Optimal caliper placement: manual vs automated methods.

OBJECTIVE: To examine the inter- and intra-operator repeatability of manual placement of callipers in the assessment of basic biometric measurements and to compare the results to an automated calliper placement system. METHODS: Stored ultrasound images of 95 normal fetuses between 19 and 25 weeks' gestation were used. Five operators (two experts, one resident and two students) were asked to measure the BPD, OFD and FL two times manually and automatically. For each operator, intra-operator repeatability of the manual and automated measurements was assessed by within operator standard deviation. For the assessment of the interoperator repeatability, the mean of the four manual measurements by the two experts was used as the gold standard.The relative bias of the manual measurement of the three non-expert operators and the operator-independent automated measurement were compared with the gold standard measurement by means and 95% confidence interval. RESULTS: In 88.4% of the 95 cases, the automated measurement algorithm was able to obtain appropriate measurements of the BPD, OFD, AC and FL. Within operator standard deviations of the manual measurements ranged between 0.15 and 1.56, irrespective of the experience of the operator.Using the automated biometric measurement system, there was no difference between the measurements of each operator. As far as the inter-operator repeatability is concerned, the difference between the manual measurements of the two students, the resident, and the gold standard was between -0.10 and 2.53 mm. The automated measurements tended to be closer to the gold standard but did not reach statistical significance. CONCLUSION: In about 90% of the cases, it was possible to obtain basic biometric measurements with an automated system. The use of automated measurements resulted in a significant improvement of the intra-operator but not of the inter-operator repeatability, but measurements were not significantly closer to the gold standard of expert examiners.

Early detection of macular changes in patients with diabetes using Rarebit Fovea Test and optical coherence tomography.

AIM: To evaluate central retinal thickness and foveal function using optical coherence tomography (OCT) and the Rarebit Fovea Test (RFT) in patients with diabetes without previously known retinopathy or maculopathy. METHOD: Forty-two patients with diabetes mellitus (DM) were selected from the screening records at St Erik Eye Hospital. Inclusion criteria were absence of macular or other retinal changes at previous screening examination and best corrected visual acuity >/=1.0. These patients and 42 healthy controls were examined with the recently developed RFT, and retinal thickness was measured using OCT. Lens thickness and light scatter were evaluated by Scheimpflug photography. RESULTS: Significantly more DM subjects (12/42) had a subnormal RFT result compared with the controls (2/42) (p = 0.007). None of the 12 DM subjects had maculopathy, one had mild non proliferative diabetic retinopathy, and five had minimal non-proliferative diabetic retinopathy. The retinal thickness in the pericentral zone was significantly (p<0.05) thinner in DM patients with subnormal RFT compared with the controls. CONCLUSION: Decreased RT and subnormal RFT results were found in a subgroup of diabetes patients, despite normal screening results. Prospective studies are under way to evaluate the prognostic implications.

Perception of very small visual stimuli in the fovea: normative data for the Rarebit Foveal Test.

BACKGROUND: Conventional visual tests are not sensitive enough to detect low degree neural damage, as 6/6 (1.0) visual acuity can be upheld with less than two-thirds of the normal number of optic nerve axons. The aim of the current study was to evaluate the physiologic properties of a new computerised test, the Rarebit Fovea Test (RFT), using very small stimuli, by quantifying the effect of age and binocular summation in relation to stimulus luminance. METHODS: The RFT relies on the perception of very small (less than 0.5 minutes of arc) bright stimuli. Two different experiments were performed. 1. Thirty-five subjects (age 19 to 63 years) were tested with five different stimulus luminances, 158, 64, 53, 41 and 33 cd/m(2). 2. Nineteen subjects (age 19 to 63 years) were tested using binocular stimulation to define the binocular summation. RESULTS: Significantly reduced median hit rates were observed at luminances of 53 cd/m(2) or below. Age and mean hit rate correlated negatively at all luminance levels below 158 cd/m(2). The mean hit rate from binocular stimulation, compared to the highest value from monocular stimulation in the same subject, was increased by a factor of 1.54 +/- 0.45 (SD). No age effect was found regarding binocular summation. CONCLUSIONS: The results in the current study indicate that RFT can identify some of the well-known features of the visual system, that is, the effects of age and binocular summation, provided that the stimulus luminance is adequately selected.

