Using The Direct Ophthalmoscope To Evaluate The Anterior Chamber Angle Depth

Shadow Technique Of Evaluating Angles

Width Of Shadow	Angle Grade
0 To 1 mm	4
1.5 To 2 mm	4- To 3+
2.5 To 3 mm Or 25%	3
3.5 To 4 mm Or >30%	3- To 2+
4.5 To 5 mm Or >40%	2- To 1+
> 5 mm Or >50%	1 To 0

Example Of Technique:

No Shadow, Open Grade 4 Angle

Using the ophthalmoscope as a light source which is held tangential to the iris one looks for any shadow that appears on the nasal side. If the nasal corneal and iris junction has no shadow you have a wide open angle. However, as this shadow increases in width relative to the overall cornea size, the angle becomes diagnostically narrower.

Grading The Angle Opening

Grade 4 To 3+	Grade 3
Grade 3- To 2+	Grade 2- To 1+
Grade 1 To 0
Normal Open Angle	Narrowed Angle

The shadow technique combined with the Van Herick technique will give you results that are vary close to that of gonioscopy. Vargas and Drance studied 135 eyes comparing the shadow technique, Van Herick technique, against gonioscopy and found that the shadow technique identified 26 of 29 "shallow eyes or approximately 90% the three closure patients that were missed all had plateau iris. The Van Herick technique identified 24 of the 29 shallow chambers or approximately 83%. It has been appropriately suggested that if both techniques were used, the sensitivity would probably approach one hundred percent. Narrow or shallow angles were classified as grades 1 or grades 2.

 

Using The Direct Ophthalmascope

1.) Pupils & Opacities: when you shine the ophthalmoscope into a patient's eye you should get a red-orange fundus glow back from the retina assuming there is nothing blocking its path. This is a good time to evaluate the patient's pupils by comparing their equality and shape (25% of the population have unequal pupils to some degree and is not pathological in nature). You should have either a +1 or +2 D lens in the ophthalmoscope and be viewing the pupils at a distance of 40 to 66 cms form the patient. You should be looking for any thing that interferes with the light returning from the retina such as floaters, cataracts, corneal distortions, scars, pigment on the lens, etc. You should also note what motion the opacity has either with or against, using the pupil plane as your reference point, which will help you identify the location of the disturbance. If the opacity moves in the same direction you move the ophthalmoscope the opacity is located behind the iris and most likely behind the embryonic nucleus. If the opacity moves in the opposite direction the opacity is located in front of the iris.

2.) Anterior Segment: Add plus to the ophthalmoscope and slowly work closer to the patient and the cornea, keeping the eye in clear focus, and grossly examine the cornea, lids, sclera, lashes and iris. At this point a +13 0r 13D lens will now be in your ophthalmoscope. The ophthalmoscope and your face will only be about 2 to 3 inches away from the patient or cheek to cheek so to speak. This is the correct distance you should be for the rest of the examination with the direct ophthalmoscope.

3.) Vitreous: Slowly reduce the plus power in the ophthalmoscope and work your way back through the vitreous examining it for slight changes. Such as floaters, posterior vitreous detachments and general degenerative changes of the vitreous body. Vitreous floaters are best seen with a + 6 or 7 D lens in place. With the retroillumination clearly in focus as the patient to look very quickly to their left and right the back to a fixation point. The floaters will be seen to swirl across as dark cobwebs or filaments within the retinal glow. It is better for you to ask the patient if their floaters bother them than for the patient to ask if you noticed them.

4.) Disc: Controling your accommodation allows for a close estimation of the patient's refractive error. Estimation of the refractive error is made when the optic disc just comes into focus. Examine the disc noting its shape, color, margins clarity (blurred or distinct) any scleral crescents of pigment crescents, what type nerve head, the cup to disc (C/D) ratio, the depth of the physiological cup, venous pulsation (+) or (-) or elicited. The red free filter is helpful when judging the C/D ratio and at times viewing the foveal reflex. Spontaneous venous pulsation (SVP) is absent in approximately 20% of normal individuals, therefore, you must try to elicit venous pulsation if not seen.

