Dan Q Nguyen

Intraocular Pressure Lowering Is Associated with an Increase in the Photopic Negative Response (PhNR) Amplitude in Glaucoma and Ocular Hypertensive Eyes

PURPOSE The aim of our study was to determine whether IOP lowering in glaucomatous and ocular hypertensive (OHT) eyes leads to an improvement in the full-field photopic negative response (PhNR) of the electroretinogram. METHODS A prospective nonrandomized interventional cohort study was conducted. Patients with OHT or glaucomatous optic neuropathy were recruited, and photopic full-field electroretinograms (ERG) were performed at baseline and then repeated 1 to 2 months later. The change in PhNR amplitude was compared between those eyes that had a significant lowering in IOP (defined as >25% decrease from baseline or to a predetermined target IOP) during follow-up and those that did not. RESULTS From a cohort of 30 eyes, 18 eyes had a significant reduction in IOP during follow-up (n = 18) and 12 eyes had no significant change in IOP (<25% reduction in IOP, n = 12). A significant increase in PhNR amplitude and the PhNR/b-wave amplitude ratios was observed in the reduced IOP group, but not in the IOP stable group for the two flash intensities used (2.25 and 3.00 cd.s/m(2)). CONCLUSIONS The full-field PhNR amplitude provides a potentially reversible measure of inner retinal function that improves after IOP lowering. Further study now is required to assess its use as a measure of optic nerve health in glaucoma patients.

Bleb vascularity following post-trabeculectomy subconjunctival bevacizumab: a pilot study

Background:  To determine whether postoperative subconjunctival bevacizumab significantly alters bleb vascularity.

Effect of phacoemulsification on trabeculectomy function

To evaluate the effect of phacoemulsification on trabeculectomy function.

A Model to Measure Fluid Outflow in Rabbit Capsules Post Glaucoma Implant Surgery

PURPOSE Prior models of glaucoma filtration surgery assess bleb morphology, which does not always reflect function. Our aim is to establish a model that directly measures tissue hydraulic conductivity of postsurgical outflow in rabbit bleb capsules following experimental glaucoma filtration surgery. METHODS Nine rabbits underwent insertion of a single-plate pediatric Molteno implant into the anterior chamber of their left eye. Right eyes were used as controls. The rabbits were then allocated to one of two groups. Group one had outflow measurements performed at 1 week after surgery (n = 5), and group two had measurements performed at 4 weeks (n = 4). Measurements were performed by cannulating the drainage tube ostium in situ with a needle attached to a pressure transducer and a fluid column at 15 mm Hg. The drop in the fluid column was measured every minute for 5 minutes. For the control eyes (n = 6), the anterior chamber of the unoperated fellow eye was cannulated. Animals were euthanized with the implant and its surrounding capsule dissected and fixed in 4% paraformaldehyde, and embedded in paraffin before 6-μm sections were cut for histologic staining. RESULTS By 7 days after surgery, tube outflow was 0.117 ± 0.036 μL/min/mm Hg at 15 mm Hg (mean ± SEM), whereas at 28 days, it was 0.009 ± 0.003 μL/min/mm Hg. Control eyes had an outflow of 0.136 ± 0.007 μL/min/mm Hg (P = 0.004, one-way ANOVA). Hematoxylin and eosin staining demonstrated a thinner and looser arrangement of collagenous tissue in the capsules at 1 week compared with that at 4 weeks, which had thicker and more densely arranged collagen. CONCLUSIONS We describe a new model to directly measure hydraulic conductivity in a rabbit glaucoma surgery implant model. The principal physiologic endpoint of glaucoma surgery can be reliably quantified and consistently measured with this model. At 28 days post glaucoma filtration surgery, a rabbit bleb capsule has significantly reduced tissue hydraulic conductivity, in line with loss of implant outflow facility, and increased thickness and density of fibrous encapsulation.

