The general method for the eye

There are 30 million blind people in the world. Half of them are blind from cataracts, and a quarter from trachoma. The other major causes of blindness are glaucoma, vitamin A deficiency, corneal infections, and onchocerciasis. In the industrial world two people in a thousand are blind, but in the developing world blindness is ten times more common[md]one or two in every hundred. Cataract can be treated, and glaucoma can be arrested; trachoma and vitamin A deficiency can be prevented. It is unfortunate therefore that ophthalmology scares most doctors, who imagine that the eye must be impossibly difficult. This is not true: you can diagnose 90% of eye diseases with a torch and an ophthalmoscope.

Someone in the district must be able to do cataracts and trabeculectomies. Surgery inside the eye is difficult, so learn these operations by apprenticeship from an expert; they are not described here. They can also be done by a medical assistant.

Here is the basic eye equipment[md]it does not include equipment for operating inside the eye. Look after it with the greatest care.

Fig. 24-1 SOME EYE ANATOMY. A, the flow of aqueous from the ciliary body into the posterior chamber, through the pupil into the anterior chamber, then through the trabecular apparatus into the scleral sinus (canal of Schlemm). B, the ciliary angle. C, the globe.

1, the visual axis. 2, the cornea. 3, the anterior chamber. 4, the iris. 4a, the lens. 5, the ciliary body (the section on the left passes through a ciliary process, on the right it passes between them). 6, the vitreous. 7, the fovea. 8, the macula. 9, the optic disc. 10, the optic nerve. 11, the sclera. 12, the choroid. 13, the retina. 14, the ciliary process. 15, the ciliary muscle. 16, the scleral sinus. CHARTS, visual acuity, (a) Snellen and (b) illiterate E charts, both for use at 6 metres; one chart only of each. These are essential, and can usually be produced locally. They have patterns of ''Es' of different sizes in different positions, and can be used by patients who cannot read.

TEST TYPE, reading pattern, one set only. Optional. Use this for examining older patients with presbyopia who need glasses. If necessary, you can also use a book or newspaper.

TORCH, for focal illumination, local pattern, preferably pencil type, with ''lens bulb', one only. A locally available torch is adequate: it can be easily replaced, as can its bulb and batteries.

LOUPE (magnifying spectacles), binocular, surgical, Bishop Harman headband type, [mu]2[nd][mu]8, one only. Some simple form of magnification is useful for examining the front of the eye, for removing superficial foreign bodies, and for other kinds of fine work, such as suturing nerves.

TONOMETER, Schi[um]otz, one only. You must be able to measure the intraocular pressure (IOP) if you are going to diagnose glaucoma. Digital measurement is simple but unreliable, unless the pressure is very high ([mt]40 mmHg), by which time there may be advanced loss of vision.

OPHTHALMOSCOPE, simple pattern, Keeler type, battery handle, one only. An ophthalmoscope is very useful, but you can do much good eye work without one.

SLIT LAMP MICROSCOPE, on stand, simple pattern, as Inami 911SX or equivalent, one only, optional. You will find a slit lamp useful, although you can diagnose uveitis without one. Read the pamphlet with the instrument, and spend some time with an experienced operator.

NEEDLES, retrobulbar, 7 cm, blunt tip, very fine, one box only. These are the best needles for retrobulbar blocks, but you can use any long thin needle.

SPECULUM, ophthalmic, lid, solid blades, hinged with screw adjustment, one only. You can only insert a lid speculum after a patient has been anaesthetized with drops of a local anaesthetic.

SCISSORS, ophthalmic, lid, blunt points, one only. If necessary, you can use any fine scissors.

FORCEPS (clamp), tarsal cyst (chalazion), 8 mm ring, Lambert pattern, one only. This has two blades, one with a ring and the other with a plate. Use it to hold an eyelid while you incise a tarsal cyst.

CURETTE, chalazion (tarsal cyst), one only.

CAUTERY, simple type, ball pattern, two only. Heat this on a spirit lamp.

