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الكلية كلية الطب
القسم الجراحة
المرحلة 5
أستاذ المادة اسعد جعفر عبد السادة الطائي
4/20/2011 8:19:05 PM
- Ophthalmoscopy:
It is a method of examination of the inner surface of the eye (fundus = retina + optic disc).
Direct ophthalmoscopy:
Principle: light from the instrument is directed to the patient s pupil and reflected from his fundus back through the viewing aperture (an opening in the instrument through which the examiner looks) to the observer s eye. There are lenses in a wheel (lens-selection ring) that can be used to clarify the picture if either the patient or examiner is ametropic (have refractive error).
Rules of examination by the direct ophthalmoscope:
1- Tell the patient to look at a given far object (to relax accommodation).
2- If you are to examine the right eye hold the instrument with your right hand, use your right eye and stand by the patient s right side and the reverse is true for the left eye.
3- At a distance of 20cm you can see the (red reflex) which is the enlighted pupil, a normal brisk red reflex means clear media and no gross retinal detachment.
4- Holding the red reflex in view approach the patient as much as you can to see the details of the fundus. You should be able to see the optic disc (look for four points in it: shape, margins, colour and cup). You should see the macula (featureless area between the two major temporal vascular arcades), see the vessels: ratio of artery to vein wall width is normally 2/3, crossings, haemorrhages, exudates (soft and hard), microaneurysms and oedema. Lastly see the peripheral fundus: the side that we want to examine we tell the patient to look into its direction.
Indirect ophthalmoscopy:
The examiner uses a hand-held lens (condensing lens) to focus a real fundus picture in front of him. The source of light is head-mounted and is very strong. Advantages are wider field, stereoscopy, it can bypass some medial opacities can be used in surgery (detachment surgery) and it is relatively not affected by errors of refraction (see table).
- Slit-lamp biomicroscope:
Consists of:
1) Illumination column: giving you several options of focal light the most useful of which is the slit shape (due to the optical section effect) and by the use of filters (polarized, red-free and cobalt light).
2) Binocular microscope: which through the use of prisms can vary the distance between the two eyepieces to fit the distance between the 2 eyes of the observer, it has several magnification options and offers stereoscopy.
The illumination column and microscope rotate around a common axis (co-axial) in the centre of which lies the eye of the patient on which both systems focus. By the slit-lamp we can examine the anterior segment and the anterior third of the posterior segment of the eye. To examine the rest of the eye we should use one of the following accessories:
1- Goldmann s 3 mirror contact lens.
2- Hruby (plano-concave) lens.
3- Volk s high power (+78 to +90) biconvex lens.
In addition to its use in detailed stereoscopic magnified examination of the eye, it can be used to do some minor surgical procedures as removal of stitches or foreign body.
- Retinoscopy:
This is an objective method of examination of refractive state by utilizing the principle of movement of light shadow in the pupil relative to the movement of light source. Types:
- Mirror retinoscope: a small round mirror with an opening in the centre to reflect light from a light source over the patient s head, the observer watches the red reflex of the patient through the opening in the mirror which he moves to see movement of the light in the pupil, if the movement is (with) he is hypermetrope, if (against) he is myrope, then (neutralize) the movement with a suitable lens in front of the patient s eye.
- Streak retinoscope: with self-illuminated, battery-operated mechanism, employing a more elaborate streak of light working on the same principle.
- Identification of lenses:
Use a cross drawn on a paper and look at it through the lens then move the lens in a vertical direction. If the image of the cross through the lens moves (with) the lens movement it is concave, if (against) it is convex, then move the lens in a circular movement around its centre, if the limbs of the cross deform changing the angle between them then it is a cylindrical lens.
Pin-hole:
It is an occluder with a small opening in it. If visual acuity of a patient improves on looking through it, then the cause of his reduced visual acuity is error of refraction.
Prism:
Image of the cross do not move on movement of the prism but it is deflected from its expected location towards the apex of the prism. Prisms are used in diagnosis and treatment of eye deviations and in ophthalmic instruments.
Keratoscopy:
The study of corneal surface by projection of a regular image (e.g concentric white and dark circles) on it utilizing its characteristic reflection as a convex mirror (e.g Placido disk).
Maddox wing:
Principle: the eyes are dissociated by barriers, one eye fixes an arrow and the other fixes a scale.
Purpose: measurement of eye-balance for near. Used mainly for measurement of heterophoria (latent squint).
Maddox rod:
Principle: a set of translucent tubes to convert a point-light into a red line thus dissociating the eyes.
Purpose: measurement of eye-balance for far, used with the trial frame and prism which is a measure of heterophoria.
Synoptophore (major amblyoscope):
A chin-rest, a bent tube is sited in front of each eye with an arrangement at the end for casette-fitting to vary targets presented to each eye and vary the direction of each tube in 3 dimensions. This instrument is used for diagnosis and treatment of a wide variety of eye balance abnormalities.
Yag laser instrument:
Slit lamp technique is used to deliver high energy pulsed UV laser to make an opening in an intraocular membrane without opening the eye.
Lid retractor:
A metal instrument that has got 2 uses:
1- Examination of children.
2- Double eversion of the upper lid.
Gonioscopy:
An instrument to visualize the angle of the anterior chamber either directly or indirectly (mirror gonioscope).
Tonometer:
An instrument to measure the intraocular pressure:
- Schi?tz tonometer: cheap, portable, do not need a slit-lamp and can be used on unhealthy cornea but it is less accurate (an indentation tonometer).
- Goldmann s applanation tonometer:
Highly accurate but needs slit lamp and healthy cornea.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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