Monday, April 16, 2018

ALLERGAN SYMPOSIUM


Allergan had organized a symposium titled “The changing face of glaucoma care” on 29th March 2018. The event was held at the Hyatt Regency Hotel, Kota Kinabalu, Malaysia. 
As the chairperson, I had the opportunity to introduce the speakers and manage the proceedings of the symposium.
Myself chairing the occasion

 
Myself with Allergan staff and some of the participants
There were 2 invited speakers : (1) Dr Suresh Subramaniam from Hospital Permaisuri Raja Bainun, Ipoh, Malaysia (2) Dr Peter Kong, who runs the Dr Peter Kong Eye Specialist Centre in Kota Kinabalu. 
Dr Suresh presented 2 talks. The first was on maximal effective therapy (MET) and the second on prostaglandins in glaucoma therapy. Maximal effective therapy centers on 3 points: (1) Every mmHg of IOP reduction counts. Early, effective therapy can bring down IOP and reduce the slope of VF progression. (2) IOP targets have to be individualized to ensure optimal therapy to slow the rate of VF progression. (3) The adherence/efficacy challenge. What makes a patient less likely to achieve the target IOP and how can we address these factors? Compliance is a serious issue in glaucoma management. 

Dr Suresh delivering his talks

A number of PGs are now available for glaucoma therapy. It may become difficult for Ophthalmologists to decide which PG is the best for their patients. In this regard 4 factors can help to differentiate among various agents. These include: (1) Mode of action (2) Preservative (3) Efficacy (4) Cost. Lumigan (bimatoprost) is a prostamide and distinct from prostaglandin analogues in that it has dual trabecular as well as uveoscleral outflow mechanisms. It also has a SUCRA value of 100%, indicating its extreme effectiveness in reducing IOP compared to PGs. 

Dr Peter Kong presented a few of his cases where he implanted Allergan’s Xen gel stent. Most of his patients had good IOP control either as a stand-alone procedure or after the addition of an IOP lowering agent. 
Dr Peter Kong presenting his talk

Friday, February 2, 2018

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:



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

Friday, January 26, 2018

SWEPT-SOURCE OCT
(UPDATED)
 

“Swept source” refers to the type of laser incorporated in “Swept-source OCTs”. Instead of the super-luminescent diode laser typically seen in conventional spectral domain OCTs (SD-OCTs), swept-source OCT (SS-OCT) uses a short-cavity swept laser. Although the swept source laser has a wavelength centered around 1µ, the laser actually changes as it sweeps across a narrow band of wavelengths with each scan. Like SD-OCT, SS-OCT has a fixed reference arm, but it does not use a spectroscope due to the tunable laser. Instead, a complementary metal oxide semi-conductor camera is employed, along with 2 fast parallel photodiode detectors. Thus, extremely high scanning speeds of 100,000 A-scans per second can be obtained. SS-OCT also has a high axial resolution of just 5µ and an improved signal-to-noise ratio.



Advantages of SS-OCT=

  • 1.       High imaging speed: This allows high resolution images to be obtained while reducing the negative effect of patient’s eye movements on scan quality.
  • 2.      It uses an invisible light which is less distracting to patients, compared to the visible light used in SD-OCT.
  • 3.      The long wavelength and swept-source technology provide the ability to obtain clear images of deep ocular structures such as choroid and lamina cribrosa which is the probable site of axonal damage in glaucoma.
  • 4.      Imaging of deep structures is possible as the long wavelength of SS-OCT is less subject to light scatter by the retinal pigment epithelium (RPE). There is less light scattering by lens opacities, therefore, SS-OCT can provide clearer images in patients with cataracts, compared to conventional OCT.
  • 5.      SS-OCT provides uniform sensitivity over the entire scan window, which enables the vitreous, retina and deep ocular structures to be visualized in a single scan. In comparison, conventional SD-OCT does not have the same capability and suffers a drop off in sensitivity with changing scan depth.
  • 6.      Placement of a peripapillary circle is not required with the wide-angle scan. In eyes with an atypical optic disc configuration, such as those with tilted optic discs or extensive areas of peripapillary atrophy, placement of the peripapillary circle can be challenging due to difficulties in delineating the optic disc margins.
  • 7.      The SS-OCT is less susceptible to artifacts that may affect the peripapillary circle measurements, such as those produced by floaters, localized scars or extensive peripapillary atrophy extending to the region of the circle.
  • 8.      Due to segmentation software incorporated in the machine, segmentation of the retinal ganglion cell layer (RGC) and inner plexiform layer (IPL) thicknesses across the entire 12x9mm scan is possible. It may provide a means for direct single-scan structure-structure comparisons of peripapillary and macular retinal layers.

Topcon’s Deep Range Imaging OCT-1 (Atlantis) can perform a wide-field scan covering a 12x9mm area of the posterior pole. Therefore, the disc and macula can be evaluated in a single scan. The DRI-OCT uses a center wavelength of 1050µ and a sweeping range of approximately 100nm, compared to the fixed 850nm wavelength typical of SD-OCT. The instrument uses 2 parallel photodetectors to achieve a scan rate of 100,000 A-scans per second compared to 40,000 A-scans per second scanning rate typical of SD-OCT.
Optic nerve head image obtained by DRI-OCT1





SS-OCT also incorporates automated segmentation software which allows identification of 7 different retinal layers. It is therefore possible to image the circumpapillary retinal nerve fiber layer (RNFL) and macular ganglion cell layer (GCL) using the same scan. The segmentation software also identifies the internal limiting membrane (ILM), IPL, inner segment-outer segment junction (IS/OS), retinal pigment epithelium (RPE), Bruch’s membrane and choroid. Multiple thickness maps can then be generated. 

