The lens and cataracts.

It is conservatively estimated that some form of lens opacity is present in 5% to 7% of horses with otherwise clinically normal eyes.These opacities can range from small epicapsular remnants of the fetal vasculature to dense and extensive cataract. A cataract is defined technically as any opacity or alteration in the optical homogeneity of the lens involving one or more of the following: anterior epithelium, capsule, cortex, or nucleus. In the horse, cataracts rarely involve the entire lens structure (ie, complete cataracts) and are more usually localized to one anatomic landmark or sector of the lens. Complete cataracts are invariably associated with overt and significant visual disability. Focal or incomplete cataracts alone seldom cause any apparent visual dysfunction in affected horses,however.     

Diagnostic ultrasonography of equine lens and posterior segment abnormalities

Purpose To define the indications for equine ocular ultrasonography and to provide representative ultrasonographic images of lens and posterior segment diseases. Methods Retrospective study. Equine medical records dating from January 1983 to March 2001 were reviewed. All cases that: (1) had a lens and/or posterior segment abnormality; and (2) received a complete ophthalmic examination and ocular ultrasonography were included. Results Forty‐three cases (n = 64 eyes) out of 112 total cases of equine lens and/or posterior segment abnormalities qualified. The following conditions were identified ultrasonographically in order of decreasing frequency: cataracts, vitreal opacities, retinal detachment, lens luxation, endophthalmitis, microphthalmos, choroiditis, lens rupture, lenticonus, buphthalmos and phthisis bulbi. Ultrasonography often enabled diagnoses to be made in the presence of anterior opacities in both surgical (pre and/or postoperatively) and nonsurgical cases. Additional ocular conditions were identified in adults with cataracts more frequently than in foals with cataracts. Conclusions Cataracts were the most common lens abnormality identified in horses that received ocular ultrasound examination. Cataracts were commonly found in association with other ocular abnormalities. Ultrasonography was a practical and effective method of evaluating the lens and posterior segment, particularly in cases with anterior opacities. Ultrasonography also provided critical information with regard to the potential for surgical removal of cataracts and was a valuable component of postsurgical follow‐up.     

Ultrasonographic Evaluation of Equine Ocular Diseases: A Retrospective Study of 38 Eyes

Ocular ultrasonography in horses represents a valuable imaging diagnostic tool for the diagnosis of intraocular and periocular diseases, particularly when cornea or lens opacities preclude ophthalmoscopy of deeper structures. The authors studied normal and pathological aspects of the eye. Nineteen horses with opacities of the dioptric structures underwent an ultrasound examination. This technique allowed the diagnosis of a posterior synechia (1), cataracts (8), vitreous opacities (6), retinal detachment (3), and a foreign body (1). Ultrasonography provided helpful information about the structure and vascular pattern when the conventional ophthalmic evaluation was unable to achieve a correct diagnosis.     

Topical KINOSTAT™ ameliorates the clinical development and progression of cataracts in dogs with diabetes mellitus

Objective To determine whether topical administration of the aldose reductase inhibitor Kinostat™ can ameliorate the onset or progression of cataracts in dogs with naturally occurring diabetes mellitus (DM). Materials and Methods A randomized, prospective, double‐masked placebo control pilot study was conducted with 40 dogs newly diagnosed with DM with no or minimal lens changes. Twenty‐eight dogs received Kinostat™ and 12 dogs received placebo. Procedures Owners administered the agent into both eyes three times daily for 1 year and compliance was monitored with log sheets. Complete ophthalmic examinations were performed on dilated eyes at the time of enrollment and 1, 2, 3, 6, and 12 months into treatment. Cataract severity was assessed on a scale of 0–3. At 12 months, full bloodwork, including HbA1C and blood Kinostat^TM levels were performed. Results After 12 months of treatment, the cataract score in the placebo group significantly increased with seven dogs (14 eyes) developing mature cataracts, two dogs (4 eyes) developing cortical opacities, and one dog (2 eyes) developing equatorial vacuoles with mild punctate cortical opacities. In contrast, the cataract score in the Kinostat^TM treated dogs was significantly less with seven developing anterior equatorial vacuoles, two developing incipient anterior cortical cataracts, and four developing mature cataracts. In fact, the cataract scores of the Kinostat^TM group at 12 months did not significantly increase from the score at the time of enrollment. The HbA1C values between the two groups after 12 months of treatment were similar, and no blood levels of Kinostat^TM were found in any enrolled dog. Conclusion The onset and/or progression of cataracts in dogs with DM can be significantly delayed by topical administration of Kinostat™.     

