VOLUME 69 - ISSUE 1

PURPOSE: Evaluation of the cut quality of the Masyk® microkeratome in obtaining corneal flap from porcine eyes. METHODS: Prospective study with 31 porcine eyes divided into two groups: 15 eyes with programmed flap thickness of 160 µm and 9.5 mm diameter (Group 1), and 16 eyes with programmed flap thickness of 140 µm and 8.5 mm diameter (Group 2). Corneal thickness was calculated with a P55 pachymeter (Paradigm, USA) and the diameter with compass. RESULTS: No complications were observed during the use of the microkeratome. In group 1, the central corneal thickness mean was 146.33 ± 15.43 µm, range between 127 and 186 µm, and the vertical diameter mean was 9.39 ± 0.26 mm, range from 8.90 to 9.85 mm. In group 2, the central corneal thickness mean was 128.75 ± 18.83 µm, range from 71 to 178 µm, and the vertical diameter mean was 8.27 ± 0.20 mm, range from 7.95 to 8.65 mm. CONCLUSION: The Masyk® microkeratome showed to be effective and safe to produce corneal flaps with appropriate thickness and diameter in porcine eyes.

Keywords: Keratomileusis, laser in situ; Keratectomy, photorefractive, excimer laser; Cornea; Microsurgery

PURPOSE: To evaluate the level of ophthalmic information and the proper procedures in ophthalmic emergencies among non- ophthalmologists in charge of the emergency departments of General Hospitals. METHODS: A questionnaire containing personal data and other information was sent to the medical personnel in charge of emergencies of several general hospitals in Sorocaba (São Paulo) and region. Questions about the diagnosis and management of ocular emergencies were also sent. RESULTS: 100 non-ophthalmologists with 10.5-year average time of practice (1-44 years), of which 74% were male answered the questions. Several specialties were represented, the largest group (23%) being of general practitioners. The great majority (93%) felt insecure when in the presence of an ophthalmic emergency. CONCLUSIONS: There is a lack of information about the correct diagnosis and management of ocular emergencies among non-ophthalmologists in charge of general hospital emergency services. This study confirms the need of popularization of information among all medical specialties.

Keywords: Emergency service, hospital; Eye diseases; Emergencies; Health knowledge, attitudes, practice; Hospitals, general; Questionnaires

PURPOSE: Self-reported visual function questionnaires are becoming more common in clinical research. The purpose of this study is to evaluate and correlate self-reported visual function assessed by a visual function questionnaire with visual acuity. METHODS: 806 patients aged 60 years and older, who were included in an epidemiological eye study, were interviewed and present visual acuity for near and distance was taken; they also answered a visual function questionnaire. RESULTS: Weak correlations were found between self-reported visual function assessed by a visual function questionnaire and visual acuities for both distance and near. CONCLUSION: Self-reported visual function assessed by a visual function questionnaire did not correspond to visual acuity, nevertheless it can provide important information to the ophthalmologist.

Keywords: Vision; Visual acuity; Refractive errors; Self disclosure; Aged; Sickness impact profile; Questionnaires

PURPOSE: To evaluate the characteristics of the essential blepharospasm and hemifacial spasm patients and the feasible treatment with botulinum toxin A. METHODS: Thirty-four essential blepharospasm or hemifacial spasm patients were evaluated according to gender, ocular complaint, time of disease, treatment outcome and complications. RESULTS: Age median was 63 years and the mean was 61 years, with no difference regarding sex; 66.66% of the patients had hemifacial spasm and 33.33%, essential blepharospasm. Many patients complained of dry eye associated with involuntary spasm. Botulinum toxin A showed a positive outcome in 91.30% of the treated patients and complications observed after treatment were eyelid ptosis (8.33%) and buccal angle deviation (8.33%). CONCLUSION: Essential blepharospasm and hemifacial spasm occurred in the elderly, of both sexes. Treatment with botulinum toxin A was useful, with very low complication rates.

