Visualization of Changes of the Iris Configuration After Peripheral Laser Iridotomy in Primary Melanin Dispersion Syndrome Using Optical Coherence Tomography

A pigment dispersion syndrome case with concave iris and ocular hypertension managed through a phakic ICL implantation

IntroductionA concave iris configuration is a characteristic feature of pigment dispersion syndrome (PDS). Therapeutic strategies to modify this configuration may be considered as first-line options for the treatment of ocular hypertension in PDS patients.Case descriptionA 37-year-old male patient with myopic anisometropia presented bilateral PDS with concave iris, Krukenberg's spindle and iris transillumination defect in both eyes. The intraocular pressure (IOP) was 27 mmHg in both eyes. Optic nerve and visual field parameters were normal. The right eye was treated with a neodymium:YAG LPI. In the left eye, an implantable collamer lens (ICL) V4c model implantation for myopia correction was performed. Six-months postoperatively, both eyes evidenced an anteriorization of the iris, the morphology of the concave iris improved with the ICL V4c in place, becaming flattener in left eye. The IOP was 18 mmHg without treatment.ConclusionThis case report reinforces the idea that in myopic patients with a concave iris, the refractive correction approach through ICL V4c implantation might also improve the iris configuration, similarly to laser peripheral iridotomy (LPI). Therefore, in this specific patient profile, this surgical procedure might be considered as a prophylactic treatment alternative to prevent the complications associated with this iris configuration, although its invasive nature should be taken into consideration.

Pigment dispersion syndrome and pigmentary glaucoma: overview and racial disparities

Pigment dispersion syndrome (PDS) and pigmentary glaucoma (PG) are two stages within the same ophthalmic disease spectrum, which are known to be affected by race. The prevalence of PDS is underestimated, largely due to its minor clinical symptoms. Although the prevalence of PG is low, the visual impairment associated with PG is extremely severe. The prevalence of PDS-PG is four or more times higher in Caucasians than in Blacks or Asians, and the "classic" PDS in Caucasians has long been used as a benchmark diagnostic criterion. Following extensive research focused on African Americans and Asians, the standard for diagnosing PDS-PG was refined. At the same time, the pathogenesis of PDS is not the same in different races. Hence, the effectiveness of preventive treatment and the need for treatment may not be equivalent in different races. The rate of conversion of PDS to PG is nearly 1/3 in Caucasians and higher in blacks and Asians, requiring more aggressive treatment and monitoring. We systematically searched a PubMed database from inception to March 2022 to provide an overview of research progress in various aspects of PDS-PG. Specifically, this paper considers the effects of race on disease prevalence, clinical manifestation, diagnostic criteria, disease mechanism, hereditary traits, treatment, and prevention to provide an accurate and comprehensive guide for the diagnosis and treatment of PDS-PG in various races.

[Pigmentary glaucoma: yesterday, today, tomorrow]

Pigment dispersion syndrome (PDS) is a condition that mostly affects young men with myopic refraction. PDS is characterized by the presence of Krukenberg spindle, peripheral iris defects, significant trabecular meshwork pigmentation, as well as convex iris configuration. Such configuration can cause friction of iris's posterior pigment layer on its ligaments, which leads to the release of pigment and its accumulation mostly in the structures of the anterior chamber. Over time PDS can progress into pigmentary glaucoma (PG), which in turn can lead to permanent loss of vision. This review analyzes available data on diagnosis and treatment of PDS and PG.

Changes of trabecular meshwork pigmentation in patients with pigment dispersion syndrome: A 15-year study

