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Post-traumatic dehiscence is a rare condition often compromising the visual outcome of transplanted patients. It can occur after transfixing keratoplasty even after low-energy trauma. We here report two cases of patients with a history of keratoplasty, admitted to the hospital with painful red eye due to trauma. Patients' assessment objected decrease in visual acuity, subtotal graft displacement and major ocular hypotonia. After symptomatic medical treatment, they underwent surgical repair after 16 hours and 72 hours respectively. Visual prognosis was better in patient 2, who reported proper visual acuity. In patient 1 visual acuity didn't improve due to the severity of graft damage and the associated retinal detachment. The purpose of this study was to highlight the poor outcome of patients with ocular trauma after corneal graft. Prognosis was determined by survival, feasibility of grafting and the presence of associated lesions. Education, information and communication campaigns to raise awareness of this condition, especially among young patients, is the best way of preventing it., Competing Interests: Les auteurs ne déclarent aucun conflit d’intérêts., (Copyright: Joseph Matar Mass Ndiaye et al.)

Purpose: To study the topography of retinal breaks and their agreement with Lincoff's rules., Materials and Methods: We performed a retrospective descriptive study of patients with recent rhegmatogenous retinal detachments followed on the ophthalmology service of Abass Ndao Hospital from January 2006 through December 2016. Patients with no prior retinal treatment were included., Results: Over 11 years, we reviewed 97 patients with 107 eyes with retinal detachments. The mean age of our patients was 51.7 years, range 23-79 years. There were 69 male patients, for a male:female ratio of 2.46. Refraction revealed that 38.1% of patients were myopes. Fourteen percent (14%) of patients had experienced trauma to the eye with the detachment. The right eye was involved in 54.6% of patients. The onset was insidious in 54.6% of cases and sudden in 23.7% of cases. All patients had decreased visual acuity, associated with a scotoma in 26.8% of cases. Visual acuity was decreased to light perception through 7/10. In 64.9% of cases, Lincoff's rules were observed., Discussion: Lincoff's rules are still relevant for localization of the breaks in retinal detachments., Conclusion: Diagnosis of a retinal detachment is an essential step, since it determines the treatment. Lincoff's rules still have a role in finding the retinal break in retinal detachments., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Introduction: Retinoblastoma is a malignant tumor of neuroepithelial origin, developed from young retinal cells, occurring in infants and young children. The goal of the study was to assess the role of CT in the diagnosis of retinoblastoma at the Aristide le Dantec Hospital in Dakar., Patients and Methods: This is an 11-year retrospective study of 160 patient records in the ophthalmology department and pediatric oncology unit of the same hospital., Results: One hundred and sixty (160) patients were recruited. The male:female ratio was 1.05. The mean age was 32.19 months. Leukocoria was the most common clinical sign, occurring in 105 cases (65.62 %). The retinoblastoma was intraocular in 97 cases (60.62 %). We saw 122 (76.25 %) unilateral and 3 (1.87 %) trilateral presentations. CT was performed in 150 children with 110 cases (73.33 %) of calcifications ; 62 cases (41.33 %) of optic nerve invasion ; 24 cases (16 %) of extraocular muscle invasion and 18 cases (12 %) endocranial extension. Associated tumors were found on CT: 2 cases of suprasellar mass and 1 case of pineoblastoma. In patients whose specimens were analyzed, histology showed 48.15 % optic nerve invasion, consistent with the CT findings., Discussion: CT has an important role in the diagnosis of retinoblastoma, despite its recent contraindication in bilateral and unilateral multinodular forms., Conclusion: CT is a good alternative to MRI in the diagnosis of retinoblastoma in developing countries with limited technological resources., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Introduction: Ametropia is common in children and cause strabismus and amblyopia. The goal was to establish its prevalence in a hospital setting among Senegalese children., Patients and Methods: This was a retrospective study of patients under 15 years of age with clear ocular media. The marital status, circumstances of discovery, and results of cycloplegic refraction were recorded., Results: Of 1506 children, 175 demonstrated ametropia. The mean age was 8 years, and the male : female ratio was 0.68. Family history of ametropia was present in 8.5 %. Decreased VA was present in 39.66 %, headache 10.06 %, and strabismus 4.47 %. Automated