CLAMP, eyelid, entropion, Desmarre's or Snellen's, (a) medium and (b) large, one only of each. Use this to hold a patient's eyelid when you operate for entropion.

SCISSORS, ophthalmic, spring pattern, Westcott's or Castroviejo's, two only. These are particularly delicate instruments which need treating with special care.

FORCEPS, fine, toothed, St Martin's, two only.

RETRACTOR, eye, Desmarre's, one only. Use this for examining children.

NEEDLE HOLDER, ophthalmic, curved with lock, Castroviejo pattern, (a) light, (b) heavy, one only of each type. Use the light pair for suturing a corneal laceration, and the heavier pair for lid surgery.

TRIAL LENSES, basic set with trial frame, spherical lenses only, cylindrical lenses not required, one outfit only. These are for prescribing glasses to correct refractive errors, and are a luxury unless spectacles are easily available.

GLASSES, simple frames, second-hand if necessary, spherical lenses [+]1 to [+]3.50[md]the most commonly needed glasses are [+]2 and [+]2.50, several hundred assorted. If you can stock glasses you can deal simply and effectively with the reading difficulties of most patients.

BASIC DRUGS. [f10]Antibiotics. [f09]Topical antibiotic: enriched tetracycline (or chloramphenicol) eye ointment 1%. Subconjunctival antibiotic: Gentamicin injection 40 mg/ml. [f10]Drugs acting on the pupil. [f09]For diagnosis: cyclopentolate 1% or phenylephrine 10%. For treatment: atropine 1% as ointment. Pilocarpine 4% for glaucoma. [f10]Local anaesthetics. [f09]Lignocaine hydrochloride 4% or amethocaine hydrochloride 0.5%. [f10]Steroids. [f09]Hydrocortisone 1% (a weak formulation). [f10]Vitamins. [f09]Vitamin A capsules 200,000 iu. [f10]Diagnostic materials. [f09]Fluorescein papers.

Sandford Smith J, ''Eye Diseases in Hot Climates', John Wright.[-3] Schwab L, ''Primary Eye Care in Developing Nations', Oxford University Press. [-3] Galbraith JEK, ''Basic Eye Surgery, a Manual for Surgeons in Developing Countries'. Churchill Livingstone, 1979.[-3] Parr J. ''Introduction to Ophthalmology', Oxford University Press, (2nd edn 1982). Fig. 24-2 TEST THE PATIENT'S VISUAL ACUITY before you do anything else. Stand him 6 metres from the test chart and ask him to tell you if the ''three legs go up, down, right, or left''. From a TALC slide set.

THE GENERAL METHOD [s7]FOR AN EYE HISTORY Always take the patient's history carefully, it may be critically important. Occasionally it is misleading. He is likely to have: (1) An acute red painful eye(s), which has occurred spontaneously (24.3), or is the result of trauma (Chapter 60). (2) Gradual or sudden impairment of vision in one or both of his eyes (24.5). (3) Gradual difficulty reading, usually in patients over 40 (presbyopia, 24.8). (4) Other less common but often important eye symptoms, such as squints (24.9), protrusion of the eye (proptosis, 24.11), or difficulty opening his eye (ptosis, 24.15) or closing it (lagophthalmos, 30.3).

If he has pain, try to distinguish: (1) The deep pain caused by an abrupt increase in intraocular pressure. (2) Foreign-body pain from irritation of his conjunctiva. (3) Superficial pain in an eyelid. (4) Photophobia, which is eye pain on exposure to light. (5) Minor discomforts which may result from inadequately corrected refractive errors. (6) Headaches.

EXAMINING AN EYE The standard examination of an eye is time-consuming to do well, so train a nurse or medical assistant to test a patient's visual acuity and examine his eyes. At first he will refer many patients to you. Later, he will be able to see 90% of the patients ]]himself. Your consulting room must be at least 6 metres long and you should be able to darken it. You must have a good light. Most examinations can be done while a patient sits in front of you.