Possible applications of SS-OCT in glaucoma include: disease detection; identification of novel risk factors; improving the understanding of disease mechanisms. 

In a study conducted by Yang et al, the diagnostic ability of both the wide-angle and peripapillary RNFL thickness measured with SS-OCT were similar to that of peripapillary RNFL thickness measurements obtained with SD-OCT. The average global RNFL thickness measurements acquired by SS-OCT wide-angle scans were thinner than that for peripapillary RNFL scans. This is assumed to be due to more axons in the peripapillary area compared to other areas scanned by wide-angle protocols. However, compared to SD-OCT, SS-OCT had a faster image acquisition rate.


Other studies are being conducted to use SS-OCT in deeper assessment of the lamina cribrosa. SS-OCT is able to scan deeper into the optic nerve head, overcoming image acquisition difficulties due to overlying blood vessels and tissues. This could give us a new perspective on glaucomatous changes in the optic nerve head.




Taken from the article by Yong et al, the above image shows representative swept-source optical coherence tomography (SS-OCT) B-scans of optic discs in high-tension glaucoma (HTG), normal-tension glaucoma (NTG), and healthy eyes.

Horizontal (A, C, E) and vertical (B, D, F) optic disc scans of HTG (A, B), NTG (C, D) and healthy eye (E, F). The image delineated with yellow guidelines is the same as that depicted to the left. The area shaded with yellow depicts the degree of posterior bowing of the lamina cribrosa (LC) according to the level of anterior laminar insertion depth (white solid line). (A, B) Optic disc scans of 65-year-old male with primary open-angle glaucoma (POAG). His baseline intraocular pressure (IOP) was 45 mmHg, and his IOP at examination was 11 mmHg. The overall anterior laminar insertion depth (ALID) was 381.8 μm, the overall mean LC depth (mLCD) was 484.4 μm, and the overall LC curvature index was 102.7 μm. (C, D) Optic disc scans of 65-year-old male with POAG. His baseline IOP was 18 mmHg, and his IOP at examination was 13 mmHg. The ALID was 290.3 μm, the mLCD was 359.9 μm, and the overall LC curvature index was 69.6 μm. (E, F) Optic disc scans of healthy 46-year-old male. His IOP at examination was 13 mmHg. The ALID was 152.6 μm, the mLCD was 146.9 μm, and the overall LC curvature index was –5.7 μm.  

http://www.topcon.co.jp/en/eyecare/products/product/diagnostic/oct/DRI_OCT-1_E.html 

IMAGES RECEIVED FROM TOPCON CORPORATION, JAPAN



 

Wednesday, January 24, 2018

GLAUCOMA UPDATE: SSY ENGINE

A glaucoma update was organized by Allergan at Le Meridian Hotel, Kuala Lumpur, Malaysia on 20th January 2018. The  highlight of the update was the presence of Dr Anders Heijl from Sweden. A name who requires no introduction, Dr Heijl has worked extensively on visual fields: developing SITA for the Humphrey perimeter, the Visual Field Index (VFI) and now the revolutionary SSY engine to determine target intra-ocular pressure (IOP).

Dr Anders Heijl and myself


The update started with a talk on "Glaucoma through the eyes of patients" by Dr Lee Ming Yueh. This was followed by a presentation by Dr Aziz Husni on "Use of structure and function in clinical decision making in glaucoma".




Dr Lee Ming Yueh

Dr Aziz Husni


After a break, Dr Heijl spoke on "Modern Glaucoma Management in Europe".

Dr Anders Heijl

Two things stood out in his talk:

(1) His team conducted a study in Sweden to assess the "Lifetime risk and duration of blindness in patients with manifest open-angle glaucoma (OAG)". According to the study, published in "Ophthalmology" journal, it was found that at the time of death 42.2% of the glaucoma patients were blind in one eye and 16.4% were blind in both eyes. This means that nearly half of the patients being treated for glaucoma ultimately ended up being blind atleast in 1 eye.

Thus, if we extrapolate this data world-wide, it would indicate that the number of patients blind from glaucoma should be much higher compared to epidemiologic studies conducted by others. This would be an eye opener for ophthalmologists, administrators and NGOs. This data needs to be brought to the notice of those who allocate funds for glaucoma care.


(2) Patients in Dr Heijl's study, as well as some other studies, had apparently well controlled IOP. This shows that there are other factors apart from IOP which can cause optic nerve damage and lead to blindness.

So far most of our efforts have been focused on reducing IOP. These include pharmacologic, laser, surgical and other means such as MIGS and Glaucoma Drainage Devices. Not much is being done to protect the nerve (neuroprotection), investigating the role played by other causes of glaucomatous optic atrophy (vascular, biochemical etc) and neuro-regeneration following optic nerve damage.

This lop-sided focus on reducing only IOP is contributing to a quantum jump in blindness from this disease. 

Dr Heijl's second talk was titled "SSY engine in practice". 


The SSY engine is an app to be used on computers and tablets. Like the glaucoma risk calculator, the app is a simple calculating algorithm. It uses data on measured rate-of-progression, current field status, patient's current age and at diagnosis, as well as measured IOP values. The user can simulate different future rates of progression and see future IOP levels associated with those rates. This helps in better target IOP settings depending on the expected life-span of the individual.


Dr Heijl explaining the SSY engine
The app is to be used when the measured rates of progression are available and the treating ophthalmologist is not content with the results. So, this app cannot be used at the time of diagnosis as we do not know the rate of progression at that time and would be useful after 2-3 years of diagnosis when rate of progression is more evident. 

The program was followed by a sumptuous dinner.