A 5-year follow-up study of disease incidence in men with an abnormal hormone pattern.

OBJECTIVES: Previous studies have suggested that abnormal levels of cortisol and testosterone might increase the risk of serious somatic diseases. To test this hypothesis, we conducted a 5-year follow-up study in middle-aged men. METHODS: A population-based cohort study conducted in 1995 amongst 141 Swedish men born in 1944, in whom a clinical examination supplemented by medical history aimed to disclose the presence of cardiovascular disease (CVD) (myocardial infarction, angina pectoris, stroke), type 2 diabetes and hypertension were performed at baseline and at follow-up in the year 2000. In addition, salivary cortisol levels were measured repeatedly over the day. Serum testosterone concentrations were also determined. Using the baseline data, an algorithm was constructed, which classified the secretion pattern of cortisol and testosterone from each individual as being normal or abnormal. RESULTS: By the end of follow-up, men with an abnormal hormone secretion pattern (n = 73) had elevated mean arterial pressure (P = 0.003), fasting insulin (P = 0.009) and insulin : glucose ratio (P = 0.005) compared with men with a normal secretion pattern (n = 68). Body mass index, waist circumference, and waist : hip ratio were significantly elevated in both groups. However, the 5-year incidence of CVD, type 2 diabetes, and hypertension were significantly higher (P < 0.001) in men with an abnormal neuroendocrine secretory pattern compared to men with a normal pattern. CONCLUSIONS: These data suggest that an abnormal neuroendocrine secretory pattern is prospectively associated with an increased incidence of cardiovascular-related events and type 2 diabetes.

Five-year follow-up of treated patients with glaucoma using resolution perimetry.

PURPOSE: The authors describe high-pass resolution perimetry findings during the first five years of antiglaucoma treatment. PATIENTS AND METHODS: Thirty-seven patients were examined six times, once a year for five years, with best corrected visual acuity, applanation tonometry, slitlamp examination, funduscopy, and high-pass resolution perimetry. Twenty-nine of these were treated for glaucoma and eight followed for ocular hypertension without treatment. RESULTS: The resolution thresholds in the treated group improved during the first two years and deteriorated after that back to baseline level. Regarding individual patients, the visual fields were improved in 4, unchanged in 16, and deteriorated in 13 of the 29 treated glaucoma patients at the end of the study period. CONCLUSIONS: Resolution visual fields showed initial improvement and subsequent deterioration in treated patients with early glaucoma. The conventional therapy, aiming at reducing intraocular pressure, appeared to postpone visual field decay for at least five years in about 50% of the patients.

Management of ocular hypertension and open angle glaucoma: clinical practice and computer-assisted decision-making.

PURPOSE: To evaluate the feasibility of computerized decision support in the management of patients with open angle glaucoma or ocular hypertension. METHOD: Based on a Swedish consensus document a computer program was developed, which provided one of 25 different recommendations for appropriate action. In 373 patient visits to seven different eye clinics, the program's recommendations were compared to the actual decisions made by the responsible ophthalmologists. RESULTS: Notable differences were observed between the clinics' management strategies, especially regarding follow-up frequency and start or increase of anti-glaucoma treatment. The program's recommendations conformed with the clinical decisions in 23 to 92% of the cases when a standard management strategy was simulated. The concordance increased to 93 to 100%, when policy differences between the clinics were taken into account. CONCLUSION: Clinical decision-making in the management of patients with ocular hypertension or open angle glaucoma can be implemented in a computer program. The optimum management protocol remains to be defined.

The effect of treatment on the results of high-pass resolution perimetry in glaucoma.

