Practical Points of Glaucoma Laser Treatment

Updated 2013-10-18 08:37:15


 

การประชุมราชวิทยาลัยที่ผ่านมา ทางชมรมต้อหินได้จัด Glaucoma Instruction Course ในหัวข้อ "Practical Points of Glaucoma Laser Treatment" โดยมีวิทยากรของชมรมต้อหินมาให้ความรู้เกี่ยวกับชนิดของเลเซอร์และการเลือกใช้ในคนไข้ต้อหินประเภทต่างๆ 
ทางทีมงานได้ขอสรุปรวบรวมเนื้อหาเพื่อให้ทางสมาชิกเข้ามาทบทวนความรู้ค่ะ
ขอขอบพระคุณทางชมรมต้อหินมา ณ ที่นี้ด้วยค่ะ


Chair: Somkiat Asawaphureekorn, MD Darin Sakiyalak, MD 
 
Instructors: Damrong Wiwatwongwana, MD Nisa Sothornwit, MD Boonchai Wangsupadilok, MD Pitipong Suramethakul, MD Sumalee Boonyaleephan, MD Nipon Sayawat, MD

 

Laser peripheral iridotomy (Damrong Wiwatwongwana, MD)

Laser peripheral iridotomy (LPI) is the preferred laser procedure for treating patients with narrow angles, narrow angle glaucoma or acute primary angle closure. The laser is used to make a small opening through the peripheral iris and change the fluid dynamics in the eye. LPI allows the aqueous to pass from the posterior chamber into the anterior chamber and eliminates pupillary block. LPI can also be helpful in making the diagnosis of plateau iris syndrome and pigmentary dispersion.
The Nd:YAG laser photo disruptor is generally used to perform LPI. In case of thick iris, the Argon laser (photocoagulation) is used to thin the iris first as a two stages technique. Conditions causing poor visualization of the iris and patients who unable to cooperate are contraindication for LPI. Complications may include IOP spike, transient blurred vision, iritis, diplopia, closure of the opening, hyphema, lens opacity and corneal injury.

Argon laser peripheral iridoplasty (Nisa Sothornwit, MD)

Argon laser peripheral iridoplasty (ALPI) is a laser surgical technique designed to use in patient who do not respond to laser iridotomy. ALPI works by shrink and pull the peripheral iris tissue away from the trabecular meshwork and opens the drainage angle.
ALPI is generally indicated in cases of acute primary angle closure, phacomorphic glaucoma and chronic non-pupillary block glaucoma.
The study shows that ALPI is significantly more effective than systemic medications in reducing IOP in acute PACG within 2 hours from the treatment and treatment of only 180° appeared to be effective and safe in controlling IOP in acute PACG, independently of the duration of attack.
In phacomorphic glaucoma, ALPI had a greater IOP reduction in 30 minutes compared with medical treatments (70% vs 40%) with less time to achieve IOP<25 mmHg and smaller post-attack C:D ratio. Both iridotomy alone or combined with iridoplasty provide a significant and equivalent IOP reduction in chronic angle closure glaucoma. The success of iridoplasty in CACG relies inversely on extent of PAS, degree of optic disc cupping and visual field changes. Contraindication for ALPI include peripheral anterior synechiae, neovascular glaucoma, uveitis, extensive corneal edema and flat anterior chamber.
Tips for iridoplasty include: place a mid-peripheral laser spot in very shallow A/C, glycerin may help to clear corneal edema in acute angle closure and laser burns should be placed more periphery if retreatment is needed.


Argon laser trabeculoplasty (Boonchai Wangsupadilok, MD)

