TOP 100 SECRETS
These secrets are100 of the top board alerts.They summarize the concepts, principles, and most salient details of ophthalmology.
1.Corneal opacification in a neonate has a differential diagnosis of STUMPED: sclerocornea, trauma, ulcers, metabolic disorder, Peter’s anomaly, endothelial dystrophy, and dermoid.
2.A break in Bruch’s membrane is necessary for a choroidal neovascular membrane to form.
3.Posterior fractures most commonly occur in the posteromedial orbital floor.
4.Eyelid trauma that reveals orbital fat has, by definition, violated the orbital septum.
5.The goal of refractive correction is to place the circle of least confusion on the retina.
6.To find the spherical equivalent of an astigmatic correction, add half the cylinder to the sphere.
7.Recheck the axial lengths if the A-scan measures less than 22 mm or more than 25 mm, or if there is more than a 0.3 mm difference between the two eyes. For each 1 mm in error, the calculation is off by 2.5 diopters (D). Recheck keratometry readings if the average K power is <40 D, >47 D, or if there is a difference of more than 1 D between eyes. For every 0.25 D error, the calculation is in error of 0.25 D.
8.According to Kollner’s rule, retinal diseases cause acquired blue-yellow color vision defects, whereas optic nerve diseases affect red-green discrimination.
9.Ultrasound findings of low-to-medium internal reflectivity and collar-button shape can confirm diagnosis of a choroidal melanoma and differentiate it from other choroidal lesions.
10.A junctional scotoma is a unilateral central scotoma associated with a contralateral superotemporal field defect and is caused by compression of the contralateral optic nerve near the chiasm.
11.False-negative errors cause a visual field to appear worse than it actually is. False-positive errors cause a visual field to look better than it actually is.
12.Lesions anterior to the optic chiasm cause unequal visual acuity, a relative afferent papillary defect, and color abnormalities. The optic disc may also have asymmetric cupping and pallor.
13.Always check the pressure in the contralateral eye in a patient with ocular trauma. Asymmetrically low intraocular pressure may be an important clue to a potential ruptured globe.
14.A drop of 2.5% neosynephrine is a simple test to distinguish between episcleritis (these vessels will blanch) and scleritis (these vessels do not)—two entities with very different prognoses and evaluations. Because 50% of patients with scleritis have systemic disease, referral to an internist is necessary for further evaluation.
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15.A patient with a corneal abrasion from a dirty source (contact lens use, tree branch) is at risk for a corneal ulcer and should not be patched while healing.
16.Immediately irrigate any patient with a chemical ocular injury from an alkali or acid, even before checking visual acuity.
17.Recurrent subconjunctival hemorrhages should be evaluated to rule out uncontrolled hypertension or blood dyscrasias.
18.A corneal ulcer is infectious until proven otherwise. You are never wrong to culture an ulcer, and any ulcer not responding to therapy should be recultured.
19.Systemic treatment is necessary for gonococcal, chlamydial, and herpetic neonatal conjunctivitis due to the potential for serious disseminated disease. The mother and her sexual partners must be evaluated for other sexually transmitted diseases.
20.Treatments that are effective for prophylaxis of gonococcal and chlamydial neonatal conjunctivitis include 1% silver nitrate, 0.5% erythromycin, and 1% tetracycline. Silver nitrate is rarely used, however, due to its potential for causing chemical conjunctivitis.
21.Topical steroids may promote herpetic keratitis if viral shedding is coincident with administration.
22.Steroid-induced increases in intraocular pressure occur in about 6% of patients on topical dexamethasone. This risk is higher in patients with known glaucoma or a family history of glaucoma.
23.Ask about gastric bypass procedures in patients who have recent severe dry eye with no discernible cause. Vitamin A deficiency may be the reason.
24.Treat patients for dry eye if they are symptomatic even if their exam is normal. Rose bengal stain will show signs of dry eye earlier than fluorescein stain.
25.If a patient presents with symptoms consistent with recurrent corneal erosion syndrome but no findings of the same, look for an underlying dystrophy, specifically epithelial basement membrane dystrophy.
26.If a patient with a corneal dystrophy is undergoing corneal transplantation but also has a clinically significant cataract, consider staging the cataract extraction a few months after the corneal transplant, offering the patient the advantage of better intraocular lens power calculation and postoperative refractive result. Alternatively, Descemet stripping endothelial keratoplasty (DSEK), which does not alter corneal contour, may be combined with cataract surgery with a predictable refractive outcome.
