Medical devices; ophthalmic devices; classification of the eyelid thermal pulsation system. Final rule

The Food and Drug Administration (FDA) is classifying the eyelid thermal pulsation system into class II (special controls). The Agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device.

An inexpensive and easy simulation model of ocular ultrasound that mimics normal anatomy as well as abnormal ophthalmologic conditions

We have constructed a simple and inexpensive simulation model for the educational instruction of health care providers to detect normal and abnormal ocular conditions in the bedside emergency setting. Such a training model serves to increase the comfort level in performing ocular ultrasound examinations and can increase the accuracy of examination interpretation. Ophthalmologic examinations can be difficult in the emergency setting, and ultrasound has become a useful tool in the diagnosis of emergent ocular conditions.

A new universal rat restrainer for ophthalmic research

PURPOSE

Immobilization of rats is required in many psychological and physiological experiments. The aim of the current paper was to invent a universal device allowing for adaptation of rats of a wide age range and to maximize convenience for in vivo exposure to optical radiation under not-anaesthetized conditions.

METHODS

Eighty-three 6-week-old and three 18-week-old Sprague-Dawley albino female rats were progressively familiarized daily with the restraining device 5 days prior to exposure to acquire a conditioned response and to reduce stress. After initial habituation, 10 min preceding the ultraviolet radiation (UVR) exposure, the animal was fixed in the rat restrainer. Each unanaesthetized animal was unilaterally exposed to a single dose of 8 kJ/m² UVR-300 nm for 15 min. Three of the 6-week-old and three of the 18-week-old rats were in vivo exposed to UVR once for 10 consecutive days.

RESULTS

All rats acclimatized well to immobilization in the restrainer. Young rats adapted quicker than older rats. The device prevented head movement and body rotation, which allowed for uncomplicated single as well as repeated in vivo exposures to UVR.

CONCLUSIONS

The restrainer effectively immobilizes unanaesthetized rats in the age range 6-18 weeks old, making it useful in future projects involving chronic repeated in vivo exposure of the eye to UVR.

[Interesting life father's of Polish ophthalmology--Wiktor Feliks Szokalski (1811-1891)--in 200 years anniversary of his birth]

Victor Szokalski is considered to be the father of Polish ophthalmology. He was born in Warsaw in 1811, where he also began his medical studies. He fought in the November's Uprising. He was awarded the Military Cross Virtuti. After its fall he went to Germany, where he continued his studies. In 1834 he defended his doctoral thesis. Then he moved to France, where worked at the Eye Clinic of Jules Sichel. He wrote many articles for medical journals and taught students. Already in Paris he acted in a number of social societies, collaborated with Prince Adam Czartoryski, was a friend of Adam Mickiewicz. Fifteen years later he returned to Warsaw, where became a consultant, then the chief at the Ophthalmic Institute. For 33 years he has served as secretary of the Warsaw Medical Society. He wrote the first Polish original textbook of ophthalmology. He died in Warsaw in 1891.

Use of laser speckle flowgraphy in ocular blood flow research

Laser speckle flowgraphy (LSFG) allows for the quantitative estimation of blood flow in the optic nerve head, choroid, retina and iris in vivo. It was developed to facilitate the non-contact analysis of ocular blood flow in living eyes, utilizing the laser speckle phenomenon. The technique uses a fundus camera, a diode laser, an image sensor, an infrared charge-coupled device (CCD) camera and a high-resolution digital CCD camera. Normalized blur (NB), an approximate reciprocal of speckle contrast, represents an index of blood velocity, and shows a good correlation with tissue blood flow rates determined with the microsphere method in the retina, choroid or iris, as well as blood flow rates determined with the hydrogen gas clearance method in the optic nerve head. The square blur ratio (SBR), another index for quantitative estimation of blood velocity, is proportional to the square of the NB. The SBR is theoretically a more exact measurement which is proportional to velocity, whereas the NB is an approximation. Normalized blur was calculated in earlier versions of LSFG because of technical limitations; the SBR is used in current versions of the LSFG instrument. As these values are in arbitrary units, they should not be used to make comparisons between different eyes or different sites in an eye. Clinical protocols, calibration, evaluation procedures and possible limitations of the LSFG technique are described and the results of ocular blood flow studies using LSFG are briefly summarized. The LSFG method is suitable for monitoring the time-course of change in the tissue circulation at the same site in the same eye at various intervals, ranging from seconds to months. Unresolved issues concern the effect of pupil size on measurement results, the effects of various stimulations, and how to measure choroidal and retinal blood flow velocity separately without using the blue-component of argon laser.