Keywords: Blepharospasm; Hemifacial spasm; Botulinum toxin type A; Action potentials; Oculomotor muscles

PURPOSE: To determine the potential risk of contamination of a trypan blue bottle (TB) after first use and after being stored under different temperature and humidity conditions, as well as to identify possible contamination factors, most frequently involved microorganisms and simultaneously evaluate bacteriostatic and bactericide properties of the dye. METHODS: An experimental and prospective study was carried out, in which 30 TB bottles were divided into 3 groups (A: control, B: refrigerator storage and C: cabinet storage). The dye was suctioned and cultivated in agar blood plates and Sabouraud agar tube. In group A, TB was cultivated immediately after the opening of the bottles (temperature zero - T0), in groups B and C cultivation occurred in T0, T1 (1 day), T2 (2 days), T7 (7 days) and T10 (10 days) after the opening of the bottles. On the 10th day, groups B and C bottles were also submitted to scraping of their inner walls after opening. Concurrently, the inhibitory action measurement test was conducted on the TB dye for the study of bacteriostatic and bactericidal activity. RESULTS: Cultivation procedures conducted in T0 presented no contamination. Among T1 and T10, added to the scraping there was only one contaminated bottle stored in the refrigerator. The encountered microorganism was Aspergillus niger. It has been proven that the dye does not show bactericide and bacteriostatic properties against the bacteria which were tested. CONCLUSIONS: Under this study's conditions there was no contamination of the bottles stored in cabinets and 1 bottle (10%) stored in the refrigerator showed contamination after opening and initial use. The source of contamination may possibly be the outer part of the product. TB does not show bactericidal and bacteriostatic properties against the tested bacteria and in the applied concentration.

Keywords: Trypan blue; Trypan blue; Aspergillus niger; Staining and labeling; Dyes; Cataract; Drug contamination

PURPOSE: To evaluate the conjunctival bacterial flora and its antibiotic resistance pattern in eyes of patients undergoing cataract surgery. METHODS: From August to October 2004, 50 patients undergoing cataract surgery in the "Fundação Altino Ventura", Recife, Brazil, were prospectively evaluated. Conjunctival material was obtained on the day of surgery, before the application of topical anesthetic, antibiotic or povidone-iodine. The collected material was inoculated and bacterioscopic analysis was carried out. In the cases where there was bacterial growth, antibiotic susceptibility tests and cultures, for isolation and identification of the bacteria, were performed. RESULTS: Of the 50 eyes, 43 (86.0%) had positive cultures. The coagulase-negative Staphylococcus (CNS), found in 27 (54.0%) eyes, was the most frequent organism. More than 90% of the isolates of this bacterium were susceptible to cephalotin, vancomycin, chloramphenicol, ofloxacin and gatifloxacin; 70 to 90% were susceptible to gentamicin, cefotaxime, oxacillin and ciprofloxacin; and less than 70% were sensible to neomycin. Four (10.5%) of the bacterial isolates were resistant to four or more antibiotics, two of them were CNS. CONCLUSION: The most frequent bacterium in the conjunctival flora is the coagulase-negative Staphylococcus. The isolates of this organism showed low susceptibility rate to neomycin, and high susceptibility rates to cephalotin, vancomycin, chloramphenicol, ofloxacin and gatifloxacin.

Keywords: Conjunctiva; Antibiotic prophylaxis; Drug resistance, microbial; Cataract extraction; Endophthalmitis; Staphylococcus

PURPOSE: To verify whether the tarsal strip procedure improves epiphora of patients with eyelid laxity but no ectropion. METHODS: A retrospective study was done with a sample of epiphora patients with lax eyelids in normal position and no nasolacrimal obstruction who were operated on with the tarsal strip technique. Fourteen lower eyelids, in 11 patients, were included in the study. RESULTS: Epiphora in ten eyes (71.4%) completely or significantly improved after a follow-up of three months. Eyelid laxity disappeared in all cases. CONCLUSION: In patients with epiphora, lax eyelids and patent lacrimal ducts, the tarsal strip procedure can significantly improve epiphora in most cases. As laxity ceased to exist in all eyelids, an assumption can be made that in some of the failures there may be other causes, concomitant with eyelid laxity, to explain perseverance of epiphora.

