Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RIGIDITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed2003

The case against rigid contact lenses.

Rigid lens fitting has been an integral part of contact lens practice for decades. However, rigid lens fitting has been constantly declining since soft lenses were introduced in the 1970s to whereby, world wide, rigid lenses constitute less than 10% of new contact lens fits. It seems that many practitioners correctly or incorrectly believe that rigid lenses only need to be prescribed in specialized or extenuating circumstances. This discussion article examines the international decline in rigid lens fitting and seeks to explain the cause of this trend. I conclude that rigid lenses will be virtually obsolete by the year 2010.

Contact Lenses↗
PubMed2004

Rigid, semirigid versus dynamic instrumentation for degenerative lumbar spinal stenosis: a correlative radiological and clinical analysis of short-term results.

STUDY DESIGN: Prospective comparative randomized clinical and radiologic study. OBJECTIVE: This study was conducted to compare the short-term effects of rigid versus semirigid and dynamic instrumentation on the global and segmental lumbar spine profile, subjective evaluation of the result, and the associated complications. BACKGROUND DATA: Lumbar spine fusion with rigid instrumentation for degenerative spinal disorders seems to increase the fusion rate. However, rigid instrumentation may be associated with some undesirable effects, such as increased low back pain following decrease of lumbar lordosis, fracture of the vertebral body and pedicle, pedicle screw loosening, and adjacent segment degeneration. The use of semirigid and dynamic devices has been advocated to reduce such adverse effects of the rigid instrumentation and thus to achieve a more physiologic bony fusion. MATERIALS AND METHODS: This study compared 3 equal groups of 45 adult patients, who underwent primary decompression and stabilization for symptomatic degenerative lumbar spinal stenosis. The patients of each group were randomly selected and received either the rigid (Group A), or semirigid (Group B), or dynamic (Group C) spinal instrumentation with formal decompression and fusion. The mean ages of the patients who received rigid, semirigid, and dynamic instrumentation were 65 +/- 9, 59 +/- 16, and 62 +/- 10 years, respectively. All patients had detailed roentgenographic study including computed tomography scan and magnetic resonance imaging before surgery to the latest follow-up observation. The following roentgenographic parameters were measured and compared in all spines: lumbar lordosis (L1-S1), total lumbar lordosis (T12-S1), sacral tilt, distal lordosis (L4-S1), segmental lordosis, vertebral inclination, and disc index. The SF-36 health survey and Visual Analogue Scale was used before surgery to the latest evaluation. RESULTS: All patients were evaluated after a mean follow-up of 47 +/- 14 months. Both lumbar and total lordosis correction did not correlate with the number of the levels instrumented in any group. Total lordosis was slightly decreased after surgery (3%, P < 0.05) in Group C. The segmentallordosis L2-L3 was increased after surgery by 8.5% (P < 0.05) in Group C, whereas the segmentallordosis L4-L5 was significantly decreased in Group Aand C by 9.8% (P = 0.01) and 16.2% (P < 0.01), respectively. The disc index L2-L3 was decreased after surgery in Group A and C by 17% (P < 0.05) and 23.5% (P < 0.05), respectively. The disc index L3-L4 was increased in Group C by 18.74% (P < 0.01). The disc index L4-L5 was after surgery decreased in all 3 groups: Group A by 21% (P = 0.01), Group B by 13% (P < 0.05), and Group C by 13.23% (P < 0.05). The disc index L5-S1 was significantly decreased in Group B by 13% (P < 0.05). The mean preoperative scores of the SF-36 before surgery were 11, 14, and 13 for Groups C, B, and A, respectively. In the first year after surgery, there was a significant increase of the preoperative SF-36 scores to 65, 61, and 61 for Groups C, B, and A, respectively, that represents an improvement of 83%, 77%, and 79%, respectively. In the second year after surgery and thereafter, there was a further increase of SF-36 scores of 19%, 23%, and 21% for Groups C, B, and A, respectively. The mean preoperative scores of Visual Analogue Scale for low back pain for Groups C, B, and A were 5, 4.5, and 4.3, respectively, and decreased after surgery to 1.9, 1.5, and 1.6, respectively. The mean preoperative scores of the Visual Analogue Scale for leg pain for Groups C, B, and A were 7.6, 7.1, and 6.9, respectively, and decreased after surgery to 2.5, 2.5, and 2.7, respectively. All fusions healed radiologically within the expected time in all three groups without pseudarthrosis or malunion. Delayed hardware failure (1 screw and 2 rod breakages) 1 year and 18 months after surgery without radiologic pseudarthrosis was observed in 2 patients in Group C. Asymptomatic radiolucent areas were shown around pedicle screws in the pedd pedicle screws in the pedicles L5 and S1 in 2, 3, and 4 cases in Group C, A, and B, respectively. There was no adjacent segment degeneration in any spine until the last evaluation. DISCUSSION AND CONCLUSION: This comparative study showed that all three instrumentations applied over a short area for symptomatic degenerative spinal stenosis almost equally after surgery maintained the preoperative global and segmental sagittal profile of the lumbosacral spine and was followed by similarly significant improvement of both self-assessment and pain scores. Hardware failure occurred at a low rate following dynamic instrumentation solely without radiologically visible pseudarthrosis or loss of correction. Because of the similar clinical and radiologic data in all three groups and the relative small number of patients that were included in each group, it is difficult for the authors to make any recommendation in favor of any instrumentation.

