Prevalence of canine cataract: preliminary results of a cross-sectional study

Nutritional cataracts in a wolf litter treated by phacoemulsification

OBJECTIVE

To describe the clinical findings in a wolf litter with nutritional cataracts and determine the treatment outcomes after phacoemulsification.

PROCEDURE

Bilateral nutritional cataracts were diagnosed in four hand-fed 10-week-old wolves (Canis lupus). The information collected included signalment, physical and ophthalmic examination findings, ocular ultrasonography and electroretinography results, and postoperative outcomes.

RESULTS

All four wolves were rejected from the dam and hand raised with a commercial artificial milk replacer from 5 days of age until weaning at 6 weeks of age. At initial presentation, bilateral cataracts were observed in all patients (8/8 eyes), with vision deficits in three of the four wolves. The main ophthalmic anomalies were mature cataracts with lens-induced uveitis (3/8 eyes, two wolves), immature cataracts (1/8 eyes, one wolf), and perinuclear and posterior cortical/subcapsular lens opacities (4/8 eyes, three wolves). Three of the four wolves (six eyes) underwent bilateral one-handed phacoemulsification with intraocular lens implantation. At the last examination 2 months following surgery, all operated eyes (6/6) were visual, Elschnig pearl proliferation was present in 2/6 eyes, and mild posterior capsular opacification was observed in 6/6 eyes. In the nonoperated wolf, the cataracts remained stable and did not affect the visual axis of either eye.

CONCLUSIONS

This is the first description of phacoemulsification surgery in wolves. Phacoemulsification is a viable treatment option for captive wolves with nutritional cataracts. Special attention should be paid to hand-raised cubs to ensure that adequate amino acid levels are present in artificial milk.

The use of sub-Tenon's anesthesia versus a low-dose neuromuscular blockade for canine cataract surgery: A comparative study of 224 eyes

OBJECTIVE

Assess the utility of a Sub-Tenon's anesthesia (STA) protocol to provide suitable operating conditions for canine cataract surgery and compare it to an alternative low-dose neuromuscular blockade (LD-NMB) protocol used for canine cataract surgery.

PROCEDURES

Clinical study of dog eyes undergoing cataract surgery with either an STA or LD-NMB protocol. While intraoperative vitreal expansion scores and intraoperative complications were collected prospectively, globe position, intraocular pressure, return of vision, and postoperative complications were collected retrospectively. Statistical testing was used to compare results between the STA and the LD-NMB groups for the data available.

RESULTS

A total of 224 eyes from 126 dogs were assessed, with 133/224 (59.4%) eyes from 99/126 (78.6%) dogs receiving STA and 91/124 (40.6%) eyes from 72/126 (57.1%) dogs receiving LD-NMB. Forty-five of these dogs (45/126; 37.7%) received STA for one eye and LD-NMB for the other eye. There was no significant change in intraocular pressure measurements following STA administration. This was not measured for the LD-NMB group. The globe achieved a central position in 110/133 (82.7%) of eyes that received STA. This was not measured for the LD-NMB group. Intraoperative vitreal expansion scores were slightly higher in STA-treated eyes compared to LD-NMB-treated eyes. The intraoperative complication rate for STA-treated eyes was higher (73/133; 54.8%) compared to NMB-treated eyes (12/91; 13.2%). The most common intraoperative complication for STA was chemosis (64/133; 48.1%), the risk of which increased with an increase in the volume of local anesthetic injected. The post-operative complication rate was higher in STA-treated eyes (28/133; 21.1%) compared to NMB-treated eyes (16/91; 17.6%). Post-operative corneal ulceration was the most common postoperative complication in STA-treated eyes (6/133; 4.5%).

CONCLUSION

The STA protocol described resulted in suitable operating conditions, but more intraoperative and postoperative complications compared to the LD-NMB protocol. Despite these complications, the STA protocol did not cause a significant deleterious impact on post-operative outcomes as defined in the present study.

