Pairs Of Eyes Research Articles

Unilateral or asymmetric pseudoexfoliation syndrome? An ultrastructural study.

Clinically, most patients with pseudoexfoliation (PEX) syndrome reveal only unilateral ocular involvement. However, the generalized nature of the disorder suggests that PEX syndrome is clinically asymmetric rather than strictly unilateral. To perform an ultrastructural study of the contralateral eyes in patients with unilateral PEX syndrome. Five pairs of donor eyes with slitlamp microscopic, macroscopic, and light microscopic evidence of unilateral PEX syndrome and 6 normal control eyes were investigated by transmission electron microscopy and light and electron microscopic immunohistochemistry using antibodies against the human natural killer (HNK-1) epitope and against latent transforming growth factor beta1-binding protein, both markers for the identification of PEX deposits. Ultrastructural alterations were observed in anterior segment tissues of all apparently not involved fellow eyes. These included (1) deposits of typical PEX fibrils on the iris and ciliary epithelia and in the dilator muscle of the iris; (2) increased accumulation of extracellular matrix, including microfibrils and reduplicated basement membrane material in the periphery of iris vessels, in the dilator muscle and in the juxtacanalicular tissue of the trabecular meshwork; and (3) degenerative changes of the iris pigment epithelium and dilator muscle cells. Latent transforming growth factor beta1-binding protein- and HNK-1-positive deposits indicating PEX material accumulations were detected in the periphery of iris vessels and in the dilator muscle in all affected and contralateral eyes, but not in the control eyes. These subclinical alterations of contralateral eyes in clinically so-called unilateral PEX syndrome support the concept that PEX syndrome is a generalized basically bilateral disorder with a clinically marked asymmetric manifestation. The iris changes may account for the clinical signs characteristic of early stages, such as melanin dispersion, peripupillary atrophy, trabecular meshwork pigmentation, and insufficient asymmetric mydriasis. The findings should be considered in the clinical management of the patients. In view of the fact that PEX syndrome is the most common identifiable cause of open-angle glaucoma worldwide and as it is an important risk factor for a wide spectrum of ocular complications, particularly during cataract surgery, the potential involvement of both eyes in the PEX process is of clinical significance.

Randomized comparison of diode laser photocoagulation versus cryotherapy for threshold retinopathy of prematurity: seven-year outcome

PURPOSE: To report the structural and functional outcomes at a minimum of 7 years postmenstrual age after randomized treatment of threshold retinopathy of prematurity with laser ablation or cryotherapy. METHODS: Nineteen patients were entered into a prospective, randomized protocol, in which one eye received cryotherapy, while the other eye received diode laser photocoagulation. Asymmetric eyes were randomly assigned. Two patients have died, and seven were no longer available for 7-year outcome examinations, leaving 10 children for analysis. RESULTS: Six males and four females with a mean birthweight of 631 g and a mean gestational age of 24.8 weeks were examined. Eight were symmetrical cases and treated in both eyes. Of these, there were six concordant and two discordant structural outcomes. The laser-treated eyes had the favorable outcome in each instance. The geometric mean visual acuity of the paired eyes after laser photocoagulation was 20/33, and after cryotherapy it was 20/133 ( P = .03). The mean refractive error was −6.50 diopters after laser photocoagulation and −8.25 diopters after cryotherapy ( P = .27), although one of the cryotherapy eyes could not be refracted because of phthisis. CONCLUSIONS: Laser photocoagulation appears to be associated with a structural and functional outcome at least as good as cryotherapy 7 years after therapy. Visual acuity and refractive error data suggest that laser photocoagulation may have an advantage over cryotherapy.

Induction of Tyrosinase Gene Transcription in Human Iris Organ Cultures Exposed to Latanoprost

