Slit-lamp examination - Ophthalmic Nursing

An introduction to the slit lamp and basic examination techniques is presented here.

Using the slit lamp

It is important to practise and familiarise yourself with the controls of the slit lamp. It is like driving a car and getting used to the clutch and the gear stick, etc. and gradually gaining in conﬁdence. Find a willing volunteer to sit on the other side and go through the practical skills.

The principle

A narrow ‘slit’ beam of very bright light is produced by a lamp. This beam is focused onto the eye, which is then viewed under magniﬁcation with a microscope

Basic key points in slit-lamp examination

r

The patient’s and your own comfort at the slit lamp are of utmost impor- tance.

r

Good explanation and reassurance of this procedure will ensure the patient’s co-operation.

r

Be systematic and methodical in your slit-lamp examination to ensure that nothing gets omitted.

r

Ensure that your eye pieces are properly adjusted prior to commencing, e.g.

your refractive errors (if any) are accounted for and that you have adjusted the pupillary apertures accordingly.

r

All ﬁndings should be accurately and legibly documented.

Uses of slit lamp

r

Observation of ocular adnexa and structures, including cornea, anterior chamber, iris, lens and anterior vitreous face;

r

Monitoring signs and symptoms of anterior segment disease or injury;

r

Examination of posterior segment of the eye by the use of auxiliary lenses;

r

Further ‘special’ investigations:

r

Goldmann tonometry

r

Van Herrick’s estimation of anterior chamber depth

r

Gonioscopic examination of the angle.

Components of the slit lamp

r

The microscope which houses the viewing system, composing the oculars and the magniﬁcation changers;

r

The illumination arm, which houses the illumination system;

r

The remainder of the instrument, e.g. chin rest, ﬁxation light, etc.

The microscope and adjustment of ocular eyepieces

The slit lamp has binocular microscopes, which means that it gives the ex- aminer a three-dimensional view of the eye and surrounding structures. The advantage of a three-dimensional view is that ocular abnormalities can be detected with greater precision.

The viewing system of the microscope can be adjusted to account for any refractive error. If you normally wear glasses, you need to make a decision as to whether to keep them on or take them off for examining the patients. If you wish to remove your glasses to examine the patient, the viewing system should be set up to accommodate your refractive correction. If you are unsure what your refractive correction is, a focusing rod (supplied with the slit lamp) can be used to measure your refractive error. Slide off the footplate and insert the focusing rod with the ﬂat side facing you. Turn on the slit lamp and, using a slit beam of light (about 1–2 mm in width), focus the light onto the rod.

Close one eye and, with the other eye, look through the slit lamp and start turning the wheel of the ocular eyepiece from the plus side of the scale and stopping immediately as soon as the image of the light through the eyepiece is clear and in focus. Where possible (if you know your own refraction readings), check whether the scale readings in dioptres actually correspond to your own spectacle correction.

You will also need to adjust the interpupillary distance for your own eyes as some people’s eyes are more widely spaced apart or closer set than others. In order to adjust the eyepieces to suit your interpupillary distance, ﬁrst take a look down the binocular eyepieces of the slit lamp. You must not be aware of seeing any black shading in your ﬁeld of vision. If black shading is noted, you will need to adjust the interpupillary aperture, either by squeezing the eyepieces together or by pulling them further apart. When the pupillary apertures are correctly set, you should have an unobstructed view with both eyes when looking down the slit lamp.

Attached to the binoculars of the microscope are settings for magniﬁcation.

Depending on your slit lamp model, the magnification changer can be altered either by flipping a lever just at the bottom of the ocular eye pieces or by turning a knob which is attached a little distance from the eyepieces. If your magnification changer is a lever switch, you will have two different settings on 10×and 16×. If your magnification changer is a knob, you will have five different magnification settings – 6×, 10×. 16×, 25×and 40×. Magnifications of 10×and 16×are adequate for most examination purposes.

The illumination arm

The illumination arm houses the illumination system. The illumination arm is capable of being moved from 0^◦ to 90^◦ from either side of the microscope.

The illumination arm houses the following components:

1 Two slit controls which have the capability to vary the height and width of the slit beam. Additionally, the orientation of the beam can be altered from a vertical to a horizontal plane. The slit control is also used for interposing of the blue ﬁlter.

2 Various ﬁlters are available which control the heat and light intensity of the beam. In addition, colour ﬁlters are available and these are used are in conjunction with different eye drops.

3 The position of the illumination system to the observation system can be measured by a graded index which is located at the bottom of the illumination column. Knowing the angle of the illumination to the illumination column is important for examining/grading certain structures of the eye.

Slit lamp position controls

The movement of the slit lamp is by using the joy stick. The joy stick is situated on the base of the slit lamp and, by moving the joy stick left to right and back to front, movement of the slit lamp is achieved. In addition, twirling the joy stick clockwise will elevate the slit lamp, and turning the joy stick anti-clockwise will lower the slit lamp.