refraction in 109 patients and skiascopy in one patient showed 58.18 % cases of myopia, 18.18 % of hyperopia and 36.57 % of astigmatism., Discussion: The most common ametropia was myopia. Patients were referred for symptomatic ametropia., Conclusion: Screening for ametropia might occur earlier if it is associated with pediatric monitoring in our regions., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Introduction: Our goal was to evaluate the normal macular thickness in Blacks by OCT and to determine socio-demographic and clinical parameters which may influence it., Materials and Methods: This was a multicenter, prospective, descriptive study over 6 months. It included Black adults followed in the ophthalmology departments of Abass Ndao and Aristide-Le-Dantec hospitals in Dakar. Included subjects had corrected visual acuity of 10/10 (0 logMAR) and P2 (+0.1 logMAR), clear ocular media, and no retinal abnormalities. We used the Topcon 3D 2000 OCT to measure the central thicknesses of the cornea (CT) and of the macula (MT), and cup to disc ratio (C/D) in each eye. Socio-demographic, clinical and tomographic data were collected on a survey form and correlated to the MT. The analysis was carried out by the Epi info 7 software. We used the Chi 2 comparison test with a P value˂0.05., Results: One hundred and nine patients were included. The mean age was 27.39 years with a male/female ratio of 0.65. The subjects were emmetropic in 54.13% of cases. The mean CT was 519.97μm, the mean C/D was 0.23, and the mean MT was 264.35μm. The P-value (P) was greater than or equal to 0.1 for all the factors studied., Conclusion: MT in our study was lower than that of Whites, and the various parameters studied did not demonstrate a statistically significant influence on MT., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Purpose: To appreciate the epidemiological characteristics and to show the therapeutic aspects of the giant retinal tears., Patients and Methods: We conducted a retrospective study from January 2014 to June 2017 on subjects with giant retinal tears. Patients with media opacities limiting examination were excluded., Results: We identified 17 cases of giant retinal tears. The frequency of detachments related to a giant retinal tear was 17% compared to all retinal tears. The mean age was 50.75 years with a sex ratio (M/F) of 6.5. We found three cases of high myopia, one case of hyperopia and four trauma cases. All patients had a decrease in visual acuity. The average time to consultation was four weeks. The mean intraocular pressure was 8mmHg. The tear was found in the left eye in eight cases and in the right eye in five cases; two cases were bilateral. We performed intraocular surgery in five eyes and laser in four eyes. We achieved anatomical reattachment and functional improvement in all operated patients., Comments and Conclusion: The prognosis of a giant retinal tear remains guarded, especially if patients are seen and treated late. Laser photocoagulation of giant tears remains effective, especially in cases of early diagnosis., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Introduction: In Senegal, 10% of the population are said to be carriers of hemoglobin S, the most widespread hemoglobinopathy in the world. It is responsible for potentially blinding ophthalmological manifestations. Few practitioners refer patients for ophthalmologic screening. The goal of our study was to assess the level of knowledge of practitioners of the blinding ocular lesions of sickle cell disease., Materials and Methods: A cross-sectional prospective study was carried out over five months. It included Dakar university hospital practitioners aside from ophthalmologists. On the survey form, each practitioner specified his or her specialty and responded to eight questions regarding sickle cell patients seen in consultation, knowledge of the blinding lesions related to the disease, and ocular monitoring for blinding systemic diseases. The practitioners were divided into three groups: department of medicine and medical specialties (group I), surgery and surgical specialties (group II), and biology and functional testing (group III). The descriptive analysis was done with the EPI-INFO software version 6.04., Results: The participation rate was 45.88%. Group I represented 45.29% of the sample, Group II 35.85% and Group III 18.86%. In all, 87.73% of practitioners saw sickle cell patients in consultation, 75.47% were aware of ocular involvement related to sickle cell disease, and 58.49% were aware of blinding lesions. 94.62% of practitioners saw sickle cell disease patients without systematically recommending ophthalmological consultation., Conclusion: Practitioners' level of knowledge of the blinding ocular lesions of sickle cell disease is considered to be low., (Copyright © 2018. Published by Elsevier Masson SAS.)