Use of laser speckle flowgraphy in ocular blood flow research

Laser speckle flowgraphy (LSFG) allows for the quantitative estimation of blood flow in the optic nerve head, choroid, retina and iris in vivo. It was developed to facilitate the non-contact analysis of ocular blood flow in living eyes, utilizing the laser speckle phenomenon. The technique uses a fundus camera, a diode laser, an image sensor, an infrared charge-coupled device (CCD) camera and a high-resolution digital CCD camera. Normalized blur (NB), an approximate reciprocal of speckle contrast, represents an index of blood velocity, and shows a good correlation with tissue blood flow rates determined with the microsphere method in the retina, choroid or iris, as well as blood flow rates determined with the hydrogen gas clearance method in the optic nerve head. The square blur ratio (SBR), another index for quantitative estimation of blood velocity, is proportional to the square of the NB. The SBR is theoretically a more exact measurement which is proportional to velocity, whereas the NB is an approximation. Normalized blur was calculated in earlier versions of LSFG because of technical limitations; the SBR is used in current versions of the LSFG instrument. As these values are in arbitrary units, they should not be used to make comparisons between different eyes or different sites in an eye. Clinical protocols, calibration, evaluation procedures and possible limitations of the LSFG technique are described and the results of ocular blood flow studies using LSFG are briefly summarized. The LSFG method is suitable for monitoring the time-course of change in the tissue circulation at the same site in the same eye at various intervals, ranging from seconds to months. Unresolved issues concern the effect of pupil size on measurement results, the effects of various stimulations, and how to measure choroidal and retinal blood flow velocity separately without using the blue-component of argon laser.

Retinal imaging with polarization-sensitive optical coherence tomography and adaptive optics

Various layers of the retina are well known to alter the polarization state of light. Such changes in polarization may be a sensitive indicator of tissue structure and function, and as such have gained increased clinical attention. Here we demonstrate a polarization-sensitive optical coherence tomography (PS-OCT) system that incorporates adaptive optics (AO) in the sample arm and a single line scan camera in the detection arm. We quantify the benefit of AO for PS-OCT in terms of signal-to-noise, lateral resolution, and speckle size. Double pass phase retardation per unit depth values ranging from 0.25 degrees/microm to 0.65 degrees/microm were found in the birefringent nerve fiber layer at 6 degrees eccentricity, superior to the fovea, with the highest values being noticeably higher than previously reported with PS-OCT around the optic nerve head. Moreover, fast axis orientation and degree of polarization uniformity measurements made with AO-PS-OCT demonstrate polarization scrambling in the retinal pigment epithelium at the highest resolution reported to date.

Association between corneal hysteresis and central corneal thickness in glaucomatous and non-glaucomatous eyes

PURPOSE

We aimed to determine corneal hysteresis values (CH) using the ocular response analyser (ORA) in non-glaucomatous and glaucomatous eyes and their relationship with central corneal thickness (CCT).

METHODS

Corneal hysteresis, intraocular pressure (IOP) as measured by Goldmann applanation tonometry (GAT) and CCT were prospectively evaluated in 74 non-glaucoma subjects with IOP < 21 mmHg and in 108 patients with treated primary open-angle glaucoma (POAG). One eye in each subject was randomly selected for inclusion in the analysis.