Quantifying refractive error in companion dogs with and without nuclear sclerosis: 229 eyes from 118 dogs

OBJECTIVE

To evaluate the relationship between nuclear sclerosis (NS) and refractive error in companion dogs.

ANIMALS STUDIED

One hundred and eighteen companion dogs.

PROCEDURES

Dogs were examined and found to be free of significant ocular abnormalities aside from NS. NS was graded from 0 (absent) to 3 (severe) using a scale developed by the investigators. Manual refraction was performed. The effect of NS grade on refractive error was measured using a linear mixed effects analysis adjusted for age. The proportion of eyes with >1.5 D myopia in each NS grade was evaluated using a chi-square test. Visual impairment score (VIS) was obtained for a subset of dogs and compared against age, refractive error, and NS grade.

RESULTS

Age was strongly correlated with NS grade (p < .0001). Age-adjusted analysis of NS grade relative to refraction showed a mild but not statistically significant increase in myopia with increasing NS grade, with eyes with grade 3 NS averaging 0.58-0.88 D greater myopia than eyes without NS. However, the myopia of >1.5 D was documented in 4/58 (6.9%) eyes with grade 0 NS, 12/91 (13.2%) eyes with grade 1 NS, 13/57 (22.8%) eyes with grade 2 NS, and 7/23 (30.4%) eyes with grade 3 NS. Risk of myopia >1.5 D was significantly associated with increasing NS grade (p = .02). VIS was associated weakly with refractive error, moderately with age, and significantly with NS grade.

CONCLUSIONS

NS is associated with visual deficits in some dogs but is only weakly associated with myopia. More work is needed to characterize vision in aging dogs.

Effect of oral antioxidants on the progression of canine senile cataracts: a retrospective study

Background

Cataracts are the leading cause of impaired vision or blindness in dogs. There are many antioxidants that can prevent cataract progression, but whether they are clinically effective in dogs has not been established.

Objectives

To analyze the delaying or preventing effect of oral antioxidants on canine senile cataracts through retrospective analysis.

Methods

Medical records of dogs from January 1, 2015 to July 10, 2020 were reviewed. Dogs that were 8 yr of age or older with senile cataracts were included in this study. The dogs were divided into two treatment groups (dogs administered with Ocu-GLO supplement and dogs administered with Meni-One Eye R/C supplement) and a control group (dogs that were not administered any supplement). Dogs with incipient and immature cataracts were included in this study. Altogether, 112 dogs (156 eyes) with incipient cataracts and 60 dogs (77 eyes) with immature cataracts were included. The period of time that cataracts progressed from incipient to immature, and from immature to mature was recorded for each dog.

Results

There was no significant delaying effect on the progression of incipient cataracts. However, both Ocu-GLO (hazard ratio = 0.265, p = 0.026) and Meni-One (hazard ratio = 0.246, p = 0.005) significantly delayed the progression of immature cataracts compared to the control group.

Conclusions

Although there was no significant delaying effect of oral antioxidants on incipient cataract progression, antioxidants could be used to delay the progression of senile immature cataract.

Roles of plant-based ingredients and phytonutrients in canine nutrition and health

Dogs possess the ability to obtain essential nutrients, established by the Association of American Feed Control Officials (AAFCO), from both animal‐ and plant‐based ingredients. There has been a recent increase in the popularity of diets that limit or completely exclude certain plant‐based ingredients. Examples of these diets include ‘ancestral’ or ‘evolutionary’ diets, raw meat‐based diets and grain‐free diets. As compared to animal sources, plant‐derived ingredients (including vegetables, fruits, grains, legumes, nuts and seeds) provide many non‐essential phytonutrients with some data suggesting they confer health benefits. This review aims to assess the strength of current evidence on the relationship between the consumption of plant‐based foods and phytonutrients (such as plant‐derived carotenoids, polyphenols and phytosterols) and biomarkers of health and diseases (such as body weight/condition, gastrointestinal health, immune health, cardiovascular health, visual function and cognitive function) from clinical trials and epidemiological studies. This review highlights the potential nutritional and health benefits of including plant‐based ingredients as a part of balanced canine diets. We also highlight current research gaps in existing studies and provide future research directions to inform the impact of incorporating plant‐based ingredients in commercial or home‐prepared diets.

