Fundus reflectance--historical and present ideas

In 1851 Helmholtz introduced the ophthalmoscope. The instrument allowed the observation of light reflected at the fundus. The development of this device was one of the major advancements in ophthalmology. Yet ophthalmoscopy allows only qualitative observation of the eye. Since 1950 attempts were made to address the challenging, quantitative assessment of the amount of light reflected by the fundus. At first, only comparative measurements were possible, applied in the study of macular and visual pigments. With improvements in light detecting techniques, and with the advent of microprocessors, the measurement of spectral and spatial distribution of the reflectance became feasible. This led to the development of models that explained the observed wavelength dependence and the directional behavior of light reflected from the fovea. The models allowed a quantitative assessment of many parameters on absorption and reflection by structures in the human eye. This paper provides a review of both the experimental and theoretical progress, and summarizes the results of fundamental and clinical research using fundus reflectometry.

Clinical applications of pupillography

The development of personal computer-based infrared video instruments has allowed pupillography to enter the clinical arena. Measuring pupil diameter for refractive surgery, distinguishing Horner syndrome from physiologic anisocoria, quantifying the relative afferent pupillary defect, and plotting visual fields by means of graded pupil constriction to focal light stimuli are recent applications in ophthalmology. Pupillography has also been used to determine sleepiness and autonomic effects of new pharmaceuticals.

Seed-less iodine-125 ophthalmic applicator

A method of preparation a seed-less active insert of iodine-125 ophthalmic applicator is described. Internal electrolysis was applied for fixing iodine-125 on the concave surface of the silver shell which is afterwards hermetically sealed inside a spherically shaped acrylic insert. The current-voltage characteristics of the galvanic cell used for deposition of silver iodide were determined. The results of the measurements of the energy spectra of the radiation emitted by a seed-less and seed-containing applicator are presented. The iodine-125 surface distribution uniformity on a silver shell was measured. The depth dose rate measurements indicate that the total activity incorporated in a seed-less applicator can be lower than that in seed-containing, while simultaneously assuring the desired dose rate.

[The evaluation of accommodation range in patients of various age groups by WASCA wavefront aberrometer]

PURPOSE

The aim of this study was, to analyse the results of accommodation range measurement obtained in groups of patients of different age. Wavefront aberrometer was used for evaluation of accommodation range of the patients eyes.

MATERIAL AND METHODS

The accommodation range was analysed in 200 eyes in 100 patients. The examined group of patients was divided into 4 groups, depending on the patients age. GROUP I--AGE: 20-30 years old; group II--age: 31-40 years old; group III--age: 41-50 years old; group IV--age: 51-60 years old. The measurements were analysed using WASCA System depend on: refractive error, sex and difference of pupil diameter for far and near vision.

RESULTS

Different ranges of accommodation were obtained. We did not observe any correlation between the accommodation range and the sex and refractive error. We noticed statistically significant differences between the accommodation range and pupil diameter, as well as the patients' age.

CONCLUSIONS

The WASCA System is a device, which can be used for analysis of accommodation range. This system gives us the possibility, to trace changes of eye accommodation range in the long period of time.

Low vision rehabilitation in patients with age-related macular degeneration at a tertiary eye care centre in southern India

PURPOSE

To evaluate the specific needs and types of low vision devices (LVDs) in patients with age-related macular degeneration (AMD) so as to use the residual vision effectively.

METHODS

One hundred consecutive patients with diagnosis of AMD were evaluated to ascertain the degree of visual disability. Different LVDs were used to suit the specific needs of individual patients. The distribution of LVDs for distance and near and other rehabilitation measures were stratified for vision >or=6/18 and <6/18. Statistical analysis was performed using chi2 test/Fisher's exact test and paired t-test.

RESULTS

The percentage of patients with visual acuity <6/18 reduced from 72.2% (26/36) to 47.2% (17/36) with the use of standard spectacles (P = 0.03). Similarly, the percentage of patients with visual acuity <6/18 reduced from 85.7% (6/7) to 14.3% (1/7) with the use of a telescope (P = 0.029). The optical devices for near tasks included spectacle magnifiers (n = 59), stand magnifiers (n = 19), and hand magnifiers (n = 18). With these LVDs, the near vision improved from 0.13 (decimal notations) to 0.39 (P < 0.001). Eighty-six patients were given at least one of the LVDs and 20% were prescribed more than one near device (bifocals, spectacle magnifiers, hand magnifiers, stand magnifiers). Additionally, patients also needed counselling (n = 89) and training on eccentric viewing (n = 39), coin identification (n = 45), and independent mobility (n = 41).

CONCLUSION

The overall management of a patient with AMD must include counselling, prescription of appropriate LVDs and training to utilize the residual vision to its fullest advantage. This is expected to improve the patient's quality of life.

A novel technique for harvesting keratolimbal allografts from corneoscleral buttons

PURPOSE

To describe a method for obtaining partial-thickness keratolimbal allografts from corneoscleral buttons to be used in corneal limbal stem cell transplantation.

DESIGN

Description of device design and technique for use.

METHODS

Cyanoacrylate tissue adhesive, placed on the posterior side of a trephinated corneoscleral rim, is used to secure the allograft to a disposable acrylic sphere that is attached to a cylindrical base.

