Wolfgang Radner

Interlacing and cross-angle distribution of collagen lamellae in the human cornea.

Purpose The interlacing and cross angles between the collagen lamellae within the human corneal stroma were studied by means of scanning electron microscopy (SEM). Methods For SEM, cells and noncollagenous extracellular matrix were removed with 10% sodium hydroxide. Transmission electron microscopy (TEM) preparations were performed according to standard procedures. The interlacing of lamellae was studied within the limbal, paracentral, and central regions of five different layers. The cross angles between the longitudinal axes of adjacent lamellae were measured. The distribution of these angles within defined layers and regions was compared. Special attention was paid to the interlacing of the lamellae. Results Lamellae split in an anteroposterior direction as well as horizontally into branches and are interlaced by crossing the fissures between the branches. Smaller lamellae cross through clefts of neighboring lamellae. The cross angles show a high variability of 1°–90°. With the exception of the limbal region of the layer adjacent to Descemets membrane, the distribution of cross angles is similar. A frequent occurrence of cross angles <30° (68%) in this limbal layer can be explained by a pseudo-circular orientation (ligamentum circulare corneae) of the lamellae. Conclusion The present study shows that the three-dimensional organization of the collagen lamellae is characterized by a greater extent of lamellar interlacing than has been assumed until now.

ALTERED ORGANIZATION OF COLLAGEN IN THE APEX OF KERATOCONUS CORNEAS

Purpose: In 15 keratoconus corneas, the three-dimensional arrangement of collagen lamellae was investigated by means of scanning electron microscopy. Methods: Keratoconus corneas without visible scars were obtained during perforating keratoplasty. The noncollagenous matrix of the stroma was removed with sodium hydroxide. Descemet’s membrane was removed mechanically and deeper layers of the stroma were exposed by cutting the tissue tangentially to the corneal surface with an ultramicrotome. The apical and the para-apical regions of keratoconus were compared to the central regions of normal corneas. Results: In the apical regions of 11 out of the 15 keratoconus corneas (73%), the arrangement of the collagen lamellae differs from those of the para-apical regions and normal corneas. Their collagen fibrils form uniform layers and no delimited collagen lamellae can be differentiated. Interlacing between adjacent layers is extremely decreased or even absent. In the para-apical region of keratoconus corneas the three-dimensional arrangement of collagen lamellae does not differ from that in normal corneas. Conclusion: Stromal thinning and conical ectasia in the apex of keratoconus corneas alters the organization of collagen. This will certainly affect the biomechanical properties of the cornea and further lead to a progression of keratoconus irrespective of its primary pathogenesis.

Monocular and binocular reading performance in children with microstrabismic amblyopia

Aim: To evaluate if functionally relevant deficits in reading performance exist in children with essential microstrabismic amblyopia by comparing the monocular and binocular reading performance with the reading performance of normal sighted children with full visual acuity in both eyes. Methods: The reading performance of 40 children (mean age 11.6 (SD 1.4) years) was evaluated monocularly and binocularly in randomised order, using standardised reading charts for the simultaneous determination of reading acuity and speed. 20 of the tested children were under treatment for unilateral microstrabismic amblyopia (visual acuity in the amblyopic eyes: logMAR 0.19 (0.15); fellow eyes −0.1 (0.07)); the others were normal sighted controls (visual acuity in the right eyes −0.04 (0.15); left eyes −0.08 (0.07)). Results: In respect of the binocular maximum reading speed (MRS), significant differences were found between the children with microstrabismic amblyopia and the normal controls (p = 0.03): whereas the controls achieved a binocular MRS of 200.4 (11) wpm (words per minute), the children with unilateral amblyopia achieved only a binocular MRS of 172.9 (43.9) wpm. No significant differences between the two groups were found in respect of the binocular logMAR visual acuity and reading acuity (p>0.05). For the monocular reading performance, significant impairment was found in the amblyopic eyes, whereas no significant differences were found between the sound fellow eyes of the amblyopic children and the control group. Conclusion: In binocular MRS, significant differences could be found between children with microstrabismic amblyopia and normal controls. This result indicates the presence of a functionally relevant reading impairment, even though the binocular visual acuity and reading acuity were both comparable with the control group.

Interlacing of collagen lamellae in the midstroma of the human cornea.

Purpose. To investigate by means of scanning electron microscopy (SEM) the interlacing of collagen lamellae in the midstroma of the human cornea after opening the interlamellar spaces. Material and Methods. For SEM, cells and noncollagenous extracellular matrix were removed with 10% sodium hydroxide. Specimens were dehydrated in a series of graded tertiary butanols, frozen at −24°C and dried in an exsiccator by sublimation of the frozen butanol. Dried corneas were cut vertically with a razor blade, and the interlamellar spaces were exposed by stretching the stroma along its anterior-posterior axis by pulling apart the inner (endothelial) and outer (epithelial) edges. Specimens were sputtered with gold and examined with a Cambridge Stereoscan 90 microscope. Results. The opened interlamellar spaces gave the stroma at the cutting edge the appearance of a polymorphic honeycomb. The stromal openings differed in size, from approximately 10 &mgr;m to over 150 &mgr;m length and up to 80 &mgr;m in height. Adjacent lamellae remained connected at several interconnecting regions, either through an exchange of short merging sublamella or single fibrils. Interlacing lamellae crossed through fissures between the branches of splitting lamellae. Others crossed clefts of neighboring lamellae, and other lamellae tunneled crosswise through a horizontally split lamellae hanging in the inferior branch as in a hammock. Large interweaving zones in which a mixture of several types of interlacing was localized close together could also be found. Conclusion. The current study indicates that interlacing is a distinct and important feature of the human cornea, and it gives new insights into the stromal morphology by demonstrating various types of interlacing that occur between collagen lamellae.

