Ординатура / Офтальмология / Английские материалы / Comprehensive Ophthalmology_Khurana_2007

Interpretation of results. Results of EOG are interpreted by finding out the Arden ratio as follows:

Normal curve values are 185 or above.

Subnormal curve values are less than 150.

Flat curve values are less than 125.

Uses. Since the EOG reflects the presynaptic function of the retina, any disease that interferes with the functional interplay between the retinal pigment epithelium (RPE) and the photoreceptors will produce an abnormal or absent light rise in the EOG. Thus, EOG is affected in diseases such as retinitis pigmentosa, vitamin A deficiency, retinal detachment and toxic retinopathies. Hence, EOG serves as a test that is supplementary and complementary to ERG and in certain states is more sensitive than the ERG.

VISUALLY EVOKED RESPONSE (VER)

As we know when light falls on the retina, a series of nerve impulses are generated and passed on to the visual cortex via the visual pathway. The changes produced in the visual cortex by these impulses can be recorded by electroencephalography (EEG) (Fig. 21.28). Thus, visually-evoked response (VER) is nothing but the EEG recorded at the occipital lobe. VER is the only clinically objective technique available to assess the functional state of the visual system beyond the retinal ganglion cells. Since there is disproportionately large projection of the macular area in the occipital cortex, the VER represents the macula-dominated response. VER is of two types depending upon the techniques used.

1.Flash VER. It is recorded by using an intense flash stimulation. It merely indicates that light has been perceived by the visual cortex. It is not affected by the opacities in the lens and cornea.

Clinical uses. (i) It can assess the integrity of macula and visual pathway in infants, mentally retarded and aphasic patients. (ii) It can distinguish between cases of organic and psychological blindness (e.g., malingering and hysterical blindness). (iii) It can detect visual potentials in eyes with opaque media.

2.Pattern reversal VER. It is recorded using some patterned stimulus, as in the checker board. In it the pattern of the stimulus is changed (e.g., black squares

go white and white become black) but the overall illumination remains same. The pattern reversal VER depends on form sense and thus may give a rough estimate of the visual acuity.

Normal versus abnormal record of VER. In normal VER record, an initial positive wave is followed by a negative deflection to be followed by larger hyperpolarization, before the potential returns to resting level (Fig. 21.28). Normally, the response is of the order of 10-25 uV and is fully established by the age of 6 months.

Fig. 21.28. Technique of recording visually evoked response (VER) and record of normal VER pattern.

In the lesions affecting the conduction of the nerve impulse by visual pathway (e.g., retrobulbar neuritis) the amplitude is reduced and there is delay in the transmission time. The timing of the response is more reliable than the amplitude.

OCULAR ULTRASONOGRAPHY

Ultrasonography has become a very useful diagnostic tool in ophthalmology. The diagnostic ophthalmic ultrasound is based upon ‘pulse-echo’ technique. Ultrasonic frequencies in the range of 10 MHz are used for ophthalmic diagnosis. Rapidly repeating short bursts of ultrasonic energy are beamed into the ocular and orbital structures. A portion of this signal is returned back to the examining probe (transducer) from areas of reflectivity. The echoes detected by the transducer are amplified and converted into display form. The processed signal is displayed on cathode ray tubes in one of the the two modes: A-scan or B-scan (Fig. 21.29).

(I)

(II)

Fig. 21.29. Ophthalmic ultrasonic A and B scan machine (I) and diagrammatic depiction of echoes produced by normal ocular structures

with ‘A’ and ‘B’ scan ultrasonography (II).

A-scan (Time amplitude). The A-scan produces a unidimensional image and echoes are plotted as spikes.

Interpretation of A-scan. (i) The distance between the two echo spikes provides an indirect measurement of tissue such as eyeball length or anterior chamber depth and lens thickness.

(ii)The height of the spike indicates the strength of the tissue sending back the echo. The cornea, lens and sclera produce very high amplitude spikes, while the vitreous membrane and vitreous haemorrhage produce lower spikes.

B-scan (intensity modulation). B-scan produces twodimensional dotted section of the eyeball. The location, size and configuration of the structures is easy to interpret.

Clinical uses of ocular ultrasound

1.Biometric studies using A-scan to calculate power of intraocular lens to be implanted.

2.Assessment of posterior segment in the presence of opaque media.

3.Study of intraocular and orbital tumours and other mass lesions.

4.Localization of intraocular and intraorbital foreign bodies.

RELATED QUESTIONS

Enumerate the causes of sudden painless loss of

vision.