In order to find out to which extent high-pass resolution perimetry would detect any changes in patients treated for glaucoma, resolution perimetry results were evaluated from 56 glaucoma patients and 15 untreated ocular hypertensive patients followed for 2 to 3 years. Fifty-nine of the 71 examined patients showed lower resolution thresholds, i.e. increased sensitivity, after 2 years, compared to initial values. The threshold decrease was significantly larger in the treated glaucoma patients (median 1.22 dB) than in the untreated ocular hypertensive patients (0.48 dB). The threshold decrease in the untreated ocular hypertensive group corresponds to the previously described learning effect. In 35 of the 56 treated glaucoma patients the thresholds improved more than 0.84 dB, the upper confidence limit in the untreated group, which may indicate a beneficial effect of antiglaucoma therapy in these patients. The threshold change was unrelated to initial resolution threshold and cannot be explained by a 'sorting' effect. The observations in the current study using resolution perimetry indicate that improved visual function can be demonstrated in many patients treated for early glaucoma, at least during the first 2 years of treatment.

The effect of topical antiglaucoma drugs on the results of high-pass resolution perimetry.

We conducted a randomly assigned, double-masked, crossover study of the effects of betaxolol, epinephrine, pilocarpine, and timolol on the high-pass resolution perimetry results in normal subjects. The influence of topical administration of these intraocular pressure-reducing drugs was negligible, which confirmed the reliability of high-pass resolution perimetry results. The method seems appropriate for the diagnosis of glaucoma and the follow-up of patients with glaucoma.

Instant photographic refractometry in children.

A simple photographic method for detection and measurement of refractive errors in children, using a specially designed camera and electronic flash unit and 'instant' (Polaroid) film, was tested on 64 children, aged 3 to 8 years, and compared with the results from retinoscopy. The refractive errors ranged from -6.5 to +6.5 D. A light reflex in the pupil was observed on the photos of all children with hyperopia greater than = 0.5 and myopia greater than = 2.0 D. A curvilinear relationship was observed (in the range -2 to -4 and +0.5 to +3 D) between the width of the light reflex in the pupil, easily measured on the photos and the degree of refractive error, determined by retinoscopy. The degree of ametropia could be estimated with reasonable accuracy (+/- 0.5 D) in the interval from -2 to -4 D and +0.5 to +3 D. The method can demonstrate the type and, to a limited extent, also the degree of refraction anomaly and may be of value in screening for refractive errors in children.

Subnormal visual acuity in children: prognosis and visual evoked cortical potential findings.

Seventy-one children, age 4-12 years, with subnormal visual acuity (VA) in at least one eye (0.7 or less) were examined using visual evoked cortical potentials (VECPs) to pattern-reversal stimulation. Twenty-eight children with squint had mean VA 0.3 in squinting and 0.7 in non-squinting eyes. Thirty-one children had unexplained subnormal VA, mean 0.6. Twelve children with mild unclassifiable fundus abnormalities had mean VA 0.5. In the squinting eyes and the eyes with fundus abnormalities the mean latency of the VECP was significantly prolonged. In squinters the mean amplitude to stimulation of the squinting eyes and to binocular stimulation was significantly reduced. Statistically significant increase in the mean VA was observed in all groups except in the cases with visible fundus abnormalities. There was no statistically significant correlation between VECP parameters and final VA. In conclusion, VA prognosis could not be predicted from VECP data in individual cases.

Pattern-reversal electroretinograms and high-pass resolution perimetry in suspected or early glaucoma.

Twenty-one patients, age 28 to 78 years, with elevated intraocular pressure (IOP) in one or both eyes, were examined with pattern-reversal electroretinograms (PERG), high-pass resolution perimetry (HRP), and conventional computer-assisted perimetry (CAP). Among the 42 eyes, 33 were hypertensive (IOP greater than or equal to 22 mmHg) and nine were normotensive (IOP less than or equal to 20 mmHg). The optic disc was judged abnormal in 14 of the hypertensive and one of the normotensive eyes. Fourteen abnormal PERGs and 19 abnormal HRPs were observed in the 33 hypertensive eyes. Conventional CAP gave abnormal results in three of the hypertensive eyes. Seven of the nine normotensive eyes were normal in all examinations. HRP was abnormal in one of the normotensive eyes and conventional CAP was abnormal in another. Thus, PERG and HRP showed a high incidence of optic nerve dysfunction in suspected or early glaucoma. These new methods should be clinically useful for diagnosis and management of conditions with increased IOP.

