视觉光学手册：仪器与视力矫正

需积分: 9 28 浏览量更新于2024-07-18 收藏 28.95MB PDF 举报

"Handbook of Visual Optics Volume Two" 是一本深入探讨生理光学的权威书籍，由Pablo Artal编辑。该书分为两卷，第二卷专注于"Instrumentation and Vision Correction"，结合了物理学、医学、生物学、心理学和工程学的多学科知识，详细阐述了眼睛与视觉矫正的科学和技术。在视觉光学这一领域，这本书覆盖了广泛的主题。首先，它探讨了眼睛和视网膜的光学原理，包括眼球的结构和功能，以及光线如何通过这些结构在视网膜上形成图像。这些基本的光学概念是理解视觉系统工作方式的关键，包括透镜、折射和成像理论。接着，书中详述了先进的眼科仪器，如眼底相机、共焦显微镜和光学相干断层扫描（OCT）等，这些设备在现代眼科研究和临床实践中扮演着重要角色。读者将了解到这些工具如何用于检测和诊断各种眼部疾病，以及它们如何帮助科学家更深入地理解视觉过程。此外，本书还关注了视觉矫正技术，包括眼镜、隐形眼镜和角膜塑形术等。这部分内容不仅介绍了这些矫正方法的工作原理，还讨论了它们在不同视力问题中的应用，如近视、远视和散光的矫正。同时，书中还涉及了视觉矫正手术，如激光视力矫正手术（如LASIK），以及这些手术的适应症、风险和效果。书中的章节还涉及了视觉感知的神经生物学机制，揭示了眼睛光学与大脑如何处理和解码视觉信息的关系。这包括对对比敏感度、颜色视觉、立体视觉等视觉功能的分析，以及视觉感知与环境、年龄和个体差异的影响。对于研究人员和学生，本书提供了丰富的实验设计和数据分析方法，包括使用MATLAB软件进行模拟和数据处理的示例。尽管MATLAB商标的使用得到了许可，但书中并未对其准确性作出保证，而是鼓励读者根据自己的需求和实验条件灵活应用这些工具。《视觉光学手册》第二卷是一本综合性的参考书，对于那些希望深入了解视觉科学、光学成像和视觉矫正技术的人来说，无疑是一份宝贵的资源。无论是眼科医生、科研人员，还是相关专业学生，都能从中受益匪浅，获得对视觉系统的深入理解和实践操作知识。

Light safety

Ken Barat

Contents

1.1 Introduction 4

1.2 Why all the concern over lasers? 4

1.3 Continuous wave 4

1.4 Pulsed lasers 4

1.5 Hazard classication 5

1.5.1 Class 1 5

1.5.2 Class 1M 5

1.5.3 Class 2 6

1.5.4 Class 2M 6

1.5.5 Class 3R (once known as 3A) 6

1.5.6 Class 3B 6

1.5.7 Class 4 6

1.5.8 Class 1 product (sometimes referred to as an embedded laser system) 6

1.6 Common medical laser wavelengths 6

1.6.1 Laser safety items 7

1.6.1.1 Appointment of a laser safety ocer 7

1.6.1.2 Laser protective eyewear 7

1.6.1.3 Signage 7

1.6.1.4 Operating procedures 7

1.7 Biological eects 7

1.7.1 Maximum permissible exposure 7

1.7.2 Nominal ocular hazard zone 7

1.7.3 Damage mechanisms 8

1.7.3.1 Electromechanical/photodisruption/acoustic damage 8

1.7.3.2 Photoablation 8

1.7.3.3 ermal damage 8

1.7.3.4 Photochemical damage 8

1.7.3.5 O-axis laser damage 9

1.7.4 Ultrafast laser injury 9

1.7.5 Laser radiation eects on skin 9

1.7.5.1 Epidermis 9

1.7.5.2 Dermis 9

1.7.5.3 Subcutaneous tissue 9

1.7.5.4 Skin eect by wavelength 9

1.7.6 Optics 11

1.7.6.1 Increased hazards when using optics 11

1.8 Aided viewing from a ber 11

1.9 Accidents and related events 12

1.10 MAUDE database 12

1.10.1 Report 1: MAUDE DB Iris medical slit lamp report number 2939653-1999-00002 12

1.10.2 Report 2: Alcon Research Ltd/Huntington Acrysof Restor intraocular lens 12

1.10.3 Report 3: Device problem, self activation or keying 12

1.10.4 Report 4: MDR Report Key 4121056 device operated dierently than expected 12

Light safety4

Ophthalmic instrumentation

1.1 INTRODUCTION

e goal of this chapter is to discuss the hazard, in particular

laser light. We will cover a number of topics that the reader may

think they are familiar with, but in the case of safety, repetition is

not a bad thing. In addition, there is coverage of a number of laser

incidents. e author of this chapter hopes that by the end the

reader will have an appreciation for the potential harm they may

be exposed to. A number of resource materials will be referenced,

and the author wishes to thank those individuals who allow open

access to their material.

