3 - Clinical Evaluation

Question 1

History and Examination Key Points

Answer 1

1. Patient’s current medications and allergies as well as PMHx and PSHx
   
   1. DM, Cardiac dz, Pulmonary dz, HTN, hemodynamic shock, sleep apnea, Raynaud’s phenomenon, migraine, renal stones, pregnancy, steroid use
2. Symptoms associated with glaucoma → pain, redness, loss of vision, alteration of vision, colored halos around lights
3. Refraction → neutralizing refractive error crucial for accurate perimetry.
   
   1. Hyperopia increased risk of angle-closure
   2. Myopia may be confused with glaucoma and myopic patients increased risk of pigment dispersion
4. External Adnexae → may help determine presence of conditions associated with secondary glaucoma and glaucoma treatment manifestations
   
   1. Tuberous Sclerosis → secondary glaucoma from vitreous hemorrhage, NVG, RD
   2. NF-1, Nevus of Ota, Juvenile xanthogranuloma (yellow/orange papules), Sturge-Weber, Klippel-Trenaunay-Weber syndrome (cutaneous hemangioma over secondarily hypertrophied limb and may involve face), orbital varices (intermittent unilateral proptosis and dilated eyelid veins), CCF fistuals (orbital bruit, EOM restriction, proptosis, pulsating exophthalmos), superior vena cava syndrome (proptosis and facial and eyelid edema and conjunctival chemosis), TED
5. Pupils → May be affected by glaucoma tx (miotics) and may also show evidence of types of secondary glaucoma
   
   1. APD testing can detect asymmetric optic nerve damage though may be difficult and may use subjective brightness test
   2. Corectopia, ectropion uvea → secondary open-angle glaucome and angle-closure glaucoma
6. SLE
   
   1. Conjunctiva → Elevated IOP may show conjunctival hyperemia and may show side effects of prostaglandin analogs and alpha-2 adrenergic agonists (brimonidine)
      
      1. Brimonidine → follicular reaction; papillary conjunctivitis and scarring with foreshortening of conjunctival fornices seen with topical ocular hypotensives
      2. Prior to filtering surgery must assess for subconjunctival scarring; should note presence of filtering bleb → height, size, degree of vascularization, integrity, Seidel test performed postoperatively in case of hypotony
   2. Episclera and Sclera → Dilation of episcleral vessels may indicate elevated episcleral venous pressure
      
      1. Oculodermal melanocytosis → may affect sclera and at risk for glaucoma and ocular melanoma
      2. Scleritis → may be associated with high IOP
   3. Cornea → glaucomas associated with anterior segment anomalies
      
      1. Enlargment of cornea associated with breaks in descemet membrane (Haab striae) commonly found in developmental glaucoma patients
      2. MCE → evidence of acute elevated IOP
      3. Endothelial abnormalities → Krukenberg spindle (pigmentary glaucoma), pseudoexfoliation material, KP (uveitic glaucoma), irregular and vesicular lesions (posterior polymorphous dystrophy), beaten bronze appearance (ICE), large posterior embryotoxin (Axenfeld-Rieger syndrome).
      4. Pachymetry → thin central K risk factor for glaucoma
   4. Anterior Chamber → Note uniformity and depth of AC
      
      1. Iris bombe and plateau iris syndrome deep centrally and flat peripherally
      2. Malignant glaucoma and other posterior pushing glaucoma mechanisms with both peripheral and central shallowness
      3. Presence of inflammatory cells, RBCs, pigment, fibrin should be noted → degree of flare, cell and pigment should be noted prior to dilation and instillation of eyedrops
   5. Iris → Note heterochromia (especially in patients considered for treatment with prostaglandin analog), TID, ectropion uvea, corectopia, nevi, nodules, exfoliative material, early NV (fine tufts around pupillary margin of fine network of vessels on surface adjacent to iris root), sphincter tears, iridodenesis
   6. Lens → May help diagnose lens-related glaucomas
      
      1. Assess for phacodenesis, pseudoexfoliation, subluxation, dislocation, PSC (long-term steroid use), size, clarity, shape, stability
   7. Fundus → Vitreous hemorrhage, effusions, masses, retinovascular occlusions, DR, RD can be associated with glaucomas

Question 2

Gonioscopy Introduction

Answer 2

1. Need gonisocopy due to total internal reflection from tear-air interface → critical angle of 46 degrees reached and light totally reflected back into corneal stroma and prevents direct visualization of angle structures
2. Small space between lens and cornea filled with viscous substance, saline solution, tears
3. May see:
   
   1. microhyphema, hypopyon
   2. iridodialysis
   3. retained AC IOFB
   4. angle precipitates suggestive of glaucomatocyclitic crises
   5. peripheral lens abnormalities
   6. intraocular lens haptics
   7. ciliary body tumors/cyst