Topical administration of latanoprost sometimes induces gradual iris darkening. The present study was undertaken to determine if latanoprost can increase transcription of the gene for tyrosinase, an important enzyme in the biosynthesis of melanin. Results from brown, hazel, and blue irides were compared. Iris tissue was isolated from 30 pairs of postmortem human donor eyes, and 2 iris segments from each eye were incubated in tissue culture medium supplemented with 200nM latanoprost acid or vehicle for 7 days. Tyrosinase messenger RNA (mRNA) was determined using real-time polymerase chain reaction analysis (TaqMan quantitative polymerase chain reaction). Results for tyrosinase mRNA were normalized according to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA in each sample. Tyrosinase mRNA expression was similar in blue and hazel irides, and ranged from 0.7-fold to 12.6-fold greater than GAPDH expression. In contrast, control brown iris culture tyrosinase expression ranged from 6.4-fold to 265-fold greater than GAPDH expression. Induction of tyrosinase mRNA by latanoprost was below threshold in all the blue iris cultures (n = 8 pairs), present in 1 of 9 hazel iris cultures, and present in 5 of 13 brown iris cultures. Mean induction in the responding hazel iris cultures was 1.40-fold. Mean induction among the responding brown iris cultures was 2.97-fold. These observations support the view that iris darkening associated with latanoprost treatment reflects induction of tyrosinase expression. Moreover, they suggest that the probability that latanoprost will increase tyrosinase expression is directly related to the magnitude of tyrosinase expression before treatments are initiated. The variability of iris darkening with latanoprost may reflect natural variation in the basal transcription of tyrosinase.

Hydraulic conductivity of fixed retinal tissue after sequential excimer laser ablation: barriers limiting fluid distribution and implications for cystoid macular edema.

To measure the hydraulic conductivity (HC) of human retina and to determine the presence and location of high-resistance barriers to fluid movement through the retina. Forty-one pairs of human eyes were investigated using an HC chamber. Once baseline HC had been determined, the effect of ablating through varying thickness of retina from the vitreous or photoreceptor surface using an excimer laser (193 nm) was investigated. Tissue samples were then processed for histological investigation. The HC of fixed intact human retina was 2.54 x 10(-10) m/s per pascal at 539 Pa (range, 0.6 x 10(-10) to 3.3 x 10(-10) m/s per pascal; SD, 0.6 x 10(-10) m/s per pascal [1 mm Hg equals 133 Pa]). Ablation from either surface resulted in little change in HC until a critical depth was reached, at which point there was an order of magnitude increase. The critical depth was approximately 170 microm from the inner limiting membrane when ablating from the vitreous surface and 70 microm from the inner limiting membrane when ablating from the photoreceptor surface. Histological specimens showed that these barriers were the synaptic portion of the outer plexiform layer, and the inner plexiform layer, respectively. The 2 high-resistance barriers to fluid flow through the retina are the synaptic portion of the outer plexiform layer, and the inner plexiform layer. These observations help to explain the distribution of cystoid macular edema seen in histological studies and with optical coherence tomography.

Innovations in Large Classes in Pakistan

* The globalization of English has made classes of more than 100 students a challenging reality for many teachers of English-especially in developing countries. These teachers are also required to cope with obsolete syllabi and, as a result of time constraints, have very little freedom to innovate. In the late 1980s, the research reports of the Lancaster-Leeds Language Learning in Large Classes Research Project (Coleman, 1989) looked at the problems of large classes, based on responses from nonnative teachers of English from Indonesia, Japan, Nigeria, Senegal, and South Africa. Such responses can be considered fairly representative of countries with similar conditions. Coleman lists four problems identified by teachers around the world (pp. 2-10). First, teachers feel self-conscious, nervous, and uncomfortable under the constant focus of more than 100 pairs of eyes. Second, discipline and classroom management are problems, especially if the teacher uses communicative methodology. Third, evaluating or reviewing students' oral and written work is difficult. Last, teachers feel that because they cannot give individual attention in large classes, very little learning takes place. Taking up this final issue, four colleagues and I piloted and then ran a project to investigate innovative ways of bringing about effective learning in large classes (Sarwar, 2000, 2001). The program was introduced both at the tertiary and undergraduate level in a women's college in Pakistan in classes of over 150 adult students of mixed ability between the ages of 16 and 21. Both the teachers and learners were nonnative speakers of English. At the initial stages, we asked ourselves the following questions:

Description of a new species of Armandia (Polychaeta: Opheliidae) from western Kyushu, Japan, with character variations

Armandia amakusaensis sp. nov. (Polychaeta: Opheliidae) is described from an intertidal sandflat in western Kyushu, Japan. The holotype measures 13.14 mm in total body length, and has 32 setigers, with branchiae on setigers 2–31. Eleven pairs of lateral eyes are present on setigers 7–17. The anal funnel opens dorsally, fringed with 11 papillae, its length being slightly shorter than the length of the last three setigers. A long unpaired cirrus originates mid-ventrally from the inside of the anal funnel. Variation in these diagnostic characters is described. The new species is most similar to A. leptocirris (Grube, 1878) and A. intermedia Fauvel, 1902. However, it is distinguished from A. leptocirris in the distribution patterns of the branchiae and the lateral eyes, and from A. intermedia in the distribution pattern of the lateral eyes, the ratio of anal funnel length to total body length, and the number of anal-funnel papillae.

