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Biomedical subjects

J T Thompson

Publications and source records attributed to J T Thompson.

At least 91 records · Page 5Linked to original sources
PubMed1987

Vitrectomy for progressive proliferative diabetic retinopathy.

We analyzed the results of 105 diabetic vitrectomy cases. The vitrectomies were performed for progressive fibrovascular proliferation that caused epiretinal membranes, vitreopapillary traction, florid neovascularization, or subhyaloid hemorrhage, with or without substantial preoperative visual loss. Eyes with inactive retinal neovascularization, dense vitreous hemorrhage, traction retinal detachment involving the macula, or combined traction and rhegmatogenous retinal detachment were excluded. Seventy-four eyes (70%) had improved final vision. The final vision was unchanged in eight eyes (8%) and was worse in 23 eyes (22%). Factors associated with a favorable visual prognosis included the following: age of 40 years or less, preoperative visual acuity of 5/200 or better, absence of preoperative iris neovascularization, preoperative panretinal photocoagulation, and absence of an iatrogenic retinal break.

Adult↗
PubMed1987

Results and prognostic factors in vitrectomy for diabetic traction retinal detachment of the macula.

The level of final visual acuity results and the prognostic factors predictive of the level were analyzed in 360 eyes that had pars plana vitrectomy for diabetic traction retinal detachment of the macula. Fifty-nine percent of the eyes had improved visual acuity on final examination. The percentage of eyes that achieved a final visual acuity of 20/100 or better and the percentage that achieved 5/200 or better increased from 21% to 36% and from 57% to 72%, respectively, during the study. Preoperative factors associated with a favorable visual prognosis were a visual acuity of 5/200 or better, the absence of iris neovascularization, a clear crystalline lens or only minimal cataract formation, clear media or only mild vitreous hemorrhage, panretinal photocoagulation of at least one fourth of the retina, and the absence of severe preoperative retinal neovascularization. Intraoperative factors associated with a favorable visual prognosis include the avoidance of performing a lensectomy, the absence of iatrogenic retinal breaks, and the avoidance of using intraocular gas bubbles.

Adolescent↗
PubMed1987

Results and prognostic factors in vitrectomy for diabetic traction-rhegmatogenous retinal detachment.

The results of pars plana vitrectomy for diabetic traction-rhegmatogenous retinal detachment were analyzed in 172 eyes, and the factors associated with a final visual acuity of 5/200 or better were identified. Forty-eight percent of eyes had improved vision on final examination. The proportion of eyes with a final visual acuity of 20/100 or better and 5/200 or better remained virtually the same during the ten-year study interval. Preoperative factors associated with a visual acuity of 5/200 or better were a preoperative visual acuity of 5/200 or better, the absence of iris neovascularization, and the absence of retinal detachment involving the macula. The intraoperative factor associated with a final visual acuity of 5/200 or better was the absence of iatrogenic retinal breaks.

Adult↗
PubMed1987

Corneal astigmatic changes after pars plana vitrectomy.

The authors prospectively studied 67 eyes of 64 patients undergoing pars plana vitrectomy without a scleral buckle to determine the effect of surgery on postoperative corneal curvature. An average of 1 D of against-the-rule astigmatism was induced in the immediate postoperative period. This astigmatic change spontaneously regressed to less than 0.15 D by the 7th postoperative week. Pars plana vitrectomy does not induce clinically significant corneal astigmatism.

Astigmatism↗
PubMed1986

Effect of scleral buckling on vector forces caused by epiretinal membranes.

Epiretinal membranes exert a perpendicular force on the retina that is directed toward the center of the vitreous cavity and tends to elevate the retina from the retinal pigment epithelium. A scleral buckle changes the eye wall from concave to convex and reverses the direction of the vector force oriented perpendicular to the eye wall. Therefore, when a scleral buckle is used, the force from an epiretinal membrane pulls the retina toward the retinal pigment epithelium instead of causing retinal detachment.

Eye↗
PubMed1986

Results of vitrectomy for proliferative diabetic retinopathy.

The authors treated 1007 eyes with vitrectomy for complications of proliferative diabetic retinopathy. Indications for surgery were: vitreous hemorrhage, 353 eyes (35%); traction retinal detachment, 360 eyes (36%); combined traction-rhegmatogenous retinal detachment, 172 eyes (17%); and other progressive fibrovascular proliferation 122 eyes (12%). During the study period, the frequency of vitreous hemorrhage as an indication for surgery decreased from 42 to 25%, and other progressive fibrovascular proliferation increased from 5 to 22%. The frequency of traction and traction/rhegmatogenous retinal detachments did not change. The results of surgery varied according to the indication. Seventy-nine percent of eyes with vitreous hemorrhage obtained final vision of 5/200 or better. Similar results were obtained in 64% of eyes with traction detachment, 56% of eyes with rhegmatogenous detachment, and 81% of eyes with progressive fibrovascular proliferation. The percentage of eyes achieving final vision of 20/100 or better are as follows: vitreous hemorrhage, 48%; traction detachment, 27%; rhegmatogenous detachment, 24%; and progressive fibrovascular proliferation, 46%. The success rate improved in each anatomic category during the last 3 years of the study.

