Central corneal thickness changes and horizontal corneal diameter in premature infants: A prospective analysis.

To report observations of horizontal corneal diameter (HCD) and central corneal thickness (CCT) changes in premature infants with stable optic disc cupping and intraocular pressures (IOPs). The HCD and CCT at term serve as a baseline for premature infants.Sixty-three premature infants were enrolled in a prospective case series. HCD, CCT, and IOP were measured. RetCam images of the optic discs were used to evaluate the cup-disc ratio (CDR) and read by an independent masked observer. Data were collected at between preterm (32-36 weeks) and again at term (37-41 weeks) postconceptual age. Left eye measurements were used for statistical analysis. Left eye findings were combined to construct predictive models for HCD and CCT.The mean HCD was 9.1 mm (standard deviation [SD] = 0.7 mm) at preterm and 10.0 mm (SD = 0.52 mm) at term. The mean CCT preterm was 618.8 (SD = 72.9) µm and at term 563.9 (SD = 50.7) µm, respectively. The average preterm CDR was 0.31 and at maturity was 0.33. Average IOP of preterm and term was 13.1 and 14.11 mm Hg, respectively. There was significant linear correlation between HCD with the postmenstrual age (r = 0.40, P < .01) and the head circumference (r = 0.33, P < .05). Predictive models were constructed for HCD (R = 0.52, 0.2 mm/wk) and CCT (R = 0.23, -11.4 µm/wk) with postconceptual ages.The HCD and CCT variation did not affect IOP reading over time. CCT was not correlated with birth parameters and decreased as the infant reached term. Corneal diameter correlated with gestational age at birth and head circumference.

Investigating the Short-term Effect of Eyelid Massage on Corneal Topography.

PURPOSE: The aim of this study was to evaluate the short-term effect of eyelid massage, after the use of warm compresses, on corneal topography. METHODS: Corneal topography was evaluated on 20 subjects (mean age, 47.0 [SD ±17.3] years) using the Oculus Keratograph (Oculus, Wetzlar, Germany). Corneal eccentricity (Epsilon) was compared between topography measurements before eyelid warming (using warm compresses) (T1), after eyelid warming (T2), directly after eyelid massage (T3), and 30 minutes after eyelid massage (T4). Differences in corneal eccentricity between the enrolment measurement (T1) and consecutive measurements (T1-4) were analyzed. The contralateral eye-treated by warm compresses, but not by eyelid massage-was the control. Visual acuity (decimal), bulbar conjunctival hyperemia, and corneal staining (Cornea and Contact Lens Research Unit grading scale) were evaluated at T1 and T4 to assess clinical safety. RESULTS: No significant differences were found between consecutive eccentricity measurements overall and with the central radii (repeated-measures analysis of variance, P > .238 (massaged eyelid: Epsilon T1: 0.48 [95% confidence interval, ±0.07], T2: 0.49 [±0.05], T3: 0.49 [±0.06], T4: 0.48 [±0.06]; horizontal radii T1: 7.76 [±0.13] mm, T2: 7.74 [±0.13] mm, T3: 7.75 [±0.13] mm, T4: 7.76 [±0.13] mm; vertical radii T1: 7.56 [±0.12] mm, T2: 7.55 [±0.10] mm, T3: 7.54 [±0.10] mm, T4: 7.58 [±0.11] mm). Decimal visual acuity significantly improved at the end of the study (massaged eyelid: T1: 1.1 [±0.1]; T4: 1.3 [±0.1]; P < .032). No significant differences were detected between the consecutive evaluation of corneal staining (Wilcoxon test; P > .285). Redness was not significantly different between time points (repeated-measures analysis of variance; P = .187) in the colateral eyes. Hyperemia was significantly reduced in the massaged eyes (T1: 2.0 grade units [±0.3]; T4: 1.9 [±0.3]; P = .021). CONCLUSIONS: Eyelid warming followed by eyelid massage appears to be a safe procedure, without any clinically relevant short-term effects on the cornea.

Proniosome-derived niosomes for tacrolimus topical ocular delivery: in vitro cornea permeation, ocular irritation, and in vivo anti-allograft rejection.