RESULTS

Mean (+/- standard deviation [SD]) age was 59.2 +/- 14.2 years in the non-glaucoma group and 62.4 +/- 9.8 years in the glaucoma group. Mean (+/- SD) GAT IOP was 15.7 +/- 2.65 mmHg and 16.38 +/- 2.73 mmHg in the non-glaucoma and glaucoma groups, respectively. There was no statistically significant difference between the two groups in mean age (p = 0.396) or mean GAT IOP (p = 0.098). Mean (+/- SD) CH was 10.97 +/- 1.59 mmHg in the non-glaucoma and 8.95 +/- 1.27 mmHg in the glaucoma groups, respectively. The difference in mean CH between the two groups was statistically significant (p < 0.0001). There was a strong positive correlation between CH and CCT in the non-glaucoma group (r = 0.743) and a significantly (p = 0.001) weaker correlation (r = 0.426) in the glaucoma group.

CONCLUSIONS

Corneal hysteresis was significantly lower in eyes with treated POAG than in non-glaucomatous eyes. The corneal biomechanical response was strongly associated with CCT in non-glaucoma subjects, but only moderately so in glaucoma patients. It can be assumed that diverse structural factors, in addition to thickness, determine the differences in the corneal biomechanical profile between non-glaucomatous and glaucomatous eyes. Corneal hysteresis could be a useful tool in the diagnosis of glaucoma.

Sophisticated instrumentation and ophthalmic ultrasonography

Formerly, ophthalmic ultrasonography was leading in view of high-performance apparatuses and transducer probes: e.g., the first array-scanner in the world was built for ophthalmic use. Within the past 2 decades, however, high-tech innovations were merely developed for other medical specialties. These were studied in view of their use for ultrasonography of eye and orbit. The combination of B-scan and Doppler techniques facilitates detection of orbital vessels. The resolution of ophthalmic digital B-scan video images proved poorer than crt-B-scans. A digital memory, however, is advantageous. But one high-resolution crt-type B-scan needs more than one disc storage capacity. "Frontline digitalization" could help to reduce the amount of data. Array transducers are now available in small sizes and could better show structure movements, but they were not yet adapted to ophthalmic use. This applies as well to annular arrays and dynamic focusing. Different methods of 3-dimensional scanning and (Pseudo-) 3-dimensional imaging might renew Baum's and Coleman's early work.

Dual-conjugate adaptive optics for wide-field high-resolution retinal imaging

We present analysis and preliminary laboratory testing of a real-time dual-conjugate adaptive optics (DCAO) instrument for ophthalmology that will enable wide-field high resolution imaging of the retina in vivo. The setup comprises five retinal guide stars (GS) and two deformable mirrors (DM), one conjugate to the pupil and one conjugate to a plane close to the retina. The DCAO instrument has a closed-loop wavefront sensing wavelength of 834 nm and an imaging wavelength of 575 nm. It incorporates an array of collimator lenses to spatially filter the light from all guide stars using one adjustable iris, and images the Hartmann patterns of multiple reference sources on a single detector. Zemax simulations were performed at 834 nm and 575 nm with the Navarro 99 and the Liou- Brennan eye models. Two correction alternatives were evaluated; conventional single conjugate AO (SCAO, using one GS and a pupil DM) and DCAO (using multiple GS and two DM). Zemax simulations at 575 nm based on the Navarro 99 eye model show that the diameter of the corrected field of view for diffraction-limited imaging (Strehl >or= 0.8) increases from 1.5 deg with SCAO to 6.5 deg using DCAO. The increase for the less stringent condition of a wavefront error of 1 rad or less (Strehl >or= 0.37) is from 3 deg with SCAO to approximately 7.4 deg using DCAO. Corresponding results for the Liou-Brennan eye model are 3.1 deg (SCAO) and 8.2 deg (DCAO) for Strehl >or= 0.8, and 4.8 deg (SCAO) and 9.6 deg (DCAO) for Strehl >or= 0.37. Potential gain in corrected field of view with DCAO is confirmed both by laboratory experiments on a model eye and by preliminary in vivo imaging of a human eye.