Argon laser trabeculoplasty (ALT) is an effective way to lower intraocular pressure in primary and secondary open angle glaucoma. The mechanism of action is widely debated. There are several theories, the three most common ones: (1) mechanical theory: laser induce trabecular meshwork tissue contraction causes collagen fiber shrinkage, thereby opening up space in adjacent structures. (2) biological theory: inflammatory cytokines (such as IL-1, TNF) are released by laser treatment and change a composition of extracellular matrix with decreased outflow resistance. (3) repopulation theory: the pinocytotic activity of the trabecular cells is activated and induces the division of the trabecular cells.
ALT is generally recommended for patient with primary open angle glaucoma, pigmentary glaucoma, exfoliative glaucoma, angle recession glaucoma and in some cases of primary angle closure glaucoma. Contraindications include inflammatory glaucoma, neovascular glaucoma, synechial angle closure, developmental glaucoma, advanced glaucoma with high intraocular pressure and in patient with lack of ALT effect in the fellow eye.
Transient IOP elevation may occur, mostly 1-2 hours after laser treatment. Other risks include transient iritis, temporary blurred vision, peripheral anterior synechiae and corneal endothelial cells damage. The factors associated with failure of ALT are younger age and higher IOP.

Selective laser trabeculoplasty (Pitipong Suramethakul, MD)

Selective laser trabeculoplasty (SLT) is a potentially repeatable IOP lowering procedure that safe and effective for increasing tonographic outflow facility. SLT uses a 532-nm frequency doubled Q-switched: Nd:YAG to selectively affect the pigmented TM cells and causes cell death without affect to non-pigmented TM cells.
SLT can be considered as a primary glaucoma treatment option, adjunct to medical therapy or in case of medical therapy failure or inappropriate medical therapy without interfering with the success of future surgery.180-360 degrees laser treatment is recommended. (50 spots/180 degree, 100 spots/360 degree) High baseline IOP is a predictive factor of SLT success.
Complications of SLT are rare including temporary blurred vision, transient iritis, intraocular pressure spike with possible VF loss, PAS and corneal endothelial abnormality.

Diode laser cyclophotocoagulation (Sumalee Boonyaleephan, MD)

Diode laser cyclophotocoagulation is a procedure in which laser energy causes irreversible ciliary body damage. The effect are coagulation of ciliary epithelium, ischemia and increased uveoscleral outflow. It is generally recommended for patients with refractory glaucoma, eyes with limited visual potential and uncontrolled IOP and painful eyes without vision thought to be secondary to elevated intraocular pressure. The use of diode TSCP as primary treatment in eyes with good vision need larger prospective trials.
Anesthetic considerations include peribulbar or retrobulbar block, suboptimal local anesthesia with IV sedation, sub-tenon and subconjunctival anesthesia and general anesthesia. It can be performed via transcleral route, transpupillary route or intraocular route.
Complications of diode TSCP are severe inflammation, hyphema, conjunctival burns, intraocular pressure spike, postoperative hypotony and phthisis, loss of vision, decreased vision, sympathetic ophthalmia and malignant glaucoma.
    The new micro-pulse technology uses a specially modified G-Probe that not commercially available at this time. This technique can reduce thermal spread lead to the diminution of tissue destruction and pain.

  1. Endocyclophotocoagulation (Nipon Sayawat, MD)

Endocyclophotocoagulation (ECP) is a technique that lowers intraocular pressure by selectively target the ciliary epithelium and results in early reduction of perfusion with later reperfusion.  It can be performed in cases of glaucoma uncontrolled by medical treatment and/or filtering surgery, primary open angle glaucoma, angle closure glaucoma, pseudoexfoliation glaucoma, neovascular glaucoma, pediatric glaucoma, uveitic glaucoma, pigmentary and traumatic glaucoma. ECP is still used in conjunction with cataract extraction or tube shunt surgery.
A peribulbar or retrobulbar block is preferred but topical anesthesia with 0.5 cc intracameral non-preservative lidocaine is accepted. A minimum incision size for ECP should be 2.6 mm to avoid corneal torqueing. In combined phacoemulsifiction with ECP, a 2.85 mm side port wound was made 90-120 degrees apart from the main temporal clear cornea incision to allow 270 degrees of ECP treatment. A viscoelastic is used to expand the ciliary sulcus. A probe-tissue distance of 2 mm corresponds to 6 ciliary processes in view. The endpoint is reached when the ciliary processes whitens and shrinks. Generally 270-360 degrees of ciliary processes are treated. The final IOP will be identified between 2-8 weeks post operatively. IOP reductions of 25-35% are common.
Complications include intraocular pressure spike, hemorrhage, serous choroidal effusion, acute graft rejection, visual loss more than 2 lines, hypotony, phthisis bulbi and cataract progression.