The objective of this study was to develop proniosome-derived niosomes for topical ophthalmic delivery of Tacrolimus (FK506). The FK506 loaded proniosomes containing poloxamer 188 and lecithin as surfactants, cholesterol as a stabilizer, and minimal amount of ethanol and trace water reconstituted to niosomes prior to use. The stability of FK506 loaded proniosomes was assessed, and the morphology, size, zeta potential, surface tension, and entrapment efficiency of the derived niosomes were characterized, indicating they were feasible for instillation in the eyes. The in vitro permeation of FK506 through the freshly excised rabbit cornea, the cumulative permeation amount of FK506 from niosomes, and the drug retention in the cornea all exhibited significant increase as compared to 0.1% FK506 commercial ointments. The in vivo ocular irritation test of 0.1% FK506 loaded niosomes instilled 4 times per day in rat eyes for 21 consecutive days showed no irritation and good biocompatibility with cornea. The in vivo anti-allograft rejection assessment was performed in a Sprague-Dawley (SD) rat corneal xenotransplantation model. The results showed treatment with 0.1% FK506 loaded niosomes delayed the occurrence of corneal allograft rejection and significantly prolonged the median survival time of corneal allografts to13.86±0.80days as compared with those treated with 1% Cyclosporine (CsA) eye drops, drug-free niosomes, or untreated. In conclusion, the proniosome-derived niosomes may be a promising vehicle for effective ocular drug delivery of FK506.

Commanding roles of keratocytes in health and disease.

The healthy corneal stroma comprises a 3-dimensional network of keratocytes interconnected by cellular processes divided by gap junctions. The shape of the corneal stromal cells is regulated by the presence of extracellular collagen matrix. Furthermore, if compact collagen are present around keratocytes, they decrease their mitotic activity so that the cells in normal healthy cornea are quiescent with low proliferative activity. However, when extracellular collagen is disrupted such as when inflammatory cells infiltrate the corneal stroma and release proinflammatory cytokines including interleukin 1 and tumor necrosis factor α, keratocytes are released from their network structure and undergo active proliferation. However, culturing keratocytes in the presence of tumor necrosis factor α dose dependently downregulates the presence and function of gap functions. Keratocytes also have phagocytic activities; foreign particles are internalized into these cells. In corneal ulceration, microorganisms invading the stroma secrete collagen-degrading enzymes and signaling molecules such as elastase and lipopolysaccharide that activate corneal keratocytes to secrete stroma-degrading matrix metalloproteinase and various chemokines to attract immune cells to the focus area of corneal stroma. Thus, keratocytes actively participate in collagen degradation of corneal ulceration. The Chinese herbal extract triptolide has been demonstrated significantly and dose dependently to decrease collagen degradation by condition medium-induced corneal fibroblasts. In ocular health, keratocytes respond to signals to and from epithelial cells. In ocular disease, keratocytes become activated cells that respond to various cytokines. Hence, keratocytes play commanding roles in ocular health and disease.

Effect of warm compress therapy from hard-boiled eggs on corneal shape.

PURPOSE: Hard-boiled eggs can be used for warm compresses, but the pressing force may distort the corneal shape. This study investigated the effect of warm compress therapy on the corneal shape by using hard-boiled eggs as the heat source. METHODS: Twenty-five young adult Chinese were recruited, and 1 eye was randomly selected to undergo the following treatment protocols in a random order: hot hard-boiled egg covered with wet cloth gently touching the eyelid; hot hard-boiled egg covered with wet cloth placed close to, but not touching, the eyelid; and cold egg covered with wet cloth gently touching the eyelid. Each treatment protocol lasted for 5 minutes. Eyelid temperature was measured using an infrared thermometer before and every 1 minute during the treatment. Corneal parameters, including SimK, best-fit sphere (BFS), surface asymmetry index (SAI), and surface regularity index (SRI), were measured by a corneal topographer before and after the treatment. RESULTS: Treatment 1 gave a 3.5 degrees C skin temperature rise within 3 minutes. The skin temperature rise was around 2.5 degrees C in treatment 2. There was no skin temperature change in treatment 3. Both treatments 1 and 3 affected the SAI and SRI. There was no significant change on other corneal parameters from treatments. CONCLUSION: Because it is difficult to standardize the pressing force, it is recommended to place the hard-boiled egg close to, but not touching, the eyelid during warm compress therapy. The temperature rise from this treatment protocol should be large enough to melt the meibomian gland secretions without distorting the corneal shape.

Magnetic compass in the cornea: local anaesthesia impairs orientation in a mammal.

The mechanism of signal transduction during magnetic compass orientation is rarely evident in vertebrates and is as yet unknown in mammals. This transmission has been associated with magnetite-based receptors innervated by the ophthalmic nerve or with the involvement of the eye, particularly the retina. We provide the first behavioural support for the cornea carrying the respective primary sensors in mole-rats (Fukomys anselli) by showing that local anaesthesia disrupts their normal directional magnetic orientation. During corneal anaesthesia in normal geomagnetic conditions, mole-rats did not maintain their preferred nesting direction, but displayed a random orientation pattern. A second experiment showed that the ability of the mole-rat to discriminate between light and dark was not impeded by the same anaesthetic treatment, suggesting no retinal involvement in mole-rat magnetic orientation. Our study restricts the peripheral primary sensors in mole-rats to the ophthalmic region, probably the cornea and indicates magnetite as the responsible signal mediator.