Purpose: The purpose was to record the causes of leukocoria among children under 10years of age and to determine the proportion of rare causes of leukocoria., Patients and Methods: This retrospective study was conducted over a period of ten years, from January 1, 2004 to December 31, 2013, in patients under 10years of age who were referred for leukocoria., Results: Leukocoria represented one of the ten reasons for consultation among children under 10years of age. The mean age of our patients was 42.5months. In 76 % of cases, the leukocoria patients were children under 6years of age. Male patients were affected more commonly, with a sex-ratio of 1.5. Patients coming from Dakar and its suburbs represented two thirds of the total. Bilateral involvement represented 53.7 % of the total. Cataracts were responsible for 74.3 % of cases, retinoblastoma 20.58 %, retinal detachment 0.96 %, retinopathy of prematurity 0.96 %, pupillary membrane persistence 0.96 %, persistent hyperplastic primary vitreous 0.64 %, endophthalmitis 0.64 %, optic nerve coloboma 0.32 %, iris heterochromia 0.32 % and ametropia 0.32 %., Discussion: The total percentage of rare causes was 5.12 % in our study, including one case of hyperopia. These etiologies, although rare, do exist., Conclusion: Rare causes of leukocoria require special attention. The discovery of leukocoria necessitates rigorous etiological work-up. Ametropia must be a diagnosis of exclusion., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Introduction: Our goal is to assess the Quality of Life (QL) of our patients after cataract surgery., Materials and Methods: We performed a multicenter prospective study from July 2012 to December 2013 including patients undergoing cataract surgery, aged 18 and older. A survey sheet with sociodemographic data, clinical data and QL survey (VF-14) was given to each patient after surgery at day 7 (D7), one month (M1) and two months (M2) postoperatively. The final score was obtained by the following formula: QL=V (%)=(F __/__ C)×25. The data analysis was performed using SPSS software., Results: A total of 100 patients were included, 56 men, and 61 years was the mean age. The mean QL score was 29.86% at D7, 73.97% at M1 and 81.21% at M2. Subjects between 18 and 30 years of age had a score of 90.15% vs. 82.52% at M2 for older patients. After optical correction, the quality of life scores increased from 83.22% at D7 to 93.18% at M2. Patients who did not have functional signs had a QL score of 83.94%. Anxious patients had a QL score of 44% at D7, 61.23% at M1 and 52.67% at M2., Conclusion: Good surgical outcomes require, in addition to clinical success, good quality of life. Several factors may influence this quality of life., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Purpose: To report the clinical investigation of isolated microspherophakia involving a Senegalese family in order to appreciate its functional impact., Observations: This is a rural family comprised of 7 members. The sibship included three girls and two boys. One of the girls, who lived in a distant zone, was unable to be examined. Of all the examined members of the family, only the father was unaffected by the illness. There was no consanguinity. The general medical examination was normal. The best-corrected visual acuity (VA) for the girls was 2/10. For one of the boys, BCVA was 8/10 for both eyes, and for the other, BCVA was 10/10 for the right eye and 8/10 for the left eye. The mother's VA was 10/10 and P2 without correction. Myopia and astigmatism were present in the 4 children of the sibship. During the examination, we noted the presence of small crystalline lenses, which were very round and presented an abnormal visibility of the lens equator and zonular fibers. The diagnosis of microspherophakia was confirmed by measurement of the lens diameters by ultrasound biomicroscopy. Complications were present in the girls, including pupillary block glaucoma and amblyopia for the elder, and retinal degeneration and amblyopia for the younger daughter. The elder daughter was managed medically with glaucoma drops. The younger daughter received optical correction and a prophylactic Argon LASER treatment. The two boys received optical correction. No treatment was recommended for the mother., Conclusion: Microspherophakia is a rare condition. Some serious complications can lead to amblyopia. A better multidisciplinary evaluation would allow for early detection and a better prognosis., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Purpose: To evaluate the type and frequency of the ocular lesions found in patients practicing artificial depigmentation., Patients and Method: We conducted a prospective study over 3 months involving 108 patients, of whom 72 underwent depigmentation, and 36 did not, representing the controls., Results: Among patients undergoing depigmentation, 100% were female, of whom 34.72% developed ocular lesions. Exogenous ochronosis lesions of the eyelid predominated (34.72%), followed by ocular ochronosis (25.81%). Cataract (19.35%) and glaucoma (6.45%) were the least frequent. Among the untreated, only 19.44% had ocular lesions. These included cataract (57.14%) and glaucoma (42.86%). Ocular lesions were more frequent in patients using products containing hydroquinone., Conclusion: Artificial depigmentation is responsible for ocular lesions of variable severity. Our study highlights the importance of the raising awareness amongst the general population of the complications of artificial depigmentation, particularly the ocular lesions., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)