Keywords: Lacrimal apparatus diseases; Eyelids; Eyelids; Suture techniques; Retrospective studies; Aged

PURPOSE: To assess the influence of central and peripheral corneal thickness on the IOP measurement by Tonopen. METHODS: The IOP of 58 eyes from suspected and glaucomatous patients was evaluated by Goldmann´s tonometry (GT) and, by Tonopen XL on the central (TC) and peripheral (TP) regions of the cornea. Using the DGH 5100e pachymeter, we also measured the corneal thickness in its central (CCT) and peripheral (at 6:00 h) regions (PCT). Patients with any corneal changes were excluded. The mean values of all measurements was comparatively analyzed (GT x TC; GT x TP; TC x TP; CCT x PCT) by the paired t test and by regression and correlation analysis. RESULTS: The means (± standard deviation) of IOP obtained with GT, TC and TP were respectively 14.6 (±3.3) mmHg; 18.9 (±2.9) mmHg and 20.7 (±3.7) mmHg with a statistical highly significant difference (p<0.001). The means (±standard deviation) of central and peripheral corneal thickness were respectively 526 (±42.3) and 639 (±52.9) µm, also with a statistical highly significant difference (p<0.001). The correlation coefficients (r) between the measurements were 0.71 (p<0.001) for GT and TC; 0.65 (p<0.001) for GT and TP and 0.64 (p<0.001) for TC and TP. CONCLUSIONS: There was a positive correlation between the measurements performed with Tonopen XL and Goldmann´s tonometer at the central region of the cornea and the mean IOP was higher with Tonopen XL. The mean IOP obtained by TP was higher than that obtained by TC. These data showed that Tonopen XL, besides providing higher IOP readings than those with Goldmann´s tonometer, is influenced by the corneal thickness presenting higher IOP readings in the periphery than in the central region of the cornea.

Keywords: Cornea; Measures; Intraocular pressure; Tonometry, ocular

PURPOSE: To determine the retention of knowledge along the years after certification of physicians as ophthalmology specialists. METHODS: The physicians, former ophthalmology residents, were selected at the Department of Ophthalmology, State University of Campinas, São Paulo, Brazil, and randomly allocated to three groups of seven individuals, according to the time as specialists. Group 1 consisted of one-year specialists, group 2 of five-year specialists and group 3 of ten-year specialists. Each participant answered a test with twenty-five multiple choice randomly selected questions, based on the national certificate tests applied by the Brazilian Ophthalmology Council between 1994 and 2003. Each question scored four points. RESULTS: The mean age of groups 1, 2 and 3 was 27, 30 and 36 years, respectively. A preponderance of males was found in all groups. Group 1 achieved the highest score, average of 88, group 2 achieved 77, and group 3 achieved the lowest, average of 64 (p<0,05). CONCLUSION: Loss of knowledge retention amongst specialists of the Brazilian Ophthalmology Council, has been observed along the years after the certification.

Keywords: Education, Medical, Continuing; Clinical competence; Ophthalmology; Randomized controlled trials; Brazilian Ophthalmology Council

PURPOSE: To verify the influence of modality of treatment in regions of the glaucomatous visual field after reduction of intraocular pressure (IOP). METHODS: Glaucoma patients that had undergone a reduction of IOP of at least 20% in a period of 2 months were retrospectively selected and divided into 2 groups: 1) after trabeculectomy; 2) after clinical treatment. Visual field global indices and thresholds (average, divided according to the severity based on the Pattern Deviation plot) were compared before and after IOP reduction. RESULTS: Thirty-one eyes of 22 patients were selected (15 in group 1, and 16 in group 2). Both groups showed good ability regarding improvement of different regions of the visual field after IOP reduction. Only the percentage of reduction of IOP (52.3±18.9% and 37.8±15.2% for groups 1 and 2, respectively, p=0.02) and the percentage of improvement in the points damaged at p<0.5% (186.0±213.3% and 30.1±35.2% for groups 1 and 2, respectively, p=0.02) were different, but not statistically significant after alpha error correction between groups. CONCLUSION: The reduction of IOP above 20% may be associated with improvement in regions of the glaucomatous visual field, regardless of treatment modality.

Keywords: Intraocular pressure; Glaucoma; Perimetry; Tonometry, ocular; Retrospective studies; Treatment outcome

PURPOSE: To evaluate fibroblast proliferation activity of the Tenon capsule from primary and recurrent pterygia. METHODS: A randomized prospective study was performed with 43 surgical samples from 30 primary and 13 recurrent pterygia, and samples of normal Tenon capsule from the same pterygium patients. Proliferation, migration, and confluence rate, and patient age, lesion location and type (fleshy or involutive; primary or recurrent) were evaluated. Data were submitted to statistical analysis. RESULTS: Of the 30 cultivated primary pterygia, 21 migrated and proliferated, and 18 (60%) went to confluence. Migration, proliferation and confluence started much later in fibroblasts from normal Tenon than from pterygia lesion. The recurrent pterygia showed migration, proliferation, and confluence starting much earlier than the primary ones. There was no statistically significant difference in the start of migration, proliferation and confluence between fleshy and involuted pterygia, or between pterygias of Grades I-II and III-IV. CONCLUSION: Pterygium fibroblasts are more viable than normal Tenon in cell culture. Migration, proliferation, and confluence differ in primary and recurrent pterygia. Fleshy and involutive pterygia are similar in culture; there is also no difference between pterygia according to lesion size in cell culture.

