Detailed evaluation: manual of ophthalmological procedure

,DETAILED EVALUATION {. {€ * rl. * {c * * **rF**** * MANUAL OF OPHTHALMOLOGICAL PROCEDURE ho? h .t,I, April 15, 1992 -l- 1. INTRODUCTION The Epidemiological Evaluation Unit, EPI, of the Onchocerciasis Control Programme in West Africa, OCP, is responsible for the evaluation of a) the impact of vector control, b) the effect of chemotherapy or c) the effect of both vector control and chemotherapy on onchocerciasis in the human populations. To carry out this function two levels of evaluations, viz simple and detailed evaluations, are employed. In the original Programme area, some 480 villages were examined at least once at the start of vector control and of these some 80 were surveyed in detail. However only 150 selected villages have been followed up longitudinally every 3-4 years, with some 30 of them in detailed evaluation. Some of the villages serve simultaneously as entomological catching points but the majority of the villages are for epidemiological evaluation only. The activities which are carried out during detailed evaluation are: I ) population census on the basis of family units and the collection of demographic data. 2) parasitological test of skin snip. 3) general clinical examination. (The general clinical examination has been dropped of late because analysis carried out recently on the data collected on the basis of the protocol in use has shown that the resulting data are not useful for demonstrating the evolution of systemic onchocerciasis in the human population) 4) visual acuity test 5) detailed ophthalmological examination These examinations enable the determination of the prevalence and intensity of infection and the prevalence of blindness as well as the distribution of systemic and ocular onchocerciasis in the community. The patient record form in use, 560lM (annex l), is a modification of and a replacement for the original EPI detailed evaluation form 560l . The ophthalmological section of the form 560l M has two parts. The first part records the results of obligatory examinations for signs of ocular onchocerciasis and eye diseases of public health importance and the second part records the results of facultative examination of less important or less interesting eye signs. The new lorm also allows the simplification of the coding of 'the main cause of blindness' into oncho and non-oncho blindness. For detailed evaluation, an ophthalmological team works in conjunction with a parasitological team and 2 census clerks. To conduct a detailed evaluation of villages, all the teams travel together, arrive in the villages together and set up their working stands in such a way as to harmonize the work. The ophthalmological examination is time consuming and its turn-over is at most half that for the parasitological examination. It is therefore often ideal to utilize the time of the parasitological team better by having 2 ophthalmologists working together with one parasitologist. This manual of procedure describes only the ophthalmological activities to be carried out during detailed evaluation. Other activities, viz, census and demographical data collection and parasitological examinations will be described in an appendix. a -L- 2. OBJECTIYE. The principal objective of ophthalmological examination during detailed evaluation is: 2.1. To monitor the impact of vector control or control by chemotherapy or the control by the combination of both forms on ocular onchocerciasis in the human populations. 2.2. As sub-objectives: ophthalmological examination serves: 2.2.1.To describe and document the natural history of ocular onchocerciasis in human populations as a result of transmission control or disease control of onchocerciasis or both. 2.2.2. To map out the geographical distribution of different community patterns of ocular onchocerciasis. 2.3. As a tool for assessing the public health importance of onchocerciasis as a disease in endemic zones. 3. GENERAL DESCRIPTION OF THE OPHTHALMOLOGICAL TEAM 3.1. The ophthalmological team: The ophthalmological team of the EPI Unit is made up of the Ophthalmologist and 6 assistants consisting of 2 ophthalmic trained nurses, 2 registered nurses and 2 auxiliary nurses. A working ophthalmological team however is made up of one ophthalmologist plus 3 assistants with the ophthalmic trained nurse as the team leader in charge of the two assistants. ORGANIZATION OF THE OPHTHALMOLOGICAL TEAM OPHTHALMOLOGIST OPHTHALMIC NURSE OPHTHALMIC NURSE REGISTERED NURSE AUXILIARY NURSE REGISTERED NURSE AUXILIARY NURSE Ar/ -!tl 3.2. Ophthalmological examination and equipment: The ophthalmological examination is conducted in the ophthalmic mobile clinic which has an air-conditioned dark room with 2 compartments, the examination compartment and the patients' waiting compartment. ln the examination compartment, the basic instruments which consist of a slit lamp with applanation tonometer, a direct andrindirect ophthalmoscope and other instruments such as, 3 mirror fundus lens, gonioscope, pachdmeter, fundus camera and accessories for outer eve pho-tpgr?p_[y anO I6It ttrat-ic drops and other matEiiElsTre kept and used. Two chairs *tprA;i,ied illt,elatlent ' ,, and the ophthalmologist and there is a table on which the ophthalmologist can write. There is also ', a file cabinet for filing individual patient record forms. There is a shelf for stocking ophthalmic drops and ointments. A set of spare basic equipment is carried along as back-up equipment during surveys. In the patients' waiting compartment are two benches for seating patients. 