Reading performance depending on the type of cataract and its predictability on the visual outcome.

Purpose: To investigate the influence of various types of cataract on reading performance in a standardized reading test setting. Setting: Department of Ophthalmology, University of Vienna, Vienna, Austria. Methods: The reading performance of 94 eyes with age‐related cataract and normal macular function was evaluated with the Radner Reading Charts preoperatively and 4 weeks after cataract surgery. Distance visual acuity was tested with the ETDRS charts. Cataracts were graded using the Lens Opacities Classification System (LOCS) III, on which NO is nuclear opalescence and NC is nuclear color. Results: Patients with pure nuclear cataracts (LOCS III: NO/NC 2.1‐5) achieved a normally high MRS (99.84% ± 7.65% of their postoperative MRS): preoperative MRS1: 190.6 ± 30.74 words per minute (wpm); postoperative MRS2: 191.21 ± 29.36 wpm. Patients with mixed nuclear‐cortical cataracts (LOCS III: NO/NC 2.1‐5; C>2) preoperatively achieved 96.96% ± 5.6% of their postoperative MRS (MRS1: 175.77 ± 31.54 wpm; MRS2: 181.34 ± 30.56 wpm). In dense nuclear cataracts (LOCS III: NO/NC>5), the MRS was significantly reduced, achieving only 72.64 ± 19.19% of the postoperative MRS (MRS1: 133.06 ± 39.43 wpm; MRS2: 185.76 ± 40.18 wpm). In posterior subcapsular cataracts, the preoperative MRS (134.1 ± 33.72 wpm) was significantly lower than postoperatively (191.14 ± 27.08 wpm). Conclusions: In contrast to dense nuclear cataracts and posterior subcapsular cataracts, the preoperative reading speed of patients with pure nuclear or nuclear‐cortical cataracts was normal at large print sizes. The preoperative evaluation of reading acuity and speed with standardized reading tests can therefore be used to estimate the postoperative reading performance in the latter 2 types of cataract.

Design of short Spanish sentences for measuring reading performance: Radner-Vissum test

PURPOSE: To develop 24 short Spanish optotype sentences for the construction of a test based on the Radner reading test to simultaneously measure near visual acuity and reading speed. SETTING: Department of Refractive Surgery, Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain. METHODS: Thirty‐one sentences were constructed in Spanish following the procedure defined by Radner to obtain sentence optotypes with comparable structure and the same lexical and grammatical difficulty. Sentences were statistically selected and standardized in 60 patients divided into 2 groups by educational level. Group A (30 patients) had a university education and Group B (30 patients), a primary school education. The interval of reading time was defined as the overall mean ±1.1 × SD. All sentences with a mean between 3.59 seconds and 4.04 seconds were selected for the reading charts. RESULTS: The mean age was 30.8 years ± 6.2 (SD) in Group A and 37.3 ± 10.7 years in Group B. The mean reading time was 3.8 ± 0.9 seconds in all patients, 3.5 ± 0.6 seconds in Group A, and 4.1 ± 1.0 seconds in Group B. CONCLUSION: The 24 short single Spanish sentences were highly comparable in syntactical structure; number, position, and length of words; lexical difficulty; and reading length.

Influence of sex, visual acuity, and systemic disease on delayed presentation for cataract surgery in Austria.

Purpose: To determine the influence of sex, age, preoperative visual acuity, and systemic disease on the delay in presentation for first‐eye cataract surgery. Setting: University Eye Clinic, Vienna, Austria. Methods: This retrospective study comprised 200 consecutive patients with age‐related cataract who were referred to the Ophthalmology Department of the University of Vienna and who had cataract surgery in the first eye. Patients with additional intraocular procedures or with other ocular comorbidity were excluded. Age, sex, preoperative best corrected Snellen visual acuity in both eyes, ocular and systemic comorbidity, and the duration of preoperative visual deterioration were recorded. The patients were divided into groups depending on systemic comorbidity. The severity of disease was categorized as no therapy necessary or nonexistent, nonsevere, or severe. Results: The mean age of women and men was 74.9 years and 70.7 years, respectively, and the mean preoperative visual acuity, 0.31 and 0.24. The duration of preoperative visual deterioration was 8.6 months and 12.2 months, respectively. All differences were statistically significant (P < .05). The visual acuity in the better eye was not significantly different between men and women. Neither the presence nor the type of systemic disease influenced preoperative visual acuity or the duration of preoperative visual deterioration. Conclusions: Although the visual acuity in the better eye was not different between men and women, men had cataract surgery after a longer duration of visual deterioration and with a worse visual acuity. More public information about cataract surgery is required to keep visual deterioration secondary to cataract to a minimum.