See page 462

Enumerate the causes of sudden painful loss of vision.

See page 462

Enumerate causes of gradual painless loss of vision.

See page 462

Enumerate the causes of gradual painful loss of vision.

See page 462

What are the causes of transient loss of vision (amaurosis fugax) ?

See page 463

Enumerate the causes of night blindness (nyctalopia).

See page 463

Enumerate the causes of day blindness (hamarlopia).

See page 463

What are the causes of defective vision for near only?

See page 463

Name the common causes of black spots in front of the eyes.

See page 463

What are the causes of flashes of light in front of the eyes (photopsia)?

See page 463

What is the most common cause of micropsia (small size of objects), macropsia (large size of objects) and metamorphopsia (distorted shape of objects) ?

Central chorioretinitis

Enumerate the causes of coloured halos.

See page 463

Enumerate the causes of diplopia.

See page 463

What are the causes of watering from the eyes?

See page 367

Enumerate the common causes of redness of eyes.

Conjunctivitis

Keratitis

Iridocyclitis

Acute glaucomas

Subconjunctival haemorrhage

Endophthalmitis

Panophthalmitis

Ocular injuries

What are the common causes of pain in eyes?

Inflammatory conditions of lids, conjunctiva, cornea, uvea, sclera, endophthalmitis, panophthalmitis

Acute glaucomas

Refractive errors

Ocular injuries

Asthenopia

Enumerate the causes of the foreign body sensation.

Conjunctival or corneal foreign bodies

Trichiasis

Corneal abrasion

Itching in the eyes is a feature of which disease?

Allergic conjunctivitis (marked itching is pathognomonic of spring catarrh).

COMMON OCULAR SIGNS

What are the causes of abnormal head posture?

Paralytic squint

Severe ptosis

Enumerate the causes of madarosis of eyebrows.

Leprosy

Myxoedema

Enumerate the causes of ankyloblepharon.

Ulcerative blepharitis

Burns of lid margins

Enumerate the causes of narrow palpebral fissure.

Oedema of lids

Ptosis

Enophthalmos

Anophthalmos

Microphthalmos

Phthisis bulbi

Atrophic bulbi

Enumerate the causes of wide palpebral aperture.

Proptosis

Buphthalmos

Congenital cystic eyeball

Upper, lid retraction

Facial nerve palsy

Enumerate the causes of lagophthalmos.

Facial nerve palsy

Leprosy

Myxoedema

Enumerate the causes of poliosis (greying of eye lashes).

Vogt-Koyanagi-Harada’s disease

Old age

Vitiligo

Albinism

Enumerate the causes of circumcorneal congestion.

Acute glaucomas

Keratitis and corneal ulcer

Acute iridocyclitis

Enumerate the causes of conjunctival follicles.

Trachoma

Acute follicular conjunctivitis

Chronic follicular conjunctivitis

Benign folliculosis

Enumerate the causes of conjunctival papillae.

Trachoma

Spring catarrh

Allergic conjunctivitis

Giant papillary conjunctivitis

Enumerate the causes of concretions.

Trachoma

Degenerative conditions

Idiopathic

Enumerate the causes of decreased corneal sensations.

Herpes simplex keratitis

Neuroparalytic keratitis

Leprosy

Herpes zoster ophthalmicus

Absolute glaucoma

Acoustic neuroma

Enumerate the causes of superficial corneal vascularization.

Trachoma

Phlyctenular keratoconjunctivitis

Rosacea keratitis

Superficial corneal ulcer

Enumerate the causes of deep corneal vascularization.

Interstitial keratitis

Deep corneal ulcers

Chemical burns

Sclerosing keratitis

After keratoplasty

Enumerate the causes of increased corneal thickness.

Corneal oedema

Enumerate the causes of abnormal corneal surface.

Corneal abrasion

Corneal ulcer

Keratoconus

Enumerate the causes of shallow anterior chamber.

Primary angle-closure glaucoma

Hypermetropia

Malignant glaucoma

Postoperative shallow anterior chamber due to

–Leaking wound

–Ciliochoroidal detachment

Corneal perforation

Intumescent (swollen cataractous) lens

Iris bombe formation

Adherent leucoma

Enumerate the causes of deep anterior chamber.

Aphakia

Total posterior synechiae

Myopia

Keratoglobus

Keratoconus

Anterior dislocation of lens in the anterior chamber

Posterior perforation of the globe

Buphthalmos

Enumerate the causes of nodules on the iris surface.