Aged↗
PubMed2004

Long-term skeletal stability after maxillary advancement with distraction osteogenesis using a rigid external distraction device in cleft maxillary deformities.

Rigid external distraction is a highly effective technique for correction of maxillary hypoplasia in patients with orofacial clefts. The clinical results after correction of sagittal maxillary deformities in both the adult and pediatric age groups have been stable. The purpose of this retrospective longitudinal cephalometric study was to review the long-term stability of the repositioned maxilla in cleft patients who underwent maxillary advancement with rigid external distraction. Between April 1, 1995, and April 1, 1999, 17 consecutive patients with cleft maxillary hypoplasia underwent maxillary advancement using rigid external distraction. There were 13 male patients and four female patients, with ages ranging from 5.2 to 23.6 years (mean, 12.6 years). After a modified complete high Le Fort I osteotomy and a latency period of 3 to 5 days, patients underwent maxillary advancement with rigid external distraction until proper facial convexity and dental overjet and overbite were obtained. After active distraction, a 3- to 4-week period of rigid retention was undertaken; this was followed by removable elastic retention for 6 to 8 weeks using, during sleep time, an orthodontic protraction face mask. Cephalometric radiographs were obtained preoperatively, after distraction, at 1 year after distraction, and 2 or more years after distraction. The mean follow-up was 3.3 years (minimum, 2.1 years; maximum, 5.3 years). The following measurements were obtained in each cephalogram: three linear horizontal and two linear vertical maxillary measurements, two angular craniomaxillary measurements, and one craniomandibular measurement. Differences between the preoperative and postoperative cephalometric values were analyzed by paired t tests (p < 0.05). The cephalometric analysis demonstrated postoperatively significant advancement of the maxilla. In addition, the mandibular plane angle opened 1.2 degrees after surgery. After the 1- to 3-year follow-up period, the maxilla was stable in the sagittal plane. Minimal anteroposterior growth was observed in the maxilla compared with that exhibited in the anterior cranial base. However, there was significant vertical maxillary growth over the 3-year observation period. The mandibular plane angle tended to decrease during the follow-up period. The cephalometric data from this study support the clinical impression of maxillary stability after maxillary advancement with rigid external distraction in cleft patients. This effective and stable technique is now considered for all pediatric patients with severe cleft maxillary hypoplasia and for adolescent and adult patients with moderate to severe deformities.

Abnormalities, Multiple↗
PubMed2003

Rigidity percolation in a field.

Rigidity percolation with g degrees of freedom per site is analyzed on randomly diluted Erdös-Renyi graphs, with average connectivity gamma, in the presence of a field h. In the (gamma,h) plane, the rigid and flexible phases are separated by a line of first-order transitions whose location is determined exactly. This line ends at a critical point with classical critical exponents. Analytic expressions are given for the densities n(F) of uncanceled degrees of freedom and gamma(r) of redundant bonds. Upon crossing the coexistence line, gamma(r) and n(F) are continuous, although their first derivatives are discontinuous. We extend, for the case of nonzero field, a recently proposed hypothesis, namely, that the density of uncanceled degrees of freedom is a "free energy" for rigidity percolation. Analytic expressions are obtained for the energy, entropy, and specific heat. Some analogies with a liquid-vapor transition are discussed. Particularizing to zero field, we find that the existence of a (g+1) core is a necessary condition for rigidity percolation with g degrees of freedom. At the transition point gamma(c), Maxwell counting of degrees of freedom is exact on the rigid cluster and on the (g+1) rigid core, i.e., the average coordination of these subgraphs is exactly 2g, although gamma(c), the average coordination of the whole system, is smaller than 2g. gamma(c) is found to converge to 2g for large g, i.e., in this limit Maxwell counting is exact globally as well.

