Age-related changes in with-the-rule and oblique corneal astigmatism.

PURPOSE: To describe the age-related changes in with-the-rule (WTR) and oblique keratometric astigmatism (KA), posterior corneal astigmatism (PCA) and total corneal astigmatism (TCA). METHODS: We used a Pentacam HR (high-resolution) rotating Scheimpflug camera to determine the KA, PCA and TCA in the right eyes of 710 patients, aged from 20 to 88 years. The age-related changes along the vertical, horizontal and oblique meridians were analyzed with Naeser's polar value method in a cross-sectional study. RESULTS: In the whole group, all meridional astigmatic powers and polar values were stable in the age groups from 20 to 49 years, followed by a 1.0 dioptre (D) against-the-rule (ATR) change in KA and TCA, and a 0.12 D reduction in against-the-rule PCA. A nasal rotation of the steep meridian in KA and TCA was noted in the 70-88 years old. The PCA averaged approximately 0.25 D ATR in all age groups. Females displayed the same early astigmatic stability as in the whole group, while male eyes demonstrated a linear decay from 1.5 D WTR at 20 years to 0.5 D ATR astigmatism for the oldest patients. CONCLUSION: Corneal astigmatism is stable until the age of 50 years; thereafter both keratometric and total corneal astigmatism show a 0.25 D ATR change per 10 years. The average 0.25 D ATR PCA compensates the predominant keratometric WTR astigmatism in the younger patients and increases the TCA in the elderly with keratometric ATR astigmatism. The gender-based differences in age-related astigmatism require further studies.

Estimating Total Corneal Astigmatism From Anterior Corneal Data.

PURPOSE: To determine keratometric astigmatism (KA), posterior corneal astigmatism (PCA), and total corneal astigmatism (TCA) in 951 normal eyes, to establish a model for estimating TCA from anterior corneal data, and to test this method in a new group of eyes with toric intraocular lenses (TIOLs). METHODS: We used a Pentacam HR (high-resolution) Scheimpflug camera to determine KA, PCA, and TCA in 951 normal eyes. A model to estimate TCA from anterior corneal data was evaluated by the difference (=error) between the measured TCA and the estimated value. The model was tested in 40 eyes with TIOLs. RESULTS: KA, TCA, and PCA averaged 1.06 (±0.85) D, 1.05 (±0.83) D, and 0.33 (±0.17) D. The error of the model to estimate TCA averaged zero with an SD of ±0.21 D. Application of this model and of direct Pentacam TCA measurements in TIOL calculation gave similar results, namely a slight reduction of overcorrection in with-the-rule astigmatism, but an eradication of undercorrection in against-the-rule astigmatism. CONCLUSIONS: It was possible to estimate TCA accurately from anterior corneal data with a new formula. However, application of both this model on keratometric data and of direct Pentacam measurements in a group of 40 eyes with TIOLs did not completely eradicate the refractive error in TIOL calculation. More studies comparing Pentacam TCA and refractive astigmatism are required.

Corneal powers measured with a rotating Scheimpflug camera.

BACKGROUND/AIM: Keratometry measures the anterior corneal curvature only. Corneal power is calculated by multiplication with the keratometric refractive index, which takes into account the average negative posterior corneal power. The aim of this study was to calculate and compare various expressions for total corneal power assessed with Scheimpflug camera techniques, which also measure the posterior corneal curvature. METHODS: We used the Pentacam rotating Scheimpflug camera to measure the equivalent power, total corneal refractive power (based on Snell's law ray tracing), and simulated keratometry (keratometric refractive index=1.3375) over the central 3.0 mm zone in 951 eyes. The keratometric refractive index of the equivalent power and the total corneal refractive power was calculated as the ratio between these values and the anterior corneal curvature. RESULTS: The equivalent power, total corneal refractive power, and simulated keratometry all differed statistically significantly (analysis of variance, p<0.001) and averaged 42.26 (±1.46) dioptres (D), 42.78 (±1.51) D and 43.42 (±1.49) D. The calculated keratometric refractive indices for equivalent and total corneal refractive power averaged 1.3284 (±0.0009) and 1.3324 (±0.0015). The error of using these calculated keratometric refractive indices rather than the measured values for equivalent and total corneal refractive power averaged 0 (±0.11 D) and -0.01 D (±0.19). CONCLUSIONS: Pentacam rotating camera assessment of total corneal power over the central 3.0 mm zone differed significantly for simulated keratometry, equivalent power and Snell's law ray tracing.

Refractive, anterior corneal and internal astigmatism in the pseudophakic eye.

