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Biomedical subjects

A Vasavada

Publications and source records attributed to A Vasavada.

At least 19 recordsLinked to original sources
PubMed2001

Phacoemulsification in Indian eyes with pseudoexfoliation syndrome.

PURPOSE: To evaluate the intraoperative and postoperative behavior after phacoemulsification in Indian eyes with pseudoexfoliation syndrome. SETTING: Iladevi Cataract & Intraocular Lens Research Centre, Ahmedabad, India. METHOD: Ninety eyes were prospectively evaluated. Group 1 (cohort) comprised 45 consecutive eyes with pseudoexfoliation and coexisting cataract and Group 2 (control), 45 consecutive normal eyes with senile cataract only. Phacoemulsification was performed by a single surgeon using a step-by-step, chop in situ, and lateral separation technique. An AcrySof intraocular lens was implanted in the bag in all eyes. Intraoperative observations included pupil size after maximal mydriasis, phakodonesis, zonular dehiscence, grade of cataract, and capsule tear/rupture. Postoperatively, intraocular pressure (IOP), best corrected visual acuity, aqueous flare/cell response, and the presence of posterior synechias were evaluated at 1 day and 1 month. A chi-square test was used for statistical analyses. RESULTS: The mean pupil size was significantly smaller in Group 1 (P =.0000). No eye in either group had phakodonesis. Sixty percent of eyes in Group 1 and 31% in Group 2 had a hard cataract (P =.008). Endocapsular phacoemulsification was performed in 82% of eyes in Group 1 and 84% of eyes in Group 2. Intraoperative complications such as zonular or capsular dehiscence were not seen in any eye. Postoperatively, IOP and aqueous cell response were comparable between groups (P =.11 and P = 0.81, respectively). A significantly higher flare response was observed in Group 1 (P =.000). The visual outcome at 1 month was similar between groups. CONCLUSIONS: The intraoperative performance of Indian eyes with pseudoexfoliation was comparable to that in normal eyes. A good surgical outcome is ensured by using an appropriate surgical technique. Apart from a higher flare response, the postoperative outcomes in eyes with pseudoexfoliation were within normal limits, and the outcome at 1 month was satisfactory.

Aged↗
PubMed2000

Observation of moist convection in Jupiter's atmosphere. Galileo Imaging Team

The energy source driving Jupiter's active meteorology is not understood. There are two main candidates: a poorly understood internal heat source and sunlight. Here we report observations of an active storm system possessing both lightning and condensation of water. The storm has a vertical extent of at least 50 km and a length of about 4,000 km. Previous observations of lightning on Jupiter have revealed both its frequency of occurrence and its spatial distribution, but they did not permit analysis of the detailed cloud structure and its dynamics. The present observations reveal the storm (on the day side of the planet) at the same location and within just a few hours of a lightning detection (on the night side). We estimate that the total vertical transport of heat by storms like the one observed here is of the same order as the planet's internal heat source. We therefore conclude that moist convection-similar to large clusters of thunderstorm cells on the Earth-is a dominant factor in converting heat flow into kinetic energy in the jovian atmosphere.

Journal Article↗
PubMed2000

Phacoemulsification in eyes with a small pupil.

