Biomedical subjects

A H Tarkkanen

Publications and source records attributed to A H Tarkkanen.

4 recordsLinked to original sources

PubMed2001

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.

Adult↗

PubMed2000

Confocal microscopy of a patient with irregular astigmatism after LASIK reoperations and relaxation incisions.

PURPOSE: Laser-assisted in situ keratomileusis (LASIK) is widely used for correcting refractive errors. If the predicted refractive result is not achieved after the first operation, a re-operation can be performed by ablating more stromal tissue after reopening the flap. The goal of this study was to analyze, by using in vivo confocal microscopy, the morphologic changes associated with repeated LASIKs. METHODS: Clinical examination, computed corneal topography, and real-time in vivo confocal microscopy were performed on both eyes of a 50-year-old patient with induced irregular astigmatism leading to decreased best-corrected vision in the left eye after LASIK. The left cornea had been operated on 5 times (LASIK with two reoperations followed by two relaxing incisions), and the right cornea twice (LASIK with one reoperation). RESULTS: Microfolds at the level of the Bowman's layer and highly reflective particles at the flap interface were observed in both corneas. The subbasal nerve plexus was severed in the left eye. In addition, we identified epithelial material in the flap margin and inside one of the two relaxing incisions placed inferotemporally. CONCLUSION: Repeated LASIKs may stretch the flap and result in microfolding at the Bowman's layer. This and deposition of particles in the flap interface may increase with the number of reoperations, challenging the healing response. Microfolding and occurrence of foreign material in the interface may add to the irregular astigmatism and poor visual outcome after LASIK. Clinical in vivo confocal microscopy offers new possibilities for the assessment of ultrastructural changes after corneal refractive surgery.

Astigmatism↗

PubMed1986

Exfoliation syndrome.

The exfoliation syndrome has now been recognised all over the world and even in such ethnic groups as the Skolt Lapps, Navajo Indians, Australian aborigines and all major tribes of the South African Bantu. The prevalence appears rather all major tribes of the South African Bantu. The prevalence appears rather similar in those countries where population-based surveys have been conducted. The exfoliation syndrome is age-dependent. In Caucasians the prevalence is low before the age of 60 years, increasing steadily to about 8 per cent in the group aged 80 to 90 years. However, the Bantus show a 6.4 per cent prevalence in the age group 30 to 39 years. In population-corrected surveys the females show a higher prevalence of the syndrome than do the males. Familial occurrence of exfoliation and population genetics have suggested an autosomal dominant mode of heredity. Suggestions of differences in prevalence of the exfoliation syndrome in different countries and even in different areas of the same country call for further population-based even in different areas of the same country call for further population-based surveys. Recognition of exfoliation is clinically of paramount importance as 20 percent of exfoliation patients show abnormalities of intraocular pressure. Poor pupillary dilatation, fragile zonular fibres and 2 per cent lens displacement may induce difficulties in extracapsular cataract surgery with posterior chamber lens implantation. Ciliary sulcus fixation of intraocular lenses with large diameter of the haptics is recommended.

Adult↗

PubMedDate not supplied

Changes in visual acuity and refraction in the exfoliation syndrome. A five-year follow-up study.

PURPOSE: To examine changes in visual acuity (VA) and refraction in non-glaucomatous patients with unilateral exfoliation syndrome (EXS). METHODS: The best corrected values for VA (Snellen acuity cards) subjectively adjusted for refraction, and IOP were measured, and the development of lens opacities was examined in 46 non-glaucomatous patients with unilateral EXS. RESULTS: After five years the rate of conversion to bilateral exfoliation was 22% and to exfoliative glaucoma 30%. There was a significant decrease in VA in the exfoliative (E) eyes (median; QI, QIII, range: 1; 0.8, 1, 0.4-1.3 vs. 0.55; 0.4, 1, 0.05-1.4, p<0.0001) and the fellow, initially non-exfoliative (NE), eyes (1; 0.9, 1, 0.3-1.3 vs. 0.7; 0.5, 0.9, 0.1-1.4, p<0.0001) and a significant myopic change in refraction in the E eyes (+1.02 +/- 2.48 vs. +0.11 +/- 3.06, p=0.0001) and the NE eyes (+0.99 +/- 2.25 vs. +0.43 +/- 2.55 D, p<0.01). At study entry the difference in refraction between the fellow eyes (refraction in the NE eye--refraction in the E eye) was -0.27 +/- 1.00D. After five years it was +0.32 +/- 1.44 (p 0.016), reflecting greater myopic changes in the E eyes. The main type of lens opacification was nuclear sclerosis. CONCLUSIONS: In five years, significant decreases in VA and myopic shifts in refraction occurred in the E and fellow eyes. The E eyes showed significantly greater myopic changes than the fellow eyes; the cause was clearly nuclear sclerosis, which must be taken into account in the long-term management of patients with EXS.

Age Distribution↗