• To re-establish familiarity with the direct ophthalmoscope.
• To use the direct ophthalmoscope in a clinically appropriate manner.
• To obtain accurate ocular information using the direct ophthalmoscope.
• To prepare for a direct ophthalmoscopy assessment.

If you are using an unfamiliar ophthalmoscope then familiarise yourself with the colour coding of the lens wheel and the various apertures and filters. To undertake successful ophthalmoscopy it is essential that both you and your patient are comfortable. The patient will be more co-operative when relaxed. Also you will be more successful if you do not have to stoop uncomfortably. Patient height adjustment is however limited by the fixed chair height in this Clinic.

Instruct the patient to look at a distant target, the white spot light on the vision chart is best and advise them to keep still and concentrate on this spot and to 'pretend' they can still see it even if you obscure it with your head. The patient also needs to be given permission to blink as required. It is best if the examination is conducted in subdued lighting to improve contrast. Your left eye and left hand should be used to examine the patient's left eye. The field of view of the fundus is increased, the closer you are to the patient's eye so for low myopes and low hyperopes it is best to remove their glasses. However for myopes and hyperopes above ± 3.00DS and for astigmats above 2.50DC it is advisable to keep the glasses on in order to overcome problems associated with magnification, minification and distortion respectively. The extra reflexes produced by the spectacle lenses will at first prove distracting but can be overcome with practice.

2. Dial up a +10DS lens in the lens wheel and observe the eye from 10cm. Study the red reflex in particular as this provides an excellent way to detect any opacity of the media. Any dark patches or irregularity of the normal uniform red reflex denotes opacity of the cornea, anterior chamber or the vitreous. Look out for a Mittendorf dot, which is a small congenital lens opacity often present in normal healthy eyes.

The position of an opacity can be inferred from its parallax with respect to the pupil. Whilst examining the red-reflex, ask the patient to look up or down slightly. If, when the patient looks up the opacity appears to move in the same direction within the red-reflex then it must lie anterior to the pupil plane (i.e. the cornea or the anterior chamber). One that remains stationary must i.e. in the plane of the pupil, and one that moves in the opposite direction to that of the patient’s gaze must lie posterior to the pupil plane (i.e. the posterior lens or vitreous). You may find it easier to move yourself slightly from side to side rather than ask your patient to move their eye to achieve the same effect.

During ophthalmoscopy it is advisable to keep both eyes open and suppress the image from the other eye. It may take some practice to accomplish this.

3. Slowly move closer to the patient and at the same time gradually reduce the power of the lens in the wheel and focus on the crystalline lens, the vitreous and finally the fundus. The power of lens necessary to focus on the fundus will depend on any patient and observer uncompensated refractive error and patient or observer accommodation. Once a blood vessel on the fundus has been located then move along it and locate the point at which it branches and move your field of view in the direction in which the apex of the branch is pointing.

4. By moving along a blood vessel in this manner the optic disc will be located. You will need to consider its colour, its margins and the cup if there is one. Also note the presence of any pigment, choroidal or scleral crescents around the disc. Differentiate between a colour cup and a contour cup.

5. Retinal blood vessels should be examined in each quadrant after locating the disc. The veins are relatively large and dark red, whilst the arteries are relatively thin and pale.

6. Return to the disc and move nasally to view along the patient’s visual axis. In this position you will obscure the fixation target, cause the pupil to constrict, dazzle the patient and notice some troublesome corneal reflections. These factors make the macula a difficult area to visualise. It may be useful to use a smaller aperture beam. The normal macula is the area between the superior and inferior temporal blood vessel arcades and it's centre is the fovea.

7. Finally ask the patient to look in the eight cardinal directions to allow you to view the peripheral fundus- 'look up' to see the superior periphery and so on. In a young patient with a large pupil you will be able to get as far as the equator of the eye. You will need to adjust the lens in the wheel slightly as the periphery is closer to you than the optic disc requiring more focusing power (plus lens).

Please note that an empty box or a tick or NAD is not an acceptable comment.

• To become aware of several types of indirect ophthalmoscope.
• To establish a basic understanding of the optical principles of the different instruments.
• To be able to set up each instrument accurately and attempt to carry out an ocular examination.
• To prepare for an indirect ophthalmoscopy assessment.

Refer to the relevant instruction sheets for clinical procedures.

Numerous condensing lenses are available. VOLK, Ocular Instruments, Nikon and Haag Streit manufacture the main types of lens. They are plus powered with two convex aspheric surfaces. The +60D version has the greatest magnification and is best used for the disc and macular. The +78D version is a good general diagnostic lens, the +90D is good with small pupils, as is the SuperPupil, and the +66D produces a high definition view of the disc and the macular. The SuperField, which is approx. +90D, is a good all rounder. They are available in clear or blue-free, 'yellow retina protector glass'. This is considered to be more comfortable for the patient and minimises the risk of phototoxic retinal damage due to prolonged exposure to the focussed beam. The procedure that follows applies to any high plus condensing lens (e.g., +60D, +66D, +78D or +90D, SuperPupil, and the SuperField NC). Haag Streit produce an 81D lens which provides a view similar to that of a 78D when held one way round, and a view similar to that produced by a 90D lens when held the other way round.