An awareness of laser safety is extremely important, not

only for the benet of users and ancillary/support sta but also

to answer patient questions and concerns. With the increase

in an aging population comes an increase in eye diseases.

Ophthalmology has responded with technology such as mydriatic

and nonmydriatic fundus cameras, phacoemulsication devices,

femtosecond lasers, supercontinuum light sources, and optical

coherence tomography. ese advances support the need for

understanding an appreciation of laser safety.

1.2 WHY ALL THE CONCERN OVER

LASERS?

With all the hazards one faces during their day, why do we

feel laser safety deserves special attention? While laser light or

radiation has properties that distinguish it from natural light,

the answer is rather simple. Visible (400–700 nm) and near-

infrared wavelengths (700–1400nm) are focused by the lens

of the eye to a spot size an order of magnitude smaller than

that of natural or incoherent visible light, a 300–200µm spot

size to one of 10–20µm. us producing an irradiance (power

per square centimeter) much higher than incoherent light. e

item that gets lost sometimes is while no one expects to look

directly into a laser beam, with this magnication of 100,000

to the macula even a small reection of a laser beam between

400 and 1400nm has the potential to cause some level of

retinal injury.

See Figures 1.1 and 1.2 for a graphic display of this point.

A1mW/cm

beam in is 100 W/cm

at ones macula.

1.3 CONTINUOUS WAVE

Laser systems that can produce uninterrupted laser energy are

called continuous wave (CW) lasers. As long as they are turned

on, a beam of laser light is emitted. By convention, any laser that

emits light for longer than 0.25 s is called a CW laser. External

shutters can be used to “chop” the beam so it has a strobe

appearance, but the output power remains constant even in the

chopped beam. e seemly pulse of the bar code scanner is an

example of a chopped CW laser. e power output of CW lasers

is measured in units of watts.

1.4 PULSED LASERS

Pulsed laser systems emit a beam that is less than 0.25 s in

duration. e 0.25 s demarcation between CW and pulsed

lasers is based on the approximate time for a human reex to

very intense light to work (aversion response). e pulsing in a

pulsed laser system is achieved internal to the laser. Some employ

an electrical “Q-switch” or are “mode locked” to achieve the

shorter pulse widths. e pulse is dened by the pulse width

(oremission duration) and the number of pulses per second

known as pulse repetition frequency. Unlike the CW laser,

all of the energy is emitted in short bursts. e total energy is

compacted into a shorter time interval so the peak energy output

can be very high. is makes shorter pulses more hazardous.

Many pulsed lasers have pulse widths measured in nanoseconds

(1 billionth of a second). Pulse rates to attosecond (10

s) pulse

widths have been routinely produced (but only in vacuum).

A laser must output pulses at a rate faster than 1Hz to be

considered a repetitive pulsed laser. e output is measured in

terms of Joules (Watts × seconds). Turnkey units are available for

the generation of femtosecond laser pulses, 10

With the development and renement of the laser diode,

a highly reliable and convenient laser source became available

for medical applications. A source that is robust and does not

require an in-house service person to keep it running has few

maintenance needs. Many laser systems combine the diode or a

diode array with a ber optic system. e ber optics is used as a

means to deliver the laser radiation without the use of open beam

paths or beam enclosures.

1.10.5 Report 5: MDR Report Key 4105971 ophthalmic femtosecond laser, lensex laser system 12

1.10.6 Report 6: Report Key 4076806 wavelight EX500 excimer laser 12

1.10.7 Report 7: MDR Reporting Key 3735743 Wavelight FS200 femtosecond laser 13

1.10.8 Report 8: MDR Report Key 4124364 Catalys precision laser system ophthalmic femtosecond laser 13

1.10.9 Report 9: Laser re 13

1.10.10 Report 10: Model No. Purepoint LIO nature of problem, malfunction 13

1.10.11 Report 11: Event, negligence 13

1.10.12 Report 12: Device problem, device inoperable 13

1.10.13 Report 13: LASIK eye surgery 13

1.10.14 Report 14: Medlite C6 13

1.10.14.1 Manufacturer response 13

1.10.15 Report 15: Electrical shock 13

1.10.15.1 Manufactures response 14

Bibliography 14

Worth reading references 14

Light safety6

Ophthalmic instrumentation

1.5.3 CLASS 2

Class 2 lasers are visible (400–700nm wavelength) CW and

repetitive-pulse lasers and laser systems that can emit accessible

radiant energy exceeding the appropriate Class 1 AEL for the

maximum duration inherent in the design or intended use of the

laser or laser system, but not exceeding the Class 1 AEL for any

applicable pulse (emission) duration <0.25 s and not exceeding

an average radiant power of 1 mW. Laser systems with invisible

beams cannot be Class 2.

