Ординатура / Офтальмология / Английские материалы / Comprehensive Ophthalmology_Khurana_2007

Enumerate the lesions which can result from a blunt trauma to the eye (contusional injury).

1.Lids: Ecchymosis, Black eye, Avulsion of the lid, Traumatic ptosis

2.Orbit: Fracture of the orbital walls, Orbital haemorrhage, Orbital emphysemas

3.Lacrimal apparatus: Laceration of canaliculi, Dislocation of lacrimal gland

4.Conjunctiva: Subconjunctival haemorrhage, Chemosis, Lacerating tears of the conjunctiva

5.Cornea: Abrasion, Partial or complete corneal tear, Deep corneal opacity

6.Sclera: Scleral tear

7.Anterior chamber: Traumatic hyphaema, Collapse of the anterior chamber following perforation

8.Iris, pupil and ciliary body:Traumatic miosis, Traumatic mydriasis, Radiating tears in iris stroma, Iridodialysis, Traumatic aniridia, Traumatic cyclodialysis, Traumatic uveitis

9.Lens: Vossius ring, Concussion cataract, Early rosette cataract, Late rosette cataract, Total cataract, Subluxation of the lens, Dislocation of the lens

10.Vitreous: Traumatic vitreous degeneration, Traumatic vitreous detachment, Vitreous haemorrhage

11.Choroid: Rupture of the choroid, Choroidal haemorrhage, Choroidal detachment, Traumatic choroiditis

12.Retina: Commotio retinae (Berlin’s oedema), Retinal haemorrhages, Retinal tears, Retinal detachment, Traumatic macular oedema, Traumatic macular degeneration

13.Optic nerve

Laceration of the optic nerve

Optic nerve sheath haemorrhage

Avulsion of the optic nerve

What are the effects of a perforating ocular injury?

1.Mechanical effects in the form of wounds of different parts of the eyeball

2.Introduction of infection may result in:

Purulent iridocyclitis

Endophthalmitis

Panophthalmitis

3.Post-traumatic iridocyclitis

4.Sympathetic ophthalmitis

What is siderosis bulbi ?

Siderosis bulbi refers to the degenerative changes produced by an iron foreign body retained inside the eyeball.

The iron particles undergo electrolytic dissociation. The iron ions combine with the intracellular proteins and produce degenerative changes. Epithelial structures of the eye are most affected.

What are the features of siderosis bulbi ?

1.Orangish or rusty deposits arranged radially in a ring in the anterior capsule and anterior epithelium of the lens

2.Greenish or reddish brown staining of the iris

3.Pigmentary degeneration of the retina

4.Secondary open-angle glaucoma due to degenerative changes in the trabecular meshwork

What is chalcosis ?

Chalcosis refers to the specific changes produced by the alloy of copper in the eye.

Copper ions from the alloy are dissociated electrolytically and deposited under the membraneous structures of the eye. Unlike iron ions, these do not enter into chemical combination with intracellular proteins and thus produce no degenerative changes.

What are clinical manifestations of chalcosis?

1.Kayser-Fleischer ring in cornea

2.Sunflower cataract

3.Deposition of golden plaques in retina

What are the methods of localizing an intraocular foreign body (IOFB):

1.Radiographic localization

1.Limbal ring method

2.Specialized radiographic techniques, e.g., Sweet and Dixon’s method

2.Ultrasonographic localization

3.CT Scan

What is sympathetic ophthalmitis?

Sympathetic ophthalmitis is a serious bilateral granulomatous panuveitis which follows a penetrating ocular trauma. The injured eye is called the exciting eye and the fellow eye which also develops uveitis is called the sympathizing eye.

What are the predisposing factors favouring development of sympathetic ophthalmitis?

1.A perforating wound

2.Wounds in the ciliary region (the so-called dangerous zone) are more prone to it.

3.Wounds with incarceration of the uveal tissue are more vulnerable

4.It is more common in children than in adults

5.It is more common in the absence of suppuration. In fact, it does not occur when actual suppuration develops in the injured eye

What are the early features of sympathetic ophthalmitis?

Photophobia

Lacrimation

Transient blurring of near vision

Mild ciliary tenderness

A few fine keratic precipitates

Name the measures to prevent occurrence of sympathetic ophthalmitis?

1.Early excision of the injured eye with no vision

2.Meticulous repair of the wound under microscope followed by systemic and topical steroids should be undertaken in an eye with hope of saving useful vision.