MEASURING HIS VISUAL ACUITY. ALWAYS test his visual acuity. Explain to him that you want to test his eyes. Begin by testing them separately (with distance glasses if he wears them); test them again each time you see him; and record your results, so that you will know if his vision is deteriorating or not. If he can read, test each eye separately with Snellen's type.

Stand him 6 metres from the well-lit chart, and close his left eye with a piece of paper or your left hand. Ask him to start at the top and tell you whether the ''three legs go up, down, right, or left'', until he cannot read any more. The top figure is the distance in metres to the test chart, the bottom one is the distance at which a person with normal vision can read that line. The usual sequence of tests getting progressively worse is: 6/6, 6/9, 6/18, 6/60, 3/60. CF 3 m (count fingers at 3 metres) is equivalent to 3/60. If he cannot CF at 1 m, try hand movements (HM), and then test for the perception of light (PL). If you shine a torch into each of the 4 quadrants of his visual field, can he tell you where it is coming from?

Visual acuity can be usefully divided into four groups: (1) Good vision 6/6[nd]6/18; (2) poor vision 6/24[nd]6/60; (3) blind CF 5 m[nd]PL (he can count fingers at 5 metres to perceive light); (4) blind to light NPL (he cannot perceive light). Blindness is ''a loss of vision which results in the patient being unable to continue with his normal life, and to walk unassisted'. It is usually equivalent to binocular vision of [lt]3/60, which is the same as [lt]CF 3 m. Before you decide that he is completely blind, test him with a very strong light. If an eye cannot see any light, and its pupil does not react to light, it is sure to be beyond help, so there is no point in referring him. If his vision is normal and remains normal and his eye is white, referral is rarely necessary.

EXAMINING THE OUTER EYE [s7]WITH A TORCH Start by looking at his face. Note any abnormalities of his lids, lacrimal apparatus, puncta and canaliculi, his lacrimal glands and sacs, and also any epiphora (tearing). If he is in much pain, and his eyelids are in spasm, one drop of a sterile local anaesthetic will make examination easier.

Do his eyelids open and close normally? You can see this best when he blinks. Check his lids for swellings, and check that his lashes are in their normal position.

Are his conjunctivae white? Note particularly the distribution of any redness. If it is maximal near his corneoscleral junction, it is ciliary hyperaemia (this occurs in iritis and corneal ulcer). If it is maximal at the periphery but often extending all over, it is likely to be conjunctivitis. To examine the conjunctiva of his upper lid, evert it as in H to K, Fig. 24-5.

Look for pus or mucopus in his inferior fornix. This is present in all cases of bacterial conjunctivitis, and in some cases of viral conjunctivitis. Look also for signs of vitamin A deficiency: dry-looking conjunctivae, or Bitot's spots (white patches on the temporal side of his conjunctiva).

Are his corneae bright, shining and clear? Surface irregular? (corneal ulcer). Pannus superiorly? (trachoma, 24.13). Haziness? (oedema from trauma, keratitis, or glaucoma).

Is the surface of his cornea normal? Ulcerated? Instil one drop of 2% fluorescein, or dip the end of a fluorescein impregnated filter paper inside his lower lid for a few seconds. Mop out the excess fluorescein with tissue paper. Shine a light on his eye at an angle. Gaps in the corneal epithelium stain green (foreign bodies, ulcers, abrasions).

Is his anterior chamber normal? Note its depth. Is there any blood (hyphaema, 60-7), or pus (hypopyon, Fig. 24-7) on the bottom of his anterior chamber?

Are his pupils black? Do they react to light? Pupils grey or white? (opacities in the lens, cataract). Note their size and shape. Is their outline irregular? (adhesions of his iris to his lens, called synechiae, due to iritis). A pupil which is large and does not react to light in an eye that cannot see? (most likely optic nerve damage, commonly caused by glaucoma).

SPECIAL EXAMINATION METHODS [s7]FOR THE EYE THE PIN-HOLE TEST is a useful way of screening for refractive errors. If he has poor vision, place a card with a 1 mm hole (punched with a pencil) in front of his eye. If he has an uncorrected refractive error, his vision will be improved. If he has a lesion of his retina or optic nerve, it will be worse.