PURPOSE: To evaluate the intraoperative difficulties and long-term outcome of phacoemulsification through a small pupil using minimal iris manipulation. SETTINGS: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. METHODS: This prospective study included 30 consecutive eyes with a maximally dilated pupil size of 4.0 mm or smaller. Except synechiolysis and occasional pupil retraction with a chopper, no iris manipulation was performed. The phacoemulsification technique included creation of deep central space, use of a low aspiration flow rate with appropriate vacuum, and step-by-step chop in situ and lateral separation of the nucleus. Patients were examined 1 day, 1 week, 1 and 3 months, and 1 year postoperatively. Specular microscopy was performed at 1 month and 1 year. RESULTS: Fourteen eyes had chronic iritis, 12 had glaucoma surgery, 2 had pseudoexfoliation, and 2 had a rigid pupil. Mean follow-up was 13.6 months. Eighteen eyes (60%) had hard cataract. Mean preoperative pupil size was 2.80 mm +/- 0.75 (SD). Mean pupil size before the capsulorhexis was initiated was 4.42 +/- 0.58 mm. The iris was bruised in 10 eyes during cortex removal. Trace amounts of cortex were left in 4 cases. Two eyes had increased intraocular pressure in the early postoperative period. Six patients had a minimal amount of retained viscoelastic material (pseudofibrin), and 2 patients developed a sterile hypopyon. Sixteen eyes had cell deposits on the IOL surface and 12 eyes, fine uveal pigments. In 2 eyes with previous glaucoma surgery and in all eyes with iritis except 2, posterior synechias reformed. CONCLUSIONS: Successful phacoemulsification was done with minimal or no pupil-widening maneuvers, restoring the preoperative pupil configuration.

Adult↗
PubMed1999

Phacoemulsification in eyes with posterior polar cataract.

PURPOSE: To evaluate the results of phacoemulsification in eyes with posterior polar developmental cataract and to appraise the strategy for surgical management. SETTING: Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, Ahmedabad, India. METHOD: This prospective study comprised 25 consecutive patients. All surgeries were performed by 1 surgeon. Endophacoemulsification was carried out after hydrodelineation. Hydrodissection or rotation was not attempted. A 2-port vitrectomy was performed when necessary. RESULTS: Mean follow-up was 13.72 months (range 7 to 22 months). Nine patients (36%) developed posterior capsule rupture and 8 (32%) revealed plaques. An intraocular lens (IOL) was implanted in all 25 eyes. In 8 of 9 cases with rupture, the haptics were placed in the sulcus; in 1 case, the IOL was placed in the bag. One patient in the capsular rupture group developed macular edema 3 weeks postoperatively that responded to conservative treatment. Among 25 patients, 18 had a visual acuity of 20/20 to 20/30 and 6, 20/80 to 20/120. These 6 patients had residual posterior capsule plaque. All except 2 patients with plaque required a neodymium:YAG capsulotomy. In these patients, visual acuity improved to 20/30. In 1 patient, with microcornea, acuity did not improve to beyond 20/120. CONCLUSION: This study confirms the predisposition to posterior capsule rupture in eyes with posterior polar cataracts. Careful surgical planning produces satisfactory technical and visual outcomes.

Adolescent↗
PubMed1999

Surgical techniques for difficult cataracts.

This article reviews some of the advances that have taken place in the surgical techniques for difficult cataracts such as rock-hard, white, and posterior polar cataracts. Fashioning a central space, modified chopping maneuvers, and creation of multiple small fragments have enabled the surgeon to consistently achieve a successful outcome. A judicious combination of chop and separation movement in a step-by-step manner reduce the stress of the procedure and make it safer. Raised intracapsular pressure and poor visibility are dealt with through various innovative techniques. Use of high-viscosity sodium hyaluronate and double capsulorhexis allow the surgeon to achieve capsulorhexis with a high success rate. A controlled and gentle approach to phacoemulsification has proven to be the key factor for success in posterior polar cataracts.

Cataract↗
PubMed1998

Graded thoracolumbar spinal injuries: development of multidirectional instability.

