Dark Room Procedures for undergraduates(MB,BS) in the field of Ophthalmology are explained in simple terms in this presentation. Series of lectures taken at Central Park Medical College Lahore Pakistan.
Undergraduate lecture 4-Dark room tests in ophthalmology
Dark Room Tests Dr. Zia-Ul-Mazhry FCPS(Pak), FRCS(Edin), FRCS(Glasgow), CIC Ophth- (UK) Assistant Professor Central Park Medical college Lahore Consultant Eye Surgeon & Head of DepartmentWAPDA Teaching Hospital Complex Lahore.
Dark room Tests• Oblique Illumination• Distant Direct Ophthalmoscopy• Direct Ophthalmoscopy• Retinoscopy• Indirect Ophthalmoscopy – Indirect Ophthalmoscope – Slit Lamp Biomicroscopy
Oblique Illumination• Objective – Examination of External and anterior Segment structures• Instruments – Illumination Beam – Magnification Aid/Microscope• Method – Illumination beam at 45 degrees
Slit Lamp• The slit-lamp is a low- power microscope combined with a high- intensity light source that can be focused to shine in a thin beam.
SLE• Observation by optical section• Direct diffuse illumination• Indirect illumination• Retro-illumination• Scattering sclero- corneal illumination• Fundus observation and gonioscopy with the slit lamp
SLE• The slit lamp exam uses an instrument that provides a magnified, three-dimensional (3-D) view of the different parts of the eye. During the exam, your doctor can look at the front parts of the eye, including the clear, outer covering (cornea), the lens, the colored part (iris), and the front section of the gel-like fluid (vitreous gel) that fills the large space in the middle of the eye.• Special lenses can be placed between the slit lamp and the cornea (or directly on the cornea) to view deeper structures of the eye, such as the optic nerve, retina, and the area where fluid drains out of the eye (drainage angle ). A camera may be attached to the slit lamp to
Distant Direct Ophthalmoscopy• Objective – To Examine and classify media opacities against fundal glow• Instrumentation – Direct Ophthalmoscope• Methods – Throw the light with DO at half meter distance – Parallax Method of deviation
Distant Direct Ophthalmoscopy• Parallax Method of deviation – Ask the patient to move his/her eye – Opacities Moving • With – Anterior to nodal point • No movement – At or very near to nodal point • Against Movement – Behind the nodal point
Distant Direct Ophthalmoscopy• Viewing ocular media – Observe red reflex – Look for media opacities • Cataracts • Corneal scars • Large floaters
Direct Ophthalmoscopy• Objective – To examine the retina/fundus• Instrumentations – Direct ophthalmoacope• Methods
Fundoscopy• Fundoscopy is the assessment of the fundus using an ophthalmoscope
Examination Technique• dim the lights.• ask the patient to fixate on a distant target.• approach the patient from the side.• examine the optic nerve and surrounding retina.
Direct Ophthalmoscopy • Advantages – Portable – Easy to use – Upright image – Magnification 15x – Can use w/o dilation • Disadvantages – Small field of view – Lack of stereopsis – Media opacities can degrade image
Indirect Ophthalmoscopy• Monocular or binocular• Advantages: – Wide field of view – Binocular instruments provide stereopsis• Disadvantages: – Requires more skill – Decreased magnification (3x) – Requires dilation – Inverted image
Macula• Lies about 2DD (disc diameters) temporal to the optic disc• Should be avascular• May appear darker red than surrounding retina• Should see bright foveal reflex on younger pts
The Indirect Ophthalmoscope George T. Timberlake, Ph.D. Department of Ophthalmology University of Kansas Medical Center Gullstrand Indirect Ophthalmoscope ca. 1910
Allvar Gullstrand 1862 - 1930 Professor of Physical & Physiological Optics, University of Uppsala First “reflex free” ophthamoscope Nobel Prize 1911 for work on optics of eyeSwedish Ophthalmologist GTT 04
Gullstrand Principle for Reflex-free OphthalmoscopyLight entrance and exit separated in pupil plane Light entering eye Light leaving eye Pupil GTT 04
Retinoscopy• Objective – To determine refractve status of the eye• Instrumentation – Retinoscope – Trial Lens set – Trial frame
Retinoscopy• Methods – Ask the patient to fixate on a distant target – Half to 1 meter distance – Project the streak on pupil – Move the streak and observe the movement of red reflex
Retinoscopy• Moves with – Emetropia – Hyperopia – Myopia of less than 1 diopter• No Movement – Myopia of exactly 1 diaopter• Moves against – Myopia of more than 1 diopter
Retinoscopy• Insert +1 D Lens in front of the eye while working at 1 meter – No movement • Emetropia – With movement • Hyperopia – Against movement • Myopia of < 1 D