Sensory system evolution at the origin of craniates

The multiple events at the transition from non-craniate invertebrate ancestors to craniates included the gain and/or elaboration of migratory neural crest and neurogenic placodes. These tissues give rise to the peripherally located, bipolar neurons of all non-visual sensory systems. The brain was also elaborated at or about this same time. Were the peripheral and central events simultaneous or sequential? A serial transformation hypothesis postulates that paired eyes and an enlarged brain evolved before the elaboration of migratory neural crest placodal sensory systems. Circumstantial evidence for this scenario is derived from the independent occurrence of the combination of large, paired eyes plus a large, elaborated brain in at least three taxa (cephalochordates, arthropods and craniates) and partly from the exclusivity of the diencephalon for visual system-related distal sensory components versus the restricted distribution of migratory neural crest-placodal sensory systems to the remaining parts of the neuraxis. This scenario accounts for the similarity of all central sensory system pathways due to the primary establishment of descending visual pathways via the diencephalon and midbrain tectum to brainstem motor regions and the subsequent exploitation of the same central beachhead by the migratory neural crest-placodal systems as a template for their organization.

Stimulus deprivation myopia in human congenital ptosis: a preliminary report of 50 unilateral cases

To investigate the frequency of hyperopia and suspected stimulus deprivation myopia in human congenital ptosis. Ametropia was evaluated in both eyes of 50 patients with congenital ptosis. The age at investigation was one year and older, average 6 years and 10 months. The amount of refraction was documented as the spherical equivalent (100% cycloplegia). Differences between the paired eyes of 1.0 dpt or more were defined as anisometropia. Statistical analysis was performed using the chi-square and sign tests. The frequency of myopia was lower (7/50: 14%) than that of hyperopia (43/50: 86%) in the ptotic eye (p<0.001). However, myopia occurred more often in the ptotic eye (7/50: 14%) than in the fellow eye (3/50: 6%, p>0.3). Myopic anisometropia was found only in the ptotic eye (5/50 vs. 0/50, p = 0.06), but was not more frequent than hyperopic anisometropia: (5/50 vs. 9/50, p>0.4). A covered center of the pupil in 27 out of 50 eyes was not associated significantly with myopia (2 of 27 versus 5 of 23, p>0.2). Altogether, we found a significantly higher rate of myopia <-1 dpt and hyperopia > 2 dpt: 10% vs. 1.4% and 40% vs. 10.2% (p<0.001) in comparison with normal school children. In summary, the following three findings were noted, of which the first two were expected and the third was not. 1. Compared with the normal population, there was an overall higher frequency of myopia in unilateral congenital ptosis. 2. There was a higher frequency of myopia in the ptotic than in the fellow eye. 3. Compared with the normal population, there was also a higher frequency of hyperopia. The clinical presentation of human congenital ptosis may be influenced by compensating head posture, strabismus, accommodation and biochemical effects, and the condition may therefore differ from the classical well-defined animal model of stimulus deprivation myopia.

Unilateral or asymmetric PEX syndrome? An electron microscopy study

The pseudoexfoliation (PEX) syndrome which is characterized by the accumulation of an abnormal extracellular material in intra- and extraocular tissues, clinically strictly manifests both unilateral and bilateral. However, the generalized nature of this matrix process does not support unilateral ocular manifestation. The aim of this study, therefore, was a detailed histopathological analysis of the apparently not involved fellow eyes in so-called "unilateral" PEX syndrome. For transmission electron microscopy, 5 pairs of donor eyes with slitlamp-microscopic, macroscopic and light microscopic evidence of unilateral PEX syndrome and 6 normal control eyes were studied. For immunohistochemistry, light and electron microscopic antibodies against LTBP-1 and HNK-1, two well-known markers for PEX deposits, were used. All apparently not involved contralateral eyes showed ultrastructural changes in the iris, in the ciliary body and in the trabecular meshwork. These changes include deposits of typical PEX fibrils on iris and ciliary epithelia as well as in the iris dilator muscle, microfibrillar precursors in the periphery of iris vessels, degenerative changes of the iris pigment epithelium and of the dilator muscle and an increased accumulation of extracellular matrix components around iris vessels, in the dilator muscle and in the juxta-canalicular connective tissue of the trabecular meshwork. In all contralateral and PEX eyes, but not in the control eyes, LTBP-1 and HNK-1 positive deposits could be identified in the periphery of iris vessels and in the dilator by light- and electron microscopic immunolabeling. The observed alterations in contralateral eyes in so-called "unilateral" PEX syndrome support the concept that the PEX syndrome is a generalized, basically bilateral disease which may present in a clinically asymmetric manifestation. This should be considered in the clinical management of these patients.

