Learn Together - Seeing Eyes: Gonioscopy- angle recession

Gonioscopy, Contact Hruby Lens, Peripheral Retina
Using The Three Mirror Goldmann Universal Indirect Contact Lens

To perform gonioscopy, contact Hruby lens, or peripheral retinal examinations you are going to need an anesthetic and a cushioning agent. The anesthetic we will be using is 0.5% Proparacaine HCl and the cushioning agent usually used is 2.5% Hydroxypropyl-Methycellulose. It is important that you check the preservative in the cushioning agent. Some use Thimerosal (mercury derivative) that has been found to cause many allergic reactions in patients and has, therefore, been removed from almost all contact lens solutions. The preservative in Hydroxypropyl-Methycellulose is an agent that is somewhat abrasive, i.e., Benzalkonium Chloride (BAK) which has slight allergic reactions. However, it can be very toxic to the cornea.

The cushioning agents come in a number of percentages depending on the procedure one is performing. The lower the percentage used the less corneal insult with resultant staining and less patient discomfort. It is very important that the corneas be examined before AND after the procedure. Use of fluorescein and the biomicroscope, particularly after the procedure, will aid in assessing the degree of patient discomfort. It is always prudent to have some form of artificial tears or soothing drops for the patient to use PRN meaning "as needed".

Under ordinary circumstances, hard contact lens (RGP) wearers should be reminded to take care upon re-inserting the lens since the cornea will be soft after instillation of any type of anesthetic. Soft lens wearers must also take special care not to abrade the cornea with a fingernail. In case of post- procedural fluorescein use, the patient's eyes must be rinsed thoroughly because residual fluorescein will permanently stain soft lenses.

If the procedure has become complicated either due to patient apprehension or previous conditions which might make the eye vulnerable to insult, lenses should not be worn after the procedure and in many cases for 12 to 24 hours, depending on the amount of corneal insult that has occurred. It must be noted that in certain cases, a soft contact lens on the patient's eye in conjunction with an anesthetic and gonio- solution will greatly reduce the insult to the cornea. This has become somewhat obsolete in optometric practice due to the advent of Celluvisc®. This is an over the counter product that is routinely prescribed for dry eye conditions. The product (Carboxymethylcellulose Sodium 1%) is preservative free and has been found to be an excellent substitute for a far more abrasive Gonak® and similar preparations.

CONTRAINDICATIONS

· Patients with known recurrent corneal erosion

· Patients with corneal abrasions

· Patients with corneal keratopathy (i.e., bullous, band, punctate, etc.)

· Certain systemic connective tissue disorders (i.e., Epidermolysis Bullosa)

· Patients with known recurrent acute attacks of anterior uveitis-iritis secondary to say Ankylosing Spondylitis

· Trauma

INDICATIONS

· To prepare a patient with very narrow angles for dilation

· Open angle glaucomas

· Various conditions of the retina or angle anomalies (e.g., diabetes, CRVO, anterior cleavage syndromes--see below)

· To temporarily open a closed angle--see below

· To view the retina, posterior pole (using the contact Hruby portion); or periphery (using various mirrors on the 3-mirror)
Note: The 4-mirror may sometimes be used to view pars plana with widely dilated pupils.

· Trauma

Note--You note that trauma is listed twice. This means that because of possibility of injury to the angle and the iris root during blunt traumas (e.g., blow to the eye during athletic events), it is mandatory to perform gonioscopy. However, the procedure MUST be delayed until any risk of hyphema (blood in the anterior chamber) has been abated. This is true even if there is no injury to the cornea itself.

GOLDMANN "UNIVERSAL" LENS AND MIRRORS

· The center lens is the contact Hruby Lens used for viewing the posterior pole, nerve head, and macula.

· The Trapezoid mirror is used to view the retina slightly posterior to the equator.

· The Half Round mirror is used to view the peripheral retina from the equator out to the ora serrata.

· The Finger Nail mirror is used to view angle and the most anterior retina and ciliary body.

There are differing opinions as to how the light hitting the mirrors should be aligned. Some prefer to have the light beam aligned parallel to the mirror which gives a broader over all view at one time. Still others prefer to use both and some strictly perpendicular to the angle.

ANGLE STRUCTURES

As discussed in class, it is easier to identify the angle structures from posterior (iris side) to anterior (cornea side). Remembering our deviation from this rule comes when identifying the scleral spur, the structures will be presented in the order discussed in class.

· First, identify the iris!

· 1.) Ciliary body - (CB) one of the most easily notable structures of the angle. May vary in color from grayish blue on rare occasions to differing degrees of darkness of brown an is the most posterior structure in the angle; and one which will disappear first as the angle narrows.

· 2.) Scleral spur - (SS) is simply a wedge of visible sclera and is the second structure to disappear as the angle narrows.

· 3.) Trabecular Meshwork "band" - (TM) drainage meshwork allowing flow of aqueous back into the circulatory system, the third structure to disappear as the angle narrows.

· 4.) Schwalbe's line - (SL) end of Descemets membrane of the cornea and is the most anterior structure in the angle and therefore the last structure to disappear as the angle narrows.

· 3a) Finally, Schlemm's canal - usually not seen, though often contains a pigment line or blood within it that helps one determine its actual location within the trabecular band.