Journal Article↗
PubMedDate not supplied

Children's attention to rigid and deformable shape in naming and non-naming tasks.

In four experiments with three-year-olds (N = 67), we investigate children's understanding of the differential importance of shape for categorization of solid rigid objects with fixed shapes and solid but deformable objects with shapes that can be changed. In a non-naming task we find that young children categorize rigid and deformable things differently and know that material is important for deformable things and shape for rigid things. In two naming tasks, however, children generalize names for both solid and deformable objects by shape similarity and disregard rigidity. To understand this pattern of results we examine a corpus of early-learned nouns and the kinds of rigid and nonrigid things named by nouns in that corpus. The results suggest that names for categories of solid, rigid objects in which instances are similar in shape dominate children's early noun vocabularies. We suggest that children's novel word generalizations for deformable things may be overgeneralizations of this dominant pattern.

Attention↗
PubMed2006

Comparison of the International Index of Erectile Function erectile domain scores and nocturnal penile tumescence and rigidity measurements: does one predict the other?

OBJECTIVE: To describe the relationship between the International Index of Erectile Function (IIEF) erectile domain score, and nocturnal penile tumescence and rigidity values measured by RigiScan (Timm Medical Technologies, Eden Prairie, MN). PATIENTS AND METHODS: In all, 73 men were evaluated with the IIEF and 2 nights of continuous penile monitoring with the RigiScan. Twenty-six men were evaluated before and after prostatectomy, for a total of 99 pairs of data points. We dichotomized the RigiScan results as 'adequate' (no erectile dysfunction, ED), or 'inadequate' (having ED), based on the 'best erectile event' over the 2 nights of monitoring. Two separate criteria for adequate erectile function were used, one of >70% rigidity for > or = 10 min, and the other >60% rigidity for > or = 10 min. The erectile domain score of the IIEF was calculated in the standard fashion. RESULTS: Using both the 70% and the 60% rigidity criteria, there was a statistically significant association between the IIEF erectile domain scores and the RigiScan data (r = 0.27, P = 0.008 and r = 0.29, P = 0.003, respectively). However, the sensitivity of the IIEF to predict ED based on RigiScan results using the 70% rigidity criteria was 68.9%, and the specificity was 57.1%. When the IIEF was used as a continuous predictor of RigiScan results, the area under the receiver-operating characteristic (ROC) curve was 0.66. Using the 60% criteria, the sensitivity was 55.8% and the specificity was 73.2%; the area under the ROC curve was 0.72. CONCLUSIONS: IIEF erectile domain scores and nocturnal penile tumescence and rigidity measurements are weakly associated, and the clinical utility of one test to predict the other is limited. However, because of the differences in the measured outcomes (perception of erectile function vs physiological capacity), a weak association does not disqualify either test's individual utility.

Adult↗
PubMed1992

Rigidity of various fixation methods used as dental splints.

Horizontal and vertical rigidity of teeth fixed with seven types of dental splints were evaluated by two tooth mobility measuring devices. Altogether 21 dissected sheep mandibles including soft tissues were used for the experiments in which Fermit, flexible wire-composite, Kevlar, Fiber, Protemp, rigid wire-composite and Triad Gel splints were applied to four incisors. The mean rigidity of the central incisors within the splint was measured by means of Mühlemann periodontometer (horizontal mobility) and Periotest (horizontal and vertical mobilities). Mobility values of teeth before splinting were used as covariants and the values with the splints were illustrated as adjusted mobility. Statistical significance between the rigidity of various splints was analyzed by an unpaired t-test. It was shown that the most rigid splints both in horizontal and vertical directions were Triad Gel, rigid wire-composite and Fermit splints. Kevlar and Fiber splint allowed more horizontal movement than other splints. Protemp and flexible wire-composite splints proved to produce adequate lateral support for the fixed teeth and allowed vertical flexibility which is experimentally known to improve periodontal healing of luxated teeth.

