Results of laser in situ keratomileusis in different degrees of myopia.

PURPOSE: This study aimed to analyze the results of laser in situ keratomileusis (LASIK) in different degrees of myopia. MATERIAL AND METHODS: Three hundred consecutive eyes were divided into 4 groups according to their degree of preoperative myopia. Group I was between -3 and -6 diopters (D) (28 eyes), low myopia. Group II was between -6.25 and -10 D (138 eyes), moderate myopia. Group III was between -10.25 and -15 D (91 eyes), high myopia. Group IV was between -15.25 and -25.50 D (43 eyes), extremely high myopia. Patients were observed for 6 to 25 months. RESULTS: For group I, the preoperative spherical equivalent was -5.12 D +/- 0.81 standard deviation (SD), corrected visual acuity was 0.88 +/- 0.14 (SD), and keratometry was 44.09 D +/- 1.65 (SD). At the last check-up, the spherical equivalent was -0.42 D +/- 0.98 (SD), corrected visual acuity was 0.89 +/- 0.15 (SD), keratometry was 39.11 D +/- 1.61 (SD). For group II, preoperative spherical equivalent was -8.33 D +/- 1.24 (SD), corrected visual acuity was 0.72 +/- 0.22 (SD), keratometry was 44.34 D +/- 1.64 (SD). At last check-up, the spherical equivalent was -0.19 D +/- 1.22 (SD), corrected visual acuity was 0.76 +/- 0.17 (SD), keratometry was 37.56 D +/- 1.90 (SD). For group III, the preoperative spherical equivalent was -12.37 D +/- 1.49 (SD), corrected visual acuity was 0.58 +/- 0.23 (SD), and keratometry was 44.06 D +/- 1.63 (SD). At last check-up, spherical equivalent was -0.55 D +/- 1.63 (SD), corrected visual acuity was 0.61 +/- 0.18 (SD), and keratometry was 35.88 D +/- 2.18 (SD). For group IV, the preoperative spherical equivalent was -19.04 +/- 2.82 (SD), corrected visual acuity was 0.37 +/- 0.17 (SD), and keratometry was 44.02 D +/- 1.30 (SD). At last check-up, spherical equivalent was -1.49 D +/- 1.54 (SD), corrected visual acuity was 0.44 +/- 0.18 (SD), and keratometry was 33.94 D +/- 2.54 (SD). CONCLUSION: With some exceptions, LASIK results generally are acceptable and stable. Nevertheless, the scatter of some cases shows that there is room for improvement, even in the most sophisticated excimer software. The high regression of group I proves the need to sample multizone software to determine whether stability is improved. Although visual results are better in patients with lower myopia, the patients whose eyes had higher ametropia more often showed improvement in their visual acuity. This may be because of the greater postoperative size of the image on the macula.

Excimer laser in situ keratomileusis for myopia.

Excimer laser in situ keratomileusis was done in 97 eyes of 59 patients to correct moderate and high myopia. Mean follow-up was 150 days. Mean preoperative myopia was -10.75 diopters (D). Mean reduction in myopia was -11.281 D (106.98%) at 1 month and -10.37D (98.417%) at 3 months. At 1-month, 41 eyes (42.27%) had a refraction within -1.00 D and 70 teeyes (72.16%) had a refraction within -2.00 D. At 3 months, 41 eyes (46.59% of 88 eyes) had a refraction within -1.00 D and 66 eyes (75% of 88 eyes) had a refraction within -2.00 D. Mean preoperative keratometric power was 44.00 D; mean postoperative keratometric power was 36.39 D. The keratometric change in power was 7.61 D. Preoperatively, 73 eyes (75%) had a spectacle corrected visual acuity of 20/40 or better; postoperatively, 64 eyes (65.63%) at 1 month and 75 eyes (77.01%) at 3 months reached 20/40 or better. The uncorrected visual acuity was 20/40 or better in 33 eyes (33.72%) at 1 month and in 49 eyes (49.96%) at 3 months. Mean ablation zone diameter was 4.92 mm. Astigmatism was treated separately in 10 eyes. Complications included optical zone decentration (3 eyes with more than 1 mm, epithelial implantation (1 eye), incomplete resection of the disc (2 eyes), severe hypotension, and irregular astigmatism (1 eye).

Problems of inference from hypothesis-generating studies on lung cancer and occupation based on routine hospital records.

This paper discusses inference from hypothesis-generating studies on occupational risks for lung cancer based on routine hospital records. A hospital-based case-control study on 567 male lung cancer patients and 906 controls provided a practical example. Among possible causes of bias, the effects of poor detail in the occupational information, of a large proportion of exclusions due to incomplete information, of cardiovascular diseases as the prevalent diagnosis among controls, of selecting cases and controls from different hospitals with likely differences in referring areas, and the problem of multiple comparisons are highlighted. Significant excess lung cancer risks were found for farmers, miners, crushers, stonemasons and cement plant workers, and stock handlers and stevedores. Positive findings with small numbers of observations are more likely to be artificially generated, but also the precision of more robust risk estimates may be affected. The limits to inference from hypothesis generating case-control studies based upon routine hospital records, such as in the example described, outweigh the advantage of the ready availability of these data-bases.

Glucose-6-phosphate dehydrogenase deficiency and lung cancer: a hospital based case-control study.

A hospital based case-control study was conducted to test the hypothesis of a lower lung cancer risk in G6PD-deficient subjects. Cases were 156 male patients with lung cancer, admitted to "Binaghi" Hospital, Local Health Unit (USL) 20, Cagliari (Italy), between January 1984 and November 1986. Controls were 235 male patients, admitted to the same hospital in the same time period, for diseases other than cancer (all types) and hemolytic anemia. No decrease of the lung cancer risk was found in G6PD-deficient subjects. This result, in line with recent reports in the literature, suggests that the genetic condition of G6PD deficiency does not provide significant protection against the development of lung cancer in humans.

Hexose monophosphate shunt enzymes in lung tumors from normal and glucose-6-phosphate-dehydrogenase-deficient subjects.

Glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate, dehydrogenase the key enzymes of the hexose monophosphate shunt pathway, were measured in both surrounding and tumoral lung tissues from normal and G6PD-deficient subjects. A significant increase of these enzymatic activities in tumoral tissue was found not only in G6PD-normal patients, but also in G6PD-deficient patients with very low or nonmeasurable G6PD activity in both erythrocytes and normal lung tissue.