Aggressive behaviour is affected by demographic, environmental and behavioural factors in purebred dogs

Aggressive behaviour is an unwanted and serious problem in pet dogs, negatively influencing canine welfare, management and public acceptance. We aimed to identify demographic and environmental factors associated with aggressive behaviour toward people in Finnish purebred pet dogs. We collected behavioural data from 13,715 dogs with an owner-completed online questionnaire. Here we used a dataset of 9270 dogs which included 1791 dogs with frequent aggressive behaviour toward people and 7479 dogs without aggressive behaviour toward people. We studied the effect of several explanatory variables on aggressive behaviour with multiple logistic regression. Several factors increased the probability of aggressive behaviour toward people: older age, being male, fearfulness, small body size, lack of conspecific company, and being the owner's first dog. The probability of aggressive behaviour also differed between breeds. These results replicate previous studies and suggest that improvements in the owner education and breeding practices could alleviate aggressive behaviour toward people while genetic studies could reveal associated hereditary factors.

Retrospective analysis of ocular disease in a population of captive pteropodid bats, 2003-2020

OBJECTIVE

To perform retrospective analysis of captive pteropodid bats presented to the University of Florida for ocular or adnexal disease from 2003-2020.

ANIMALS STUDIED

Twenty-four individuals from seven species were included.

PROCEDURES

Records were analyzed for disease process, methods of treatment, and surgical techniques and complications.

RESULTS

The most frequently reported abnormality was corneal disease (79%), followed by cataracts (54%), and uveitis (42%). Corneal disease was primarily attributed to either trauma or exposure keratitis secondary to buphthalmia. The majority of uveitis appeared to be lens-induced. Five cases (21%) of glaucoma were reported, all of which accompanied lens luxation. Of the seven enucleations performed, six had post-operative complications (85.7%), including swelling at the surgical site, seroma formation, and bacterial infection. There was no significant relationship between age and trauma, age and cataract formation, sex and trauma, or species and cataract formation.

CONCLUSIONS

The most common underlying cause of ocular pathology in these cases was trauma. While the bats tolerated topical and systemic treatment well, individual temperament must be taken into account when developing treatment plans, and prevention of injury is the most effective management strategy.

The ophthalmic health and refractive state of working dogs in South Brazil

Background:

Working dogs, such as police dogs and guide dogs, have important roles in the contemporary society by performing specific and demanding jobs. Ocular health and the maintenance of good visual acuity are imperative to strong work performance and thus human safety.

Aim:

The aim of this study was to assess ophthalmic abnormalities and refractive errors in police and guide dogs in Brazil.

Methods:

A total of 71 dogs (141 eyes) were evaluated. Ten were guide dogs and 61 were police dogs. The work performance was assessed by a questionnaire to each dog’s handler/owner. All the dogs underwent a complete ocular examination, and abnormalities were classified by condition, if they were active or inactive and if they were located within the visual axis. In addition, 62 dogs were evaluated by streak retinoscopy for refractive errors.

Results:

Ophthalmic abnormalities were detected in 38 (54%) dogs, of which 23 were considered inherited, 25 were considered active, and 10 were located within the visual axis. Incipient cataracts were the most prevalent abnormality. No guide dog had an abnormality within the visual axis. The most common refractive error was myopia with the median and interquartile range of –0.75 ± 0.75 diopters; among these, police dogs had –1.0 ± 0.5 diopters, whereas guide dogs +0.38 ± 0.75 diopters. Police dogs tended to be slightly myopic and guide dogs were emmetropic.