Why alkali burns are more serious than the acid burns?

Alkalies penetrate deep into the tissues unlike acids (which cause instant coagulation of all the proteins which then acts as a barrier and prevents deep penertration) and thus produce more damage.

What are the effects of ultraviolet radiations on the eye ?

1.May produce photophthalmia

2.May be responsible for senile cataract

What are the effects of infra-red radiations on the eye?

Photoretinitis (solar macular burn or eclipse burn)

Darkroom procedures (DRPs) form an essential part of examination of the eyes in modern ophthalmic practice. Consequently, this section has been given a special slot in the undergraduate as well as postgraduate examinations. Most of the darkroom procedures have been described vividly with the support of self-explanatory illustrations. Common darkroom procedures are:

Oblique illumination examination

–Loupe and lens examination

–Slit-lamp biomicroscopy

Gonioscopy

Transillumination

Retinoscopy

Ophthalmoscopy

OBLIQUE ILLUMINATION,

GONIOSCOPY AND

TRANSILLUMINATION

OBLIQUE ILLUMINATION

Oblique illumination also known as focal illumination, is a method for examination of the structures of the

anterior segment of the eye. Karl Himly (1806) was the first to employ the technique of oblique illumination examination. In it, a zone of light is made to fall upon the structure to be examined so that it is brilliantly illuminated and stands out with special clarity as compared to the surroundings which remain in shadow.

There are two main methods of focal illumination:

Loupe and lens examination; and

Slit-lamp examination.

Loupe and lens examination

Optical principle. It is based on the principle that when an object is placed between a convex lens and its focal point, its image formed is virtual, erect, magnified and on the same side as the object.

Prerequisites. (1) Darkroom, (2) source of light, (3) condensing lens of +13 D, (4) corneal loupe of +41 D, made with two planoconvex lenses each of 20.5 D (×10 magnification) (Fig. 23.1).

Procedure (1) Light source is placed about 2 feet away, laterally and slightly in front of the patient’s eye (2) Light is focused on the structure to be examined with the help of +13 D condensing lens,

held in one hand (3) The examination is carried out with the help of corneal loupe. The loupe is held between thumb and forefinger of the second hand, the fourth and fifth fingers are supported on the patient’s forehead, while the middle finger is used for elevating the upper lid (Fig. 23.2). The loupe is brought close to the patient’s eye till the illuminated area is focused. The observer should also move his or her eyes as close to the loupe as possible to have a better view (4) By changing the position of the condensing lens and loupe, various structures of the anterior segment can be examined one by one.

Fig. 23.1. Corneal loupe.

Fig. 23.2. Technique of loupe and lens examination.

Use of binocular loupe. The corneal loupe may be replaced by a binocular loupe (Fig. 23.3), which gives the added advantage of stereoscopic view and easy manoeuvring, as normally it is fixed to the examiner’s head by a band. However, the magnification achieved with binocular loupe is much less than that of uniocular corneal loupe.

Fig. 23.3. Binocular loupe.

Slit-lamp examination

Slit-lamp biomicroscope was invented in 1911 by Gullstrand. Today, biomicroscopy forms an invaluable and indispensable part of ophthalmological examination.

Parts. Slit lamp consists of following three parts (Fig. 23.4):

1.Observation system (Microscope)

2.Illumination system (Slit-lamp)

3.Mechanical system (Engineering support)

Fig. 23.4. The slit-lamp.

Optics

It works on the same principle as a compound microscope.

The objective lens (+22 D) is towards the patient, whose eye forms the object. The objective lens consists of two planoconvex lenses with their convexities facing towards each other.

The eyepiece is +10 to +14 D and is towards the examiner.

The illuminating system can be adjusted to vary the width, height and angle of incidence of the light beam.

Slit-lamp biomicroscopy routine. While performing slit-lamp biomicroscopy, following routine may be adopted (Fig. 23.5):

1.Patient adjustment. Patient should be positioned comfortably in front of the slit-lamp with his/her chin resting on the chin rest and forehead opposed to head rest.

2.Instrument adjustment. The height of the table housing the slit-lamp should be adjusted according to patient’s height. The microscope and illumination system should be aligned with the patient’s eye to be examined. Fixation target should be placed at the required position.