Keywords: Pterygium; Recurrence; Cell proliferation; Fibroblasts; Conjunctiva

PURPOSE: From a quantitative point of view, to determine if the viscous friction forces could act as possible promoters of ocular stabilization keeping the rotational movements, which would provide the necessary values to be used in the ocular system. METHODS: A mechanical model was created to measure the necessary forces to overcome the friction of an alluminum sphere partially kept in a viscous liquid. Solutions of carboxymethylcellulose from 1.0% to 6.0% (with a variation of 0.5%) were used. Another variant to be considered was the area of contact between the sphere and the viscous liquid. RESULTS: After appropriate corrections and discounts a meaningful force (over 5 gf) was found in the solutions of carboxymethylcellulose at 3.5% or more in the largest contact area (587.8 mm²), in the solutions of carboxymethylcellulose at 4.5% or more in the intermediate area (335.9 mm²), in the solutions of carboxymethylcellulose at 5.5% and 6.0% in the smallest area (167.9 mm²). CONCLUSION: Some of the viscous liquids tested are apparently able to ensure enough friction force for ocular stabilization, specially the solutions of carboxymethylcellulose at 5.5% and 6.0% which provided good results in the smallest contact area.

Keywords: Oculomotor muscles; Eye movements; Nystagmus, pathologic; Strabismus; Viscosity; Carboxymethylcellulose; Optical rotation

PURPOSE: To evaluate the charts of patients with sensorial strabismus regarding range of different aspects, such as etiology, the type and the amount of deviation, relationship between the type of deviation and the patient's age when the disease occurred and the surgical outcome. METHODS: A retrospective analysis of data charts of 191 patients seen at the section of Ophthalmology at the University of São Paulo, from September 1990 to July 2002. RESULTS: There were 84 male and 107 female patients. The most frequent diagnosis responsible for low vision in the squinted eye was atrophic chorioretinitis in 49 patients. Eighty-seven were exotropes and 97 were esotropes. Fifty patients were operated on, but 8 of them were lost to follow-up. In 90.5% the surgical outcome was successful: less than 15 prismatic diopters of hyper or undercorrection after surgery. CONCLUSIONS: The good surgical outcome seen in this and other studies enhances and justifies the need for surgical correction of this type of strabismus.

Keywords: Esotropia; Depth perception; Strabismus; Visual acuity; Treatment outcome

PURPOSE: To determine the mycobiota of the healthy conjunctiva in diabetic individuals, according to diabetes type, age, sex, disease time, type of treatment, and stage of diabetic retinopathy of the individuals. To identify the anemophilus mycobiota in the sampling rooms. METHODS: A cross-sectional study was carried out on 803 diabetics who reside in the urban area of São Paulo-SP/Brazil. Sabouraud's dextrose agar culture with chloramphenicol was used for primoisolation, and the key of De Hoog was used to identify filamentous fungi. RESULTS: Of the evaluated diabetics, 6.6% (53/803) presented type 1 diabetes and 93.4% (750/803) type 2. The positive cultures for fungi in the conjunctiva of diabetics was 4.2% (34/803), with 1.9% (1/53) in type 1 diabetics and 4.4% (33/740) in type 2 diabetics (p=0.720). With respect to the presence or not of isolated fungi, there was no statistically significant association regarding age (p=0.575), sex (p=0.517), disease time (p=0.633), type of treatment (p=0.422), and diabetic retinopathy stage (p=0.655) of the tested individuals. The identified fungi were all filamentous: Aspergillus spp. represented 59.5% (25/42) of isolations and 47.6% (20/42) of isolated species were Aspergillus niger. Growth of anemophilus fungi occurred in the air of the room and coincidences were observed between the isolated species from the air and those from the conjunctiva. CONCLUSIONS: Presence of mycobiota in healthy conjunctivas of diabetics was identified, with no significant association between the greater number of positive fungi isolations and the type of diabetes, age, sex, disease type, type of treatment, and stage of diabetic retinopathy. In the collection rooms, anemophilus mycobiota was identified.