To report the changes of trabecular meshwork (TM) pigmentation and clinical outcomes of patients with pigment dispersion syndrome (PDS) after resolution of reverse pupillary block.Twenty one eyes of 11 PDS patients were followed up periodically for 15 years after resolution of reverse pupillary block with either Nd: YAG laser peripheral iridotomy (LPI) or trabeculectomy. Visual acuity (VA), best-corrected visual acuity (BCVA), slit lamp examination, intraocular pressure (IOP), Humphrey visual field analysis (VFA), gonioscopy and stereoscopic funduscopy were performed on admission and every 6 months postoperatively. TM pigmentation was quantitatively evaluated and graded every 5 years after the treatment, in which the circumference of anterior chamber angle was divided into 4 quadrants: superior, inferior, nasal and temporal. Postoperative IOP, VA, BCVA, VFA, TM pigmentation and adjunctive anti-glaucoma medications were main outcome measurements and compared with baseline.Eleven patients (9 males, 2 females) were identified as PDS according to the diagnostic criteria, with average age of 38.25 ± 6.93 years (range, 31-55 years) at initial diagnosis. The mean IOP level was 33.1 ± 9.8 mmHg (range, 22-56 mmHg) at diagnosis. Ten PDS eyes received LPI, and the other eleven eyes underwent uneventful trabeculectomy. The median TM pigmentation score of the 21 PDS eyes was 16 (interquartile range [IQR], 15-16) on admission, which changed to 14 (IQR, 13-15), 13 (IQR, 12-14), 12(IQR, 10.5-12) at 5-, 10-, 15-year follow-up visits respectively. The decrease rate of TM pigmentation was 37% in inferior quadrant, while in nasal, temporal, and superior quadrant the reduction rate was 28%, 23%, and 18%, respectively, at the last follow-up visit. Majority of these enrolled eyes (19/21) had stable VA and BCVA with average endpoint IOP of 15.1 ± 3.4 mmHg.TM pigmentation in PDS patients attenuates with time after reverse pupillary block was resolved, in which the inferior quadrant seems faster than the other quadrants.

Pigment dispersion syndrome and its implications for glaucoma

Pigment dispersion syndrome (PDS) represents a clinical spectrum of a relatively common and usually underdiagnosed phenomenon produced by spontaneous pigment dispersion from the iris into the anterior segment. PDS is often bilateral, has no gender predisposition, and presents at a young age, particularly in myopes. Although most patients experiencing an episode of pigment dispersion are asymptomatic, extreme photophobia, ocular pain, redness, and blurred vision may occur. Other characteristic signs are iridolenticular contact, concave iris configuration, 360° peripheral iris transillumination, and pigment deposition on the anterior chamber angle or the corneal endothelium (Krukenberg spindle). Early PDS diagnosis is crucial to detect patients with pigment-related ocular hypertension (POHT) that can eventually lead to pigmentary glaucoma (PG). The latter represents a sight-threatening condition in which mechanical, environmental, and genetic factors contribute to optic nerve damage. In this review, we update the pathogenic mechanisms involved in the clinical spectrum of the disease. We describe its clinical presentation, ophthalmologic manifestations, and complications, including the factors influencing the development of POHT and PG. Because PDS has variable clinical presentations that lead to misdiagnoses, we emphasize the differential diagnosis and the actual therapeutic strategies according to disease status.

Effects of Nd-YAG Laser iridotomy on anterior segment measurements in pigment dispersion syndrome and ocular hypertension

PURPOSE

To compare the anterior segment optical coherence tomography (AS-OCT) measurements of eyes with pigment dispersion syndrome (PDS) and ocular hypertension (OHT) before and after neodymium:yttrium-aluminum-garnet (Nd:YAG) laser peripheral iridotomy (LPI).

METHODS

A total of 23 eyes of 23 patients with PDS and OHT with features of PDS were included in this retrospective study. All of the eyes with PDS and OHT were examined by AS-OCT before and after Nd:YAG LPI. Anterior chamber depth, angle opening distance 500, angle opening distance 750, trabecular iris space 500, trabecular iris space 750 and scleral spur angle, iris bowing and iris shape were measured with AS-OCT by the same examiner.

RESULTS

The differences in all parameters before and after Nd:YAG LPI were statistically significant. Iris configuration was concave in all eyes prior to iridotomy. After Nd:YAG laser iridotomy, the iris configuration became convex in 7 eyes, flat in 9 eyes and remained concave in 7 eyes.

CONCLUSION

Nd:YAG laser peripheral iridotomy is an effective method for reversing the iris concavity and iris bowing in pigment dispersion syndrome.

Quantitative Assessment of Anterior Chamber Parameters in Pigmentary Glaucoma Using Slit-Lamp Optical Coherence Tomography

Purpose.