27.Keratoconus is found more frequently in atopic and Down syndrome patients, possibly related to eye rubbing. All keratoconus patients should be advised to avoid eye rubbing.
28.Most patients with keratoconus can be managed successfully with contact lens wear. Corneal transplantation is highly successful in treating keratoconus patients whose visual needs cannot be satisfied by spectacle or contact lens correction.
29.If there are significant complications with refractive surgery in the first eye, do not proceed with refractive surgery in the fellow eye on the same day.
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30.As many as 30–50% of individuals with glaucomatous optic nerve damage and visual field loss have an initial intraocular pressure measurement less than 22 mmHg.
31.The treatment of both primary open-angle glaucoma (POAG) and low tension glaucoma (LTG) aims to preserve vision and quality of life through the lowering of intraocular pressure.
32.When evaluating a patient with angle closure glaucoma, it is important to look at the fellow eye. Except for cases of marked anisometropia, the fellow eye should have a similar anterior chamber depth and narrow angle. If it does not, consider other nonrelative papillary block mechanisms of angle closure.
33.Lens-induced glaucoma includes phacomorphic, phacolytic, phacoanaphylactic, and lens-particle glaucoma.
34.Patients with sporadic inheritance of aniridia need to be evaluated for Wilms’ tumor, which is associated with 25% of cases.
35.The prostaglandin analogs are the most potent topical intraocular pressure-lowering medications, have a favorable side-effect profile, and are easy to use. However, prostaglandin analogs and miotics are contraindicated in any type of inflammatory glaucoma.
36.Topical medication allergy can present months to years after starting the drop.
37.If a patient’s glaucoma continues to worsen, even with seemingly reduced intraocular pressure during office visits, think noncompliance.
38.Adrenergic agonists except for apraclonidine are absolutely contraindicated in infants. Apraclonidine should be used only as a last resort in healthy infants.
39.Before trabeculectomy surgery, detect high risk patients in whom sudden hypotony should be avoided: those with angle-closure glaucoma, shallow anterior chambers, very high preoperative IOP, or elevated episcleral venous pressure or high myopia. Hemorrhagic choroidals and expulsive hemorrhages are more likely.
40.Patients with traumatic ocular injuries must be evaluated for systemic injuries as well.
41.Patients recovering from a traumatic hyphema are at increased risk for glaucoma and retinal detachments in the future. They need ongoing ophthalmic evaluation for the rest of their lives.
42.Complete evaluation by a pediatrician is mandatory for any infant with a congenital cataract.
43.Patients must have a documented interference in quality of life from a visual standpoint before cataract surgery is indicated.
44.Topical anesthesia allows the surgical patient to recover functional vision more quickly and decreases the risk of some complications compared with retrobulbar anesthesia.
45.Glare testing can reveal significant functional visual problems not noted by Snellen testing.
46.When complications result in the unplanned decision to place an intraocular lens in the ciliary sulcus, remember to lower the power of the implant approximately 0.5 D from what was chosen for capsular fixation to compensate for the more anterior location of the lens.
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47.If amblyopia is associated with an afferent pupillary defect, a lesion of the retina or optic nerve should be suspected and ruled out.
48.Although amblyopia is most effectively treated prior to age 6 years, treatment can be successful at older ages if compliance is good. Atropine penalization can be as effective as patching in the treatment of mild and moderate amblyopia.
49.Treat amblyopia prior to surgery for esotropia.
50.Early treatment for congenital esotropia gives the best chance for the development of binocular vision. Be certain that a patient with a partial accommodative esotropia is wearing the maximum tolerated hyperopic prescription.
51.Check the light reflex test and cover test to determine if a true deviation exists. If the light reflex is in the appropriate place and there is no refixation on cover testing, the patient is orthophoric.
52.A young patient with asthenopia should be evaluated for exophoria at near (convergence insufficiency) as well as checking his or her cycloplegic refraction for undercorrected hyperopia (accommodative insufficiency).
53.Any patient with chronic progressive external ophthalmoplegia needs an electrocardiogram to rule out heart block. These patients may need a pacemaker to prevent sudden death.
54.A patient with acute onset of any combination of III, IV, V, and VI cranial nerve palsies; extreme headache; and decreased vision must be immediately placed on intravenous steroids and referred to neurosurgery for pituitary apoplexy.
55.The signs of endophthalmitis typically appear 1–4 days after strabismus surgery and include lethargy, asymmetric eye redness, eyelid swelling, and fever.
