Ординатура / Офтальмология / Английские материалы / Clinical Ocular Pharmacology 5th edition_Bartlett, Jaanus_2008

Figure 19-7 Use of a Jaeger eyelid plate protects the globe from accidental perforation in performing anesthetic injections into the eyelid.

the area to be excised.This allows a decreased volume of anesthetic to be used in a larger surgical area. Moderate pressure should be applied with sterile gauze to allow diffusion of local anesthesia. Gently massaging the area after injection disperses the bolus of anesthetic, helps to restore normal anatomy, and reduces the chance of hematoma.

Approximately 5 minutes after injection, the patient should be evaluated by pinching the lesion or anesthetized

15°

Figure 19-8 Schematic representation of subcutaneous injection. (From Hockenberry. Wong’s clinical manual of pediatric nursing, 6/e, St. Louis: Mosby, An imprint of Elsevier.)

area with tissue forceps. The patient should be able to detect the forceps but not experience any discomfort. Alternatively, the anesthetized area could be tested by pinching it with the original needle; if additional anesthetic is needed, it can be injected from the same syringe. The needle and syringe should be discarded in an appropriate sharps container.

Papilloma and Eyelid Lesion Removal

Eyelid lesions are common and often benign. In most cases the patient desires removal for cosmetic reasons, but occasionally the lesion may interfere with the patient’s spectacle placement or present with a suspicious history that warrants removal for pathologic analysis (Table 19-2). Anesthesia for the surgical removal of most eyelid lesions is accomplished using a pretarsal subcutaneous block. A typical anesthetic agent such as

1% lidocaine with 1:100,000 epinephrine is injected subcutaneously at the base of the lesion with a 27-gauge 0.5-inch needle using the technique described previously (Figure 19-9).

Once local anesthesia has been verified, the lesion should be grasped with tissue forceps and removed at the base using a scalpel, iris scissors, or Westcott scissors.The excised lesion should be placed in a vial of fixative and sent to the laboratory for pathologic evaluation. Hemostasis should be maintained with direct pressure using a cotton swab, or bleeding vessels should be cauterized with a disposable cautery. An antibiotic ointment

Table 19-2

Assessment of an Eyelid Lesion (H-ABCs)

AAvascularity? Malignant growths tend to have Asymmetry? feeder vessels.

Figure 19-9 Subcutaneous injection of 1% lidocaine with epinephrine at base of papilloma provides adequate anesthesia for excision.

should be applied to the area, and the patient should be educated on appropriate postoperative medications and follow-up appointments. Potential complications to removal of an eyelid lesion may include bruising, bleeding, scarring, lid notching, pitting, recurrence, or infection.

Chalazion Incision and Drainage

Anesthesia for chalazion incision and drainage depends on the extent of lipid material and its location. Small to medium-size chalazia anterior to the tarsus require a transcutaneous approach warranting a pretarsal subcutaneous block. If the chalazion is located posterior to the tarsus, however,surgery occurs through the palpebral conjunctiva. After instillation of one drop of 0.5% proparacaine to each eye, the palpebral conjunctiva and eyelid margin should be anesthetized using a sterile cotton-tipped applicator soaked in 4% lidocaine before injection of 1% lidocaine with epinephrine. Large chalazia (>8 mm) and hypersensitive patients may require a regional nerve block at the appropriate branches of the trigeminal nerve (Figure 19-10).

The eyelid may be stabilized with a chalazion clamp before the initial incision.A horizontal incision is typically used for a transcutaneous approach, whereas a vertical incision is used in a transconjunctival approach. The contents of the chalazion are removed with a curette or cotton swab (Figure 19-11), and special care is taken to ensure that the capsule wall is excised with scissors.

A disposable cautery can be used to hyfrecate the base of

Figure 19-10 A retrotarsal block is performed by injecting anesthetic subconjunctivally along the proximal tarsal border.

the capsule to control bleeding. Sutures (e.g., 6-0 or 7-0 nylon) may be required to close the eyelid skin for chalazia anterior to the tarsus. A topical antibiotic ointment is applied postoperatively, and the eye may be pressure patched for up to 6 hours if needed.

