Shan C. Lin

Aqueous Shunts in Glaucoma: A Report by the American Academy of Ophthalmology

OBJECTIVE To provide an evidence-based summary of commercially available aqueous shunts currently used in substantial numbers (Ahmed [New World Medical, Inc., Rancho Cucamonga, CA], Baerveldt [Advanced Medical Optics, Inc., Santa Ana, CA], Krupin [Eagle Vision, Inc, Memphis, TN], Molteno [Molteno Ophthalmic Ltd., Dunedin, New Zealand]) to control intraocular pressure (IOP) in various glaucomas. METHODS Seventeen previously published randomized trials, 1 prospective nonrandomized comparative trial, 1 retrospective case-control study, 2 comprehensive literature reviews, and published English language, noncomparative case series and case reports were reviewed and graded for methodologic quality. RESULTS Aqueous shunts are used primarily after failure of medical, laser, and conventional filtering surgery to treat glaucoma and have been successful in controlling IOP in a variety of glaucomas. The principal long-term complication of anterior chamber tubes is corneal endothelial failure. The most shunt-specific delayed complication is erosion of the tube through overlying conjunctiva. There is a low incidence of this occurring with all shunts currently available, and it occurs most frequently within a few millimeters of the corneoscleral junction after anterior chamber insertion. Erosion of the equatorial plate through the conjunctival surface occurs less frequently. Clinical failure of the various devices over time occurs at a rate of approximately 10% per year, which is approximately the same as the failure rate for trabeculectomy. CONCLUSIONS Based on level I evidence, aqueous shunts seem to have benefits (IOP control, duration of benefit) comparable with those of trabeculectomy in the management of complex glaucomas (phakic or pseudophakic eyes after prior failed trabeculectomies). Level I evidence indicates that there are no advantages to the adjunctive use of antifibrotic agents or systemic corticosteroids with currently available shunts. Too few high-quality direct comparisons of various available shunts have been published to assess the relative efficacy or complication rates of specific devices beyond the implication that larger-surface-area explants provide more enduring and better IOP control. Long-term follow-up and comparative studies are encouraged.

Endoscopic photocoagulation of the ciliary body for treatment of refractory glaucomas.

PURPOSE To evaluate the safety and efficacy of endoscopic cyclophotocoagulation in the treatment of refractory glaucomas. METHODS The preoperative and postoperative courses of 68 eyes of 68 patients who underwent endoscopic cyclophotocoagulation at our institution were retrospectively reviewed. Study patients had diverse forms of glaucoma, and most had failed maximal medical therapy as well as failed filtration or transscleral cyclodestructive procedures, or both. Endoscopic cyclophotocoagulation treatment encompassed 180 to 360 degrees of the ciliary body circumference and was performed through a limbal incision (56 eyes, 12 of which underwent concurrent cataract extraction) or pars plana incision (12 eyes). A second laser treatment was required in five eyes (7%). RESULTS During the mean follow-up period of 12.9 months, mean +/- SD intraocular pressure decreased from 27.7 +/- 10.3 mm Hg preoperatively to 17.0 +/- 6.7 mm Hg at the final postoperative visit (P < .0001), for a mean reduction of 10.7 mm Hg and a mean percent decrease of 34%. Sixty-one eyes (90%) achieved an intraocular pressure < or = 21 mm Hg. Using this definition of success, Kaplan-Meier analysis predicted a successful outcome in 94% of patients after 1 year and 82% after 2 years. The mean number of glaucoma medications used by each patient was reduced from 3.0 +/- 1.3 preoperatively to 2.0 +/- 1.3 postoperatively (P < .0001). Best-corrected visual acuity was stable or improved in 64 eyes (94%), with four (6%) losing 2 or more lines of Snellen acuity. No case of hypotony (intraocular pressure < 5 mm Hg) or phthisis was observed. CONCLUSION These early results suggest that endoscopic cyclophotocoagulation is a safe and effective therapeutic modality for refractory glaucomas.

