Information and emerging technology of laser application in ophthalmology

1. EMERGING EYE ISSUES
PRESENTER:CYNTHIA OLOO
Bsc Comprehensive ophthalmology and cataract surgery
JKUAT/SABATIA EYE HOSPITAL

7. PROPERTIES OF LASER
1.Directionality-It has the shape of the narrow beam that can remain
apparently unchanged as its propagates
2. Monochromaticity- It is a single color radiation; spectoral bandwidth of a
common helium-neon laser, emitting red light with a wavelength of
632.8nm.is measured in thousands of nanometer
3.Coherence-It has high degree of coherence they can oscillate with a fixed
phase relative to each other; two types
-longitudinal coherence; is related to the temporal properties allowing us to
conc. Laser light in time in the form of very short laser pulses
-Transverse coherence; it perpendicular to the propagation axis, is related to
its spartial properties allowing us to conc. Laser light in space in the form of
tiny ,bright, focused spots of light

8. 4.Brightness-Are typically very bright, extended in space, light spread
apart as it moves away from the source

33. LASER SURGERY IN CORNEA
NEOVASCULARIZATION
• There are several treatment modalities to achieve antiangiogenesis/
angioregression.
• Medical and surgical approaches such as topical corticosteroids,
NSAIDS, anti-VEGF agents, cyclosporine A
• Laser treatments , fine needle diathermy and keratectomy
• Innovative treatments using genetic modulations are under
investigation
• Photothermal laser (ND:YAG-KTP 532nm) and photodynamic therapy
with photosensitizers are well established as alternative treatment for
corneal NV

34. • Argon laser was first described by Cherry and Garner in 1973, it
operates through the induction of thermal lesions following energy
absorption by hemoglobin
• Photodynamic therapy was first described by Fossarelo in 2003, acts
through the induction of free radicals leading to vascular obstruction
• A prospective human study was published by Yoon et al. in 18
patients , using a diode laser source and verteporfin as a
photosensitizers, showing similar results .in a comparative study dye
yellow laser 570nm and argon laser 514nm showed similar efficiency

36. • In 1970s argon laser (Nd : YAG-KTP) became the first to be regularly
used for performing a non-invasive iridotomy, it is well absorbed by
iris pigments
• IN 1980S , Q-switched Nd:YAG laser(YAG laser 1064nm) was
introduced, this device can be highly effective in light colored irides
• Indicated intreatment and prevention of acute angle closer, pigment
dispersion glaucoma, pupillary block, diagnosis of plateau iris
syndrome

37. peripheraliridoplasty/gonioplasty
• The first attempt to use laser energy near the iris root to widen the
angle were made by Krasnov and Kimbrough
• In the late seventies ,using laser parameters more like penetrating
burns rather than the slow contraction burns that ultimately proved
to be optimal
• The term gonioplasty was first used by Kimbrough ,who treated 360
degrees of peripheral iris through gonioscopy lens.

38. trabeculoplasy
• The application of laser to the trabecular meshwork was described by
Krasnov in 1972 and also by Worthen and Wickam in1973
• Argon laser applied to TM induces significant IOP reduction as
described by Wise and Witter 1979
• With development of selective laser trabeculoplasty by Latina and
park( approved by the US FDA in 2001)
• Indicated in primary and secondary OAG
• CONTRAINDICATED in angle closure glaucom

40. ANTERIOR HYALOIDOTOMY AND TRANSCLERAL CPC
• Aqueous misdirection syndrome was first described in1869 by
Albrecht von Graefe
• Laser procedure performed in a step ladder approach
1. Argon /ND:YAG-KTP laser photocoagulation(ALP)
2. ND:YAG Q-switch laser Anterior Hyaloidotomy
3. CPC

41. CYCLOPHOTOCOAGULATION
• Laser is delivered indirectly (scleral), directly(endoscopy)
• Indicated in refractory glaucoma to medical therapy, outflow
surgeries, painful eyes, eyes with no or little vision
• ECP is gaining popularity for treatment of refractory glaucoma
• Between 2005 and 2012 ,increased by 99%

42. LASER IN IRIS AND PUPIL
• Puplloplasty
• Photomydriasis
• Synechiolysis
• Persistent fetal vasculature
• Corticolysis
• membranectomy

