Non-Contact Hruby Lens and
Hand Held Funduscopic Lenses

The Hruby lens is available in both a contact and non-contact version. The non-contact Hruby lens is a high powered plano concave minus 55 diopter lens (-55D) which is available for most slit lamp biomicroscopes as an attachment from either above or below that can be rotated into the line of sight. The lens is aligned and focused by following a grooved track or rail which is positioned directly in front of the eye. The Hruby lens requires that the illumination be aligned with the biomicroscope in the straight ahead position through a dilated pupil [Bock, 1977]. The beams height and width should be set similar to a parallelepiped in order to minimize reflections. The retinal focus is achieved by effectively neutralizing the optical power of the eye and extending the focus of the biomicroscope back to the retina. The view is erect, but is subject to reflections and a restricted field of 5-8 degrees or just larger than one disc diameter. This, plus the need for precise patient fixations and cooperation makes the Hruby lens a difficult procedure for screening the posterior pole. The optic nerve head (optic disc) is approximately 1.5 mm (1500 microns) in diameter or 5.5 degrees horizontally and 7.5 degrees vertically.

The Hruby lens on the Topcon SL-2E slit lamp is a pre-aligned system. This means once the slit lamp and lens have been properly aligned there is basically nothing one needs to do other than move the slit lamp forward until the retina comes into focus. The non-contact Hruby lens is a plano-concave lens. The Topcon SL-2E has a handle focusing mechanism which is for fine focusing. However, if you have good control and good working knowledge of the slit lamp, in most cases, you will find you will use it very little. It can be helpful when fine focusing within the vitreous. Viewing the retina with 16 X magnification gives one close to the same magnified view as seen with the direct ophthalmoscope. Because the lens does not come in contact with the cornea, like a contact Hruby lens, reflections are somewhat of a problem. As always, one must make sure the patient is aligned in the slit lamp properly. The patient must be given instructions regarding fixation. You can use the fixation light which is helpful if you want to follow different vessels to a given location, this is something you will have to practice if you are to become proficient. If you are only wanting to view the optic nerve head, having the patient look right past the tip of your ear and this should align you closely with the nerve head.

PROCEDURE

1.) The plano side of the lens should be toward the examiner and the slit lamp and illumination system should be in click position.

2.) Adjust the slit width to 2 - 3mm and magnification 10 X then from outside (with the patients eyes closed) move the slit lamp forward until the slit appears focused on the patient's lid.

3.) Have the patient open their eyes and give them your fixation instructions.

4.) There should be a red retro-glow within the dilated pupil. Now move the slit lamp forward slowly until retinal vessels are seen.

5.) Once you have located the structure you are wanting to evaluate; you can increase the magnification to 16 X or higher. Look for venous pulsation when viewing the disc.

6.) If you are wanting to view the macula foveal area I suggest you insert the red-free filter for comfort reasons. This is not something you will do on every patients, but rather when it's indicated. You'll notice that with the red-free filter in place the macula foveal area appears yellowish plus you should see the foveal reflex. The red-free or the cobalt blue filters will also make the nerve fiber layer of the retina more visible.

7.) The slit width is narrowed down to an optic section (the slit lamp and illumination system remain in alignment, click position) it will help you evaluate elevations or holes. An optic section of the retina is not the same as the cornea. It is nothing more than a finely focused, narrow slit on the area of concern. You do not get the three dimensional view through the retina as seen when viewing the cornea or crystalline lens. You do get a stereoscopic appreciation for deflections or elevations and transillumination on either side of the optic section in certain conditions.

Locate the optic nerve then give the patient instructions so you can follow the superior and inferior vessels out as far as possible and then back to the optic nerve head. Place the red-free filter in place and find the macula-foveal areas.

