Indirect Ophthalmoscopy and Slit Lamp Biomicroscopy

By Dr.Lakshmi.K.SModerator: Dr.Sudhir Hegde

Index Indirect Ophthalmoscopy• History• Principle, procedure and recording of findings in IDO• Small pupil IDO• Scleral indentation technique• Advantages and disadvantages Slit Lamp Biomicroscopy• Types of lenses used, their advantages and disadvantages Ophthalmologists health issues Fundus Drawing

History of Indirect Ophthalmoscope

• In 1700s- doddel, Richter, Beer noted spontaneous luminosity of human eye

• 1823- Purkinje, under certain conditions of illumination human eyes could be made luminous

• 1846, 1847- Cumming and Brucke finally realized that the observer had to stand in the path of the emerging rays to see the luminous eye

• 1850- helmoltz direct ophthalmoscope• 1852- Reute 1st mono ocular indirect ophthalmoscope

• 1958- schepens, binocular indirect ophthalmoscope provides an excellent resolution of fundus

Principle • Indirect Ophthalmoscopy (IDO) involves making the eye highly

myopic by placing a high power convex lens (+13D to +30D) in front of the eye so that a real, inverted and laterally reversed image is formed in front of lens

• The technique is called Indirect because the fundus is seen through a condensing lens.

• The image is formed close to the principle focus of the lens, between the lens and the observer

Illumination System• Presence of the corneal reflection and the

usual backscattered light of the healthy cornea and lens make the evaluation of fundus changes difficult.

• Gullstrand evaluated the principles• Observation beam and the illumination

beam be separated at the corneal and lens plane, to avoid corneal and lens reflection and scatter for which a dilated pupil is needed

• With patient and observer pupils conjugate, loss of light is minimized, and field of view is maximized.

The power of the condensing lens determines:• Working distance • Magnification• Field of view As the power of condensing lens decreases, field of view decreases but

working distance and magnification increases Roughly, magnification is the eye power divided by the power of condenser

lens used

Lens Power (D)

Static Field of View* Magnification Working Distance from Cornea

+14 22 4.17 72 mm

+20 30 3.25 47 mm

+30 40 1.97 26mm

Stereopsis • Normal interpupillary distance is about 60mm• Reduced to 15mm by the use of prisms in IDO• reduces the stereopsis appreciated by an observer by about

one fourth• axial magnification (which equals one fourth of the square of

lateral magnification) augments the stereoscopic appearance

Parts of an indirect ophthalmoscope

Examination technique

Preparation:• Dilatation of eyes. •dark rooms preferred whenever possible.• preferable to have a patient chair that fully reclines, enabling the practitioner to move around the patient and hence gaining a full 360° traverse of the fundus. • If a reclining chair is not available, the practitioner will have to make more use of the patient fixating peripheral targets, and this will often mean that a smooth traverse of the peripheral fundus is not possible

• Proprioception helps patient to look in cardinal gazes

• Patient should be urged to keep the other eye open

Helpful hints

Alignment of the head-band ophthalmoscope

• Place the ophthalmoscope on the head and adjust the straps for maximum comfort

• Face a wall approximately 40 cms away, and adjust the illumination mirror such that the illumination field is vertically centralized to the observation ports

• Move the viewing ports horizontally by adjusting the interpupillary distance to align with the illumination field

• Adjust the illumination system to give the required field.• Set the illumination at a medium intensity to start with.

Use the yellow lens to reduce the amount of blue light on the retina

Procedure Proper• The practitioner should first illuminate the patient’s pupil area by pointing the head and hence the illumination towards the patient’s eye.• Interpose the condenser lens close to the eye about 2 cm, and centre the lens on to the pupil. The lens should be held with the more convex side towards the practitioner.• Pull back the lens away from the patient’s eye, at the same time taking care to keep the illumination centered on the pupil. Whilst withdrawing the lens, the practitioner will find a distance that provides an optimum field of view. This should be approximately at the focus of the lens, i.e. 5cms from the pupil using a +20D lens• Having obtained an image filling the BIO lens, the fundus may then be examined by moving around the patient if reclining, or by redirecting the patient’s fixation if seated

Holding the lens

Pivot

Imaginary Convex Eye Technique

• One of the main difficulties encountered by those new to indirect ophthalmoscopy is that the image of the fundus is both inverted and reversed

• With direct ophthalmoscopy in mind, the examiner would have been tempted to move down or ask the patient to look up

• The opposite is required with indirect ophthalmoscopy and this does take some getting used to.