RESULTS

After fixation of the corneoscleral rim to the acrylic sphere, keratolimbal allograft harvesting is performed as a continuous strip dissection with a 65 Beaver blade. This technique minimizes trauma to the epithelial stem cells, provides excellent stability of the corneoscleral rim during harvesting, and preserves the central corneal button.

CONCLUSIONS

This method for obtaining keratolimbal allografts effectively provides tissue stabilization during harvesting, minimizing epithelial stem cell trauma and eliminating the need for whole donor globes.

The effect of an eyelid speculum on intraocular pressure measurement in children

PURPOSE

To assess the effect of a pediatric eyelid speculum on the measurement of intraocular pressure (IOP) in children.

DESIGN

Observational case series.

METHODS

Intraocular pressure measurements were performed during examination under anesthesia immediately after induction. The measurements were made with and without a pediatric eyelid speculum in place.

RESULTS

Intraocular pressure measurements were made in 77 eyes of 45 consecutive children. The mean IOP without the speculum was 16.33 mm Hg in the right eye and 16.55 mm Hg in the left eye. With the lid speculum in place the mean IOP was 20.26 mm Hg in the right eye and 20.05 mm Hg in the left eye (P <.05).

CONCLUSIONS

The presence of an eyelid speculum raised IOP an average of 4 mm Hg. This effect should be considered when interpreting IOP measurements in children.

Hand-held digital video-camera for eye examination and follow-up

We developed a hand-held digital colour video-camera for eye examination in primary care. The device weighed 550 g. It featured a charge-coupled device (CCD) and corrective optics. Both colour video and digital still images could be taken. The video-camera was connected to a PC with software for database storage, image processing and telecommunication. We studied 88 normal subjects (38 male, 50 female), aged 7-62 years. It was not necessary to use mydriatic eye drops for pupillary dilation. Satisfactory digital images of the whole face and the anterior eye were obtained. The optic disc and the central part of the ocular fundus could also be recorded. Image quality of the face and the anterior eye were excellent; image quality of the optic disc and macula were good enough for tele-ophthalmology. Further studies are needed to evaluate the usefulness of the equipment in different clinical conditions.

Measuring corneal power for intraocular lens power calculation after refractive surgery. Comparison of methods

PURPOSE

To find a more accurate and predictable method for intraocular lens (IOL) power calculation in eyes after refractive surgery.

SETTING

Department of Ophthalmology, Kangnam St. Mary's Hospital, Seoul, Korea.

METHODS

The accuracy of the following methods for calculating IOL power in 132 eyes after PRK or LASIK was compared: manual keratometry, hard contact lens, refraction-derived keratometry at the corneal plane, and the refraction-derived keratometry at the spectacle plane. Based on this comparison, the IOL power was calculated in the 2 eyes of a patient using refraction-derived keratometry at the spectacle plane with the SRK II formula. Cataract surgery with IOL implantation was then performed.

RESULTS

The largest corneal power values were obtained using a manual keratometer and the smallest using refraction-derived keratometry at the spectacle plane (P <.001). In the patient having cataract surgery with IOL implantation, near target refraction was achieved with minimal error in IOL power.

CONCLUSIONS

If the corneal power is known before refractive surgery, the use of the smallest value of those obtained using refraction-derived keratometry and the hard contact lens method is recommended. However, if the corneal power before refractive surgery is unknown, the use of the hard contact lens method is recommended.

Comparison of scotopic pupil measurement with slitlamp-based cobalt blue light and infrared video-based system

PURPOSE

To determine the accuracy and reproducibility of scotopic pupil measurements with a slitlamp-based cobalt blue light.

SETTING

University of Texas Health Science Center-San Antonio, San Antonio, Texas, USA.

METHODS

In a prospective experimental study, 2 independent observers measured 16 subjects' pupils with a standard slitlamp-based cobalt blue light. In the same setting, the accuracy and reproducibility of the measurements were compared with those obtained with an infrared video-based system.

RESULTS

Measurements of pupil size using the infrared video-computer system were highly reproducible. With the slitlamp-based cobalt blue light, the 2 measurements obtained by observer 2 (n = 16) were very close to each other (mean difference 0.09 mm +/- 0.23 [SD]; P =.12), whereas those obtained by observer 1 (n = 16) were slightly different from each other (mean difference 0.18 +/- 0.33 mm; P =.043). The mean pupil diameter measured with cobalt blue light was not significantly different between the 2 observers (P >.05), and the measurements were highly correlated with each other (r = 0.96, P <.01). The mean difference between the measurements using cobalt blue light and the infrared video-computer system was 0.21 +/- 0.54 mm for observer 1 (P =.47) and 0.06 +/- 0.47 mm for observer 2 (P =.85). Good correlation was noted between the measurements taken from each measuring device for both observers (r = 0.87 and 0.90, P <.01).

CONCLUSIONS

Slitlamp-based cobalt blue light provided a reasonably good measurement of scotopic pupil size. It correlated well with the infrared video system when used at the lowest setting by experienced personnel. However, the observed difference between the measurements obtained by the 2 devices indicates that the cobalt blue light should be used cautiously in the refractive surgery preoperative evaluation of patients with large pupils.