Conclusion:

Despite finding a considerable number of ophthalmic abnormalities and refractive error, work performance was good with no signs of visual impairment in any dog. Regular ophthalmic examinations are advised for working dogs, and an exclusion of severely affected dogs from breeding programs is recommended.

Age-related changes in eye lens biomechanics, morphology, refractive index and transparency

Life-long eye lens function requires an appropriate gradient refractive index, biomechanical integrity and transparency. We conducted an extensive study of wild-type mouse lenses 1-30 months of age to define common age-related changes. Biomechanical testing and morphometrics revealed an increase in lens volume and stiffness with age. Lens capsule thickness and peripheral fiber cell widths increased between 2 to 4 months of age but not further, and thus, cannot account for significant age-dependent increases in lens stiffness after 4 months. In lenses from mice older than 12 months, we routinely observed cataracts due to changes in cell structure, with anterior cataracts due to incomplete suture closure and a cortical ring cataract corresponding to a zone of compaction in cortical lens fiber cells. Refractive index measurements showed a rapid growth in peak refractive index between 1 to 6 months of age, and the area of highest refractive index is correlated with increases in lens nucleus size with age. These data provide a comprehensive overview of age-related changes in murine lenses, including lens size, stiffness, nuclear fraction, refractive index, transparency, capsule thickness and cell structure. Our results suggest similarities between murine and primate lenses and provide a baseline for future lens aging studies.

The hypoattenuating ocular lens on CT is not always due to cataract formation

Hypoattenuating ocular lenses on CT have been described with cataract formation in humans, however published studies are currently lacking regarding this finding in veterinary patients. The purpose of this retrospective and prospective study was to describe the varying CT appearances of the ocular lens in vivo, and investigate the causes for CT density variations in a population of cats and dogs. A total of 102 canine and feline patients with CT of the head acquired at the authors' hospital between May 2011 and March 2019 were included. A bilateral hypoattenuating halo surrounding an isoattenuating to mildly hypoattenuating core was described in the ocular lens center of every cat in which a Philips brand proprietary image construction filter was used. A similar but more varied hypoattenuating region was noted in the lenses of 45.8% of dogs where the same filter was applied, as well as 43.8% of dogs with a second, similar filter. Ophthalmic examination of three live cats and one dog with hypoattenuating lenses demonstrated normal lens translucency, excluding the presence of cataract. The effect of different proprietary filters on lens appearance was also described in three fresh cadavers with normal lenses identified on ophthalmic, macroscopic, and microscopic examination. Etiology of the hypoattenuating areas within the ocular lens was not conclusively determined. Recognition that such a variant may be seen in the absence of cataract is important, in order to prevent misdiagnosis.

Ocular translational science: A review of development steps and paths

Developing successful drug delivery methods is challenging for any tissue, and the eye is no exception. Translating initial concepts into advanced technologies treating diseases in preclinical models and finally into functional and marketable products for humans can be particularly daunting. While referring to specific ophthalmic companies and products, this review considers key exchanges that lead to successful translation. By building on basic science discoveries in the academic setting, applied science can perform proof-of-concept work with simple, benchtop experiments. Eventually, simple models need to be translated to more robust ones where cells, tissues, and entire organisms are incorporated. Successful translation also includes performing due diligence of the intellectual property, understanding the market needs, undertaking clinical development, meeting regulatory requirements, and eventually scale up manufacturing. Different stages of the translation can occur in different environments, including moving from academia to industry, from one company to another, or between veterinary and human applications. The translation process may also rely on contract organizations to move through the complex landscape. While the path to a commercial, marketable product may not look the same each time, it is important to design a development plan with clear goals and milestones to keep on track.

Epidemiology of ocular disorders presumed to be inherited in three large Italian dog breeds in Italy

OBJECTIVE

To describe the epidemiology and the types of eye disorders that are presumed to be inherited (PIED) in three large Italian dog breeds.