Question 3

Direct Gonioscopy

Answer 3

1. Koeppe, Barkan, Wurst, Swan-Jacob, Richardson lens
2. Erect view of angle structures → essential when goniotomies are performed
3. Most easily performed with patient in a supine position and commonly ussd in OR for examining infants under anesthesia

Question 4

Indirect Gonioscopy

Answer 4

1. Light reflected by a mirror within lens
2. May be used with patient in upright position
3. Gives inverted and slightly foreshortened image (makes angle appear little shallower than direct gonioscopy systems) of opposite angle → Right-Left orientation and Up-Down orientation unchanged
4. Goldmann lens → requires viscous fluid for optical coupling with cornea
5. Posterior pressure on lens especially if tilted indents sclera and may falsely narrow angle
6. Posner, Sussman, Zeiss 4-mirror goniolenses → allow 4 quadranta of anterior chamber angle to be visualized without rotation of lens. Goldmann-type lens has approximately same radius of curvature as cornea and optically coupled by patient’s tears
7. Pressure on cornea may distort angle → can detect pressure by noting induced Descemet membrane folds. Pressure may falsely open angle (aq humor forced into angle) → dynamic gonioscopy sometimes essential for distinguishing iridocorneal apposition from synechial closure. Because posterior diameter of goniolenses smaller than corneal diameter, posterior pressure can be used to force open a narrowed angle.
8. Have patient look towards mirror and apply pressure opposite

Question 5

Gonioscopic Documentation and Assessment

Answer 5

1. Perform with dim light and thin short beam of light → minimize light entering pupil as excessive light may result in pupillary constriction and a change in peripheral angle appearance that can falsely open the angle and may prevent identification of narrow or occluded angle
2. Scleral Spur and Schwalbe Line → 2 important angle landmarks most consistently identified
3. Corneal light wedge → allows detection of junction of cornea and TM. 2 linear reflections seen → one from external surface of cornea and junction with sclera; one from internal surface of cornea. 2 reflections meet at Schwalbe Line.
4. Angle closure → peripheral iris obstructs TM and TM not visible. Often difficult to distinguish narrow but open angle from angle with partial closure.
5. Width of angle → determined by convexity of iris, prominence of peripheral iris roll, site of insertion of iris on ciliary face

Question 6

Shaffer System

Answer 6

1. Describes angle between TM and iris
2. Grade 4 → angle between iris and TM 45 degrees
3. Grade 3 → angle between iris and TM 20-45 degrees
4. Grade 2 → angle between iris and TM 20 degrees, Angle closure possible
5. Grade 1 → angle between iris and TM 10 degrees, Angle closure in time
6. Slit → angle between iris and TM less than 10 degrees, Angle closure likely
7. Grade 0 → iris against TM, Angle closure present

Question 7

Spaeth System

Answer 7

1. Includes description of peripheral iris contour, insertion of iris root, angular width of angle recess

Question 8

Blood in Schlemm Canal

Answer 8

1. Schlemm canal usually invisible on gonioscopy
2. Blood enters Schlemm canal when episcleral venous pressure exceeds IOP

Question 9

NVA

Answer 9

1. Fuchs heterochromatic uveitis vessels → fine, branching, unsheathed, meandering
2. NVG → trunklike vessels crossing ciliary body and scleral spur and arborizing over TM. Contraction of myofibroblasts accompanying vessels leads to PAS formation.

Question 10

PAS

Answer 10

1. Important to distinguish PAS from iris processes which are open and lacy and follow normal curve of angle. Synechiae more sheetlike and solid and composed of iris stroma and obliterate angle recess

Question 11

Pigmentation of TM

Answer 11

1. Pigmentation of TM increases with age and marked in individuals with dark irides
2. Pigmentation may be segmental and usually more marked in inferior angle
3. Pattern of pigmentation varies over time especially in PDS
4. Heavy pigmentation → PDS or PEX
5. Sampolesi Line → pigment deposition anterior to Schwalbe Line often present in PEX
6. Other causes of pigmentation of TM → melanoma, surgery, trauma, inflammation, hyphema, angle closure

Question 12

Angle Recession

Answer 12

1. Abnormally wide ciliary body band
2. Increased prominence of scleral spur
3. Torn iris processes
4. Marked variation of ciliary face width and angle depth in different quadrants of same eye

Question 13

Blunt Trauma

Answer 13

1. Cyclodialysis → separation of CB from SS may require UBM if small cleft identified. Gonioscopy reveals gap between SS and CB

Question 14

Optic Nerve Anatomy

Answer 14

1. Consists of 1.2-1.5M axons of retinal ganglion cells
2. Average diameter of ONH 1.5-1.7mm and expands to 3-4mm upon exiting globe due to axonal myelination and beginning of optic nerve sheath. Axons separated into fascicles within ON with intervening spaces occupied by astrocytes
3. 3 RGC types
   