[Orbscan: a new device for iridocorneal angle measurement]

PURPOSE

To evaluate the accuracy and reproducibility of iridocorneal angle measurement obtained with a slit-lamp method (Orbscan).

METHODS

The iridocorneal angle was measured in 100 normal eyes of 50 patients using the Orbscan II device. Angles were measured in eight meridians using both the "plane" and "polynomial" modes. For each eye, two exams were taken successively and the reproducibility was calculated by analyzing the difference between both measurements. Angle value was correlated with subjective spherical equivalent and other biometric measurements obtained by Orbscan (i.e., anterior chamber depth, axial length, corneal diameter).

RESULTS

Reproducibility of the angle measurement was significantly better with the plane mode than with the polynomial mode (5.4%+/-4.7 versus 7.2%+/-6.2; p<0.001). Reproducibility significantly varied with localization (p<0.001). Significant differences were found between reconstruction modes (49.3 degrees +/-4.6 degrees for plane mode versus 42.8 degrees +/-6.7 degrees for the polynomial mode; p<0.001) and according to localization (p=0.02). Correlation with the other biometric measurements was higher for the plane mode than for the polynomial mode. Angle measurement with the plane mode showed significant correlation with subjective spherical equivalent (r(s)=-0.59; p<0.001), the anterior chamber depth measurement (r(s)=-0.74; p<0.001), the axial length measurement (r(s)=-0.34; p<0.002), and the corneal diameter measurement (r(s)=-0.34; p<0.002).

CONCLUSION

The iridocorneal angle measure obtained with the plane mode showed high reproducibility and it significantly correlated with clinical parameters. It appears to be useful for clinical application.

Clinical evaluation of refraction using a handheld wavefront autorefractor in young and adult patients

PURPOSE

To determine the accuracy of measurement by the SureSight autorefractor (software version 2.0) and the influence of accommodation.

SETTING

Pediatric Section, Department of Ophthalmology, University of Hamburg, Hamburg, Germany.

METHODS

In a series of comparative measurements, autorefractor readings were compared with cycloplegic retinoscopy in 195 eyes of 108 patients (1 to 81 years) measured under cycloplegia. Ninety-six eyes were also measured without cycloplegia.

RESULTS

The wavefront autorefractor was able to refract human eyes from a distance of 0.35 m. The accuracy was lower than that with conventional tabletop autorefractors. A difference of less than 0.51 diopter (D) was found in 68% of the spherical equivalents under cycloplegia. Many emmetropic and hyperopic children accommodated during the noncycloplegic measurements and were minus-overcorrected up to -6.13 D. In our group of young patients (2 to 17 years), 47% were minus-overcorrected by more than -2.00 D.

CONCLUSIONS

The wavefront autorefractor uses a new method to determine the refractive state of the eye from a distance. It was less accurate than other conventional autorefractors. A benefit is its application in infants and disabled and uncooperative subjects. Cycloplegia is necessary in young hyperopic patients.

Does glaucoma medication influence the diameter of the retinal arteriole in the human eye? (A pilot study using the retinal vessel analyser)

PURPOSE

To investigate the potential in vivo influence of different topical glaucoma medications on the diameter of the retinal arterioles of healthy volunteers and glaucoma patients.

METHODS

The diameter of one pre-selected retinal arteriole per eye was measured using the Retinal Vessel Analyser (RVA), an instrument developed for non-invasive clinical measurement of the diameter of the main retinal vessels. The instrument contains a video system, and the integrated software recognises the boundaries of the retinal vessels by detecting their light-transmission profile. The vessel diameter (in arbitrary units) is plotted against time (seconds) on a separate display screen. In Study I the vessel diameter was measured in 12 eyes of six healthy volunteers (age 21-26 years, mean age 24.0 years) on six occasions each separated by 14 days. In a double-masked fashion, each subject's right eye was treated with one of 5 glaucoma medications (brinzolamide 1%, timolol 0.5%, betaxolol 0.5%, brimonidine 0.2% or latanoprost 0.005%) and the left eye always received balanced salt solution. In Study II, one randomly selected eye of 16 patients (age 50-79 years, mean age 65.2 years) suffering from primary open-angle glaucoma controlled with topical monotherapy was investigated, in an unmasked fashion. Four patients were on betaxolol 0.5% treatment, six subjects were receiving non-selective topical beta receptor blockers and six subjects were being treated with once daily latanoprost 0.005%.

RESULTS

The coefficient of variation for the arteriole diameter in the healthy volunteers was less than 12% in each case. No significant post-treatment change of the diameter of the pre-selected arteriole was found for any topical medication investigated, either in the healthy volunteers (Study I) or in the patients suffering from glaucoma (Study II) (p>0.05, paired t-test). In addition, in Study I no difference was observed in the alteration of the arteriole diameter between the baseline and the hour 2 measurements when the values from the drug-treated and placebo treated eyes were compared (p>0.05, two-way ANOVA).

CONCLUSION

In the present investigations it was not possible to detect any statistically meaningful change of the arteriole diameter at two hours after the instillation of any of several topical antiglaucoma drugs widely used in clinical practice. Further investigations are necessary to clarify whether the lack of observed change is due to the lack of retinal vascular effects of the drugs investigated, or is due to an inability of the RVA instrument in practice to detect alterations between time-points separated by several hours.

