PREFACE
Much of the information in this book can be found in many other ophthalmology textbooks. The table of contents is similar to that of other books in print. So why bother to write this ophthalmology text? The value of this book is in the unique manner in which the material is presented, continuing the tradition the Secrets Series has established in numerous other specialties. The question-and-answer “Socratic method” format reflects the process by which a large portion of clinical medical education takes place. Our purpose is not to displace the comprehensive textbooks on ophthalmology in the shelves of clinicians and students. Instead, we hope that we have filled a useful spot beside them. We greatly appreciate the efforts of the talented contributors who have shared their wisdom and experiences to help fill this void.
We have received much positive feedback on the first three editions of this book. We have enjoyed updating Ophthalmology Secrets, and we hope that clinicians and students will enjoy this book and find it valuable.
Janice A. Gault, MD, FACS
James F. Vander, MD
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TOP 100 SECRETS
These secrets summarize the concepts, principles, and most salient details of ophthalmology.
1. The goal of refractive correction is to place the circle of least confusion on the retina.
2. To find the spherical equivalent of an astigmatic correction, add half the cylinder to the sphere.
3. Recheck if the axial length 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 intraocular lens (IOL) power calculation is off by 2.5 diopters (D). Recheck keratometry
readings if the average K power is <40 D or >47 D or if there is a difference of more than 1 D between eyes. For every 0.25-D error, the IOL power calculation is in error by 0.25 D.
4. According to Kollner’s rule, retinal diseases cause acquired blue-yellow color vision defects, whereas optic nerve diseases affect red-green discrimination.
5. 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.
6. False-negative errors cause a visual field to appear worse than it actually is. Falsepositive errors cause a visual field to look better than it actually is.
7. 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.
8. 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.
9. Immediately irrigate any patient with a chemical ocular injury from an alkali or an acid, even before checking visual acuity. Normalize the pH before examining the patient to prevent further damage to the eye.
10. Rule out uncontrolled hypertension or blood dyscrasias in patients with recurrent subconjunctival hemorrages.
11. A corneal ulcer is infectious until proven otherwise. You are never wrong to culture an ulcer; any ulcer not responding to therapy should be recultured.
12. Systemic treatment is necessary for gonococcal, chlamydial, and herpetic neonatal conjunctivitis because of the potential for serious disseminated disease. The mother and her sexual partners must be evaluated for other sexually transmitted diseases, including HIV.
13. 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, because of its potential for causing chemical conjunctivitis.
14. Topical steroids may promote herpetic keratitis if viral shedding is coincident with administration.
15. 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.
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16. Patients may be symptomatic with dry eye even with a normal slit lamp exam.
17. Ask about gastric bypass procedures in patients who have recent severe dry eye with no discernible cause. Vitamin A deficiency may be the reason. Similarly, patients after gastric bypass may present with Wernicke-Korsakoff syndrome (nyastmus, diplopia, ptosis and mental confusion) due to vitamin B1 deficiency.
18. If a patient presents with symptoms consistent with recurrent corneal erosion syndrome but no findings on slit lamp exam of the same, look for an underlying dystrophy, specifically epithelial basement membrane dystrophy.
19. 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, which does not alter corneal contour, may be combined with cataract surgery with a more predictable refractive outcome.
20. Corneal opacification in a neonate has a differential diagnosis of STUMPED: sclerocornea, trauma, ulcers, metabolic disorder, Peter’s anomaly, endothelial dystrophy, and dermoid.
21. Most patients with keratoconus can be managed successfully with contact lens wear. Corneal transplantation is very successful in treating patients whose visual needs are not satisfied with glasses or contact lens correction.
22. As many as 30% to 50% of individuals with glaucomatous optic nerve damage and visual field loss have an initial intraocular pressure measurement less than 22 mm Hg.
23. The treatment of both primary open-angle glaucoma and low-tension glaucoma aims to preserve vision and quality of life through the lowering of intraocular pressure.
24. 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.
25. Patients with sporadic inheritance of aniridia need to be evaluated for Wilms tumor, as it is found in 25% of cases.
26. Allergy from topical medications can present months to years after starting the drop.
27. If a patient’s glaucoma continues to worsen, even with seemingly reduced intraocular pressure during office visits, think of noncompliance.
28. Before trabeculectomy surgery, identify high-risk patients in whom sudden hypotony should be avoided: those with angle-closure glaucoma, shallow anterior chambers, very high preoperative intraocular pressure, elevated episcleral venous pressure, or high myopia. Hemorrhagic choroidals and expulsive hemorrhages are more likely.
