Biomedical subjects
Publications and source records attributed to K C Nagpal.
The renal calculi are studied by using an X-ray diffractometer for different chemical composition of the stones. A new constituent, alpha-quartz, is confirmed to be present in the renal calculi which is responsible for piezoelectric property of such materials.
Explore the source record for details and available documents.
We performed 400 consecutive pars plana vitrectomies, using the vitrophage. Most patients (68%) showed some degree of visual improvement; only 8% had a decline in visual acuity postoperatively. The major operative complications were controllable bleeding from iris vessels and intravitreal stalks (19%) and retinal tears (2%). No retinal dialysis was noted. The major, early postoperative complications were related to corneal decompensation in 38% of the cases; this persisted beyond two weeks in only 7%. Increased intraocular pressure occurred in 19% and postoperative rubeosis iridis developed in 10% of the diabetic patients. Complications related to rebleeding occurred in 18% of the diabetic patients within the first two weeks, and an additional 9% had late rebleeding. Less frequent complications included one case of endophthalmitis, late retinal detachment in 5%, and phthisis bulbi in 2% of all cases. All complications were considerably more frequent and severe in the diabetic population.
Explore the source record for details and available documents.
Sixty-five patients with hemoglobins AS, SC, and SS were investigated in a masked fashion. We observed a statistically significant positive correlation between the severity of conjunctival sickling signs and the counts of irreversibly sickled cells in each hemoglobinopathy group. We also observed a statistically significant positive correlation between the severity of the conjunctival vasculopathy and the percentage of sickle hemoglobin in the total group of patients with hemoglobins AS, SC, and SS.
With prospective observations we have documented by fluorescein angiography the development of retinal neovascularization in the eyes of patients with sickle cell-hemoglobin C disease (hemoglobin SC). In each patient, arteriolarvenular (AV) anastomoses occurred before the development of neovascular sea fans. To our knowledge, this report constitutes the first such documentation in the literature. New sea fans from AV anastomoses appeared throughout an average interval of 18 months (range, 8 to 36 months) in approximately 21% of young adults with hemoglobin SC. Each year approximately 14% of young patients with hemoglobin SC may develop retinal neovascularization.
Seven patients had sickle cell trait (hemoglobin AS) and vasoproliferative retinopathy. The retinal abnormalities in these seven patients were indistinguishable from those seen in patients with clinically significant sickling hemoglobinopathies (sickle cell-hemoglobin C disease, hemoglobin S-thalassemia disease, and sickle cell anemia). All seven patients also had some evidence of associated systemic disease such as diabetes, syphilis, tuberculosis, or sarcoidosis. In the presence of an associated systemic disease, marked retinopathy can occur in the ordinarily benign condition of sickle cell trait.
Nine patients had white-without-pressure retinal lesions. These lesions were seen in areas of vitreoretinal adhesions. The configuration and location of these lesions changed over variable periods of time. The cause of this pecular migration is unknown, but may be related to separation and re-creation of vitreoretinal adhesions. The migratory nature of white-without-pressure areas has not, to our knowledge, previously been reported in the literature.
Five patients had angioid streaks associated with sickle cell haemoglobinopathy. Other diseases associated with angioid streaks were ruled out, as was elastic tissue degenegation in sickle cell patients. After studying over 350 patients, we believe the incidence of angioid streaks in sickle cell disease to be between 1 and 2 per cent.
A total of 125 consecutive eyes, all registered blind with diabetic vitreous haemorrhage, underwent pars plana vitrectomy with the vitrophage. Sixty-six per cent experienced some improvement in their visual acuity; 24 per cent were unchanged and 10 per cent were worse postoperatively. The major surgical complication was controllable haemorrhage (23 per cent). No retinal dialysis occurred. Significant postoperative complications were transient (71 per cent) and persistent (11 per cent) corneal oedema, early (8 per cent) and late (13 per cent) vitreous haemorrhage, transient (30 per cent) and persistent (6 per cent) rise in intraocular pressure, and rubeosis iridis (5 per cent).
Two children with persistent hyperplastic primary vitreous (PHPV) underwent vitrectomy and lensectomy via the pars plana to remove the fibrovascular stalk. Postoperatively the eyes were quiet, only a slight vitreous haze obscured the fundus view in the immediate postoperative period, and the stumps of the stalks retracted. Early surgical treatment of PHPV may prevent later serious complications.
The posterior pole vasculature of 100 patients with different sickling haemoglobinopathies was studied prospectively over a period of three years. Various abnormalities of the posterior pole vasculature were seen in 29 per cent of the patients. Continuous remodelling of the macular and perimacular vasculature occurred. Visual acuity was variably affected and sometimes remained intact.
The unique problems encountered in sickle patients include the need to remove peripheral vitreous if perfusing sea fans-which can bleed after vitrectomy-are present at the time of surgery. However, peripheral vitrectomy is riskier than central vitrectomy alone. If visualization of the sea fans is sufficient, it is safer to close the sea fans prior to vitrectomy in order to obviate the need for peripheral vitrectomy; then, only central vitrectomy is performed. When sea fans cannot be closed prior to vitrectomy, peripheral vitreous is removed to allow early photocoagulation of the sea fans before they bleed again. Four case presentations illustrate these principles. Vitrectomy relieved severe vitreous traction that complicated retinal detachment in the fifth patient, thereby eliminating the need for a tight encircling structure, which can be poorly tolerated in patients with SC hemoglobin.
Of 45 patients with proliferative sickle retinopathy in stages III, IV, and V, nine patients (eight with hemoglobin SC disease, one with sickle cell thalassemia) showed spontaneous regression (autoinfarction) of retinal sea fans. One mechanism involved in autoinfarction of neovascular tissue is progressive, centripetal retraction of the anterior vascular arcade of the peripheral retina. In addition, vitreous traction on feeder vessels may result in sluggish blood flow and occlusion of these vessels, or may tear the sea fan completely away from its feeder vessels. In view of the many incidences of vitreous hemorrhages that occur in patients with proliferative retinopathy, however, we recommend treatment of neovascularization rather than prolonged observation.
In a prospective study of 38 patients, who were initially selected as being at an early stage of sickling retinopathy, three developed circular black chorio-retinal scars (black sunbursts) during a period of 6 to 24 months. These lesions appear to be the sequelae of intraretinal and subretinal haemorrhage. They occur in the fundus periphery and do not interfere with vision.
Seven black patients had dark brown homogeneous geographical areas of the fundus. Six cases were associated with sickle cell haemoglobinopathies and one was associated with systemic hypertension. These flat lesions were uniform in colour and occurred in the posterior pole or in the midperiphery. They appeared to be transient and often disappeared leaving no residue. The cause is unknown. By analogy with white-without-pressure fundus lesions, we have called these areas dark-without-pressure.
Explore the source record for details and available documents.
Explore the source record for details and available documents.