[Diode lasers in ophthalmic surgery]

The paper outlines current aspects of the use of diode lasers in ophthalmology. The Ufa Research Institute of Eye Diseases is the first in Russia to develop and use endoscopic cyclic laser coagulation and laser endoscopic antegrade dacryocystorhinostomy. The introduction of new laser microendoscopic technologies into practical ophthalmology has increased the efficiency of ophthalmological care in the treatment of patients with non-compensated glaucoma and lacrimal duct diseases.

Simultaneous measurement of foveal spectral reflectance and cone-photoreceptor directionality

An instrument for simultaneous measurement of foveal spectral reflectance and cone-photoreceptor directionality is described. The key element is an imaging spectrograph (spectral range of 420-790 nm) with its entrance slit conjugate to the pupil plane of a human eye. A 1.9-deg spot on the retina is sampled in 1 s. Video observation of the retina and the pupil facilitates proper alignment. Measurements were performed on 21 healthy subjects. Model analysis of the spectra provided densities of photostable ocular absorbers. As an example, macular pigment and melanin are discussed in more detail. Spatial profiles exhibited the optical Stiles-Crawford effect, reflecting cone-photoreceptor directionality.

A portable instrument for measuring macular pigment with central fixation

PURPOSE

To evaluate the reliability and validity of a portable instrument for measuring macular pigment optical density.

METHODS

The instrument is small, uses light emitting diodes as light sources and the principles of heterochromatic flicker photometry of comparing foveal and extra-foveal minimum flicker matches. It uses central fixation for the extra-foveal matches, which subjects found easier than eccentric fixation. Subjects with healthy eyes used the instrument to measure their pigment density in a number of eye clinics.

RESULTS

The mean pigment density in 124 eyes in 124 individuals was 0.41 +/- 0.16 (mean +/- SD), there was no significant change with age but the density was less in females, those with light irides, smokers, subjects on diets low in precursor carotenoids and in those exposed to several hours of daylight every day or who used sun beds.

CONCLUSIONS

The portable instrument gave valid and reliable data that confirmed published values for macular pigment. It was convenient to use in the clinic and has potential as a screening tool.

The use of the Naugle orbitometer in maxillofacial trauma

BACKGROUND AND OBJECTIVES

Objective measuring of globe position is not a universal practice in the management of orbital trauma. Few studies in the literature advocate its routine use.

METHODS AND MATERIALS

The Hertel exophthalmometer is the most widely used instrument; however, in trauma involving the lateral orbital rim (e.g., in zygoma fractures), the results are inaccurate because the displacement of the zygomatic bone interferes with its reference point on the lateral orbital rim. A more recent measuring device, the Naugle orbitometer, was introduced in 1992. It uses the superior orbital rim (frontal bar) and inferior orbital rim (malar eminence) as reference points.

RESULTS AND/OR CONCLUSIONS

This article reports experience with this instrument in objective measuring the position of the globe in orbital trauma. These measurements are used 1) to monitor fractures that may not require repair but should be followed and observed for dystopia or enophthalmos, 2) to determine the adequacy of fracture repair, and 3) to determine the volume adjustment required for correcting enophthalmos. Future studies will be directed to compare the accuracy of Naugle and Hertel exophthalmometers.

The stamler lid splint: a new short-term technique for achieving therapeutic ptosis

PURPOSE

To provide an introduction to a new device, the Stamler lid splint (SLS), a disposable appliance designed to create a temporary total therapeutic ptosis. We also describe the indications for its use and analyze its limitations.

METHODS

The utility of the SLS in effecting complete ptosis was examined in 33 patients. Outcome parameters examined were mean duration of (induced) ptosis, success (and failure) rate, and the incidence of side effects.

RESULTS

The most common indications for using the SLS were lid closure abnormalities (n = 6) and epithelial defects after keratoplasty (n = 5). The induced ptosis lasted for a mean of 3.3 days (range, 1.5-6). The success rate of the SLS in achieving a total ptosis was 90.9%. Failure was attributed to the presence of atypical lid or orbital anatomy. No patient developed a complication specifically related to the SLS itself.

CONCLUSIONS

The SLS is an inexpensive, quick, and technically straightforward means of treating a variety of ocular surface disorders in compliant patients with normal lid and orbital anatomy. The SLS is best suited to patients who require short-term therapy only.

A new non-contact optical device for ocular biometry

BACKGROUND

A new commercially available device (IOLMaster, Zeiss Instruments) provides high resolution non-contact measurements of axial length (using partial coherent interferometry), anterior chamber depth, and corneal radius (using image analysis). The study evaluates the validity and repeatability of these measurements and compares the findings with those obtained from instrumentation currently used in clinical practice.

METHOD

Measurements were taken on 52 subjects (104 eyes) aged 18-40 years with a range of mean spherical refractive error from +7.0 D to -9.50 D. IOLMaster measurements of anterior chamber depth and axial length were compared with A-scan applanation ultrasonography (Storz Omega) and those for corneal radius with a Javal-Schiötz keratometer (Topcon) and an EyeSys corneal videokeratoscope.