DIGITAL TONOMETRY to measure the intraocular pressure (IOP). Ask him to look down and keep looking down, but not to actively close his eyes. Put the tips of both your index fingers on one of his globes, so as to feel his sclera through his upper lid above the upper border of his tarsal plate. Gently press with alternate finger tips towards the centre of his globe: (1) Gently fluctuate it from one finger to another. (2) Indent it with one finger and estimate the sense of fluctuation imparted to your stationary finger. (3) Estimate the indentation of his sclera as you relax your indenting finger. You can judge his eye to be ''soft' ([lt]10 mmHg), ''normal (10[nd]35 mmHg), or ''hard' ([mt]35 mmHg). This is a crude test, and he must have a significant rise of pressure ([mt]30 mm Hg) before you can detect it.

Fig. 24-3. SCHI[um]OTZ TONOMETRY. The scale is merely an example; use the scale which is supplied with your instrument. Three weights are usually supplied with each instrument.

SCHI[um]OTZ TONOMETRY Clean the instrument with a pipe cleaner and ether. Using the standard 5.5 gram weight and the metal footpad, make sure the instrument is calibrated to zero. Explain what you are going to do, lie him flat and instil a local anaesthetic into his conjunctiva. Ask him to open both his eyes, and look straight up at a target placed on the ceiling.

With the 5.5 g weight in place, put the tonometer plunger gently on the centre of his cornea with his eye open, and read the scale. If in doubt, repeat the reading 3 times. Use the tables provided with the instrument to calculate his IOP from the scale reading.

The normal IOP is 7 to 25 mm Hg. In practice, using the 5.5 g weight, a scale reading of 2 or less ([mt]28 mmHg) indicates a raised IOP. A reading of 3 or above ([lt]25 mmHg) is ''normal'. If his IOP is [mt]40 mmHg, his cornea is likely to become oedematous (the characteristic ''hazy cornea' of glaucoma), and you can see this with a torch. This is usually a late sign of glaucoma.

OPHTHALMOSCOPY to examine the fundus and media of a patient's eye. You must, either, dilate his pupils with a short-acting mydriatic such as cyclopentolate 1%, or examine him in a dark room.

7 (1) Ask him to keep both eyes open and look straight ahead. (2) Start with the ''0' lens in the ophthalmoscope (unless you have a refractive error and are not wearing glasses; if so select the appropriate correcting lens and use this as ''0'). (3) Use your right hand for his right eye and your left hand for his left eye. (4) Hold the sight hole of the ophthalmoscope close to your eye, resting it against your nose and orbit, and move it with you as if it was attached to your head. To find this position, look through the sight hole at some distant object. (5) With your thumb on his forehead gently raise his upper lid clear of his pupil. (6) Start with the ophthalmoscope 20 cm from his eye, and shine the light into his pupil; it should glow uniformly red (the red reflex). (7) Move closer and watch for any opacities in his media silhouetted against his red reflex. If you see a shadow, use the [+] lenses ([+]5 to [+]12) to see it more clearly. (8) Ask him to look straight ahead, and move as close as you can to his eye without touching his eyelashes or cornea. (9) Find and look at his optic disc: it is 15[de] to the nasal side of the optical axis of his eye. (10) Turn the wheel with your forefinger to get the best view of his disc. Examine: (a) The vertical cup/disc ratio (a ratio of [mt][1/2] suggests glaucoma, 24.6). (b) His disc margins; if these are blurred all round (360[de]) it suggests papilloedema (refer him). (c) His blood vessels, looking for haemorrhages and exudates suggestive of diabetic retinopathy. (d) His macula, for black and white pigmentation which may suggest choroiditis involving his macula (maculopathy).

Fig. 24-4 SLIT LAMP MICROSCOPY. A, a narrow pencil of light illuminates the patient's eye from an angle while it is examined with a low-power microscope. B, the layers of his cornea and lens are demonstrated. Particles (not shown) in his aqueous and vitreous reflect light, like dust particles illuminated by a sunbeam in a darkened room. After Parr, John, ''Introduction to Ophthalmology', (2nd edn 1982). OUP, with kind permission.