Pattern-reversal electroretinograms from normotensive, hypertensive and glaucomatous eyes.

Pattern-reversal electroretinograms (PERG) were recorded from 67 subjects, age 55-77 years, with normotensive (n = 19), hypertensive (n = 37) or glaucomatous (n = 11) eyes. The pathological intraocular pressure (IOP) ranged from 23 to 29 mm Hg in 21 eyes and from 30 to 43 mm Hg in 16 eyes. In 11 eyes (11 patients) manifest glaucoma was present (excavated optic disk, visual field defect). All examined subjects had normal visual acuity and clear optic media. The amplitude of the positive component of the PERG was measured. The mean PERG amplitude was 2.8 +/- 1.2 microV in the eyes with normal IOP (19 +/- 3 mm Hg), 2.2 +/- 1.0 microV in the eyes with moderately elevated IOP (26 +/- 2 mm Hg), 2.0 +/- 0.9 microV in the eyes with IOP above 30 mm Hg (33 +/- 4 mm Hg) and 1.1 +/- 0.6 microV in the glaucomatous eyes. Regression lines of PERG amplitudes versus age were calculated in all groups and showed a decrease in amplitude with increasing age. However, the correlation coefficients were not statistically significant. The decline with age was similar in all groups. The results indicate that the PERG amplitude is reduced in glaucomatous eyes and may be reduced also in ocular hypertension as well as with increasing age.

Visual acuity measurement using evoked potentials and fast Fourier transform.

Visual evoked cortical potentials (VECP) were recorded from 10 subjects with normal visual acuity (VA) 1.0. Reversing square-wave gratings of 16 different spatial frequencies were used as stimuli. In all 10 subjects significant increase in power at the stimulation frequency was observed in the Fourier spectrum. The VA, calculated from the Fourier spectra, ranged from 0.4 to 1.0. The described method for VA measurement is entirely objective, and the examination can be performed very rapidly and conveniently with the aid of a computer. However, the results indicate that the reliability of the measurement in individual cases may be doubtful.

Early diagnosis of retinal changes in diabetes: a comparison between electroretinography and retinal biomicroscopy.

The present study was undertaken in order to find out whether electroretinographic examinations could reveal signs of functional abnormalities before morphological changes are detected in the diabetic retina. Pattern-reversal and flash electroretinograms (ERG) and oscillatory potentials (OP) were recorded in 24 diabetics and 10 age-matched normal controls. The diabetic group consisted of 11 patients without retinopathy and 13 patients with background retinopathy. No significant changes in pattern-reversal or flash ERG or OP amplitudes were observed in the diabetic group with normal fundus or with background retinopathy. The findings imply that ERG examination with the described techniques does not reveal retinal dysfunction in diabetics before retinopathy can be detected by means of retinal biomicroscopy.

Pattern-reversal electroretinograms in ocular hypertension.

Pattern-reversal electroretinograms (ERGs) were recorded from seven patients, aged 50 to 69 years, with clinical diagnosis of unilateral ocular hypertension. In four of the seven patients the pattern ERG amplitude from the hypertensive eye was reduced below the normal level of variability, when compared with the amplitude from the opposite normotensive eye (ratio less than 0.8). In three of these four cases excavation of the optic disk in the hypertensive eye was observed 6 to 15 months after the recording of reduced pattern ERG. The finding suggests that pattern ERG may be an useful objective method for early detection of functional damage in eyes with increased intraocular pressure.

Preoperative electroretinograms and visual evoked cortical potentials for predicting outcome of vitrectomy in diabetics.