1.5.4 CLASS 2M

Class 2M lasers are limited to visible wavelengths (400–700nm)

at accessible emission levels below the Class 2 AEL for the

unaided eye. However, they can exceed the Class 2 AEL under

optically aided viewing conditions. Class 2M lasers do not exceed

the Class 3B AEL for optically aided viewing.

1.5.5 CLASS 3R (ONCE KNOWN AS 3A)

Class 3R lasers include lasers and laser systems that have

an accessible output between one and five times the Class 2

AEL for visible lasers and the Class 1 AEL for all other lasers,

based on the appropriate exposure duration. The output range

is 1–5 mW.

1.5.6 CLASS 3B

Class 3B lasers and laser systems include the following:

UV (180–400nm) and IR (1400nm to 1mm) lasers and

laser systems that emit accessible radiant power in excess

of the Class 3R AEL during any emission duration within

the maximum duration inherent in the design of the laser

or laser system, but that (a) cannot emit an average radiant

power in excess of 0.5 W (5–500 mW CW) for greater than

or equal to 0.25 s or (b) cannot produce a radiant energy

greater than 125 mJ in 0.25 s.

Visible (400–700nm) and near IR (700–1400nm) lasers and

laser systems that emit in excess of the Class 3R AEL but

that (a) cannot emit an average radiant power in excess of

0.5 W for greater than or equal to 0.25 s and (b) cannot

produce a radiant energy greater than 30 mJ/pulse.

Class 3B lasers are not eye safe. It is hazardous to view the

beam of a Class 3B laser under most conditions. Some may

have a diuse reection hazard. All Class 3B lasers require

some engineering controls and require a danger label/sign.

1.5.7 CLASS 4

Class 4 lasers and laser systems are those that emit radiation that

exceeds the Class 3B AEL. ese lasers can often be re hazards

and have diuse reection hazards.

ey are not considered “eye safe” under any viewing

conditions. Many have hazardous diuse reections and can be

skin and combustion hazard. Class 4 lasers require many more

safety devices and engineering controls.

1.5.8 CLASS 1 PRODUCT (SOMETIMES REFERRED TO

AS AN EMBEDDED LASER SYSTEM)

is is a laser device or product that incorporates a laser, greater

than Class 1 (usually class 3B or 4) inside the unit in such a

way that during normal operation there is no potential for laser

exposure to the operator. During any service or maintenance, this

can all change. ese also have no unique safety requirements

for their use (no extra engineering controls or safety devices). It is

always to ones advantage to use a class 1 product.

1.6 COMMON MEDICAL LASER

WAVELENGTHS

An increasing number of wavelengths are used in medical

applications. is number will only increase over time and

as new medical applications are developed and wavelengths

become available for use. As an example, at one time, the use

of femtosecond lasers would have seen as out of reach in a local

clinic. is would be from an operator knowledge perspective,

maintenance requirements, and cost. But now, femtosecond

Spot size

300–400 µm

Foveal

region

5 m17 mm

Spot size

2 µm

Irradiance

150 W/m

Irradiance

300 million W/m

Extended light source

10 mm

Cornea

Lens

Iris

Retina

100 W lamp

frosted glass

Point light source

1 mW laser

Figure 1.2 Extended and point source power density at the retina.

1.7 Biological effects 7

Ophthalmic instrumentation

laser systems have become available as turnkey systems. Much

of this has to do with the absorption and transmission of various

layers of skin and cellular components as well as the development

of new optics (i.e., nonlinear optics). e following list should

be considered as basic examples of the type of lasers used in

ophthalmology and not all inclusive.

