DR. MALIK KAHOOK: GUEST AUTHOR

Dr Malik Kahook  is the Professor of Ophthalmology; Vice Chair, Clinical and Translational Research; Director of Glaucoma service and glaucoma fellowship program at the University of Colorado School of Medicine, USA. 

The "Glaucoma Specialty Club: The Glog" is honored to have his views on the Kahook Dual Blade which is proving to be a new armament in our armory to fight glaucoma. 

Dr Malik Kahook

"The Kahook Dual Blade (KDB) device was launched in the United States in 2015 and is now available around the globe. This has allowed the collection of real world data regarding KDB’s utility and safety in everyday practice."

Kahook Dual Blade

"One example of a clinical data set involved a prospective interventional case series of consecutive patients with glaucoma who had phacoemulsification plus goniotomy with KDB. Of the 71 eyes included in this study, 70% had primary open-angle glaucoma. Other diagnoses included angle-closure, pigmentary, pseudoexfoliative, and normal-tension glaucoma. Sixty-five percent of eyes were classified as having mild to moderate glaucoma and 35%, severe glaucoma. The mean baseline IOP decreased from 17.4 mm Hg ± 5.2 (SD) to 12.8 ± 2.6 mm Hg 6 months postoperatively and the hypotensive medication use decreased from 1.6 ± 1.3 to 0.9 ± 1.0, respectively (P < .001 and P = .005, respectively). The most common observation was blood reflux during surgery (39.4%). The authors concluded that the KDB plus phacoemulsification resulted in a significant and sustained reduction in IOP and a decrease in glaucoma medications after 6 months of follow-up.

The goal for inventing the KDB device was to find a better and more efficient method for removing a complete strip of TM using an ab interno approach while minimizing damage to surrounding tissues. The preclinical testing and subsequent clinical data collected to date reveal that the KDB can safely remove TM and allow for aqueous humor egress through the distal outflow system. The documented safety and efficacy has made KDB a valuable part of the surgical care of glaucoma patients with disease ranging from mild to end-stage while the added versatility of combining KDB with cataract surgery or as a standalone treatment has made it a mainstay in operating rooms around the globe." 

A video of the KDB is available at the following website:

https://www.youtube.com/watch?v=ruZw-WK_f34  

REFERENCES:

https://www.ncbi.nlm.nih.gov/pubmed/?term=greenwood+kahook
https://www.ophthalmologymanagement.com/issues/2017/february-2017/blade-lets-nature-take-its-own-course

KAHOOK DUAL BLADE vs iSTENT: A META-ANALYSIS

 

The Kahook Dual Blade (KDB) is a modern goniotomy device. The goal for inventing the KDB device was to find a better and more efficient method for removing a complete strip of trabecular meshwork (TM) using an ab interno approach while minimizing damage to surrounding tissues.

CHECK LINK: https://ourgsc.blogspot.com/search?q=kahook

The iStent is a minimally invasive glaucoma surgery (MIGS) device devised to bypass the obstructed TM and allow the flow of aqueous from the anterior chamber into the Schlemm’s canal.

CHECK LINK: https://ourgsc.blogspot.com/search?q=iStent

A systematic review and meta-analysis comparing the KDB with iStent implantation with phacoemulsification was done by Guedes et al.

Fourteen studies were included with a total of 1959 eyes (958 phaco-KDB, and 1000 phaco-Stent including 753 phaco-iStent and 207 phaco-iStent inject).

The combined findings showed significantly higher rates of surgical success in the phaco-KDB group versus the phaco-Stent group (odds ratio: 0.68; 95% CI: 0.50 to 0.92; P = 0.01; I2 = 40%), and greater IOP reduction in the phaco-KDB group versus the phaco-Stent group at month 6 (MD: 1.13 mm Hg; 95% CI: 0.43 to 1.83; P = 0.002; I2 = 51%).

By month 12, both groups demonstrated similar IOP reduction. Subgroup analysis at month 12 showed greater IOP reduction in the phaco-KDB group versus the phaco-iStent group (MD: 1.69 mm Hg; 95% CI: 0.44 to 2.95; P = 0.008; I2 = 74%). However, compared with the phaco iStent inject group, there was no significant difference in IOP reduction (MD: −0.72 mm Hg; 95% CI: −3.69 to 2.24; P = 0.63; I2 = 64%). Medication reduction and the incidence of adverse events were comparable between groups.

