Lasers in Ophthalmology Apr 25, 2006 Apr 25, Small Animal Ophthalmology - - DVOS NTUVH -

Outline Introduction of lasers Introduction of lasers Characteristics of eye and lasers Characteristics of eye and lasers Common lasers and applications Common lasers and applications Refractive surgery in human Refractive surgery in human Laser safety Laser safety Diode laser used in Vet Ophthalmology. Diode laser used in Vet Ophthalmology.

Introduction of lasers First medical use was in ophthalmology. First medical use was in ophthalmology. Unique properties ideal for laser. Unique properties ideal for laser. Steady development since 1960s. Steady development since 1960s. Vet clinical use closely linked to humans.(1980s) Vet clinical use closely linked to humans.(1980s)

Methods (probes) Methods or Probes Indications Transcleral probes Contact or noncontact Endoprobe For inside the eye Laser indirect ophthalmoscope (LIO) Laser indirect ophthalmoscope (LIO) Transcorneal and transpupillary Slit lamp biomicroscope Slit lamp biomicroscope Operating microscope adapter (OMA) Operating microscope adapter (OMA)

Characteristics Various media absorb different wavelength Various media absorb different wavelength Media Wavelength (nm) Color Corneal & Sclera Short UV Long IR Lens UV Ocular Pigments Visible spectrum Near-IR

Wavelengths for use WavelengthColorFunctions Short blue Inner retinal layer Inner retinal layer Surface puckering Surface puckering Yellow Some red, Some red, Subretinal neovascular membrane Long Red Deeper to subretinal vessels Deeper to subretinal vessels IR Penetrate sclera well Penetrate sclera well LongerIR Better scleral transmission

Diode laser wavelength

Three pigments Pigments Absorbing color Locations Melanin Most important !! Visible, IR WL ( ) WL, Absorb Uveal tissue (choroid) Uveal tissue (choroid) Retinal pigmented epithelium (RPE) Retinal pigmented epithelium (RPE) Hemoglobin Blue, green, yellow Vascular tissue XanthophyllBlue Macula Macula

Choice of laser Desired tissue Effects Absorption characteristics Absorption characteristics 1.Photocoagulation 1.Photocoagulation 2.Photodisruption 2.Photodisruption 3.Photoablation 3.Photoablation 4.Photochemical 4.Photochemical Damage type Damage type Effect type Effect type 1.Continuous wave mode 2.Pulsed mode

Laser effects EffectsDescription Power and duration Ablation Disappearance of tissue into smoke evacuator Higher power Shorter periods Coagulation Blanching of tissue Lower power Longer periods Distance and power affect the two effects each other.

Common used lasers LaserWLColor Tissue effect Applications Diode810IR-coagulation Retinal photocoagulation Nd:YAG1064IR -coagulation -disruptionIridotomy CO IR-ablationBlepharoplasty Excimer193UV-ablation PRK, LASIK Argon Blue-green-coagulation Retinal photocoagulation

CO 2 laser CO 2 laser Extraocular (eyelids and conjunctiva) applications Extraocular (eyelids and conjunctiva) applications Primarily photoablative effect Primarily photoablative effect Absorbed by water than pigment Absorbed by water than pigment Absorbed by the corneal and sclera. Absorbed by the corneal and sclera. Vaporize water and tissue within a very discrete zone Vaporize water and tissue within a very discrete zone Remove only a few cell layers at a time. Remove only a few cell layers at a time. Blepharoplasty Ablation of eyelid lesions Ablation of conjunctival papillomas Skin resurfacing

Excimer laser ( ) Excimer laser ( ) Photoablative effect Photoablative effect Absorbed by the conrea Absorbed by the conrea Break intermolecular bonds and ablating tissue without causing thermal damage to adjacent tissue. Break intermolecular bonds and ablating tissue without causing thermal damage to adjacent tissue. Ideal for corneal remodeling Ideal for corneal remodeling Refractive surgery (myopia, myopic astigmatism, hyperopia…) Phototherapeutic keratectomy