3.3. Visual acuity test is done in day-light under a shade, usually of a tree, with Sjiigren's hand test type. t {,,i*u a, r -3- 3.4. Visual field test is done with the Bjerrum screen in day-light under a shade and/or with the Freedman's analyzer in an ophthalmic mobile clinic. 4. DIVISION OF RESPONSIBILITY. 4.1. The ophthalmologist is in charge of: 4.1.1. Planning and executing the survey which consists of the full examination of the village population aged 5 years and above and the recording of the results on special, individual record forms in the ophthalmic mobile clinic. 4.1.2. Taking up contact with government officials on the way to the village 4.1.3. At the village, taking up contact with the village authorities 4.1.4. He is also responsible for filing a report on the results of the survey 4.2. Ophthalmic nurse, team leader: 4.2.1. He is responsible for the assistants in his team 4.2.2.Checks that all equipment, including the back up equipment are in good working condition before the start of the survey. 4.2.3. Makes requisition for materials and drugs for the survey 4.2.4. Oversees the movement of the team when the Ophthalmologist does not travel with the team in a convoy. 4.2.5.In the field, he is responsible for assigning duties to the assistants under him and ensuring the smooth running of the survey. 4.2.6. His principal duty in the field is conductins visual field test of patients as requested by the ophthalmologist. 4.3. The two other assistants: They help the team leader in putting together the materials and equipments for the survey. Their other duties are: 4.3.l.Carrying out visual acuitv test (Sjiigren's hand test) according to laid down instructions and recording the results using laid down codes, see paragraph 8 and annex 2. 4.3.2. assisting the ophthalmologist during his work in the ophthalmic mobile clinic where their duty consists of: 4.3.3. Collecting the forms of patients who have had their visual acuity test done from the visual acuity test stand. These patients would have undergone parasitological examination at the parasitological stand previously, (see appendix). 4.3.4. Calling out the patients in groups of 6 to 8 and seating them in the patients' waiting compartment of the ophthalmic vehicle with their heads bent down between their knees before slit lamp examination commences. 4.3.5. Presenting the patients one after the other for slit lamp examination, after the first patient has bent down his head for at least 2 minutes. He thereby hands over the correctly identified record form allocated to the patient to the ophthalmologist. 4.3.6. Instilling mydriatic drops in the patient's eyes after the slit lamp examination. 44.3.7. Recalling the patients, after 4 groups of 24 - 32 persons have undergone slit lamp examination or after the lapse of about an hour of examination, for fundus examination. 4.3.8. Dispensing eye drops or ointment to patients on the instructions of the ophthalmologist. 5. PREPARATION OF THE SURYEY 5.1. Surveys are conducted in the dry season when the roads are motorable, the farming season is over and the villagers are available and are willing to spare their time for the examination. 5.2. Before the survey, a plan or a timetable is elaborated which takes into account the fact that the ophthalmologist can examine only up to 80 - 100 patients a day. Allowance is also made for travelling from one village to the other. 5.3. A letter signed by the Programme Director is sent to the Minister of Health of the country concerned about 2 months in advance to announce the dates of the planned survey of the villages with an indication of their'sous-prefecture' and'prefecture' or district or province or region, as the case may be. tn the letter, the Minister is kindly asked to inform the local authorities concerned about the pending survey. 5.4. The team leaves Ouagadougou after going through the check list of materials and equipment which are securely stacked in the vehicles to avoid any damage during travel. 