Introduction: Cycloplegia allows for an objective refraction in children. Atropine is the gold standard but causes prolonged blurred vision. Cyclopentolate is less effective but less disabling. Tropicamide is a weak cycloplegic. The purpose of this study was to evaluate a cyclopentolate and tropicamide combination (CTA) versus atropine for refraction in black children., Materials and Methods: We performed a prospective study between October 2011 and July 2012 on all children seen in consultation. Objective refraction was performed after cycloplegia with cyclopentolate 0.5% combined with tropicamide 0.5%, and then after cycloplegia with atropine., Results: Thirty-three patients were recruited, 14 boys and 19 girls. The average age was 9.9 years. The mean age of the patients was 9.9 years. Astigmatism was found in 96.9% of cases. It was 1.34±1.32 diopters with CTA and 1.35±1.22 diopters with atropine. The mean axis was 98.15 and 99.8, respectively. Hyperopia and myopia were found in 39 and 27 eyes, respectively with ACT (average 1.73 and 5.37 diopters), and in 41 and 19 eyes with atropine (average 2.06 and 6.11 diopters)., Discussion: There is a good correlation of results with regards to cylindrical and spherical refractive error between the two protocols. Atropine is the best cycloplegic, however ACT provides reliable results., Conclusion: The cyclopentolate-tropicamide combination is satisfactory for routine cycloplegia in children., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Purpose: To measure the central corneal thickness (CCT) in Senegalese melanoderms with primary open angle glaucoma (POAG) and to determine its effect on visual impairment, intraocular pressure, optic nerve and perimetric damage., Patients and Methods: We studied retrospectively the records of patients followed for POAG between May and July 2012. We recorded CCT measured by ultrasonic pachymetry and results of the first clinical examinations, including best-corrected visual acuity (CVA), intraocular pressure (IOP) by Goldmann tonometry, cup-to-disc ratio (C/D), and visual fields by automated perimetry according to the classification of Hodapp., Results: Two hundred and thirty-four eyes of 117 patients were enrolled. Mean age was 56.53 ± 11.29 years and gender ratio was 2.77. Mean CCT was 525.40 ± 39.63 μm for all eyes, right and left (P=0.734). Women had a mean CCT of 521.20 ± 36.20 μm and men 526.91 ± 40.79 μm (P=0.332). Corneas were thinner in patients over 50 years (P=0.0047), in eyes having a CVA<3/10 (P=0.01) or a C/D ≥ 0.8 (P=0.043). CCT had no correlation with frequency of ocular hypertension (P=0.16) or advanced visual field defect (P=0.33)., Conclusion: CCT of glaucomatous Senegalese is independent of laterality and sex, but decreased with age. A thin cornea is a risk for visual loss and optic cup enlargement, thus the importance of systematic measurement of CCT., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Aim: To describe the and the factors that influence their occurrence., Material and Methods: A prospective study was performed over a year in the Ophthalmology clinic of Aristide le DANTEC Hospital, including 112 eyes of chronic renal failure patients followed up in the internal medicine unit of the same hospital. For each patient data of his follow up in the nephrology ward were recorded, even as the ophthalmological clinical examination which included colour test and angiography. All the lesions found were recorded on a questionnaire, seeking for any influence as far as age, sex, duration of signs, dialysis, and general complications were concerned. The analysis was performed using the 2005 Epi-info 6.0 software., Results: Sex ratio was 1.54. 70% were above 40 years old. Blindness was found on 44.6% of the eyes. There were 20.5% cases of eye lids oedema, 15.8% conjunctival calcifications, 26.8% cataracts, 3 cases of ocular hypertension, 7.1% corneal lesions. Hypertensive retinopathy was found on 75.9% of the cases, amongst 14.3% classified stage 3, and retinal oedema signs associated on 13.8%, arteriosclerosis on 14.3% of the cases. 88.1% had confirmed signs of dyschromatopsia. On angiography, there was evidence of chorioretinal lesions due to high blood pressure, including decrease of the choroidal blood flow, choroidal ischemic areas, and halo peripapillary oedema. Age was a risk factor for eye lid oedema. Corneal and conjunctival lesions, even as eye lid oedema and hypertensive retinopathy were more frequent on patients, sick for less than a year. High blood pressure was a risk factor for papillary lesions, hypertensive retinopathy, and dyschromatopsia. Corneal and conjunctival calcifications were found mostly on patients on dialysis, whereas they had less eye lid oedema, hypertensive retinopathy, and maculopathy., Conclusion: Retinal lesion, especially due to high blood pressure is the most described. It permits to establish the prognostic of the disease. Patients on dialysis show a decrease of that retinopathy, but some sequels might persist which are invalidating, irreversible and may lead to blindness. This can be prevented by early screening of high blood pressure and an adequate treatment of chronic renal failure. Ophthalmologic examination remains a cheap and simple method to prevent the complications.