43. Lens surgery
• In 1748 , first report of cataract surgery
• Phacoemulsification by Kelman
• Recently, femtosecond laser-assisted cataract surgery(FLACS)
Can occur in different stages of the procedure
• To create the main and side port corneal incisions
• In astigmatic keratotomies
• In anterior capsulotomy
• In fragmentation of the cataract nucleus

45. • Others lens surgery
1. Repositioning of posterior chamber intra-ocular lens
2. Pigment ND:YAG Q switch laser sweeping, anterior capsuloplasty

46. Laser in vitreous
• The treatment decision is made upon identification of vitreous in A/C
• In 1983, Katzen et al . Described the use of Nd : YAG 1064 nm Q-
switch laser (QS-YAG) for cutting vitreous strands.
• Contraindicated in photopsias, or untreated retinal pathology, active
intraocular inflammation, or uncontrolled OHT
• IN 1985, Laser vitreolysis by means of QS-YAG pulses was first
described by Frankhauser ,
• Posterior vitreolysis is usually an options in patients whom pars plana
vitrectomy is contraindicated or has to be postponed
• Indicated in removal of symptomatic vitreous opacities in optic axis

47. • Removal of vitreous traction over retina
• Facilitation of vitreous hemorrhage clearing

48. Diagnostic laser
optic coherence tomography (OCT)
• Produces real time , non contact, high resolution, cross –section
images of the retina ,optic nerve and anterior segment structures
• OCT technology started with time domain, the newer generationof
commercial OCT designed as a spectral domain
• Is capable of acquiring small sizable image over short period of time
• OCT systems uses a laser beam in the near infra –red range
• An equipment that is associated with OCT uses low beam energy blue
laser that asses autofluorescent RPE

49. swept source OCT (SS-OCT)
• Based on fourier transform, uses a short cavity –swept tunable laser
• Able to emit different frequencies of light
• A narrowband 1050nm laser light source is used which have a longer
wavelength than SD-OCT(840nm), allowing deeper tissue penetration
with less scattering
• Also permit imaging through media opacity, e.g cataract
• Uses photodetectors that allows increase in axial resolution 1um

50. confocal scanning LASER ophthalmoscope-cSLO
• In 1980s , Pomeranzeff and Webb
• Proposed a way of imaging the retina using less light than indirect
ophthalmoscopy/ photography
• SLO consists of scanning the fundus with a very narrow beam and
detecting the reflected light with a high sensitivity detector (one pixel
detector)
• It has the ability to produce rapid images at low light levels using
specific wavelength

51. optical coherence Tomography Angiography
• The first widely available OCTA device is the RTVue XR Avanti (Optvue
inc, Fremont, California, USA)
• This instrument has a A –scan rate of 70,000 scans per second, a light
source centered on 840nm bandwidth of 50nm
• Tissue resolution is 5mm axially and 15mm beam width
• Two image sets are performed
• Other platform are now beginning to emerge like Zeiss AngioPlex(Carl
Zeiss Meditec AG,Jena, Germany), spectralis OCT Angiography
(Heidelberg Engineering, Dossenheim, Germany)

59. FEMTOSECOND LASER
• Development of the femtosecond laser was another revolutionary
step in refractive surgery
• It was pioneered by Kurtz et al in 1998 and later commercialized by
IntraLase Corporation
• The high –power, low-exposition time (femtosecond ) laser causes
plasma – induced-ablation via optical breakdown
• 2 Categories higher energy-lower frequency, lower energy high
frequency Femtosecond laser that are used for LASIK procedures are
solid-state focusable plasma photoablative laser that operate in the
infrared spectrum at wavelength of approx. 1000-1053nm

62. LASER IN RESEARCH
laser Doppler Flowmetry
• In Vivo confocal microscopy of the cornes
• Pupillometry- 1960 in psychology and psychiatric studies
• Adaptive optics
• Clinical applications of intraoperative OCT

69. • Excimer lasers-used in LASIK , a Term coined by Pallikaris et al in 1991
• Femtosecond laser from use of mechanical microkeratomes
• Subthreshold micropulsed laser still under study , it works by limiting
progression of laser scars
• Nanosecond laser(2RT ELLEX)-A new frequency doubled nanosecond
ND-YAG laser 532nm with discontinuous beam energy, was recently
developed is being investigated as retinal rejuvenation therapy for Tx
of DME,AMD
• LASER delivery with eye tracking
• Laser based imaging technique, OCTA, SS-OCT

70. Reference
• MANUAL OF LASER IN OPHTHALMOLOGY 2017