Enhancing the early differential diagnosis of plateau iris and pupillary block using a-scan ultrasonography

Plateau Iris: A Review

Purpose

To review the concept of plateau iris and summarize the recent evidence on its diagnosis and management.

Methods

This is a narrative review on the plateau iris. A literature review was conducted in PubMed, Google Scholar, and Scopus databases using keywords: angle-closure glaucoma, glaucoma, nonpupillary block glaucoma, plateau iris, and plateau iris management.

Results

This review defined the current knowledge about plateau iris. First of all, the anatomy and epidemiology were discussed. Then, we outlined the available evidence on the diagnosis of plateau iris and its differential diagnosis. Conclusively, the treatment options were mentioned.

Conclusions

Plateau iris is a condition in which nonpupillary block mechanisms are responsible for intraocular pressure elevation and angle closure attack when a patent peripheral iridotomy has removed the relative pupillary block. An anteriorly positioned ciliary body causes mechanical obstruction of trabecular meshwork in these patients. It is usually seen in younger patients with angle closure and is diagnosed by gonioscopic examination and imaging modalities such as Ultrasound biomicroscopy. Despite the known mechanism of plateau iris, there is no consensus over treatment. Low-dose pilocarpine and Argon laser peripheral iridoplasty are nonsurgical treatments for these patients, but their effects are short-term. Cataract extraction with/without endocyclophotocoagulation (ECP), endocycloplasty, excisional goniotomy, and transscleral cyclophotocoagulation are alternative treatments. Patients should be examined periodically for further progression or recurrence of plateau iris. In cases of glaucoma unresponsive to conventional medical treatments, surgical treatments such as trabeculectomy and drainage devices should be considered.

Efficacy of Combined Phacoemulsification and Goniosynechialysis in Primary Angle Closure Disease With Different Degrees of Peripheral Anterior Synechiae

PRCIS

Phacoemulsification and goniosynechialysis (Phaco-GSL) was equally effective in the treatment of primary angle-closure disease (PACD) with preoperative peripheral anterior synechiae (PAS) <180 degrees and larger than 180 degrees. Patients with a larger preoperative PAS range required more range of mechanical separation intraoperatively and displayed more recurrence of PAS (re-PAS) range postoperatively.

PURPOSE

To evaluate the long-term efficacy of combined phaco-GSL in PACD with different extent of PAS.

PATIENTS AND METHODS

A retrospective study was conducted on 67 patients (79 eyes) who received phaco-GSL. The patients were divided into 2 groups according to the extent of PAS (group A: PAS ≤180 degrees; group B: PAS >180 degrees). Changes in intraocular pressure (IOP), the number of anti-glaucoma drugs, intraoperative mechanical separation of PAS and range of re-PAS during the last follow-up ≥12 months were analyzed.

RESULTS

At baseline, eyes in group B presented with higher IOP and more anti-glaucoma drugs usage ( P =0.008 and 0.004). The PAS range, IOP, number of anti-glaucoma medication were reduced both in 2 groups at the final visit. The range of mechanical separation intraoperatively and re-PAS postoperatively were both larger in group B ( P =0.002 and <0.001). The postoperative re-PAS range was positively correlated with the range of mechanical separation ( R2 =0.17). The complete success rates at 12, 24, 36, and 48 months were 86.8%, 71.1%, 71.1%, and 71.1% in group A; and 80.5%, 74.6%, 69.9%, and 69.9% in group B. The qualified success rates were 100%, 96.6%, 92.0%, and 92.0% in group A; and 100%, 89.5%, 85.1%, and 85.1% in group B.

CONCLUSION

Phaco-GSL for the treatment of PACD showed equally effective IOP control regardless of the extent of preoperative PAS.

Prevalence of Plateau Iris in Primary Angle Closure Glaucoma: An Egyptian Hospital Based Ultrasound Biomicroscopy Study

Purpose

To determine the distribution and the anatomical characteristics of plateau iris (PI) in primary angle closure glaucoma (PACG) using ultrasound biomicroscopy (UBM).