Diabetic Retinopathy↗
PubMed1986

Endolaser treatment of the ciliary body for uncontrolled glaucoma.

We used vitrectomy and transvitreal endophotocoagulation of the ciliary processes to treat 18 eyes with severe glaucoma that could not be managed successfully by medical therapy and conventional glaucoma surgery. Lensectomy was performed in the two phakic eyes in the series because of cataractous lens changes. A pars plana vitrectomy was done in each eye and a fiberoptic probe used to apply transvitreal blue-green argon laser photocoagulation directly to the ciliary processes. Treatment of more than 180 degrees was necessary for sufficient lowering of the intraocular pressure. Postoperative intraocular pressure was equal to or less than 20 mmHg in 14 of 18 eyes, although nine of the 14 successful cases required postoperative medical therapy. Complications included transient vitreous hemorrhage (2 eyes), transient choroidal detachment (2 eyes), and hypotony (1 eye).

Adolescent↗
PubMed1986

Prognostic factors in vitrectomy for epiretinal membranes of the macula.

A retrospective multivariate analysis of 264 consecutive cases of vitrectomy for removal of epiretinal membranes of the macula was performed. Two main preoperative prognostic factors were identified that were associated with the visual outcome of surgery: (1) the preoperative visual acuity, and (2) the duration of blurred vision before surgery. Discriminant functions constructed using these two factors allowed correct classification of eyes into an outcome group with good visual acuity with a 69% accuracy, and an 80% accuracy in classifying eyes into a group showing significant improvement in the level of visual acuity. Eyes that began with vision better than 20/100 tended to have slightly better postoperative visions than eyes with poorer preoperative visual acuity. However, eyes with worse preoperative vision tended to improve the greatest amount after surgery. Eyes with a longer history of blurred vision had poorer visual acuity after surgery and also less improvement in vision. Other statistically significant prognostic factors were identified; however, they did not appreciably improve the accuracy of the discriminant function in predicting visual outcome.

Adolescent↗
PubMed1986

Prognostic indicators of success and failure in vitrectomy for diabetic retinopathy.

Results of pars plana vitrectomy for complications of diabetic retinopathy were analyzed by logistic regression analysis in 1007 eyes to determine the preoperative and intraoperative factors associated with visual success or failure. Preoperative factors associated with a poorer visual outcome (final visual acuity less than 5/200) include preoperative iris neovascularization, cataract, visual acuity less than 5/200 and traction or rhegmatogenous retinal detachment. Intraoperative factors associated with a greater chance of a poor visual result include use of intravitreal gas or air and creation of an iatrogenic retinal break or detachment. The presence of any one of these factors resulted in a 1.5 to 3.9 times greater risk of a poor final visual result. The regression coefficients may be combined to predict the likelihood of obtaining final acuity greater than or equal to 5/200 in eyes with various preoperative characteristics.

Adolescent↗
PubMed1986

The use of intravitreal thrombin to control hemorrhage during vitrectomy.

The ability of intravitreal bovine thrombin to control intraoperative bleeding was investigated by a prospective double blind study of 28 consecutive patients with vascularized preretinal membranes undergoing vitrectomy for diabetic retinopathy. Addition of thrombin (100 units/ml) to the vitrectomy infusate was associated with a significantly reduced intraocular bleeding time after cutting vascularized membranes. The mean bleeding time without thrombin was 111.5 seconds, compared to 12.3 seconds with intravitreal thrombin (P less than 0.0001). Patients receiving thrombin had less overall bleeding during surgery and less vitreous hemorrhage on the second postoperative day. Intravitreal bovine thrombin was associated with increased postoperative intraocular inflammation in 20% of patients receiving thrombin. This inflammation could be controlled by use of frequent topical steroids.

Animals↗
PubMed1985

Role of lensectomy and posterior capsule in movement of tracers from vitreous to aqueous.

The rate of movement of 20,000- and 70,000-dalton dextran from vitreous to aqueous was determined after extracapsular lensectomy in rabbits with an intact posterior capsule. Dextran was injected into the vitreous, and 3.5 hours later the aqueous concentration of 20,000-dalton dextran was 10.3-fold greater in the aphakic than the phakic eye. The aqueous concentration of the 70,000-dalton dextran was 3.9-fold greater in the aphakic eye after 3.5 hours. Thus, extracapsular lensectomy with an intact posterior capsule increases the rate of movement of 20,000- and 70,000-dalton dextran from the vitreous to the anterior chamber. In addition, the movement of tracers from vitreous to aqueous is increased further when the posterior capsule is opened.