Motor Control by Vision and the Evolution of Cerebral Lateralization

Chicks (4 or 5 days old), which are able to use either eye freely, use the right eye (RE) preferentially in approach to a food dish when a lid, which has to be removed, is visible during approach. They use the left eye (LE) instead when no manipulation is required, but the same dish is similarly visible. The RE is also used preferentially in selecting food grains scattered over the floor; RE use in these two contexts is thus associated with visual control which brings the bill in planned contact with a visible target rather than with approach to a site where it is anticipated that feeding will occur. Zebrafish also use the RE preferentially when preparing to bite a target; during purely visual examination of the same target, this preference disappears. This evidence is used together with evolutionary evidence to support a new hypothesis for the origin of cerebral lateralization: paired anterior eyes evolved in filter-feeding ancestors of the vertebrates as part of the acquisition of prey catching. A key use for early vision was to predict likely contact with prey so as to inhibit reflexes of rejection and avoidance normally elicitated by tactile input to the mouth and so to allow ingestion. Innervation of mouth structures by the left side of the CNS caused control of mouth reflexes to become predominantly a left CNS affair. As visual abilities developed this starting condition meant that control of manipulation (which is by the mouth for most vertebrates) remained predominantly with the left side of the CNS.

Isolation of primary open-angle glaucomatous trabecular meshwork cells from whole eye tissue

Isolation and culture of human trabecular meshwork (TM) cells from primary open-angle glaucomatous (POAG) tissue has proven difficult. The objective of this study was to directly compare the utility of two different isolation methods to obtain viable human TM cells from POAG whole eye tissue. Using a blunt dissection technique, human TM tissue was obtained from four pairs of donor eyes (67, 77, 81 and 82 years) with a documented history of POAG. TM tissue from one eye was explanted into tissue culture. TM from the contralateral eye was digested with a collagenase mixture and seeded onto culture plates. Primary cell isolates were obtained from all donors with both techniques. However, only cells obtained using the digestion method (3 of 4 TMs) could be passaged for expansion and freeze-downs (3 x 107 second passage cells/donor). None of the cells obtained from explanted TMs could be passaged. Cells from successful isolations were of uniform size, possessed typical TM morphology and had doubling times < 48 hours. These results demonstrate a clear advantage to digesting the extracellular matrix of glaucomatous TM tissue to obtain sufficient numbers of healthy cells for use in experiments. In contrast to cells obtained from explants, cells liberated from POAG TM tissue by digestion appear indistinguishable morphologically and behaviorally from "normal" TM cells.

Diurnal stability of refraction after implantation with intracorneal ring segments

Purpose To investigate diurnal changes in visual acuity and refraction in myopic eyes implanted with intracorneal ring segments (ICRS). Setting University of California San Diego Shiley Eye Center, La Jolla, California, and Emory University Vision Correction Center, Atlanta, Georgia, USA. Methods This prospective study involved 2 groups of patients who had ICRS (Intacs™) implantation and a follow-up of at least 6 months. The first group included 102 eyes of 51 bilaterally treated patients; the second group, 32 eyes of 16 unilaterally treated patients. Examinations including visual acuity, manifest refraction, and videokeratography were done in the morning and evening at least 9 hours apart on a single day. Refractive changes were analyzed by power vectors; multivariate statistics were used to determine the significance of change in any component of the spectacle prescription. Results In the bilateral treatment group, 97 eyes (95%) were within 1 line of spectacle-corrected visual acuity from morning to evening. The mean change in manifest refraction was −0.14 +0.08 × 4 and in spherical equivalent, −0.10 diopters (D) (σ = 0.3; range −0.750 to +0.875 D). Ninety-six eyes (94%) had a change in refraction within 0.50 D of spherical equivalent. There was no significant change in corneal power ( P = .20). In the unilateral treatment group, there was no significant difference between treated and untreated eyes in changes in spectacle-corrected visual acuity, manifest refraction, or corneal power and toricity ( P > .05). Conclusion No clinically significant diurnal variation in visual acuity or manifest refraction was observed after ICRS implantation or in untreated paired eyes. Moreover, the data suggest less diurnal change in visual acuity and refraction after ICRS implantation.