RESULT:

The study concluded that KDB goniotomy may offer better surgical success compared with Stent implantation when used in combination with phacoemulsification. KDB goniotomy demonstrated better IOP reduction at month 12 compared with iStent. However, iStent inject showed a similar IOP reduction to KDB.

REFERENCE:

Guedes J, Amaral DC, de Oliveira Caneca K, Cassins Aguiar EH, de Oliveira LN, Mora-Paez DJ, Cyrino LG, Louzada RN, Moster MR, Myers JS, Schuman JS, Shukla AG, Shalaby WS. Kahook Dual Blade Goniotomy Versus iStent Implantation Combined With Phacoemulsification: A Systematic Review and Meta-Analysis. J Glaucoma. 2025 Mar 1;34(3):232-247. doi: 10.1097/IJG.0000000000002522. Epub 2024 Dec 9. PMID: 39641580.

SPYGLASS DRUG DELIVERY PLATFORM

 

A new drug delivery platform for anti-glaucoma medication has been developed by Dr. Malik Y. Kahook, professor of ophthalmology and the Slater Family Endowed Chair in Ophthalmology at the University of Colorado School of Medicine, USA.

Known as the SpyGlass Drug Delivery Platform, it is implanted with the SpyGlass intra-ocular lens (IOL) into the capsular bag via standard cataract surgical technique.

The SpyGlass drug delivery platform consists of a single-piece, hydrophobic acrylic IOL and two drug eluting pads that slide over each haptic and securely attach at the haptic junction. With the drug pads securely attached, the IOL and pads are loaded into a standard IOL injector. The lens is advanced and injected through a sub 2.4 mm incision and implanted directly into the capsular bag.

The drug pads remain outside the visual axis and continuously elute directly into the aqueous humor, which carries the active drug to targeted tissues.

The pads elute Bimatoprost for three years into the eye, providing sustained delivery of the drug for effective glaucoma management.

Pre-clinical testing found compelling IOP lowering in normotensive beagles with 3 doses compared to 0.03% topical bimatoprost. In NZW rabbits there was no detectable systemic exposure and no drug related adverse events even at 10x the maximum dose up to 9 months.

A prospective study was performed to evaluate the safety and efficacy of the sustained release bimatoprost implant with SpyGlass IOL in patients with ocular hypertension or mild to moderate open-angle glaucoma. The results of the study at 3 months reported 45% mean IOP reduction across all doses and all patients became off topical IOP-lowering therapy.

ENDOSCOPIC CYCLOPHOTOCOAGULATION

 

Endoscopic cyclophotocoagulation (ECP) is a procedure to lower aqueous production by laser-induced destruction of the ciliary processes, the site of aqueous production in the eyes. The key feature of ECP is direct visualization of the ciliary processes as the target tissue for controlled laser ablation. With this procedure, it is possible to titrate the extent of ciliary body ablation to maximize IOP lowering while minimizing collateral damage and adverse events. It can be performed along with cataract surgery or as a stand-alone treatment.

The ECP instrumentation consists of the laser endoscope and the console to which it is attached. The laser endoscopy console combines a 175 W xenon light source for illumination, 810 nm diode laser for photocoagulation, helium-neon laser aiming beam, and video imaging for intraocular visualization.

The endoscopy probe contains all three fiber groupings and is available in 19, 20, or 23 gauge sizes with a field of view ranging from 70° to 140° and depth of focus spanning 1–30 mm. The probe tips are straight or curved and easily fit through a 2.0 mm clear corneal incision. Another advantage to the 23-gauge probe is its compatibility with all 23-gauge vitrectomy trocar systems. The probes can be sterilized and reusable up to 25 times or more.

A variety of anesthesia may be used for ECP including intracameral, sub-Tenon's, or retrobulbar routes of administration. If intracameral anesthesia is utilized, increased intravenous sedation may be needed to maximize patient comfort during the laser application.

Before the start of the procedure, the three component cables of the ECP probe should be securely connected to the laser console. The camera image should be focused with the desired orientation and illumination adjusted outside the eye before the initiation of surgery. The laser should be set to continuous duration with an initial power of 0.25 W and an aiming beam setting of 20–30.

A temporal or superiorly placed clear corneal incision is performed near the limbus, approximately 2.0 mm in width. The ciliary sulcus is deepened with cohesive viscoelastic to improve visualization of the ciliary processes. The probe is then inserted through the corneal wound and positioned in the sulcus at or near the pupillary border.