Animals↗
PubMed1985

Volume displacement of scleral buckles.

Indentation of the eye wall by a scleral buckle displaces volume from the vitreous cavity. We developed a mathematical formula to calculate the volume displacement caused by a scleral buckle and verified the accuracy of this mathematical model by performing scleral buckles in 21 cadaver eyes and three eyes undergoing retinal reattachment surgery. A single 5-mm radial sponge of moderate height displaces about 0.2 mL of fluid and a circumferential 2.5-mm-wide band of moderate height displaces about 0.5 mL of fluid. Larger circumferential tires of 7- to 10-mm width displace 1.1 to 1.8 mL of fluid, depending on the height and configuration of the scleral buckle. A 7- to 10-mm-wide circumferential scleral buckle with a buckle height of 4 mm may displace up to 45% of the volume of the vitreous cavity. This volume displacement should be considered when injecting expansile gases or pharmacologic agents into the vitreous cavity.

Body Fluids↗
PubMed1985

Ophthalmic prisms. Deviant behavior at near.

Unpredictability in strabismus surgery results may be due in part to errors in the measurement of strabismic deviations. Whenever measuring strabismic deviations with a fixation target at near, the distance from the eye to the prism must be taken into account to measure the true deviation. For example, when a prism is held 4 cm from the cornea of an eye deviating 50 prism diopters from a fixation target at 33 cm, the measured deviation is 62 prism diopters. The required prism power needed to neutralize a deviation with fixation at near will be increased, the further the prism is held from the cornea. This may lead to surgical overcorrections if the surgery is based on the near measurement. The deviation neutralized by a prism held in any angular position, the effect of prism measurements at near, and the measurement of deviations over Fresnel prisms can be calculated and the appropriate corrections made.

Humans↗
PubMed1984

Effect of lensectomy on the movement of tracers from vitreous to aqueous.

To investigate the effect of extracapsular lensectomy with posterior capsulotomy, 20,000- and 70,000-dalton dextran was injected into the vitreous of rabbits. The concentration of the 20,000-dalton dextran in the aqueous of aphakic eyes was 14-fold greater than in phakic eyes 3.5 hours after injection of dextran into the vitreous. The aqueous concentration of the 70,000-dalton dextran was four times greater in aphakic eyes after 3.5 hours. The aqueous concentration of a 20,000-dalton dextran in phakic and aphakic eyes became equal between 15.5 and 22.0 hours after injection. Thus, extracapsular lensectomy with posterior capsulotomy increased the rate of movement of a single bolus of both 20,000- and 70,000-dalton dextran preparations from the vitreous to the anterior chamber.

Animals↗
PubMed1984

A new posterior chamber intraocular lens formula for axial myopes.

The accuracy of prediction of postoperative refractive error was evaluated in 175 patients with extracapsular cataract extraction and a Shearing-style posterior chamber intraocular lens. The Binkhorst, Colenbrander - Hoffer and SRK formulas were all less accurate in patients with an axial length greater than or equal to 24.5 mm. The standard error of the estimates of the Binkhorst formula was 1.2 diopters, the Colenbrander - Hoffer formula 1.18 diopters and the SRK formula 0.90 diopters. A new intraocular-lens formula for axial myopes was derived by polynomial regression analysis with a standard error of the estimate of 0.85 diopters. This new formula was accurate within 1 diopter in 79% of axial myopes compared to 71% for the SRK , 66% for the Colenbrander - Hoffer and 64% for the Binkhorst formulas. Regression analysis of a surgeon's own patient data can further improve the accuracy of prediction of the post-operative refraction.

Cataract Extraction↗
PubMed1983

Ophthalmic prisms. Measurement errors and how to minimize them.

Variable results of strabismus surgery may be due in part to errors in prism measurement. The amount of deviation neutralized by an ophthalmic prism is variable depending on how the prism is held. For example, a 40 delta glass prism with the posterior face held in the frontal plane gives only 32 delta of effect. Glass prisms are calibrated for use in the Prentice position. Plastic prisms are calibrated for use in the frontal plane position. Surprisingly large errors in prism measurement are produced when adding a small prism to a large prism. For example, adding a 5 delta glass prism to a 40 delta glass prism gives not 45 delta of effect, but 59 delta. This error can be minimized but not eliminated by holding one prism in front of each eye. The error can also be calculated so that the appropriate correction can be made.

Calibration↗