To quantitatively assess the parameters of anterior chamber and angle dimensions by slit-lamp optical coherence tomography (SL-OCT) in eyes with pigmentary glaucoma (PG).

Methods.

A total of 18 eyes of 11 patients with PG and 18 eyes of 11 healthy volunteers were included in the study. Anterior chamber depth (ACD), anterior chamber volume (ACV), spur distance (internal horizontal anterior chamber diameter), central corneal thickness (CCT), angle opening distance at 500 urn from the scleral spur (AOD 500), and trabecular iris space area at 500 μm from the scleral spur (TISA 500) parameters were detected by SL-OCT. The differences of anterior chamber parameters between patients with PG and the control group were analyzed by Mann-Whitney U test.

Results.

Mean ACD and ACV were measured as 3.28±0.38 mm and 191.6±39.7 mm3 respectively in the PG group. Mean AOD 500 and TISA 500 were 0.88±0.47 mm and 0.29±0.15 mm2 at the nasal angle and 1.14±0.67 mm and 0.41 ±0.23 mm2 at the temporal angle, respectively. Nasal and temporal angles were 49.83±11.1° and 53.83±10.46°. In eyes with PG, the midperipheral iris configuration was found to be considerably concave in 15 eyes (83.3%). Except CCT and spur distance, all anterior chamber dimension and angle parameters detected by SL-OCT were found to be significantly higher in the eyes with PG (Mann-Whitney U test, p<0.05).

Conclusions.

SL-OCT provided highly quantitative data on the parameters of anterior chamber and angle dimensions in PG. The evaluation of the anterior segment anatomy using SL-OCT revealed increased anterior chamber dimensions and posterior bowing of the iris consistent with the increase in angle parameters in patients with PG.

[Role of laser peripheral iridotomy in pigmentary glaucoma and pigment dispersion syndrome: A review of the literature [French version]]

PURPOSE

Pigment dispersion syndrome (PSD) is characterized by a structural abnormality of the posterior surface of the iris causing contact with the zonular fibers. It can lead to an open-angle glaucoma secondary to pigment dispersion into the trabecular meshwork. Laser peripheral iridotomy (PI) has been proposed as a treatment for pigmentary glaucoma (PG) and pigment dispersion syndrome (PDS) by reducing the dispersion of pigment. The goal of this review was to assess the effects of PI for PSD and PG.

METHODS

We included six randomized controlled trials and two cohort studies (286 eyes of 218 participants). Four trials included participants with PG, and 4 trials enrolled participants with PSD with or without elevated intraocular pressure (IOP).

RESULTS

Among patients with PG, at an average of 9 months of follow-up, the mean difference in IOP between groups was 2.69mmHg less in the PI group (95 % CI: -6.05 to 0.67; 14 eyes). In patients with PDS, the average IOP was statistically lower after PI as compared to baseline (Student test, t=11.49, P<0.01). With regard to visual field progression in participants with GP, after an average follow-up of 28 months, the risk of progression was not influenced by PI (RR 1.00 95 %: CI 0.16 to 6.25; 32 eyes). No trials that enrolled patients with PSD showed a diminution of the risk of glaucoma conversion at mid- and long-term.

CONCLUSION

PI decreases the biomechanical factor causing contact between the iris and zonular fibers and may lower IOP over the long-term. Nevertheless, the effects of PI on visual field changes or progression have not been established in PG and PDS. There is no scientific evidence as of yet to advocate PI as a treatment for PDS or PG.

Peripheral iridotomy for pigmentary glaucoma

BACKGROUND

Glaucoma is a chronic optic neuropathy characterized by retinal ganglion cell death resulting in damage to the optic nerve head and the retinal nerve fiber layer. Pigment dispersion syndrome is characterized by a structural disturbance in the iris pigment epithelium (the densely pigmented posterior surface of the iris) that leads to dispersion of the pigment and its deposition on various structures within the eye. Pigmentary glaucoma is a specific form of open-angle glaucoma found in patients with pigment dispersion syndrome.Topcial medical therapy is usually the first-line treatment; however, peripheral laser iridotomy has been proposed as an alternate treatment. Peripheral laser iridotomy involves creating an opening in the iris tissue to allow drainage of fluid from the posterior chamber to the anterior chamber and vice versa. Equalizing the pressure within the eye may help to alleviate the friction that leads to pigment dispersion and prevent visual field deterioration. However, the effectiveness of peripheral laser iridotomy in reducing the development or progression of pigmentary glaucoma is unknown.