Purpose: Present a Senegalese experience of local anesthesia in children's ocular surgery., Patients and Methods: We conducted a retrospective study on 309 patients under 15 years of age, operated on in our department from June 1998 to December 2002. The type of anesthesia, general or local, was noted. The latter consisted in a retrobulbar and/or a peribulbar injection, with 4 ml of 50% of lidocaine 2% and bupivacaine mixture., Results: Local anesthesia was given to 38.8% of patients, who had a mean age of 11.51 years, with a sex ratio of 2.4. The mean age of patients operated on with general anesthesia was 4.6 years. No complications were noted in the local anesthesia group. One operation was postponed because of lack of cooperation. In this group of operated patients, 62.5% had a cataract surgery, 16.7% a corneal laceration suture, and 10.0% mutilating surgery., Comments: Because of our working conditions, local anesthesia, more than a choice, is almost obligatory. Our study shows that local anesthesia in children's ocular surgery has many advantages and few disadvantages. However, this study is limited because of a lack of information on the anesthesia and postoperative reactions. A prospective study based on a questionnaire completed by the anesthesiologist and the surgeon at the end of surgery will be necessary., Conclusion: Ocular surgery under local anesthesia is possible in children as young as 10 years of age. Good psychological preparation of the patient and the presence of the parents, from the consulting room to operating room, are required.

The diagnosis of allergic conjunctivis begins by a meticulous questioning emphasizing the existence of ocular itching, the way of evolution of the signs and allergic preceeding. The examination searchs after follicles and papillae of the conjunctiva who usually go with serous discharges, blepharitis and keratitis. So four clinical forms may be described the chronic conjunctivitis, the vernal kerato-conjunctivitis, the atopic conjunctivitis and the giganto-papillar conjunctivitis. For the treatment, all non specific signs of allergy must be eliminated, the focal infections also and allergic substance isolated. If evolution is worse, an antiallergic eye drop is given until the disappearance of all the physical signs. In the same time, steroids and anti H1 drugs must be avoided. In case of failure, the specialist in allergy will be helpful to exam the patient.

Fungal infection is rarely investigated in keratitis. The authors report five cases of fungal keratitis observed at the le Dantec University Teaching Hospital of Dakar, Senegal, involving two males and three females. Diagnosis was made by examination of smears and cultures of corneal scrapings revealing Candida albicans isolated in four patients and Acremonium strictium in another after 2 or 12 weeks of treatment with antibiotics, antivirals, or steroids. Povidone iodine 2.3% concentrated eye drop was used alone or with an azole for 4 a mean of weeks. All patients presented corneal scars. Fungal keratitis must be considered in presence of torpid corneal ulcer and corneal scraping must be systematically done. Topical povidone iodine alone or associated with azole may be an alternative fungal keratitis treatment in intertropical areas.

Aim: To show the etiological, clinical, and epidemiological aspects of orbital cellulitis at the ophthalmological clinic of A. le Dantec hospital., Patients and Method: This is a retrospective study conducted from January 1994 to October 2003. Sixty-eight patient records were used. We noted patients' civil status, past medical history, clinical and paraclinical examinations, treatment received before and at admission to the clinic, and progression., Results: The incidence of orbital cellulitis was 8.9 cases per year. The average age of patients was 18 years and the sex ratio 2.78 in favor of males. Patients were hospitalized for a mean of 11 days. The fever was often stopped at admission. All patients had violent retrobulbar pain, associated with inflammatory exophthalmos in 77.8% of cases, and ophthalmoplegia in 67.2%. Two cases of diplopia were noted; 57.5% had sinusitis. Streptococcus was the bacterium found most frequently. In hospital, all patients received three antibiotics (ampicillin, aminoglycoside, metronidazole) and prednisone. In 51.5% of the cases, surgical treatment was necessary. Progression was favorable in 55.88% of the cases. Three patients died and 18 cases of blindness were noted., Conclusion: Orbital cellulitis is a young people's disorder with serious complications. This medical emergency requires a combination of effective antibiotics and a corticosteroid. Treating the source of infections is essential to avoid recurrence. In our practice, these three drugs in association in first intention was beneficial without an antibiogram.