Complications of chalazion incision and drainage include risks for infection, bleeding (normally minimal and controlled by direct compression or cautery), pain, loss of cilia, scarring, notching of the eyelid, and recurrence in cases of incomplete excision as well as chronic obstruction of meibomian glands.Alternatives to surgical excision include conservative therapy such as monitoring, lid hygiene, or other procedures such as intralesional steroid injection.

Figure 19-11 Curettage of large chalazion involving the central upper eyelid, transconjunctival approach.Anesthesia was delivered using both retrotarsal infiltration and a supraorbital nerve block.

SELECTED BIBLIOGRAPHY

Bergin DJ.Anatomy of the eyelids, lacrimal system and orbit. In: McCord CD, Tanenbaum M, eds. Oculoplastic surgery, ed. 2. New York: Raven Press, 1987.

Casser L, Fingeret M, Woodcome HT. Atlas of primary eyecare procedures, ed. 2. Stamford, CT:Appleton & Lange, 1997.

Dutton JJ. Atlas of ophthalmic surgery, vol. 2. Oculoplastic, lacrimal and orbital surgery. St. Louis: Mosby-Year Book, 1992.

Dzubow LM, Halpern AC, Layden JJ, et al. Comparison of preoperative skin preparations for the face. J Am Acad Dermatol 1988;19:737–741.

Eggleston St, Lush LW. Understanding allergic reactions to local anesthetics.Ann Pharmcother 1996;30:851–857.

Naguib M, Magboul MM, Jaroudi R, et al.Adverse effects and drug interactions associated with local and regional anaesthesia. Drug Saf 1998;18:221–250.

Stoelting R, Hillier S. Pharmacology & physiology I: anesthetic practice, ed. 2, Philadelphia: Lippincott Williams & Wilkins: 2006.

Tetzlaff JE. The pharmacology of local anesthetics. Anesthesiol Clin North Am 2000;18:217–233.

Wilson RP.Anesthesia. In: Spaeth GL, ed. Ophthalmic surgery: principles and practice. Philadelphia:WB Saunders, 1990: 77–88.

Since the development of the direct ophthalmoscope in the 19th century, practitioners have used mydriatic drugs to facilitate examination of the crystalline lens, vitreous, retina, and optic nerve. With the advent of the binocular indirect ophthalmoscope, three-mirror fundus contact lenses, and other diagnostic instrumentation, a panoramic and stereoscopic view of the fundus from ciliary body to optic nerve has become available to the ophthalmic practitioner. Much of this view, however, is accessible only with the use of mydriatics. The proper use of mydriatics enables the practitioner to identify and diagnose more accurately various abnormalities of the eye. This chapter considers the incorporation of routine pupillary dilation into office practice, anterior chamber angle evaluation before dilation, dilation drug regimens, postdilation procedures, and complications of pupillary dilation.

EXAMINATION ROUTINE

For routine examinations most clinicians dilate patients’ pupils only after most other examination procedures have been performed. Complete ocular and medical histories, visual acuities, external examination, pupillary examination, refraction, biomicroscopy, tonometry, and other routine evaluations precede instilling the mydriatic (Figure 20-1). This approach ensures that dilation does not interfere with the refraction, assessment of accommodation or binocularity, or any other refractive finding. In addition, the predilation examination procedures allow the clinician to identify any cautions or contraindications to dilation. In most routine cases ophthalmoscopy or fundus biomicroscopy is the only procedure remaining after dilation. After drops have been instilled for dilation, the patient may proceed to the reception area, the “dilation room,” or the dispensary for spectacle frame selection while the pupils dilate. While the patient’s pupils dilate, the practitioner can examine the next scheduled patient. In 20 to 30 minutes, after all procedures except dilation have been performed on the second patient and the mydriatic drops instilled, the first

patient can return for ophthalmoscopy and any other indicated procedures.

The placement of dilation procedures toward the conclusion of the routine examination enables the practitioner to perform all of the mydriatic preinstillation examination as a standard routine. All procedures that should be accomplished before instilling the mydriatic (e.g., gross assessment, visual acuity, tonometry, pupil testing, anterior angle evaluation, and drug sensitivity history) occur in a natural and logical sequence.Thus the patient may immediately undergo pupillary dilation if warranted. If the practitioner does not wish to dilate the pupils at this time, an undilated fundus examination can be performed in the usual manner.