ANIMALS

Three large Italian dog breeds: Neapolitan Mastiff (FCI code: 197), Maremma Sheepdog (FCI code: 201), and Italian Corso dog (FCI code: 343).

PROCEDURES

All dogs that underwent a complete ophthalmic examination between 1992 and 2012 were included in this prospective observational study. The prevalence of eye disorders with 95% confidence intervals was reported for presumed healthy dogs and for dogs referred to a veterinary center for an ophthalmic consultation. Univariate and multivariate logistic regression techniques were used to generate odds ratios.

RESULTS

Of 605 dogs examined during the study period, 351 dogs were affected by at least one PIED (58%; 95% CI: 54-62%). The prevalence of PIED was significantly lower in dogs presented for ophthalmic examination (53.8%) as compared to presumed healthy dogs (62.2%)(OR: 1.4; 95% CI: 1.02-1.9; P = 0.037). Also after multivariate adjustment for the period of observation, the odds of Neapolitan Mastiff (92.1%; OR: 21.4; 95% CI: 11.1-41.4) and of Cane Corso (57.7%; OR: 2.5; 95% CI: 1.7-3.6) suffering a PIED were greater than the Maremma Sheepdog (35.4%). The most common PIED in each breed were entropion (24.3% of all the PIED) in the Neapolitan Mastiff, ectropion (36.6%) in the Corso dog, and cataract (27.9%) in the Maremma Sheepdog.

CONCLUSIONS

Clinicians should be aware that three large Italian dog breeds frequently suffer PIED. Breed standards should be reconsidered, and breeding programs should be directed at limiting such disorders.

Prevalence of common canine digestive problems compared with other health problems in teaching veterinary hospital, Faculty of Veterinary Medicine, Cairo University, Egypt

Aim:

The present study was conducted to ascertain the prevalence of common digestive problems compared to other health problems among dogs that were admitted to the teaching veterinary hospital, faculty of veterinary medicine, Cairo University, Egypt during 1 year period from January to December 2013. Also, study the effect of age, sex, breeds, and season on the distribution of digestive problems in dogs.

Materials and Methods:

A total of 3864 dogs included 1488 apparently healthy (included 816 males and 672 females) and 2376 diseased dogs (included 1542 males and 834 females) were registered for age, sex, breed, and the main complaint from their owners. A complete history and detailed clinical examination of each case were applied to the aids of radiographic, ultrasonographic, and endoscopic examination tools. Fecal examination was applied for each admitted case. Rapid tests for parvovirus and canine distemper virus detection were also performed.

Results:

A five digestive problems were commonly recorded including vomiting, diarrhea, concurrent vomiting with diarrhea, anorexia, and constipation with a prevalence (%) of 13.6, 19.1, 10.1, 13.1, and 0.5 respectively while that of dermatological, respiratory, urinary, neurological, cardiovascular, auditory, and ocular problems was 27.9, 10.5, 3.3, 0.84, 0.4, 0.25, and 0.17 (%) respectively. This prevalence was obtained on the basis of the diseased cases. Age and breed had a significant effect on the distribution of digestive problems in dogs (p<0.001). Gender had an effect on the distribution of digestive problems with significant (p≤0.01) while season had a non-significant effect (p>0.05) on the distribution of such problems.

Conclusion:

Digestive problems were the highest recorded problems among dogs, and this was the first records for such problems among dogs in Egypt. Age, gender, and breeds had a significant effect on the distribution of the digestive problems in dogs while season had a non-significant effect on the distribution of such problems. The present data enable veterinarians in Egypt to ascertain their needs for diagnostic tools and medication that must be present at any pet clinic.

Genes against aging

Individual mutations in mice can slow aging: They extend life span by retarding a wide range of harmful, age-dependent changes in multiple cells and tissues. Evolutionary changes-by definition, changes in DNA sequence-can lead to even more dramatic postponement of age-dependent deterioration. Genetic variation within a species, for example among breeds of dogs, can also lead to major changes in aging rate, although there is not yet any strong evidence for similar genetic variation that modulates aging in rodents or humans. This essay compares different strategies for using genetic information to clarify questions in biogerontology, suggesting an emphasis on genes that can retard multiple forms of age-dependent dysfunction in parallel.