56.When performing a recess-resect procedure, the recession should be done first.
57.Try for fusion of all patients with nystagmus. Aim for exophoria with fusion.
58.All patients with anisocoria need to have their pupils measured in both dim and bright illumination.
59.Smoking is a controllable risk factor for thyroid eye disease.
60.All patients with optic neuritis should experience some improvement in vision. However, 5% of patients who presented with visual acuity of less than 20/200 were still 20/200 or less at
6 months.
61.An abnormal MRI in a patient with optic neuritis is the strongest predictor of developing multiple sclerosis (MS). Fifty-six percent of patients with optic neuritis and a white matter lesion on MRI will develop MS at 10 years.
62.The closer a patient stands to a visual-field testing screen, the smaller the field should be. This is helpful in determining a malingering patient.
63.Any patient suspected of giant cell arteritis should immediately be started on intravenous steroids to prevent involvement of the other eye even if the temporal artery biopsy cannot be done beforehand.
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64.The primary causes of tearing are dry eyes, lower eyelid laxity, and blockage of the lacrimal system.
65.Dacryocystitis must be treated emergently to prevent cellulitis or intracranial spread.
66.CT scanning is superior to MRI in most cases of orbital disease due to better bone-tissue delineation.
67.The most common cause of unilateral or bilateral proptosis is thyroid eye disease (Graves’ ophthalmopathy).
68.A child with rapidly progressive proptosis, inferior displacement of the globe, and upper eyelid edema should have immediate neuroimaging followed by an orbital biopsy to rule out rhabdomyosarcoma.
69.Suspect thyroid-related ophthalmopathy (TRO) in patients with nonspecific redness and inflammation of the eyes even if there is no history of a systemic thyroid imbalance.
70.Most patients with TRO will not require surgery for their disease; it will burn out with time and multiple office visits.
71.Surgical drainage should be undertaken in orbital cellulitis if sinuses are completely opacified, response to antibiotics is poor by 48–72 hours, vision decreases, or an afferent pupillary defect presents.
72.Mild ptosis associated with miosis and neck or facial pain should raise suspicion of a carotid artery dissection, prompting an urgent workup.
73.Acute ptosis and ocular misalignment mandate a careful evaluation of the pupil to rule out pupil-involving third-nerve palsy. A dilated pupil requires neurologic evaluation for a compressive aneurysm.
74.Basal cell carcinoma is the most common malignant eyelid tumor. It has a 3% mortality rate because of invasion to the orbit and brain via the lacrimal drainage system, prior radiation therapy, or clinical neglect.
75.Squamous cell carcinoma may metastasize systemically.
76.Keratoacanthomas often resolve spontaneously but should be removed surgically if near the lid margin to prevent permanent deformity.
77.A patient with a recurrent chalazion in the same spot must be evaluated for sebaceous cell carcinoma.
78.Young patients with xanthelasma should be evaluated for diabetes mellitus and hypercholesterolemia.
79.All patients who have anterior uveitis must have a dilated examination to exclude associated posterior segment disease.
80.Masquerade syndromes should be considered in the very young or elderly and in patients who have uveitis that does not respond to treatment. Uveitis in patients with AIDS is almost invariably part of a disseminated systemic infection. Lymphoma may masquerade as retinitis.
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81.Early signs of chloroquine retinopathy are perifoveal retinal pigment epithelium changes.
82.Never aspirate subretinal exudates for diagnostic purposes in a patient with potential Coats disease unless retinoblastoma has been absolutely ruled out.
83.The five trauma-related breaks are horseshoe tears, operculated tears, dialyses, retinal dissolution, and macular holes.
84.The globe is most likely to rupture at the limbus, underneath a rectus muscle, or at a previous surgical site.
85.Age-related macular degeneration (ARMD) is the leading cause of legal blindness in the Western world. The leading epidemiologic risk factors for ARMD are increasing age, smoking, and genetic predisposition.
86.In the treatment of ARMD, therapeutic paradigms are shifting from destructive laser-based modalities to physiologic pharmacologic therapies such as inhibitors of vascular endothelial growth factor (VEGF).
87.Threshold disease of retinopathy of prematurity (ROP) is five contiguous or eight cumulative clock hours of stage 3 ROP in zone I or II in the presence of plus disease.
88.Patients who weigh <1500 grams at birth and/or are 28 weeks’ gestational age should be screened for ROP at 4–6 weeks after birth or 31–33 weeks postconceptual age.