5.5. The journey to the village is planned in such a way that the team arrives there in the course of the afternoon. N.B. It is important to study the 'village form' (annex 5) before setting out for the village. The 'village form' contains all the details about the village, including its political set up as well as its access route. A detailed map of the area where the village is situated is to be carried along to aid in finding the route to the village. In the event of the first evaluation of the village, the 'village form' should be filled in accordingly. 6. ARRIVAL AT THE VILLAGE 6.1. First, the chief of the village is sought for the usual salutation, to introduce the team, and to give a brief account of the purpose of the mission. The chief is kindly asked to assemble his elders, political leaders and notables in the village e.g. school teachers, nurses, dressers etc. in the evening for a more detailed briefing. In some villages the political leader is the more influential personality. If that is the case, it is more effective to work through the political leader rather than the village chief. These facts are either noted on the 'village form' or can be enquired discretely. NB. The timing of the assembly in the evening ensures maximum participation. This is the time when all the villagers would have returned home from their farms. In moslem communities, the meeting must be timed to take place after the last prayer of the day. 6.2. Meanwhile the team will search for an appropriate place for the ophthalmic mobile clinic to be parked, preferably under the shade of a tree to avoid direct sunshine on the vehicle and provide shade for the patients waiting for their turn to be examined. 6.3. The Bjerrum screen is hung on the side of the vehicle for visual field test. It is necessary to conduct the test under the pleasant atmosphere of a shade. 6.4. A place, preferably a shade under a tree for conducting visual acuity test is located NB. Ideally the places chosen for the above named tests should be located close to each other and to the parasitological and census stands to avoid the loss of patients when moving from one stand to the next. Boxes used for carrying materials are used as improvised seats for the patients waiting for their turn to be called for the various examinations at the stands. -5- 6.5. At the evening assembly of the chief with his elders, the political leader and the notables of the village, the aim and the procedure of the survey is explained as carefully as possible. It is stressed that only a limited number of people can be examined in a day (about 100 - 120 parasitologically of whom 80 - 100 aged 5 years and over can be examined by the ophthalmologist). It therefore follows that only a certain number of families can be asked to attend the examination each day but everybody will have his turn. NB. The selection of the number of families to be examined is done in consultation with the census clerk if there has been a previous "passage" (see appendix 3). In the event of a first survey, an attempt is made to estimate the sizes of the families to guide in the selection. It is necessary to have about 20 candidates carried over to the next day to ensure that the ophthalmologist can also start work at the same time as the others the next morning. 6.6. At this time the names of the heads of families to be seen on the first day of the survey will be announced and the importance of the attendance by all members of the family together and not singly is stressed. This facilitates the smooth running of the census. The gathering is informed that an eye examination is useful and painless and that people with eye problems other than onchocerciasis will be treated. It is proper to start the survey with the family of the village chief and the chief himself as the first patient. 6.7. The names of the heads of families to be seen the next day will be communicated to the village authorities on the preceding evening with the same instructions, until all families and therefore every body in the village has been examined. 6.8. A point should be made to thank the village authorities on the day of departure NB. A small packet of drugs -nivaquine, aspirin and vitamins- is left with the village chief to be put in the village first-aid box, a useful public relations gesture. 7. Setting up for the Ophthalmological Examination: (reserved for diagram I' -6- 7 .l . On the morning of the first day of the survey (i.e. first actual working day) in the village, the assistants arrange the ophthalmic mobile clinic. They set up the slit lamp and the -{-u_ndus camera, arrange eye drops and ointments in the proper places, test that the generator, the lighting system, as well as the air conditioner work and arrange all other equipment and materials in order for the consultation. 