An unusual inguinoscrotal hernia with renal involvement.

We present a case of a 74-year-old man who, while in intensive treatment unit for an upper gastrointestinal bleed, decompensated cardiac failure and concurrent pneumonia, was found to have a large right hydronephrotic pelvic kidney and bladder within the hernia. After discharge, he was medically optimised for 7 months before undergoing an elective open mesh repair of his hernia. During the procedure, drainage of a large hydrocoele was performed to facilitate reduction of the hernia. Postoperatively, he underwent ureteric stenting due to a persistent hydronephrosis with impairment of his renal function. He subsequently made a good recovery and was discharged home with outpatient follow-up planned.

Automated perimetry: using gaze-direction data to improve the estimate of scotoma edges.

PURPOSE: To make an initial assessment of the feasibility of using records of eye movements during perimetry to improve the estimate of scotoma edge location. METHODS: The nasal edge of the blind spot was mapped in seven normal subjects with a 2° grid of test locations, using a custom test station, while gaze direction was monitored with an eye tracker. Records were analyzed to determine whether the combined sensitivity and eye movement data could be used to estimate the nature of the blind spot edge. RESULTS; Analysis was conducted for 15 high-variability test locations. For 11 locations the blind spot edge estimates fit plausibly with the general form of the blind spot (edge orientation within 90° of expected); for four locations the agreement was poor. One consequence of interpreting the test results using the edge estimates was an average reduction of test-retest variability by 58%. CONCLUSIONS: Recordings of eye movements during perimetry can be used to generate an improved estimate of scotoma boundaries. A byproduct of the new estimate is a substantial reduction of test-retest variability.

The human pupil and the use of video-based eyetrackers.

Video-based devices for measuring gaze direction are widespread. However, there is a built-in imprecision in such devices in the event that pupil diameter changes during the experiments. Data are presented to demonstrate this effect. The possibility of correcting eye-position records for the imprecision is discussed and preliminary examples of such correction are presented.

Appearance of the human eye: optical contributions to the "limbal ring".

PURPOSE: Many eyes appear to have a dark ring at the limbus. The present work investigated whether this ring could be partly caused by optical properties of the eye near the limbus. METHODS: The eyes of 10 human subjects were immersed in water, by having subjects wear goggles filled with saline, to assess the changes in the limbal ring when the power of the cornea/air interface was largely eliminated. Eyes were photographed in air and in water, and images were analyzed to determine the prominence of the limbal ring. Corneal shape was determined for the same eyes using a commercial topography system. RESULTS: Immersion in water reduced the prominence of the limbal ring by approximately 55% on average. CONCLUSIONS: The dark limbal ring has a substantial optical component in many eyes, although evidence was found for an anatomical basis in some eyes. Visibility of the ring may depend on extent of non-transparent cornea, which has implications for clinical estimation of angle width.

Rapid pupil-based assessment of glaucomatous damage.

PURPOSE: To investigate the ability of a technique employing pupillometry and functionally-shaped stimuli to assess loss of visual function due to glaucomatous optic neuropathy. METHODS: Pairs of large stimuli, mirror images about the horizontal meridian, were displayed alternately in the upper and lower visual field. Pupil diameter was recorded and analyzed in terms of the "contrast balance" (relative sensitivity to the upper and lower stimuli), and the pupil constriction amplitude to upper and lower stimuli separately. A group of 40 patients with glaucoma was tested twice in a first session, and twice more in a second session, 1 to 3 weeks later. A group of 40 normal subjects was tested with the same protocol. RESULTS: Results for the normal subjects indicated functional symmetry in upper/lower retina, on average. Contrast balance results for the patients with glaucoma differed from normal: half the normal subjects had contrast balance within 0.06 log unit of equality and 80% had contrast balance within 0.1 log unit. Half the patients had contrast balances more than 0.1 log unit from equality. Patient contrast balances were moderately correlated with predictions from perimetric data (r = 0.37, p < 0.00001). Contrast balances correctly classified visual field damage in 28 patients (70%), and response amplitudes correctly classified 24 patients (60%). When contrast balance and response amplitude were combined, receiver operating characteristic area for discriminating glaucoma from normal was 0.83. CONCLUSIONS: Pupillary evaluation of retinal asymmetry provides a rapid method for detecting and classifying visual field defects. In this patient population, classification agreed with perimetry in 70% of eyes.