RESULTS

Axial length: the difference between IOLMaster and ultrasound measures was insignificant (0.02 (SD 0.32) mm, p = 0.47) with no bias across the range sampled (22.40-27.99 mm). Anterior chamber depth: significantly shorter depths than ultrasound were found with the IOLMaster (-0.06 (0.25) mm, p <0.02) with no bias across the range sampled (2.85-4.40 mm). Corneal radius: IOLMaster measurements matched more closely those of the keratometer than those of the videokeratoscope (mean difference -0.03 v -0.06 mm respectively), but were more variable (95% confidence 0.13 v 0.07 mm). The repeatability of all the above IOLMaster biometric measures was found to be of a high order with no significant bias across the measurement ranges sampled.

CONCLUSIONS

The validity and repeatability of measurements provided by the IOLMaster will augment future studies in ocular biometry.

[The price of success - informatics in ophthalmology]

Medicine and engineering seemed to be until now two so different field that have nothing in common. By the present, we have tried to show, how to make your work easier and perform, being helped by an application named OPTILINK, which combine so successfully those two fields. Also, in this paper work we have presented the way this application work and all the apparatus you need for. OPTILINK means working directly with an application engineer who not only understand your needs, but can also help you specify affordable opto-mechanical components to meet those needs.

Raman spectroscopy in ophthalmology: from experimental tool to applications in vivo

Raman spectroscopy is a qualitative and quantitative optical technique for determining the molecular composition of matter. Improvements in spectroscopic instruments, especially the modality to detect low light level signals extended the Raman technique to biomedical applications, even in delicate structures like the eye. The purpose of this paper was to make an inventory of performed applications of Raman spectroscopy in biomedical science and especially in ophthalmology. A literature search was done using Medline, Current Contents, a patent server on the Internet, and references found in articles and patents. This search revealed a variety of Raman techniques and applications in biomedical research, and an increasing flow of articles starting in the late 1970s on Raman spectroscopy in ophthalmology. This increase in literature about Raman spectroscopy in ophthalmology feeds the expectation that this valuable technique will be introduced in the future into clinical practice.

Evaluation of the validity and reliability of A-scan ultrasound biometry with a single use disposable cover

BACKGROUND

The UK Medical Devices Agency has suggested that ophthalmic practitioners should, where practicable and not compromising clinical outcome, restrict corneal contact devices to single patient use to minimise a remote theoretical risk of transmission of new variant Creutzfeldt-Jakob disease (vCJD). This study reports on a modified technique of ultrasound A-scan biometry that complies with the MDA recommendations.

METHODS

The right eyes of 37 consecutive hospital patients had a series of biometry readings taken with a Humphrey 820 A-scan instrument with a plane wave transducer use d conventionally and with the addition of a disposable latex cover.

RESULTS

Intrasessional repeatability of axial length measurements was similar for conventional readings--mean difference 0.027 mm, 95% confidence intervals (CI) +/- 0.44 mm and those taken with a disposable cover (0.028 mm, CI +/- 0.38). Intersessional repeatability was equivalent with (0.002 mm, CI +.- 0.51) and without a cover (0.03 mm, CI +/- 0.51). Readings with a cover were not significantly different from those without (paired t test; p >0.05), but tended to be greater (mean difference 0.085 mm, CI +/- 0.60).

CONCLUSIONS

These findings suggest that corneal contact biometry with a disposable cover is a viable and theoretically safer alternative to the conventional technique.

Eye health care in the Czech Republic

OBJECTIVE

An analysis of eye health care in the Czech Republic as of 1998 was performed.

METHODS

A questionnaire was used to obtain information from all 59 in-patient eye departments.

RESULTS

The number of ophthalmologists per 1 million inhabitants was 95. The number of cataract operations per 1 million inhabitants was 4,209: phaco-emulsification (36,926 surgeries, 85.2%), extracapsular extraction (6,094 surgeries, 14.1%) and intracapsular extraction (90 surgeries, 0.2%). Intra-ocular lenses were implanted in 99% of cases; 404 corneal transplantations and 1,220 operations for retinal detachment were performed. The number of pars plana vitrectomies for diabetic eye complications was 661.

CONCLUSION

Selected regional clinical centres should be equipped and preferred by health insurance companies to provide comprehensive eye health care services and training.

Assessment of ocular counterroll during head tilt using binocular video oculography

PURPOSE

According to recent literature, the presence and the amount of true compensatory ocular counterroll is still debatable. The purpose of the current study was to assess compensatory counterroll in response to lateral head tilt using a new noninvasive recording technique, and, furthermore, to find out whether the amount of counterroll is influenced by the presence or absence of spatial orientation.

METHODS

Eye movement recordings were performed using the infrared three-dimensional video oculography (3D-VOG) technique. Objective cycloposition of five healthy individuals was measured in presumed primary position and in head tilt positions of 15 degrees, 30 degrees, and 45 degrees to the right and left. The same paradigm was performed under three viewing conditions: binocularly without spatial orientation and both binocularly and monocularly with spatial orientation.

RESULTS

A consistent ocular counterroll corresponding to the amount of head tilt was observed in all subjects. Maximum torsional amplitude was 10 degrees at a 45-degree head tilt. The relative amount of compensation ranged between 13% and 22% of the actual head tilt, decreasing with increasing head tilt. Compensatory counterroll and torsional conjugacy between both eyes revealed minor differences between the experimental paradigms. Incomplete cycloductional reorientation in primary position after head tilt was detected in all subjects, regardless of the stimulus.

