What is the principle of indirect ophthalmoscope?
In summary, the purpose of the ophthalmoscopy lens in indirect ophthalmoscopy is to redirect diverging pencils of light emerging from the patient’s pupil toward the observer’s eye. In doing so, the lens also focuses parallel rays within each pencil into an inverted aerial image of the patient’s fundus.
What are the parts of the ophthalmoscope?
The ophthalmoscope consists of a head and a handle (Figures 4-8 and 4-9). The head contains viewing lenses and beam selection controls. The viewing lens control (lens wheel) is used to focus the instrument.
What is the difference between direct and indirect ophthalmoscopy?
Direct ophthalmoscopy one that produces an upright, or unreversed, image of approximately 15 times magnification. Indirect ophthalmoscopy one that produces an inverted, or reversed, image of 2 to 5 times magnification.
Why is it called indirect ophthalmoscope?
The process is “indirect” because the fundus is viewed through a hand held condensing lens.
What is a 20D lens used for?
|Table 1. Indirect Lenses and Their Typical Use|
|20D||View the retina including periphery using a head-mounted BIO||Higher magnification than 28D. Ideal for pediatric examination, when scleral indentation is required and for patients with nystagmus. Useful when slit lamp examination is not possible.|
What are the two types of ophthalmoscope?
There are two main types of ophthalmoscopes: direct and indirect. Direct ophthalmoscopes are simple hand-held ophthalmic instruments consisting of a concave mirror, a light source, an eye piece for the ophthalmic professional conducting the examination, and a simple handle.
What are the types of ophthalmoscope?
There are different types of ophthalmoscopy.
- Direct ophthalmoscopy. You will be seated in a darkened room.
- Indirect ophthalmoscopy. You will either lie or sit in a semi-reclined position.
- Slit-lamp ophthalmoscopy. You will sit in a chair with the instrument placed in front of you.
What is direct ophthalmoscopy used for?
A direct ophthalmoscope, or simply an ophthalmoscope, is a hand-held optical instrument used to inspect the fundus or back of the eye.
Why is indirect ophthalmoscopy preferred over direct ophthalmoscopy?
The indirect ophthalmoscope offers some advantages over the direct ophthalmoscope: It permits binocular vision with depth perception (stereoscopic vision). It has a wider field of view. It can be combined with scierai indentation to examine the anterior retina.
What does fundoscopy test for?
Fundoscopic / Ophthalmoscopic Exam. Visualization of the retina can provide lots of information about a medical diagnosis. These diagnoses include high blood pressure, diabetes, increased pressure in the brain and infections like endocarditis.
Why is fundoscopy done?
Fundoscopy may be used to check for eye problems, such as glaucoma, macular degeneration, eye cancer, optic nerve problems, or eye injury. Also called funduscopy and ophthalmoscopy.
Which lens is used in ophthalmoscope?
The viewing system of the instrument (Figure 2) consists of a pair of low-powered convex lenses. This design affords the examiner a stereoscopic view of the virtual image. The +20D lens is the standard lens for general examination offering 3x magnification and a field of view of approximately 45°.
What is magnification of 20D lens?
The magnification of a specific BIO lens is crudely determined by 60/the power of lens. Thus, a +20D lens would have a magnification of 60/20= 3X. 20D lens is the most commonly used lens for BIO in adults.
What is ophthalmoscope used for?
Ophthalmoscopy (also called fundoscopy) is an exam your doctor, optometrist, or ophthalmologist uses to look into the back of your eye. With it, they can see the retina (which senses light and images), the optic disk (where the optic nerve takes the information to the brain), and blood vessels.
Which mirror is used in ophthalmoscope?
Concave Mirror Uses in the Ophthalmoscope Concave mirrors are used in optical instruments such as Ophthalmoscope. Ophthalmoscope consists of a concave mirror with a hole in the centre.
Which lens is used in direct ophthalmoscope?
Most modern ophthalmoscopes utilize a prism in place of a mirror for this purpose. Condensing Lens: These are aspheric lens with ranges varying with every ophthalmoscope model. Eg. +1-10, +15, +20,+40 and -1-10,-15,-20,-25,-35 in the Heine beta 200.
What are the advantages of direct ophthalmoscope?
Advantages of direct ophthalmoscopy have traditionally included (1) a 15× magnified view of the posterior pole that facilitates appreciation of small, dynamic changes of the ocular fundus, such as venous pulsations and circulatory changes; (2) wide availability and portability—the direct ophthalmoscope is easily …
What are the advantages of using indirect ophthalmoscope?
The monocular indirect ophthalmoscope (or PanOptic) allows a five times greater area of the fundus to be viewed than with direct ophthalmoscopy. With this instrument it is possible to view beyond the equator when the patient has dilated pupils.