Introduction: Compliance to medical treatment expresses the patient's perception of the disease and the treatment prescribed by the doctors. Lack of compliance endangers chronic glaucoma care, which explains the importance it has been given these last years. The objectives of this survey were to evaluate the compliance of adult patients suffering from primary open angle glaucoma to discover the influential factors., Materials and Methods: We conducted a survey at the ophthalmology clinic of Le Dantec Hospital from January 1997 to May 1998 among 31 adults being treated for primary open angle glaucoma. An indirect evaluation of the patients' compliance was made on the basis of a questionnaire after examination of their medical files. It was deemed good, average, or bad depending on: regularity of the patient's visits to the doctors, regularity of the treatment, respect of the doctor's prescription and the prescribed times for taking the medicine. The Chi square independence test was used to study the influence of the following factors: age, sex, residence, socioeconomic status, duration of symptom progression, level of instruction, counseling, and treatment., Results: The patients' mean age was 60.5 years. Compliance was deemed good for 29% of the total cases, average for 32.3%, and bad for 38.7%. Only factors such as the regular visits to the doctor, the regularity of the treatment, and respect of the doctor's prescription and the prescribed times for taking the medicine were found to be influential (p<0.05)., Conclusion: The medical treatment of primary open angle glaucoma, whether temporary or permanent, with a maximum of efficacy and a minimum of side-effects requires good compliance on the part of the patient. This compliance in turn requires a good doctor-patient relationship based on effective repeated counseling to educate patients, help them understand the disease, and act on the influential factors.

Purpose: Congenital cataract surgery can be performed by pars plana or limbal incision. We report our experience with scleral incision without ultrasounds in congenital cataract surgery., Material and Methods: Fifteen children with congenital cataract underwent surgery of both eyes (30 eyes). The zonular ciliaris and the lens anlage were normal in all cases. All procedures were performed by the same surgeon. A 3.2 mm scleral tunnel incision was made 2 mm from the limbus. Large capsulorhexis or capsulopuncture were performed after injection of a viscoelastic substance in the anterior chamber. After hydrodissection, the nucleus and cortex were aspirated. The wound was closed by apposition suture., Results: The mean age was 70.13 months (range 5 months to 130 months). Mean induced astimatism calculated with the Cravy method was 0.70 dipoters. A posterior capsular tear was observed in 1 case., Conclusion: Small scleral incision without ultrasounds has advantages. No expensive instruments are required and astimatism is not induced. The anterior chamber lies deep during the operation, protecting the endothelial cells and facilitating aspiration. Postoperative inflammation is minimal. The small scleral incision technique is useful in selected cases of congenital cataract.

Bundles of microtubular structures appear in the cytoplasm of spermatids of the African frog Dicroglossus occipitalis. They are observed in the vicinity of axonemes. Natural tubulin polymerization leads to the formation of hooks on microtubular structures. They can be related to experimentally induced tubulin hooks. The direction of curvature of the hooks allows us to define the polarity of the bundles. This is opposite to the polarity of axonemal microtubules: Bundles and axonemes are antiparallel. Under colchicine action, arch-like microtubular structures are shown to open in the same direction as they lock. This enables us to characterize their opening and locking site: It corresponds to the place of the "11th filament" described in microtubular structures such axonemes. The "11th filament" is thus demonstrated to be the most susceptible to natural opening and to the action of colchicine in microtubular structures.

Bundles of microtubular structures appear in the cytoplasm of germinal cells of the African frog Dicroglossus occipitalis. They are made of several associated microtubules. Every bundle contains one normal singlet and numerous arch-shaped microtubular structures growing in all directions from the singlet wall. The walls of these microtubules are shown to contain 10 to 13 protofilaments. Attempts made with colchicine point out their susceptibility to this antimitotic drug. The formation and opening of these microtubular structures give evidence of complex organization.