CONCLUSIONS

A consistent compensatory ocular counterroll was demonstrated in response to static lateral tilting of the head in healthy individuals. The amplitude of counterroll and the gain of compensatory cycloversion were higher than has been generally reported. Infrared 3D-VOG technique was a reliable and comfortable method for the assessment of ocular cycloduction. It can be considered to be a promising tool for advanced evaluation of disturbances of the oblique eye muscles.

Accuracy of IRAS GT interferometer and potential acuity meter prediction of visual acuity after phacoemulsification: prospective comparative study

PURPOSE

To assess and compare the accuracy of 2 methods of predicting visual acuity after phacoemulsification.

SETTING

Department of Ophthalmology, Montpellier, France.

METHODS

This prospective study evaluated 47 eyes of 47 patients having uneventful phacoemulsification over a 1-month period. All the patients had mild to moderate cataract. Visual acuity recovery was predicted using the white-light IRAS GT interferometer on the 3- and 8-degree wide test area and the Guyton-Minkowski potential acuity meter (PAM). Best corrected visual acuity was evaluated 1 day before and 1 month after surgery.

RESULTS

Both the interferometer and PAM underestimated the retinal visual capacity. Three-degree white-light interferometry gave significantly better mean predicted results than 8-degree interferometry and the PAM. There was no statistically significant disparity between predicted and postoperative results with 3-degree interferometry (1.04 +/- 0.57 logMAR; -0.09 +/- 0.27 decimal) (P =.0647) and a statistically significant disparity with 8-degree interferometry (0.89 +/- 0.59 logMAR; -0.13 +/- 0.27 decimal) and the PAM (0.66 +/- 0.62 logMAR; -0.22 +/- 0.24 decimal) (P =.0001). The predicted values were widely dispersed; the correlation indices were 0.38 with the PAM (P =.091), 0.39 with 3-degree interferometry (P =.001), and 0.49 with 8-degree interferometry (P =.0005).

CONCLUSIONS

Three-degree white-light interferometry gave more accurate results than 8-degree interferometry and the PAM. The wide dispersion of results and unsatisfactory correlation indices show the tests are poor predictors of individual acuity. They should be used semiquantitatively and the results interpreted in relation to the clinical data. Qualitative methods may be useful in confirming or refuting visual recovery capacity ascertained by quantitative systems.

Putting retinal exams for diabetics in the primary care arena

Only about half of all diabetics get their recommended annual eye exams. Until now, little progress has been made in boosting the number of diabetics who are compliant in getting this annual exam done. However, a new device that enables the exams to be completed in the PCP's office is getting rave reviews from early users.

Non-cycloplegic screening for amblyopia via refractive findings with the Nikon Retinomax hand held autorefractor in 3 year old kindergarten children

AIMS

To assess non-cycloplegic screening for amblyopia with the hand held Nikon Retinomax autorefractor in 3 year old kindergarten children.

METHODS

427 three year old children were examined in kindergarten with the Retinomax without cycloplegia. A gold standard was established in all children by two orthoptic examinations in kindergarten. If there were missing, abnormal, or inconsistent findings, children were referred for ophthalmological examination. If, by the ophthalmological examination, a new case of amblyopia requiring treatment was diagnosed, the gold standard was set "positive."

RESULTS

In 404 children the gold standard was obtained. 10 children (2.5%) had a "positive" gold standard of unknown and untreated amblyopia. Screening sensitivity was 0.80, specificity 0.58, accuracy 0.58, and the likelihood ratio 1.89.

CONCLUSION

Non-cycloplegic refractive screening with the Retinomax led to many false positive referrals due to instrument myopia and "inconclusive" results. Hence specificity, accuracy, and the likelihood ratio were too low to conduct screening effectively.

Teleophthalmology link between a primary health care centre and a reference hospital

We have evaluated a teleophthalmology service linking a primary health care centre and an eye clinic at a reference hospital. General practitioners at the primary care centre serving a population of 15,000 and ophthalmologists at the reference hospital participated in this study. Eye fundus digital images were taken from 278 eye fundi of 139 consecutive patients with clinical conditions that could potentially produce fundus alterations. Fundus images were obtained with a non-mydriatic fundus camera (Canon CR6-45M) and were electronically sent reference hospital where ophthalmologist inspected the images and returned the diagnosis. In 18 patients (13%) the images did not have good enough quality to exclude eye fundus lesions. In 24 patients (17%) clear eye fundus alterations were found in at least one eye. In 14 patients (10%) there were image features suggesting retinal alterations that could not be confirmed by image inspection. Media opacity (13 eyes, 5%, seven patients, 5%) was the most common cause of poor image quality. The most difficult assessment was the evaluation of optic nerve head cupping. Retinal oedema was not observable in the digital images. In our experience teleopthalmology services seem to be an effective alternative for eye fundus diagnosis and patient follow-up.

Effect of pneumatic suction ring placement on intraocular pressure in cats

PURPOSE

To determine the effect of placing a pneumatic suction ring on intraocular pressure (IOP) in the cat and to design an improved method to generate a stable elevation of IOP.