Variability of visual field measurements is correlated with the gradient of visual sensitivity.

Conventional static automated perimetry provides important clinical information, but its utility is limited by considerable test-retest variability. Fixational eye movements during testing could contribute to variability. To assess this possibility, it is important to know how much sensitivity change would be caused by a given eye movement. To investigate this, we have evaluated the gradient, the rate at which sensitivity changes with location. We tested one eye each, twice within 3 weeks, of 29 patients with glaucoma, 17 young normal subjects and 13 older normal subjects. The 10-2 test pattern with the SITA Standard algorithm was used to assess sensitivity at locations with 2 degrees spacing. Variability and gradient were calculated at individual test locations. Matrix correlations were determined between variability and gradient, and were substantial for the patients with glaucoma. The results were consistent with a substantial contribution to test-retest variability from small fixational eye movements interacting with visual field gradient. Successful characterization of the gradient of sensitivity appears to require sampling at relatively close spacing, as in the 10-2 test pattern.

Pupillary evaluation of retinal asymmetry: development and initial testing of a technique.

Glaucomatous damage to upper and lower retina is often unequal. We have developed a rapid, objective, quantitative measure of asymmetry of retinal sensitivity, using infrared pupillometry and pairs of large stimuli that are symmetric about the horizontal meridian. Results for a group of 11 young subjects free of eye disease indicate that the distribution of asymmetry is close to a normal distribution centered near upper/lower symmetry. Some subjects showed modest amounts of asymmetry, which was relatively uniform within each eye, and between the two eyes, of the subject. This approach to determination of asymmetry within an eye is potentially applicable to testing patients with glaucoma. The narrowness of the distribution should make it possible to detect asymmetries caused by disease.

Effects of changing the direction of gravity on sector pupil dilations.

PURPOSE: To study anterior segment aqueous humor kinetics by using sector pupil dilations with different directions of gravity to change the direction of convectional flow in the anterior chamber. METHODS: Sector pupil dilations were elicited using focal applications of phenylephrine at the limbus. To vary the direction of gravity (and hence the direction of convectional flow) relative to the eye, subjects' heads were tilted left side down or right side down with gaze horizontal. Pupil elongation and pupil center displacement were measured as functions of time. RESULTS: Early stages of pupil dilation were dominated by pupil elongation toward the site of drug application. Amplitude of elongation was about the same for all the application points, but center displacement depended on the application point. Later stages of pupil dilation showed an interaction between the site of drug application and the direction of gravity. CONCLUSIONS: The results are interpreted in terms of anterior chamber convectional flow and its interaction with transpupillary aqueous flow and diffusion. Early distribution in the anterior segment of a substance applied to the limbus appears to be determined primarily by local diffusion, whereas later distribution is affected by movement of the drug in convectional and transpupillary flow.

Modelling transport in the anterior segment of the eye.

PURPOSE: To model the kinetics of substances, particularly applied substances, in the anterior segment. METHODS: A simple computational model was developed to describe portions of the anterior segment. First, a two-dimensional vertical slice through the center of a simplified anterior segment was modeled. This incorporated movement of substances by diffusion and by bulk flow in the anterior segment convectional flow. Second, movement by bulk flow in the secretory inflow and drainage of aqueous humor was included. Lastly, the model was extended to three-dimensional form, enabling it to deal with portions of the anterior segment. RESULTS: The model was applied to a number of situations. First, the anterior chamber was loaded with a substance, and entry of fresh aqueous through the pupil was modeled. To model drug applications, a drug was focally applied to the cornea at the limbus, and the distribution of the drug was followed, including arrival at iris targets. In these situations, model results compared reasonably to published experimental observations and findings. For drug distribution, convectional flow was dominant; however, a good match to experimental findings required that secretory flow and drainage be included. CONCLUSIONS: A simple computational model appears to be able to give a reasonable description of anterior segment kinetics. Although the speed of secretory flow is small compared to the speed of convectional flow, it can exert substantial effects near the surface of the anterior chamber.