Direct ophthalmoscopy is performed as part of a routine examination by an ophthalmologist. This is important for determining the health of the retina and vitreous. There are three main steps to performing a fundus examination - pupil dilation, wide angle fundus examination, and a magnified view of underlying lesions and abnormalities.
An ophthalmoscope is used in this activity to examine the fundus and rule out diabetic or hypertensive retinopathy.
Normal ophthalmoscopy findings
The optic nerve head or disc is visible when the pupil is viewed at an angle of about 15 degrees to the optical axis (the patient's line of sight is "straight ahead"). The disc is a yellow-pink color that stands out from a redder, browner, or more orange retina. The disc is sharply demarcated temporally and to a lesser extent nasally from the background retina, which is a retina that is not a disc, vessels, or macula. Often a narrow crescent of the pigmented spot is adjacent to the sides of the disc, especially the temporal side. The width of the disc is slightly greater than the height. The central part of the disc is paler and is called the blind spot; this usually occupies less than one third of the disc diameter. With glaucoma and with high myopia, the blind spot increases.
The transverse diameter of the disc is a standard criterion in the description of the bottom, so that, for example, a lesion can be characterized as: the diameter of half a disc at two o'clock" and the elongation of two disc diameters exceeding it. Near the middle of the disc, the central artery and vein emerge from the optic nerve, with which they run forward into the orbit. Each of them quickly bifurcates into upper and lower branches that run "flat", that is, parallel to the surface of the retina. In addition to the same disc diameter, they are called arterioles and venules. In all retinal vessels, arteries appear slightly smaller and distinctly lighter, more orange-red and less purple than veins. The difference in color reflects the visualized blood column: transparent vessel walls and deoxygenated venous blood are darker than arterial blood. At the edge of the disc, each large vessel divides into nasal and temporal branches. Thus, the major arteries, veins, and quadrants of any retina are superior temporal, inferior temporal, inferior nasal, and superior nasal.
The macula is the region of greatest visual acuity. Beyond this zone, the background color of the retina will parallel the patient's skin and hair pigmentation, ranging from pale in fair-skinned blonds to dark in the darkest blacks.
For successful ophthalmoscopy, it is important that the patient is comfortable during the examination. When relaxed, the patient will be more cooperative.
The doctor will ask the patient to look at a distant target, preferably an overview chart, and advise him to remain still and focus on that spot and "pretend" that he can still see it, even if the doctor obscures it with his head. The patient also needs to be given permission to blink as needed. It is best if the examination is carried out in low light conditions to improve contrast. The left eye and left hand should be used to examine the patient's left eye. The field of view of the bottom is increased, the closer the doctor is to the patient's eyes, the better for low myopes and low hypermetropes, it is better for them to remove their glasses. However, for myopes and hypermetropes above ±3.00DS and for astigmats above 2.50DC, it is recommended to keep glasses in order to overcome the problems associated with magnification, minimization and distortion, respectively. The additional reflexes created by spectacle lenses will be distracting at first, but can be overcome with practice.
Method of examination:
- Using a large diameter hole and looking around the sides of the ophthalmoscope, the doctor will examine the external features of the eye. This applies to eyelashes, eyelid margins, conjunctiva and sclera. He also observes the color of the iris, the size and regularity of the pupil.
- The clinician dials a +10DS lens into the lens wheel and observes the eye from 10 cm. Examines the red reflex in particular as this provides an excellent way to detect any corneal opacity. Any dark spots or irregularity in the normal, uniform red reflex indicates opacity of the cornea, anterior chamber, or vitreous. The doctor monitors the Mittendorff point, which is a small congenital opacity often present in normal healthy eyes.
- When examining the red reflex, the doctor will ask the patient to look up or down a little. If, when the patient looks up, the opacity seems to be moving in the same direction in the red reflex, then it must lie in front of the plane of the pupil (i.e., the cornea or anterior chamber). The one that remains stationary should be, for example, in the plane of the pupil, and the one that moves in the opposite direction from the patient's gaze should lie behind the plane of the pupil (i.e., the posterior lens or vitreous).
- During ophthalmoscopy, it is advisable to keep both eyes open and suppress the image from the other eye. This may require some practice.
- The doctor slowly approaches the patient and at the same time gradually reduces the power of the lens in the wheel and focuses on the lens, the vitreous, and finally on the fundus. The power of the lens required to focus on the bottom will depend on any unsatisfactory refractive error of the patient and observer, as well as patient or observer placement. Once a blood vessel at the bottom has been found, the doctor moves along it and finds the point where it branches and moves the field of view in the direction that the top of the branch points.
- Moving along the blood vessel in this way, the optical disk will be located. The ophthalmologist will need to consider its color, its fields. You also need to pay attention to the presence of any pigment, choroidal or scleral crescent around the disc.
- Retinal blood vessels should be examined in each quadrant after disc location. The veins are relatively large and dark red, while the arteries are relatively thin and pale.
