Corneal topography after excimer laser photorefractive keratectomy for myopia

BACKGROUND

This study was performed to assess and correlate the changes in central corneal power with the changes in manifest refraction after myopic photorefractive keratectomy (PRK) and to measure ablation zone centration.

METHODS

Fourteen patients had computerized videokeratography and manifest refraction performed preoperatively, and than 1, 2, 3, 4, 6, and 12 months after photorefractive keratectomy.

RESULTS

There was a significant association (r = -0.9; p < 0.0001) between changes in manifest refraction and changes in central corneal power at the 12-month postoperative examination; however, a mean difference of 1.1 D was seen between the two readings. The mean decentration of the ablation zone was 0.47 +/- 0.26 mm (range, 0.08 to 1.05 mm: 0 to 0.49 mm, six patients; 0.50 to 0.99 mm, seven patients; and 1.00 to 1.50 mm, one patient).

CONCLUSIONS

Corneal power-as measured by videokeratography-is not an accurate predictor of manifest refraction, although the two parameters did demonstrate good correlation. Centration of ablations was comparable to previous studies.

Central and peripheral endothelial cell changes after excimer laser photorefractive keratectomy for myopia

OBJECTIVE

To investigate changes in the human corneal endothelium after photorefractive keratectomy for treatment of myopia.

DESIGN

Specular microscopy of the central, paracentral, and peripheral zones of the corneas of 14 patients (12 of whom were previous contact lens wearers) was performed preoperatively and at 1, 2, 3, 6, and 12 months after photorefractive keratectomy. The corneal endothelial cell density, coefficient of variation (CV) of the endothelial cell area, and percentage of hexagonal cells were assessed at each examination.

RESULTS

The central endothelial cell density was increased by 7% during the first 3 postoperative months (P < .05). In contrast, the peripheral cell density declined steadily by 6.9% during the first year (P < .01). The CV of the cell area was decreased in all 3 zones, whereas the percentage of hexagonal cells was increased in the central and paracentral zones (P < .05).

CONCLUSIONS

We observed statistically significant changes in the central and peripheral endothelial cell densities and morphological features that could have resulted from photorefractive keratectomy; however, these changes also may have been explained by the discontinuation of contact lens wear. If such changes are contact lens-related, they could mask the effects of laser-induced damage to the central zone of the endothelium.

Drusen of the optic disc

Although optic disc drusen have been of interest to ophthalmologists for more than 100 years, their etiology and many aspects of their relationship to other clinical conditions remain obscure. They have been clinically observed in 0.3% of the population, although autopsy studies suggest an incidence of 2%. Drusen are seldom accompanied by visual symptoms; however, decreased vision and visual field changes may occur. The historical and epidemiological aspects of drusen are reviewed; clinical and histological features, as well as special diagnostic techniques (ultrasonography and fluorescein angiography) are discussed in detail.

Isolated retinal arterial aneurysms

We observed three patients with isolated retinal arterial aneurysms and obtained a clinicopathologic correlation in one of them. All three were hypertensive and in the sixth or seventh decade of life. Fatty exudates were present around the aneurysms, taking the form of large circinate rings in two cases. Microscopic examination in one case revealed a retinal arterial aneurysm with an extensive fibroglial reaction around it. Dilated capillaries, hemosiderin deposits, and both lipoidal and proteinaceous exudates were found in the adjacent retina. Isolated retinal arterial aneurysms appear to be distinct clinical entity as compared to miliary aneurysms of the cerebral circulation.