Adjustable fluidic lenses for ophthalmic corrections

We report on two fluidic lenses that have been developed for ophthalmic applications. The lenses use a circular aperture to demonstrate optical powers between -20 and +20 D and a rectangular aperture to demonstrate astigmatism with values ranging from 0 to 8 D. Measurements of image quality were made with the fluidic lens using a model eye. Both lenses were variable and controllable by adjusting the fluid volume of the lens. To the best of our knowledge this is the first demonstration of a continuously variable lens for control of astigmatism.

Dr Adam Zamenhof (1888-1940) and his insight into ophthalmology

Adam Zamenhof was greatly influenced by his father, Ludwik Zamenhof, who designed the international language Esperanto. Like his father, he became an ophthalmologist and joined the Esperanto movement. He published in the field of ophthalmology and was soon chosen as head of an ophthalmology department. He subsequently became Chief of the Orthodox Jewish Hospital at Czystem in Warsaw. He was active in the leadership of the Bialystok-Warsaw Chamber of Medical Doctors. He perished in the Nazi Holocaust (Shoah) but all Zamenhof's ideals that Adam served as a doctor and social activist remain still alive.

Busin Guide vs Forceps for the Insertion of the Donor Lenticule in Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

To compare two insertion methods in Descemet stripping automated endothelial keratoplasty (DSAEK): Busin guide-assisted vs Forceps-assisted insertion of the corneal lenticule graft.

DESIGN

Prospective, consecutive, comparative, nonrandomized study.

METHODS

setting: Cornea clinic at the Toronto Western Hospital. study population: Sixty-three eyes of 63 consecutive patients were included. All patients underwent DSAEK for Fuchs endothelial dystrophy, pseudophakic bullous keratopathy, aphakic bullous keratopathy, failed graft, or iridocorneo endothelial syndrome. Twenty-six consecutive donor discs were inserted with the Busin guide and 37 consecutive eyes underwent forceps assisted insertion of the donor. main outcome measures: Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, corneal endothelial cell loss, and postoperative complications.

RESULTS

Busin guide-assisted DSAEK group had significantly worse UCVA and lower donor endothelial cell counts preoperatively. No significant differences were noted in the intraoperative or postoperative complications. Six months following surgery, BCVA was not significantly different between groups: 20/37 in the Busin guide-assisted DASEK group vs 20/42 in the Forceps-assisted group (P = .39). Mean spherical equivalent was -0.02 diopters (D) and 0.82 D (P = .06), and mean refractive cylinder was 2.2 D and 1.31 D (P = .0006), respectively. Endothelial cell loss was significantly lower in the Busin guide-assisted DASEK group: 25% loss vs 34.3% loss in the Forceps-assisted DSAEK group. (P = .04).

CONCLUSIONS

Although visual outcomes were not different between the groups studied, Busin guide-assisted DSAEK resulted in lower percentage of endothelial cell loss compared with forceps insertion, six months following surgery.

The effects of CAM vision stimulator for bilateral amblyopia of different etiologies

BACKGROUND

To evaluate the association between bilateral amblyopia and the effects of CAM vision stimulator.

METHODS

This retrospective study was carried out between January 1994 and July 2004. The 105 children enrolled were all younger than 7 years old and had bilateral amblyopia. All children wearing full-correction glasses regularly received CAM vision stimulation once per week. The patients' age, initial best corrected visual acuity (BCVA), final BCVA, and the number of CAM sessions needed to achieve a visual acuity (VA) > or = 0.8 were recorded.

RESULTS

The major cause of bilateral amblyopia was refractive error. In this study, the types of refractive error were classified as astigmatism (> 2.0D, 61 cases), hyperopia (> 3.0D, 17 cases), and myopia (> 4.0D, 12 cases). The myopic group showed significantly poorer visual outcomes than the other children after CAM treatment (p < 0.05). However, older children patients had better initial BCVA, and the hyperopic patients had the better outcomes in this study.