Keywords: Conjunctiva; Fungi; Diabetes mellitus; Diabetic retinopathy; Colony count, microbial; Aspergillus niger; Aspergillus; Urban population

PURPOSE: To describe the clinical evolution of cases with avulsed retinal vessels without retinal detachment treated with laser or scleral buckle. METHODS: Retrospective analysis of cases with avulsed retinal vessels treated between 2001-2003. Laser photocoagulation or scleral buckle was used. The minimum follow-up was 6 months. Average age was 53.6 years. RESULTS: Of 13 patients, 8 were photoagulated with argon laser and 5 were submitted to a scleral buckle. The most common symptom was reduction in visual acuity. Vitreous hemorrhage was present in 7 eyes (53.8%) at diagnosis, and was the most frequent complication after treatment (30.7%). Final visual acuity was unchanged. CONCLUSION: Avulsed retinal vessels have a good prognosis using laser or buckle. Late vitreous hemorrhage was the main complication.

Keywords: Retinal vessels; Retinal perforations; Laser surgery; Vitreous hemorrhage

PURPOSE: To describe and to evaluate the usefulness of Nd: Yag laser in pseudophakic children. METHODS: Twenty-four eyes of 22 pseudophakic patients with posterior capsule opacification, that had been submitted to posterior capsulotomy with Nd:Yag-laser were prospectively analyzed at the Infantile Cataract Section of the Federal University of São Paulo/Paulista School of Medicine, from June 2001 to March 2003. Age at surgery, IOL type, IOL placement, time interval between surgery and posterior capsule opacification, energy needed (mJ), laterality, initial and final visual acuity were analyzed. RESULTS: Capsulotomy was performed in all pseudophakic eyes. Four (16.6%) eyes received polyacrylic implants and 18 (75%) PMMA lenses. Twelve IOL were in the capsular bag and nine in the ciliary sulcus. The laser energy level required was 0,8 mJ to 2 mJ per spot, total amount was 100 mJ. Nd:Yag laser was feasible in 22 (91.6%) eyes. Only two (8.3%) eyes required capsulotomy surgery. CONCLUSION: The obtained results suggest that Nd:Yag laser capsulotomy may be a good option to improve visual acuity in pseudophakic children.

Keywords: Cataract; Cataract extraction; Vitrectomy; Lens implantation, intraocular; Visual acuity; Lens, capsule crystalline; Laser surgery; Child

We describe a rare case of Dandy-Walker syndrome malformation and its ocular alterations. A female child, aged 1 year and 9 month, with central nervous system alterations (Dandy-Walker syndrome), associated with low visual acuity, megalocornea (13 mm diameter in right eye and 13.5 mm in the left), fundoscopy with 0.7 optic papilla excavation in both eyes (BE) and temporal paleness in BE, intraocular pressure of 16 mmHg in the right eye and 14 mmHg in the left and anteroposterior diameter of 20.55 mm in both eyes.

Keywords: Dandy-Walker syndrome; Glaucoma; Nervous system malformation; Eye manifestations; Case reports

The authors report a case of congenital optic disc pit with serous macular detachment successfully treated, with argon laser photocoagulation in the temporal border of the pit, followed by intravitreous injection of C3F8 (100%) 0.3 ml. Patient was followed up for 12 months. Retinal reattachment was associated with improvement in visual acuity, as well as return of the fovea to its normal configuration shown by optical coherence tomography.

Keywords: Optic disk; Optic nerve diseases; Image processing, computer-assisted; Retinal detachment; Laser coagulation; Macula lutea; Case reports

We describe a patient with polyarteritis nodosa being treated with cytostatics and corticosteroids who developed an anterior ischemic optic neuropathy, a rare manifestation of this pathology.

