Abstract
The goal of this chapter is to provide the clinician with an understanding of binocular indirect ophthalmoscopy (BIO) and helpful clinical techniques for success in examining the fundus of the pediatric patient, including scleral depression. The challenging technique to examine the premature infant at risk for retinopathy of prematurity will be explained in detail, including the standard classification of the disease with photos depicting the different location and stages of disease. BIO with the addition of scleral indentation helps the clinician diagnose and locate lesions that may otherwise go undetected, such as retinal holes, tears, or vitreoretinal adhesions. Complete examination of the fundus of a child is no less important than of any other patient who seeks eye care but often requires efficiency and precision (as well as many human arms). Time is a rate limiting aspect when examining children so preparation and experience will lead to success.
TopBinocular Indirect Ophthalmoscopy (Bio)
Background
Binocular indirect ophthalmoscopy (BIO) consists of a headband apparatus, optical viewing system, and rheostatically controlled illumination source (Figure 1). The light beam from the BIO is directed into the child's eye which produces reflected observation beams from the retina. With a high plus powered condensing lens, these beams create an aerial image at its focal distance in front of the patient's eye (Figure 2). The resultant image is real, magnified 1.5x to 3.5x, reversed left to right, inverted top to bottom, and located between the examiner and the condensing lens (Figure 3).
Figure 1. Binocular indirect ophthalmoscopy (BIO) components: headband, optical viewing system and illumination source
Figure 2. BIO optics: light beams directed into patient's eye, create reflected beams from the retina focused to an aerial image with a condensing len
Figure 3. The BIO plus condensing lens creates a real, magnified, reversed, inverted aerial fundus image
The headband provides proper support with adjustable controls. There are various styles based on manufacturing company. The ocular lens system has knobs that are adjustable to line up with the examiner's pupil distance (PD). Prisms are incorporated into the instrument to create a stereoscopic view. The two images of the examiner's pupils and of the light source are located inside the patient's dilated pupil for 3D viewing. The small pupil BIO allows passage of these points through an undilated pupil and is better for undilated pupil retinal exam or those who do not dilate fully.
The BIO condensing lens is double aspheric lens with antireflective coating. It is available in various powers, including +15D, +20D, and +28D. When the lens provides a larger field of view (FOV), the magnification is decreased and vice versa. For example, the +28D provides a larger FOV compared to 20D, which has a larger FOV compared to +15D. The +15D lens has the smaller FOV but a higher magnification compared to the other two lenses. During examination, the more convex lens surface faces toward the examiner, less convex surface faces the patient's eye. While differences exist between manufacturers, the standard +20D condensing lens typically produces about 2.5x-3x magnification and a 35-45 degree or eight-disc diameter FOV (Casser et al., 1997a). This is in comparison to a direct ophthalmoscope, which produces about 15x magnification and a two-disc diameter fundus FOV. These lenses can be clear or amber color. Amber or yellow lenses appear to increase patient comfort by reducing scattered light. Different clinicians will have different preferences relative to fundus color perception with the two different types of lenses.
Clinical Pearl: +28D and +20D lens are helpful in a pediatric exam and screening patients as it allows for quick, wide view of the retina. Clinicians can view a large retinal area at one time to rule out any obvious gross disease. Clinician preference drives the choice between these two lenses but the 28D lens provides a view of the macula and the optic nerve at once while the magnification with the 20D lens allow for greater detail of these structures.
Key Terms in this Chapter
Gestational Age (Menstrual Age): Is the time between conception and birth. It is measured in weeks, from the first day of the woman's last menstrual cycle to the current date. A normal pregnancy can range from 37 to 42 weeks. Gestational age can be determined before (with ultrasound) or after birth (look at baby's weight, length, head circumference, vital signs, reflexes, muscle tone, posture and condition of the skin and hair).
Oxygen Therapy: Is used to assist in raising blood oxygen levels for the development of organs but need to be titrated carefully to prevent end organ damage, such as retinopathy of prematurity.
Vascular Endothelial Growth Factors (VEGF): Are substances made by cells that are important in new blood vessel development. They are also associated with pathologic angiogenesis.
Retinopathy of Prematurity (ROP): A retinal disorder caused by abnormal blood vessel growth in premature infants.
Vasculogenesis: Process involves the proliferation, differentiation, and organization of blood vessels from endothelial progenitors and angioblasts (angiogenesis).
Postmenstrual Age: Is the time elapsed between the first day of the last menstrual period and the birth (gestational age) plus the time elapsed after birth (chronological age).
Chronological Age (Postnatal Age): Is the time elapsed after birth.