CONCLUSIONS

CAM treatment for bilateral amblyopia can achieve satisfactory improvement in 3 months in most instances. The myopic group and children younger than 4 years old had worse visual outcomes after CAM treatment.

Depth of focus in pseudophakic eyes

PURPOSE

To assess depth of field/depth of focus in pseudophakic eyes as function of visual acuity.

SETTING

Department of ophthalmology of National Medical Academy of Postgraduate Education.

METHODS

Forty-three pseudophakic eyes of 43 patients after implantation in the capsular bag of monofocal posterior chamber IOLs were examined. All patients had visual acuities at least 20/20 for distance. Visual acuity was examined by charts consisting the Landolt's rings under defined constant illumination within distance from 3 m to 20 cm from patients' eyes at various distances with difference of 10 cm (29 measurements). Depth of field was calculated in diopters.

RESULTS

The mean value of the depth of field in pseudophakic eyes with pupil diameter of 3 +/- 0.3 mm was as follows: 1.12 D for visual acuity 20/20, 0.62 D for visual acuity 20/13, and 0.47 D for visual acuity 20/10.

CONCLUSIONS

Depth of focus correlates to normal levels of visual acuity. The higher the visual acuity, the lower the depth of focus. The ability of clear vision due to depth of focus-pseudoaccommodation is passive function. Separating the pseudoaccommodation from artificial accommodation in eyes with accommodative IOLs requires strict standardization of methodology especially regarding diameter of pupil, size of test objects, and level of illumination.

Bacterial flora on slit lamps

The slit lamp can be a source of cross infection in the clinic setting. We identified the bacteria flora on slit lamps and determined the risk of transmission to patients. Frequent cleaning of the slit lamp especially after treating infected cases can decrease the transmission of organisms.

[Development of the technology of the substance of davikol and standardization]

Among wide assortment of pharmaceutical remedies, that use modern medicine as a weapon against different diseases, special place belongs to the ophthalmic pharmaceutical forms, and their development presents independent branch of pharmaceutical technology. Recently, as a reason of various diseases and among them ophthalmic problems, is considered free radicals and reactions with their participation. Protection of the organism from such diseases presents a main goal of antioxidant system. Nowadays, special attention is paid to the natural antioxidants. On the basis of the natural honey technology of eye drops davikol with antioxidant activity have been developed. The objective of our study has been the development of the substance of prolonged pharmaceutical dosage form davikol - eye ophthalmic drops and its standardization. The qualitative and quantitative methods were developed. It is concluded that the optimal method of drying of davikol is sublimation. Dry powder (active substance) davikol was obtained; quality characteristics were identified.

Optical projection mires for measurements of the radii of curvature of the cornea in biomicroscopes

Keratometry is currently achieved by projecting a circular mire onto the patient's cornea and analyzing the size and shape of its reflected image. The projection mires are decisive for the precision of the measurement. We have previously developed a keratometric module for slit lamps, and the development of four projection mires are presented. Mire 1 is composed of optical fibers and electrical cables; Mire 2, 48 LEDs; Mire 3, optical fibers and no electrical cables; and Mire 4, mechanical parts--cable free. Mires 2-4 provide accurate keratometry measurements at slit lamps. Mire 4 is the most adequate for the clinical environment.

How to measure slab-off and reverse slab prism in spectacle lenses

It is well known that new spectacle lenses for the correction of anisometropia can induce diplopia with reading. The difference in the powers of the lenses induces a net prismatic effect that can cause double vision through off-center areas of the lenses. This is particularly bothersome when patients try to read, often noting vertical double vision in attempted downgaze, especially through multifocal add segments. This induced prismatic effect can be compensated at one level of downgaze by the use of slab-off or reverse slab prism. Typically the slab-off correction is ground into the stronger minus, or weaker plus lens. Reverse slab is ground into the weaker minus, or stronger plus, lens. Unfortunately, determining the amount of slab-off prism already incorporated into spectacle lenses is nonintuitive and inconvenient. This usually requires the use of a lens clock, which is not widely accessible to many ophthalmology practices. A simple technique, described in the past but poorly known, is illustrated here for quickly measuring slab-off and reverse slab prism prescription lenses in the clinic with a common manual lens meter.