Novel Glaucoma Procedures: A Report by the American Academy of Ophthalmology

OBJECTIVE To review the published literature and summarize clinically relevant information about novel, or emerging, surgical techniques for the treatment of open-angle glaucoma and to describe the devices and procedures in proper context of the appropriate patient population, theoretic effects, advantages, and disadvantages. DESIGN Devices and procedures that have US Food and Drug Administration clearance or are currently in phase III clinical trials in the United States are included: the Fugo blade (Medisurg Ltd., Norristown, PA), Ex-PRESS mini glaucoma shunt (Alcon, Inc., Hunenberg, Switzerland), SOLX Gold Shunt (SOLX Ltd., Boston, MA), excimer laser trabeculotomy (AIDA, Glautec AG, Nurnberg, Germany), canaloplasty (iScience Interventional Corp., Menlo Park, CA), trabeculotomy by internal approach (Trabectome, NeoMedix, Inc., Tustin, CA), and trabecular micro-bypass stent (iStent, Glaukos Corporation, Laguna Hills, CA). METHODS Literature searches of the PubMed and the Cochrane Library databases were conducted up to October 2009 with no date or language restrictions. MAIN OUTCOME MEASURES These searches retrieved 192 citations, of which 23 were deemed topically relevant and rated for quality of evidence by the panel methodologist. All studies but one, which was rated as level II evidence, were rated as level III evidence. RESULTS All of the devices studied showed a statistically significant reduction in intraocular pressure and, in some cases, glaucoma medication use. The success and failure definitions varied among studies, as did the calculated rates. Various types and rates of complications were reported depending on the surgical technique. On the basis of the review of the literature and mechanism of action, the authors also summarized theoretic advantages and disadvantages of each surgery. CONCLUSIONS The novel glaucoma surgeries studied all show some promise as alternative treatments to lower intraocular pressure in the treatment of open-angle glaucoma. It is not possible to conclude whether these novel procedures are superior, equal to, or inferior to surgery such as trabeculectomy or to one another. The studies provide the basis for future comparative or randomized trials of existing glaucoma surgical techniques and other novel procedures.

Cyclophotocoagulation: A report by the American Academy of Ophthalmology

OBJECTIVE This document describes cyclophotocoagulation procedures for glaucoma and examines the evidence to answer key questions about patient selection, and efficacy of transscleral and endoscopic techniques. METHODS A literature search conducted for the years 1968 to 2000 retrieved 130 citations. The author reviewed 34 of these articles and selected 19 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies. RESULTS The predominant problem with all studies on cyclophotocoagulation is the lack of a uniform definition of success, which makes comparisons difficult. One randomized controlled trial (Level I evidence) compared the efficacy of transscleral cyclophotocoagulation with noncontact Nd:YAG and semiconductor diode laser. It found no significant difference between the two, although a significant problem was the variability allowed with laser parameters. Most of the literature consists of noncomparative case series that provide evidence that is limited and often not convincing. CONCLUSION Cyclophotocoagulation is indicated for patients with refractory glaucoma who have failed trabeculectomy or tube shunt procedures, patients with minimal useful vision and elevated intraocular pressure, and patients who have no visual potential and need pain relief (based on Level III evidence). It may be useful for patients whose general medical condition precludes invasive surgery or who refuse more aggressive surgery (i.e., filter or tube). It is also useful in emergent situations, such as the acute onset of neovascular glaucoma. There is insufficient evidence to definitively compare the relative efficacy of the cyclophotocoagulation procedures for glaucoma. It is the panels opinion, however, that semiconductor diode systems appear to possess the best combination of effectiveness (based on Level III evidence), portability, expense, and ease of use at this time.

Correlation between intraocular pressure, central corneal thickness, stage of glaucoma, and demographic patient data: prospective analysis of biophysical parameters in tertiary glaucoma practice populations.