Effect of Healon and Viscoat on outflow facility in human cadaver eyes

PurposeTo compare the acute effects of Healon® (sodium hyaluronate) and Viscoat® (sodium chondroitin sulfate–sodium hyaluronate) on outflow facility in human cadaver eyes and determine which viscoelastic agent is least likely to cause an intraocular pressure (IOP) spike after cataract surgery. SettingThe Glaucoma Research Lab, University of Toronto, Ontario, Canada. MethodsIn this prospective paired study, 15 pairs of human cadaver eyes were used. Following the construction of a 3.0 mm scleral tunnel, 0.25 cc of Healon was injected into the anterior chamber of 1 eye and 0.25 cc of Viscoat was injected into the contralateral eye. The viscoelastic agents were removed from both eyes in a standardized fashion and the scleral tunnels closed. The eyes were then perfused at a constant IOP of 8.0 mm Hg, corresponding to 16.0 mm Hg in vivo. Outflow facility (μL/minute [min]/mm Hg) was recorded every 15 minutes for 24 hours using standard methods. ResultsOutflow facility in the Viscoat-treated eyes decreased appreciably for the first 3 hours, then recovered somewhat after 12 hours; facility in the Healon-treated eyes showed less of an overall decrease. Over the 24 hour perfusion period, mean outflow facility was 0.037 μL/min/mm Hg ± 0.015 (SD) in the Viscoat-treated eyes and 0.060 ± 0.012 μL/min/mm Hg in the Healon-treated eyes. Healon reduced outflow facility significantly less than Viscoat between 3.25 and 10.50 hours postoperatively (P < .05, 2-tailed t test). ConclusionsHealon reduced outflow facility less than Viscoat between 3.25 and 10.50 hours postoperatively.

Surgical prevention of posterior capsule opacification: Part 2: enhancement of cortical cleanup by focusing on hydrodissection

PurposeTo experimentally analyze the role and efficacy of hydrodissection in achieving maximal cortical cleanup. SettingCenter for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina, USA. MethodsPhacoemulsification and irrigation/aspiration were performed in 10 pairs of human eyes (20 eyes) obtained postmortem. Ten eyes had previous hydrodissection and 10 eyes, no hydrodissection. The time (seconds) required for complete lens substance removal in each procedure was measured. In addition, a qualitative evaluation of difficulty of surgery was noted. ResultsPhacoemulsification required 28.6% less time in eyes with previous hydrodissection than in those without. Irrigation/aspiration time was reduced by 50.9% when hydrodissection was performed. The total time of each procedure required for complete evacuation of the capsular bag was reduced by an average of 37.7% in eyes with hydrodissection. Furthermore, qualitatively the procedure was far easier, less stressful, and caused less posterior capsule stress or rupture when copious hydrodissection was performed. ConclusionsHydrodissection enhances the general safety and efficiency of cortical cleanup, especially at 12 o’clock. Hydrodissection is the best available, practical, immediately implementable, and inexpensive means to help remove equatorial E-cells and thus alleviate the incidence of posterior capsule opacification.

Isolation of primary open-angle glaucomatous trabecular meshwork cells from whole eye tissue

Purpose. Isolation and culture of human trabecular meshwork (TM) cells from primary open-angle glaucomatous (POAG) tissue has proven difficult. The objective of this study was to directly compare the utility of two different isolation methods to obtain viable human TM cells from POAG whole eye tissue. Methods. Using a blunt dissection technique, human TM tissue was obtained from four pairs of donor eyes (67, 77, 81 and 82 years) with a documented history of POAG. TM tissue from one eye was explanted into tissue culture. TM from the contralateral eye was digested with a collagenase mixture and seeded onto culture plates. Results. Primary cell isolates were obtained from all donors with both techniques. However, only cells obtained using the digestion method (3 of 4 TMs) could be passaged for expansion and freeze-downs (3 × 10 7 second passage cells/donor). None of the cells obtained from explanted TMs could be passaged. Cells from successful isolations were of uniform size, possessed typical TM morphology and had doubling times < 48 hours. Conclusion. These results demonstrate a clear advantage to digesting the extracellular matrix of glaucomatous TM tissue to obtain sufficient numbers of healthy cells for use in experiments. In contrast to cells obtained from explants, cells liberated from POAG TM tissue by digestion appear indistinguishable morphologically and behaviorally from “normal” TM cells.