7.2. The ophthalmic team leader then assigns one assistant to the ophthalmic vehicle and the other to the visual acuity stand. Meanwhile census would be proceeding and parasitological examination would have started, (see annex 3 and 4) 8. VISUAL ACUITY TEST The visual acuity test stand is set up under the shade of a tree. The test is conducted by the examiner at a distance of 5 metres from a patient who is sitting dowm on a seat provided. A mark is also made at 3 metres from the patient. The visual acuity test is conducted with 4 single test- types of the Sjtigren's Hand test. They areY=5/4 corresponding to a visual acuity of 6/6 or 1.0; Y=5/5beingthevisualacuityequivalentto6/9or0.7; Y=5/l0equivalentto6/18or0.3andV= 5/30 tantamount to a visual acuity of 6/60 or 0.1. Patients proceed to the visual acuity test stand after having gone through the parasitological examination. 8.1. To start the test, the patient is seated and made to feel at ease. The assistant explains the test directly to the patient or through an interpreter if he does not speak the local dialect. The assistant stands in front of the patient with the big hand test-type of Y =5 /50 and explains to the patient that he or she is to respond to the test by pointing his or her fingers in the direction the fingers on the picture are pointing each time he or she is shown the picture of the hand. The fingers may point upwards, downwards, to the right or to the left in any order. 8.2. After several trials to ensure that the patient has understood the procedure, his or her Ieft eye is covered and the visual acuity of the right eye is tested. Thereafter the right eye is covered and the visual acuity of the left eye is also tested. NB. The essence of the test is for the assistant to present the 4 single Sjtigren's hand test-types in a decreasing order at the 5 metre mark from the patient to him or her. The assistant tests whether the patient is able to recognize correctly the direction in which the fingers of the hand on the test- type being presented are pointing. In the process, the assistant presents each test-type several times, changes the direction the fingers are pointing each time whilst following no particular order and waits for the patient's response before presenting the next change. It is necessary to aim to change the direction the fingers on the test-type are pointing in a random manner to eliminate any guessing by the patient. [t is useful to have other villagers watch the on-going test to give them the chance to learn the procedure at the same time. The patient is considered as having passed the test when he or she recognizes the direction the fingers on the test type are pointing without hesitation on each of the several presentations. The patient will be deemed to have failed the test when he or she is unable to point correctly in the direction the fingers on the test type are pointing on 3 or more occasions of the different presentations of that particular test type. 8.3. Procedure of the test and coding of the results. 8.3.1. The assistant starts the visual acuity test with the first test-type, Y=5/30 ar 5 metre distance from the patient and works him or her through the procedure described above. 8.3.2. If the patient fails the test with test-type Y=5/30, the assistant will repeat the test with the same test type Y=5/30 at the 3 metre mark. 8.3.3. If the patient passes the test with the test-type Y=5/30, the assistant proceeds to repeat the test with the next test type, Y=5/10. -7 - N.B.: The outcome of the visual acuity test with the first test-type Y=5/30 at 5 metre distance determines the way the test should be conducted further. If the patient passes the test it means he or she sees 6/60 or better and the test continues with the smaller test-types in descending order. If the patient fails the test it means he or she sees worse than 6/60 and the procedure is to retain the test-type and repeat the test at the 3 metre distance from the patient. 8.3.4. If the patient passes the test with V=5/30 at 3 metre mark, his or her visual acuity is "counting fingers at 3 metres", code 4, also known as "severe visual impairment". 8.3.5. If the patient failed the test with V=5/30 at the 3 metre mark. He or she would be considered blind, code 5. 8.3.6. If the patient, on passing the test with V=5/30 and being presented with V=5/10 also passes this test, the assistant will repeat the test with the next test-typeY=5/5. 8.3.7. If the patient failed the test with the test-type Y=5/10, it follows that his or her visual acuity, (having passed the test with V=5/30) is 6/60 or 0.1. He is coded 3. This level of visual acuity is described as "visual impairment". 8.3.8. The patient who passed the test with V=5/5, will be presented with the test type Y=5/4 by the assistant. 8.3.9. If the patient failed the test Y=5/5: his or her visual acuity, (having passed the test at Y=5/10) is 6/18 or 0.3 i.e. code 2. 8.3.10. If the patient passed the test withY=5/4, his or her visual acuity would be equal to or better than 6/6 or l/0 i.e. code 0. 