Evaluation of triamcinolone acetonide following intravitreal injection in New Zealand white rabbits.

The safety of intravitreally injected triamcinolone acetonide suspension (TA) was evaluated in rabbits. Each animal received 0.1 ml (1) balanced salt solution (BSS) vehicle, (2) formulation vehicle, (3) 4% TA (4-mg dose), (4) 16% TrAc (16-mg dose) or (5) 25% TA (25-mg dose) as a single intravitreal injection into the right eye. The left eyes served as untreated controls. All animals were observed for 1 month following treatment. In-life evaluations included clinical signs, body weights, slit-lamp biomicroscopic and indirect ophthalmoscopic examinations, intraocular pressure and corneal thickness measurements, and electroretinograms (ERGs). Ocular tissues were harvested following a 1-month post-treatment observation period, fixed, processed, and evaluated by light microscopy. No significant or treatment-related clinical signs were observed for any animals during the study. The opaque white test article was clearly visible in the eye for all TrAc-treated groups, and remained so throughout the study. No statistically significant differences in mean body weights were present between the control and treatment groups, though changes in body weight varied. Corneal thickness was slightly reduced for some treated groups. Intraocular pressures were not statistically significantly different from controls for any treatment group. No significant changes in ERG were evident between treatment groups or from baseline readings. Microscopically, basophilic material (presumed to be drug) was seen in the vitreous of all or most treated eyes, with accumulations in the vitreous or in clumps adjacent to the retinal surface. No pathological changes were observed in the retina or other ocular structures. Triamcinolone acetonide suspension was safe and well tolerated following intravitreal injection in New Zealand white rabbits.

Corneal morphometry prior to and five years after corneal stromal photoablation: the possible role of topical anesthesia on postablative corneal morphometry / Morfometría corneal previa a y cinco años tras fotoablación estromal corneal: el posible papel de la anestesia tópica en la morfometría corneal postablativa

The aim of this study was to investigate central corneal thickness values prior to and five years after ablation of the central cornea using 193 nm UV radiation. Thirty eight eyes of 38 subjects were analysed in a prospective study. Central corneal thickness measurements were carried out prior to and 60 months after corneal stromal photoablation under a 160 ?m flap with the Summit Excimed SVS plus excimer laser (Summit Technology, Inc. Walthan, MA). Mean intended ablation depth was 55±20 ?m. Central corneal thickness measurements were carried out with the DGH 2000 AP ultrasonic pachymeter (DGH Technology, Inc., San Diego, USA). Consecutive central corneal thickness readings were made until three consecutive measurements were within 5 mm of each other. The mean of these three consecutive readings was used as the value of central corneal thickness in this study. Preoperative mean central corneal thickness was 556±55 ?m; five years later it was 513.41 ?m (p<0.001). The difference between the "theoretical" postablative corneal thickness values and the "real" corneal thickness values observed 60 months after stromal photoablation was also significant (p<0.001). Five years after central corneal stromal photoablation using 193 nm UV radiation there was a disparity between the programmed postoperative residual corneal thickness and the corneal thickness obtained by ultrasound pachymetry. Further research is neccesary in order to identify possible unexpected values of corneal thickness after a paracentral corneal stromal photoablation has been carried out (AU)

El objetivo de este estudio era investigar los valores del espesor corneal previo a y cinco años tras la ablación de la córnea central empleando radiación UV de 193 nm. Treinta ojos de treinta sujetos fueron analizados en un estudio prospectivo. Las mediciones del espesor corneal se realizaron previo a y 60 meses tras la fotoablación estromal bajo un flap de 160 micras con el láser excimer Summit Excimed SVS plus (Summit Technology, Inc. Walthan, MA). La media de la ablación intentada fue de 55ñ20 micras. Las mediciones del espesor corneal central se realizaron con el paquímetro ultrasónico DGH 2000 AP (DGH Technology, Inc. San Diego, USA). Se realizaron mediciones consecutivas del espesor corneal hasta que tres consecutivas de ellas estuviesen entre 5 micras de diferencia. La media de estas tres mediciones consecutivas se usó como el valor del espesor central en este estudio. El espesor central medio era 565ñ55 micras; cinco años después era 513ñ41 micras (p<0.001). La diferencia entre los teóricos valores del espesor corneal y los verdaderos observados 60 meses tras la ablación estromal también fue significativa (p<0.001).Cinco años tras la fotoablación estromal empleando radiación UV de 193 nm existe una disparidad entre el espesor residual postoperativo programado y el espesor corneal obtenido mediante paquimetría ultrasónica. Es necesaria mayor investigación con la finalidad de identificar los posibles valores inesperados del espesor corneal tras ser realizada una ablación estromal paracentral (AU)

Corneal topography after ocular rubbing.

