using hypotensive eyedrops not containing PG. Significantly higher SMR thickness values were found in PG group compared to both control groups. DMR/SMR ratio significantly reduced in PG group. No correlation was found between PG treatment length and iris parameters.

Conclusion:

The present data indicate that PG treatment induced DMR thickness reduction and an increase in SMR thickness. These changes were not related to the duration of PG exposure.

Characterization of prostaglandin F2α receptors in human eyelids

PURPOSE

Elongation, thickening, and crowding of eyelashes are commonly seen after topical use of prostaglandin analog eyedrops for glaucoma treatment. The purpose of this study was to demonstrate the presence and characterize the location of prostaglandin analog F2α receptors (PGF2α) in human hair follicles.

METHODS

In this observational clinical laboratory study, excised eyelid specimens following eyelid surgery were studied. Resected portions of eyelids were submitted for histopathologic evaluation. For immunohistochemistry evaluation, a polyclonal antibody directed against PGF2α was purchased from Cayman Chemical. The staining procedure was carried out on an automatic stainer.

RESULTS

Out of 26 patients recruited, final analysis was conducted on 17 eyes of 15 patients. There were 10 men and 5 women (mean age 77 ± 14 years). Staining was detected only in hair follicles in the anagen stage (37 slices). No variation in pattern, distribution, or intensity of immunostaining was noted among sections of different individuals. Only the bulb and stem of the hair follicle stained positive. In the bulb, the strongest staining occurred in the matricular cells and in the inner sheath layer. In the stem, the strongest staining occurred in the Huxley layer of the inner sheath.

CONCLUSIONS

This immunohistologic study found that PGF2α receptors were located predominantly in the inner root sheath of the bulb and stem of eyelashes and expressed only in eyelashes in the anagen phase.

A review of the use of latanoprost for glaucoma since its launch

INTRODUCTION

Prostaglandins are increasingly used as first choice treatment for glaucoma because they are highly effective, lack relevant systemic side effects and require just once-daily administration. Latanoprost is an ester prodrug analog of prostaglandin F2α, which reduces intraocular pressure (IOP) by increasing uveoscleral outflow. Latanoprost 0.005% has received European and US approval as the first-line drug for reducing IOP in patients with open-angle glaucoma or ocular hypertension. Following the recent patent expiry for Xalatan®, a number of latanoprost generics have entered the glaucoma market.

AREAS COVERED

This review, achieved through PubMed and Medline research methods, describes the composition, pharmacokinetics, mode of action, efficacy, side effects and safety profile of latanoprost.

EXPERT OPINION

Latanoprost was the first prostaglandin analog introduced in glaucoma management and it dramatically changed the market of the disease thanks to its efficacy and safety. Conjunctival hyperemia, which is commonly found after latanoprost use, is associated with a minor efficacy and duration of trabeculectomy; yet, from the ophthalmologist's perspective, this side effect seems largely counterbalanced by the high efficacy and safety of this compound. It is always advisable to consider the pro-inflammatory mode of action of latanoprost because this may have negative effects in particular patients (i.e., those with uveitis and cystoid macular edema) for whom caution and close follow-up is necessary.

Prostaglandin efficacy and safety study undertaken by race (the PRESSURE study)

PURPOSE

Latanoprost, travoprost, and bimatoprost are prostaglandin or prostamide-type ocular hypotensive medications, all of which are effective and safe for lowering intraocular pressure (IOP). Most studies with these types of drugs have included patients mainly from European or white ethnic backgrounds; however, some reports have suggested that there is a difference in response between patients of white and African racial heritage. On account of the possibility that drugs may act differently in people of different ethnic background, we decided to study the effectiveness and safety of all 3 drugs in people from various ethnic heritages. Our hypothesis was that there might be a possible ethnic-based difference in IOP-lowering effectiveness between the 3 medications.

METHOD

This was a prospective randomized investigator-masked multicenter study. Patients newly diagnosed with open-angle glaucoma (primary, pseudoexfoliative, or pigmentary), or whose pressure became elevated after a washout period, were randomized to receive 1 of 3 prostaglandin/prostamide drugs. Assignment of drug was balanced by racial group and study site, and the investigator was masked to the drug used. The patients were requested to self-identify their racial group as White, African, East Indian, Asian, or Hispanic; to minimize the possibility of heterogeneity, all 4 grandparents had to be known to originate from the same group. However, for purposes of analysis, the patients were divided into 2 groups--White or Other. Patients were followed at 2, 6, 12, and 24 weeks; IOP and local side effects were assessed at each visit.

RESULTS

Eighty-three patients were recruited from 9 sites. The mean age of the patients was 61.5 ± 10.5 years. There were no differences in mean age or the distribution of sex between the patients whether examined by the 2 racial groups or the 3 drug groups. There was a highly statistically significant decrease in IOP from baseline to 12 weeks and from baseline to 24 weeks (F = 439.3, P<0.0001; F = 305.94, P<0.0001). There were no differences in treatment effect between the 3 drugs or between the 2 ethnic groups, (P > 0.05 for all comparisons) and there was no interaction between race and drug.

CONCLUSIONS

All 3 prostaglandin/amide drugs are highly effective at lowering IOP. No differences in effect between the drugs or between members of different racial groups were detected, although the study sample size was too small to be certain to detect differences, if they existed.

Latanoprost in pediatric glaucoma--pediatric exposure over a decade

BACKGROUND

Although numerous studies of latanoprost in adult glaucoma have shown it to be an effective hypotensive agent with a low incidence of side effects, these issues have not been well studied in pediatric glaucomas. The purpose of the current study is to evaluate the safety and intraocular pressure (IOP) lowering effect of latanoprost in various pediatric glaucomas over a long period.