8.3.ll.If the patient failed the test with V=5/4; his or her visual acuity, (having passed the test at Y=5/5) is 6/9 or 0.7, i.e. code l. NB. The new detailed evaluation form 560lM does not distinguish between different levels of blindness. The form gives code 6 to a person who has not been examined but is believed not to be blind and code 7 to a person, not examined but believed to be blind, both information being supplied by the relatives or the villagers. A patient who failed to understand the test is coded 8. Code 9 is reserved for the rare case of the patient who has not been examined and about whom no reliable information can be elicited with regard to the visual acuity. OUTCOME -8- TEST OF VISUAL ACUITY AND CODING TEST OUTCOME OUTCOME Fail Pass CODE 5 Fail START Test: Y = 5/30 (at 5m) Pass Test: Y = 5/30 (at 3m) Test: V = 5/10 (at 5m) Pass Test: Y = 5/5 (at 5m) Fail Pass Test: Y = 5/4 (at 5m) Fail 2 Pass I -9- 9. EXAMINATION IN THE OPHTHALMIC YEHICLB 9.1. The ophthalmologist's work begins with the availability of the first l0- I 5 or so patients who have gone through the parasitological stand and have had their visual acuity test done. Before this time the ophthalmologist would have ascertained that all equipment and instruments to be used for the examination are in working condition. He must also have acquainted himself previously with the form 560lM and its record description, annex I and 2 or he must have refreshed his memory in this regard. 9.2. Anterior segment examination 9.2.1 . The assistant assigned to the mobile clinic calls in the first 6-8 patients who get seated with their heads bent down between their knees. The procedure and the purpose of the examination is then explained to the patients by the assistant directly or through an interpreter when he does not speak the local dialect. NB. The bending down of the heads between the knees by the patients causes microfilariae in the anterior chamber of the eye to fall by gravity and to aggregate at the 12 o'clock position, the topmost point of the anterior chamber which has now become the lowest point. On seating the patient at the slit lamp, thereafter, the aggregated microfilariae start falling by gravity again. It is at this point in time that the microfilariae in the anterior chamber of the eye are counted. This procedure ensures standardized microfilarial counts. 9.2.2. After the patients have bent down their heads for at least 2 minutes, the assistant presents the form of the first patient, correctly identified, to the ophthalmologist and seats the patient at the slit lamp. NB. It is important that the assistant checks that the identity of each patient is correct. To identify a patient correctly, the assistant calls out the name of the patient as appears on the individual form. He then proceeds to check that the temporary number the patient is carrying plastered on his right wrist, tallies with that on the individual form. The ophthalmologist, on his part, checks whether the age and sex recorded on the form correspond to the patient. Occasionally, the patient might have lost the number plastered on his wrist. It is then particularly important to ensure that the identification of the patient is correctly established. 9.2.3. Count of microfilariae in the anterior chamber of the eye (MFAC). The ophthalmologist starts the examination by counting the microfilariae present in the anterior chamber, first of the right eye, then the left using the slit lamp magnification x 16. Instruction for coding the count is given by "Record description to form 560lM, annex 2". NB. The search for microfilariae in the anterior chamber is straight forward but the counting becomes more and more inaccurate as the number of microfilariae exceeds 30. Also when only a few microfilariae are present in the anterior chamber, say I - 3, they may occasionally be difficult to find and the anterior chamber may need to be scanned carefully. A single microfilaria may lie hidden in the angle of the anterior chamber and may appear after perhaps a minute or two when scanning of the right anterior chamber may have been over and the left is being scanned. If I or 2 microfilariae are found in the left anterior chamber when none had been found previously in the right, another look at the right anterior chamber may be indicated to ensure that there is really no microfilaria in the anterior chamber of the right eye. 9.2.4. Count of dead microfilariae in the cornea, (DMFC). Dead microfilariae in the cornea can be seen with the x l6 count is made first in the right then in the left cornea. magnification of the slit lamp. The NB. Dead microfilariae are usually found at 3 and 9 o'clock positions of the corneal periphery but may be fairly evenly distributed in the cornea when they are many. They are usually found in the anterior l/3 of the cornea. Counting of dead corneal microfilariae is an accurate procedure vi ll -10- when the patient is co-operative. When the microfilariae are many, the count may be facilitated by dividing the cornea into sectors and counting the microfilariae in a sector at a time. The coding of the result is similar to that of MFAC, see annex 2. 