PURPOSE: To examine the immediate effect of ocular rubbing on corneal topography. METHODS: Corneal topography and analysis were performed before, immediately after, and 5 minutes after eyelid rubbing in 29 volunteers without ocular disease. RESULTS: The surface regularity index increased from a baseline of 0.24 to 0.91 ( p< 0.0001) immediately after rubbing and returned to baseline after 5 minutes. The surface asymmetry index increased from 0.27 to 0.89 ( p= 0.0018) immediately after rubbing. There was a small amount of astigmatism induced immediately by rubbing (0.5 diopter) ( p= 0.01). CONCLUSIONS: Ocular rubbing should be avoided prior to standard corneal topography. The increased surface regularity index may reflect the alterations of the tear film and/or the molding of the corneal surface.

Myopia associated with hyperbaric oxygen therapy.

BACKGROUND: Hyperbaric oxygen therapy (HBOT) involves exposing patients to elevated oxygen pressures and concentrations for the treatment of soft tissue degenerative diseases. As side effects, some patients experience cataract development and/or a significant increase in myopia. SUBJECTS: Eight subjects participated in this project. All were receiving HBOT for health problems. METHODS: For all subjects, acuities and refractive error corrections were measured before and after HBOT sessions at the beginning, midpoint, and end of therapy. For four subjects, A-scan ultrasound and corneal curvature measurements were also made before and after selected HBOT sessions. In addition, susceptibility to free radical damage and indicators of actual damage were measured by blood analyses. During the first half of HBOT therapy, four subjects took placebo tablets; during the second half, antioxidant supplements were given. RESULTS: No subject showed significant acuity or refractive error changes produced by single HBOT sessions. Two of the 8 subjects showed significant increases in myopia over the 20 session course of HBOT. No corresponding changes were found in the ultrasound, corneal curvature, or blood analysis data. DISCUSSION: Theoretically, the increases in myopia could have been caused by lenticular refractive index changes resulting from oxidative damage to lens proteins. However, the biochemical assays used in this project did not predict which subjects were susceptible to increased myopia, nor did they demonstrate elevated levels of free radical activity in a subject who did experience an increase in myopia.

The effects of UW solution and its components on corneal thickness during and after storage.

The ability of rabbit corneas to undergo energy-dependent deturgescence was examined after the corneas were stored at 4 degrees C in UW solution, M-K media, or selected modifications of these media. All corneas slowly increased in thickness during storage, despite the presence of colloidal osmotic agents. Corneas stored for 2.5 days in M-K became slightly thinner when cultured over a 24-hour period. Corneas stored in UW swelled quickly in culture and became too opaque to measure within three hours. Corneas stored in UW with 1.8 mM CaCl2 swelled transiently, then maintained their thickness and exhibited deturgescence in the latter stages of the culture period. Deturgescence of corneas stored for 7 days in M-K was only slightly worse than those stored for 2.5 days. Corneas stored for 7 days in UW, however, became opaque almost immediately in culture and those stored in calcium-supplemented UW became opaque within 4.5 hours. Replacement of the dextran in M-K with hydroxyethyl starch produced a slower rate of corneal swelling during storage and a substantially better corneal deturgescence profile during culture. Use of high concentrations of potassium ion in the M-K formulation had no significant effect on post-storage deturgescence. Replacement of glucose in M-K with the impermeable sugar, raffinose had a slight deleterious effect on corneal deturgescence in subsequent culture. Use of the impermeable anions gluconate or lactobionate to replace chloride ion caused profound corneal swelling during culture, compared with those stored in M-K. These experiments show that UW solution is inferior to M-K at preserving post-storage corneal function.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperbaric oxygen and corneal incision healing.

Corneal incision healing in the presence of daily or twice daily exposures to hyperbaric oxygen was compared in dogs to the natural course of such healing. Exposures lasted for 90 min and consisted of 60% oxygen administered at 60 fsw, an oxygen exposure of 2 ATA. Twenty corneas received such exposure, and 20 corneas were allowed to heal under natural conditions. Eyes were enucleated between 5 and 56 days after incision. The corneas were studied by gross observation and light microscopy. Uncomplicated and essentially comparable healing of the incisions occurred. There was a suggestion that superficial central clearing of the incision opacity occurred more quickly in the hyperbaric oxygen series.