Aravind FAQs

709 Pages·2013·3.14 MB·English

by  Venkatesh, Prajna N.

Aravind
FAQs in
Ophthalmology
Aravind
FAQs in
Ophthalmology
N Venkatesh Prajna
DNB FRCOphth
Director-Academics
Aravind Eye Hospital
Madurai, Tamil Nadu, India
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Aravind FAQs in Ophthalmology
First Edition: 2013
ISBN: 978-93-5090-183-0
Printed at
Preface
The specialty of ophthalmology has developed by leaps and bounds in the
recent past. Excellent comprehensive books are being brought out at
regular intervals, which helps an ophthalmologist to keep abreast with
times. In my 15 years experience as a residency director, I have often
found the need for a concise, examination oriented ready-reckoner, which
would be of use to the postgraduates to answer specifically to the point.
This book aims to fill this gap and serves as a compilation of the frequently
asked questions (FAQs) and the answers expected in a postgraduate
clinical ophthalmology examination. This book should not be misconstrued
as a replacement to the existing standard textbooks. These questions
have been painstakingly gathered over a 10-year period from the collective
experience of several senior teachers at Aravind Eye Hospital, Madurai,
Tamil Nadu, India. Apart from the exam-oriented questions, this book also
contains examples of case sheet writing and different management
scenarios, which will help the students to logically analyze and answer in
a coherent manner. I do sincerely hope that this book helps the postgraduate
to face his/her examination with confidence.
N Venkatesh Prajna
Contents
1. Introduction .................................................................1
1.1 Visual Acuity 1
1.2 Color Vision 10
1.3 Anatomical Landmarks in Eye 14
1.4 Pharmacology 18
1.5 Slit Lamp Biomicroscope 26
1.6 Direct Ophthalmoscope 33
1.7 Indirect Ophthalmoscopy 36
1.8 X-rays in Ophthalmology 40
1.9 Computed Tomography and Magnetic Resonance Imaging 48
2. Cornea .......................................................................55
2.1 Keratometry 55
2.2 Corneal Vascularization 58
2.3 Corneal Anesthesia 60
2.4 Corneal Deposits 63
2.5 Bacterial and Fungal Corneal Ulcer 66
2.6 Acanthamoeba Keratitis 72
2.7 Viral Keratitis 77
2.8 Interstitial Keratitis 80
2.9 Mooren’s Ulcer 82
2.10 Band-Shaped Keratopathy 88
2.11 Adherent Leukoma 91
2.12 Bowen’s Disease 94
2.13 Keratoconus 98
2.14 Stromal Dystrophies—Cornea 107
2.15 Fuch’s Endothelial Dystrophy 117
2.16 Endothelial Disorders and Bullous Keratopathy 121
2.17 Keratoplasty 125
3. Uvea .........................................................................134
3.1 Uveitis—History and Clinical Features 134
3.2 Sympathetic Ophthalmia 150
3.3 Fuch’s Heterochromic Iridocyclitis 152
3.4 Vogt Koyanagi Harada Syndrome 154
3.5 Behcet’s Disease 156
3.6 Investigations in Uveitis 158
3.7 Treatment of Uveitis 172
viii ARAVIND FAQs IN OPHTHALMOLOGY
4. Glaucoma.................................................................178
4.1 Tonometry 178
4.2 Gonioscopy 186
4.3 Glaucoma Diagnostic with Variable Corneal
Compensation (GDx VCC) 192
4.4 Glaucoma Visual Field Defects 194
4.5 Ultrasound Biomicroscopy in Glaucoma 201
4.6 Angle Closure Glaucoma 203
4.7 Management of an Acute Attack of Angle Closure
Glaucoma 212
4.8 Primary Open-Angle Glaucoma 213
4.9 Neovascular Glaucoma 220
4.10 Pigmentary Glaucoma 229
4.11 Pseudoexfoliation Glaucoma 233
4.12 Uveitic Glaucoma 239
4.13 Steroid Induced Glaucoma 242
4.14 Lens Induced Glaucoma 245
4.15 Medical Management of Glaucoma 249
4.16 Newer Drugs in Glaucoma 260
4.17 Lasers in Glaucoma 266
4.18 Trabeculectomy 275
4.19 Modulation of Wound Healing in Glaucoma Filtering
Surgery 289
4.20 Glaucoma Drainage Devices (GDD) 293
4.21 Cyclodestructive Procedures 302
5. Lens and Cataract ..................................................308
6. Retina.......................................................................314
6.1 Fundus Fluorescein Angiography (FFA) 314
6.2 Ultrasonography (USG) 325
6.3 Diabetic Retinopathy (DR) 330
6.4 Lasers in Diabetic Retinopathy 338
6.5 Hypertensive Retinopathy (HTN Retinopathy) 349
6.6 Central Retinal Vein Occlusion (CRVO) 355
6.7 Central Retinal Artery Occlusion (CRAO) 363
6.8 Retinal Detachment (RD) 368
6.9 Endophthalmitis 390
6.10 Retinitis Pigmentosa 398
6.11 Retinoblastoma (RB) 407
6.12 Age-Related Macular Degeneration (ARMD) 414
6.13 Vitrectomy 422
6.14 Central Serous Chorioretinopathy (CSCR) 426
6.15 Angiogenesis 428
CONTENTS ix
7. Neuro-Ophthalmology ............................................430
7.1 The Normal Pupil 430
7.2 Optic Nerve Head 435
7.3 Optic Neuritis 442
7.4 Papilledema 449
7.5 Optic Atrophy 464
7.6 Optic Disk Anomalies 474
7.7 Anterior Ischemic Optic Neuropathy 480