   1. Magnocellular → large diameter, sensitive to changes in dim illumination (scotopic conditions), largest dendritic field, Motion perception
   2. Parvocellular → 80% of all ganglion cells, smaller diameter, Color vision, discriminate fine detail, process information of high spatial frequency, most active under higher luminance conditions, concentrated in central retina
   3. Koniocellular (bistratisfied) → blue-yellow colors, activated by short-wavelength perimetry
4. Arcuate fibers → more susceptible to glaucomatous damage
5. Anterior optic nerve 4 layers:
   
   1. Nerve fiber Layer
   2. Prelaminar
   3. Laminar → continuous with sclera and composed of lamina cribrosa (fenestrated CT that allow transit of neural fibers through sclera)
   4. Retrolaminar → beginning of axonal myelination
6. Lamina cribrosa → main structural support for optic nerve; collagen, elastin, laminin, fibronectin
7. Between ONH and adjacent choroid and scleral tissue lies rim of CT → ring of Elschnig

Question 15

Blood Supply to Optic Nerve

Answer 15

1. Arterial supply of anterior optic nerve → from branches of ophthalmic artery via 1-5 posterior ciliary arteries → posterior ciliary arteries course anteriorly from ophthalmic artery and divide into 10-20 SPCA prior to entering globe
2. Posterior ciliary artery → divide into medial and lateral group before branching into SPCA
3. SPCA → supply peripapillary choroid, and most of anterior optic nerve
4. Circle of Zinn-Haller → noncontinuous arterial circle exists within perineural sclera from SPCA
5. CRAO → penetrates optic nerve ~10-15mm behind the globe; few intraneural branches except for small branch within retrolaminar region which may anastomase with pial system; supplies superficial NFL
6. Prelaminar region → supplied by SPCA and branches of Zinn-Haller
7. Laminar region → Zinn-Haller
8. Retrolaminar region →

Question 16

Cilioretinal Artery

Answer 16

1. From SPCA and supplies temporal retina NFL

Question 17

Glaucomatous Optic Neuropathy

Answer 17

1. Consists of loss of axons, blood vessels, glial cells → loss of tissue starts at level of lamina cribrosa and more pronounced at superior and inferior poles of optic nerve head. In many cases, structural optic nerve changes may precede detectable functional loss
2. Decreased optic nerve head perfusion and/or disturbance of vascular autoregulation may also contribute to optic nerve damage in glaucoma
3. High magnification lenses for assessment → 60D, 78D, 90D
   
   1. 60D lens → height of slit adjusted to vertical diameter of disc = disc diameter read directly from scale
   2. 78D lens → scale reading multiplied by 1.1
   3. 90D lens → scale reading multiplied by 1.3
4. Normal optic disc ranges from 1.5 - 2.2 mm in diameter
5. Direct ophthalmoscope MAY NOT give sufficient stereoscopic detail of ONH
6. Indirect ophthalmoscope used for children and uncooperative patients though NOT as detailed for assessing ONH as SLE method
7. ONH → will see progressive cupping and pallor within cup, BUT NOT pallor of remaining rim tissue
8. Confounding ONH cupping seen in:
   
   1. congenital pits of optic nerve head
   2. coloboma
   3. morning glory syndrome
   4. arteritic ischemic optic neuropathy
   5. compressive optic neuropathy
9. Most patients progress relatively slowly though others have aggressive disease with fast deterioration which can eventually result in substantial VF loss unless appropriate interventions take place. Progressive structural damage may occur despite lack of detectable VF deterioration → thus structural changes have been shown to predict future functional deterioration in glaucoma patients.

Question 18

Ophthalmoscope Signs of Glaucoma - Asymmetry

Answer 18

1. Asymmetry of ON Cupping (diffuse neuroretinal rim thinning) → Unusual in normal eyes in absence of disc asymmetry
   
   1. Vertical C:D ratio normally between 0.1 and 0.4 (5% of ppl without glaucoma may have C:D ratios > 0.6)
   2. Asymmetry of C:D ratio of more than 0.2 may be due to disc asymmetry or more commonly glaucomatous changes
   3. Increased size of cup may be familial trait and also seen in high myopia. Oblique insertion of optic nerve into globe in high myopia may cause a tilted appearance and is challenging when trying to assess glaucomatous damage

Question 19

Localized Loss of Neuroretinal Rim

Answer 19

1. Localized loss of neuroretinal rim → typically inferior and superior temporal poles of ON in glaucoma leading to vertically elongated cup.
   