Diode laser Diode laser Photocoagulation effect Photocoagulation effect Transmitted well through the sclera and clear media Transmitted well through the sclera and clear media Absorbed by melanin and applied to the retina, PRE, choroid, and iris. Absorbed by melanin and applied to the retina, PRE, choroid, and iris. Better scleral transmission with contact mode. Better scleral transmission with contact mode. Additional benefits : small and portable, relatively inexpensive, runs off a standard electrical supply, requires low maintenance. Additional benefits : small and portable, relatively inexpensive, runs off a standard electrical supply, requires low maintenance. Transscleral cyclophotoablation Intraocular neoplasia Capsulotomy Retinopexy

Laser damages WLAbsorbed Damage Effects Cornea Temporary photokeratitis Lens Cataract formation Retina (through the clear media) Visible spectrum Recipient is aware of the exposure Not in visible spectrum Retinal damage may go undetected Cornea Corneal (scleral) burns Penetrate deeper Heating of lens proteins and cataract formation

LASIK LASIK LASIK Laser In-Situ Keratomileusis LASIK Laser In-Situ Keratomileusis LASIK LASIK

(1) (1)

(2) (2)

VCNA Glaucoma laser in VET Lower IOP with ablation effect !! Lower IOP with ablation effect !! Primary on ciliary epithelium Primary on ciliary epithelium Secondary mechanism: Secondary mechanism: Vascular damage Vascular damage Decreased ciliary surface area Decreased ciliary surface area Ciliary body atrophy Ciliary body atrophy Increased uveoscleral outflow (Chen TC, et al. 1999) Increased uveoscleral outflow (Chen TC, et al. 1999) Cyclophotocoagulation >> cyclocryoablation ?? Cyclophotocoagulation >> cyclocryoablation ??

VCNA Nd:YAG laser Nd:YAG was first used in the dogs. Nd:YAG was first used in the dogs. Noncontact mode with average 222J per eye results in IOPand less complications. Noncontact mode with average 222J per eye results in IOPand less complications. Complications: act, postop IOP spike, tissue damage, longer time to control IOP. Complications: cataract, postop IOP spike, tissue damage, longer time to control IOP. Clinically cyclophotoablation in glaucomatous cat eyes does not seem as effective as in dogs. (Cook C, et al. 1997) Clinically cyclophotoablation in glaucomatous cat eyes does not seem as effective as in dogs. (Cook C, et al. 1997) Higher transmission but less absorption by melanin than diode laser. Higher transmission but less absorption by melanin than diode laser.

Diode studies VCNA Large study (Cook C, et al. 1997) Large study (Cook C, et al. 1997) High power, per eye 85J (1.5W x 1.5s per site) High power, per eye 85J (1.5W x 1.5s per site) Complications: most eyes: postop IOP spike, few eyes: corneal ulceration, cataract, intraocular hemorrhage, and retinal detachment Complications: most eyes: postop IOP spike, few eyes: corneal ulceration, cataract, intraocular hemorrhage, and retinal detachment Small study (Hardman C, et al. 1998) Small study (Hardman C, et al. 1998) Higher total energy with low power per eye 125J (1W x 5s) Higher total energy with low power per eye 125J (1W x 5s) Less IOP spike, better IOP control postop Less IOP spike, better IOP control postop Both studies complication : Both studies complication : Cataract & corneal ulceration Cataract & corneal ulceration

Combined TSC diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs w/ 1º glaucoma: 51 cases ( ) Sapienza JS. Vet Ophthal (2) Evaluate diode laser + Ahmed gonioimplant. Evaluate diode laser + Ahmed gonioimplant. 51 dogs age: 3-14yr (7.5yr); most are American Cocker Spaniel. 51 dogs age: 3-14yr (7.5yr); most are American Cocker Spaniel. Immediate surgical complications: Immediate surgical complications: Fibrin formation in ante chamber (15) Fibrin formation in ante chamber (15) Corneal ulcers (4) Corneal ulcers (4) Hyphema (7) Hyphema (7) Focal retinal detachment (1) Focal retinal detachment (1)

Two laser settings Mean total delivered was 109.6±23.6 J Mean total delivered was 109.6±23.6 J Need future study to compare the two settings. Need future study to compare the two settings. SettingSitesCases mW x mS sites 19 eyes High power, Low energy 16/19 (84.2%) visual; 3/19 blind mW x 5000 mS sites 32 eyes Low power, High energy 26/32 (81.3%) visual; 6/32 blind