• Whilst observing the aerial image of the fundus, the practitioner should imagine that the fundus image is convex and not its true concave form

In figure a naevus has been observed by the examiner(position P) on the inferior fundus (seen superiorly). The optometrist should move up (position S) or ask the patient to look down to view the lesion

Recording the findings

• By orienting the paper so that its 12 o'clock meridian is directed inferiorly toward the patient's feet, the image fields can be visually translated directly onto the paper without having to mentally invert them.

Video

Small pupil indirect ophthalmoscopes

• Many IDO’s incorporate a small pupil feature which facilitates the examination of eyes when the pupils dilate poorly or eyes harbor focal medial opacities

• A small lever located under the eye pieces is moves in position to engage this feature

• This lever physically places the illumination and visualization pathways closer together by moving a triangular prism

Scleral depression technique

• To take full advantage of head-band binocular indirect ophthalmoscopy, the practitioner should learn to perform scleral indentation

• Scleral indentation will neither cause nor worsen retinal tears or detachments

• The examiner should choose a thimble or other type of depressor tool that feels comfortable to hold

• Sitting to one side of the patient, the examiner should gently place the probe on the outside of the lid. A starting position would be a little higher than the inner canthus, just missing the caruncle, and at 180° to the observation angle

• The practitioner should very gently and tangentially move the probe into the fold of the lid (approx 8mm from the limbus)

• Look for the indentation in the lower field of the BIO lens, as it will be inverted. Keep the depressor moving slightly to aid finding the indented retina

• The 3o/c and 9o/c positions can be indented by placing the depressor slightly above on the upper lid (2o/c and 10o/c), and sliding the probe round to move it into the inner or outer canthal positions

• If this is difficult, indentation can be done applying the probe to the sclera without the intervening lid, but topical anesthesia should be used to make your patient comfortable

• A – Patient looks down, depressor on margin of sup tarsal plate• B – Depressor advanced into the orbit as patient looks up but no

depression applied as yet• C – Scleral depression applied gently to area of interest

Scleral Depression technique

Critical in obtaining a binocular (stereoscopic) view

Comparison with direct ophthalmoscopy

Advantages of IDO• Larger field of view• Lesser distortion of retinal image• Easier to examine if patients eye movements are present

and with high spherical or astigmatic refractive errors• Stereopsis• Useful in hazy media due to its bright light and optical

property• Can be used intraoperatively• Vitreous can be examined easily and various vitreous

abnormalities diagnosed through this

Disadvantages of IDO

• Difficult to learn• Less magnification, therefore details of a small

lesion not visualized properly• Impossible with very small pupils• More uncomfortable to the patient

Inexpensive method of indirect ophthalmoscopy

• K R Bishai- BJO 1989

Video indirect ophthalmoscopy

• Mahesh P shanmugam- IJO 2011

Simple model for indirect ophthalmoscopy

Tumaini University/ KCMC, Moshi, Tanzania- BJO 2006Using• Styrofoam pad• Glass marble• Small print paper• Black paper

Slit Lamp Biomicroscopy• Retinal SLM BIO affords high magnification and illumination

necessary to evaluate retinal lesions in detail• Because the cornea has such a high refractive power, the slit-lamp

microscope can view only the first one third of the eye. • Special lenses, in conjunction with the slit-lamp microscope, can

be used to view the posterior vitreous and the posterior pole retina.

• The two ways to overcome the high corneal refractive power are: (1) nullify the corneal power(2) utilize the power of the cornea as a component of an

astronomical telescope, in a manner similar to that exploited by the indirect ophthalmoscope.

It consists of• A binocular slit lamp biomicroscope• Any one of the following lenses1. Hruby lens2. Contact lens biomicroscopy- modified koeppe’s

lens, wide field panfundoscopic indirect contact lens, goldmann’s 3 mirror contact lens

3. Findus non contact lens- range from +60 to +132 D, most commonly 90D and 78D

Hruby lens biomicroscopy• A plano concave non –contact lens • High minus power [-58.6 D]- nullifies

corneal power• Virtual erect image• To visualize optic cupping , peri papillary changes Nerve fibre layer-thickness [red free

filter] Macular lesion level [slit beam

sideways movement-watzke Allen test]

Vitreous opacities, strands.• Disadvantage- its used exclusively for

posterior pole as distortion seriously degrades the image if the fundus is viewed along any axis other than the approximate optical axis of the patient's eye

Contact lens biomicroscopy

• Goldman’s Contact lens• Goldman’s three mirror contact lens• Mainster contact lens• Panfundoscopic contact lens

Contact lens biomicroscopy• The Goldmann contact lens -

nullify the dioptric power produced by the corneal curvature and to bring the retina into the focal range of the slit-lamp microscope

• plano-concave contact lenses • forms virtual, erect, and

diminished images of the illuminated retina near the pupillary plane, within the focal range of the slit-lamp microscope.