   1. ISNT rule → normal eye Inferior thickest > Superior > Nasal > Temporal. If rim widths DO NOT follow this pattern, there should be increased concern for presence of focal loss of rim tissue though NOT SPECIFIC and may be seen in normal eyes too.
   2. Deep localized notching where lamina cribrosa visible at disc margin → acquired optic disc pit
   3. Nasalization of CRA and CRV seen as cup enlarges

Question 20

NFL Hemorrhages

Answer 20

1. 1/3 of glaucoma patients develop NFL hemorrhage
2. NFL Hemorrhages usually followed by localized notching of rim and VF loss → some glaucoma patients have repeat NFL hemorrhages
3. Important prognostic sign for development of progression of VF loss → requires evaluation and follow-up.
4. May also be caused by DM, PVD, BRVO, anticoagulation therapy

Question 21

RNFL Loss

Answer 21

1. Axons in NFL may be visualized with red-free illumination
2. Diffuse loss → generalized reduction of RNFL brightness with reduction of normal difference between I&S Vs. T&N poles. More common in glaucoma than focal loss but also more difficult to observe.
3. Localized loss → Wedge-shaped defects emanating from optic nerve head in an arcuate pattern

Question 22

Peripapillary Atrophy

Answer 22

1. Alpha Zone → present in most normal eyes as well as in eyes with glaucoma. Irregular hypo/hyper pigmentation of RPE
2. Beta Zone → More common in glaucoma; atrophy of RPE and choriocapillaris leading to increased visibility of choroidal vessels and sclera

Question 23

Optic Nerve Head Documentation

Answer 23

1. Glaucoma diagnosis requires longitudinal monitoring and detection of progressive damage over time
2. Simultaneous stereophotography or monoscopic photographs excellent for recording appearance of optic nerve head
3. Assessment subjective and shows large interobserver and intraobserver variation
4. Spectral domain OCT → improved spatial resolution and image acquisition speed
5. RNFL thickness from OCT → may detect glaucomatous damage in some eyes before the appearance of VF defects and to be predictive of future VF loss in glaucoma suspect eyes
6. Ganglion cell complex = RNFL + Ganglion cell + IPL → macular parameters able to distinguish glaucomatous eyes from healthy subjects

Question 24

Visual Field and Perimetry

Answer 24

1. Automated static perimetry → current standard method; quantification of VF sensitivity enables VF defects by comparison with normative data
   
   1. Threshold sensitivity performed at a number of test locations using white stimuli on a white background → known as standard automated perimetry (SAP).
2. Manual kinetic perimetry → used in patients who are unable to perform automated test
3. Factors affecting perimetry:
   
   1. Patient attentiveness
   2. Perimetrist → instruct patient what to expect, how long test will be, when to blink, what stimulus will look like and where it might appear. Advise patients that stimulus likely to be barely visible throughout test, more than half of stimuli will not be visible. All this can decrease patient’s anxiety and improve cooperation. Perimetrist can instruct patient that patient can pause test. Patient should be monitored during test to ensure proper positioning and fixation and perimetrist should intervene if necessary.
4. Background luminance
5. Stimulus luminance
6. Size of stimulus
7. Patient refraction
   
   1. Presbyopic patients
   2. Center patient close to correcting lens to reduce rim artifact
8. Pupil size → <2.5mm reduces light entering eye

Question 25

Automated Static Perimetry

Answer 25

1. SITA → Swedish interactive threshold algorithm uses prior information from previous evaluations of healthy individuals and persons with disease to generate a probability distribution function representing probabilities that the visual field sensitivity will be of particular value at a particular visual field location. As test progresses, distribution adjusted according to whether or not person being tested responds to stimulus presentations. This continues until the PDF is within small range at which point mean of distribution is selected as threshold sensitivity estimate. PDFs adjusted for age, VF location tested, sensitivity values of neighboring test locations, results of previous stimulus presentations.
2. SITA Fast → more difficult for patient because test stimuli tend to be closer to patient’s threshold.
3. 24° and 30° threshold tests → test central field using a 6° grid. Test points 3° above and 3° below the horizontal midline.
4. 10-2 → test central 10° of visual field and tests every 1° - 2° enabling one to follow more test points within central island and improve detection of progression.

Question 26

Interpretation of Visual Field

Answer 26

1. High percentage of false-positives is MOST detrimental to a visual field test → >15% are likely unreliable and nonrepresentative of patient’s true field status.
2. High fixation loss rate > 25% indicative of an unreliable field
3. False negative measures tendency of patient to fail to press button even when a visible stimulus has been presented → although a high false negative rate could indicate an inattentive patient, damaged areas of visual field show increased variability which can lead to high false positive rates → false negatie rates can be elevated in abnormal fields regardless of the attentiveness of the patient THUS visual field tests should NOT be disregarded because of high false negative rates.
   4.