PurposeTo determine the correlation of central corneal thickness (CCT) to Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT, PASCAL®), and to glaucoma stage as assessed by cup-to-disc ratio (CDR). DesignProspective, cross-sectional tricenter observation study. Patients and MethodsFrom three glaucoma specialty practices a sample of 406 independent eyes was included. After ultrasound pachymetry, intraocular pressure was measured using PASCAL® and Goldmann applanation tonometry and cup-to-disc ration was reassessed. Demographic data were included in the multivariate analysis. ResultsMean corneal thickness was 540 μm. African Americans and normal-tension glaucoma patients showed the lowest values (518 μm and 522 μm, respectively). These values were significantly thinner than the central corneal thickness of Caucasians (549 μm) and ocular hypertensives (564 μm). Intraocular pressure assessed by Goldmann applanation tonometry shows a significant correlation with central corneal thickness (r2=0.068, P<0.001), whereas PASCAL® is not significantly associated with central corneal thickness (r2<0.001, P=0.997). Increased IOP is significantly correlated with large ocular pulse amplitudes (r2=0.13, P<0.001), which is predominantly seen in ocular hypertensives. A significant negative correlation was detected between cup-to-disc ratio and central corneal thickness (r2=0.102, P<0.001). ConclusionGlaucoma patients with thin central corneal thickness are more likely to be found at an advanced stage of the disease and among those with normal-tension glaucoma and black African ancestry. Underestimation of intraocular pressure by Goldmann applanation tonometry could be one causative factor.

Automated perimetry: A report by the American academy of ophthalmology

OBJECTIVE The purpose of this document is to summarize and evaluate the effectiveness of new automated perimetry tests and algorithms in diagnosing glaucoma and detecting disease progression. METHODS A literature search on automated perimetry retrieved over 300 citations from 1994 to 2001, of which 71 were selected as relevant to this assessment. The quality of the evidence obtained from these studies was assessed by the methodologist. RESULTS The four automated perimetry techniques described in this assessment are short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), high-pass resolution perimetry (HPRP), and motion automated perimetry (MAP). The algorithms described are Swedish interactive threshold algorithm (SITA) and SITA fast. With the exception of SWAP, these techniques and algorithms reduce testing time and inconsistent patient performance when compared with conventional full threshold testing. CONCLUSIONS Short wavelength automated perimetry detected visual field loss earlier than standard threshold automated perimetry, with a sensitivity and specificity of about 88% and 92% respectively. However, it is a lengthy, demanding test, is sensitive to media opacities, and has a greater magnitude of long-term fluctuation compared with standard threshold automated perimetry, which make it difficult to assess disease progression accurately. When compared to standard threshold automated perimetry, FDT perimetry showed sensitivity and specificity greater than 97% for detecting moderate and advanced glaucoma, and sensitivity of 85% and specificity of 90% for early glaucoma. As FDT perimetry has a short testing time and is resistant to blur and pupil size, it may be a useful screening tool. In a longitudinal study, high-pass resolution perimetry was more effective than standard threshold automated perimetry in monitoring progressive glaucomatous loss, detecting progression at a median of 12 months earlier in 54% of patients studied. Motion automated perimetry demonstrated usefulness in detecting early glaucomatous visual loss in a longitudinal study. Studies on SITA demonstrated greater sensitivity and reproducibility and less intertest variability when compared to standard full threshold testing and a 50% reduction in testing times. A study comparing standard full threshold, SITA, and SITA fast found a sensitivity of 95% for the first two techniques and 93% for SITA fast. Long-term follow-up studies are needed to assess the ability of these techniques to detect progression of glaucoma over time.

Dynamic contour tonometry: principle and use

Interindividual variability of central corneal thickness has been found to be a source of error for conventional Goldmann applanation tonometry. The dynamic contour tonometer represents a potentially new technology for non‐invasive and direct intraocular pressure (IOP) measurement, and has been proposed to accurately measure the true IOP irrespective of the corneal thickness. It is based on the principle that when the tip of the device exactly matches the contour of the cornea, the pressure measured by a transducer placed on its tip is an accurate indicator of the true IOP. This device is also capable of measuring the ocular pulse amplitude, a variable that has controversial significance in the diagnosis and management of glaucoma. Even though this technique seems to be very promising, further studies are required to conclusively determine the effectiveness of the dynamic contour tonometer in patients having an abnormal or irregular corneal contour.