•Slit lamp.

•Dilating agents (0.5% or 1.0% tropicamide-for maximum dilation used in conjunction with 2.5% phenylephrine)

•Set the illumination arm of the slit lamp to be coaxial with the viewing system (i.e. straight-ahead). This will help to ensure proper lens alignment and will facilitate initial fundus detection and observation.

•Narrow the beam down 1 to 2 mm width with a height corresponding to the vertical height of the dilated pupil. Magnification should be set to 10x.

•Ensure that the condensing lens surfaces are clean.

•Hold the lens vertically between the thumb and index finger of the left hand to examine the patient’s right eye.

•Hold the lens in the right hand to examine the patient’s left eye.

•Some lenses may be used with a lens holder mounted on the upright support of the headrest or an adapter that rests against the patient’s eyelids. Either of these accessories may make fundus observation easier for the novice.

1. Instruct the patient to fixate straight ahead, to stare wide and to blink normally.

2. Centre the beam in the patient’s right pupil and focus on the cornea.

3. Place the lens in front of the patient’s eye, directly in front of the cornea so the back surface just clears the lashes (approximately 11 mm for the +60D, 7 mm for the +78D, and 6.5 mm for the +90D and the SuperField NC, from the patient’s cornea). These condensing lenses can be used either way round. Avoid touching the patient’s eyelashes if possible. Lens positioning may be made easier by placing the other fingers on either the brow bar or the patient’s forehead. When the lens is properly positioned, a blurred red fundus reflex will appear when looking through the oculars of the slit lamp.

4. Using the joystick, focus on the fundus image by slowly moving away from the cornea, keeping the beam centred in the pupil. When scratches on the surface of the condensing lens come into view the slit lamp needs to be pulled back only a little more (about 1 cm) for the retina to be in focus.

5. Once the retinal image is focussed, widen the beam to observe a greater area of the fundus. The magnification may also be changed to a higher setting at this time.

6. Scan across the entire lens. At this stage keep the lens still.

7. In order to view the peripheral retina ask the patient to change fixation into the nine cardinal positions of gaze. It will be necessary to realign the lens and refocus the slit lamp.

8. To reduce interfering reflections, tilt the lens or increase the setting of the illumination arm to 10 degrees either nasal or temporal once the fundus has been located and focussed.

9. Depending upon the design of the slit lamp, a +60D or a +78D lens may require the patient to move away from the headrest slightly to be able to focus the retina.

10. Centre the slit lamp beam in the left eye and repeat steps 3 through 6 on the patient’s left eye.

•When viewing finer fundus details, temporally increase the lamp intensity and magnification.

•A larger field can be obtained by slightly moving the lens and the slit horizontally in the same direction.

•The condensing lens forms a real, inverted and laterally reversed image between the lens and the practitioner, approximately at the focus of the lens

•Descriptions and illustrations should be anatomically correct. Indicate where the lesion

is on the retina, not where it appears through the lens.

The Hruby lens (-55D) produces an upright virtual image that is not laterally reversed.

Patient co-operation is extremely important and can be enhanced by attention to comfort before hand. Focus the oculars to accommodate any practitioner refractive error, set the pupillary distance, remove all filters and set the magnification to the lowest setting, usually 6-10x. The illumination of the slit-lamp should be adjusted for an intermediate slit height and a 2 mm width, and then placed in the straight ahead position between the oculars (zero degrees). Check to make sure neither eyepiece is occluded. The slit-lamp rheostat should be at a medium setting. As always the slit-lamp should be adjusted for the individual practitioner. The height of the patient is adjusted with the chin rest so that the fixation device is in the centre of the patient's field in front of the contra-lateral eye. After the slit-lamp is moved into position so that the slit is imaged in the patient's pupil, the Hruby lens is introduced in front of the patient's eye as close as possible without contacting the cornea or lashes.

Direct ophthalmoscopy using a slit-lamp and negative auxiliary lenses can provide a very high level of magnification-even greater than that of the monocular hand held direct ophthalmoscope. The actual level of magnification depends on that available through the slit-lamp. Stereopsis is provided to a greater degree than all other examination techniques.

The main disadvantage of this technique is the field of view. It is smaller than all other examination methods with the exception of direct monocular ophthalmoscopy (less than two disc diameters for an emmetropic patient). More dilation is required than in other binocular techniques. The quality of the image is easily degraded by media opacities; however this problem can be reduced by increasing the slit-lamp illumination.

As the magnification is so high, small movements of the practitioner, lens, or patient have an immediately noticeable negative effect on image quality. Patient co-operation is extremely important and can be enhanced with the use of a fixation device present on most slit-lamps.