INDICATIONS AND

CONTRAINDICATIONS

When the various clinical and legal factors governing patient care are considered, a standard of care (see Chapter 5) emerges that provides for dilated fundus evaluation for virtually all “new” patients presenting for a comprehensive eye examination. Pupillary dilation allows a substantially more thorough evaluation of the ocular media, the fundus (including peripheral retina), and the posterior pole than is possible without dilation.Although it is possible to merely detect the presence of many abnormal conditions through an undilated pupil, a careful internal ocular examination needs to be performed through a dilated pupil to definitively rule out subtle internal ocular conditions.

In rare clinical situations dilation of the pupil may be contraindicated (Box 20-1), but if the patient’s history, signs, or symptoms indicate that dilation is necessary, the practitioner should proceed by following the guidelines given later in this chapter. Legal issues of negligence (failure to dilate) and patient informed consent are extremely important and can play a pivotal role in the selection of patients whose pupils should be dilated or when dilation should be deferred (see Chapter 5).

330 CHAPTER 20 Dilation of the Pupil

Histories (Ocular, Medical, Family)

Visual Acuity

External Examination

Pupillary Examination

Ocular Motility

Refraction

Biomicroscopy

Goldmann Tonometry

Instillation of Mydriatic

Fundus Examination

Figure 20-1 Example of routine examination in which the mydriatic is instilled near the conclusion of the examination.

ANTERIOR ANGLE EVALUATION

Acute angle-closure glaucoma is a rare but well-recognized complication of mydriatic use. Because the risk of such a complication is greatest in eyes with shallow anterior chambers, the practitioner should evaluate the anterior chamber angle before instilling any mydriatic.

Box 20-1 Contraindications to Pupillary Dilation

Iris-supported intraocular lens Subluxated crystalline lens Subluxated intraocular lens

Extremely narrow or closed anterior chamber anglesa History suggesting angle-closure glaucoma, without

surgical or laser interventiona

aDilate with caution.

Adapted from Alexander LJ, Scholles J. Clinical and legal aspects of pupillary dilation. J Am Optom Assoc 1987;58:432–437.

The angle can be assessed by using the shadow test, the slit-lamp method, or most accurately by gonioscopy.

Shadow Test

The easiest and fastest method of evaluating the anterior angle entails using a penlight to illuminate the iris from the side (Figure 20-2). This method is less accurate than the slit-lamp or gonioscopic procedures; nevertheless, it is reliable for identifying critically narrow angles that might be predisposed to angle closure. Furthermore, it is useful in the pediatric age group, when slit-lamp examination or gonioscopy may not be possible. It may easily be integrated into the examination routine while performing pupillary light reflex testing.

The penlight beam is directed across the eye from the temporal side at the level of the iris perpendicular to the line of sight.The entire iris is illuminated if the iris lies in a flat plane (see Figure 20-2A). This is characteristically observed in eyes with deep anterior chambers, such as those in myopia and aphakia, in which the open angle (grade 4) makes a 45-degree angle between the iris and cornea. When the iris is bowed forward or the lens–iris diaphragm is displaced anteriorly, the penlight beam illuminates the temporal iris but a shadow falls on the nasal aspect of the iris in proportion to the convexity of the iris or the displacement of the lens–iris diaphragm.

Although this method of evaluating the anterior angle is reliable in most patients, the practitioner must avoid misinterpretation. It is possible to estimate the angle as being narrower than it actually is because of central shallowing of the anterior chamber. This is especially common in older patients with enlarged lenses. In such eyes the peripheral iris often recedes from the trabecular meshwork, leaving the angle incapable of closure. Properly positioning the penlight exactly perpendicular to the visual axis enhances the accuracy of this method. If the penlight is positioned too far anteriorly or if the eye is deviated temporally, the penlight may illuminate the nasal aspect of the iris directly, thus giving a false-negative result by indicating a wider angle than is actually present.

