Examination of the Lens
The ophthalmologist uses a slit lamp to examine the lens. The eye can also be examined with a focused light if necessary.
Direct illumination will produce ared reflection of the fundusif the lens isclearand gray shadows if lens opacities are present. The examiner then illuminates the eye laterally with a focused light held as close to the eye as possible and inspects the eye through a +14 diopter loupe (see Fig. 1.10). This examination permits better evaluation of changes in the conjunctiva, cornea, and anterior chamber. With severe opacification of the lens, a gray coloration will be vis-ible in the pupillary plane. Any such light-scattering opacity is referred to as a cataract.
Indirect ophthalmoscopy is usually performed by the ophthalmologist and produces a laterally reversed image of the fundus. Less experienced examiners will prefer direct ophthalmoscopy. Here, the oph-thalmoscope is held as close to the patient as possible (Fig. 1.13; see also Figs. 12.4b and c). Refractive errors in the patient’s eye and the examiner’s eye are corrected by selecting the ophthalmoscope lens required to bring the retina into focus. The examiner sees an erect, 16 power magnified image of the ret-ina. The examination should be performed in a slightly darkened room with the patient’s pupils dilated. Students should be able to identify the optic disk. In a normal eye, it is sharply defined structure with vital coloration (i.e., yel-lowish orange) at the level of the retina and may have a central excavation. The central vein lies lateral to the artery; venous diameter is normally 1.5 times greater than arterial diameter. Each vascular structure should be of uni-form diameter, and there should be no vascular constriction where vessels overlap. A spontaneous venous pulse is normal; an arterial pulse is abnormal. Younger patients will have a foveal and macular light reflex, and the retina will have a reddish color (see Fig. 12.8). An ophthalmologist should be con-sulted if there are any abnormal findings.