What is the use of condensing lens in indirect ophthalmoscope?
Condensing lens is a lens used as an auxiliary lens in indirect instruments to examines the fundus. This lens is used with binocular indirect ophthalmoscope and slit-lamp biomicroscope to reach a stereopsis image of fundus.
Which lens is used in indirect ophthalmoscope?
The most commonly used lenses are indirect, also known as “aspheric” and “condensing” lenses, which are classically used at a slit lamp—for example, 78D or 90D lenses—or with a head mounted binocular indirect ophthalmoscope (e.g., 20D or 28D lenses).
What is the condensing lens used for?
The aim of the condenser lens in a projector system is to align the light rays into a straight path. This allows the maximum amount of light possible to reach the projector screen. A high quality condenser lens will allow the aperture of the projector lens to be reduced in size.
What can you see in indirect ophthalmoscope?
Indirect Ophthalmoscopy 101
- Dilate properly. To conduct a good peripheral exam, the patient’s eyes must be well dilated.
- Position the patient for optimal viewing.
- Choose the right lens.
- Minimize lens distortion.
- Adjust the indirect headset.
- Depress the sclera.
- Ask for help when you need it.
Which is better 78D vs 90D?
The traditional 78D has been in use for decades and is an excellent general purpose fundus or macula lens with better stereopsis than the 90D. The Super 66 and Digital 1.0x, both 66D, provide 1.0x magnification for optic nerve measurements without applying a scaling factor.
What is a condenser lens on a microscope?
A condenser is a glass lens or lens system located within or below the stage (sub-stage) on compound microscopes. Its basic function is to gather the light coming in from the illuminator and to concentrate that light into a light cone onto the specimen.
What is a 20D lens used for?
The +20D lens is commonly used for binocular indirect ophthalmoscopy. The authors use this +20D lens for slit lamp biomicroscopy examination of the fundus. An informed consent of the patient for a clinical examination is obtained.
Why it is called indirect ophthalmoscope?
The technique of examining the fundus of the eye is called ophthalmoscopy. In direct ophthalmoscopy, a virtual and erect image of the fundus is seen. In indirect ophthalmoscopy, a real and inverted image is formed between the condensing lens and the observer.
How do you hold a 90 diopter lens?
– Keep the lens centered on the patient’s pupil. – Hold the lens far enough from the patient’s eye so that the retinal image is the same diameter as the lens. – Keep the illumination source as dim as possible to minimize reflections and loss of image contrast.
What is 20D used for optometry?
The 20D lens is the standard lens for most optometrists. It has a good combination of magnification, field of view, and lens working distance for most people.
How to choose the right lens for indirect ophthalmoscopy?
Choose the right lens You have two main options for indirect ophthalmoscopy. 20 D: The most commonly used binocular indirect ophthalmoscopy (BIO) lens, the 20-D double aspheric lens has magnification up to 3.13°— and a 60° dynamic field of view. Use the 20-D lens to evaluate macular and peripheral pathology.
What is an indirect ophthalmoscope (Ido)?
The advantage of stereopsis (depth perception) and a larger field of view makes indirect ophthalmoscope (IDO) more useful both in retina clinics and during posterior segment surgeries.
How does a binocular indirect ophthalmoscope work?
Binocular indirect ophthalmoscope. The light source mounted above and between the examiner’s eyes illuminates the condenser, which images the source at the periphery of the patient’s pupil. The illumination does not overlap the observation beam. The condenser lens is handheld; it forms an inverted aerial image of the retina.
What is a condensing lens used for?
During use, a hand held “condensing lens” is held by the examiner, a few inches above the patient’s eye. The purpose of this lens is to “gather” the light rays coming out of the patient’s eyes which are divergent due to the power of the cornea.