Light beams directed into the patient's eye produce reflected observation beams from the retina. These beams are focused to a viewable, aerial image following placement of a high plus-powered condensing lens at its focal distance in front of the patient's eye. The resultant image is real, magnified, reversed left to right, inverted top to bottom and located between the examiner and the condensing lens. The observer views this image through the oculars of the head-borne indirect ophthalmoscope.

1) Head band for comfortable instrument placement.

2) Light source with variable intensity illumination beams directed downward and reflected laterally by an adjustable mirrored surface in the main housing.

3) Knobs to align the low plus powered eyepieces (+2.00 to +2.50 D) with the examiners interpupillary distance.

1) Place the loose BIO onto the head and position the bottom of the front headband one index finger width above the eyebrows.

2) Tighten the crown strap until this headband position begins to stabilise.

3) Position the back head strap on or below the occipital notch and tighten until secure.

4) Loosen the knobs that control the instruments main housing (oculars and light tower).

5) Fixating straight ahead and level, vertically position the oculars to within eye lash distance from your uncorrected eyes aligned tangential to or slightly angled downward from the ocular surface; this should maximise your visual field and minimise horizontal diplopia.

6) Horizontally align each ocular by closing one eye and fixating a centrally positioned thumb at 40 to 50 cm.

7) Adjust the ocular alignment knob or slide the oculars to place an identical centrally positioned thumb in each ocular's field of view.

8) Turn on the light source and fixate straight ahead on a wall at 40 to 50 cm looking at the projected light source.

9) Use the mirror knob to vertically place the light source at the upper one-half to one-third of the field.

Head mounted BIO technique

1) Best with dilated pupils.

2) Headset in place and with the voltage set to mid-range

3) Hold a +20 D condensing lens with the thumb, index, and middle fingers of the right hand

4) The more convex surface should be toward the observer and the white-ringed edge closest to the patient

5) From a working distance of 18 to 20 inches, direct the light beam into the pupil, producing a complete red pupillary reflex

6) Pull backward on the lens, maintaining the central position of the pupil reflex, until the entire lens fills with the fundus image

7) Make fine adjustments in the lens tilt and vertex distance to produce a distortion-free full lens view.

Procedure

1) Best carried out on a dilated pupil.

2) To examine the right eye, remove any patient spectacle correction, stand to the patient's right side, and ask them to fixate straight ahead and level with the left eye; the observer should keep on any refractive correction.

3) Dim the room lighting and turn up the instrument rheostat.

4) Push the iris diaphragm lever fully to the left to maximally increase the aperture size

5) Centre the red dot on the filter dial to position the open aperture for normal viewing

6) Observers head against the forehead rest and align eye through the instrument with the patient's right eye, holding the handle with the right hand

7) When positioned several inches in front of the patient and focus through the pupil onto the fundus using the thumb and focusing lever.

8) Approach the patient and stop at 10 to 12 cm from the eye.

9) Adjust the focusing and iris diaphragm to produce a clear maximally illuminated fundus view.

10) Continue to approach the patient until the observer's knuckle lightly touches the patient's cheek, as the working distance decreases, fundus magnification will increase.

11) Angle the light slightly nasally to illuminate the optic disc.

However children often become frightened as the examiner approaches closely, as is necessary with the direct ophthalmoscope and co-operation is lost. Additionally children often fix the ophthalmoscope light and track it as it is moved by the examiner, allowing examination of the macula but not of the disc. The field of view is small and the magnification is more than is usually necessary. This will prevent the examiner from seeing the "big picture".

To avoid these difficulties the direct ophthalmoscope can be used in conjunction with a 20D condensing lens, the type used with head mounted binocular indirect ophthalmoscopes. This combination provides a moderately magnified and wider angle, view of the posterior pole. This avoids the close proximity between the patient and examiner required when using a direct ophthalmoscope alone. The technique is called modified (monocular) indirect ophthalmoscopy and has been noted for its ability to provide a good view of the retina through a small pupil.

To begin the examination a red reflex is visualised through the direct ophthalmoscope held approximately 18 cm from the patient's eye. A 20D lens is then placed 3 to 5 cm in front of the patient's eye in the path of the ophthalmoscope light beam, the examiner then needs to move slightly toward or away from the patient until a clear image of the retina is observed.

An inverted, aerial image of the retina is produced, located between the observer and the lens. The apparent magnification will gradually increase as the examiner moves closer to this image (i.e. closer to the patient), allowing more detailed examination. A magnification of 4 to 5x is obtained by moving closer to the image. As the examiner moves closer additional lenses in the ophthalmoscope are needed, to keep the image clear depending on the accommodative needs of the examiner. Experience has shown that a viewing distance of approximately 18 cm from the patient is optimal, providing suitable magnification and a wide field of view

A disadvantage of the technique, as with conventional direct ophthalmoscopy is the lack of a true stereoscopic view, however, lateral movement and rotation of the direct ophthalmoscope during the examination gives good parallax clues to depth.