PURPOSE: To evaluate the correlation between refractive astigmatism (RA) and anterior corneal astigmatism (ACA), and determine the internal astigmatism (IA) in 184 pseudophakic eyes. METHODS: The study was a prospective non-masked single-centre study. Patients were examined 8 weeks after phacoemulsification with implantation of aspheric one-piece monofocal IOLs. Examination included autokeratometry and subjective refraction. All refractive data were converted to the corneal plane. The corneal refractive index, taken to be 1.376, was used to estimate the ACA. All astigmatisms were converted to net curvital and net torsional powers with the steeper corneal plane as the reference meridian. Curvital power is the force acting along a given meridian, and torsion is the power twisting the astigmatic direction out of that plane. The internal astigmatism (IA) was calculated as the difference between RA and ACA. RESULTS: For curvital powers, the refractive astigmatism (KP(Φ)RA ) could be described as a function of anterior corneal astigmatic magnitude (KP(Φ)ACA ) and direction α by the multiple linear regression equation: KP(Φ)RA = -0.09 + 0.61*KP(Φ)ACA + 0.33*cos2α, (r(2) = 0.59, p < 0.0001). The average internal astigmatism amounted to 0.47 D inclined 92° relative to the steeper anterior corneal meridian. The magnitude of internal astigmatism depended on the angle α of the steeper anterior corneal meridian, averaging 0.86 D at 91° for with-the-rule, 0.37 D at 95° for oblique and 0.17 D at 97° for against-the-rule corneal astigmatisms. CONCLUSIONS: The internal astigmatism varies as a function of the direction of the anterior steeper corneal meridian. In patient candidates to surgical correction of astigmatism, measuring only the curvature of the anterior corneal surface and neglecting that of the posterior corneal surface can lead to inaccurate evaluation of total corneal astigmatism.

Reappearance of the tapetal-like reflex after prolonged dark adaptation in a female carrier of RPGR ORF15 X-linked retinitis pigmentosa.

PURPOSE: To report changes in the tapetal-like reflex in a female carrier of RPGR ORF15 c.3395delA X-linked retinitis pigmentosa (XLRP) between examinations at 16 and 22 years of age, and to report the observation that the tapetal-like reflex faded due to exposure to daylight and reappeared with prolonged dark adaptation at 22 years of age. METHODS: Clinical examination, kinetic Goldmann perimetry, dark adaptometry, fundus autofluorescence photography, spectral domain optical coherence tomography (SD-OCT), full-field electroretinography (ffERG), and multifocal electroretinography (mfERG) were performed. RESULTS: A female carrier of RPGR XLRP presented with a tapetal-like reflex at age 16. At age 22, the tapetal-like reflex was absent upon examination in daylight; however, the reflex reappeared after 12 h of dark adaptation. Fundus autofluorescence was unremarkable and did not change after prolonged dark adaptation. Full-field electroretinography and dark adaptometry at age 22 demonstrated reduced rod and cone function compared to at age 16. CONCLUSIONS: Dark adaptation before fundus photography may enable the detection of a tapetal-like reflex where it is otherwise invisible. The light-dependent fluctuation of a disease-related substance in the photoreceptors should prompt further study of the potential role of light as a modulator of the progression of RPGR XLRP.

Prevalence of generalized retinal dystrophy in Denmark.

PURPOSE: Generalized retinal dystrophy is a frequent cause of visual impairment and blindness in younger individuals and a subject of new clinical intervention trials. Nonetheless, there are few nation-wide population-based epidemiological data of generalized retinal dystrophy. The purpose of this study was to examine the prevalence and diagnostic spectrum of generalized retinal dystrophy in the Danish population. METHODS: A population-based cross-sectional study with data from the Danish Retinitis Pigmentosa Registry that comprises all patients in Denmark with generalized retinal and chorioretinal dystrophies from the 19th century to the present. Among 3076 registered cases, the primary diagnosis of generalized retinal dystrophy was assessed by chart review, including fundus photographs and electroretinograms. Demographic data on the Danish population were retrieved from Statistics Denmark. RESULTS: Of the 5,602,628 Danish citizens on January 1, 2013, 1622 patients were registered as having a generalized retinal dystrophy and were alive and living in Denmark, corresponding to a prevalence of 1:3,454. In 28% of cases the eye condition was part of a syndrome, while the remaining 72% had eye disease only. Aside from simplex cases (45%), the most common hereditary pattern was autosomal recessive (23%). CONCLUSION: This epidemiological survey demonstrates that the prevalence of generalized retinal dystrophy in the Danish population is 1:3454. Many of the dystrophies are the subjects of clinical intervention trials, and nation-wide epidemiological data can help assess the burden of the disease and the future need for treatment.

A tapetal-like fundus reflex in a healthy male: evidence against a role in the pathophysiology of retinal degeneration?