29. Patients with traumatic ocular injuries must be evaluated for systemic injuries as well. 30. Posterior fractures most commonly occur in the posteromedial orbital floor.
31. 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.
32. 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 possible ruptured globe.
33. Complete systemic evaluation by a pediatrician is mandatory for any infant with a congenital cataract.
34. Patients must have a documented functional interference in quality of life from a visual standpoint before cataract surgery is indicated.
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35. Glare testing can reveal significant functional visual problems even in patients with excellent visual acuity on Snellen testing.
36. Amblyopia is a diagnosis of exclusion. If amblyopia is associated with an afferent pupillary defect, a lesion of the retina or optic nerve should be suspected and ruled out.
37. The critical period of visual development is from birth through age 6 to 7 years. Amblyopia is most successfully treated during this time. However, treatment can be successful at older ages with good compliance. Atropine penalization can be as effective as patching.
38. 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.
39. 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.
40. A young patient with asthenopia should be evaluated for exophoria at near (convergence insufficiency) as well as for his or her cycloplegic refraction for undercorrected hyperopia (accommodative insufficiency).
41. 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.
42. A patient with acute onset of any combination of third, fourth, fifth, and sixth cranial nerve palsies; extreme headache; and decreased vision must be immediately placed on intravenous steroids and referred to neurosurgery for pituitary apoplexy.
43. The signs of endophthalmitis typically appear 1 to 4 days after strabismus surgery and include lethargy, asymmetric eye redness, eyelid swelling, and fever.
44. Before evaluating for strabismus, make sure patients with double vision have binocular diplopia. Strabismus does not cause monocular diplopia.
45. Always consider myasthenia gravis and thyroid eye disease in patients presenting with diplopia and normal pupils.
46. When performing surgery on both oblique and rectus muscles, hook the obliques first. 47. In a recess–resect procedure, the recession should be done first.
48. If a patient has a significant deviation in primary gaze or an abnormal head posture, strabismus surgery is indicated in most incomitant strabismus cases.
49. Try for fusion of all patients with nystagmus. Aim for exophoria with fusion. 50. Smoking is a controllable risk factor for thyroid eye disease.
51. 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.
52. An abnormal magnetic resonance imaging (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 within 10 years.
53. 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.
54. Any patient suspected of giant cell arteritis should immediately be started on high doses of steroids to prevent involvement of the other eye even if the temporal artery biopsy cannot be done beforehand.
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55. Dacryocystitis must be treated emergently to prevent cellulitis or intracranial spread of the infection.
56. Computed tomography (CT) scanning is superior to MRI in most cases of orbital disease owing to better bone–tissue delineation.
57. The most common cause of unilateral or bilateral proptosis is thyroid eye disease (Graves ophthalmopathy). Most patients with thyroid-related ophthalmopathy (TRO) will not require surgery for their disease; it will burn out with time.
58. The most common cause of unilateral proptosis in children is orbital cellulitis.
59. 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.
60. Suspect TRO in patients with nonspecific redness and inflammation of the eyes even if there is no history of a systemic thyroid imbalance.
61. Myositis, a nonspecific inflammation of an extraocular muscle, can be distinguished from thyroid-associated ophthalmopathy (TAO) by the location of muscle inflammation. TAO demonstrates thickening of the muscle belly, but only myositis shows thickening of the tendon insertion as well.
62. Persistent proptosis and progression of orbital infection while on intravenous antibiotics for orbital cellulitis should prompt a repeat CT scan to rule out an orbital abscess.
63. The sinuses are the most common source of an orbital infection. The ethmoid sinus is the most frequent culprit as its lateral wall is the thinnest orbital wall, the lamina papyracea.
64. Surgical drainage should be undertaken in orbital cellulitis if sinuses are completely opacified, response to antibiotics is poor by 48 to 72 hours, vision decreases, or an afferent pupillary defect presents.
65. Mild ptosis associated with miosis and neck or facial pain should raise suspicion of a carotid artery dissection, prompting an urgent workup.
66. 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.
67. Basal cell carcinoma is the most common malignant eyelid tumor. It has a 3% mortality rate because of invasion into the orbit and brain via the lacrimal drainage system, prior radiation therapy, or clinical neglect.
68. Squamous cell carcinoma may metastasize systemically.
69. Keratoacanthomas often resolve spontaneously but should be removed surgically if near the lid margin to prevent permanent deformity.