ABOVE A WIDE OPEN ANGLE "GRAPHIC" AS SEEN
WITH GOLDMANN INDIRECT LENS

Actual Gonioscopic View of the Most Open Inferior Angle, Light Oriented Parallel

MODIFIED CLASSIFICATION OF ANGLES

· GRADE: IV wide open when the trabeculae and a broad band of ciliary body are visible (35 - 45 degrees)

· GRADE: III-II Intermediate when the trabeculae is visible and the ciliary body is either not seen or is seen as only a narrow band (20-35 degrees)

· GRADE: II-I Narrow when only 1/3 or less of the trabeculae is visible (less than 20 degrees)

· GRADE: I-0 Extremely narrow to closed if only Schwalbe's line can be seen or not at all (10 degrees or less ) Most would agree if Schwalbe's line and at least 1/2 to 3/4 of the trabeculae meshwork is visible for 360 degrees it's usually safe to dilate.

GOLDMANN THREE MIRROR "UNIVERSAL" LENS

Advantages of the Goldmann three mirror are its versatility. The instrument allows the clinician to perform gonioscopic angle evaluations, contact Hruby lens posterior pole examinations, mid-periphery retinal examination, and extreme peripheral retina examinations.

Disadvantages:
1.) Only has one gonio-mirror, therefore the lens must be turned to make a 360 degrees angle evaluation.
2.) Must use a cushioning agent which can be somewhat abrasive and toxic to the cornea depending on the agent used. This is the reason why Celluvisc® is being used in this procedure.
3.) Patients can be somewhat apprehensive about the procedure because of the large looking lens and the fact that it is being placed on their eye.

With the four mirror indirect lens types, i.e., (without a handle/hand-held) Sussman and the new Zeiss then (with handles) Posner and Zeiss a cushioning solution is not needed. You are able to view all 360 degrees of the angle without having to rotate the lens. The magnification and sharpness of the angle being viewed is not, usually, equal to that noted with the Goldmann. The lens can be used with saline solution or better yet, hard contact lens wetting solution or Celluvisc® plus a topical anesthetic. Since there is very little suction created by the lens, it can be difficult to keep centered on the cornea; wetting solution or Celluvisc® will help. The most appropriate time to evaluate the angles with the 4 mirror is right after Goldmann applanation tonometry, since the corneas are already anesthetized from the use of Fluress®.

ANGLE RECORDING:

One can either record the findings of all 360 degrees by a grading method of1 to 4 or perhaps even a better method is to record the actual structures seen and their amount. For example: 0-90 degrees SL + I/2 TM, 90-135 degrees SL+TM +CB and from 135-360 degrees SL+TM

PROCEDURE

· The patient must be given instructions and properly aligned in the slit lamp so the clinician will have to make little to no adjustments once the lens has been placed on the eye.

· The slit lamp's illumination source and the microscope are aligned and in click position, the approximate beam length and width have been set, and the starting magnification is on 10 -16 X which may be changed later.

· Two (ii) drops (gtts) of 0.5% Proparacaine HCl are instilled in the eye on which the lens will be placed, and one (i) drop (gtt) in the fellow eye to help reduce the blink reflex; plus, several drops of artificial tears (like Celluvisc® or (Refresh Plus Cellufresh® Formula) in the fellow eye to prevent corneal desiccation. If evaluation of the retina is necessary, the patient will, or has already been, dilated with the usual mydriatic agents [e.g., one (i) drop (gtt) of 1.0% Tropicamide].

· NOW-- Place approximately (2-3) drops of Celluvisc® (Carboxymethylcellulose Sodium 1%) in the concave surface of the lens and check to make sure there are no bubbles in the solution. If you are using Gonak (2.5% hydroxypropyl methylcellulose) always store the solution upside down to help prevent bubbles from forming.

· Decide which mirror you are going to use before ever thinking about putting the lens on the patient.

· The small finger nail shaped mirror is the mirror to use for gonioscopy evaluation of the angle. To view the inferior angle place this mirror at12:00 o'clock on the eye. You may need something to rest your arm on while performing this procedure (arm rests are available in the lab for that purpose).

· Move the slit lamp slightly out from in front of the eye you are going to put the lens on. Have the patient look up and retract their lower lid either with a finger you are holding the lens with or use your other hand. Place the lower edge of the lens firmly in the lower cul-de-sac, then smoothly position the lens forward on to the globe. Now ask your patient to look straight ahead, the lens should now be centered on your patients eye free of any air bubbles. If there are large bubbles present you will have to remove the lens and start over. Small bubbles usually do not present a large problem and you may still get a clear view.

· To remove the lens have the patient look up and apply gentle pressure, through the lid, at the inferior part of the eye with either your finger or a Q-Tip while gently tilting the lower part of the lens upward and away from the point of pressure to break the vacuum. OR: Have the patient look, as far as they can, toward their nose ( right or left) then apply pressure through the lid from the temporal side while tilting the lens in the same direction of gaze.

TERMS TO REMEMBER

Sampaolesi's Line: Is associated with glaucoma and the exfoliation syndrome though the presence of the line is not exclusively diagnostic. Pigment deposition anterior to Schwalbe's line forms Sampaolesi's line. Also there is often an unusual amount of pigment within the trabeculum.

ANTERIOR CLEAVAGE SYNDROMES: There are a number of clinically identifiable abnormalities which are present from birth. They are predisposing factors for greater likelihood of developing various types of glaucomas.

Posterior embryotoxon - prominent Schwalbe's ring; present in 30% of the normal population and is not necessarily diagnostic; however--

Axenfeld's anomaly - prominent Schwalbe's ring (posterior embryotoxon) with iris strands attached to Schwalbe's line

Rieger's anomaly - prominent Schwalbe's ring with iris strands attached to Schwalbe's line and hypoplasis of the anterior iris stroma

Peter's anomaly - a posterior corneal defect with scar and iris adhesions to the edge of the scar