PURPOSE: To report on the retinal function and structure in a 37-year-old male who presented with a tapetal-like reflex (TLR) indistinguishable from that seen in female carriers of X-linked retinitis pigmentosa (XLRP). METHODS: Clinical examination included dark adaptometry, full-field electroretinography (ERG), multifocal ERG, optical coherence tomography, and fundus autofluorescence photography. Molecular genetic testing included screening for known mutations in autosomal dominant, autosomal recessive, and X linked retinitis pigmentosa (RP) genes with a commercially available chip, and sequencing analysis of retinitis pigmentosa GTPase regulator (RPGR)-open reading frame 15 (ORF15). RESULTS: Fundus examination revealed a bilateral TLR, which is typical of female carriers of XLRP. Imaging studies and electrophysiological testing was unremarkable, except for a significant increase in full-field ERG amplitudes after prolonged dark adaptation as compared to after standard dark adaptation. Mutation screening was negative. CONCLUSIONS: TLR was found for the first time, to the best of our knowledge, in a male subject. There were no definitive signs of retinal degeneration, suggesting that this reflex in itself is not necessarily a precursor of the retinal degeneration that can be seen in female carriers of XLRP.

A 52-week, multinational, open-label, parallel-group, noninferiority, treat-to-target trial comparing insulin detemir with insulin glargine in a basal-bolus regimen with mealtime insulin aspart in patients with type 2 diabetes.

OBJECTIVE: This trial compared the efficacy and safety profiles of the insulin analogues detemir and glargine as the basal insulin component of a basal-bolus regimen in patients with type 2 diabetes mellitus (T2DM) who were being treated with oral antidiabetic drugs (OADs) or insulin with or without OADs. METHODS: This was a multinational, 52-week, openlabel, parallel-group, noninferiority, treat-to-target trial. Patients with a diagnosis of T2DM for > or = 12 months who had been receiving an OAD or insulin, with or without OADs, for > 4 months were randomized in a 2:1 ratio to receive detemir or glargine. According to the approved labeling, detemir could be administered once or twice daily, and glargine was administered once daily. Insulin aspart was given at mealtimes. Insulin secretagogues and a-glucosidase inhibitors were discontinued at study entry, and existing OADs were continued. Doses of detemir and glargine were titrated to achieve a prebreakfast (and predinner for detemir administered twice daily) plasma glucose target of < or = 6.0 mmol/L. Patients monitored their plasma glucose levels before breakfast and dinner on the 3 days before each of 13 scheduled visits, recorded their insulin doses on 1 of these 3 days, and recorded their 10-point self-monitored plasma glucose (SMPG) at baseline and after 24 and 52 weeks. The primary efficacy end point was glycosylated hemoglobin (HbA(1c)) at 52 weeks; secondary efficacy end points included changes in fasting plasma glucose (FPG), postprandial plasma glucose, insulin doses, and weight change at 52 weeks. Safety end points included the frequency of hypoglycemia and adverse events (AEs). RESULTS: The intention-to-treat population included 319 patients (58.0% male, 42.0% female; 78.4% white; mean age, 58 years; mean weight, 92.8 kg; mean duration of diabetes, 13.6 years). At study entry, 46.1% of patients were receiving insulin and > or = 1 OAD, 35.4 were receiving insulin only, and 18.5% were receiving > or = 1 OAD only. At 52 weeks, there was no significant difference between detemir and glargine in terms of mean HbA(1c) (7.19% and 7.03%, respectively; mean difference, 0.17% [95% CI, -0.07 to 0.40]) or the mean decrease in HbAlc from baseline (-1.52% and -1.68%). The reduction in HbA(1c) was not significantly affected by whether detemir was administered once or twice daily. There were no significant differences between groups in terms of mean FPG (7.05 and 6.68 mmol/L) or the mean change in FPG from baseline (-2.56 and -2.92 mmol/L; mean difference, 0.36; 95% CI, -0.26 to 0.99). The overall shape of the 10-point SMPG profiles was not significantly different between groups. Mean weight gain at 52 weeks was significantly lower with detemir than with glargine (2.8 vs 3.8 kg; mean difference, -1.04; 95% CI, -2.08 to -0.01; P < 0.05). Doses of basal and prandial insulins at the end of the study were not significantly different between groups. Major hypoglycemic episodes were reported by 4.7% and 5.7% of patients in the respective treatment groups. There was no significant difference in the risk of hypoglycemia between groups. The proportion of patients with AEs and the number of AEs per patient were comparable between groups (185/214 patients [86.4%] reporting 743 AEs and 88/105 patients [83.8%] reporting 377 AEs). CONCLUSIONS: when used as indicated as part of a basal-bolus regimen in patients with T2DM who had previously received other insulin and/or OAD regimens, detemir was noninferior to glargine in its effects on overall glycemic control. Both basal insulins were associated with clinically relevant reductions in hyperglycemia. Both were well tolerated, with no significant difference in the frequency of hypoglycemia or AEs.