Slit-Lamp Method

A more accurate method for anterior angle evaluation is the van Herick slit-lamp technique.With the patient at the slit lamp, a vertical slit-lamp beam is placed at the temporal limbus just inside the corneoscleral junction. The slitlamp beam should be as narrow as possible and should be directed toward the eye at an angle of approximately

60 degrees from the direction of the observation microscope (Figure 20-3).The depth of the anterior chamber at the temporal limbus is compared with the thickness of the cornea through which the beam travels and is graded on a scale of 1 to 4. If the depth of the anterior chamber is equal to or greater than approximately one-half the thickness of the cornea, the angle is judged anatomically

332 CHAPTER 20 Dilation of the Pupil

Table 20-1

Classification and Implications of Slit-Lamp Assessment of

Anterior Angle

angle; gonioscopy required

incapable of closure, and the patient can be safely dilated. An anterior chamber depth of less than one-half the corneal thickness indicates a narrow angle, and gonioscopy should be performed to directly view the angle structures and verify that the eye is safe to dilate. This technique is extremely rapid (requiring only seconds) and accurate for estimating the depth of the anterior chamber angle. Also, it tends to correlate well with gonioscopic findings.Table 20-1 shows the classification and implications of the slit-lamp assessment in terms of the risk for angle closure.

Using this technique, grade 1 narrow angles have a prevalence of only 0.64% and grade 2 angles have a prevalence of 1%.The prevalence of grade 1 and grade 2 angles increases with age,but this finding is expected,considering the normal increase of lens thickness with age.The practical implication of the slit-lamp method is that angles graded at 2 or less indicate a risk of angle closure and merit gonioscopic confirmation before dilation of the pupil.

Another quick and useful technique performed at the slit lamp is to place a narrow slit beam entering at a

60-degree angle at the inferior limbus.This beam is observed as it passes from the limbus onto the cornea and iris. A gap between the corneal and iris beams indicates that the two structures are physically separated in space and that the angle is open. If the two beams appear to meet at the angle, then gonioscopy should be performed to directly view the angle structures before dilating.

Gonioscopy

Gonioscopy provides the most definitive assessment of the anterior angle.This procedure allows visualization of the anterior chamber angle structures and thus indicates with greater accuracy the risk of angle closure associated with pupillary dilation. The techniques most commonly used involve use of the Goldmann, Zeiss (Posner), or Sussman gonioprisms (Figure 20-4). Each of these

Figure 20-4 Sussman (top left), Goldmann (top right), and Posner gonioprisms.

gonioprisms allows an indirect view of the anterior chamber angle by reflection through a mirror. Although gonioscopy yields a great deal more information than whether or not an angle is safe to dilate, we only address this one concern here.

When viewed gonioscopically, the normal anterior angle most often appears narrower superiorly and widest inferiorly and has a depth intermediate between these two extremes at the temporal and nasal aspects.The risk of angle closure is inversely proportional to the extent to which the angle structures are visualized during gonioscopy. A conservative estimate of the risk of angle closure is when the posterior trabecular meshwork is obscured. Table 20-2 summarizes the classification and implications of the gonioscopic observations. While observing the angle, the iris configuration should be recorded (i.e., bowed, flat, or concave) (Figure 20-5). In addition, any abnormalities such as synechiae, recession, dense pigmentation, exfoliative debris, neovascularization, or angle dysgenesis should be noted and documented.

In most instances the slit-lamp method of evaluating the anterior chamber depth correlates well with gonioscopy, except when the angle is extremely narrow. The slit-lamp method may be used to screen and select patients in need of gonioscopy; patients having an anterior chamber depth of 0.25 of the corneal thickness or less should generally undergo gonioscopy. If, during gonioscopy, one-half or less of the trabecular meshwork depth is visible in all quadrants, the eye should be considered at risk of angle closure during pupillary dilation.

Notably, however, partial angle closure can occur without

significant elevation of intraocular pressure (IOP) or ocular damage. Thus the widest quadrant of the anterior chamber angle is generally the most critical for evaluation. Despite careful indirect method of gonioscopy, predicting precisely which eyes sustain angle closure on pupillary dilation is still not possible. However, with highresolution ultrasound biomicroscopy the risk of angle closure during pupil dilation can be determined with higher probability. This instrument can also be useful where evaluating atypical angle configurations, such as a plateau iris.