Efficacy of a new warm moist air device on tear functions of patients with simple meibomian gland dysfunction

PURPOSE

To evaluate the safety and efficacy of an original warm moist air device on tear functions and ocular surface of patients with simple meibomian gland dysfunction (MGD).

METHODS

Fifteen patients with simple MGD and 20 healthy volunteers were recruited in an initial prospective interventional clinical trial to evaluate the safety and short-term effects of the warm moist air device. The device was applied to the eyes of the subjects for 10 minutes. Temperatures of the eye lids and corneas were measured with an infrared thermometer. Symptoms of ocular fatigue were scored using visual analog scales (VASs). Schirmer test, tear film break-up time (BUT), DR-1 tear film lipid layer interferometry, fluorescein staining, and rose bengal staining were also performed before and after the application of the eye steamer. After the initial study, another 2-week prospective clinical trial was carried out in 10 patients with MGD who received the warm moist air treatment. Ten other patients were also recruited and received warm compress treatment with hot towels for 2 weeks to evaluate the long-term effects of the warm moist air device and the warm compresses on tear film lipid layer thickness and ocular surface health. The warm moist air device and the warm compresses were applied for 10 minutes twice a day. The changes in VAS scores for symptoms, BUT values, fluorescein, and rose bengal staining scores were examined before and after each treatment during the second trial.

RESULTS

VAS scores of ocular fatigue improved significantly with short- and long-term applications of the warm moist air device in both studies. The mean corneal surface and eye lid temperatures showed significant elevation within safe limits 10 minutes after the moist air application. The mean BUT prolonged significantly in the patients receiving warm moist air applications but did not change significantly in those treated with warm compresses. DR-1 tear film lipid layer interference showed evidence of lipid expression in the patients and controls, with thickening of the tear film lipid layer after 10 minutes of warm moist air device use. In the 2-week trial, tear film lipid layer thickness increased in both warm moist air device and warm compress groups, with a greater extent of increase in the warm moist air device group.

CONCLUSION

Warm moist air device use provided symptomatic relief of ocular fatigue and improvement of tear stability in patients with MGD. The new warm moist air device seems to be a safe and promising alternative in the treatment of MGD.

Maximum permissible exposures for ocular safety (ANSI 2000), with emphasis on ophthalmic devices

After discussing the rationale and assumptions of the ANSI Z136.1-2000 Standard for protection of the human eye from laser exposure, we present the concise formulation of the exposure limits expressed as maximum permissible radiant exposure (in J/cm(2)) for light overfilling the pupil. We then translate the Standard to a form that is more practical for typical ophthalmic devices or in vision research situations, implementing the special qualifications of the Standard. The safety limits are then expressed as radiant power (watts) entering the pupil of the eye. Exposure by repetitive pulses is also addressed, as this is frequently employed in ophthalmic applications. Examples are given that will familiarize potential users with this format.

A novel approach to lacrimal sac dissection in dacryocystorhinostomy

The use of membrane-peeling vitreoretinal forceps to facilitate lacrimal sac dissection in external dacryocystorhinostomy is demonstrated. The closed vitreoretinal forceps are advanced via the upper punctum and canaliculus, through to the lacrimal sac. They are then opened maximally providing two points of elevation. This maneuver allows for easier identification of the plane of dissection during lacrimal flap creation. It is especially useful with complex anatomy and for junior trainees in helping to orient the dissection. No tissue or instrument damage has been noted, and because many ophthalmic units have a vitreoretinal service, the forceps may be readily available at no extra cost.

Insertion of a Bandage Contact Lens With Minims

PURPOSE

To describe a new technique for the insertion of a bandage contact lens with the help of sterile Minims.

METHODS

The bandage contact lens is picked up with the nozzle of the Minims by suction. The lens is then taken to the patient, placed on the cornea, and released by breaking the vacuum.