Ultrastructure of clear corneal incisions

Purpose: To examine the ultrastructure of clear corneal incisions (CCls) performed with diamond keratomes and steel blades as well as the corneal trauma after implantation of a foldable intraocular lens (IOL) through two incision widths. Setting: University Eye Clinic and Institute of Histology and Embryology II, University of Vienna, Austria. Methods: Twenty‐four human cadaver eyes without prior ocular surgery were obtained from the University Eye Bank, Vienna. Single‐plane CCIs were performed with 3.0 and 3.2 mm Alcon steel blades and with a 3.0 mm Huco diamond keratome. The AVIO PhacoFlex II lens was implanted with a Fine II folder. During the entire procedure, the eye pressure was kept between 26 and 30 mm Hg by infusing balanced salt solution into the anterior chamber. Specimens were prepared for light microscopy, transmission electron microscopy, and scanning electron microscopy according to standard procedures. Results: The diamond keratome produced cleaner cuts than the steel blade. After IOL implantation, 3.0 mm steel blade incisions exhibited extensions at their lateral ends. Within these extensions, the collagen lamellae were displaced and torn. This was not true with 3.2 mm tunnels. Because of the thickness of a 3.0 mm diamond keratome, the extent of corneal trauma was between that found with 3.0 and 3.2 mm steel keratome tunnels. Conclusions: Implantation of the SI‐30 through 3.0 mm CCls produced by the steel blade led to more severe corneal trauma than implantation through 3.2 mm steel blade incisions or 3.0 mm diamond keratome incisions. Thus, IOL implantation through incisions that are too small intensifies corneal trauma.

Ultrastructure of clear corneal incisions: Part II: Corneal trauma after lens implantation with the Microstaar injector system

Purpose: To examine the ultrastructure of clear corneal incisions (CCls) after implantation of a plate‐haptic intraocular lens (IOL) with the Microstaar™ injector system through two incision widths. Setting: University Eye Clinic and Institute of Histology and Embryology II; University of Vienna, Austria. Methods: Fourteen human cadaver eyes without prior ocular surgery were obtained from the University Eye Bank, Vienna. Single‐plane CCls were performed with 3.0 and 3.2 mm steel keratomes. Using the Microstaar injector system, a foldable silicone plate‐haptic IOL (23 diopters) was implanted in the anterior chamber. During the entire procedure, the eye pressure was kept between 26 and 30 mm Hg by infusing balanced salt solution into the anterior chamber. Specimens for light microscopy and scanning electron microscopy were prepared according to standard procedures. Results: After IOL implantation, the 3.0 mm steel blade incisions exhibited distinct distensions at their lateral ends. Adjacent to these distensions, the collagen lamellae were pressed apart, displaced, and torn. In 3.2 mm tunnels, the corneal trauma at both lateral ends was considerably less severe. These incisions also showed a better primary adaptation of the wound lips after implantation. Conclusions: Implantation performed with the Microstaar injector system through 3.0 mm steel blade CCIs led to considerably more severe corneal trauma than implantation through 3.2 mm incisions.

Zur dreidimensionalen Anordnung der kollagenen Lamellen im posterioren Stroma der menschlichen Hornhaut

ZusammenfassungDie dreidimensionale Anordnung der kollagenen Lamellen in der menschlichen Hornhaut ist bis heute nicht restlos geklärt. In einer Vorversuchsreihe haben wir eine spezielle Präparationstechnik zur optimalen Darstellung des Kollagens in der Cornea entwickelt und untersuchten mittels Raster- und Transmissionselektronenmikroskopie die Anordnung der subendothelialen Lamellen in verschiedenen Regionen (limbal, parazentral, zentral) der menschlichen Hornhaut.Die kollagenen Lamellen verlaufen nicht nur in einer Ebene, sondern erreichen, indem sie sich aufteilen und durchkreuzen, auch benachbarte Hornhautschichten. Die Teilungswinkel der Lamellen betragen in der gesamten Cornea etwa 25 °. Auffällig ist, daß die Kreuzungswinkel in den verschiedenen Regionen unterschiedlich sind. Sie betragen in der limbalen Region durchschnittlich 25 °; parazentral und zentral variieren sie zwischen 40° und 75°. Eine limbusparallele Hauptverlaufsrichtung läßt sich für die limbale und parazentrale Region ermitteln.SummaryThe discussion about the three-dimensional arrangement of collagen lamellae in the human cornea is equivocal. In the present study we investigated the limbal, paracentral and central region of the posterior layer of human corneal stroma by scanning and transmission electron microscopy.In all regions lamellae split into branches at angles of about 25 ° and are interlaced by crossing each other. By doing so lamellae reach different layers. In all regions we found splitting angles of about 25 °. However, different angles of criss-crossing were found — in the limbal region of about 25 °; in the paracentral and central cornea the angles vary between 40 ° and 75 °. In the limbal and paracentral region we could demonstrate a main course of the lamellae which is parallel to the limbus.