GENERAL GUIDELINES FOR

MYDRIATIC USE

The following general guidelines for the clinical use of mydriatics should enhance the clinical effectiveness of pupillary dilation:

1.Instilling topical anesthesia before the mydriatic enhances patient comfort and reduces tearing from the stinging caused by the mydriatic drops. In addition, if applanation tonometry has been performed immediately before dilation, then the patient is already anesthetized, and any corneal epithelial disruption caused by the tonometer can enhance the dilation.

2.The goal of dilation should be wide and rapid mydriasis. The use of a combination of adrenergic and anticholinergic agents achieves this goal.The single instillation of tropicamide or phenylephrine alone may allow some

Figure 20-5 Major anatomic landmarks in gonioscopy. Schwalbe’s line (SL), trabecular meshwork (TM), scleral spur (SS), and ciliary body (CB).

pupillary constriction on intense light stimulation, such as that received during funduscopy. Furthermore, tropicamide alone may prove less effective in the elderly because of decreased sympathetic pupillary tone. Thus topically administered adrenergic and anticholinergic drugs used in combination produce faster and more complete mydriasis. In most cases pupils obtain maximum mydriasis within 15 to 30 minutes. The combination of phenylephrine and tropicamide is suitable for routine dilation purposes because the drugs have a similar duration of action and because tropicamide is less likely to produce cycloplegia than are most other anticholinergic drugs.

3.Various combinations of mydriatics have been investigated for their efficacy in pupillary dilation while minimizing side effects. The individual agents (usually tropicamide and phenylephrine or tropicamide and hydroxyamphetamine) can be instilled in any order, and instilling the second drug immediately after the first does not seem to adversely influence the drugs’ additive effects for this diagnostic purpose. One commercially available mydriatic combination, 0.2% cyclopentolate with 1% phenylephrine (Cyclomydril), has far too prolonged mydriatic and cycloplegic durations for routine pupillary dilation. Use of this combination requires nearly 8 hours for sufficient accommodation to return to allow reading. In contrast, a combination of 0.25% tropicamide with 1% hydroxyamphetamine (Paremyd) provides satisfactory mydriasis and inhibition of the pupillary light response in young adults, with only minimal paralysis of accommodation. We have had success in combining equal amounts of commercially available 1% tropicamide with 2.5% phenylephrine to produce a solution containing final concentrations of 0.5% tropicamide and 1.25% phenylephrine. One drop of this combination solution is enough to produce adequate pupillary dilation in virtually all patients on whom this combination has been used (see Chapter 8).

4.Although mydriatic combinations give faster and wider dilation, phenylephrine may be used alone for dilation when the patient or practitioner has concerns about the possibility of drug-induced blurred near vision. These adrenergic drugs spare accommodation but usually require more than one instillation and more time for adequate dilation to occur. Also, some

334 CHAPTER 20 Dilation of the Pupil

small amount of pupillary constriction inevitably occurs during examination due to the bright light and lack of sphincter paralysis.

5.Multiple instillations of anticholinergic mydriatics are rarely required to achieve a wide pupillary dilation. The single instillation of a suitable combination of mydriatics usually achieves rapid and complete mydriasis while minimizing the risk of side effects associated with drug overdosages. However, in patients whose pupils may be anticipated to dilate poorly, such as those with poorly controlled diabetes mellitus, surgical pupils, posterior synechia, or darkly pigmented irides, multiple applications may be used.

6.A pupillary diameter of 7 mm is usually adequate to permit most examination procedures to be performed, including peripheral retinal examination using the standard indirect biomicroscope or three-mirror fundus contact lens. However, the desired pupil size depends on what one wants to achieve. For example, the optical coherence tomographer, the Heidelberg retinal tomographer, and GDx instruments can all be used with an undilated pupil; however, some dilation results in improved image quality and ease of use.

7.The goal of dilation should be a maximally dilated pupil. Minimally dilated or pupils that remain in a middilated state pose a risk of pupillary-block glaucoma in eyes with narrow angles that is not present with maximally dilated pupils.

