An optical instrument used to inspect the fundus or back of the eye is known as an indirect ophthalmoscope. Also known as a binocular indirect ophthalmoscope, the device is worn on the examiner’s head or attached to spectacles at times. A stereoscopic image that is magnified by 2x to 5x times can be produced using the instrument that can help diagnose and treat retinal tears, detachments, and holes. The procedure is performed in a dark room where the examiner positions his head to enable the light from the instrument to be directed into the patient’s eye. Pupils are dilated beforehand for the indirect ophthalmoscope to work effectively. The examiner also uses a positive-powered condensing lens, held at its focal length from the patient’s eye. Two purposes are served by the same-
1) Light from the illumination system is condensed back by the lens towards the patient’s pupil.
2) A real horizontally and laterally inverted image of the fundus is created as the light reflected from the retina passes back through the lens.
The stereoscopic view of the virtual image is made possible by a pair of low powered convex lenses that are attached to the viewing system of the instrument. For general examination, a standard +20D lens is used that offers a field of view of approximately 45° and 3x magnifications. A high powered +30D lens that offers a field of 65° approximately along with 2x magnification is used to examine kids and people with smaller pupils. If someone is new to using indirect ophthalmoscopes, these high-powered lenses are considered a great choice and are often more forgiving than the lower-powered versions.
Halogen bulbs are used as the light source in most of the indirect ophthalmoscopes. Latest models however that are durable and operate efficiently make use of LED light sources. Battery packs might also be incorporated in these models that can either be accommodated into the headband itself or worn on the examiner’s belt. This eliminates the movement restrictions that power cables versions face. Here are some of the advantages that make indirect ophthalmoscopes better than the direct ophthalmoscopes-
· Binocular vision with depth perception is permitted
· It comes with a wider field of view
· It enables examination of the anterior retina when combined with scleral indentation
· It remains unaffected by the refractive state of the patient’s eye
· It is safe to be used in the operating room without contamination
· Brighter and larger light sources can be accommodated into the same that allows the examiner to view in-depth retinal detail by penetrating moderate cataracts. If you are looking for an ophthalmoscope that boasts of convenient features, buy Welch Allyn ophthalmoscope. Quite interestingly, Smart Medical Buyer, one of the most prominent online medical retailers and suppliers in India, is giving a discount of 4% on all the Welch Allyn products including ophthalmoscopes, otoscopes, stethoscopes, BP monitors etc. from 13th May to 19th May, 2019. So if you are looking forward to buying one of the medical devices and equipment by Welch Allyn, this is the right time!