METHODS

A pneumatic suction ring was applied to the eye in cats while the IOP was monitored. Three groups of animals (10 per group) were used. A vacuum pressure of 450 mbar was applied in one step to eyes of group 1 (anesthetized) and to group 2 (euthanized) cats. In group 3 (anesthetized) cats, an initial vacuum pressure of 250 mbar was applied, followed by a vacuum of slowly increasing pressure at a rate of 5 mbar/min for a total of 40 min to 450 mbar.

RESULTS

After the one-step application of a vacuum (450 mbar) to the eyes of anesthetized cats (group 1), IOP peaked within the first minute from a basal value of 25 +/- 2 mm Hg (mean +/- SD) to 90 +/- 7 mm Hg. It then rapidly decreased to 69 +/- 2 mm Hg 5 min later and continued to decrease to 39 +/- 4 mm Hg 40 min later. This sharp peak and decline of IOP were also observed in eyes of euthanized cats (group 2). The basal IOP of these eyes was 8 +/- 1 mm Hg. It rose to 18 +/- 2 mm Hg immediately after the application of vacuum pressure (450 mbar) and returned to the basal level 5 min later. In contrast, the eyes of group 3 receiving an initial vacuum of 250 mbar followed by a 5 mbar/min vacuum increment exhibited a rapid increase in IOP and a very stable plateau (mean IOP = 62-68 mm Hg), lasting the whole study period (40 min).

CONCLUSION

IOP after a one-step application of a vacuum via a pneumatic suction ring is self-adjusting and declines rapidly over time. This decline in IOP can be overcome by a supplementary increment in vacuum pressure.

[Ocular biometric measurements with a slit-lamp method (Orbscan)]

PURPOSE

To evaluate the accuracy and reproducibility of the biometric measurements obtained with the Orbscan((R)) device in normal eyes.

METHODS

Anterior chamber depth, axial length, and corneal diameter were studied in 50 normal eyes of 25 patients using the Orbscan((R)) device and A-Scan ultrasonography. For each eye, two exams were done successively and reproducibility was calculated by analyzing the difference between both measurements.

RESULTS

The reproducibility of anterior chamber depth and corneal diameter measurements obtained by Orbscan((R)) was high (respectively 0.721.25% and 0.831.40%). The anterior chamber depth measurements by Orbscan((R)) and A-Scan ultrasonography were strongly correlated (rs=0.92;p<0.001). The axial length measurement obtained with the Orbscan((R)) device was less reproducible (3.554.11%). For the axial length, the Orbscan((R)) measurements and A-Scan ultrasonography measurement was poorly correlated. (rs=0.64; p<0.001).

CONCLUSION

The anterior chamber depth measurement obtained with the Orbscan((R)) device showed high reproducibility and it was strongly correlated with the measurement obtained by A-Scan ultrasonography. Axial length measurement obtained with the Orbscan((R)) device was less reproducible and poorly correlated with the A-Scan ultrasonography measurement. It was not relevant for clinical application.

Reliable measurement of mouse intraocular pressure by a servo-null micropipette system

PURPOSE

To develop a reliable technique for measuring intraocular pressure (IOP) in the mouse.

METHODS

An electrophysiologic approach-the servo-null micropipette system (SNMS)-for measuring hydrostatic pressure was adapted for the mouse eye. Fine-tipped (5 microm in diameter) micropipettes were advanced across the cornea with a piezoelectric micromanipulator, and the IOP was continuously monitored for up to 46 minutes.

RESULTS

The micropipette tip was visualized in the anterior chamber. With the SNMS, the IOP of black Swiss outbred mice under ketamine anesthesia was 17.8 +/- 0.4 mm Hg, higher than values previously estimated in inbred mouse strains by a larger bore microneedle manometric technique. After withdrawal of the micropipette, a second penetration led to a similar level of IOP. Hypotonic solutions increased and hypertonic solutions decreased IOP. Drugs that decrease inflow (acetazolamide, timolol) or increase outflow facility (pilocarpine, latanoprost) in primates and humans lowered steady state IOP in the mouse. The transient initial increase in IOP produced by pilocarpine reported in other animals was also observed in the mouse. Xylazine-ketamine anesthesia lowered IOP substantially in comparison with systemic anesthesia with either ketamine or tribromoethanol alone.

CONCLUSIONS

The SNMS is the first reliable, reproducible method for measuring mouse IOP. The mouse IOP is sensitive not only to drugs known to reduce aqueous humor inflow but also to drugs that increase aqueous humor outflow facility in the eyes of primates and humans. The development of the SNMS is an enabling step in the use of the mouse for glaucoma research, including molecular genetics, molecular pharmacology, and the search for novel antiglaucoma drugs.

Tritan colour contrast sensitivity function in refractive multifocal intraocular lenses

AIMS

To compare tritan colour contrast sensitivity (CCS), without and with glare, in patients with refractive multifocal intraocular lenses (IOLs) and with monofocal intraocular lenses.

METHODS

Tritan CCS was determined (Moorfields Vision System, CH Electronics) in 15 eyes (14 patients, 75.7 (+/-6.6) years) with a refractive multifocal IOL (Allergan SA 40N) and in 11 eyes (10 patients, 73.7 (+/-6.4) years) with a monofocal IOL (Allergan SI 40 NB). Measurements were made monocularly under mesopic conditions at a distance of 2 metres from the monitor with best distance refraction plus 0.5 D at 0.5, 1, 3, 6, 11.4, and 22.8 cycles per degree (cpd). The test was then repeated for the multifocal IOLs, adding minus 2.5 D to the best distance refraction to force the patient to use the near focus. Both lenses were also investigated under glare conditions with the same set-up and using the brightness acuity tester (BAT).