Acrylic Resins↗
PubMed1987

Cognitive rigidity in suicide attempters.

A number of investigators have reported evidence of cognitive rigidity in suicide attempters (e.g., Levenson & Neuringer, 1971; Neuringer, 1964; Patsiokas, Clum, & Luscomb, 1979). It is important to note, however, that in all of the studies that found suicide attempters to be rigid, the test batteries had been administered to persons during their period of hospitalization immediately following a suicide attempt-thus, presumably, while they were still in the crisis period. The present study was designed as a step toward determining whether cognitive rigidity is a personality trait of suicide attempters or simply a transient characteristic limited to the crisis period. We administered tests for rigidity to persons who had attempted suicide but were well past the crisis period. These persons were less rigid than attempters from previous studies on the Rokeach Map Test (p less than .05) and the Alternate Uses Test (p less than .001). The implication is that if indeed there is a suicidal personality, rigidity is not a defining trait.

Adolescent↗
PubMed1997

Indications for flexible versus rigid bronchoscopy in children with suspected foreign-body aspiration.

Diagnostic indications for flexible bronchoscopy in the initial investigation of children with suspected foreign-body (FB) aspiration have not been evaluated prospectively. We prospectively collected history, clinical, and radiologic findings at prebronchoscopic examination of all children referred for suspected FB aspiration between February 1993 and September 1995. Children with asphyxiating FB aspiration, requiring immediate rigid bronchoscopy, were excluded. If there was clear evidence of FB aspiration from the physical and radiographic findings, rigid bronchoscopy was directly performed. If the evidence was not convincing, children underwent diagnostic flexible bronchoscopy under local anesthesia. If an FB was found, rigid bronchoscopy was always performed for extraction. Eighty-three consecutive children (median age: 24 mo) were included. Among 28 who underwent rigid bronchoscopy first, 23 had an FB. Among the 55 children who underwent flexible bronchoscopy first, 17 had an FB. Predictive signs of a bronchial FB were a radiopaque FB, and associated unilaterally decreased breath sounds and obstructive emphysema (positive predictive value = 0.94). We propose the following management algorithm: Rigid bronchoscopy is performed first in case of asphyxia, a radiopaque FB, or association of unilaterally decreased breath sounds and obstructive emphysema. In any other case, flexible bronchoscopy is performed first for diagnostic purposes. If applied retrospectively to the 83 children in our study, this algorithm would have decreased the negative first rigid bronchoscopy rate to 4%. Flexible bronchoscopy is a safe and cost-saving diagnostic procedure in children with suspected FB aspiration.

Algorithms↗
PubMed1989

Structure from two orthographic views of rigid motion.

We study the inference of rigid three-dimensional interpretations for the structure and motion of four or more moving points from but two orthographic views of the points. We develop an algorithm to determine whether image data are compatible with a rigid interpretation. As a corollary of this result we find that the measure of false targets (roughly, nonrigid objects that appear rigid) is zero. We find that if the two views have at least one rigid interpretation, then in fact there is a canonical one-parameter family of rigid interpretations; we show how to compute this family, and we describe precisely how the rigid interpretations vary within it. Since only two views are used, this analysis is relevant also to stereo vision.

Algorithms↗
PubMed2006

Transparent endoscopic sheath and rigid-rod endoscope used in endoscopic third ventriculostomy for hydrocephalus in the presence of deformed ventricular anatomy.

OBJECT: Endoscopic third ventriculostomy (ETV) has been widely performed for the treatment of noncommunicating hydrocephalus. In cases of hydrocephalus in conjunction with deformed and complex ventricular anatomy, it is preferable to use a rigid-rod endoscope for ETV, because the excellent visibility provided by this instrument yields a smooth and correct orientation in the ventricle. The authors report on ETV procedures in which they used a transparent endoscopic sheath that has a common channel in which a rigid-rod endoscope and an instrument can be inserted. METHODS: In 15 cases of noncommunicating hydrocephalus, a transparent endoscopic sheath and a rigid endoscope were used for ETV. In 11 of the 15 patients, the diameter of the foramen of Monro and the width of the third ventricle were greater than 5 mm, and thus a transparent endoscopic sheath and a rigid endoscope could be smoothly introduced through the foramen of Monro and an ETV successfully performed. Four patients had congenital or acquired narrowing of the foramen of Monro and an anatomically deformed ventricular system. In three of the patients, opening of the narrowed foramen and an ETV were successfully performed using the transparent endoscopic sheath under direct visualization through the rigid-rod endoscope. CONCLUSIONS: A transparent endoscopic sheath increases safety by offering a corridor to the third ventricle. It also provides excellent visibility without troublesome bleeding from tissues surrounding the foramen of Monro during endoscopic procedures in which a rigid endoscope is used.