Keywords: Polyarteritis nodosa; Polyarteritis nodosa; Adrenal cortex hormones; Eye manifestations; Optic neuropathy ischemic; Retinal vasculitis

Report of a complication related to the use of 0.1% trypan blue during capsular staining of the anterior crystalline lens capsule in an extracapsular cataract extraction with intraocular lens implantation. The capsular dye was injected using an air-bubble technique, inadvertently, it was done using high pressure dispersing the dye through the zonules leading to a complete losts of red reflex, the following steps of the procedure becoming more difficult after the cataract extraction and causing a temporary disturbance of visual acuity in the postoperative period. In order to avoid this complication, the authors also describe the use of "Modified air-bubble technique" where dispersive viscoelastic is placed into the iridolenticular space 360° to create a protection barrier.

Keywords: Cataract extraction; Trypan blue; Trypan blue; Capsulorhexis; Lens implantation, intraocular; Intraoperative complications; Case reports

PURPOSE: To report a case of bilateral retinal detachment associated with behavior changes. RESULTS: A 62-year-old, female patient presented agitated, complaining of progressive bilateral low vision for the 3 past months, along with anxiety and behavior changes. On examination, she had visual acuity of light perception in the right eye and conting fingers at 30 cm in the left eye; anterior chamber reaction; bilateral hyperemic and edematous optic disc and bilateral serous retinal detachment, yellow-white subretinal peripapillary plaques and subretinal and intraretinal exudation. On laboratory work-up, the patient had positive VDRL and FTA-Abs tests. Lumbar puncture was done; she had positive FTA-Abs and hemagglutination treponemal test on spinal fluid analysis. Neurosyphilis diagnosis was established, and the patient was admitted to the hospital for an intravenous penicillin course associated with oral prednisone (0.5 mg/kg). After 2 weeks, the patient showed marked improvement of her retinal findings, with reatachment of the retina and also an improvement of visual acuity. CONCLUSION: Syphilis is a pleomorphical disease, and may present as diffuse uveitis associated with bilateral exudative retinal detachment. Central nervous system involvement must always be evaluated and discarded; proper treatment may lead to visual function improvement and diminished sequelae.

Keywords: Syphilis; Syphilis serodiagnosis; Syphilis; Prednisone; Retinal detachment; Uveitis; False positive reactions; Neurobehavioral manifestations

The Authors describe a case where the initial diagnosis, clinical and laboratorial, was compatible with ocular toxocariasis. Therefore the follow-up added to a histopathologic examination disclosed a different diagnosis, proving the importance of the histopathologic examination, mainly in presumable diagnostics.

Keywords: Toxocariasis; Eye infections, parasitic; Granuloma; Uveitis; Biopsy; Diagnosis, differential

Skin cancer is the most common neoplasm in human beings and among them, basal cell carcinoma is the most prevalent. This report shows two cases with this tumor, located in the lateral canthus, affecting both the superior and inferior eyelids. The first case was a female, 72 years old, with amaurosis of the right eye. One year ago, she noted a tiny papule at the left lateral canthus. The CT scan revealed that the tumor had compromised about 80% of the left superior eyelid, 70% of the inferior eyelid and showed superficial invasion of the lateral orbital wall. The histopathological test diagnosed basal cell carcinoma, with clear margins. The reconstruction of both eyelids was done with Fricke's flap. The second patient was a female, 68 years old, who had an accident with multiple scars at the left side of her face two years before. One year later, she noted a small lesion at the left side of the lateral canthus. The CT scan showed that the tumor had affected about 90% of the left superior eyelid, 65% of the inferior eyelid and showed superficial invasion of the lateral orbital wall. The histopathological test diagnosed basal cell carcinoma, with clear margins. The reconstruction of both eyelids was done with Fricke's flap. The authors belive that although this flap is not the first choice for a reconstructive procedure, it should not be forgotten because in some patients, it would be the only possible choice.

Keywords: Carcinoma, squamous cell; Skin neoplasms; Surgical flaps; Eyelids; Case reports

The major aim of this overview was the visual perception of egocentric (distance from an observer to a target) and exocentric distance (distance between two targets). We considered different issues concerning the relationship between perceived distance and physical distance, giving special attention to the theories, to the cues regarding distance, how perceived distances are measured, and the types of visual environments where the measuring of distances occurred. We concluded that the perceived distance does not reflect a simple transformation of its physical counterpart; rather, the mapping between perceived distance and physical distance depends substantially on the type of visual environments where distances are measured, and, on the cue combination available in these environments.

Keywords: Depth perception; Space perception; Visual perception; Distance perception; Psychophysics; Optical illusions