3.Beginning slit-lamp examination. Some points to be kept in mind are:

Fig. 23.5. Technique of slit-lamp examination.

i.Examination should be carried out in semidark room so that the examiner’s eyes are partially dark adapted to ensure sensitivity to low intensities of light.

ii.Diffuse illumination should be used for as short a time as necessary.

iii.There should be a minimum exposure of retina to light.

iv.Medications like ointments and anaesthetic eyedrops produce corneal surface disturbances which can be mistaken for pathology.

v.Low magnification should be first used to locate the pathology and higher magnification should then be used to examine it.

Start with diffuse illumination and examine the lid margins, bulbar conjunctiva, limbus, cornea, tear film, aqueous, iris and the lens one by one.

Methods of illumination. There are 7 basic methods of illumination using the slit-lamp as described by Berliner:

1.Diffuse illumination. A diffuse broad beam of light is used, and a general view of the anterior segment of eye is observed.

2.Direct illumination. The slit beam and microscope are focused on the same area, and examination is performed. Changes in the corneal stroma and epithelium are better noted by this technique.

3.Indirect illumination. The slit beam is focused on a position just beside the area to be examined. Corneal microcysts and vacuoles can be best observed by this method.

4.Retroillumination. Light is reflected off the iris or fundus, while the microscope is focused on the cornea. This technique is especially helpful in detecting corneal oedema, neovascularization, microcysts and infiltrates.

5.Specular reflection. Here the angle between the slit-lamp and microscope is increased to 60°, i.e., angle of incidence = angle of reflection. Changes in the endothelium like polymegathism, guttate, etc. can be viewed by this method.

6.Sclerotic scatter. It utilizes the phenomenon of total internal reflection. The slit beam is focused at the temporal limbus, and as it passes through the cornea, it outlines any subtle stromal or epithelial opacities which may lie in its path.

7.Oscillatory illumination of Koeppe. In this, the beam is given an oscillatory movement by which it is often possible to see minute objects or filaments, especially in the aqueous which would otherwise escape detection.

GONIOSCOPY

Owing to lack of transparency of corneoscleral junction and total internal reflection of light (emitted from angle structures) at anterior surface of cornea it is not possible to visualize the angle of anterior chamber directly. Therefore, a device (goniolens) is used to divert the beam of light and this technique of biomicroscopic examination of the angle of anterior chamber is called gonioscopy.

Types of goniolens.: (i) Indirect goniolens provides a mirror image of the opposite angle, e.g., Goldmann (Fig. 23.6) and the Zeiss goniolens; (ii) direct goniolens provides a direct view of the angle. Koeppe goniolens is the most popular type.

Procedure. The patient is seated upright on the slitlamp. A drop of 1 percent methylcellulose is placed in the concavity of the goniolens and with the patient looking up, one edge of the lens is positioned in the lower fornix. The upper lid is elevated and the patient is instructed to look straight ahead. The lens is rotated into position against the eye. When checking the lateral and medial angles, the slit beam should be horizontal and when checking the superior and inferior angles, the slit beam should be vertical.

The angle structures (Fig. 23.7) seen from behind forwards are (Fig. 23.7) :

1.Root of the iris,

2.Anteromedial surface of the ciliary body (ciliary band),

3.Scleral spur,

4.Trabecular meshwork and Schlemm’s canal and

5.Schwalbe’s line

Applications of gonioscopy

1.Classification of glaucoma into open angle and closed angle based on configuration of the angle.

2.Localization of foreign bodies, abnormal blood vessels or tumours in the angle.

3.Demonstration of extent of peripheral anterior synechiae and hence planning of glaucoma surgery.

4.Direct goniolens is used during goniotomy.

Fig. 23.6. Goldmann’s goniolens (A) and technique of gonioscopy (B)

Fig. 23.7. Structures forming angle of the anterior chamber.

Gonioscopic grading of angle width

See page 205

TRANSILLUMINATION

Herein an intense beam of light is thrown through the conjunctiva and sclera or pupil and illumination is observed in the pupillary area.

1.Trans-scleral techniques. The beam of light is thrown through the sclera. Normally, the pupil emits a red glow but in the presence of a solid mass (e.g., intraocular tumour) in the path of light, the pupil remains black as the beam is obstructed by the mass.

2.Transpupillary technique. The beam of light is allowed to pass obliquely through the dilated pupil. Normally the pupil is well illuminated but in detached retina, a grayish reflex is seen.

RELATED QUESTIONS

Who invented the technique of oblique illumination

examination ?

Karl Himly (1806) was the first to employ the technique of oblique illumination examination.

Who invented the slit-lamp ?