RESULTS

Examination of the contact lens under the microscope after insertion showed no damage.

CONCLUSIONS

Insertion of a bandage contact lens with Minims is a nontouch, inexpensive, easy, and patient-friendly method. It can reduce the risk of infection in already compromised eyes.

Personal identification based on prescription eyewear

This study presents a web-based tool that can be used to assist in identification of unknown individuals using spectacle prescriptions. Currently, when lens prescriptions are used in forensic identifications, investigators are constrained to a simple "match" or "no-match" judgment with an antemortem prescription. It is not possible to evaluate the strength of the conclusion, or rather, the potential or real error rates associated with the conclusion. Three databases totaling over 385,000 individual prescriptions are utilized in this study to allow forensic analysts to easily determine the strength of individuation of a spectacle match to antemortem records by calculating the frequency at which the observed prescription occurs in various U.S. populations. Optical refractive errors are explained, potential states and combinations of refractive errors are described, measuring lens corrections is discussed, and a detailed description of the databases is presented. The practical application of this system is demonstrated using two recent forensic identifications. This research provides a valuable personal identification tool that can be used in cases where eyeglass portions are recovered in forensic contexts.

Recovery from macular phototoxicity after corneal triple procedure

PURPOSE

Visual recovery from macular phototoxicity in 2 cases after prolonged exposure to operating microscope light from uncomplicated corneal triple-procedure surgery. Recovery is discussed in the context of repair and regeneration.

METHODS

Retrospective case reports.

RESULTS

Immediately postoperatively, both patients reported positive scotomata and were found to have macular retinal pigment epithelial depigmentation. In 1 case, the fovea was involved. By 6 to 12 months, the scotomata had disappeared despite large areas of retinal pigment epithelial hyperpigmentation remaining.

CONCLUSION

Recovery from macular phototoxicity occurs, although the mechanism remains unclear. Positive scotomata in these cases resolved over several months. The time scale of recovery was consistent with the time required for cellular replacement and possible differentiation from neural progenitor cells.

Postoperative follow up by dynamic light scattering: detection of inflammatory molecular changes in the cornea, the vitreous and the lens

OBJECTIVE

To detect post-op molecular changes and inflammatory processes by dynamic light scattering (DLS) in eye segments. To develop DLS parameters which are appropriate for the control of post-op course after ophthalmologic surgery. METHODS, DESIGN: Three new DLS devices were tested in different post-op clinical settings such as pseudoexfoliation syndrome (PEX), cataract surgery and retinal surgery. In a second step DLS was used to detect molecular changes in the cornea of 6 patients after photo refractive keratectomy (PRK) and 16 patients after photo astigmatic refractive keratectomy (PARK).

RESULTS

In PEX-patients cataract surgery changed the DLS signals of the anterior chamber and the lens in a specific way compared to the pre-op situation. Cataract patients without PEX had more scattering particles post-op and retinal surgery modified the DLS signal of the vitreous. Furthermore it was shown that the length of the corneal scattering vector l correlated with the process of the corneal wound healing after PARK. One and three months after surgery the lengths of the scattering vectors had increased significantly but returned to pre-op values twelve months post-op.

DISCUSSION

The post-op transparency of eye segments such as the cornea, the vitreous and the anterior chamber depends primarily on the wound healing mechanisms. DLS seems to be a suitable method to control the corneal recovery after refractive surgery.

CONCLUSIONS

The length of the scattering vector l correlates well with the wound healing after refractive surgery. However DLS-signals seem to contain information about the molecular composition of tissue too. Therefore further research is needed to refine the interpretation of the DLS signals.

Comparative study of the polaroid and digital non-mydriatic cameras in the detection of referrable diabetic retinopathy in Australia

AIM

To show that the non-mydriatic retinal camera (NMRC) using polaroid film is as effective as the NMRC using digital imaging in detecting referrable retinopathy.