Age-related cataract in dogs: a biomarker for life span and its relation to body size

Clinical data from 72 dog breeds of varying size and life expectancy were grouped according to breed body mass and tested for prevalence at ages 4 to 5, ages 7 to 10, and lifetime incidence of non-hereditary, age-related cataract (ARC). The incidence of ARC was found to be directly related to the relative life expectancies in the breed groups: The smallest dog breeds had a lower ARC prevalence between ages 4 and 5 than mid-size breeds and these, in turn, a lower prevalence than the giant breeds. A similar sequence was evident for ages 7 to 10 and for overall lifetime incidence of ARC. These differences became more significant when comparing small and giant breeds only. We could also confirm the inverse relationship between body size and life expectancy in these same sets of dog breeds. Our results show that body size, life expectancy, and ARC incidence are interrelated in dogs. Given that ARC has been shown to be at least partially caused by oxidative damage to lens epithelial cells and the internal lens, we suggest that it can be considered not only as a general biomarker for life expectancy in the canine and possibly other species, but also for the systemic damages produced by reactive oxygen species. This suggests new approaches to examine the gene expression pathways affecting the above-noted linkages.

Resveratrol prevention of oxidative stress damage to lens epithelial cell cultures is mediated by forkhead box O activity

PURPOSE

To evaluate the potential role that FoxO transcription factors play in modulating resveratrol's protective effects against oxidative stress in lens epithelial cells.

METHODS

Primary human or porcine lens epithelial cells (LECs) were treated with resveratrol (RES) 25 μM and incubated under either physiologic (5%) or chronic hyperoxic (40%) oxygen conditions. Acute oxidative stress was applied using 600 μM H(2)O(2). Changes in expression of FoxO1A, FoxO3A, and FoxO4 were analyzed. The production of intracellular reactive oxygen species (iROS), SA-β-galactosidase (SA-β-gal) activity, and autofluorescence (AF) was assessed by flow cytometry. SiRNAs of FoxO1A, FoxO3A, and FoxO4 were used to study the roles that these transcription factors play in resveratrol's protective effects against cell death induced by oxidative stress.

RESULTS

RES incubation under 40% oxygen increased the expression of FoxO1A, FoxO3A, and FoxO4. RES also increases mitochondrial membrane potential under 5% and/or 40% O(2) conditions and significantly decreased iROS, SA-β-gal, and AF normally induced by hyperoxic conditions. While RES had a mild pro-apoptotic effect in nonstressed cells, it significantly prevented apoptosis induced by H(2)O(2) stress. SiRNA inhibition of FoxO1A, FoxO3A, and FoxO4 not only led to loss of the anti-apoptotic effects of RES in stressed cells but actually exhibited a mild pro-apoptotic effect.

CONCLUSIONS

RES exerts a protective effect against oxidative damage in LEC cultures. The levels of expression of FoxO1A, FoxO3A, and FoxO4 appear to play a central role in determining the pro- or anti-apoptotic effects of RES. This has implications for future studies on oxidative stress-related lenticular disorders such as cataract formation.

Preservation of femoral bone thickness in middle age predicts survival in genetically heterogeneous mice

To see whether age-related changes in bone could predict subsequent lifespan, we measured multiple aspects of femur size and shape at 4, 15, and 24 months of age in genetically heterogeneous mice. Mice whose cortical bone became thicker from 4 to 15 months, associated with preservation of the endosteal perimeter, survived longer than mice whose endosteal cavity expanded, at the expense of cortical bone, over this age range. Femur size at age 4 months was also associated with a difference in life expectancy: mice with larger bones (measured by length, cortical thickness, or periosteal perimeter) had shorter lifespans. Femur length, midlife change in cortical bone thickness, and midlife values of CD8 T memory cells each added significant power for longevity prediction. Mice in the upper half of the population for each of these three endpoints lived, on average, 103 days (12%) longer than mice with the opposite characteristics. Thus, measures of young adult bone dimensions, changes as a result of bone remodeling in middle age, and immunological maturation provide partially independent indices of aging processes that together help to determine lifespan in genetically heterogeneous mice.

