Ike K. Ahmed

A novel Schlemm's Canal scaffold increases outflow facility in a human anterior segment perfusion model.

PURPOSE An intracanalicular scaffold (Hydrus microstent) designed to reduce intraocular pressure as a glaucoma treatment was tested in human anterior segments to determine changes in outflow facility (C). METHODS Human eyes with no history of ocular disease or surgeries were perfused within 49 hours of death. The anterior segments were isolated and connected to a perfusion system. Flow rates were measured at pressures of 10, 20, 30, and 40 mm Hg. The scaffold was inserted into Schlemms canal of the experimental eye, while a control eye underwent a sham procedure. Flow rate measurements were repeated at the four pressure levels. Individual C values were computed by dividing the flow rate by its corresponding pressure, and by averaging the four individual C measurements. The change in C between control and experimental eyes was assessed by the ratio of the baseline and second C measurement. In two eyes, the placement of the scaffold was evaluated histologically. RESULTS After scaffold implantation in the experimental eyes, the average C increased significantly from baseline (n = 9, P < 0.05). Ratios of C at all pressure levels, except for 10 mm Hg, were significantly higher in experimental eyes (n = 9) than control eyes (P < 0.05, n = 7). Histologically, the scaffold dilated Schlemms canal with no visible damage to the trabecular meshwork. CONCLUSIONS The Hydrus Microstent provided an effective way to increase outflow facility in human eyes ex vivo.

New devices in glaucoma surgery

Traditional glaucoma drainage devices are made of a tube-and-plate concept that creates an alternate pathway for aqueous humor drainage by channeling the fluid from the anterior chamber through a tube to an equatorial plate that promotes bleb formation. Reactive fibrosis results in the long-term failure of these devices. This led to an explosion of new devices that divert the aqueous into different locations, including the limbal subconjunctival space, the suprachoridal space and Schlemm’s canal. This review outlines the design, surgical success and complications associated with these devices being used in glaucoma surgeries.

EP3/FP dual receptor agonist ONO-9054 administered morning or evening to patients with open-angle glaucoma or ocular hypertension: results of a randomised crossover study.

Background/aims The novel prostaglandin E (EP) 3 and prostaglandin F (FP) receptor agonist ONO-9054 is effective in lowering intraocular pressure (IOP) in patients with ocular hypertension and open-angle glaucoma when administered once daily. This study compares the effects of morning (AM) versus evening (PM) dosing of ONO-9054 on tolerability and IOP lowering. Methods This was a single-centre, randomised, double-masked, two-sequence, placebo-controlled crossover study in 12 subjects with bilateral primary open-angle glaucoma or ocular hypertension. Two 14-day crossover regimens were separated by a 2-week washout: ONO-9054 (1 drop to each eye) in the morning (07:00) and vehicle in the evening (19:00) and vice versa. IOP was measured multiple times during select days. Ocular examinations also evaluated safety and tolerability. Results Mild ocular hyperaemia, reported by six subjects with PM dosing, was the most frequent adverse event. Mild to moderate dryness was also slightly more frequent after PM dosing. Maximum IOP reduction from baseline occurred on day 2 with decreases from baseline of −7.4 mm Hg (−30.8%) for AM dosing and −9.1 mm Hg, (−38.0%) for PM dosing; after 14 days, mean reduction in IOP was −6.8 mm Hg (−28.6%) for AM dosing and −7.5 mm Hg (−31.0%) for PM dosing. Conclusions PM dosing of ONO-0954 was associated with a slightly increased frequency of mild hyperaemia and mild to moderate dryness. Both dosing schedules provided sustained reduction in IOP. Trial registration number NCT01670266.

Intra-operative gonioscopy: a key to successful angle surgery

Since its inception, gonioscopy has been primarily utilized for angle assessment, laser trabeculoplasty and surgery limited to the pediatric age group. Three-fourths of a century would pass since Barkan’s description of goniotomy before intra-operative gonioscopy would come into vogue with the advent of micro-invasive glaucoma surgery. Over the last decade, several clinical trials have been conducted or are currently underway in evaluating devices and instruments targeting different surgical spaces within the angle. However, a rate-limiting step of successful angle surgery requires good gonioscopy and has led to a renewed interest among ophthalmologists to master this skill. During this same time period, several goniosurgical lens prototypes have been introduced in the market with the goal of optimizing angle viewing including clarity, globe stability, accessibility and simultaneous surgical manipulation of angle structures. Several non-gonioscopic methods have also been recently introduced to facilitate angle surgery.