Contact lens biomicroscopy- Goldman’s 3 mirror lens

• Concavo plano contact lens - virtual , erect image

• Combines stereopsis, high illumination, high magnification [10 x] , 20 degree field.

• Flat central portion – posterior vitreous and pole

• Angled mirror-3 73 deg - area around posterior pole 67 deg - equatorial fundus 59 deg - peripheral retina and

iridocorneal angle

• Eliminates total internal reflection by replacement with cornea – goldmann contact lens interface.

Technique for examination• Dilate pupils• Topical anaesthesia• Insert coupling fluid into the cup of contact lens• Ask the patient to look up, insert the inferior rim of contact

lens into the lower fornix and press it against the cornea• Examine the vitreous cavity using central lens and then

examine the posterior pole and perephery using mirrors• To visualize the entire fundus, rotate the lens for 360 deg using

the 59, 67 and 73 deg tilted mirrors• To obtain a more peripheral view of retina, tilt the lens to the

opposite side and ask the patient to look in the same side

Advantage• Very high resolutionDisadvantage• Limited field of view• Cumbersome to use

Panfundoscopic lens• Consists of a meniscus lens coupled

with a spherical lens (high powered condensing)

• A real inverted image obtained in the spherical glass element which is within the focal range of slit lamp microscope

Advantage Because the lens is close to the eye

and of such high power, field of view is very wide, without rotation of lens like the mirrored lenses

Can be used in poorly dilating pupilsDisadvantage the image is small and periphery not

clear and hence Used more often for laser photocoagulation than diagnostic purposes

Mainster lens• Has a biconvex, aspherical anterior

lens element and a concave lens to fit to the corneal curvature

• Provides a somewhat reduced field of view compared to panfundoscopic lens, but produces higher magnification (.92X)

• Good resolution for cases of macular thickening

• Versatile for both diagnostic and therapeutic purposes

• Image plane is anterior to lens surface- therefore difficult to view fundi of patients with hyperopia or exophthalmos

• Mainster widefield (118 deg) and mainster ultrafield PRP lens (165 deg) gives a greater field of view and mainster high mag (1.25X) gives a higher magnification

ComparisonParameter Goldmann Panfundoscope Mainster

Anterior surface Flat Convex Spherical Convex Aspherical

Power -67 +85 +61

Image Type Virtual Erect Real Inverted Real, inverted

Image location Posterior Capsule Biconvex Lens Air

magnification 0.86 0.51 0.92

Field of view 18 Deg 60 Deg 45 Deg

• A real image of the fundus is formed at the slit lamp several centimeters in front of the patient's eye when a high-powered plus lens is positioned in front of the cornea.

• This aerial image of the fundus is magnified by the slit-lamp optics. • The resultant image is real, inverted, and of high quality if a superior high-

power aspherical lens made for this purpose is used• Lens power = + 78 or + 90 D , other lenses= + 60 to 132 D• Field of view = 30 to 40 degrees

Indirect slit lamp biomicroscopy

Technique

• Set the slit lamp magnification to 10X or 16X• Adjust the light intensity to minimum usable,

about halfway• Slit beam-4mm wide• Hold the lens in between the thumb and index

finger approx 5 to 10 mm from the patients cornea• Examine fundus using a joystick• Increase the magnification for a greater detail as

necessary

• Video

• Drawing the slit lamp biomicroscopic view: Done on an inverted fundus chart and paper is turned as

patients gaze direction changes in respective clock hour meridian.

• Evaluating fundus :

Recording Findings

Tips on SLM BIO

• Use the patient’s optic disc diameter as a reference point when determining the retinal lesion’s dimensions.

• Always use a red free filter soon after viewing with normal yellow light

• Work up the optic nerve with high magnification

• Examine macula clearlyWatzke-Allen test:• you place a narrow slit-lamp beam over the fovea, then ask the patient to look

directly into the center of the beam and describe its overall appearance. • If the patient says that the beam looks unbroken and completely rectangular, the

macula is most likely intact. • If, however, he or she reports that the beam appears narrow or distorted in the

center, this could indicate a partial-thickness (lamellar) hole. • Finally, if the patient says the beam as looks broken in the center, he or she may

have a full-thickness hole. • To perform the test accurately, it is helpful to present the beam both horizontally

and vertically• If the macula of the opposite eye appears generally healthy, performing the

Watzke-Allen test in that eye may provide the patient with a point of comparison.