Granulomatous uveitis (Koeppe’s and Busacca’s nodules

Melanoma of the iris

Tuberculoma

Gumma

Enumerate the causes of rubeosis iridis (neovascularization of iris).

Diabetes mellitus

Central retinal vein occlusion

Chronic iridocyclitis

Sickle-cell retinopathy

Retinoblastoma

Enumerate the causes of iridodonesis.

Dislocation of lens

Aphakia

Hypermature shrunken cataract

Buphthalmos

Enumerate the causes of hyphaema.

Ocular injuries

Postoperative

Herpes zoster iritis

Gonococcal iritis

Intraocular tumour

Spontaneous (from rubeosis iridis).

Enumerate the causes of hypopyon.

Corneal ulcer

Iridocyclitis

Retinoblastoma (pseudohypoyon)

Endophthalmitis

Panophthalmitis

What is diameter of normal pupil ?

Diameter 3 to 4 mm

In infancy pupil is smaller than at birth

Myopes have larger pupil than hypermetropes

Enumerate the causes of miosis.

Effect of miotic drugs (parasympathomimetic drugs, e.g., pilocarpine)

Effect of systemic morphine

Iridocyclitis (narrow, irregular non-reacting pupil)

Horner’s syndrome

Head injury (pontine haemorrhage)

Senile rigid miotic pupil

During sleep

Argyll Robertson pupil

Poisonings

–Alcohol

–Barbiturates

–Organophosphorus compounds

–Morphine

–Carbolic acid

Hyperpyrexia

Enumerate the causes of mydriasis.

Topical sympathomimetic drugs such as adrenaline and phenylephrine

Topical parasympatholytic drugs such as atropine, homatropine, cyclopentolate, tropicamide

Acute congestive glaucoma (vertically oval, large, immobile pupil)

Absolute glaucoma

Optic atrophy

Retinal detachment

Internal ophthalmoplegia

Third nerve paralysis

Belladonna poisoning

Coma

Sympathetic stimulation

–Aortic aneurysm

–Cervical rib

–Mediastinal sarcoma, lymphosarcoma, Hodgkin’s disease and pulmonary carcinoma

–Emotional excitement

Severe anaemia

Adie’s tonic pupil is larger than its fellow

Enumerate the causes of leukocoria (white reflex in pupillary area).

Congenital cataract

Retinoblastoma

Persistent hyperplastic primary vitreous

Retrolental fibroplasia

Toxocara endophthalmitis

Coat’s disease

Enumerate the causes of Marcus Gunn pupil.

(In swinging flashlight test, the pupil on the diseased side dilates on transferring light to it)

Optic neuritis

Optic atrophy

Retinal detachment

Central retinal artery occlusion

Central retinal vein occlusion

Enumerate the causes of subluxation of lens.

Trauma

Marfan’s syndrome

Homocystinuria

Weill-Marchesani syndrome

Enumerate the causes of deposits on anterior surface of lens.

Vossius ring — pigmented ring seen after blunt trauma

Pigment clumps in iridocyclitis

Rusty (orange) deposits in siderosis bulbi

Enumerate the causes of cherryred spot.

Central retinal artery occlusion

Commotio retinae (Berlin’s oedema)

Tay-Sachs’ disease

Niemann-Pick’s disease

Gaucher’s disease

Enumerate the causes of macular oedema.

Trauma

Intraocular operations

Uveitis

Diabetic maculopathy

Enumerate the causes of superficial retinal haemorrhages.

Hypertensive retinopathy

Diabetic retinopathy

Central retinal vein occlusion

Anaemic retinopathy

Leukaemic retinopathy

Retinopathy of AIDS

Enumerate the causes of soft exudates on the retina.

Hypertensive retinopathy

Retinopathy of toxaemia of pregnancy

Diabetic retinopathy

Anaemic retinopathy

LE, PAN and scleroderma

Leukaemic retinopathy

Retinopathy of AIDS

Enumerate the causes of hard exudates on the retina.

Diabetic retinopathy

Hypertensive retinopathy

Coats’ disease

Circinate retinopathy

Enumerate the causes of neovascularization of retina.

Diabetic retinopathy

Eales’ disease

Sickle-cell retinopathy

Central retinal vein occlusion

Enumerate the causes of proliferative retinopathy.

Proliferative diabetic retinopathy

Sickle cell retinopathy

Eales’ disease

Ocular trauma

Differential diagnosis of salt and pepper appearance of fundus.

Prenatal rubella

Prenatal influenza

Varicella

Mumps

Congenital syphilis

Enumerate the causes of arterial pulsations at the disc.