5.) Vessels: Artery to vein ratio (A/V) ratio, arterior light reflex (ALR), branching of vessels to all four quadrants, crossings phenomenons, etc.

Arteriolar Sclerosis and Associated Crossing Phenomenons

The eye is one organ in the body where thrombosis of a vein results from intimal arteriosclerosis. It occurs because the central retinal vein and artery and their branches are surrounded by a common adventitial sheath at their arteriovenous crossings as well as within the optic nerve. At these crossings the atheromatous process readily invades the vein, causing a similar atheromatous plaque on which a thrombosis may form. When you stop and think about it, this is how and why patients may develop a central retinal vein occlusion or a branch vein occlusion. Central retinal artery and branch occlusions ,usually, result from the above plus emboli (plaques) that have broken off the internal carotid artery, ophthalmic artery, aorta or from a heart valve. Those which successfully migrate into the arterioles of the retina may be seen at an arteriole bifurcation and are called "Hollenhorst plaques".

Two types of sclerosis affects the arterioles of the retinas (fundi) and are seen with the ophthalmoscope:
1.) Intimal atherosclerosis, a plaque - like disease of the intima.
2.) Arteriolar sclerosis affecting the arterioles. This is associated with, and believed to be a consequence of hypertension.

 

Hypertensive changes seen with the ophthalmoscope:
1.) First, narrowing of the arterioles (attenuation)
2.) Second, compression of the veins at artery vein crossings and focal spasms of the arterioles, sometimes referred to as sausaging.
3.) Third, hemorrhages which are usually of the flame shape nature within the nerve fiber layer.
4.) Forth, exudates and "macular star"
5.) Fifth, Edema of the optic disc "papilledema", cotton wool spots exudates and "macular star " Seen the chart at the end of these notes.

6.) Macula: you should record if the macula is clear or are there drusens, pigmentary migration, depigmentation (RPE drop out), elevated (edema), age related macular degeneration (ARMD) and is there a foveal light reflex (FLR) present. You should not ask the patient to look into your light when viewing the macula on a non-dilated patient. The patient will accommodate and this together with the bright light from your ophthalmoscope will make the pupil even smaller reducing your ability to view the whole macula area. You must develop the skill of moving temporally with your ophthalmoscope into the macula area not only viewing the fovea but the whole macula area plus the fovea.

7.) Fundus: Observe as much of the posterior pole as possible and check the integrity of the back ground. To accomplish this have the patient look in different directions, since, the total area seen is only 6.5 to 10 degrees at any one time. This will depend to some extent on the patient's pupil size.

8.) Filters: The red free filter in the ophthalmoscope is a very diagnostic tool. For one it is used to differentiate between retina nevi or choroidal nevi. The retinal blood supply and its retinal pigment epithelium (RPE) act like a red filter. Therefore, a nevus that is behind the retina and located in the choroid will not be seen when viewed with the red free filter since red and green cancel each other out. On the other hand a nevus located on or in the retina will still be seen with the red free filter in place. The red free filter also makes small macro-aneurysms and small hemorrhages standout more clearly. The red free filter can also be helpful in estimating the C/D ratio. Nerve fibers are lost in glaucoma and optic atrophy and using the red free filter can help detect these subtle changes. If the scope has a cobalt blue filter this too works to detect nerve fiber drop out. Some feel the aforementioned condition is best view with the cobalt blue since the blue light wave length is focused more directly in the nerve fiber layer. Other than the nerve fiber layer the cobalt blue filter has little use when examining the retina.

The optic nerve head is usually not round but oval in nature. The horizontal component is approximately 1.5mms (1500 microns) or 5.5 degrees across and the vertical component is 7.5 degrees. The fovea is located approximately 2DD temporal and 1.5 degrees below the horizontal. The small spot of light (apertural) in the direct ophthalmoscope is intended to be approximately one disc-diameter in size. Place the spot on the disc and observe how much of the disc is filled up. If the disc fully fills the spot of light and matches its size this would indicate a normal disc size. Optic nerve heads will vary in size. A recent study, Heijl A., Molder H. Act Ophthalmologica 71 (1993) 122-129, there is a tendency to label large discs with large cup as being glaucomatous even if they are not and small discs as normal even when glaucoma is present.