Injuries of the thoracolumbar spine are serious, disabling, and costly to society. These injuries vary from mild ligament tears to severe bony fractures. Increased range of motion (ROM) and neutral zone (NZ) have been suggested as indicators of the resulting clinical instability. The purpose of the present study was to investigate the relative sensitivities and merits of the ROM and NZ in relation to spinal injuries of the thoracolumbar junction. A graded spinal trauma experiment was designed, in which the threshold of injury and injury progression were examined. Ten thoracolumbar human spine specimens (T11-L1) were traumatized using a high-speed incremental trauma model. The ROM and NZ, which indicate altered mechanical properties, were determined for three physiological motions: flexion/extension (FE), lateral bending (LB), and axial rotation (AR). The injury threshold was found to be 84 J (or 84 Nm) by examining both ROM and NZ for all motion types (P < 0.05), but the NZ was more sensitive. At the injury threshold, the NZ showed an overall average increase of 566% above that of the intact, while the equivalent increase in the ROM was only 94%. The NZ was also a more sensitive parameter documenting the progression of the injury beyond the injury threshold. After the maximum trauma of 137 J, the NZs for the three motions (FE, LB, and AR) increased by 700%, 1700%, and 3000% above their respective intact values. Corresponding increases in the ROM were much smaller: 115%, 184%, and 425% respectively. Direct extrapolation of the in vitro experimental findings to the clinical situation, as always, should be done with care. Our findings, however, suggest that the ROM, as measured from functional radiographs of a traumatized patient, may underestimate the true injury to the spinal column.

Adult↗
PubMed1998

Phacoemulsification of white mature cataracts.

PURPOSE: To evaluate the intraoperative difficulties associated with phacoemulsification of white mature cataracts and develop a strategy for consistently achieving continuous curvilinear capsulorhexis (CCC) in these cases. SETTING: Raghudeep Eye Clinic, Iladevi Cataract & IOL Research Centre, Ahmedabad, India. METHODS: This prospective study comprised 60 eyes of 60 patients with senile white mature cataract. Mean follow-up was 7 months. Detailed preoperative and intraoperative notes were made including intraoperative subjective assessment of the intracapsular pressure and cataract hardness. A small capsulorhexis was attempted initially. Endophacoemulsification was performed using the stop, chop, chop, and stuff technique. The capsulorhexis was enlarged before intraocular lens implantation. An initial cut in the capsulorhexis margin was made with a cystotome needle while a spatula supported the anterior capsule. The capsulorhexis was then enlarged with forceps. RESULTS: A CCC was achieved in 57 eyes (95%). Intracapsular pressure was judged to be raised in 24 eyes (40%). Of these, CCC was accomplished in 21 eyes (88%). Statistical analysis confirmed that raised intracapsular pressure was a significant factor. Capsule opacification or plaque was detected at the end of the surgery in 20 eyes (33%); 50% of the nuclei were of grade 5 hardness. CONCLUSION: If a CCC can be achieved, the results of white cataract phacoemulsification are comparable to those of routine cataract surgery. When using the two-stage technique, one should be prepared to deal with a hard cataract through a small capsulorhexis.

Adult↗
PubMed1998

Relationship between lens and capsular bag size.

PURPOSE: To measure the size of the lens and the empty capsular bag and evaluate the relationship between them. SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. METHODS: In 46 eye-bank eyes, the equatorial diameter of the lens was measured after a corneoscleral button and the iris were removed. Empty capsular bag diameter was measured after extracapsular cataract extraction through an intact capsulorhexis. RESULTS: Mean lens size was 10.20 mm +/- 0.38 (SD) and mean capsular bag size, 10.38 +/- 0.35 mm. The difference between the size of the lens and that of the empty capsular bag varied from 0 to 0.50 mm (mean 0.20 +/- 0.17 mm). Lenses measuring less than 10.25 mm in diameter showed an increase of 0.25 mm while lenses larger than 10.25 mm showed an increase of 0.09 mm. CONCLUSION: Lens size was larger in our population than in previous studies. The increase in the empty capsular bag size was related to initial lens size.

Aged↗
PubMed1997

Primary posterior capsulorhexis with and without anterior vitrectomy in congenital cataracts.