9.2.5. Count of Oncho Punctate Opacity: The counting of oncho punctate opacities of the cornea is done with x l6 magnification of the slit lamp. NB. Corneal punctate opacities or fluffy opacities are about 0.5 mm in diameter and lie in the anterior layer of the cornea and the names describe their appearance. They are also known as snow flake or cotton wool opacities. They may or may not contain dead microfilariae,.either in part or- as-.a whole in their middle. (When dead microfilariae are present in onctro.coinEat' opacities, the mibiofilaiiae are counted and added to the count of the dead microfilariae made previously). Oncho punctate opacities are often found at the nasal or temporal periphery but may be anywhere in the cornea. Coding of the results is found in the "Record description of form 560lM', annex 2. 9.2.6. Sclerosing keratitis (SK) The search for sclerosing keratitis is done with x l6 magnification of the slit lamp. The coding follows the instructions in the "Record description of form 560lM" NB. Sclerosing keratitis is a diffuse opacification of the cornea resulting from the invasion of numerous microfilariae therein. It may be mild and be located in the nasal, temporal or inferior periphery of the cornea only. It is grade I when it is found in only one or two of the above locations. Sclerosing keratitis may present as an inferior confluent semi-lunar opacity of the cornea, when it is grade II, and may, on occasion, extend to cover the pupil area of the cornea, grade III. The diagnosis of the typical onchocercal sclerosing keratitis is straightforward. However, often, its differentiation from other non-onchocercal corneal lesions may not be easy, in particular, when microfilariae are not found in the cornea. Furthermore, in the course of the regression of the lesion during control, sclerosing keratitis may undergo changes in form and appearance. This atypical sclerosing keratitis, which are unassociated with corneal microfilariae, may also pose a problem in the diagnosis. This anomaly is well described in the "Record description of form 560lM". annex 2. The additional codes 4, 5, 6 are provisional. They are designed to determine the validity of the association of the lesions with oncho sclerosing keratitis. 9.2.7. Other corneal signs: After the search for the typical onchocercal signs, a search for any other corneal pathology is made and the results recorded using the applicable code. See under other cornealsigns in "Record description of form 560lM", annex 2. 9.2.8. Iridocyclitis. Next, the signs of iridocyclitis, viz, flare, cells, KP's. circumcorneal injection, iris changes and finally pupil reaction to light are lo6ked for and the results coded according to the "Record description of form 560lM', annex 2. 9.2.9. Conjunctiva/lid signs: A search is made for signs of conjunctival and lid pathology and coded as applicable according to the "Record description of form 560lM", annex 2. 9.3.1. The assistant now instills mydriatic in the eyes of the patient and helps him or her out of the mobile clinic. He then seats the next patient for examination of the slit lamp after correcrly identifying him or her and handing over his or her record form to the ophthalmologist. - ll - 9.3.2. Meanwhile the ophthalmologist records his findings by filling the appropriate codes on form 560lM, annex l, belonging to the patient just examined. NB. After about one hour or the slit lamp examination of some 20 - 30 patients, the first patients will be ready (with their pupils dilated) for posterior segment examination. 9.4. Posterior segment examination 9.4.1. The assistantcalls the first 6-8 patients again. This time the patients sit down normally. 9.4.2. The first patient is seated at the slit lamp and his form, checked to be correct, is handed over to the ophthalmologist. 9.4.3. Lens f cataract: The ophthalmologist examines first the lens with the slit lamp to look for the presence of lens opacities or lens luxation and codes the results according to "Record description of form 560lM, annex 2". NB. Occasionally, dead microfilariae are found attached to the posterior lens capsule 9.4.4. Optic disc: The examination of the optic disc is done with the direct ophthalmoscope to look for changes such as pallor of the disc, changes at the disc margins, sheathing of central retinal blood vessels, signs of papillitis and cupping of the disc. These are coded according to the "Record description of form 560lM", annex 2. 9.4.5. Oncho Choroido-retinitis: The ophthalmologist looks for the presence and the distribution of the typical oncho signs of the choroid-retina, viz. atrophy of the retinal pigment epithelium, atrophy of choriocapillaries, grey discs and subretinal fibrosis. The search is made with the direct and if necessary the indirect ophthalmoscope and the results are coded according to the "Record description of form 560lM", annex 2. 