8.Unless specifically contraindicated the pupils of both eyes should be dilated rather than dilating only one eye for initial examinations. Failure to dilate the pupil of the contralateral eye can cause diagnostic errors because lesions considered to be normal variants frequently occur bilaterally. In addition, the contralateral eye can serve as a control, or normal eye, for that individual. Once a lesion has been documented, on subsequent visits the affected eye can be dilated alone, with the unaffected eye being dilated on a routine periodic basis. However, dilating one eye only could be determined by patient preference due to the Pulfrich effect.

9.In patients at risk for systemic side effects from topically administered pharmacologic agents, eyelid closure and manual nasolacrimal occlusion (see Figure 3-6) are reasonable procedures to minimize nasolacrimal drainage of drug and subsequent absorption into the systemic circulation.

DILATION DRUG REGIMENS

Routine Dilation

Adults

For routine use, rapid and effective mydriasis may be obtained in adults by using one drop each of 2.5% phenylephrine and 1.0% tropicamide. As stated previously, this combination is effective in dilating pupils with agerelated miosis in which there is decreased sympathetic

pupillary tone, where the use of tropicamide alone would be less effective.To facilitate drop administration, the two commercially available drugs may be mixed together to form a single solution with final concentrations of 1.25% phenylephrine and 0.5% tropicamide. Drops may be applied to the medial canthus with the lids closed and head tilted back in uncooperative patients. The drug flows into the eye when the patient opens his or her lids.

Children

Effective dilation for patients in the pediatric age group may be obtained by using 0.5% to 1.0% tropicamide and 2.5% phenylephrine, instilled separately or as a combination solution as outlined above. This regimen produces wide mydriasis for fundus examination. Adding 0.5% or 1.0% cyclopentolate produces effective cycloplegia for retinoscopy or subjective refraction. Administration of these eyedrops to the medial canthus with the head tilted back and the eyes closed can be an effective means of ophthalmic drug delivery in uncooperative children. Alternatively, these agents can also be administered together as a spray solution containing 0.5% cyclopentolate, 0.5% tropicamide, and 2.5% phenylephrine.The spray is applied to the closed eyelids and produces mydriasis and cycloplegia comparable with that provided by the same combination of mydriatics administered as eyedrops to the open eye. Moreover, children usually have less avoidance reaction with the spray than with traditional eyedrop instillation.

Neonates and Infants

Ophthalmoscopic examination of premature infants requires wide pupillary dilation and binocular indirect ophthalmoscopy. Because premature infants treated with oxygen concentrations exceeding room air are at increased risk of developing retinopathy of prematurity, binocular indirect ophthalmoscopy of the peripheral retina is required to detect early signs of this disease. Other neonates or infants may require dilation to evaluate congenital cataracts or to search for ocular signs of toxoplasmosis, cytomegalovirus, or herpes.Thus the mydriatics chosen must be effective and safe.

Because of the premature infant’s small body mass and less mature cardiovascular and cerebrovascular status, prudence dictates using the lowest concentration yet the most effective combination of mydriatics for pupillary dilation. A combination of 2.5% phenylephrine and 0.5% to 1.0% tropicamide provides sufficient mydriasis without adverse cardiovascular effects in preterm infants.The use of tropicamide alone, however, does not generally produce a sufficient mydriasis in premature infants. Adding cyclopentolate to the tropicamide regimen improves mydriasis but may contribute to elevated blood pressure and heart rate. Moreover, because of possible gastric secretory inhibition in preterm infants, the concentration of cyclopentolate should be limited to 0.25%. A commercially available combination of 1% phenylephrine and

0.2% cyclopentolate (Cyclomydril) has proven effective and has minimal risk of cardiovascular or gastrointestinal effects in these patients.

To facilitate the application of mydriatics in neonates and infants, a single-instillation solution may be prepared by combining 3.75 ml cyclopentolate 2% with 7.5 ml tropicamide 1% and 3.75 ml phenylephrine 10%.The final solution contains 0.5% cyclopentolate, 0.5% tropicamide, and 2.5% phenylephrine. This combination produces no major side effects and provides an effective pupillary dilation. Alternatively, equal amounts of 1% tropicamide and 2.5% phenylephrine may be mixed together to yield a single combination solution with final concentrations of 0.5% tropicamide and 1.25% phenylephrine. This too should produce adequate pupillary dilation with no major side effects. Again, these solutions can also be applied as a spray. Cyclopentolate, tropicamide, and phenylephrine administered in microdrops (mean drop volume, 5.6 microliters, as opposed to commercially available standard drops) have the same efficacy with a decreased risk for systemic side effects.