7.8 Oculomotor Nerve 485
7.9 Fourth Nerve Palsy 496
7.10 Abducens Nerve Palsy 500
7.11 Myasthenia Gravis 505
7.12 Nystagmus 513
7.13 Visual Fields in Neuro-Ophthalmology 519
7.14 Cavernous Sinus Thrombosis 523
7.15 Carotico-Cavernous Fistulas 530
7.16 Carotid Artery Occlusion 532
7.17 Ophthalmoplegia 537
7.18 Malingering 543
8. Orbit..........................................................................548
8.1 Ectropion 548
8.2 Entropion 557
8.3 Ptosis 562
8.4 Eyelid Reconstruction 568
8.5 Blepharophimosis Syndrome 576
8.6 Thyroid-Related Orbitopathy (TRO) and Proptosis 577
8.7 Blowout Fractures of the Orbit 597
8.8 Orbitotomies 602
8.9 Botulinum Toxin 606
8.10 Dacryocystorhinostomy 608
9. Pediatric Ophthalmology and Strabismus............610
9.1 Diplopia Charting 619
9.2 Hess Charting 621
10. Miscellaneous..........................................................626
10.1 Vitamin A Deficiency 626
10.2 Localization of Intraocular Foreign Bodies (IOFB) 631
10.3 Community Ophthalmology 641
Case Sheet Writing..........................................................649
Index................................................................................669
1
Introduction
CHAPTER
1.1. VISUAL ACUITY
1. Define visual acuity.
Visual acuity is defined as the reciprocal of the minimum resolvable angle
measured in minutes of arc for a standard test pattern.
2. Define visual angle.
It is the angle subtended at the nodal point of the eye by the physical
dimensions of an object in the visual field.
3. What are the components of visual acuity?
Visual acuity has three components.
i. Minimum visible: Detection of presence or absence of stimulus.
ii. Minimum separable: Judgment of location of a visual target relative
to another element of the same target.
iii. Minimum resolvable: Ability to distinguish between more than one
identifying feature in a visible target. Threshold is between 30 sec
and 1 minute of arc.
4. What are the components of measurement of vision?
i. Visual acuity
ii. Field of vision
iii. Color vision and
iv. Binocular single vision.
5. Who developed classic test chart?
Professor Hermann Snellen in 1863.
6. What is the testing distance? Why do we check at that distance?
The testing is done 6 m (20 ft) away from the target. At this distance,
divergence of rays that enters the pupil is so small that rays are considered
parallel. Hence, accommodation is eliminated at this distance.
2 ARAVIND FAQs IN OPHTHALMOLOGY
7. Describe about the Snellen’s chart.
The letters are:
i. It consists of series of black capital letters on a white board arranged
in lines, each progressively diminishing in size.
ii. Lines comprising letters have such a breadth that they will subtend
at an angle of 1 minute at the nodal point of the eye at a particular
distance.
iii. Each letter is designed such that it fits in a square.
iv. The sides of the letter are 5 times the breadth of constituent lines.
v. At given distance, each letter subtends at an angle of 5 minutes at
the nodal point of the eye.
8. What does normal 6/6 visual acuity represent?
It represents the ability to see 1 min of arc which is close to theoretical
diffraction limits.
9. Explain LogMAR charts.
i. Used for academic and research purposes.
ii. This is a modification of Snellen’s chart, where each subsequent line
differs by 0.1 log unit in the minimum angle of resolution (MAR)
required for that line.
iii. They have equal number of letters in each line.
iv. Used at a distance of 4 meters.
10.What is the procedure of testing visual acuity (VA) using Snellen’s
chart?
i. Patient is seated at a distance of 6 m from the Snellen’s chart
because at this distance the rays of light are practically parallel and
patient exerts minimal accommodation.
ii. Chart should be properly illuminated (not less than 20 foot candle).
iii. Patient is asked to read with each eye separately.
iv. Visual acuity is recorded as a fraction.
– Numerator: Distance of the patient from the chart.
– Denominator: Smallest letters read accurately.
v. When the patient is able to read upto 6 m line, the VA is recorded
as 6/6 – Normal.
vi. Depending on the smallest line patient can read from distance of 6m
VA is recorded as 6/9, 6/12, 6/18, 6/24, 6/36 and 6/60.
vii. If the patient cannot see the top line from 6 m, he/she is asked to
walk towards the chart till one can read the topline.
viii. Depending on the distance at which patient can read the topline, the
VA is recorded as 5/60, 4/60, 3/60, 2/60 and 1/60.
ix. Finger counting:
If patient is unable to read topline even from 1 m, he/she is asked
to count fingers (CF) of the examiner, the VA is recorded as CF-3’,
CF-2’, CF-1’ or CF close to face depending on the distance (in
meters) at which the patient is able to count fingers.