Douthwaite, W. A.
Special Skills and Techniques. Gretchen Beal Van Boemel. Thorofare, NJ: Slack Inc. 1999. Pages: 272. Price: $30.00. ISBN 1-55642-349-7.
This book is written primarily for ophthalmic and optometric assistants. The foreword suggests that assistants may be expected to perform some techniques with little or no prior knowledge. The author has attempted to deal with this problem by describing techniques in a manner that introduces each topic.
The techniques covered in Chapter 1 include exophthalmometry, pachymetry, corneal topography, pupillometry, pupillography, and ophthalmoscopy. This is an extensive list for a single chapter and it is no surprise that each topic is dealt with at only a superficial level. The description of the videokeratoscope is very basic and no description of keratometers is included. The section on ophthalmoscopy is also very general and contains surprising statements like “ophthalmoscopy is the examination of the posterior chamber of the eye” and “… there are two apertures in a direct ophthalmoscope for large and small pupils.” The only indirect ophthalmoscope described is the head-mounted binocular arrangement. This chapter makes it obvious that this book is not a “how-to” manual; rather, it is a basic introduction to the techniques described, sometimes using terminology that an optometrist might consider inappropriate.
Chapter 2 is an introduction to psychophysical testing. It describes color vision testing, dark adaptometry followed by descriptions of the potential acuity meter and tests for glare. There are a number of mistakes and surprising statements in this chapter. For example, Fig. 2.28 shows the Pelli-Robson chart but is described as an ETDRS style chart. Color arrangement tests are described as “qualitative not quantitative,” yet the author goes on to discuss scoring for the 100-Hue test.
Chapter 3 is an introduction to microbiology, but the remaining chapters deal with techniques with which the author seems to have more direct experience and consequently include more detail. Chapter 4 considers Ultrasound A-scans for determination of the axial length of the eye and intraocular lens powers. The descriptions are at a technician level, which was the declared intention of the book. The author now describes what to do but does not investigate the fundamental principles underlying the measurements. This means that the advantages, disadvantages, and limitations of the techniques may be difficult to appreciate. Variations of instrument design are considered for the first time. The earlier part of the book gives the impression that there is only one type of videokeratoscope, for example. The description of IOL power calculation simply states that there are a number of equations available but does not give a single example.
Chapter 5 covers diagnostic A and B-scan ultrasonography. There is considerable repetition of the information in Chapter 4, but there is also a detailed explanation of standardized echography. This chapter also includes some useful ultra-scan pictures.
Chapter 6 describes the electroretinogram (ERG). Only full field (Ganzfeld) flash ERG is considered. The only quantification of stimulus parameters is given as 5 to 10 foot-lamberts as the brightness required for light adapting the eye. The stimulus is described simply as bright or dim. More guidance on stimulus parameters and amplifier settings would have been useful. The neophyte technician might appreciate, for example, some information on the high- and low-frequency filters used by the amplifier combined with a discussion of what these filters do. Clinical ERG recordings illustrate the ERG response in a number of ocular diseases.
Chapter 7 describes Electro-oculography and illustrates recordings from a number of ocular diseases. Quantification of stimulus and recording parameters would have been helpful.
Chapter 8 describes the visually evoked response to both flash and pattern reversal. Again, there is little information concerning stimulus and recording parameters. The electrode impedance value is stated to be less than 5 without any indication of units. This chapter includes some VER clinical recordings that illustrate the diagnostic potential of the technique.
Appendix A discusses who qualifies for disability benefits. Appendix B describes the universal precautions to avoid inadvertent patient exposure to blood-borne pathogens and ocular surface antigens. The book finishes with a useful index.
The book suffers from a lack of color prints. There are very few typographical errors but there are a number of printing errors, which result in missing text, duplication of the text, or in text appearing in an inappropriate position. The author has an easy-to-read style. There are one or two references at the end of some of the chapters. There is a small bibliography at the end of the book.
This book is a basic introduction to some of the techniques used by optometrists and ophthalmologists. It cannot be considered to be an instruction manual for someone actually intending to perform the techniques described.