Sociodemographic factors and utilization of eye care services: is there an association with patients presenting to a tertiary referral hospital in acute angle-closure?

Background:  The aim of this study is to examine the relationship between sociodemographic factors and utilization of eye care services in patients presenting in acute angle‐closure (AAC).

Comment on 'Phakic intraocular lenses outcomes and complications: Artisan vs Visian ICL'.

Sir, We read with interest Hassaballa and Mackys1 article on phakic intraocular lenses (p-IOL) outcomes and complications. In their series significant complications resulting in elevation of intraocular pressure (IOP) requiring additional surgery occurred in two eyes (3%). As noted there are several possible mechanisms for increased IOP in patients implanted with a p-IOL. If IOP remains uncontrolled removal of a p-IOL may potentiate further pigment dispersion. There are case reports of intractable IOP elevation presumed secondary to pigment dispersion requiring surgery.2, 3 We performed non-penetrating glaucoma surgery for a similar case of bilateral severe IOP elevation post p-IOL implantation in a patient with high myopia.3 The authors report pigment dispersion occurring in 28.6% (Artisan) and 15.38% (Visian) in their series. They did not document whether all patients underwent pre- and post-operative gonioscopy to examine the anterior chamber angle. Stulting et al4 reported an incidence of iris pigment precipitates of 6.9%. A long-term incidence of pigment dispersion of 6.6% has also been described.5 This may be of significance as patients undergoing p-IOLs are generally from a younger demographic. As the article stands, we agree with the authors on the need for long-term data on the efficacy and complications of p-IOLs. Evaluation of the possible effect on trabecular function from p-IOL-related pigment dispersion is warranted. Pigment dispersion is not always benign.

Determination of Bleb Capsule Porosity With an Experimental Glaucoma Drainage Device and Measurement System

IMPORTANCE Control of intraocular pressure after implantation of a glaucoma drainage device (GDD) depends on the porosity of the capsule that forms around the plate of the GDD. OBJECTIVE To compare capsular porosity after insertion of 2 different GDDs using a novel implant and measurement system. DESIGN, SETTING, AND SUBJECTS We performed an experimental interventional study at an eye research facility in a tertiary eye care center. Testing was performed on 22 adult New Zealand white rabbits that received the experimental GDD or an existing GDD. INTERVENTIONS A new experimental GDD, the Center for Eye Research Australia (CERA) implant, was created using computer-aided design and a 3-dimensional printer. The CERA GDDs were implanted in the eyes of rabbits randomized into 1 of the following 3 groups: with no connection to the anterior chamber (n = 7), with connection to the anterior chamber for 1 week (n = 5), and with connection to the anterior chamber for 4 weeks (n = 5). In a control group (n = 5), a pediatric GDD was implanted without connection to the anterior chamber. We measured the capsular porosity using a pressure-gated picoliter pump at a driving pressure of 12 mm Hg. The animals were killed humanely for histologic study. MAIN OUTCOMES AND MEASURES Porosity of the fibrous capsule around the implant. RESULTS We found no difference in mean (SEM) capsular porosity between the CERA (3.39 [0.76; 95% CI, 1.43-5.48] µL/min) and pediatric (4.52 [0.52; 95% CI, 3.19-5.95] µL/min) GDDs (P = .28, unpaired t test) at 4 weeks without aqueous exposure. Mean (SEM) capsular porosity of CERA GDDs connected to the anterior chamber at 1 week was 2.46 (0.36; 95% CI, 1.55-3.44) µL/min but decreased to 0.67 (0.07; 95% CI, 0.49-0.86) µL/min at 4 weeks (P = .001, unpaired t test). CONCLUSIONS AND RELEVANCE Our experimental method permits direct measurement of capsular porosity of an in situ GDD. In a comparison between an experimental (CERA) and an existing GDD, no differences were identified in capsular porosity or histologic reaction between the implants. These results suggest that the CERA GDD model can be used to test key components of glaucoma surgery and implant design.