- The clinician then looks at the disc and moves towards the nose to view the patient's visual axis. In this position, it will obscure the purpose of fixation by causing the pupils to constrict, blinding the patient and noticing some unpleasant corneal reflexes. These factors make the macula a difficult area to visualize. It may be useful to use a beam with a smaller aperture. The normal macula is the area between the arcades of the superior and inferior temporal blood vessels, and the center is the fovea.
- Finally, the doctor will ask the patient to look in eight main directions so that he can see the peripheral bottom - "look up" to see the periphery and so on. In a young patient with a large pupil, it is possible to reach the equator of the eye. The clinician will need to slightly adjust the lens on the wheel as the periphery is closer to it than the optical disc requiring more focusing power (plus the lens).
Direct ophthalmoscopy is a routine part of the examination of every doctor, not just an ophthalmologist. It consists solely of inspection. The doctor looks through the fundus of the eye with an ophthalmoscope, which is just a light with various optical modifications, including lenses. The ophthalmoscope illuminates the retina through the normal diaphragm, which is the pupil. The light rays that form the image of the retina reappear through the pupil. The viewing aperture (window) of an ophthalmoscope contains a lens that changes light beams to assist the user. This procedure looks at the structures that lie in the innermost layer of the eyeball: the retina, the retinal blood vessels, the optic nerve head (disc) and, to a limited extent, the inferior choroid.
The pupil is often dilated pharmacologically to facilitate examination of the retina and examination of the macula. One paralyzes the pupillary muscle and the tip of the iris muscles with non-absorbable short-term parasympatholytic drugs, resulting in greater pupillary dilation. Compared to an ophthalmologist, a general practitioner, neurologist or pediatrician concentrates in particular on fundoscopic manifestations of systemic disease and less on local eye disease. Only ophthalmologists perform retinoscopy and indirect ophthalmoscopy, which require different equipment and provide different information.
Direct ophthalmoscopy reveals:
- normal fundus;
- hypertensive retinopathy;
- retinal vein occlusion.
Direct ophthalmoscopy is still the method of choice for fundus examination in ophthalmic practice.
Ophthalmoscopy provides the only means for direct examination of the arteries, veins, or central nervous system in an intact, living patient. The detection of papilledema, usually reflecting increased intracranial pressure, is a medical emergency. Treating its cause will prevent permanent neuronal damage and somatic death. The absence of optic disc edema does not mean that everything is fine, since its development does not occur immediately after an increase in intracranial pressure. However, visible retinal venous pulsations rule out elevated intracranial pressure, which is vital in assessing any condition with headaches, developing neurological conditions, or head trauma. Loss and reappearance of pulsation quickly reflect changes in intracranial pressure. It is important to note that absent pulsations do not necessarily mean increased intracranial pressure.
Retinal hemorrhages occur in a variety of conditions, including endocarditis, pernicious anemia, diabetes mellitus, leukemia, subarachnoid hemorrhage, and disseminated intravascular coagulation (DIC). They always deserve attention in diagnosis and treatment; their appearance may lead to an initial diagnosis or assessment of progression. In severe hypertension, the detection of retinal hemorrhage redefines the condition as complicated hypertension; no blood pressure measurement can do that. Often this means being treated in an intensive care unit. Prevention of early death, preservation of kidney function and the possibility of subsequent outpatient care reward the examiner's skill.
Chorioretinal lesions of some infections are themselves diagnostic. Candidal exudates indicate endophthalmitis in a patient with suspected systemic candidiasis. Cytomegalovirus in an AIDS patient has a very characteristic appearance, which consists of mixed hemorrhages and yellow granular exudates that are often centered on vessels. Toxoplasmosis and histoplasmosis of the eye also have distinct, though not pathognomonic, features when examined by ophthalmoscopy. Miliary tuberculosis can be confirmed by identifying the choroidal tubercles.
Proliferative diabetic retinopathy is a major cause of blindness, but can be treated with laser photocoagulation. Ophthalmoscopic recognition of preproliferative lesions or frank neovascularization will lead to measures to prevent its occurrence, and its typical consequences of retinal and vitreous hemorrhage and permanent blindness. Diabetic nephropathy rarely occurs without diabetic retinopathy, so a normal retina in a nephrotic diabetic will stimulate the search for non-diabetic causes of kidney disease, thus improving the selective and efficient use of diagnostic resources.
In cerebrovascular disease, ophthalmoscopic examination provides the data needed for management. If the examiner sees fragments of atheroma affecting retinal arterioles, he knows that they did not originate in situ, since this vessel caliber does not experience atherogenesis. Therefore, they were embolized in a more proximal region such as the aorta or carotid artery. Most cerebrovascular tests measure brain structure, blood flow, or pressure; they can all remain normal if the ulcerated plaque occurs without critical arterial stenosis; carotid arteriography is an exception, but its hazard, discomfort, and cost put it off in highly selected cases, so the need to use fundoscopy for screening is emphasized.