OBJECTIVES

The objective of this review was to assess the effects of peripheral laser iridotomy compared with other interventions, including medication, trabeculoplasty, and trabeculectomy, or no treatment, for pigment dispersion syndrome and pigmentary glaucoma.

SEARCH METHODS

We searched a number of electronic databases including CENTRAL, MEDLINE and EMBASE and clinical trials websites such as (mRCT) and ClinicalTrials.gov. We last searched the electronic databases on 2 November 2015.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that had compared peripheral laser iridotomy versus no treatment or other treatments for pigment dispersion syndrome and pigmentary glaucoma.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures for systematic reviews. Two review authors independently screened articles for eligibility, extracted data, and assessed included trials for risk of bias. We did not perform a meta-analysis because of variability in reporting and follow-up intervals for primary and secondary outcomes of interest.

MAIN RESULTS

We included five RCTs (260 eyes of 195 participants) comparing yttrium-aluminum-garnet (YAG) laser iridotomy versus no laser iridotomy. Three trials included participants with pigmentary glaucoma at baseline, and two trials enrolled participants with pigment dispersion syndrome. Only two trials reported the country of enrollment: one - Italy, the other - United Kingdom. Overall, we assessed trials as having high or unclear risk of bias owing to incomplete or missing data and selective outcome reporting.Data on visual fields were available for one of three trials that included participants with pigmentary glaucoma at baseline. At an average follow-up of 28 months, the risk of progression of visual field damage was uncertain when comparing laser iridotomy with no iridotomy (risk ratio (RR) 1.00, 95% confidence interval (95% CI) 0.16 to 6.25; 32 eyes; very low-quality evidence). The two trials that enrolled participants with pigment dispersion syndrome at baseline reported the proportion of participants with onset of glaucomatous visual field changes during the study period. At three-year follow-up, one trial reported that the risk ratio for conversion to glaucoma was 2.72 (95% CI 0.76 to 9.68; 42 eyes; very low-quality evidence). At 10-year follow-up, the other trial reported that no eye showed visual field progression.One trial reported the mean change in intraocular pressure (IOP) in eyes with pigmentary glaucoma: At an average of nine months of follow-up, the mean difference in IOP between groups was 2.69 mmHg less in the laser iridotomy group than in the control group (95% CI -6.05 to 0.67; 14 eyes; very low-quality evidence). This trial also reported the mean change in anterior chamber depth at an average of nine months of follow-up and reported no meaningful differences between groups (mean difference 0.04 mm, 95% CI -0.07 to 0.15; 14 eyes; very low-quality evidence). No other trial reported mean change in anterior chamber depth. Two trials reported greater flattening of iris configuration in the laser iridotomy group than in the control group among eyes with pigmentary glaucoma; however, investigators provided insufficient data for analysis. No trial reported data related to mean visual acuity, aqueous melanin granules, costs, or quality of life outcomes.Two trials assessed the need for additional treatment for control of IOP. One trial that enrolled participants with pigmentary glaucoma reported that more eyes in the laser iridotomy group required additional treatment between six and 23 months of follow-up than eyes in the control group (RR 1.73, 95% CI 1.08 to 2.75; 46 eyes); however, the other trial enrolled participants with pigment dispersion syndrome and indicated that the difference between groups at three-year follow-up was uncertain (RR 0.91, 95% CI 0.38 to 2.17; 105 eyes). We graded the certainty of evidence for this outcome as very low.Two trials reported that no serious adverse events were observed in either group among eyes with pigment dispersion syndrome. Mild adverse events included postoperative inflammation; two participants required cataract surgery (at 18 and 34 months after baseline), and two participants required a repeat iridotomy.