89.The most common cause of vision loss in diabetic retinopathy is macular edema.
90.Clinically significant macular edema (CSME) is defined as one of the following: retinal thickening within 500 microns of the center of the fovea, hard yellow exudate within 500 microns of the fovea and adjacent retinal thickening, or at least one disc area of retinal thickening, any part of which is within 1 disc diameter of the center of the fovea.
91.Most central retinal artery obstructions are thrombotic; most branch retinal artery obstructions are embolic. Systemic disease must be ruled out in any patient with retinal artery obstruction.
92.Perform iris examination and gonioscopy prior to dilation in a patient with a central retinal vein occlusion. Neovascular glaucoma is the most feared complication of a central retinal vein occlusion.
93.The classic symptoms of a retinal break are flashes and floaters. Pigmented cells or blood in the vitreous strongly suggests the possibility of a retinal break.
94.Risk factors for rhegmatogenous retinal detachments include previous cataract surgery, lattice degeneration, and myopia.
95.Retinoblastoma is the leading eye cancer in children. Over 95% of children with retinoblastoma in the United States and developed nations survive due to early detection and proper management.
96.Most children with unilateral retinoblastoma are managed with enucleation. Most children with bilateral retinoblastoma are managed with chemoreduction.
97.The presence of dilated, tortuous episcleral blood vessels warrants a complete exam to rule out an underlying ciliary body or peripheral choroidal tumor.
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98.Uveal melanomas with epithelioid cells have a poorer prognosis. Seventy percent of uveal metastases are from breast or lung cancer.
99.The most common cause of unilateral proptosis in children is orbital cellulitis; in adults, thyroid-related ophthalmopathy (Graves’ ophthalmopathy).
100.Based on recent data, the treatment of choice for optic nerve sheath meningioma is stereotactic radiotherapy.
I. GENERAL
CLINICAL ANATOMY OF THE EYE
Kenneth B. Gum, MD
CHAPTER 1
1.Name the seven bones that make up the bony orbit and describe which location is most prone to damage in an orbital blow-out fracture.
The seven orbital bones are the frontal, zygoma, maxillary, sphenoid, ethmoid, palatine, and lacrimal. A true blow-out fracture most commonly affects the orbital floor posteriorly and medially to the infraorbital nerve. The ethmoid bone of the medial wall is often broken.
2.Which nerves and vessels pass through the superior orbital fissure? Which motor nerve to the eye lies outside the annulus of Zinn, leaving it unaffected by retrobulbar injection of anesthetic?
The superior orbital fissure transmits the third, fourth, and sixth cranial nerves as well as the first division of the fifth cranial nerve, which has already divided into frontal and lacrimal branches. The superior ophthalmic vein and sympathetic nerves also pass through this fissure. The fourth cranial nerve, supplying the superior oblique muscle, lies outside the annulus. This position accounts for residual intorsion of the eye sometimes seen during retrobulbar anesthesia (Fig. 1-1).
3.A 3-year-old is referred for evaluation of consecutive exotropia after initial bimedial rectus recessions for esotropia performed elsewhere. Review of the operative notes discloses that each muscle was recessed 4.5 mm for a 30-prism diopter deviation. Unfortunately, the child had mild developmental delay and presents with a 25-prism diopter exotropia. You decide to advance the recessed medial rectus of each eye back to its original insertion site. Where is this site in relation to the limbus? Identify the location of each of the rectus muscle insertion sites relative to the limbus.
Reattach each medial rectus muscle 5.5 mm from the limbus. Insertion of the inferior rectus is
6.5mm from the limbus; the lateral rectus is 6.9 mm from the limbus; and the superior rectus,
7.7mm. The differing distances of rectus-muscle insertions from the limbus make up the spiral of Tillaux. An important caveat in developmentally delayed children is to postpone muscle surgery until much later, treating any amblyopia in the interim. Early surgery frequently leads to overcorrection.
4.What is the most common cause of both unilateral and bilateral proptosis in adults?
Thyroid orbitopathy is the most common cause. Many signs are associated with thyroid eye disease, which is probably caused by an autoimmune reactivity toward the epitope of thyroidstimulating hormone (TSH) receptors in the thyroid and orbit. The order of frequency of extraocular muscle involvement in thyroid orbitopathy is as follows: inferior rectus, medial rectus, lateral rectus, superior rectus, and obliques. There is enlargement of the muscle belly with sparing of the tendons.
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