70. Rule out sebaceous cell carcinomas in a patient with a recurrent chalazion in the same spot.
71. Young patients with xanthelasma should be evaluated for diabetes mellitus and hypercholesterolemia.
72. All patients who have anterior uveitis must have a dilated examination to exclude associated posterior segment disease.
73. Consider masquerade syndromes in the very young, the elderly, and in patients who have uveitis that does not respond to treatment. Uveitis in patients with acquired immunodeficiency syndrome is almost invariably part of a disseminated systemic infection. Lymphoma may masquerade as retinitis.
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74. Never aspirate subretinal exudates for diagnostic purposes in a patient with potential Coats disease unless retinoblastoma has been absolutely ruled out. It may take as long as 1 to 2 years for exudation to clear after successful treatment of the abnormal peripheral retinal vessels.
75. The five trauma-related breaks are horseshoe tears, operculated tears, dialyses, retinal dissolution, and macular holes.
76. The globe is most likely to rupture at the limbus, underneath a rectus muscle, or at a previous surgical site.
77. A break in the Bruch membrane is necessary for a choroidal neovascular membrane to form.
78. 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.
79. 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.
80. When ROP reaches ETROP Study Type 1 (high-risk disease), indirect laser photocoagulation dramatically reduces the risk of blindness.
81. Newborns weighing less than 1500 g at birth and/or born at or before 28 weeks’ gestational age should be screened for ROP at 4 to 6 weeks after birth or 31 to 33 weeks postconceptual age and followed until the retinal vascularization has fully matured.
82. The most common cause of vision loss in diabetic retinopathy is macular edema.
83. Neovascularization of the iris is an ominous finding in proliferative diabetic retinopathy and requires prompt treatment with panretinal photocoagulation, intravitreal anti- vascular endothelial growth factor (VEGF) injections, or both.
84. Clinically significant macular edema is defined as one of the following: retinal thickening within 500 μm of the center of the fovea, hard yellow exudate within 500 μm of the fovea and adjacent retinal thickening, or at least one disc area of retinal thickening, any part of which is within one disc diameter of the center of the fovea. It is based on fundus exam and is NOT related to visual acuity or optical coherence tomography findings.
85. 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.
86. First-line treatment for macular edema from retinal venous occlusive disease is intravitreal anti-VEGF injections. However, there is an emerging role for intravitreal corticosteroid treatment, especially in refractory cases.
87. In patients with central retinal venous occlusions, argon laser photocoagulation is indicated only when neovascularization develops; it is not for prophylaxis.
88. Perform iris examination and gonioscopy before dilation in a patient with a central retinal vein occlusion. Neovascular glaucoma is the most feared complication of a central retinal vein occlusion.
89. Branch and central retinal venous occlusions are classified as ischemic or nonischemic. Patients with ischemic occlusions lose vision primarily from macular edema. Vision loss in nonischemic occlusions is due to macular nonperfusion, vitreous hemorrhage, tractional retinal detachments, and neovascular glaucoma.
90. 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. Risk factors for rhegmatogenous retinal detachment (RRD) include previous cataract surgery, lattice degeneration, myopia, trauma, family history, and fellow eye with an history of an RD.
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91. Pneumatic retinopexy for an RRD should be avoided if patients are at high risk of significant vitreoretinal traction, i.e., early PVR, highly elevated flap tears, multiple tears, lattice degeneration, or sizable vitreous hemorrhage.
92. Retinoblastoma is the leading eye cancer in children. About 98% of children with retinoblastoma in the United States and developed nations survive owing to early detection and proper management.
93. Most children with unilateral retinoblastoma have a somatic mutation and are managed with enucleation or intra-arterial chemotherapy.
94. Most children with bilateral retinoblastoma have a germ-line mutation and are managed with intravenous or intra-arterial chemotherapy.
95. The presence of dilated, tortuous episcleral blood vessels warrants a complete exam to rule out an underlying ciliary body or peripheral choroidal tumor.
96. 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.
97. Uveal melanomas with epithelioid cells have a poorer prognosis. Seventy percent of uveal metastases are from breast or lung cancer.
98. Most periocular lymphomas are B cell, extranodal marginal zone lymphoma, also known as mucosal-associated lymphoid tissue lymphoma.
99. Management of orbital lymphoma is largely based on two factors: the particular histologic subtype and the stage of disease.
100. Based on recent data, the treatment of choice for optic nerve sheath meningioma is stereotactic radiotherapy.