Diode + gonioimplant (2) Long-term complications Long-term complications Cataract (8 total, 2 of significant, vision-threatening) incidence 8/51= 15.7% Cataract (8 total, 2 of significant, vision-threatening) incidence 8/51= 15.7% Elevated IOP (6) Elevated IOP (6) Unstable gonioimplant (1) Unstable gonioimplant (1) Glaucoma recurrence (14/51, 27.5%) Glaucoma recurrence (14/51, 27.5%) Additional surgery performed Additional surgery performed Intrascleral prosthesis (4) Intrascleral prosthesis (4) Enucleation (1) Enucleation (1) Resection of fibrotic scar tissue (5) Resection of fibrotic scar tissue (5) Repeat laser cycloablation (8) Repeat laser cycloablation (8)

Diode + gonioimplant (3) Final IOP control: Final IOP control: Good : 39/51 (76%) Good : 39/51 (76%) Poor or uncontrolled : 12/51 (24%) Poor or uncontrolled : 12/51 (24%) Visual condition: Visual condition: Immediate short-term visual maintain 42/51 (82%) Immediate short-term visual maintain 42/51 (82%) Table 6- and 12-month follow-up of available cases 6 months Visual eyes Visual eyes 20/41 (49%) Blind eyes Blind eyes 21/41 (51%) 12 months Visual eyes Visual eyes 12/29 (41%) Blind eyes Blind eyes 17/29 (59%)

Diode laser TSCP for the tx of 1ºglaucoma in 18 dogs: a retrospective study Hardman C, VO eyes of 18 dogs 24 eyes of 18 dogs Glaucoma probe with a spot size: 600 microns, 1W x 5S (25 sites) to 125J per eye. Higher total energy with low power protocol. Glaucoma probe with a spot size: 600 microns, 1W x 5S (25 sites) to 125J per eye. Higher total energy with low power protocol. Anterior chamber with 30G needle to control IOP less 15mmHg Anterior chamber with 30G needle to control IOP less 15mmHg Subconjunctival corticosteroids Subconjunctival corticosteroids Temporary tarsorrhaphy was applied in some Temporary tarsorrhaphy was applied in some Post-op topical and systemic steroid + CAI Post-op topical and systemic steroid + CAI Control the IOP < 25mmHg Control the IOP < 25mmHg

This setting is (1W x 5S, 25 sites) higher total energy protocol. Postop complications: Postop complications: Cataracts (6/24, 25%), corneal ulceration (3/24), keratitis (3/24), the 2nd laser treat (3/24) Cataracts (6/24, 25%), corneal ulceration (3/24), keratitis (3/24), the 2nd laser treat (3/24) No hyphema nor phthisis bulbi. No hyphema nor phthisis bulbi. Postop IOP spike 92%, 24-48h: 58%. Hospitalize 1-2days suggested. Postop IOP spike 92%, 24-48h: 58%. Hospitalize 1-2days suggested. Good control IOP: 92%!! (long-term 8-21 months) Good control IOP: 92%!! (long-term 8-21 months) Regain vision: about 50% Regain vision: about 50% But this protocol may result in a higher incidence of secondary cataracts (25%) But this protocol may result in a higher incidence of secondary cataracts (25%)

Iris melanoma treatment Cook CS, VO 1999 Iris melanoma: range 2x3 mm to 4x12mm Iris melanoma: range 2x3 mm to 4x12mm Diode laser delivery system through: Diode laser delivery system through: Operating microscope adapter (OMA) Operating microscope adapter (OMA) Laser indirect ophthalmoscope (LIO) with 20D lens Laser indirect ophthalmoscope (LIO) with 20D lens Mild complications Mild complications Dyscoria, iris hyperpigmentation, corneal edema. Dyscoria, iris hyperpigmentation, corneal edema. Non-invasive diode laser appears to be a safe and effective method. Non-invasive diode laser appears to be a safe and effective method.