Distribution of lead and transthyretin in human eyes.

The retinal pigment epithelium serves as a defensive barrier to the retina in the same way that the choroid plexus functions in the brain. Previous studies have shown that lead sequestration in the choroid plexus reduces the production and secretion of transthyretin by the choroid plexus. The purpose of this study was to investigate the distribution of lead and transthyretin in human eyes and to explore the potential effect of lead on transthyretin in human eyes. Eight pairs of human eyes were obtained from the New York City Eyebank within 24 hours of postmortem. The eyes were dissected to obtain the aqueous, vitreous, retina, and choroid. Lead and transthyretin concentrations in ocular tissues and liquids were determined by atomic absorption spectrophotometry for lead and radioimmunoassay for transthyretin. Lead accumulated in the retina at concentrations that were 166, 739, and 5 times higher than those in the aqueous, vitreous, and choroid, respectively (p < 0.05 for all comparisons). Lead concentrations in ocular tissues or intraocular liquids did not change as a function of age or gender. The concentration of transthyretin in the vitreous (14.4 +/- 5.1 SE microg/mL) was twice as much as in the aqueous (7.0 +/- 1.1SE microg/mL) and was significantly correlated to that in the retina (r = 0.93, p < 0.005). This study indicates that lead accumulates in human ocular tissues, particularly in the retina. The markedly elevated retina lead level and its relationship to ocular transthyretin and other macromolecules bear further investigation.

Stimulus deprivation myopia in human congenital ptosis: a preliminary report of 50 unilateral cases

OBJECTIVE. To investigate the frequency of hyperopia and suspected stimulus deprivation myopia in human congenital ptosis. METHODS. Ametropia was evaluated in both eyes of 50 patients with congenital ptosis. The age at investigation was one year and older, average 6 years and 10 months. The amount of refraction was documented as the spherical equivalent (100% cycloplegia). Differences between the paired eyes of 1.0 dpt or more were defined as anisometropia. Statistical analysis was performed using the chi-square and sign tests. RESULTS. The frequency of myopia was lower (7/50: 14%) than that of hyperopia (43/50: 86%) in the ptotic eye (p<0.001). However, myopia occurred more often in the ptotic eye (7/50: 14%) than in the fellow eye (3/50: 6%, p>0.3). Myopic anisometropia was found only in the ptotic eye (5/50 vs. 0/50, p = 0.06), but was not more frequent than hyperopic anisometropia: (5/50 vs. 9/50, p>0.4). A covered center of the pupil in 27 out of 50 eyes was not associated significantly with myopia (2 of 27 versus 5 of 23, p>0.2). Altogether, we found a significantly higher rate of myopia <-1 dpt and hyperopia > 2 dpt: 10% vs. 1.4% and 40% vs. 10.2% (p<0.001) in comparison with normal school children. CONCLUSION. In summary, the following three findings were noted, of which the first two were expected and the third was not. 1. Compared with the normal population, there was an overall higher frequency of myopia in unilateral congenital ptosis. 2. There was a higher frequency of myopia in the ptotic than in the fellow eye. 3. Compared with the normal population, there was also a higher frequency of hyperopia. The clinical presentation of human congenital ptosis may be influenced by compensating head posture, strabismus, accommodation and biochemical effects, and the condition may therefore differ from the classical well-defined animal model of stimulus deprivation myopia.

Evaluation and transplantation of corneas from pseudophakic donor eyes.