Visible arterial pulsations are always pathological

True pulse waves are seen in:

–Aortic regurgitation

–Aneurysm

–Exophthalmic goitre

Pressure pulse is seen in:

–Glaucoma

–Orbital tumours

What is the significance of venous pulsations at the disc ?

Are visible in 10 to 20% of normal people

Are absent in papilloedema

In which condition capillary pulsations of the optic disc are seen ?

Are seen in aortic regurgitation as a systolic reddening and diastolic paling of the disc.

Enumerate the causes of enlargement of blind spot.

Primary open-angle glaucoma

Papilloedema

Medullated nerve fibres

Drusen of the optic nerve

Juxtapapillary choroiditis

Enumerate the causes of tubular vision.

Terminal stage of advanced glaucomatous field defect

Advanced stage of retinitis pigmentosa

Enumerate the causes of ring scotoma.

Glaucoma

Retinitis pigmentosa

Enumerate the causes of central scotoma.

Optic neuritis

Tobacco amblyopia

Macular hole, cyst, degeneration

Enumerate the causes of bitemporal hemianopia Central lesions of chiasma:

Pituitary tumours (common)

Suprasellar aneurysms

Craniopharyngioma

Glioma of third ventricle

Meningiomas at tuberculum sellae

Enumerate the causes of homonymous hemianopia.

Optic tract lesions

Lateral geniculate body lesions

Lesions involving total fibres of optic radiations

Visual cortex lesions (usually sparing of macula)

Enumerate the causes of binasal hemianopia Lateral chiasmal lesions:

Distension of third ventricle

Atheroma of posterior communicating arteries

Enumerate the causes of altitudinal hemianopia Altitudinal hemianopia refers to loss of upper or more rarely lower halves of field from pressure upon the chiasma. Causes are:

Early loss in upper half of field—intra or extrasellar tumours.

Early loss in lower half of field—suprasellar tumours.

Enumerate the causes of quadrantic hemianopia.

Homonymous upper quadrantinopia (pie in the sky)—temporal lobe lesions involving lower fibres of optic radiations.

Homonymous lower quadrantanopia (pie on the floor)—anterior parietal lobe lesions involving upper fibres of optic radiations.

Quadrantic hemianopia also occurs due to lesions in the occipital cortex involving the calcarine fissure.

Appendix-I

Ophthalmic Clinical Case Sheet

INTRODUCTION

DISEASES OF THE CONJUNCTIVA

A case of Pterygium

DISEASES OF THE CORNEA AND SCLERA

A case of corneal ulcer

A case of corneal opacity

A case of anterior staphyloma

DISEASES OF THE UVEAL TRACT

A case of acute iridocyclitis

A case of chronic iridocyclitis

DISEASES OF THE LENS

A case of senile cataract

A case of congenital/developmental cataract

A case of aphakia

A case of pseudophakia

GLAUCOMA

A case of primary narrow-angle glaucoma

A case of primary open-angle glaucoma

A case of phacomorphic glaucoma

A case of phacolytic glaucoma

DISEASES OF THE EYELIDS

A case of blepharitis

A case of chalazion

A case of stye

A case of trichiasis and entropion

A case of ectropion

A case of ptosis

DISEASES OF THE LACRIMAL APPARATUS

A case of chronic dacryocystitis

DISEASES OF THE ORBIT

A case of proptosis

SQUINT AND NYSTAGMUS

A case of squint

OCULAR INJURIES

A case blunt trauma

INTRODUCTION

Clinical case discussion is the most important method of assessing the students’ clinical acumen. In ophthalmology practical examinations the students are supposed to work-up a long case and/or 2 to 3 short cases with common eye disorders.

Presentation of a long case

Students are supposed to evaluate a long case under following headings:

1.Name, age, sex, occupation and address of the patient

2.Chief complaints

3.History

i.History of present illness

ii.History of past illness

iii.Personal and professional history

iv.Family history

4.General physical and relevant systemic examination

5.Ocular examination

6.Provisional diagnosis

7.Differential diagnosis, if any

8.List of diagnostic tests required

9.Line of management

List of long cases. During the eight weeks clinical posting in ophthalmology department, students should evaluate and write in their clinical case registers, the common long cases. These include a case of—cataract, aphakia, pseudophakia, glaucoma, iridocyclitis, corneal ulcer (bacterial, viral or fungal), corneal opacity, leukocorea, red eye, chronic dacryocystitis or epiphora and anterior staphyloma.