AUTHORS' CONCLUSIONS

We found insufficient evidence of high quality on the effectiveness of peripheral iridotomy for pigmentary glaucoma or pigment dispersion syndrome. Although adverse events associated with peripheral iridotomy may be minimal, the long-term effects on visual function and other patient-important outcomes have not been established. Future research on this topic should focus on outcomes that are important to patients and the optimal timing of treatment in the disease process (eg, pigment dispersion syndrome with normal IOP, pigment dispersion syndrome with established ocular hypertension, pigmentary glaucoma).

Anterior-segment morphology and corneal biomechanical characteristics in pigmentary glaucoma

Purpose

The aim of the study reported here was to evaluate characteristics of the anterior-segment via anterior-segment optical coherence tomography (AS-OCT) and corneal biomechanical properties using an ocular response analyzer and their changes by peripheral laser iridotomy (PI) in patients with pigmentary glaucoma (PG).

Materials and methods

Seventeen eyes with PG were included consecutively. AS-OCT and ocular response analyzer measurements were taken before and 3 months after PI. Baseline morphology and change in morphology were analyzed by correlation and multiple linear regression analysis. The main parameters assessed were anterior-chamber (AC) angles and volume as well as corneal hysteresis (CH) and corneal resistance factor.

Results

AC angles were found to have decreased significantly in each quadrant after PI (P<0.001), with the highest effect seen in the temporal quadrant, which decreased from 57.0°±9.6° to 44.1°±5.2° (± standard deviation). Mean AC volume decreased significantly from 213.1±36.4 to 187.0±23.4 mm³ (P<0.001). CH and corneal resistance factor did not change after PI. CH was found to correlate with the preoperative superior and inferior angle width (Spearman’s rho 0.553 and 0.615, respectively, P<0.05). Biomechanical parameters showed no predictive value on the change of AC angles or volume.

Conclusion

PI in eyes with PG results in a highly significant reduction in the AC angles and volume as visualized by AS-OCT, with the largest effect seen in the temporal quadrant. CH is strongly positively correlated with the superior and inferior preoperative AC angles, emphasizing the importance of the biomechanical properties of the cornea for glaucoma pathogenesis in PG, but corneal biomechanical properties cannot predict PI-related AC changes.

[Is prophylactic YAG iridotomy useful in pigment dispersion syndrome?]

Despite theoretical considerations concerning the advantage of iridotomy in eyes with pigment dispersion syndrome or early pigment glaucoma, there is a lack of clinical evidence that this procedure has a long-term effect in preventing glaucoma damage under these circumstances. However, several factors may contribute to this lack of evidence, e.g. the statistical problem of a low conversion rate from pigment dispersion syndrome to pigment glaucoma or the inclusion criteria in the studies treating patients older than 40 years or genetic dispositions in pigment glaucoma that are not yet fully clear. On the basis of current data the decision for YAG iridotomy should only be taken in patients younger than 40 years, if the midperipheral iris shows an inverse bowing and the intraocular pressure is normal or slightly increased with no progressive signs of optic nerve damage. In cases of insufficient intraocular pressure and visual defects due to glaucomatous optic nerve damage, incisional glaucoma surgery is usually necessary especially in younger patients with a long life expectancy.

Value of optical coherence tomography for anterior segment surgery

Anterior segment optical coherence tomography (AS-OCT) is an important new noncontact imaging technology that uses a 1310 nm super luminescent diode. It can be used to assess anterior chamber biometry, corneal thickness, lens thickness, and angle configuration; to visualize pathological processes; to evaluate postsurgical anatomy and posttraumatic eyes; and to image phakic intraocular lenses and intracorneal ring segments. Because it is a noncontact technique, it can also be used intraoperatively, which could be useful during trabeculectomy and after deep anterior lamellar keratoplasty to detect abnormalities in the cornea and interface. A disadvantage of AS-OCT is its inability to penetrate the iris pigment epithelium, which makes it impossible to evaluate the structures behind the iris. The most frequently used devices are time-domain AS-OCT, but new Fourier-domain OCT devices, which have faster image acquisition and higher resolution, are currently under investigation.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.