To evaluate the quality of corneal donor tissue from pseudophakic eyes for transplantation. Only capsular-supported posterior chamber pseudophakia was studied. Forty-five pairs of donor eyes were assessed and evaluated by standard Minnesota Lions Eye Bank (MLEB) protocol. Thirty-three pairs were unilaterally pseudophakic with the unoperated phakic eye used as a control eye. Twelve donors were bilaterally pseudophakic. All corneas were rated for corneal clarity, epithelial defects, stromal edema, Descemet's membrane folding, endothelial cell density (ECD), and cell damage by slit-lamp examination and specular microscopy. If the corneas were not transplanted, the endothelium was vital stained with trypan blue and counterstained with alizarin red S for quantitation, localization, and visualization of cell morphology and damage. Sixty-eight of the 90 corneas in this study did not meet transplantation criteria. A significant difference in ECD (>22%) and in overall corneal rating was found in seven (21%) of 33 pairs of unilateral pseudophakic donors. Fourteen corneal transplants were performed using corneas from the donors in this study. Nine corneas from pseudophakic donor eyes were transplanted, resulting in one primary graft failure reported. Corneas from pseudophakic donor eyes may need more extensive evaluation for endothelial viability than is currently required by eye bank standards.

Telemedicine Screening of Glaucoma

Glaucoma is a major cause of blindness. More than 80,000 Americans suffer permanent vision loss from the disease. Widespread screening is fundamental in limiting the incidence of glaucoma-associated blindness. This pilot study explored the use of stereo digital images taken at a primary care center for telemedicine review by an off-site specialist as a means of screening for glaucoma. Thirty-two diabetic patients were screened at a family medicine clinic. None had previously been diagnosed with glaucoma. A senior optometry student took stereoscopic digital and 35-mm optic disc photographs with a nonmydriatic retinal camera. The digital images were forwarded to a remote ophthalmologist for review. The conventional color stereo slide pairs of the same eyes were subsequently reviewed for comparison. Agreement on signs of glaucomatous disc changes between the two imaging systems was analyzed. Twenty-six of 32 eyes' digital and 35-mm photographs were analyzed. Six of 32 eyes (18.8%) could not be compared due to lack of matching 35-mm slides or digital images. Out of 26 eyes, lamina cribosa visibility was undeterminable in 8 eyes' digital images and 3 other eyes' 35-mm slides. Agreement among digital images and 35-mm slides of the remaining eyes was: 100%-vertical elongation, barring of vessels, bayoneting of vessels, and drance hemorrhage; 96.2%-focus notching of rim and rim pallor; 93.3%-lamina cribosa visability; 92. 3%-overpass cupping; 88.5%-focal enlargement; 84.6%-parapapillary halo; 80%-nerve fiber visibility; 65.4%-parapapillary atrophy. Parapapillary halo (p = 0.046) and nerve fiber layer visibility (p = 0.18) were detected on some 35-mm slides but not seen on matching digital views. Evaluations of cup-to-disc ratio (C/D) using both methods were in general agreement. However, some digital images were noted as too dark for assessing fine glaucomatous disc changes. Stereo digital images taken with a nonmydriatic camera by nonophthalmic photographers is a promising alternative for glaucoma screening in primary care settings. Telemedicine offers efficient communications with off-site glaucoma specialists. A larger study population is necessary to determine the overall effectiveness of using stereo digital imagery and teleophthalmology for glaucoma screening.

OPINION The case of the one-eyed brine shrimp: are ancient atavisms possible?

In the cyclopean mutant of the anostracan branchiopod Artemia franciscana, paired stalked eyes are replaced by a single, median, sessile, eye resembling that found in certain monocular branchiopod orders. This eye, its nerve supply, and skeletal support, comprise a perfect unit which appears to be a spontaneous atavism. However, according to recent calculations this cannot be so. These suggest that while re-activation of long-silent genes, on which atavisms depend, can occur after a lapse of up to 6 million years (My), this is impossible after 10 My unless the gene is maintained by active selection, which cannot apply here. However, the Anostraca is an old group, and the atavism (if such it be) is clearly very ancient. Efficient DNA repair, not considered in the calculations, offers a possible explanation of how silent genes may survive for longer than the suggested period of viability. Particularly intriguing is that a binocular condition is primitive and the cyclopean derived, which has remarkable evolutionary implications. It suggests two reversals during the history of the Anostraca—from paired sessile eyes to a long-extinct monocular condition such as prevails in certain other branchiopods, later to paired stalked eyes. Other ancient atavisms also challenge the claim that silent genes have short life spans. This problem, which has fundamental biological implications, is still sub-judice.