Efficacy of zinc citrate ascorbate for treatment of canine cataracts

Efficacy of zinc citrate ascorbate was evaluated in 146 dogs (265 eyes) that had various lens opacities. Zinc citrate ascorbate or saline placebo drops were applied topically once or twice daily for 4 to 31 weeks. Of 138 eyes treated with zinc citrate ascorbate, 86 eyes (62.3%) had no change, 48 eyes (34.8%) had increased lens opacity, and 4 eyes (2.9%) had decreased lens opacity. Of 127 eyes treated with a saline placebo, 99 eyes (77.9%) had no change, 25 eyes (19.7%) had increased lens opacity, and 3 eyes (2.4%) had decreased lens opacity. Zinc citrate ascorbate drops were not significantly (P = less than 0.05) more effective in clearing cataracts than were saline drops. Seemingly, zinc citrate ascorbate drops may have caused lens opacities to increase in area and density.     

Pulverulent nuclear cataract in the Norwegian buhund

Pulverulent cataracts were diagnosed in 52 of 102 Norwegian buhunds, with both sexes being equally affected. All the dogs were otherwise considered clinically healthy. Initial lens changes were visible from six and a half weeks of age as small dots parallel to the suture lines behind the nucleus. Gradually, the opacities along the suture lines became more opaque until, by the age of four to five and a half years, they had progressed to involve the fetal nucleus which then resembled a ball of candy floss. The outer part, the adult nucleus, usually remained clear, and the cortex was not involved. The ages of the dogs in the present study ranged from three and a half weeks to 12 years at first examination. An outcross of an affected bitch to a mixed-breed dog resulted in three puppies, of which two were affected. The retinas could be evaluated in all the examined dogs, and revealed no abnormalities except for one case of focal retinopathy. In addition to the pulverulent cataracts, 10 cases of cortical cataracts were diagnosed, three of which also had pulverulent cataracts. Based on the pedigrees, an autosomal dominant mode of inheritance with a high degree of penetrance is suggested for pulverulent cataract.     

Phacoemulsification in an adult Savannah monitor lizard

An adult male Savannah monitor lizard (Varanus exanthematicus) was presented for bilateral lens opacities that had progressed rapidly over the previous 2 months. A diagnosis of bilateral mature cataracts was made and phacoemulsification cataract extraction was performed. Surgery restored vision and normal activity to the patient.     

An outbreak of cataract with lens rupture and nuclear extrusion in wolf-fish (Anarhicas spp.)

Eight spotted (Anarhicas minor Olafsen) and five common wolf-fish (Anarhicas Lupus L), developed cataracts shortly after an episode of increased water temperature and decreased salinity 5 years prior to examination. On clinical examination, the cataracts were mostly bilateral and complete, and a majority of the lenses were lobulated. Inflammatory reaction was, apart from one eye with severe inflammation, limited to iris atrophy. Of the 14 eyes collected for pathomorphological examination, eight had lens rupture with extrusion of the nucleus to the posterior chamber, two showed partly dislocated nuclei with posterior protrusion and two lenses were morgagnian. A multilayered squamous epithelium with abundant desmosomes had developed on the surface of seven of the extruded nuclei. The main cause of the cataracts was considered to be the rapid decrease in water salinity, causing osmotic changes within the eyes with secondary swelling of lens fibers and rupture of the lens capsules.     

Effects of topical administration of an aldose reductase inhibitor on cataract formation in dogs fed a diet high in galactose

OBJECTIVE: To determine effects of a topical formulation of an aldose reductase inhibitor (ARI) on the development of sugar cataracts in dogs fed a diet high in galactose. Animals-Ten 6-month old Beagles. PROCEDURES: Dogs were fed a diet containing 30% galactose, and after 16 weeks, 6 dogs were treated topically with a proprietary ARI formulation and 4 dogs were treated with a placebo. Cataract formation was monitored by means of slit-lamp biomicroscopy and fundus photography. Dogs were euthanized after 10 weeks of treatment, and lenses were evaluated for degree of opacity, myo-inositol and galactitol concentrations, and concentration of the ARI. RESULTS: All dogs developed bilateral cortical opacities dense enough to result in a decrease in the tapetal reflex after being fed the galactose-containing diet for 16 weeks. Administration of the ARI arrested further development of cataract formation. In contrast, cataracts in the vehicle-treated dogs progressed over the 10-week period to the mature stage. Evaluation of the isolated lenses after 26 weeks of galactose feeding indicated that lenses from treated dogs were significantly less optically dense than lenses from control dogs. Lenticular myo-inositol concentration was significantly higher in the treated than in the control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that topical application of a proprietary ARI formulation may arrest or reverse the development of sugar cataracts in dogs fed a diet high in galactose. This suggests that this ARI formulation may be beneficial in maintaining or improving functional vision in diabetic dogs with early lens opacities.     