SLIT LAMP MICROSCOPY. Position his head by placing his forehead and chin on the rest. Vary the angle of the light as convenient. Examine his eye layer by layer: conjunctiva[ar]cornea[ar]anterior chamber[ar]lens.

Conjunctiva: Foreign body? Cornea: Foreign body embedded in his cornea? Ulcer? Note its size and shape after instilling fluorescein and using the blue light. On the back of the cornea look for keratic precipitates (KP, these are clumps of white cells, and indicate uveitis). Anterior chamber: look for cells and flare, pus and blood; estimate its depth. Lens: Posterior synechiae from his iris? Opacities? Vitreous: Particles from a recent posterior uveitis, or bleeding?

MOVEMENTS. Test the movements of both his eyes together, and then test each eye separately, in all directions, including convergence. Note any squint (24.9).

DIAGNOSIS. You have now examined his eyes and should be able to make a provisional diagnosis.

BASIC METHODS [s7]FOR THE EYE BASIC DRUGS. Here is a list:

Antibiotics: Tetracycline or chloramphenicol eye ointment, and eye drops. Ask your pharmacy to make up eye drops in used injection bottles and autoclave them. A little gentamicin for subconjunctival injections will go a long way. Don't use penicillin locally on the eye, either as drops or as subconjunctival injections; it does not keep well and may cause hypersensitivity, especially in light-skinned people. You can get high concentrations of an antibiotic inside his eye by: (1) Injecting it subconjunctivally (see below). (2) Applying it frequently (not less than 4-hourly) as drops into his conjunctiva. If an eye infection is severe, give him systemic antibiotics also. Systemic chloramphenicol will enter his eye.

Drugs acting on the pupil: You will need mydriatics to dilate it. Atropine 1% as ointment or drops will dilate his pupil for a week, so only use this for treating iridocyclitis. Cyclopentolate 1%, or phenylephrine 10%, will dilate it for some hours only, so use these when you want to examine him with an ophthalmoscope.

Steroids may be indicated in iridocyclitis. They quieten the inflammation, reduce photophobia and lachrymation, and make the eye white. Use hydrocortisone or prednisolone as a 1% suspension. The frequency of administration depends on the degree of inflammation; you may have to administer them every 3 hours night and day.

CAUTION ! (1) Steroids can cause viral and fungal corneal ulceration, glaucoma, and cataracts. They are dangerous in the hands of the nonexpert, so prescribe them with the greatest care. (2) Don't use any steroid unless you are certain about the diagnosis, and then use the weakest commonly available one, which is hydrocortisone 1%. (3) Avoid more powerful steroids, such as dexamethasone, because they are more likely to induce glaucoma in a susceptible eye. See also Section 24.5.

Local anaesthetics: Lignocaine hydrochloride 4% or amethocaine hydrochloride 1% (A 5.8).

CAUTION ! The great danger of an anaesthetized eye is that a foreign body may get into it, of which he is unaware, or that he may abrade it, so shield it.

Diagnostic materials: Fluorescein papers are better than fluorescein drops, because you can more easily keep them sterile.

Placebo: If he wants something for his eyes and you need a placebo, give him saline eye drops 0.5%.

EYE DROPS. Pull his lower lid down so that you can see his conjunctiva. Ask him to look up. Put drops or ointment into the outer third of his conjunctiva. Close his eye for two minutes to allow the drug to enter his eye. Don't let the dropper touch his eye, or it may become contaminated. If possible, each patient should have his own drops, because of the danger of cross-infection.

TO MAKE CHLORAMPHENICOL EYE DROPS dissolve two 250 mg capsules in 100 ml of water. Filter the solution into sterile 10 ml dropper bottles. Screw the caps on loosely, and sterilize them in a hot water bath at 100[de]C for 30 minutes, without letting the water splash over the necks of the bottles. Refrigerate them; their shelf-life is 2 months at 2[nd]8[de]C. The shelf-life of commercial drops is only 4 months, so this is a useful method.