Gullstrand

What is the power of the condensing lens used in

loupe and lens examination technique?

+13Ds

What is the power of a corneal loupe?

+41Ds

What is the magnification of a corneal loupe?

10x

What are the advantages and disadvantages of a binocular loupe over the monocular corneal

loupe?

Advantages

Binocular loupe provides stereoscopic vision.

It is easier to use.

Disadvantages

Magnification is less.

What is the optical principle of oblique

illumination?

It is based on the principle that when an object is placed between a convex lens and its focal point, the image formed is virtual, erect, magnified and on the same side.

What are the prerequisites for loupe and lens examination technique?

A darkroom

Source of light

A condensing lens of +13 Ds

A corneal loupe of +41 Ds

Where is the source of light placed in oblique

illumination examination ?

The source of light is placed slightly laterally and 2 feet in front of the patient’s eye.

Enumerate the structures which can be examined with a slit-lamp without any additional aid?

Lid margin

Conjunctiva

Cornea

Sclera

Anterior chamber

Iris and pupil

Lens

Anterior part of vitreous

What are the advantages and disadvantages of slit-lamp examination over loupe and lens

examination?

Advantages

1.Magnification can be increased and decreased.

2.Stereoscopic vision improves depth perception.

3.Aqueous flare can be better demonstrated.

4.Applanation tonometry and gonioscopy can be performed with the slit-lamp.

Disadvantages

1.Slit-lamp is very costly.

2.It is not handy.

Enumerate a few ocular conditions where transillumination test helps in the diagnosis.

1.Intraocular tumour

2.Retinal detachment

3.Vitreous haemorrhage

RETINOSCOPY

The procedure of determining and correcting refractive errors is termed as refraction. It is an art that can only be mastered by practice. The refraction comprises two complementary methods, objective and subjective.

OBJECTIVE REFRACTION

The objective methods of refraction include retinoscopy, refractometry and keratometry.

RETINOSCOPY

Definition

Retinoscopy also called skiascopy or shadow test is an objective method of finding out the error of refraction by the method of neutralization.

Principle

Retinoscopy is based on the fact that when light is reflected from a mirror into the eye, the direction in which the light will travel across the pupil will depend upon the refractive state of the eye.

Prerequisites for retinoscopy

1.A darkroom, preferably 6-m long, or which can be converted into 6 m by use of a plane mirror.

2.A trial box containing spherical and cylindrical lenses of variable plus and minus powers, a pinhole, an occluder and prisms.

3.A trial frame (Fig. 23.8) preferably of adjustable type which can be used in children as well as adults.

4.Vision box. A Snellen’s self-illuminated vision box (Fig. 23.9).

5.Retinoscope is a simple device to perform the retinoscopy. Broadly, retinoscopes available are of two types:

(a)Mirror retinoscopes are cheap and the most commonly employed. A source of light is required when using mirror retinoscope, which is kept above and behind the head of the patient. A mirror retinoscope may consist of

Fig. 23.9. Snellen’s vision box.

a single plane mirror (Fig. 23.10A) or a combination of plane and concave mirrors (Pristley-Smith mirror– Fig. 23.10B.

A B

Fig. 23.10. Mirror retinoscopes: A, plane mirror; B, Pristley-Smith, mirror.

(b)Self-illuminated retinoscopes are costly but handy. Two types of self-illuminated retinoscope available are: a spot retinoscope and a streak retinoscope (Fig. 23.11). The streak retinoscope is more popular. In it the usual circular beam of light is modified to produce a linear streak of light by using a planocylindrical retinoscopy mirror. The streak retinoscopy is more sensitive than spot retinoscopy in detecting astigmatism.

Plane versus concave mirror retinoscope

Fig. 23.11. Streak retinoscope.

Procedure

The patient is made to sit at a distance of 1 m from the examiner (Fig. 23.12). With the help of a retinoscope, light is thrown onto the patient’s eye, who is instructed to look at a far point (to relax the accommodation). However, when a cycloplegic has been used, the patient can look directly into the light and have the refraction assessed along the actual visual axis. Through a hole in the retinoscope’s mirror, the examiner observes a red reflex in the pupillary area of the patient. Then the retinoscope is moved in horizontal and vertical meridia keeping a watch on the red reflex (which also moves when the retinoscope is moved).

In practice, plane mirror is used for retinoscopy. In patients with hazy media and high degree of ametropia concave mirror is more useful.

Fig. 23.12. Procedure of retinoscopy.