PURPOSE: To determine whether anterior vitrectomy is necessary along with primary posterior capsulorhexis in children less than 5 years of age with congenital cataracts. SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. METHOD: This prospective study comprised 18 eyes of 16 children whose mean age was 2.3 years (range 3 months to 5 years). Primary posterior continuous curvilinear capsulorhexis (PCCC) and posterior chamber intraocular lens (IOL) implantation were performed in all eyes. No vitrectomy was done in 8 eyes (Group 1); an anterior vitrectomy was performed in 10 eyes (Group 2). Optic capture through the posterior capsule was achieved in 3 eyes in Group 1 and in 5 eyes in Group 2. Average follow-up was 13.3 months. RESULTS: Five eyes (62.5%) in Group 1 needed secondary pars plana vitrectomy because the visual axis was obscured; no eye in Group 2 needed a secondary procedure. Four Group 1 eyes developed significant complications (updrawn pupil, decentration, occlusio pupillae, transient glaucoma). While no Group 2 eye developed a serious complication, some degree of pigment dispersion was noted in all the eyes. CONCLUSION: The results suggest that anterior vitrectomy is desirable along with primary PCCC in children younger than 5 years with congenital cataracts.

Aphakia, Postcataract↗
PubMed1997

Enlarging the capsulorhexis.

We describe a method to enlarge an initial small capsulorhexis using an iris spatula and cystotome needle. The iris spatula is placed underneath the anterior capsulorhexis margin; the spatula supports the anterior capsule and protects the posterior capsule. A gentle touch on the spatula by the cystotome needle generates a break in the continuity. This is done prior to intraocular lens implantation with the capsular bag and anterior chamber filled with viscoelastic.

Anterior Chamber↗
PubMed1997

Functional morphology of the spinal canal after endplate, wedge, and burst fractures.

Changes in the canal diameter during physiological motions are important considerations in the treatment of patients who have a burst fracture with the presence of bony fragments, but without neurologic deficit. In this in vitro study, the changes in the soft-canal diameter of the thoracolumbar region, when intact and after different fractures, was investigated under several different loading conditions. The soft-canal diameter was clearly identified on the lateral radiographs by attaching a series of steel balls to the posterior longitudinal ligament and ligamentum flavum in the midsagittal plane. Endplate, wedge, and burst fractures were produced incrementally in 19 three-vertebrae human cadaveric spine specimens by high-speed impacts. After each injury, a series of functional lateral radiographs were taken. The minimal canal diameter (MCD) was obtained by digitizing the images of the steel balls on radiographs using a custom-designed computer program. In the intact specimens, the MCD at the disc level changed significantly in flexion, extension, and compression, when compared with the MCD in the unloaded neutral position. However, the changes were small. The MCD after endplate and wedge fractures changed in a similar way. However, after the burst fracture, the MCD at the bone fragment level increased remarkably by a distraction force. It also significantly improved by an anterior shear force in comparison to the corresponding MCD in the neutral position. However, this change was smaller than the change due to the distraction force.

Biomechanical Phenomena↗
PubMed1995

Dynamic canal encroachment during thoracolumbar burst fractures.

In the burst fractures seen clinically, often poor correlation exists between the neurological deficit and the canal encroachment measured on post-trauma radiographic images. The purpose of the present study was to determine whether the dynamic canal encroachment during the trauma is greater than the static canal encroachment posttrauma. We successfully produced burst fractures in nine of 15 fresh human cadaveric thoracolumbar spine specimens (T11-L1). The specimens were incrementally impacted in a high-speed trauma apparatus until fracture occurred. During the trauma, dynamic canal encroachments were measured using three specially designed transducers placed in the canal at the levels of the superior end-plates of the T12 and L1 and the T12/L1 disk. After the trauma, residual static spinal canal encroachments were measured from the radiographs of the specimens that were prepared with 1.6-mm diameter steel balls lining the canal in the midsagittal plane. We found that the average canal diameter was 16.6 +/- 1.3 mm and the static canal encroachment was 18.0% of the canal diameter. The corresponding dynamic canal encroachment was 33.3%. Thus, the dynamic canal encroachment was 85% more than the static measurement. The clinical significance of this study lies in providing awareness to the clinician that the dynamic canal encroachment is significantly greater than the static canal encroachment seen on posttrauma radiographs or computed tomography scans. The finding may also explain the clinical observation of poor correlation between the canal encroachment measured radiographically and the neurological deficit.