LASER TYPE WAVELENGTH (nm)

Excimer 193,308

Argon ion 488–514

Freq. doubled Nd:YAG

neodymium–yttrium

aluminum garnet

532

Ruby 694

Diode 780–840

Nd:YAG 1,064

Holmium 2,100

Carbon dioxide 10,600

Conditions and procedures one can apply laser technology to

•

Eyelid growths, including lid cancers

•

Histoplasmosis

•

Central serous retinopathy

•

LASIK

•

Cataract surgery

•

Glaucoma surgery

•

Diabetic retinopathy

•

Misdirected eye lashes (trichiasis)

•

Opening up or treating blockage of the opening to the tear

ducts (lacrimal punctum)

•

Benign (noncancerous) growth on the tissue that covers the

surface of the white part of the eye and may grow onto the

cornea (pterygium)

•

Increased eye pressure (glaucoma)

•

Prevention and treatment of attacks of acute glaucoma (laser

iridotomy)

•

Retinal tears and detachment treatment

•

Diabetic retinopathy

•

Treatment of cancer of the eye (such as retinoblastoma)

•

Open-angle glaucoma

1.6.1 LASER SAFETY ITEMS

Laser users need to look toward the American National Institute

Standards Z136 series for user laser safety guidance. If developing

a product, one needs to look at laser safety product regulations

either from the FDA or IEC (outside U.S. requirements). From a

user point of view, there is Z136.1 for Safe Use of Lasers, Z136.3

for Safe Use of Lasers in Health Care Facilities, and Z136.8 for

Safe Use of Lasers in Research, Development, and Testing. e

Laser Safety Ocer (LSO) can choose from these for the control

guidance that ts their use location and setting rather than just

using one of these standards. Regardless when there is a potential

for laser beam exposure, a number of common administrative

safety steps need to be addressed.

1.6.1.1 Appointment of a laser safety ofcer

No facility can say they address laser safety if no one has the title

and responsibilities of the LSO. eir chief role is to put in place

the appropriate control measures and ensure training is delivered

to sta with possible beam exposure. In the clinic setting, this is

usually the physician or senior medical sta person, not the one

who is judged least valuable.

1.6.1.2 Laser protective eyewear

When required, laser eyewear must be labeled with the

wavelength coverage it is designed for and its optical density

(OD) (optical attenuation). As important as correct OD is visual

light transmission, meaning one needs to see while wearing the

eyewear. While laser eyewear is ones last line of defense, its use

when required is critical. is is where having an LSO or MLSO

(Medical Laser Safety Ocer) is critical; one should not count on

vendors for eyewear selection.

Patient eye protection should never be overlooked where

practical.

1.6.1.3 Signage

Posting of the laser use area while it will not prevent an accident,

it is a demonstration of laser safety awareness. Check with the

appropriate standard for signage requirements. e signage needs

to convey what eyewear is required and the class of the laser in

use. Often with mobile medical equipment, the sign and eyewear

travel with the laser cart.

1.6.1.4 Operating procedures

Any time Class 3B or Class 4 lasers or laser systems are in use,

standard operating procedures are required. ey need to be more

than a cookbook work procedure, but indicate hazards and what

controls will be applied to control them. In medical settings, most

SOPs are a combination of pre- and postoperation checklists.

ese checklists need to include safety items, that is, post sign,

perform beam alignment, check eyewear, and communicate laser

hazard to sta in room. Is patient safety in place?

1.7 BIOLOGICAL EFFECTS

1.7.1 MAXIMUM PERMISSIBLE EXPOSURE

From a safety perspective, maximum permissible exposure (MPE)

needs to be dened. In simple terms, it is the exposure limit for

exposure levels to the skin and eye. ese are generally expressed

in J/cm

or W/cm

measured at the cornea. Damage threshold is

generally 5–20 times higher than the MPE. Exposure up to and

including the particular MPE value will not cause injury. e

ocial denition is MPE values are the level of laser radiation to

which an unprotected person may be exposed without adverse

biological changes in the eye or skin.

1.7.2 NOMINAL OCULAR HAZARD ZONE

e distance along the axis of the unobstructed beam from a

laser, ber end or connector to the human eye beyond which the

irradiance or radiant exposure is not expected to exceed the MPE.

ink of it as the starting line of the safe zone or end of the safe

zone if one is closer.

剩余404页未读，继续阅读

possible_11

粉丝: 2
资源: 1

视觉光学手册：仪器与视力矫正

视觉光学手册 第1卷：基础和眼睛光学.pdf

handbook of optical systems, volume 2

Visualization Handbook PDF part 2 of 2

handbook of visual optics

handbook.of.optics

handbook of model checking

handbook of integral equations

master handbook of acoustics

the handbook of research synthesis and meta-analysis pdf

handbook of constraint programming pdf

最新资源

视觉光学手册第1卷：基础和眼睛光学.pdf