RESULTS

The tritan CCS function without glare in multifocal lenses through the distance focus was nearly identical to that through the near focus. The following statistically significant differences were measured: the CCS function without glare for the multifocal lens was worse at 0.5 cpd and 1.0 cpd than that of the monofocal lens. In CCS testing of the multifocal group with glare at 6 cpd, the results through the distance focus were better than the results through the near focus. For the CCS function with glare, the values for the distance focus in the multifocal lens were worse than the values for the monofocal lens at 0.5 cpd and 1 cpd. In CCS testing with glare through the near focus and CCS testing through the monofocal lens, the monofocal lens performed better at 0.5 cpd, 1 cpd, 3 cpd, and 6 cpd.

CONCLUSION

Refractive multifocal intraocular lenses influence tritan CCS function compared to monofocal lenses.

Clinical evaluation of the Shin-Nippon SRW-5000 autorefractor in children

The Canon Autoref R-1 is an 'open-field' autorefractor which has been widely used for research purposes for the past 20 years, but is no longer manufactured. A new autorefractor, the Shin-Nippon SRW-5000, is now available, and if measures using this instrument are shown to be equally accurate and reliable, is likely to replace the R-1. Here we report on the accuracy and reliability (repeatability and reproducibility) of refraction measures in a paediatric population (from 4 to 8 years of age). Subject numbers were 44 for cycloplegic measures and 53 for non-cycloplegic measures. As would be expected, agreement with cycloplegic refraction and reliability were better when SRW-5000 measures were taken using cycloplegia. Repeatability results from the SRW-5000 autorefractor, both with and without cycloplegia were similar to those reported for the Canon R-1.

Continuous recording of accommodation and pupil size using the Shin-Nippon SRW-5000 autorefractor

A newly released commercial autorefractor, the Shin-Nippon SRW-5000 (Japan), has been found to be valid compared to subjective refraction and repeatable over a wide prescription range. Its binocular open field-of-view allows the accommodative state to be monitored while a natural environment is viewed. In conventional static mode, the device can take up to 45 readings in 1 min using digital image analysis of the reflected retinal image of a measurement ring. Continuous on-line analysis of the ring provides high (up to 60 Hz) temporal resolution of the refractive state to an accuracy of < 0.001 D. Pupil size can also be analysed to a resolution of < 0.001 mm. The measurement of accommodation and pupil size was relatively unaffected by eccentricity of viewing up to +/- 10 degrees and instrument focusing inaccuracies of +/- 5 mm. The resolution properties of the analysis are shown to be ideal for measurement of dynamic accommodation and pupil responses.

Clinical evaluation of the Shin-Nippon SRW-5000 autorefractor in adults

A clinical evaluation of the Shin-Nippon SRW-5000 (Japan), a newly released commercial autorefractor, was undertaken to assess its repeatability and validity compared to subjective refraction. Measurements of refractive error were performed on 200 eyes of 100 subjects (aged 24.4 +/- 8.0 years) subjectively (non-cycloplegic) by one optometrist and objectively with the SRW-5000 autorefractor by a second. Repeatability was assessed by examining the differences between the seven autorefractor readings taken from each eye and by re-measuring the objective prescription of 50 eyes at a subsequent session. Although the SRW-5000 read slightly more plus than subjective refraction (mean spherical equivalent +0.16 +/- 0.44 D), it was found to be highly valid (accurate) compared to subjective refraction and repeatable over the prescription range of +6.50 to -15.00 D examined. The Shin-Nippon SRW-5000 autorefractor is therefore a valuable complement to subjective refraction and as it offers the advantage of a binocular open field-of-view, has a great potential benefit for accommodation research studies.

Description of a method for neutralising the Stiles-Crawford effect

The influence of the Stiles-Crawford effect on visual performance can be investigated by filters based on the apodisation model of the Stiles-Crawford effect. We describe the development of practical filters to achieve neutralisation. We present some results of the Stiles-Crawford function showing that the filters work well for expected errors in aligning filters in front of the eye.

[The significance of points alpha and beta on the dark adaptogram of the normal eye]

PURPOSE

To determine the meaning of the points alpha and beta of the curve during dark adaptation.

METHOD

In this paper I studied the curves during dark adaptation of the 48 normal eyes, examined at the Goldmann-Weekers adaptometer, for 30 minutes in standard conditions. The study had two stages: 1. To find out the mathematical low which defined the phenomenon; 2. To give a physiological explanation of the phenomenon.

CONCLUSIONS

1. Distribution in time of point alpha and point beta recognized mathematical low of normal log. 2. The cones adapted to the dark into two phases: from the beginning of the adaptation to the point alpha; after point alpha till before point beta. 3. The rods adapted in three phases: a) before point alpha to the point alpha; b) from point alpha to the point beta; c) after point beta to the terminal threshold.

CONCLUSION

Point beta gained a new meaning: point beta represents the end of the cone's adaptation.