Cadaver corneoscleral model for angle surgery training

PURPOSE To assess a new training model (Tackdriver) for new-generation microinvasive glaucoma surgeries (MIGS). SETTING Resident training centers in Canada. DESIGN Evaluation of technology. METHODS Human cadaver corneoscleral rims recovered after Descemet-stripping endothelial keratoplasty or not suitable for transplantation were acquired from an eye bank. The tissue was fixated with a single tack through the center of the cornea, which was inverted in a concave fashion. A water-based medical lubricant was used for placement of a goniolens after visualization of the anterior chamber and the trabecular meshwork. Microbypass stent (iStent) insertion and gonioscopy-assisted transluminal trabeculotomy (GATT) were practiced on this model. The model was qualitatively assessed for ease of preparation, accuracy of surgical simulation, and the number and variety of MIGS procedures that can be performed. RESULTS Efficient high-volume training was performed for microbypass stent insertion using first-generation and second-generation microbypass stents. The GATT procedure was also performed as a final step in a titratable fashion in 90-, 180-, or 270-degree segments or a complete 360-degree treatment. The model simulated bimanual angle surgery with good fidelity. CONCLUSIONS The training model allowed for high-volume bimanual MIGS training for techniques such as microbypass stent insertion and removal as well as GATT. Preparation was relatively simple, efficient, and cost-effective compared with other models. Inverting the specimen allowed the trainee to practice MIGS techniques independent of the tissues corneal clarity. Other MIGS techniques and angle training procedures can be adopted to this model.

Gold Metal Shunt (GMS) Implant

Surgical management of uncontrolled glaucoma poses several challenges to the ophthalmologist. Suprachoroidal procedures obviate the need to utilize conjunctiva to create filtering blebs (i.e., trabeculectomies) and reduce the risk of failure of bleb-related surgery secondary to bleb-related fibrosis, scarring, infection, or overfiltration. The gold metal shunt implant takes advantage of the natural negative pressure gradient from the anterior chamber into the suprachoroidal space while still providing natural counterpressure to prevent hypotony.

Cataract Extraction with Gold Metal Shunt (GMS) Implant

Surgical management of cataract patients with uncontrolled glaucoma poses several challenges to the ophthalmologist. With the goal of improving visual acuity and optimizing intraocular pressure, the ophthalmologist may choose to combine cataract extraction with glaucoma surgery in one operative encounter. Suprachoroidal procedures obviate the need to utilize the conjunctiva to create filtering blebs (i.e., trabeculectomies) and reduce the risk of failure of bleb-related surgery secondary to bleb-related fibrosis, scarring, infection, or overfiltration. The gold metal shunt implant takes advantage of the natural negative pressure gradient from the anterior chamber into the suprachoroidal space, while still providing natural counterpressure to prevent hypotony.

Baerveldt Drainage Shunt with Scleral Patch Graft

Patients with scarred, friable, or otherwise compromised conjunctival tissue may benefit from the use of a glaucoma shunt device, as their conjunctiva may not be viable for creation of a trabeculectomy bleb. Also, the use of shunt devices as a primary glaucoma procedure is on the rise. The use of a non-valved implant such as the Baerveldt has been shown to offer better long-term IOP control, but the choice of valve often falls into the preference of the surgeon and the ability of the patient to tolerate suboptimal IOP over the first 6 postoperative weeks and a higher complication rate compared with a valved implant (i.e., Ahmed glaucoma valve drainage device).

Cataract Extraction, Endocyclophotocoagulation, and Goniosynechialysis

Patients should have been evaluated and deemed appropriate for such surgical intervention. Surgical indication for cataracts includes those that impair visual acuity, create visual disability, affect activities of daily living and closed angles secondary to lens rise, or deemed medically necessary for monitoring or further surgical procedures. Endocyclophotocoagulation is often combined with cataract surgery to help reduce intraocular pressure. ECP works by inducing thermal damage to the ciliary processes under endoscopic visualization in order to decrease the amount of aqueous produced or to shrink large ciliary processes posteriorly. Patients should have been educated about the risks and benefits of the procedure, including alternatives.

Scleral Suturing and Fixation of a Dislocated Intraocular Lens

In the case of a symptomatic dislocated IOL secondary to trauma, poor capsule-zonular support, or zonulopathy, the surgeon is faced with choosing the appropriate strategy for visual rehabilitation. One of the techniques to improve visual acuity without the need for IOL explantation or exchange is scleral fixation of the dislocated IOL. This technique relies on the surgeon’s ability to stabilize the IOL within the eye and provide a new fixation plane in lieu of the capsular support. When performed correctly, patients may experience excellent visual rehabilitation without the added risk of IOL explantation, large corneal incisions, or extended surgical time.