FIELD OF VIEW IS SMALL & MAGNIFICATION IS LARGE
THE VIEW SEEN IS A DIRECT IMAGE

Slit Lamp Aspheric Biomicroscopy Indirect Fundus Lenses

These lenses have an advantage over the non-contact Hruby allowing a better view around cataracts. These lenses are double aspheric and come in +90D, +78D, and +60D powers. There is no correct direction for holding the lenses; either side can face the patient. With these indirect fundus lenses magnification increases as power of the lens decreases, similar to that found with condensing lenses utilized for binocular indirect ophthalmoscopy. The +60 D lens gives greater magnification and is preferred by some for examination of the optic nerve and macula. The +90 D lens produces less magnification and larger field of view (30-40 degrees) [Barker, 1987]. However, the slit lamp biomicroscope permits variable magnification which neutralizes this magnification problem. Theoretically, the increased field of view would permit easier examination of the peripheral fundus to the equator and ora serrata. Clinically, if the pupil is fully dilated, the magnification is set on low, and there is good patient cooperation, this can be accomplished with any of the three lenses. The +78 D lens obviously falls in between the +60 D and +90 D lenses in terms of magnification and field view. It is slightly smaller in overall size than the +60 D and noticeably larger than the +90 D lens. The +78 D lens is usually preferred by the novice who feels it is easier to hold and manipulate. Recent report has given preference for the +78 D over the others to study the nerve fiber layer [Litwak, 1990].

One potential disadvantage of the +60 D has to do with its longer focal length and the extent that the slit lamp must be pulled away from the patient in order to focus on the aerial image in front of the condensing lens. Some older model slit lamps may not have enough of a range to bring this image into clear focus. Even the +90 D lens when used on some patients can be challenging.

All three lenses are available either in clear or with a yellow tint. The yellow tint filters the wave-lengths below 480 nm, enhancing patient comfort and acceptance. The yellow tint causes a slight color shift in the appearance of the retina which could cause misinterpretation of optic nerve pallor and makes detection of the macular edema more difficult [Barker, 1987]. In lieu of an actual tint to the condensing lens itself, other products are also available to provide yellow illumination. One version of this consists of utilizing a filter which attaches directly to the slit lamp; another is that of a removable yellow filter which may be attached and detached from the condensing lens itself. The vitreous of the eye can also be examined with these lenses. Remember, the vitreous is anatomically located in front of the retina, therefore, you have to pull the slit lamp farther back towards you to view the vitreous body.

SIMPLE MAGNIFICATION
Emmetropic Eye Is Considered To Be 60 Diopters

MAGNIFICATION = POWER OF THE EYE / POWER OF THE CONDENSING LENS

MAG. = 60D / 90D

MAG. = .666 X MAGNIFICATION OF SLIT LAMP

MAG. = .666 Times 10X

MAG. = 6.66 X (ETC.)

The indirect biomicroscope lens is not intended to take the place of the binocular indirect ophthalmoscopy, but allows you to view an area stereoscopically and with higher magnification than with the binocular indirect ophthalmoscope.

Image Location Using a Funduscopic Lens

Microscope

Aerial Image

+ 78D Lens

LARGER FIELD OF VIEW THAN HRUBY LENS
LESS MAGNIFICATION

Image of the Left Optic Disc and Vessels as Seen With a 90D Lens and Slit Lamp. The Image Seen is Inverted and Perverted. The Magnification is Reduced, but the Field of View is Large.	Direct View of the Left Optic Disc As Seen With a Non-Contact Hruby Lens and Slit Lamp. It Shows Increased Magnification and Reduced Field of View.

Anatomical, direct view of Dr. Riley's right posterior pole.	Indirect, condensing lens view of Dr. Riley's right posterior pole.

78D lenses indirect field of view of the right optic disc and vessels.

 

Slit Lamp Aspheric Indirect Biomicroscope Procedure

1.) Make sure your patient is comfortably adjusted in the slit lamp. Just as though you were going to do a slit lamp examination.

2.) The illumination system and the microscope should be in alignment or click position and start with slit lamp magnification on 10X.

3.) Tell your patient what you are going to do and why. Have the patient close their eyes while you adjust the slit lamp for yourself. Open the slit width to about 2 - 3 mm's. Because of the slit lamps halogen bulbs brightness, keep the illumination on low.

4.) Have the patient open their eyes, give them fixation instructions and focus on the centrally retroilluminated pupil. Then pull the slit lamp back approximately 2 inches.