The surgeon then directs his/her gaze towards the monitor to gain orientation in the sulcus and identify the target tissue. During treatment, approximately 6-7 ciliary processes should be in view at all times as this places the probe at an optimal distance for absorption of laser energy. Once the aiming beam is placed over a ciliary process, the foot pedal is depressed to deliver laser energy continuously. Treatment is titrated according to the visualized tissue response. The process should whiten and shrink to a variable degree after appropriate treatment.

If the probe is closer to the processes, a shorter duration and/or lower power will be needed to reach the desired effect. Rupture or popping of the processes should be avoided as an indication of over-treatment. The probe can then be advanced along the adjacent processes while applying laser energy. The entire visible area of each ciliary process should be treated including anterior and posterior edges as well as crypts in between processes.

Treatment should be carried to the extent of visualization in one direction, and then the probe is rotated 180° with rotation of the image on the monitor, and treatment is continued as far as possible in the other direction. With a curved probe, a single incision allows treatment of approximately 270° of ciliary processes. If more treatment is desired, a second incision may be placed 180° away from the initial wound to gain access to the subincisional processes and complete a 360° treatment for additional IOP lowering.

In aphakic or pseudophakic patients, a pars plana approach (ECP plus) may also be utilized to achieve a more thorough treatment of the ciliary processes when aggressive IOP lowering is desired. A standard 2 or 3 port pars plana vitrectomy must be performed initially, followed by insertion of the probe through one of the sclerotomies. Once the processes are visualized, treatment is carried out in the same fashion as the anterior approach. The anterior 1-2 mm of pars plana may also be treated in severe, refractory cases but may increase the risk for hypotony postoperatively.

At the end of the procedure viscoelastic is removed and the incision/s coapted.

Postoperatively the patient is started on steroid drops until the inflammation resolves. The anti-glaucoma medications are continued until the inflammation subsides and the desired IOP is achieved.

REFERENCE:

Seibold LK, SooHoo JR, Kahook MY. Endoscopic cyclophotocoagulation. Middle East Afr J Ophthalmol. 2015 Jan-Mar;22(1):18-24. doi: 10.4103/0974-9233.148344. PMID: 25624669; PMCID: PMC4302471.

 

MENTAL HEALTH AND GLAUCOMA

 

Memory and cognitive impairment, as well as other mental health problems (e.g., depression and anxiety) are conditions which could significantly reduce a glaucoma patient's ability to adhere to the treatment regime. Poor adherence to treatment may lead to preventable vision loss.

Cognitive impairment may prevent one from adhering to treatment, regardless of the complexity of the treatment regimen. In a study, 12% of patients reported difficulty remembering to take their medications [Sleath B, Robin AL, Covert D, et al. Patient-reported behavior and problems in using glaucoma medications. Ophthalmology. 2006;113(suppl 3):431–436]

Another study has shown that the patients who were nonadherent to the treatment protocol had more frequent memory problems than participants classified as adherent. Such memory problems included forgetting when to take their medication and forgetting appointments. [Stryker JO, Beck AD, Primo SA, et al. An exploratory study of factors influencing glaucoma treatment adherence. J Glaucoma. 2010;19:66–72]

In a study by Yochim and colleagues, controlling for age, in subjects above 50 years of age, memory impairment was found in approximately 20% of the sample, and impaired executive functioning was found in approximately 22% of the sample. Mild-to-moderate depressive symptoms were found in 12.2% of participants, and 1 person reported clinically significant anxiety. [Yochim, Brian P. PhD, ABPP*; Mueller, Anne E. MA*; Kane, Katherine D. MA*; Kahook, Malik Y. MD†. Prevalence of Cognitive Impairment, Depression, and Anxiety Symptoms Among Older Adults With Glaucoma. Journal of Glaucoma 21(4):p 250-254, April/May 2012. | DOI: 10.1097/IJG.0b013e3182071b7e]

The results from Yochim’s study indicate that cognitive impairment may be common in older patients with glaucoma. This has implications for treatment adherence, as difficulties in remembering information may significantly impede the ability to follow instructions from a physician.

Care-givers for glaucoma patients are usually focused on compliance to treatment but overlook the mental health issues of the patients which could be driving the poor adherence to protocols.

Since these care-givers are often the first to interact with such patients, it is imperative that they are able to pick the signs and symptoms providing clues to the presence of mental health issues in these patients.

Appropriate interventions can achieve better quality of life in these patients in the long run.