A- and B-modes echobiometry in cataractous and noncataractous eyes of English Cocker Spaniel dogs

A- and B-modes ultrasonographic changes in the thickness of various structures of the eyeball in male and female English Cocker Spaniel dogs with and without nondiabetic cataracts were evaluated. Sixteen dogs with cataracts (32 eyes) and seven normal dogs (14 eyes) older than eight years were selected. A- and B-modes ultrasonography was performed with a 10MHz transducer. Data was statistically evaluated by one way ANOVA. Mean and standard deviations of various ocular structures for dogs with and without cataracts were, respectively, anterior chamber: 3.041±0.828mm, 3.373±1.040mm; lens: 6.817±1.117mm, 7.062±0.477mm; vitreous: 10.056±0.754mm, 9.523±0.705mm; and axial length: 19.909±1.103mm, 19.958±1.050mm. Ocular measurements between right and left eyes, males and females, as well as in eyes with and without cataract were not different (P>0.05).

Risk factors associated with cataracts and lens luxations in captive pinnipeds in the United States and the Bahamas

OBJECTIVE

To determine risk factors for lens luxation and cataracts in captive pinnipeds in the United States and the Bahamas.

DESIGN

Cross-sectional study.

ANIMALS

111 pinnipeds (99 California sea lions [Zalophus californianus], 10 harbor seals [Phoca vitulina], and 2 walruses [Odobenus rosmarus]) from 9 facilities.

PROCEDURES

Eyes of each pinniped were examined by a veterinary ophthalmologist for the presence of cataracts or lens luxations and photographed. Information detailing husbandry practices, history, and facilities was collected with a questionnaire, and descriptive statistical analyses were performed for continuous and categorical variables. Odds ratios and associated 95% confidence intervals were estimated from the final model.

RESULTS

Risk factors for lens luxation, cataracts, or both included age >or= 15 years, history of fighting, history of ocular disease, and insufficient access to shade.

CONCLUSIONS AND CLINICAL RELEVANCE

Diseases of the lens commonly affect captive pinnipeds. Access to UV-protective shade, early identification and medical management of ocular diseases, and prevention of fighting can limit the frequency or severity of lens-related disease in this population. An extended life span may result from captivity, but this also allows development of pathological changes associated with aging, including cataracts.

Oxidative stress and the eye

Oxidative and particularly photo-oxidative processes are critical factors many ocular conditions but are often poorly recognized by those investigating ocular disease. The author discusses oxidative stress in inflammatory processes of the conjunctiva, cornea, and uvea; in cataract formation in the lens; in retinal degeneration; and in optic nerve pathologic conditions, inflammatory in optic neuritis and degenerative in glaucoma.

Outcomes of dogs presented for cataract evaluation: a retrospective study

Two hundred and forty-four dogs were evaluated for cataracts at the University of Tennessee from January 2001 to December 2002. Fifty-four canine breeds were affected. Odds ratios for cataracts were significantly higher for six purebred dogs (including the cocker spaniel, miniature schnauzer, toy poodle, Boston terrier, miniature poodle, and bichon frise) compared with mixed-breed dogs. One hundred fifty-nine dogs did not have cataract surgery. The most common reason for dogs not having surgery was retinal degeneration (n=66).