Further adjustment to the slit lamp can be achieved by a lever located at the base of the slit lamp table. By releasing the lever, the height of the whole table (including the slit lamp) can be adjusted to accommodate the height of individual patient.

The patient’s comfort at the slit lamp can be further achieved by moving the chin rest up and down by means of a lever adjustment knob located on the side frame of the slit lamp. When the patient is in the correct position, the patient’s outer canthus is aligned with a black mark or notch on the headrest bar and the patient’s forehead against the forehead rest.

Adjust for any refractive error by using a focusing rod – if you wear glasses and know your refractive error, the eye pieces can be adjusted accordingly.

Otherwise remove the foot plate and slide in the focusing rod with the ﬂat side facing you.

Turn on the slit lamp and, using a slit beam of light (about 1–2mm in width), focus the light onto the rod. Close one eye and, with the other eye look through the slit lamp and start turning the wheel of the ocular eyepiece from the plus side of the scale and stopping immediately as soon as the image of the light through the eyepiece is clear and in focus

Familiarise yourself with the controls, switch the machine on. Start off with using the lowest voltage setting on the slit lamp to minimise patient’s discom- fort at having a very bright light in his eyes.

The joystick moves the whole slit lamp – the illumination system as well as the binocular – up and down and left and right. These various movements allow you to examine the eye at various positions and depth. It also allows both eyes to be examined with ease. When the slit lamp is not in use, secure the slit lamp to the table by turning the screw, which is situated on the right-hand side of the base of the slit lamp. If the slit lamp is not securely fastened, the microscope may roll forward, causing the whole slit lamp to topple forward, jarring not only the delicate optics and illumination system but also potentially crushing the patient.

The illumination arm

At the top of the arm, the first circle on the left-hand side represents unfiltered bright white light. You should never use this first light as, in theory, you could burn the retina. The second circle with slashes in the centre represents the heat filter, while the third circle is the grey filter. The last circle is for accommodating an additional filter.

NB: You use the green light to make red objects black, thus increasing their deﬁnition.

The blue filter is used for examination of corneal integrity and for applana- tion tonometry. It is necessary to instil topical fluorescein to observe if the cornea is compromised and a combination of topical local anaesthetic and fluorescein for the measurement of intra-ocular pressure.

PROCEDURE GUIDELINE

Step by step to a good basic slit-lamp examination

Nursing Action Pre-procedure

Good explanation to the patient is vital in order to ensure co-operation.

1 Explain to the patient that, although the machine may look formidable, it is only a gloriﬁed microscope used to magnify the different structures of the eye.

2 Inform the patient that he needs to ensure that his forehead must rest against the bar, that his chin must be in the chin rest, and that his mouth must be closed.

3 Warn the patient that the light from the slit lamp can be bright.

4 Tell the patient to keep both eyes open.

Nursing Action: Positioning the patient

The position of the slit lamp is equally important to ensure co-operation.

Be patient with the elderly and the very young. If the patient is in a wheel chair, where possible transfer them to your examination chair. If it is not possible, manoeuvre the slit lamp as close as you can to the patient by removing the arm and footrest of the wheelchair. For shorter patients or children, it is possible to examine them standing right in front of the slit lamp. Women with large breasts can have considerable difﬁculty in leaning forward, and you may experience difﬁculty in pushing your slit lamp all the way forward. In this scenario, place the examining chair away from the slit lamp and get the patient to lean forward and into the chin and headrest. Patients with head tremors should have their head supported from behind. Above all, be patient.

1 Align the black marker to the patient’s outer cantus.

2 Correct positioning can be achieved by moving the whole slit lamp (including the table) up or down using the lever situated underneath the table and manipulating the knob of the chin rest.

3 Make yourself comfortable.

Tips for using the slit lamp

r

Fixation: ask the patient to look at your right ear when you examine his right eye and vice versa: some machines have a ﬁxation light; this is useful when you are removing foreign bodies.

r

The wheel moves the chin rest up and down.

r

The latch tilts the slit lamp, which is useful for posterior examination work or if you want to see the depth of a foreign body penetration.

r

Set your slit lamp on the lower magniﬁcation and turn on the control box on to the lowest voltage.

r

Usually one hand is used to operate the joystick and the other hand to operate the illumination arm. If examining the patient’s left eye, have the illumination unit on the left-hand side and vice versa.

... ...

.

... ...

.

r

In order to focus the light on to the slit lamp, you can look at the patient’s eyes by looking from the side of the slit-lamp machine and grossly aligning the eye. Once when the eye is grossly aligned, look through the oculars and ﬁne tune the focus by using the joy stick and by movement of the illumination arm. The second method of alignment is to look through the oculars from the beginning and, by using the joystick, to move the slit lamp and illumination arm until the eye is in focus. For the beginners, this may require some practice before you get the hang of it. Don’t despair if you don’t get it the ﬁrst few times. It gets easier with practice.

r

Be methodical in your examination. In this way, you are less likely to miss something.

... ...

Dalam dokumen Ophthalmic Nursing (Halaman 77-82)