Diode laser with LIO VCNA

Potential damage to corneal endothelium w/ diode laser Chandler MJ, Vet. Ophthal Chandler MJ, Vet. Ophthal Transcorneal iridal laser photocoagulation Transcorneal iridal laser photocoagulation Specular and scanning EM show --- No significant changes Specular and scanning EM show --- No significant changes Endothelial cell densities and corneal thickness. Endothelial cell densities and corneal thickness. Take into consideration Take into consideration Young age of the dogs (6-9mo) Young age of the dogs (6-9mo) Endothelial cell regeneration in young dogs Endothelial cell regeneration in young dogs Short period of postop study (3wk) Short period of postop study (3wk)

Laser safety No discussion without mention of safety! No discussion without mention of safety! Laser causing damage depend on… Laser causing damage depend on… Wavelength Wavelength Intensity Intensity Absorption Absorption Laser safety eyewear Laser safety eyewear For eyelids, protected by a non-reflective stainless steel or lead eye shield. For eyelids, protected by a non-reflective stainless steel or lead eye shield. Petroleum-based lubricants Petroleum-based lubricants

TS-600 Wear glasses first !! SAFETY SAFETY Eye protection from treatment laser 810nm. Eye protection from treatment laser 810nm. Also from RED diode aiming laser Also from RED diode aiming laser Reflection hazards: such as metal. Reflection hazards: such as metal. Explosion hazard: flammables or explosives, such as volatile alcohol ( ?) Explosion hazard: flammables or explosives, such as volatile alcohol ( ?) Red

Product specifications Treatment Beam nm (IR) Aiming Beam 650 nm (Red) Laser Spot Sizes 550 micron spot at the fiber tip 550 micron spot at the fiber tip 400 micron spot on the plane of the ciliary body 400 micron spot on the plane of the ciliary body Therapeutic legion size will be larger than theoretical spot size Therapeutic legion size will be larger than theoretical spot size Typical lesion: 2s around 2 mm dia. Typical lesion: 2s around 2 mm dia. Red

Treatment protocol 1500mW x 1500mS (2.25J) High P, Low E. 1500mW x 1500mS (2.25J) High P, Low E. First 5 sites: (more power in lightly pigmented eye) First 5 sites: (more power in lightly pigmented eye) If no pops, increase power to 1750mW If no pops, increase power to 1750mW If 2-3 pops, maintain 1500mW If 2-3 pops, maintain 1500mW If 4-5 pops, decreased power until pops are heard in 50-75% of sites. If 4-5 pops, decreased power until pops are heard in 50-75% of sites. Classification Pre-op IOP Sites J x Sites Prophylactic< Acute & Chronic >

Another protocol Low power, long duration ! More gentle, offering a greater potential for vision retention. More gentle, offering a greater potential for vision retention. High energy protocol: (60J) 100J~200J High energy protocol: (60J) 100J~200J PowerDuration Treat sites 1000mW4000ms Visual eye Blind eye 25-50

Treatment protocol Superior limbus: first sites Superior limbus: first sites 3mm posterior to the limbus with probe perpendicular to sclera. 3mm posterior to the limbus with probe perpendicular to sclera. If buphthalmic eye, mm was used. If buphthalmic eye, mm was used. Inferior limbus: next sites Inferior limbus: next sites Avoid 3 and 9 oclock position Avoid 3 and 9 oclock position Avoid pigmentation conjunctiva Avoid pigmentation conjunctiva Frequent moistening of site with saline Frequent moistening of site with saline

Medication 0.5mg/kg Banamine (NSAID) IV pre-op 0.5mg/kg Banamine (NSAID) IV pre-op 4mg triamcinolone subconjunctival post-op 4mg triamcinolone subconjunctival post-op Topical antibiotic / steroid TID x 14day post-op Topical antibiotic / steroid TID x 14day post-op Follow up: Follow up: Immediate: if IOP > 30mmHg paracentesis with 30G needle to bring IOP 30mmHg paracentesis with 30G needle to bring IOP < 15mmHg. IOP spike within 24hr!! IOP spike within 24hr!! 1hr, 1wk, 4wk, 8wk, 26wk recheck. 1hr, 1wk, 4wk, 8wk, 26wk recheck.

Thank you for your attention ! Schwind Excimer Laser Multi Scan KERATOM