5.) With the lens between your thumb and index finger place the lens and your index finger against the patients brow. Look around from outside the slit lamp to make sure the light from the slit lamp is going through the lens and into the patients pupil.

6.) If the light is going into the patients pupil you are ready to look through the slit lamp. Slowly pull the slit lamp towards you. If the surface of the indirect lens is in focus you still have to pull the slit lamp back farther. The more the pupil is dilated and the closer the lens is to the patient's eye the larger the field of view.

7.) If you have told the patient to look in the direction of the top of your ear the optic nerve head should be coming into view.

8.) You might notice a reflection in your line of sight, this can be greatly reduced by either tilting the lens slightly, rotating it around its vertical axis or by placing the illumination system slightly out of click. Make sure if you place the illumination system out of click it is not obstructing your view from one of the oculars.

9.) To view the superior retina have the patient look up and tilt the lens in at the bottom an out towards you at the top. It is important to remember; if the patient is looking up you are observing the superior retina. The most anterior part of the superior retina will be located in the inferior part of the lens. If the patient is looking down your are observing the inferior retina. The most anterior part of the inferior retina will be located in the superior part of the lens.

Above Is The Peripheral Retina Of The Right Eye With A Retinal Scar And Vortex Ampullae Located At 9:30 And 10:00 O'clock Respectively.	The Image Seen Within The 90D Lens Will Be Inverted And Perverted With The Most Anterior Part Of The Peripheral Retina Located In The Inferior Part Of The Lens.

To View The Superior Fundus The Lens Must Be Tilted in Toward The Cheek and The Top Out Toward The Examiner

10.) To view the inferior retina have the patient look down. You will have to use your middle or ring finger to retract the upper lid. Tilt the top of the lens toward the patient and the bottom out towards you.

To View The Inferior Fundus The Lens Must Be Tilted in Toward The Brow and The Bottom Out Toward The Examiner. The Middle or Ring Finger is Used to Retract The Upper Lid.

11.) To view the nasal or temporal retina you will need to have the patient look in the direction you are wanting. Rotate the microscope and illumination system as a unit in the opposite direction to the patient's gaze allowing you to get slightly farther into the periphery. The lens is held so it is always perpendicular to the light source.

Suggested Procedure for Indirect Biomicroscopy Examination of the Posterior Pole of the Eye.

The optic nerve head is usually always examined first. The inferior or superior arcades are examined in the order you feel most comfortable with and last the macula foveal areas are examined.

As mentioned before, an optic section of the retina is somewhat different than the cornea. It is nothing more than a very narrow streak of light sharply focused on a given area. It is not only helpful in determining if an area is elevated or is a hole, but is beneficial in detecting and diagnosing a central serous detachment of the macula and drusens of the nerve head. This sharply focus beam of light causes the surrounding area to be transilluminated bring out detail and extent.

The lenses are going to get dirty and oily from the patient's lashes brushing against it and your finger prints. Cleaning the lenses: 1.) Rinse the whole lens off under running tepid water. 2) place several drops of hard contact lens cleaner on the surface. 3.) Wet your finger and clean both surfaces. 4.) Rinse the cleaning solution off completely. 5.) Use a paper towel and just blot the excess water off the surface. Do not rub. There is an anti- reflection coating on the lenses and you will scratch and destroy the clarity of the lenses. 6.) Finally blot the remaining moisture off with a tissue.

Find the optic nerve head and look for venous pulsation, physiological cupping and C/D ratio. Give the patient instructions and scan the superior and inferior vessels out as far as you can and back to the optic nerve head. Have the patient look as far in all directions and see the extent of the retina you are able to view. With the red-free filter in place find the macula-foveal areas and foveal reflex. You should find vortex veins and short ciliary nerves at the equator.