SUBCONJUNCTIVAL ANTIBIOTICS are indicated if he has a severe corneal infection or ulceration, especially with hypopyon. You can inject a volume of 0.5 ml (max 1.0 ml) under his conjunctiva. If this contains 0.2 ml of a local anaesthetic, such as 2% lignocaine, the injection will be almost painless. Use a sharp 0.4 mm needle on a 2 ml syringe, as in E, Fig. 24-5.

CAUTION ! Be careful which antibiotics you mix in the same syringe. Don't mix crystalline penicillin and lignocaine. Gentamicin alone is not too painful.

Anaesthetize his eye with a few drops of local anaesthetic solution. Ask him to look up. Pull down his lower lid, with your finger on his cheek. Rest the needle flat on the conjunctival surface of his globe, with the bevel facing away from it. Push the needle under his conjunctiva, parallel to the surface of his globe, rotating it gently as you do so. If it is in the right layer, you will see its point under his conjunctiva. Then inject.

Inject gentamicin 40 mg (the standard antibiotic for this purpose), or chloramphenicol 100 mg, or soframycin 50 mg, or methicillin 100 mg, or ampicillin 100 mg. Make these up in a volume of 1 ml. Don't use penicillin, because of the danger of hypersensitivity. Systemic chloramphenicol enters the eye; so if his eye is severely infected, give him 500 mg 4 times a day for 10 days.

If his infection is getting worse, repeat the injection, daily, for 2 or 3 days (3 is the maximum) until you are quite sure that there is going to be no endophthalmitis. A severely infected eye is is likely to improve, or be lost, in a few hours, so subconjunctival injection is usually only done once, or occasionally twice, on successive days.

WARM SOAKS are an old method, but are an effective one for soothing a painful eye. Ask him to wrap a cloth round a spoon, to dip this into very hot water, and to hold it as close to his eye as he can bear. Soaks are useful for a stye (infected eyelash follicle).

PAD HIS EYE if he has had a minor injury with no suspicion of perforation (60.4). An eye pad, with gentle firm pressure, will reduce his discomfort, and promote healing by preventing his lids moving over the injured area.

Shut his eye, put a pad of gauze over it; place two pieces of adhesive strapping diagonally across the pad, from his forehead to his cheek, to hold the pad in place. Change the pad daily, and look for signs of ulceration or infection.

CAUTION ! The great danger of an eye pad is that it may rub against an anaesthetized eye, and cause an abrasion. So his eye must be shut when you apply the pad. A layer of vaseline gauze on the pad will help to ensure this. Opinions vary as to whether you should ever pad an anaesthetized eye. If you do pad it, there is a risk of the pad pressing against the eye. If you don't pad it, dust may get into it of which he is unaware!

SHIELD HIS EYE: (1) After any severe injury, especially if there is a perforation. (2) After any operation. Shielding it allows it to open and close, without anything extraneous touching his cornea, and perhaps scratching it. A shield is the safest way to protect an anaesthetized eye, and is very helpful for a painful inflamed eye with photophobia.

Put a piece of sterile gauze across his orbit without touching his eye. Hold this in place with a strip of adhesive strapping diagonally across his orbit. Cut an 8 cm diameter circle from cardboard, or an old X-ray film. Cut a radius in this, fold it into a cone, and maintain the cone with a piece of strapping. Hold the cone in place with two pieces of adhesive strapping, or plastic tape from his forehead to his cheek.

CAUTION ! Never occlude the eye of a child under 7 years for several days, because this may cause amblyopia (24.9).

Fig. 24-5 SOME BASIC EYE METHODS. A, an eye pad. B, an eye shield. C, inserting the upper blade of a lid speculum while the patient is looking down. D, inserting the lower blade while he is looking up. E, subconjunctival injection is an effective way of getting a high concentration of an antibiotic inside his eye. F, inserting the first lid suture. G, lid sutures in place; two for the upper lid and one for the lower lid. H, to K, steps in everting the upper lid.