Methods

Fifty UBM images of PACG cases were studied over one year by retrospective analysis. The data from UBM images including angle opening distance at 500 and 750 μm (AOD500 and AOD750), trabecular-iris angle (TIA), angle recess area at 750 μm (ARA750), maximum ciliary body thickness (CBTmax), anterior placement of ciliary processes (APCP), central anterior chamber depth (CACD), axial lens thickness (ALT), and ciliary sulcus status were analyzed and compared between the PI and non-PI cases.

Results

Eighteen cases had PI (36%). The mean AOD500, AOD750, and TIA were significantly smaller in PI than in non-PI eyes (P = 0.01; P = 0.046; and P = 0.026). Values of the ARA750 and CBTmax were not significantly different between the two groups (P = 0.208 and P = 0.368). CACD was deeper in the PI group (P = 0.011). ALT was higher in the non-PI group (P = 0.001). The mean APCP of the PI group was more than those of the non-PI group (P < 0.001). The number of cases with obliterated ciliary sulcus in more than two quadrants was significantly more in the PI group (P < 0.001).

Conclusion

Around one-third of PACG eyes were found to have PI on UBM imaging. The number of obliterated ciliary sulcus and APCP were important UBM parameters that help in PI diagnosis.

Measurement of the depths at different regions of the anterior chamber in healthy Chinese adults

AIM

To measure the depths of different regions of the anterior chamber (AC) in healthy Chinese adults, and to explore possible correlations with age or gender.

METHODS

The AC was imaged by swept-source optical coherence tomography in healthy Chinese adults. The horizontal scan of the right eye was used to measure the anterior chamber depth (ACD) at 199 points.

RESULTS

A total of 309 images from 309 subjects were analyzed. The ACD values at nearly all locations were negatively correlated with age (all P<0.05), except for ACD1, 2, 198, and 199 (correspond to the iris roots). The mean annual decrease 0.013±0.005 mm/y for all ACDs combined, 0.008±0.004 mm/y for the peripheral region, 0.017±0.003 mm/y for the middle peripheral region, and 0.014±0.001 mm/y for the central region. The mean annual decrease was significantly different among these three regions (P<0.001). The ACD was greater in males than in females (P<0.05). The mean difference in ACD between males and females was 0.081±0.025 mm.

CONCLUSION

This study showed that optical coherence tomography can be used to measure the ACD of different regions of the AC. We found reductions in ACD with age, although the reduction varied among different points, in healthy Chinese adults.

Qualitative and quantitative evaluation of acute angle-closure mechanisms

BACKGROUND

To evaluate ocular biometric parameters in different subtypes of acute angle closure and compared to fellow eyes of AAC and PACS eyes.

METHODS

This is a retrospective chart review study. A total of 167 eyes (96 patients) consisting of 71 AAC eyes, 71 fellow eyes of AAC, and 25 PACS eyes were recruited. All patients underwent ocular examination and biometry. The mechanism of AAC was confirmed by ultrasound biomicroscopy. We then subdivided AAC eyes into four subgroups: crowded-angle (CR), lens subluxation (LS) pupillary block (PB), and plateau iris syndrome (PL). Outcome variables included anterior chamber depth (ACD), lens thickness (LT), vitreal length (VL), axial length (AL), lens position and relative lens position (LP and RLP, respectively), and lens axial length factor (LAF).

RESULTS

Among the three groups, ACD was shallower in AAC eyes than fellow eyes of AAC and PACS eyes (p < 0.01 for both) and AAC eyes demonstrated a lesser LP and RLP. The LT, VL, AL, and LAF were not significantly different among the three groups. Among the four subgroups, LS displayed the most shallow ACD (p = 0.01). The lens position in PL was greater than in CR and LS (p < 0.05 and <0.01, respectively).

CONCLUSIONS

AAC eyes had a more anterior lens position than fellow eyes and PACS eyes, though lens thickness did not differ among the groups. As such, an anterior lens position may offer more sensitive prognostication regarding future development of AAC compared to lens thickness.