DILATION

Tropicamide is one of the drugs used in the clinic to dilate patients. Tropicamide comes only in 1% or 0.5% ophthalmic solution. The generic equivalent drugs being used are Tropicacyl or Spectro-Cyl. Tropicamide is an anticholinergic drug which blocks the sphincter muscle of the iris and the ciliary muscle resulting in dilation and causes a moderate cycloplegic effect. One should use 0.5% tropicamide and nothing else on patients who have very narrow angles. This will enable satisfactory dilation without substantial risk for angle closure. REASONS FOR USING FUNDISCOPIC LENSES AND NON-CONTACT HRUBY   1.) POSSIBLE PAPILLEDEMA (NERVE HEAD EVALUATION) 2.) POSSIBLE DRUSENS OF THE NERVE HEAD (PSUEDOPAPILLEDEMA) 3.) POSSIBLE NEOVASCULARIZATION OF THE NERVE HEAD (DIABETES) 4.) ESTIMATING THE CUP TO DISC RATIO (GLAUCOMA DIAGNOSIS) 5.) POSSIBLE OPTIC ATROPHY (COLOR AND LACK OF VESSELS) 6.) CYSTOIDAL MACULAR DEGENERATION (SECONDARY TO CATARACT SURGERY, TRAUMA OR PANLASER SURGERY) 7.) MACULAR EDEMA (CENTRAL SEROUS RETINOPATHY) 8.) CHORIORETINAL LESIONS THAT MAY CAUSE RETINAL DETACHMENTS 9.) EVALUATING THE NERVE FIBER LAYER OF THE RETINA (RED-FREE, COBALT) 10.) POSTERIOR VITREOUS DETACHMENT AND SYNERESIS 11.) MACULAR HOLES, CYSTS, HEMORRHAGES, SCARS, PSEUDOHOLES, ETC.

As Requested The Following Are Definitions Or Explanations Of The Above: From: Dr. Larry J. Alexander's text "Primary Care Of The Posterior Segment" 2nd Ed.

1.) Papilledema: Can be a life and vision treating condition. Sometimes referred to as "choked disc" and according to Dr. Alexander "is best defined as optic disc edema secondary to increased intracranial pressure." The condition is usually bilateral though one nerve head may progress faster than the other. Given both nerve heads are distended and confirmed with ultrasonography or neurologic imaging, i.e., CT scan or MRI scan is a sure sign of increased intracranial pressure creating papilledema. The optic nerve sheaths are pushed forward into the vitreous as well as laterally causing the retina to buckle inward at the temporal aspect of the nerve head. This buckling is know as Paton's folds. The disc vessels as they cross the disc margin become obscured as a result of the swelling and edema. Acute rise in intracranial pressure, e.g., caused by a brain tumor, results in grossly swollen disc, flame hemorrhages in the nerve fiber layer, engorged veins, lose of physiological cupping, cotton-wool spots and loss of venous pulsation or the ability for it to be induce. Spontaneous venous pulsation is absent in approximately 20% of normal individuals, hence, spontaneous venous pulsation not being seen is not diagnostic of papilledema. Other causes, severe hypertension causing papilledema and marked reduction of intraocular pressure or extremely high intraocular pressure. Color plates 22 & 23 plus Figures 3-86, 3-87, 3-88

2.) Pseudopapilledema: Not to be confused with pseudotumor cerebri which has bilateral papilledema, but lacks the presence of an intracranial mass. Pseudopapilledema is often used when the nerve heads appear swollen in the absence of elevated intracranial pressure, vascular abnormality, or inflammation. It is a blurring of the disc margins not caused by elevated intracranial pressure. The most classic example of pseudopapilledema is that caused by hyaline bodies (calcium-like globular bodies) of the nerve head. Hyaline bodies, often called drusens of the nerve head are usually located anterior to the lamina cribrosa. Drusens of the optic nerve head have no histiopathologic correlation to retinal drusens and as such are not age-related other than they too become more visible with age. Drusens are spherical refractile structures and refractile bodies transilluminate (glow) when viewed with the slit lamp and a Hruby lens or hand held indirect funduscopic lenses. Ultrasound, B-scan, is most helpful in the diagnosis of buried nerve head drusens. Drusens of the optic nerve head are inherited and will most like be found in other family members. This condition can cause glaucoma like visual field loss and when severe can be visually devastating. There is presently no treatment for the condition. Color plates 11 & 12 and Figures 3-51 & 3-52 Patients with marked hyperopia have nerve heads that appear small and often appear slightly elevated with blurred margins. The absence of hemorrhages, peripapillary retinal edema, and venous engorgement are helpful in ruling out papilledema. Inflammatory optic neuritis (papillitis) may simulate papilledema when it affects the nerve head. Affected patients have marked visual acuity loss and usually there are cells in the vitreous surrounding the disc. Engorged veins, blurring of the disc margins, and retinal hemorrhages are characteristic. This inflammation is usually unilateral.
Figure 3-74

