Albert Jakobiec Ophthalmology Pdf
Diagnosing retinal disease requires a combination of careful clinical examination and specialized imaging techniques. The macula can be examined without pupillary dilation, but, to perform a complete retinal examination, the pupil should be fully dilated. Pupil dilation is accomplished through a variety of pharmacologic agents, including 1% tropicamide, 2.5% phenylephrine, and 1% cyclopentalate.
In general, longer-acting dilating agents are not required.The simplest examination technique is using the direct ophthalmoscope, which provides an upright, monocular, high-magnification (15 ×) image of the retina. However, the instrument’s lack of stereopsis, small field of view, and poor view of the retinal periphery limit its use. These shortcomings are overcome by using the binocular indirect ophthalmoscope (BIO) in combination with a handheld magnifying lens that dramatically increases the field of view with lower magnification (2–3 ×).
The inverted, binocular image of the retina that these provide allows examination of most of the retina; however, to see the entire retina (especially pathology near the ora serrata), the BIO examination needs to be combined with scleral depression. In general, 20, 28, and 30 D lenses are used to view the retina. Because the field of view is inversely proportional to the power of the lens, the 30 D lens has the widest field of view and lowest magnification. An easy way to correct for the image reversal is to turn the page upside down when you are drawing the retina, and draw the retina and pathology as seen through the lens; this will make the drawing correctly depict what you see.Magnification of even the lowest power BIO lens is insufficient to evaluate subtle retinal changes or abnormalities of the vitreous body. To evaluate these structures, slit-lamp biomicroscopy is required. A variety of lenses are available for viewing the retina with the slit lamp. Contact lenses offer the advantage of better stereopsis and higher resolution.
They require topical corneal anesthesia and are placed directly on the cornea to eliminate its power and the cornea–air interface. Fluids used range from contact lens wetting solutions to viscous clear gel solutions. The more viscous the solution, however, the more it interferes with the quality of any photography or angiography performed shortly after the examination. In contrast, non–contact lenses use the power of the lens in combination with the cornea to produce an inverted image with a wider field of view. The biconvex indirect lenses used with the slit lamp do not touch the cornea, and thus topical anesthesia is not necessary. In general, high-plus optical power lenses such as the 60, Super66 (which has a 1:1 image magnification; Volk Optical, Mentor, OH), 78, and 90 D lenses are used; however, more specialized lenses have been developed, including the SuperField, Super VitreoFundus, SuperPupil, Digital Wide Field, and Digital HighMag (all from Volk Optical) and the Ocular Maxfield lenses (Ocular Instruments, Bellevue, WA).
In general, lenses with lower diopter power offer more axial resolution and better stereopsis. Non–contact lenses are easier to use and offer more rapid evaluation of the retina. Finally, a Hruby lens, an external planoconcave lens with high negative optical power attached to the slit-lamp frame, is another option if a contact or non–contact lens is not available. Like the biconvex indirect lenses, it does not require topical anesthesia or placement of other drops on the cornea. Although the Hruby lens does not give an inverted image, it is less versatile than the biconvex indirect lenses for viewing outside the fovea.Detection of retinal thickening in macular edema, cystic spaces in cystoid macular edema, or subretinal fluid in choroidal neovascularization (CNV) is enhanced by using a thin slit beam, ideally at a 45 ° angle, and a biomicroscopic lens with high magnification. The inner aspect of the beam is directed at the surface of the retina and retinal vessels, the outer aspect at the RPE. The distance between the inner and outer aspects is recognized as the thickness of the retina.
Once the normal thickness of the retina is known for a given location within the macula, abnormal thicknesses may be evaluated in other areas. The same technique is useful for determining the level of hemorrhage—preretinal, intraretinal, or subretinal.
Careful examination of the beam as it hits the retina can differentiate between elevation or depression of a retinal lesion. Transillumination is another technique that may help highlight cystic changes of the neurosensory retina or help detect pigment epithelial detachments where the edge of the beam appears to glow.
Red-free (green) light may be used to help detect small vessels (such as intraretinal microvascular abnormalities or retinal neovascularization) or dots of hemorrhage that may be difficult to see against an orange background when viewed with the normal slit beam. A lighter color to the retina on red-free light may correspond to the presence of fluid, fibrin, or fibrous tissue associated with CNV. Examination of the retina: ophthalmoscopy and fundus biomicroscopy. In: Albert DM, Miller JW, Azar DT, Blodi BA, eds. Albert & Jakobiec’s Principles and Practice of Ophthalmology. Philadelphia: Saunders; 2008:chap 127.
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Albert Jakobiec Ophthalmology Pdf Template
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