Biomedical subjects
L F Jindra
Publications and source records attributed to L F Jindra.
Contrast sensitivity testing: a more complete assessment of vision.
Contrast sensitivity testing is a powerful tool for determining the capability of the visual system to process spatial and temporal information about the everyday objects we see. The current gold standard in the assessment of vision, visual acuity, provides only a limited amount of information, obtained under artificial conditions. Contrast sensitivity testing measures a range of visual performance under real-life conditions. It measures the least amount of contrast needed to detect a visual stimulus and gives us a more complete quantitization of patients' visual capabilities. Many instances in which losses in contrast sensitivity were detected when visual acuity (one point on the contrast sensitivity function) was normal have been reported. These include amblyopia, neuro-ophthalmology, retina, anterior segment disease, and glaucoma. Therefore, contrast sensitivity testing enables the clinician to diagnose selective deficits in visual processing at an earlier stage than is possible with conventional testing methods.
Fourier analysis of the nerve fiber layer by digital imaging techniques.
We introduce a new method to examine the retinal nerve fiber layer (RNFL) that may detect early changes in its structure due to glaucoma. Viewed in the conventional manner, in a plane perpendicular to the retina, we get an estimation of the structural integrity of the RNFL. Viewed from a plane parallel to the retina, the RNFL forms a contour surface of hills and valleys. In our method red free fundus slides are digitally acquired. A waveform, representing a topographic profile cut through the resulting representation of the RNFL contour surface, was analyzed using Fourier's transform. Three cycles/mm in the Fourier power spectrum was used as an arbitrary cutoff to discriminate normal from glaucomatous RNFL. The Fourier power spectrum from normal RNFL was shifted to higher spatial frequencies, while the power spectrum from glaucomatous RNFL was shifted to lower spatial frequencies. Thus, Fourier Analysis can reveal information about such a wave form which is not obvious by visual inspection or by densitometric techniques. This method may allow for an even earlier diagnosis of injury to the optic nerve due to glaucoma.
Calculating mean threshold sensitivity in automated perimetry.
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Blindness following retrobulbar anesthesia for astigmatic keratotomy.
Retrobulbar anesthesia has become the most common form of anesthesia used in ophthalmic surgery. Acute blindness is a rare but known complication of retrobulbar anesthesia given for intraocular surgery. I report a case of acute, permanent blindness caused by direct trauma to the optic nerve when retrobulbar anesthesia was used for an astigmatism correction procedure. Complications, sometimes probably too incidental or insignificant to be noticed, probably occur far more frequently than a review of the literature would indicate. Using dull shorter needles, proper eye positioning, and injection technique will minimize risk of injury to the optic nerve. Another alternative under review is the use of peribulbar anesthesia. Perhaps the best way to prevent a complication from a retrobulbar injection, however, is to carefully and judiciously consider whether any injection at all is needed.