3.) Optic Atrophy: "Degeneration of the optic nerve." The atrophy can be sectoral, partial, or complete. Whenever it occurs patients will have loss of vision in the corresponding area of their visual field. The optic nerve head turns a yellowish to a very white color rather than its normal salmon or pinkish healthy color plus loss of the very small vessels on its surface. There are a numerous conditions which can lead to atrophy of the nerve head. Dr. Alexander breaks the condition down into two primary causes: Inherited familial optic atrophy: Pages 122-126 Acquired optic nerve disease: Dr. Alexander further breaks these conditions down into inflammations of the optic nerve head, which end with the suffix "itis" and "optic nerve edema" conditions that cause swelling of the optic nerve fibers. pages 126-165. Color plate 36

4.) Neovascularization of the nerve head: Neovascularization results secondary to the lack of oxygenated blood. These new blood vessels are fragile and subject to leakage, fibrosis, and hemorrhages. New vessel formations are not uncommon in advanced diabetic retinopathy though there are other causes. When neovascularization of the optic nerve head occurs the new vessels easily grow into the vitreous an leak protein sometimes causing a haziness to the disc borders. These new vessels are subject to trauma and posterior vitreous detachments (PVD) that may lead to intravitreous or retrovitreous hemorrhages. Neovascularization on the disc will face the direction of the hypoxic retina. Diagnosis of the cause is of utmost importance. Color Plates 44 & 46

4.) Posterior Vitreous Detachment (PVD): This topic is not all that simple. The development of a PVD rarely occurs before the age of 45 years, but after that age it seems to occur more frequently in women than men. The condition increases with age, with a prevalence approximately equal to the person's age over 50 years. The term implies that the vitreous behind the vitreous base (the most anterior attachment of the hyaloid membrane to the retina) and the hyaloid membrane separates from the sensory retina. The hyaloid membrane collapses and the space between the retina and the membrane contains liquefied vitreous gel. In most cases, vitreous detachment is classified as a complete or incomplete PVD. This can be further broken down to with collapse or without collapse of the vitreous gel. According to Dr. Alexander, clinically the most common seen PVD is with collapse of the vitreous gel. The hyaloid membrane pulls free from it's attachment to the optic nerve head and this creates the common annular opacity (separation of the ring of Gartner from the optic disc) seen floating in front of the optic nerve head and or retina. See pages 350 & 351 for photo and schematics of complete and incomplete PVD. Color plate 87

5.) Cystoid Macular Edema (CME): According to Dr. Alexander CME usually is secondary to fluid seeping into the unusual arrangement of fibers in Henle's layer, where the internal limiting membrane is the thinnest. The etiology of the fluid accumulation is sometimes obscure. The macula area is very sensitive to fluid accumulation. Since, the macula area is involved the patient experiences a reduction in their visual acuity and in some case have slight metamorphopsia and a prolonged photostress recovery time. There are many ocular conditions which cause CME, e.g., ocular tumors, ocular inflammations, vaso-occlusive disease, post cataract surgery (Irvine-Gass syndrome), idiopathic central serous chorioretinopathy, pars planitis, severe carotid or ophthalmic artery disease, retinitis pigmentosa, YAG laser posterior capsulotomy and retinal surgery. Fluorescein angiography is the definitive diagnostic test and the radiating cystoid spaces of CME present a glow simulating the petals of a flower. Pages 305-306

