conjunctival discharge. Patients often describe discomfort, burning or foreign body sensation as “pain”. Sometimes they mention a lot of complaints and the doctor has to find out which of them disturbs the patient the most and which of the subjective symptoms describes the complaints best. In other cases, the patient does not readily give specific information on what he/she really feels but just reports “I have an eye problem” or “I turn to you because of my eyes”.
Diagnostic clues, characteristic complaints of the patient, that may help the differential
diagnosis among the most common causes of red eyes are:
If the eye itches, it is usually allergy.
If the eye burns, it can be dry eye.
If the eye is sticky, it is probably bacterial conjunctivitis.
Many more questions and answers, as well as specific symptoms are discussed in detail in the following chapters of this booklet, dealing with dry eyes and allergic and infectious types of conjunctivitis.
EXAMINATION OF THE PATIENTS
Examination of a patient with a red eye performed by a GP differs from the examination performed by an oph- thalmologist in several respects. The GP does not have the instruments with which an eye specialist usually exa- mines the patient (such as a slit lamp, ophthalmoscope,
Figure 2 – Examination with side illumina- tion and a magnifying glass
tonometer, perimeter etc.). The GP has to examine the eyeballs, the eyelids and the surrounding areas with the naked eye. The inspection can be assisted with good side illumination (a flashlight, a visit lamp or a table lamp). For better visualization the doctor can use a loupe (mag- nifying glass) and if he/she is presbyopic (or is wearing glasses) must wear his/her glasses when performing the examination (Figure 2). The other major difference is that
the GP does not have to diagnose all specific eye diseases. It is sufficient to decide whether the patient has some type of conjunctivitis (conjunctivitis sicca, allergica or infectiosa), that can be treated by a non-specialist with appropriate eye drops and ointments, or if the patient is (or may be) suffering from other possible causes of red eyes (different types of keratitis, iri-
tis, iridocyclitis, scleritis, eye injuries, glaucoma etc.) that should be treated by an eye specia- list. In any doubtful case, it is always better to be on the safe side and to refer the patient to an ophthalmologist rather than to treat “according to the most probable diagnosis”.
In case of more severe (non-conjunctivitis) type of red eyes, it is also important to decide when, how and where to send the patient (in the lying position in an ambulance immediately to the nearest hospital, by car within a few hours to an institute with an ophthalmological depart-
ment, next day or with an early appointment to the local eye specialist). Eye injuries and glau- comatous attack may fall into the first category; different types of keratitis, iritis and iridocy- clitis into the second; various forms of blepharitis, scleritis, chronic and therapy resistant cases of non-infectious conjunctivitis or keratoconjunctivitis into the third.
THE DIFFERENTIAL DIAGNOSIS OF THE RED EYE
After taking a proper medical history (good anamnesis is half diagnosis!), the first and the most important task is to find out if the patient's visual acuity is disturbed (decreased by the red eye) or not. In some countries, GPs renew driving licenses, waterman ship certificates, fire-
arms licenses and disability pensions (evaluate the impact of possible changes in health suit- ability). To perform this function, they are trained and have the necessary facilities to evalua- te the patient’s visual acuity (i.e. have a vision chart on the wall of their examination room, but do not have a trial frame and a set of lenses for correction of refractive errors). Those GPs who cannot check the patient’s visual acuity using a vision chart can perform distance and near visual acuity tests using posters, tables on the wall and printed text like newspapers with let- ters of different sizes, to find out if the patient is able to read what healthy people can under the same circumstances. Common sense is needed when performing visual acuity testing. Examine both eyes of the patient separately (cover the other eye during the examination). Make sure that the patient keeps his /her eye open and is looking in the right direction. The visual acuity of a patient who normally uses glasses or contact lenses has to be tested with their glasses or contact lenses. If the patient is older than 40 years of age, he/she is presbyo-
pic, i.e. he/she can only read with proper reading glasses. Take into consideration that pres- byopic patients may have different glasses for distance vision (5 m, 20 feet and more) and for reading (33 cm). Patients suffering from conjunctivitis should not have visual disturbance (unless their eyes are full of exudates, or their eyelids are stuck to one another by exudates).
Decreased vision in a red eye should always be considered as a sign of a more severe form of inflammation! These patients have to be referred to an eye specialist, and not treated by the GP!
The second task is to evaluate the smoothness of the sur- face and the clearness (the transparency) of the cornea. The surface of the cornea is normally smooth because it is covered by continuous epithelium and an even, suffici- ently thick and stable precorneal tear film. The smooth- ness of the corneal surface can be judged by examining (evaluating) the light reflex(es) (the reflections of light sources) that can be seen on the surface of the cornea. If the form of these reflexes is regular, if they have sharp margins, if they remain regular when the eye is moving, the surface is smooth (Figure 3). If the light reflexes are irregular, broken or are totally missing, or lose their regu- larity when the eye is moving then the surface is not regular. Irregularity of the corneal surface is a sign of cor- neal involvement, either keratitis or traumatic lesion of the cornea (Figure 4). The transparency of the cornea can be evaluated by judging how clearly the pupillary margin and the texture of the iris can be seen through different parts of the cornea. Usually the details (the colour, the cryptas and the lacunas, parts that are lighter and darker) can be seen and distinguished on the iris, and the mar- gin, the shape, the size and the regularity of the pupil can easily be evaluated (Figure 3). If this is not the case and the above mentioned details cannot be clearly seen, and their sharpness is not the same when the eye moves,
Figure 3 – Bacterial conjunctivitis (clear cornea, purulent exudate)
Figure 4 – Keratoconjunctivitis (broken corneal light reflex, partly cloudy cornea)
THE DIFFERENTIAL DIAGNOSIS OF THE RED EYE