METHODS

A series of patients with diabetes attending the eye out-patients department at the Royal Victorian Eye and Ear Hospital had single-field non-mydriatic fundus photographs taken using first a digital and then a polaroid camera. Dilated 30 degrees seven-field stereo fundus photographs were then taken of each eye as the gold standard. The photographs were graded in a masked fashion. Retinopathy levels were defined using the simplified Wisconsin Grading system. We used the kappa statistics for inter-reader and intrareader agreement and the generalized linear model to derive the odds ratio.

RESULTS

There were 196 participants giving 325 undilated retinal photographs. Of these participants 111 (57%) were males. The mean age of the patients was 68.8 years. There were 298 eyes with all three sets of photographs from 154 patients. The digital NMRC had a sensitivity of 86.2%[95% confidence interval (CI) 65.8, 95.3], whilst the polaroid NMRC had a sensitivity of 84.1% (95% CI 65.5, 93.7). The specificities of the two cameras were identical at 71.2% (95% CI 58.8, 81.1). There was no difference in the ability of the polaroid and digital camera to detect referrable retinopathy (odds ratio 1.06, 95% CI 0.80, 1.40, P = 0.68).

CONCLUSION

This study suggests that non-mydriatic retinal photography using polaroid film is as effective as digital imaging in the detection of referrable retinopathy in countries such as the USA and Australia or others that use the same criterion for referral.

A clinical test of otolith function: static ocular counterroll with passive head tilt

When roll-tilted around the naso-occipital axis, humans exhibit compensatory torsional rotation of the eyes in the opposite direction owing to the torsional vestibulo-ocular reflex. In the static condition (sustained head roll), the utricles act as responsible sensors for 'static ocular counterroll'. Contributions of cervico-ocular reflexes remain unknown. To find an easy, clinically useful test of utricular function, we induced ocular counterroll in 10 healthy study participants (two men, mean age 27+/-2 years) under three stimulation conditions (active/passive head tilt and passive whole body tilt in roll plane), used three-dimensional video-oculography to measure it, and compared values. Active head-tilt-induced ocular counterroll varied most and was thus less reliable than passive head and body tilt-induced ocular counterroll. Utricular function can thus be tested simply by measuring passive head tilt with video-oculography.

[Design of a quantitative keratoscope used for ocular microsurgery]

A new quantitative keratoscope used specially for ocular microsurgery to measure corneal astigmatism is reported. A combined cylinder-lens, which power can be changed by rotating lens in anti-direction equally, was designed according to the principal of the crossing cylinder lens. The axis direction is fixed when the lens is rotated. The corneal astigmatism can be measured by changing the power of the combined lens to adjust the corneal ring images. The keratoscope could be used to measure the corneal astigmatism quantitatively specially for ocular microsurgery. At the work-distance of 0.025 m, the maximum power of measured astigmatism was up to 8.50 D. The error of the measurement was less than 0.20 D. The keratoscope is a portable lens to be used easily during the ocular microsurgery. The reporting keratoscope is a simple combined cylinder-lens that can be used to measure corneal astigmatism, including the power and the axis of astigmatism, easily during ocular microsurgery.

High-resolution, in vivo retinal imaging using adaptive optics and its future role in ophthalmology

Until recently it was impossible to fully realize the optical resolution afforded by the human eye due to the inherent optical aberrations. These aberrations limit the ability to see fine structure in the retinal layers and visual perception of the outside world. A conventional spectacle or contact lens refraction only provides a static amelioration of the lowest order aberrations, namely defocus and astigmatism. In addition, all of these distortions are constantly evolving due to changes in accommodation and head/eye movements. The technique of adaptive optics not only corrects all of the static spatial modes but also measures and corrects any dynamic changes. Such systems have allowed for routine in vivo cellular imaging, the classification of individual photoreceptor cells and have enabled psychophysical testing of human visual function at the neural level. This review introduces the principle of adaptive optics and the key hardware required to implement such a scheme. The integration of adaptive optics into different imaging modalities is presented along with descriptions of current systems in use today and the experimental results obtained to date. Finally, the review concludes by discussing future technology and gives the author's prediction of how the field will evolve over the coming years.