Adolescent↗
PubMedDate not supplied

Structural determinants of the rigidity of the red cell membrane.

Although the stability and viscoelasticity of the red cell membrane are undoubtedly governed by the membrane's underlying protein skeleton, the mechanism by which this network controls elasticity is uncertain. The structural constraints, that impose end-to-end spacing on the spectrin molecules well below that in free solution, may impart rubbery (entropic) elasticity to the system. However, other enthalpic and entropic contributions due to interactions between spectrin chains or between spectrin and other proteins, the lipid bilayer or the solvent must also prevail. To relate structural features to elasticity, explicit measurements of membrane rigidity are required. The most widely used measurement is that of the membrane shear elastic modulus by micropipette aspiration. Analysis of genetic variants of membrane structure have shown that the density of spectrin is directly correlated with membrane rigidity. Although cross-linking of the skeleton increases rigidity, interruption of the continuity of the network by dissociating spectrin tetramers into dimers does not reduce rigidity as might be expected. On the other hand, external ligands that cause new interactions between integral proteins and the skeletal network do increase rigidity. Moreover, hereditary ovalocytes, which have a deletion of 9 amino acids from band 3 at the first point of entry into the membrane, are extremely rigid. This mutation is associated with decreased translational and rotational mobility of the band 3, and may impair flexural freedom of its cytoplasmic domain. It thus appears that elasticity may be regulated not only by the structure of the spectrin network, but also by its interactions with and freedom of motion relative to the lipid bilayer.

Chemical Phenomena↗
PubMed1990

Discriminating rigid from nonrigid motion: minimum points and views.

Theoretical investigations of structure from motion have demonstrated that an ideal observer can discriminate rigid from nonrigid motion from two views of as few as four points. We report three experiments that demonstrate similar abilities in human observers: In one experiment, 4 of 6 subjects made this discrimination from two views of four points; the remaining subjects required five points. Accuracy in discriminating rigid from nonrigid motion depended on the amount of nonrigidity (variance of the interpoint distances over views) in the nonrigid structure. The ability to detect a rigid group dropped sharply as noise points (points not part of the rigid group) were added to the display. We conclude that human observers do extremely well in discriminating between nonrigid and fully rigid motion, but that they do quite poorly at segregating points in a display on the basis of rigidity.

Adult↗
PubMed1999

Rigid contact lens fitting relationships in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group.

PURPOSE: Although the influence of flat-fitting contact lenses on corneal scarring in keratoconus is frequently debated, the current standard of care with regard to the apical fitting relationship in keratoconus remains undocumented. METHODS: Patients were examined at baseline in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study (N = 1209). Patients wearing a rigid contact lens in one or both eyes (N = 808) had their habitual rigid contact lenses analyzed, and the fluorescein patterns and base curves were compared to the first definite apical clearance lens (FDACL). The FDACL is the flattest lens in the CLEK Study trial lens set that exhibits an apical clearance fluorescein pattern. For patients wearing a rigid contact lens in both eyes, one eye was selected randomly for analysis. RESULTS: Twelve percent of the rigid contact lens-wearing eyes were wearing lenses fitted with apical clearance based upon the clinician's fluorescein pattern interpretation. The remainder (88%) was wearing lenses fitted with apical touch. For mild (steep keratometric reading <45 D) keratoconus corneas, the mean estimate of the base curve to cornea-fitting relationship was 1.18 D flat (SD +/- 1.84 D); moderate (steep keratometric reading: 45 to 52 D) corneas were fitted on average 2.38 D flat (SD +/- 2.56 D); and severe (steep keratometric reading > 52 D) corneas were fitted an average of 4.01 D flat (SD +/- 4.11 D). CONCLUSIONS: Despite the potential risk for corneal scarring imposed by flat-fitting rigid contact lenses, most CLEK Study patients wear flat-fitting lenses. Overall, rigid lenses were fitted an average of 2.86 D (SD +/- 3.31 D) flatter than the FDACL.