Adult↗
PubMed1995

Capsulorhexis: its safe limits.

We undertook this study to determine the safe limits of capsulorhexis during nucleus expression in 40 eyes of patients undergoing extracapsular cataract extraction (ECCE) with a posterior chamber intraocular lens (PCIOL) implantation and in 30 cadaver eyes. In group I (patient eyes), capsulorhexis of 4.5 to 7.5 mm was performed and the nucleus was expressed by hydrodissection. The nuclei measured 4.5 to 9.0 mm. One relaxing incision at 12 o'clock position had to be placed in 9 patients. In group II (cadaver eyes), continuous curvilinear capsulotomies of 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5 mm were made in 5 eyes each. No relaxing incisions were placed. In both the groups, nuclei of all sizes could be safely delivered through intact capsulotomies measuring 5.5 mm or more. In two patient eyes, posterior capsule rupture occurred with rhexis measuring 4.5 and 5.0 mm, respectively. In the cadaver eyes, intracapsular extraction occurred in 4 eyes with rhexis measuring 5.0 mm or less. We conclude that a rhexis less than 5.5 mm is not safe for nucleus delivery during ECCE.

Adult↗
PubMed1994

On the understanding of clinical instability.

STUDY DESIGN: Three-dimensional flexibility changes due to the application of an external fixator at C4-C5 were studied in cervical spine specimens. OBJECTIVES: To evaluate the biomechanical effects of applying a cervical external fixator to a patient using an in vitro model. SUMMARY OF BACKGROUND DATA: There is controversy regarding the relationship between the changes in spinal motion and clinical instability. METHODS: Using fresh cadaveric C4-C7 specimens, multidirectional flexibility was measured at all vertebral levels, before and after the fixator application at C4-C5, C5-C6, and C4-C6. RESULTS: The average ranges of motion for flexion, extension, lateral bending, and axial rotation were 8.3 degrees, 7.2 degrees, 5.3 degrees, and 5.6 degrees, which decreased by 40%, 27%, 32%, and 58%, respectively, because of the fixator application. The corresponding neutral zones were 3.4 degrees, 3.4 degrees, 3.0 degrees, and 2.0 degrees, which decreased by 76%, 76%, 54% and 69%, respectively. The decreases with the fixation at C4-C5 were similar to those for fixation at C5-C6. CONCLUSIONS: This in vitro study documented that the application of an external fixator to the cervical spine decreases the intervertebral motion in general, and decreases flexion, extension and torsional neutral zones in particular. The findings help explain the clinical instability of the spine and support the hypothesis that the neutral zone is more closely associated with the clinical instability than is the range of motion.

Adult↗
PubMed1994

Disc degeneration affects the multidirectional flexibility of the lumbar spine.

STUDY DESIGN: An in vitro biomechanical investigation using human lumbar cadaveric spine specimens was undertaken to determine any relationship between intervertebral disc degeneration and nonlinear multidirectional spinal flexibility. SUMMARY OF BACKGROUND DATA: Previous clinical and biomechanical studies have not established conclusively such a relationship. METHODS: Forty-seven discs from 12 whole lumbar spine specimens were studied under the application of flexion-extension, axial rotation, and lateral bending pure moments. Three flexibility parameters were defined (neutral zone (NZ), range of motion (ROM), and neutral zone ratio (NZR = NZ/ROM)) and correlated with the macroscopic and radiographic degeneration. RESULTS AND CONCLUSIONS: In flexion-extension, the ROM decreased and NZR increased with degeneration. In axial rotation, NZ and NZR increased with degeneration. In lateral bending, the ROM significantly decreased and the NZR increased with degeneration. In all three loading directions, the NZR increased, indicating greater joint laxity with degeneration.

Adult↗