SUBJECTS AND METHODS

This retrospective study included all children treated with latanoprost at our institution from 1996 to 2007. Demographic, glaucoma-related, and side-effect information was recorded for each subject. Duration of latanoprost exposure was calculated in child-months (1 child exposed for 1 month). If interpretable IOP data were available, the presence or absence of a treatment response (IOP reduction > or =15% from baseline) was determined for each subject.

RESULTS

A total of 115 subjects with latanoprost exposure were identified, with a collective exposure of 2,325 child-months. Exposure for > or =1 year occurred in 52 subjects. Side effects were mild and infrequently reported. Of the 115 subjects, 63 had interpretable IOP data, and 22 (35%) were treatment responders. Predictors of a response included a diagnosis of juvenile open-angle glaucoma, monotherapy, and older age.

CONCLUSIONS

This large study of latanoprost-treated children confirms the excellent safety profile of the drug in the treatment of pediatric glaucoma. The study also confirms latanoprost's IOP-lowering ability in older children with juvenile open-angle glaucoma and in some children with aphakic glaucoma. Prospective studies are needed to better define the optimal role of latanoprost in the treatment of pediatric glaucoma, especially congenital glaucoma.

Side effects associated with prostaglandin analog therapy

Topical prostaglandin analogs, which have become first-line therapy in the medical management of glaucoma, have an excellent safety profile with regard to systemic side effects, but are associated with several ocular side effects. Some of these are common, with no apparent serious consequences other than cosmetic, whereas others are much less common but represent potentially sight-threatening side effects. The former group includes conjunctival hyperemia, elongation and darkening of eyelashes, induced iris darkening, and periocular skin pigmentation. The latter group of side effects, which are relatively rare and lack definitive causal relationship to prostaglandin analog therapy, includes iris cysts, cystoid macular edema, anterior uveitis, and reactivation of herpes simplex keratitis. Most of the literature regarding side effects associated with prostaglandin analogs involves the use of latanoprost, probably because it was the first to be studied. There is no evidence, however, aside from less conjunctival hyperemia with latanoprost, that the commercially available prostaglandin analogs differ significantly with regard to side effects.

A study of histopathological features of latanoprost-treated irides with or without darkening compared with non-latanoprost-treated irides

OBJECTIVES

To study the histopathological features of latanoprost-treated irides with or without darkening, compared with non-latanoprost-treated irides.

METHODS

Iridectomy specimens and patient history forms were independently examined by 3 ophthalmic pathologists in a masked fashion. Specimens were evaluated for premalignant changes and for differences in level of pigmentation and degrees of cellularity, inflammation, and vascular abnormalities.

RESULTS

The specimens consisted of 22 latanoprost-treated darkened irides, 35 latanoprost-treated irides without darkening, and 35 non-latanoprost-treated irides. There was a statistically significant decrease in the number of nuclear invaginations and prominent nucleoli in latanoprost-treated darkened irides compared with the other 2 groups (P = .004 and P = .005, respectively). The average thickness and pigmentation of the anterior border layer was greater in the latanoprost-treated darkened irides than in the other 2 groups (P = .03 and P = .02, respectively). The latanoprost-treated darkened irides had increased pigmentation of the stroma (P < .001), stromal fibroblasts (P < .001), melanocytes (P = .005), vascular endothelium (P = .02), and adventitia (P < .001) relative to the other 2 groups.

CONCLUSIONS

There is no histopathological evidence of premalignant changes in latanoprost-treated darkened irides. The latanoprost-induced iris color changes are due to a thickening of the anterior border layer and an increased amount of melanin in the anterior border layer and within the stromal melanocytes.

Incidence of a latanoprost-induced increase in iris pigmentation in Japanese eyes

PURPOSE

To prospectively determine the incidence of a latanoprost-induced increase in iris pigmentation in Japanese brown iris eyes by identifying changes in iris pigmentation on a series of iris color photographs.

METHODS

In a cohort study, we prospectively and consecutively enrolled 104 patients (104 eyes) with primary open-angle glaucoma or normal-tension glaucoma who began treatment with latanoprost eye drops for the first time. None of the enrolled patients had a history of previous intraocular surgery or laser surgery. Patients comprised 51 men and 53 women. Their ages ranged from 23 to 80 years (mean +/- SD, 63.8 +/- 10.4 years). Before and every 3 months after starting latanoprost treatment, iris photographs were taken using a slit-lamp biomicroscope with an attached camera. To identify an increase in iris pigmentation, seven glaucoma specialists independently read the series of photographs. If five of the seven observers agreed that iris pigmentation had increased, we determined that the iris pigmentation had increased from the time the previous photograph was taken. Ten normal volunteers served as controls, and photographs of their eyes were used in the evaluation of iris pigmentation. The Kaplan-Meier life table analysis was adopted to evaluate the incidence of increase in iris pigmentation during treatment with latanoprost.

RESULTS

The Kaplan-Meier life table analysis indicated that the incidence of increased iris pigmentation at 3, 6, 9, 12, and 15 months after the start of latanoprost treatment was 16.3%, 34.2%, 49.5%, 58.2%, and 58.2%, respectively.

CONCLUSIONS

Latanoprost instillation for at least 1 year induced increased iris pigmentation in approximately 50% of the treated Japanese eyes, which is a considerably higher percentage than that reported in Caucasians.

Latanoprost-induced iris darkening: a morphometric study of human peripheral iridectomies

PURPOSE

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.

Update on prostaglandin analogs

Prostaglandin analogs are a novel class of intraocular-lowering medications used primarily for the treatment of glaucoma. These topical medications reduce intraocular pressure primarily by enhancing uveoscleral outflow. The recent literature has enhanced our understanding of the mechanism of action, efficacy, and safety of these agents and has allowed us to better understand the differences between the three commonly used once-daily medications.