In order to find that the outcome of vitrectomy could be predicted in diabetics with very low visual acuity (finger counting at 3 m--approximately 20/400--or less), flash electroretinograms (ERG) and visual evoked cortical potentials (VECP) were simultaneously recorded from about 300 patients within one month before the operation. From this series two groups were formed, based on the outcome of surgery. One group (30 patients) had improved visual acuity, with finger counting at 0.1 to 1.0 m (20/200-20/20). The other group (29 patients) was unimproved by surgery. The groups were matched with regard to age, duration of diabetes, preoperative visual acuity and occurrence of cataract and previous panretinal photocoagulation. All patients had dense vitreal opacities, precluding inspection of the ocular fundus. Only patients without surgical and postoperative complications were included. There was a statistically significant (P less than 0.05) difference between the groups in ERG amplitude, but not in VECP latency or amplitude. Based on ERG amplitude, the outcome of vitrectomy could be predicted correctly in 36 of 59 patients (61%) and in 35 of 56 patients (63%) based on VECP latency. The VECP amplitude or the combination of ERG and VECP parameters did not improve the prediction rate. Thus, preoperative flash ERG and VECP can not safely predict the outcome of vitrectomy in diabetics with very low visual acuity.

Pattern-reversal electroretinograms and visual evoked cortical potentials in multiple sclerosis.

Pattern-reversal and flash electroretinograms (ERG) and visual evoked cortical potentials (VECP) were recorded from 15 patients with definite multiple sclerosis (MS). All patients had prolonged VECP latency, indicating demyelination of one or both optic nerves. The pattern-reversal ERG amplitude was reduced below the level of normal variation (mean -2 SD) in 11 of the 22 eyes with prolonged VECP latency and in one of the eight eyes with normal VECP latency. The mean pattern-reversal ERG amplitude from eyes with prolonged VECP latencies was significantly lower than the mean amplitude from the normal controls. No abnormalities were observed in the flash ERGs. Degeneration of retinal ganglion cell axons has been demonstrated in MS patients. The amplitude reduction in the pattern-reversal ERG, observed in some 50% of the eyes with prolonged VECP latencies, is supposed to reflect retinal ganglion cell dysfunction or degeneration secondary to demyelination of the optic nerve.

Oscillatory potentials, flash and pattern-reversal electroretinograms in amblyopia.

Oscillatory potentials (OP), flash and pattern-reversal electroretinograms (ERG) were recorded in 8 adult patients with amblyopia (visual acuity 0.3 or less) and 10 age-matched normal controls. No significant differences were observed in OPs between amblyopic and opposite eyes and normal controls. The pattern-reversal ERGs were significantly reduced in all amblyopic eyes. No significant side difference was found in the flash ERGs. The observed amplitude reduction in the pattern-reversal ERG might reflect dysfunction of the retinal ganglion cells, which have been supposed to be the main source of this type of ERG. No electrophysiological evidence could be demonstrated for a disturbed retinal function prior to the ganglion cell level.

Pattern-reversal electroretinograms in unilateral glaucoma.

Pattern-reversal and flash electroretinograms (ERG) and oscillatory potentials (OP) were recorded from 11 patients with unilateral glaucoma. All glaucomatous eyes had reduced amplitudes both compared to the opposite eye in the same patient and to reference values. In 10 of the 11 cases this reduction was below the level of normal variation. The difference in pattern-reversal ERG amplitude means from glaucomatous and opposite eyes was statistically significant. No differences were observed in flash ERGs or OPs. The histopathologic correlate to the visual field defects in glaucoma is retinal ganglion cell degeneration. The present electrophysiologic findings support the view, based on results from animal experiments, that the pattern-reversal ERG reflects ganglion cell activity.

Pattern-reversal electroretinograms in squint amblyopia, artificial anisometropia and simulated eccentric fixation.

Pattern-reversal electroretinograms were recorded in 10 normals and 10 adult patients with squint amblyopia (visual acuity 0.3 or less). The effects of artificial anisometropia and simulated eccentric fixation were tested in normals. The pattern-reversal ERG amplitude was reduced linearly with increased defocusing (0 to + 3 D). A significant amplitude reduction was observed when defocusing amounted to + 1 D. The amplitudes were not reduced below the range of normal variability at 4 degrees of simulated eccentric fixation. In the amblyopia patients, refractive errors were corrected. None had eccentric fixation of more than 4 degrees. Yet, the pattern-reversal ERGs were lower in the amblyopic eyes compared with the opposite normal eyes. The difference in amplitude means was statistically significant. The finding supports the view that retinal function is impaired in human squint amblyopia.