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T V Cravy

Publications and source records attributed to T V Cravy.

10 recordsLinked to original sources
PubMed1992

Calculating the surgically induced refractive change following ocular surgery.

Calculating the surgically induced refractive change following ocular surgery is important for evaluating the results of keratore-fractive procedures, smaller incisions and various wound closures for cataract surgery, and the effect of suturing techniques and suture removal following corneal transplant surgery. We present a ten-step method of calculating the spherical- and cylindrical-induced refractive change in a manner suitable for a programmable calculator or personal computer. Several applications are given including (1) adding the overrefraction to the spectacle correction, (2) determining the surgically induced refractive change from the preoperative and postoperative refractions, (3) determining the surgically induced refractive change from the K-readings, (4) rotating axes, (5) determining the power at meridians oblique to the principal meridians of a spherocylinder, (6) determining the coupling ratio, and (7) averaging axes. Standard methods for calculating and reporting aggregate results are also given.

Astigmatism↗
PubMed1991

Natural history of corneal astigmatism after cataract surgery.

Little information on the natural course of corneal astigmatism following cataract surgery exists. We report a prospective, computerized analysis of postoperative astigmatism, based on keratometry measurements, of 137 cases of extracapsular cataract extraction with intraocular lens implantation performed by one surgeon. No sutures were cut postoperatively. Surgery induced 1.44 diopters (D) of with-the-rule astigmatism at one month, which declined at a rate of 0.77 D and 0.35 D per month for the next two months, respectively, with a more gradual decline thereafter. The mean surgically induced astigmatism at the last postoperative visit ranged from 0.29 D at six months (minimum follow-up) to 1.23 D at 48 months; both were against-the-rule. Mean follow-up was 28.92 months. These findings may be technique specific and suggest that (1) corneal curvature continues to change slowly even two to four years postoperatively; (2) most patients develop against-the-rule astigmatism, thus more with-the-rule astigmatism is desirable in the early postoperative period; (3) selective suture removal is necessary only when significantly more than 3.00 D of surgically induced with-the-rule astigmatism is present.

Aged↗
PubMed1991

Routine use of a lateral approach to cataract extraction to achieve rapid and sustained stabilization of postoperative astigmatism.

After observing that lateral under-riding scleral pocket incisions and closures decayed very little and required full correction on the table to achieve the desired reduction in astigmatism, I began performing routine lateral approaches to planned extracapsular cataract extraction (ECCE). The result was an improvement in early and prolonged stabilization of keratometric astigmatism. This improvement was statistically significant when compared with the identical surgery performed in the vertical meridian. Using a 6.5 mm scleral pocket incision and the same suture material and closure technique, I found that the results of phacoemulsification via vertical and lateral approaches were not statistically different from the planned ECCE via lateral approach. Scleral pocket incisions and modified shoelace closures with 11-0 polyester suture were used in all cases; no suture removal was performed. The early visual recovery with planned ECCE via lateral approach was equivalent to that with phacoemulsification but did not require the expensive instrumentation or the "phaco learning curve." The minimal and stable postoperative astigmatism, along with early and sustained visual recovery possible with ECCE via lateral approach, may reduce the potential benefit of mini-incision and foldable intraocular lens surgery.

Aged↗
PubMed1989

Using the intraocular lens refraction factor to improve refractive prediction accuracy.

In 1984, I reported that the refraction constant used in the SRK formula was too high and should have a value of 1.0 or less. The term refraction factor (RF) was adopted to replace the refraction constant which was under scrutiny. The current study was done in four phases. Phase 1 showed improved refraction prediction accuracy for sulcus-fixated intraocular lenses (IOLs) when an RF of less than or equal to 1.0 was used instead of a fixed RF of 1.25. The anterior chamber IOLs had worse results under the same conditions. Phase 2 retrospectively determined computer optimized and matched A constant and RF pairs for anterior chamber, sulcus-fixated, and bag-fixated IOLs for all axial lengths (AL), short (AL less than or equal to 21.5 mm), long (AL greater than or equal to 24.5 mm), and mid-range (21.5 mm less than AL less than 24.5 mm). Phase 3 demonstrated a dramatic improvement in the refraction prediction accuracy when the matched pairs according to AL were used in 61 consecutive patients receiving Jaffe, bag-fixated IOLs. Phase 4 demonstrated good results in 15 consecutive patients, using the RF found for Jaffe IOLs in calculations for a meniscus-type, bag-fixated IOL, with which I had no experience. I determined that the longer the eye, the smaller the RF, for any given IOL position in the eye. The data indicated that different RFs should be used for different IOL locations within the eye. The more forward the IOL, the larger the RF.(ABSTRACT TRUNCATED AT 250 WORDS)

Electronic Data Processing↗
PubMed1989

Long-term corneal astigmatism related to selected elastic, monofilament, nonabsorbable sutures.

The long-term decay of surgically induced corneal astigmatism following planned extracapsular cataract extraction has been studied in 395 patients who had limbal or scleral pocket incisions of 60 to 140 degrees. Limbal incisions were closed with a full-thickness shoelace closure; scleral pocket incisions, with a new, modified shoelace closure. Suture material was 10-0 nylon, 9-0 nylon, 10-0 polypropylene (Prolene), and 10-0 polyester (Mersilene). The nylon sutures demonstrated clinically significant hydrolysis beginning at five months (10-0) and 12 months (9-0). Because of the adverse hydrolytic effects, 10-0 nylon was eliminated from the scleral pocket closure group. The hydrolysis of 9-0 nylon caused excessive late astigmatic changes in patients who did not heal normally. Prolene and Mersilene showed no tendency toward hydrolysis; however, the elasticity of Prolene produced more against-the-rule change in astigmatism than desired even though it was stable over the long run. I stopped using nylon sutures in cataract (and keratoplasty) wound closures and switched to routine use of Mersilene.

Adult↗
PubMed1980

A modified suture placement technique to avoid suture drag or "cheese wire" effect.

A modified technique is described for microsurgical suture placement, irrespective of the closure technique, to prevent suture drag and loosening of the suture following postoperative wound edema. Fine, elastic, non-absorbable sutures which loosen as a result of suture drag or "cheese wiring" have no more reliability than do absorbable or silk sutures. Predictable and reproducible results of suture placement are necessary to allow the surgeon to effectively use the operating keratometer in the control and modification of corneal astigmatism following anterior segment surgery.

Astigmatism↗
PubMed1979

Calculation of the change in corneal astigmatism following cataract extraction.

Obtaining a minimal amount of postoperative astigmatism following cataract surgery is becoming increasingly important. One aspect of the patient's surgery which should not be overlooked is the preoperative keratometry which provides a basis for preoperative planning of surgical technique to be used and a point of reference for determining the amount of change in astigmatism produced by the surgery. Analysis of the surgically induced change in astigmatism using the calculations described in this paper will allow the surgeon to evaluate his own techniques and to maximize his potential for obtaining consistently good postoperative astigmatic results without the need for suture removal. The method presented is based upon concepts in common use in surgical ophthalmology and requires only simple mathematical procedures, familiar to all with a background in algebra and trigonometry.

Astigmatism↗