Contact Lenses↗
PubMed2000

A comparative study of skeletal and dental stability between rigid and wire fixation for mandibular advancement.

This study examined the skeletal and dental stability after mandibular advancement surgery with rigid or wire fixation for up to 2 years after the surgery. Subjects for this multisite, prospective, randomized, clinical trial were assigned to receive rigid (n = 64) or wire (n = 63) fixation. The rigid cases received three 2-mm bicortical position screws bilaterally and elastics; the wire fixation subjects received inferior border wires and 6 weeks of skeletal maxillomandibular fixation with 24-gauge wires. Cephalometric films were obtained before surgery, and at 1 week, 8 weeks, 6 months, 1 year, and 2 years after surgery. Skeletal and dental changes were analyzed using the Johnston's analysis. Before surgery both groups were balanced with respect to linear and angular measurements of craniofacial morphology. Mean anterior advancement of the mandibular symphasis was 5.5 mm (SD, 3.2) in the rigid group and 5.6 mm (SD, 3.0) in the wire group. Two years after surgery, mandibular symphasis was unchanged in the rigid group, whereas the wire group had 26% of sagittal relapse. Dental compensation occurred to maintain the corrected occlusion, with the mandibular incisor moving forward in the wire group and posteriorly in the rigid group. However, at 2 years after surgery, when most subjects were without braces, the overjet and molar discrepancy had relapsed similarly in both groups.

Adolescent↗
PubMed1991

[The late results after mobilizing bone resections in posttraumatic rigidity of the elbow].

Two categories of posttraumatic rigidities are distinguished: partial and total. The severity of partial rigidities depends on the residual flexion-extension amplitude arch and they are divided accordingly into functional rigidities, with a residual amplitude arch of 60-100 degrees, and non-functional ones, with residual flexion amplitude arches of 0-80 degrees or over 100 degrees. The severity of total rigidities depends mainly on the preservation or loss of the pronation-supination movement. To the department where the authors are working were admitted during 16 years (1970-1986), 54 cases of posttraumatic rigidities of the elbow, on which 63 operations were performed. The surgical indications were established according to the anatomopathological type of lesions, to the time elapsed from the accident, to the age and occupation of the patient and to the residual amplitude arches. The late results were checked up after 1-10 years, on the average after 3-4 years, by comparison of pre- and postoperative Rocher indices. The flexion-extension movements benefitted postoperatively by 70% in total rigidities and by 45% in the partial ones and the pronation-supination movements, by 40%. The results regarding the change of the biomechanical functionality conditions following the mobilizing bone resections are shown in comparison with those obtained by arthrosis and total elbow prostheses.

Adult↗
PubMed1990

Rigidity in mentally retarded and nonretarded children.

The dependence of rigidity on task difficulty was examined. The hypothesis was that mentally retarded subjects would be more rigid than would nonretarded subjects on difficult but not on easy tasks. An intelligence test and seven rigidity tests varying in difficulty were administered to 45 retarded and 45 MA-matched nonretarded subjects. Factor analyses yielded one rigidity factor for the retarded group and two for the nonretarded group. In both groups the rigidity tests were interrelated and formed a Guttman simplex structure in terms of difficulty. The groups did not differ on three easy tests but did differ on four more difficult tests. The results were interpreted mainly in a motivational framework, with implications concerning mental retardation and rigidity as an interactional concept.

Attention↗
PubMed1987

The use of spherical power effect bitoric rigid contact lenses in hospital practice.

In this retrospective study of astigmatic contact lens dispensing in the hospital setting, 680 patients were noted to have been dispensed new contact lens prescriptions over a specific 20-month period. Seventy-five patients (11%) received at least one astigmatic rigid or hydrogel contact lens. Forty-nine patients received at least one rigid astigmatic lens; 43 patients (63 eyes)--or about 87% of all rigid lens fittings--were dispensed spherical power effect (SPE) design rigid contact lenses. We find that we usually prescribe bitoric rigid lenses with the flatter (longer) meridian of the lens base curve about 0.50 diopters steeper than the flattest (longest) corneal meridian. Mean diameter was 9.3 mm, and about 80% of lenses were made from rigid gas permeable materials. The majority of patients were successful from a clinical perspective, with most attaining visual acuity equal to or better than with maximum spectacle correction, and with good comfort and physiological results.

Adolescent↗