Magnification Of The Direct Ophthalmoscope

The direct ophthalmoscope gives a magnification of approximately 15 x and a field of view of 6.5 to 10 degrees, therefore, if you want to see more than just the very posterior pole you will have to have the patient look in 6 to 8 different directions. This 15 x magnification makes the 1.5 mm disc appear much larger than it really is. The formula M= 60D/4 holds well for up to + or - 10D's of refractive error. You can really appreciate this small field of view when you compare what you seen with the direct and the indirect view of the penlight technique.

Monocular Indirect Ophthalmoscope

The monocular indirect ophthalmoscope (MIO) gives a magnification of 5 x and a field of view of approximately 30 degrees, but it is important that you have the patient look in 6 to 8 different directions to see as much of the fundus as possible. The optical system of the MIO has an erecting lens which allows you to see things as they actually appear anatomically. It also gives you a greater working distance from the patient of 5 to 6 inches. The mio has a yellow filter that allows one to see deeper details of the retina at about the level of the choroid which is nice. The cost of the MIO is about equal to that of a good binocular indirect ophthalmoscope and you of course do not get a stereoscopic view of the retina.

Things not to do:

There are certain things that you should be careful of or not do at all when performing ophthalmoscopy on a patient. Do not put your hands on the patient's shoulder use the back of the chair to steady yourself. Do not put your hands on the top of the patient's head. Number "ONE" women and many men do not like for you to mess up their hair and "SECOND" there are men who are wearing hair pieces that go flying off their head very easily "be careful out there." Last, you cannot do much about your patient's breath on personal hygiene, but you can yours so make sure to pay some attention to the both.

Penlight Ophthalmoscopy

This is a very old technique that originally utilized a pen light and a high plus lens. The pen light can still be used, however, your direct ophthalmoscope gives a brighter light that is more uniform. The patient must be dilated to get as much binocularity as possible and large field of view. The ophthalmoscope is held just below your eyes and its light directed into the patient's eye. The patient's eye is viewed from over the top of the ophthalmoscope while a 20D lens is placed approximately 3-4 cm from the patient's eye. The condensing lens is held just like a 90 or 78D lens between the thumb and forefinger with the other fingers resting on the patient's brow or forehead. The light leaving the condensing lens must come to focus within the pupil allowing the fullest field of view of the retina, approximately 30 degress. The image is inverted and perverted and located between the ophthalmoscope and the condensing lens. The degree of stereopsis depends on how fully the pupil is dilated and ones ability to converge and accommodate on the image. There are a number of views when stereopsis will be lost and the image is seen in a monocular fashion. It still gives a larger field of view than a MIO though less magnification. One should not be mislead in believing this will take the place of a binocular indirect ophthalmoscope (BIO) for you just do not have the stereopsis. This is an excellent method to examine small infants. They become frightened by the ominous looking presence of the BIO on the doctor's head not to mention the bright light. Should the bulb burn out in a BIO one has an alternative means to get a good view of the peripheral fundi.

Grades Of Vascular Retinopathies

A.) Hypertension

B.) Arteriosclerosis

Degree	A/V Ratio	Hemorrhages	Exudates	Papilledema	Light Reflex	A/V Crossings
Normal	2/3-3/4	None	None	None	Fine Yellow Line 1/3-1/4	None
Grade 1	A/V=1/2	None	None	None	Slight Increase	Mild Compression Of Venules
Grade 2	A/V=1/3	None	None	None	More Marked	Compression or Elevation Of Venules
Grade 3	A/V=1/4	Present	Macular Star	None	Copper Wire	Right Angle Deviations, Nicking Or Tapering
Grade 4	Fine Cords	Present	Cotten Wool & Macular Star	Present	Silver Wire	All The Above Plus Marked Distal Congestion

Hypertension And Arteriosclerosis May Occur Together In Varying Degress. This Table Is Only Intended To Serve As A Guide To Better Help Organize The Ocular Signs.

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