Corneal recovery after lasik for high myopia: a 2-year prospective confocal microscopic study.

AIM: To quantify human corneal recovery after moderate to high myopic laser in situ keratomileusis (LASIK) in a 2-year prospective follow-up study. METHODS: Fifteen eyes of 15 patients (mean refraction -10.1 (SD 2.4) D) were examined preoperatively and postoperatively at day 1, 5 days, 2 weeks, 1, 3 and 6 months and 2 years. Biomicroscopy, visual acuity and refraction were examined prior to imaging studies. An in vivo tandem scanning confocal microscope was used to obtain images from the central cornea. Subbasal nerve density was measured as the total length of nerve trunks in confocal image per mm2. Keratocyte density was calculated manually from stromal sublayers. The thickness of the altered keratocyte zone was measured on both sides of the LASIK interface. RESULTS: At the end of the follow-up, all patients had a 20/20 BCVA, and nine of 15 patients were within +/-0.5 D of the intended correction. The total corneal thickness remained unaltered, but epithelial hyperplasia was seen at 2 years. Keratocyte density in the anterior stroma and posterior to the flap interface showed a slight decrease during the follow-up. Subbasal nerve density decreased 82% in 5 days after LASIK. A gradual increase was observed from 2 weeks postoperatively, but even 2 years after the operation the nerve density was only 64% from the preoperative values. CONCLUSIONS: Subbasal nerve fibre density shows a gradual recovery throughout the follow-up. However, only three subjects showed totally regenerated subbasal nerve fibres at 2 years. This may correlate with the observed decrease in the density of the most anterior keratocytes. Corneal remodelling seemed to continue for at least 2 years.

Corneal morphology and sensitivity in lattice dystrophy type II (familial amyloidosis, Finnish type).

PURPOSE: To describe the corneal abnormalities and to measure different modalities of corneal sensitivity in corneal lattice dystrophy type II (familial amyloidosis, Finnish type, also known as gelsolin-related amyloidosis and originally as Meretoja syndrome). METHODS: Twenty eyes of 20 patients were examined by in vivo confocal microscopy and noncontact gas esthesiometry. RESULTS: Pleomorphism of, and dense deposits between or posterior to, the basal epithelial cells were frequently observed, as well as a reduction of long nerve fiber bundles in the subbasal nerve plexus. The anterior stroma was altered in most cases, with fibrosis and abnormal extracellular matrix. In 15 corneas, thick anterior and midstromal filaments, corresponding to lattice lines, and in 11 corneas, thin undulated structures were observed. The average mechanical sensitivity threshold of 12 subjects was increased, and in the remaining 8 subjects there was no response, even to the highest intensity of stimuli used. Three patients did not respond to CO(2), 11 to heat, and 2 to cold, but those patients who responded had normal thresholds. Patients with more long nerve fiber bundles per confocal microscopic image had better mechanical and cold sensitivity than patients with fewer nerve fiber bundles. CONCLUSIONS: Lattice lines seem to be related to amyloid material and not to corneal nerves. However, the subbasal nerve density appears reduced, which results mainly in a decrease in mechanical and, to a lesser extent, thermal sensitivity. The location of stromal filaments and undulated structures changes with increasing age.

Photorefractive keratectomy in ophthalmic residents.

PURPOSE: To find out how ophthalmologists themselves experience the correction of myopia after photorefractive keratectomy. Visuomotor functions were of special interest. METHODS: Four ophthalmology residents and one medical engineer underwent photorefractive keratectomy for myopia. Objective measurements including refraction, corneal topography, perimetry, contrast sensitivity, pattern visual evoked potentials, in vivo confocal microscopy, and a car driving simulator test were performed preoperatively, postoperatively, and at 6 months. Subjective evaluation was reported. RESULTS: Performing ophthalmological examinations and microsurgery without spectacles was easier postoperatively and was appreciated by the four ophthalmology residents. Minimal haze formation, good accuracy, and normal performance in the car driving simulator were also observed. Visual fields, contrast sensitivity, and pattern visual evoked potentials did not show changes. Negative observations included postoperative pain for 2 to 4 days, dry eye symptoms, a period of anisometropia between operations, and hypersensitivity of the lids. CONCLUSIONS: The four ophthalmic residents were satisfied with the outcome of their refractive surgery. Low to moderate myopic correction did not affect the objective measurements of high and low contrast sensitivity, pattern visual evoked potentials, or simulated car driving in dark illumination.

Autosomal recessive cornea plana: in vivo corneal morphology and corneal sensitivity.

PURPOSE: Autosomal recessive corneal plana (RCP) is a rare corneal anomaly with unknown pathogenesis and a high incidence in Finland. The aim was to examine corneal sensitivity and the morphology of different corneal layers and subbasal nerves in RCP patients. METHODS: Three patients with a diagnosed autosomal recessive cornea plana were examined. Corneal sensitivity to different modalities of stimulation was tested in four corneas using noncontact esthesiometry. Tissue morphology of three corneas was evaluated, and in two corneas thickness of corneal layers was measured using in vivo confocal microscopy. RESULTS: Corneas of RCP patients appear to have mechanosensory, polymodal, and cold-sensitive nerve terminals. RCP patients had normal sensation thresholds for chemical, heat, and cold stimulation but a high threshold for mechanical stimulation. Their capacity to discriminate increasing intensities of stimulus was reduced, except for cold stimuli. Thickness of the epithelial layer was reduced, whereas total corneal and stromal thicknesses were slightly reduced or close to normal values. In all cases Bowman's layer was absent. Subbasal nerves had abnormal branching patterns. The arrangement of anterior keratocytes was altered, showing clustered and irregularly shaped nuclei. Increased backscattering of light in confocal microscopy through focusing (CMTF) profiles was observed throughout the stroma. Epithelial and endothelial cells appeared to be regular in shape. CONCLUSIONS: The present study revealed qualitative and quantitative alterations in corneal sensitivity, cellular morphology, and the thickness of corneal layers in RCP patients.