9.4.6. Other choroido-retinal signs, of possible oncho origin The non-typical oncho choroido-retinal signs viz. pigment hyperplasia, ps@!.gg_and pseudo-grey discs are coded according to "Record description of form 560lM", annex 2. NB. This portion of the record of the results of the ophthalmological examination is designed to test the probable association o udo-drusen, pigment hyperplasia and pseudo-grey disc with oncho and should be viewed as provls 9.4.7. Other fundus signs: During the ophthalmoscopy, other fundus signs resulting from retinal or choroidal pathology are looked for and coded according to "Record description of form 560lM", annex 2. 9.5. Visual fields: All patients with onchocercal lesions of the fundus affecting the optic nerve or choroid-retina, will require visual field test and the ophthalmologist must request it. The test is carried out by the ophthalmic nurse who has been trained especially to conduct it, using the Bjerrum screen and also the Freedman's analyzer if possible as a check for accuracy. -12- 9.6. Facultative examination: These examinations are done for special studies only. 9.6.1. Count of living microfilariae in the cornea, (LMFC) The counting of living microfilariae in the cornea is conducted with x 25 magnification of the slit lamp. Coding of the results is similar to that of DMFC and MFAC, see annex 2. NB. Living microfilariae lie usually coiled over themselves in the anterior cornea. Similar to dead microfilariae, they are located at 3 or 9 o'clock position of the corneal periphery when they are only a few. When many, they are fairly evenly distributed in the cornea. On continued observation, they may be found to uncoil and recoil themselves. They are transparent and are usually difficult to see by the untrained observer. Retro-illumination technique facilitates the viewing of living microfilariae in the cornea. If this facultative examination is envisaged it is recommended to carry it out after the count of dead microfilariae, see (9.2.4). 9.6.2. Measuring of Intra-ocular pressure, (IOP): Intra-ocular pressure should be measured when there are signs of glaucoma or the existence of glaucoma is suspected. NB. Intra-ocular pressure is generally not measured as a routine. The IOP is entered as exact value on form 560lM. 9.6.3. Gonioscopy: When done the result is coded according to the "Record description of form 560lM". annex 2 9.6.4. Fluorescein angiography: This is done only in special studies and can be coded if necessary according to the "Record description of form 560lM", annex 2. 9.6.5. Eye photography: Photos may be made of oncho lesions of the anterior segment of the eye or the posterior segment by fundus photography. The coding of eye photography is given by the "Record description of form 560lM", annex 2. NB. These photos are useful for documentation and recording of changes that have occurred during follow-up surveys. 9.6.6. Observation: The space "observation" on form 560lM is provided for recording any extra information that has no provision for coding and should be used freely. 9.7. Main cause of visual impairment: This gives a summary diagnosis of the eye examination and is coded according to the "Record description of form 560lM", annex 2. NB. After filling in the form 560lM, the ophthalmologist must check to ensure that all spaces on the form are correctly filled and that there are no apparent discrepancies. - 13 - 10. DATA ORGANIZATION 10.1. At the end of the survey in the village the assistants set out to organize the data collected by age and sex in a summary table on a special form provided, annex 6. 10.2. The ophthalmologist can therefore prepare a preliminary analysis of the results of the survey of the village. NB. The preliminary analysis of the results of the survey enables the ophthalmologist to brief the local authorities on the level of or the changes in the severity of ocular onchocerciasis in the village and therefore in the area as a whole, when he pays them the usual courtesy visit at the end of the survey. The data processing leading to the definitive analysis of the results of the village surveys are done with the computer by the unit of Bio-statistics and Information System in Ouagadougou. 11. DATA ENTRY AND PROCESSING ll.l. Back in Ouagadougou the census clerk checks that all the individual forms have been correctly filled. Any mistakes or omissions found on the individual forms are then rectified after checking with the responsible ophthalmologist. The forms, so reviewed, are handed over to the Biostatistics and Information System unit. 11.2. The entry of the data in the computer is done by two members of the EPI unit who have been trained especially for this purpose. I I .3. The processing of the data is done by the Programme Analyst using standard programmes Both the data collected and the results of the analysis are stored in Bernoulli boxes. NB. Usually the results of the analysis are ready in some 2-4 weeks after return from the survey