6.) Central Serous Retinopathy or Idiopathic Central Serous Chorioretinopathy (ICSC): ICSC is a puzzling condition with transient episodes of serous retina or pigment epithelial detachments in the macular area of young to middle-aged individuals who have no common predisposing conditions, such as drusens. The condition is usually unilateral affect males 10 to 1 over females and is more common in whites than none whites. Typically patients with ICSC will have sudden onset of unilateral distortion (metamorphopsia), slight loss of central vision haze over their vision, or slight color perception problems. The best overall view of the dome or elevation of the macula is with the binocular indirect ophthalmoscope. A important characteristic the clinician looks for is a color variation within the macula area. The details of the dome are best observed using a Hruby or Volk lens and high magnification. Because of the fluid, the dome can be transilluminated, using an optic section, which enhances the view. Color plates 75 & 76

7.) Nerve Fiber Layer Changes: Retinal nerve fiber striations are a routine ophthalmoscopic finding. The nerve fibers can be enhanced by using the red free (green) filter or the cobalt blue filter of the ophthalmoscope. It has been reported that nerve fiber layer defects can be identified up to 5 years before visual field abnormalities appear. The striations are best seen at the inferior and superior aspects of the optic nerve head. They are most easily seen in young patients and patients with heavily pigmented fundi (plural for retina). When there is degeneration of the nerve fiber layer they are usually located or easiest seen within 2 disc diameters of the optic nerve head. Figure 3-70

8.) Macular Holes: It is considered that any condition that produces cystoid macular edema may be implicated in the origination of the macular hole. Idiopathic (a condition of unknown origin or cause) macular holes usually occur in patients over 60 years of age. Macular holes are usually divided into two separate categories, lemellar holes (partial thickness hole) and full-thickness (through and through holes).The lemellar hole is the result of the rupture of the thin, inner retinal layer of a macular cyst. There is a slight reddish coloration or the hole with some retention of visual acuity. A full-thickness hole is a complete loss of retina neural (sensory) tissue. It is usually 1/3 to 1/4 disc diameters (DD) in size, reddish in color and surrounded by a grayish edematous cuff of tissue. There are usually yellow deposits in the base of a full-thickness hole, however, they may be transitory. Figures 5-35 & 5-36 plus color plates 77 & 78

9.) Pseudomacular Hole: Pseudomacular holes may be the result of the contraction of the epiretinal membranes with a baring of the tightly bound foveal area. The illusion of a macular hole may be created by the contrast of the whitish epiretinal membrane and the foveal color which creates a sharply circumscribed border around the foveal area. Pseudoholes are usually oval and appear puckered rather than round, lack the presence of yellow deposits in the base, and edematous cuff of neural tissue. Careful examination with the slit lamp and fundiscopic lenses makes the differentiation easier plus the presence of the whitish epiretinal membrane. The pseudohole may reduce the patients visual acuity as a result of the tugging on the neuro tissue in the foveal area.

PERIPHERAL FUNDUS OF THE RIGHT EYE

The short ciliary nerves are usually located near a vortex ampullae which are located at the equator of the eye. Vortex ampullae are very easy to see in blond, light colored eyed patients. This is not always the case in some patients where the only clue you are near a vortex is the presence of pigment migration at and around its base.

You will be asked to find some of the above structures with these lenses. The optic nerve head, venous pulsation, C/D ratio, macula, vortex veins, short ciliary nerves are areas you should be able to find and observe.

Appendix
The latest lenses ©Volk has add to the hand held funduscopic lenses are the Super Field and more recently the Super Pupil and the Super 66. The Super Field is approximately the same the size as the 60 or 78D lenses. The company claims it has the magnification close to the 78 and the visual field size closes to the 90D lens 30-40 degrees. Because of it's size I find it has one of the drawbacks the 78D lens, e.g., when examining the extreme peripheral retina it is more difficult to maneuver within the orbital area. I like the lens it has excellent optics and you will most likely find you can become proficient with any of the lenses. The Super Field must be held correctly unlike the 78, 60, and 90D lenses which either side may face the patient. The Super 66 is approximately the size of the Super Field with magnification between the 78 and 60 diopter lenses. I have not used the Super Pupil. It claims to get a binocular view of the disc of an undilated pupil. Therefore, you will have less magnification, but will have a lager field of view.

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