Laser Trabeculoplasty for Open-Angle Glaucoma A Report by the American Academy of Ophthalmology

OBJECTIVE To provide an evidence-based summary of the outcomes, repeatability, and safety of laser trabeculoplasty for open-angle glaucoma. METHODS A search of the peer-reviewed literature in the PubMed and the Cochrane Library databases was conducted in June 2008 and was last repeated in March 2010 with no date or language restrictions. The search yielded 637 unique citations, of which 145 were considered to be of possible clinical relevance for further review and were included in the evidence analysis. RESULTS Level I evidence indicates an acceptable long-term efficacy of initial argon laser trabeculoplasty for open-angle glaucoma compared with initial medical treatment. Among the remaining studies, level II evidence supports the efficacy of selective laser trabeculoplasty for lowering intraocular pressure for patients with open-angle glaucoma. Level III evidence supports the efficacy of repeat use of laser trabeculoplasty. CONCLUSIONS Laser trabeculoplasty is successful in lowering intraocular pressure for patients with open-angle glaucoma. At this time, there is no literature establishing the superiority of any particular form of laser trabeculoplasty. The theories of action of laser trabeculoplasty are not elucidated fully. Further research into the differences among the lasers used in trabeculoplasty, the repeatability of the procedure, and techniques of treatment is necessary. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Intraocular Pressure and Ocular Pulse Amplitude Comparisons in Different Types of Glaucoma Using Dynamic Contour Tonometry

Purpose: To compare the intraocular pressures (IOP) and ocular pulse amplitudes (OPA) in patients with different types of glaucoma, ocular hypertension (OHT), and normal controls (NC) using dynamic contour tonometry (DCT) and the goldmann applanation tonometry (GAT). Methods: 906 eyes of 501 adult patients in the following five groups were included in this cross-sectional study: primary open angle glaucoma (POAG), normal tension glaucoma (NTG), Pseudoexfoliative Glaucoma (PXG), OHT, and NC. The following tests were performed simultaneously during a single visit: IOP using DCT and GAT; OPA using DCT and central corneal thickness (CCT) using ultrasound pachymetry. Mixed effects regression models were used to compare the DCT and GAT IOP measurements in the five groups; the effect of CCT on IOP and the relationship between OPA and IOP within each group. Results: DCT consistently had higher IOP values than GAT in POAG, PXG, NTG, and controls (p < 0.001) but not in OHT (p = 0.84). DCT IOP did not change while GAT IOP showed a non-significant increase (p = 0.09) with increased corneal thickness in each group. OPA was found to be highest in OHT (3.61 mmHg) and lowest in the control group (2.86 mmHg) and significantly increased with IOP in all groups. Conclusions: DCT measures an IOP that is significantly higher than GAT IOP in glaucoma and control subjects but not in ocular hypertensives. Furthermore, the DCT may measure an IOP that is independent of the CCT, which may not be true for the GAT, which increases with the CCT. OPA was highest in OHT and may be affected by the IOP.

Anterior Chamber Depth, Iridocorneal Angle Width, and Intraocular Pressure Changes After Phacoemulsification: Narrow vs Open Iridocorneal Angles

OBJECTIVE To determine the association of changes in anterior chamber angle and anterior chamber depth (ACD) with intraocular pressure (IOP) reduction after uncomplicated phacoemulsification. METHODS In this prospective study, subjects underwent phacoemulsification with foldable lens implantation. Anterior chamber angle grading of 2 or less (Shaffer grading) in 3 or all quadrants was considered narrow angle (NA). Anterior segment optical coherence tomography and tonometry were performed preoperatively and 10 days and 1, 3, and 6 months after surgery. The ACD and angle opening distance at 500 μm anterior to the scleral spur (AOD500) were assessed from anterior segment optical coherence tomography. RESULTS Data were collected from 63 eyes that underwent cataract surgery. Twenty-six eyes were classified as having NA. Before surgery, the mean (SD) AOD500 and ACD in the NA group were 0.179 (0.014) mm and 2.23 (0.07) mm, respectively. Six months after surgery, the mean (SD) AOD500 and ACD in the NA group were 0.389 (0.025) mm and 3.75 (0.05) mm, respectively. The postoperative IOP was reduced significantly in both groups. We found that each 0.1-mm increase in AOD500 corresponded to a mean (SD) 0.42 (0.18)-mm Hg decrease in IOP (P < .001) in the NA group and 0.32 (0.16) mm Hg (P = .046) in the OA group. CONCLUSIONS Postoperative reduction in IOP was proportional to the increase in angle in both groups, but the IOP reduction per 0.1-mm increase in AOD500 in NA eyes was greater than that in OA eyes.