Dilation in Patients with Systemic Disease

Because of its risk of adverse pressor effects, the 10% concentration of topical phenylephrine should be avoided for pupillary dilation, especially in patients with cardiac disease, systemic hypertension, aneurysms, and advanced arteriosclerosis. However, mild hypertension is not necessarily a contraindication to the use of the 2.5% concentration phenylephrine.

Patients with Down syndrome are hypersensitive to topically applied anticholinergic agents.The pupils often dilate widely in response to tropicamide, reflecting an imbalance between cholinergic and adrenergic autonomic activity in the iris. Cyclopentolate, scopolamine, homatropine, and atropine should therefore be avoided in these patients if at all possible.

Ectopia lentis may occur as part of the syndrome of homocystinuria and Marfan’s syndrome. Dilate these patients with caution with a weak mydriatic due to the risk of angle closure. Place the patient in a supine position during the fundus assessment.After the examination, confirm that the crystalline lens remains behind the iris and then mydriasis can be reversed by using a miotic, such as 0.5% dapiprazole.

Dilation in Pregnant and Nursing Women

Although the drugs used for routine pupil dilation are not known to have teratogenic effects, common sense dictates that practitioners must use caution in pregnant women because topically administered drugs may be absorbed systemically. In many cases the dilated fundus examination can be postponed until after delivery. However, if the patient must be dilated, tropicamide is the drug of choice.The risk-to-benefit ratio must be carefully

weighed in each individual case. A consult with the patient’s obstetrician/gynecologist may be indicated.

Open-Angle Glaucoma

The management of open-angle glaucoma requires periodic dilation of the pupil for fundus, optic nerve, and visual field examination. Pupillary dilation is essential for the following reasons:

1.Stereoscopic examination of the optic nerve head is essential for the proper long-term management of glaucoma. Critical judgments are often necessary in establishing the initial diagnosis of glaucomatous disc damage, and monocular viewing can easily overlook subtle changes of the nerve head.

2.Accurate evaluation of glaucomatous visual fields requires at least a 3- to 4-mm pupillary aperture so that cataractous changes or miosis do not cause artifactual field loss.

3.Imaging instruments yield higher quality images with larger pupils (e.g., photos, Heidelberg retinal tomographer, GDx, optical coherence tomographer).

4.Miotics may cause peripheral retinal tears with subsequent rhegmatogenous retinal detachment. Periodic dilation for peripheral retinal examination can identify these patients.

Dilation of eyes with exfoliation or pigmentary glau-

coma may liberate pigment into the anterior chamber. Profuse pigment liberation during dilation of such eyes may cause blocking of the trabecular meshwork, with obstruction of aqueous outflow and subsequent elevation of IOP. This elevation of pressure is transient, and pigment can be liberated during pupillary dilation without a concurrent elevation of pressure.The pupils of eyes with exfoliation syndrome generally dilate more poorly than do those in healthy eyes.This situation may result from bonding of the posterior surface of the iris to the preequatorial lens capsule and anterior zonules by exfoliation material or from iris infiltration and fibrosis.

In summary, the combination of phenylephrine and tropicamide generally permits wide mydriasis while minimizing potential elevation of IOP and is recommended for routine clinical use.They may be administered as two separate drops or as a combination solution. Cyclopentolate may be used in addition to provide cycloplegia, if necessary.

Narrow Angle With Intact Iris

Mydriatic-induced angle-closure glaucoma most commonly occurs in elderly patients with narrow angles. It can, however, occur in young patients, and the previous use of mydriatics without adverse sequelae does not necessarily indicate that angle closure will not develop on subsequent dilation.Thus the practitioner should approach the dilation of eyes with narrow anterior angles with the knowledge that some risk exists for angle closure.