Ultraviolet irradiation up-regulates telomerase transcription and activity in lens epithelial cells

PURPOSE

Ultraviolet irradiation (UVR) increases telomerase activity in various cell types including skin, a sun-exposed organ. The lens is also continually exposed to UVR and we hypothesized that lenses exposed to UVR would have increased telomerase activity, with up-regulated TERT and TR, the two main components of the telomerase holoenzyme. To evaluate whether the cornea would protect lenses from such changes, whole globes, as well as isolated lenses, were exposed to UVR, and lenses were evaluated for changes in telomerase activity.

METHODS

There were three parts to this project. The first part of this experiment evaluated freshly harvested normal adult canine lenses exposed to 0, 300, 600, or 1200 J/m(2) UVR, and then allowed to recover for 1, 2, 3 and 4 h. Since only 600 J/m(2) UVR increased telomerase activity, four more postexposure recovery time-points for this UVR dose were evaluated: 10 min, 30 min, 8 h and 24 h. The second part of this experiment used freshly enucleated whole canine globes exposed to 0, 50, 100, 150, 300, 600 or 1200 J/m(2) and incubated overnight; lens epithelial cells (LEC) were evaluated for telomerase activity. The third part evaluated lenses that were exposed to 0 or 600 J/m(2) UVR, and then allowed to recover for 8 and 24 h, before TERT and TR mRNA levels were measured.

RESULTS

Isolated lenses exposed to 600 J/m(2) UVR had significantly higher telomerase activity than unexposed controls and other UVR doses, at all time-points except 24 h postexposure. Lenses from whole globes exposed to UVR showed a dose-dependent increase in telomerase activity except at 50 J/m(2) and 1200 J/m(2). Isolated lenses exposed to 600 J/m(2) UVR and then allowed to recover for 8 and 24 h significantly up-regulated TERT and TR mRNAs compared to unexposed control lenses.

CONCLUSIONS

Telomerase activity is regulated at both the transcriptional and post-translational levels in canine LEC. Previous work in our laboratory showed dose, time, and age-dependent changes in telomerase activity in the lens. The present study showed that TERT and TR mRNA transcription was increased for up to 24 h following an acute dose of UVR. Both telomerase activity and TERT and TR mRNA levels were elevated until 24 h post-UVR exposure, TERT in combination with TR functions in proliferation-related telomerase activity, but TERT alone has an anti-apoptotic function and its up-regulation may protect LEC from the acute effects of UVR. We are continuing to evaluate the mechanisms by which telomerase is regulated in normal and cataractous LEC.

Age-related cataract progression in five mouse models for anti-oxidant protection or hormonal influence

Five mouse models with known alterations of resistance to oxidative damage were compared by slit lamp examination for the presence and degree of advancement of age-related cataract in young adult and old animals along with wild type controls. A group of young and old normal C57BL/6Jax mice were examined first to constitute a standard, and they were found to exhibit age-related cataract development. Following this, four models on the C57BL/6 background with imposed genetic alterations affecting anti-oxidant enzyme presence or activity, and one outbred model in which a deletion blocked the growth hormone/IGF-1 axis, were similarly examined. There was no evidence of foetal or juvenile cataract development in any of these models, and an age-related severity for lens opacities was shown between young adult and old mice in all groups. Model 1, mice null for the anti-oxidant gene glutathione peroxidase-1 (GPX1) had significantly advanced cataracts in older mice vs. same age controls. In mouse model 2 hemizygous knockout of SOD2 (MnSOD) did not affect age-related cataract development. In model 3 combining the GPX1 and SOD2 deficiencies in the same animal did not advance cataract development beyond that of the GPX1 null alone. In model 4 the addition of anti-oxidant protection in the lens by transfection of human catalase targeted only to the mitochondria resulted in a significant delay in cataract development. The 5th model, growth hormone receptor knockout (GHR-/-) mice, also demonstrated a significant reduction in age-related cataract development, as well as dwarfism. These findings, in general, support the oxidative theory of age-related cataract development. The exception, the partial deletion of SOD2 in the hemizygous KO model, probably did not represent a sufficiently severe deprivation of anti-oxidant protection to produce pathologic changes in the lens.