Ophthalmologists health• Compared to family

practice practitioners, eye care professionals report a much higher incidence of neck, back, hand and wrist pain

• Spinal disc prolapse or spinal nerve compression

• Carpal tunnel syndrome• Cervical contractures• Ulnar neuropathy

Remedies:• Sitting in front of patient and

mobilizing the patient’s head instead of doctor moving back and forth

• Use 2 finger method to hold the lens, speculum can be used to keep eyes open

• When sitting behind the slit lamp, take the extra time to raise or lower the patient to a height where examiner’s back remains straight while looking through the oculars.

• Years of performing fundus biomicroscopy with elbow on the table can lead to ulnar neuropathy which can be avoided using a foam pad on the SLM table

Color Anatomic FeatureRed Retinal arteries, retinal

hemorrhage, attached retina, retinal neovascularization

Blue Retinal veins, detached retina, retinal edema

Green Media opacities, vitreous hemorrhage

Yellow Retinal and choroidal exudatesBrown Pigmented lesions, choroidal

detachmentsRed lined with blue Retinal breaks

 Color Coding for Retinal Drawing

•Retinal arterioles• Neovascularization• Vascular anomalies• Attached retina• Vascular tumors•Hemorrhages ( Pre- retinal and retinal)• Open interior of retinal breaks (tears, holes)

FUNDUS DRAWING – RED SOLID

• Open portion of Giant Retinal Tears or large dialyses• Inner portion of thin areas of retina• Open portion of retinal holes in inner layer of retinoschisis

FUNDUS DRAWING- RED CROSSED

• Detached retina

• Retinal veins

• Outlines of retinal breaks

• Outlines of ora serrata

FUNDUS DRAWING – BLUE SOLID

FUNDUS DRAWING – BLUE SOLID

• VR traction tuft

• Outline of lattice

degeneration (inner X)

• Outline of thin area of

Retina

•Inner layer of retinoschisis

•White with or without pressure (label)

•Detached parsplana epithelium anterior to separation of ora serrata

•Rolled edges of retinal tears / inverted flap in GRT (curved lines)

FUNDUS DRAWING – BLUE CROSSLINES

• Opacities in the media

• Vitreous hemorrhage

• Vitreous membranes

• Hyaloid ring

• IOFB

FUNDUS DRAWING- GREEN SOLID

• Asteroid hyalosis

• Frosting or snowflakes on Retinoschisis or lattice degeneration

FUNDUS DRAWING – GREEN DOTTED

• Uveal tissue

• Pigment beneath detached retina

FUNDUS DRAWING – BROWN SOLID

• Pigment epithelial Detachment

• Choroidal melanomas

• Nevus

• Choroidal detachment

FUNDUS DRAWING- BROWN SOLID

• Edge of buckle beneath detached retina

• Outline of Posterior Staphyloma

FUNDUS DRAWING – BROWN OUTLINE

• I/R, S/R hard exudate

• S/R gliosis

• Deposits in the RPE

FUNDUS DRAWING – YELLOW SOLID

• Post-cryo retinal edema

• Substance of long & short ciliary N

• Retinoblastoma Yellow – stippled-• Drusen Yellow Crossed• Chorioretinal coloboma

FUNDUS DRAWING- YELLOW SOLID

• Hyperpigmentation as a result of previous Rx with cryo/laser/Diathermy

• Completely Sheathed vessels

• Pigment within detached retina (Lattice)

FUNDUS DRAWING- BLACK SOLID

• Pigment within choroid or pigment epithelial hyperplasia within attached retina (e.g. RP)

• Pigment demarcation line at margin of attached

and detached retina

FUNDUS DRAWING- BLACK SOLID

• Edge of buckle beneath attached retina

• Outline of Chorio Retinal anastomosis

FUNDUS DRAWING – BLACK OUTLINE

References

• Retina and vitreous- Albert Jacobi• Yanoff and Duker’s Ophthalmology• Post Graduate Ophthalmology-Zia Chaudhri• Theory and Practise of Optics and refraction-AK

khurana• American academy of Optometry-binocular IDO

procedures• Retinal Laser Optical Aids- Indian Journal of

Ophthalmology

Thank You