Ocular findings in two colonies of gray mouse lemurs (Microcebus murinus)

OBJECTIVE: To determine the incidence and describe the characteristics of cataracts and other ocular lesions found in two colonies of gray mouse lemurs (Microcebus murinus). ANIMALS STUDIED: A total number of 218 mouse lemurs (age range: 4 months-11 years) were included in this study. All individuals were property of the Muséum National d'Histoire Naturelle (France), and were housed either in Paris (colony #1: 75 animals examined), or in Brunoy (colony #2: 143 animals). METHODS: Ocular examinations were performed on all animals before and after pupil dilation, and included slit-lamp biomicroscopy and indirect ophthalmoscopy. In both colonies, a limited number of individuals were re-examined between several months and 2 years following the initial eye examinations. The eyes of five mouse lemurs with incipient or immature cataracts that died during this period were collected, and processed for routine histopathologic examination. RESULTS: A high incidence of cataracts was observed in both colonies (48% in colony #1; 21% in colony #2). Cataracts were predominantly bilateral, started in the anterior and/or posterior subcapsular area, and appeared to be slowly progressive. The earliest age at which lens opacities were observed was 3.5 years, and more than 50% of mouse lemurs over 7 years of age were diagnosed with cataracts. Complete cataracts led to blindness and were occasionally associated with other ocular lesions. CONCLUSION: We report a high incidence of acquired, slowly progressive, bilateral cataracts in two colonies of mouse lemurs (Microcebus murinus). Further studies need to be conducted to determine the cause of this disease in this species.     

Diagnosis and treatment of lens diseases.

The lens represents a unique tissue in light of its embryologic development, retention of old cells and nuclear make-up, transparent nature, immune privileged status, and metabolic restrictions. Disorders of malformation and malposition occur, but cataract development is the most common and significant problem for owners and animals. Technologic and pharmacologic advances have allowed surgical removal of equine cataracts to become an acceptable alternative, capable of returning a visually impaired horse to a functional status. Uveal inflammation represents the greatest threat to successful surgical cataract removal. Veterinarians should consult with those versed in ophthalmology for assistance in diagnosis, prognosis, peroperative treatment, surgical intervention, and follow-up on lens disorders.     

Cataracts: Clinical presentations,diagnosis and management

Cataracts can be developmental or acquired lesions and cause minimal or significant visual impairment. The ability to identify cataracts and determine the likely effect on the visual potential of the horse is an important part of an equine ocular examination. Cataract surgery is the only treatment for those cataracts that cause significant visual impairment. Understanding appropriate patient selection and potential post operative complications is important so that owners can be appropriately advised of their options.     

Posterior lenticonus with congenital cataract in a Shih Tzu dog

A seven-month-old, male Shih Tzu dog weighing 3.7 kg had an immature cataract in its left eye. A biomicroscopic examination revealed numerous vacuolations in the posterior cortices with nucleus cataracts, covered by an intact anterior lens capsule. The changes observed by ocular sonographic examination (OSG) of the left eye were hyperechoic, and a funnel-cone shape was observed posteriorly with cortex hyperechogenicity in the lens. The left eye was diagnosed as having a posterior lenticonus with congenital cataract. Phacoemulsification was performed on the left eye as diagnostic treatment of the posterior lenticonus and cataract. Postoperative OSG on the left eye revealed a V-shaped linear echo that was indicative of a posterior capsule of the lens. Moreover, it was confirmed that hyperechoic cataract material inside the lens had disappeared.     

Familial cataracts and concurrent ocular anomalies in chow chows.

A closely inbred line of Chow Chows affected with congenital cataracts was studied. Sixteen dogs were examined including 1 adult male, 2 adult females, and 13 pups. Twelve of the pups were from 6 different litters, out of 6 different bitches, all sired by 1 adult male. The exact relationship of the thirteenth pup was undetermined. Clinical evaluation included slit-lamp biomicroscopy, biomicroscopic photography, and indirect ophthalmoscopy. Clinical appearance of the cataracts was variable, ranging from incipient nuclear or capsular lesions to advanced cortical opacity. The lens nucleus was most consistently affected, with variable involvement of the lens cortex. Concurrent ocular anomalies of some eyes included wandering nystagmus, entropion, microphthalmia, persistent pupillary membrane remnants, and multifocal retinal folds. A correlation was not apparent between the character or severity of the cataracts and the finding of the other anomalies. Histologic examination of 12 lenses revealed posterior displacement of the lens nucleus, retained lens epithelial cell nuclei in the nuclear and cortical lens, anterior capsular irregularity and duplication, anterior lens epithelial duplication, and posterior subcapsular migration of epithelium. The high incidence of cataract in this family of Chow Chows suggested an inherited defect, although the inheritance pattern was undetermined.     

Detection of Encephalitozoon cuniculi in the feline cataractous lens

Purpose Identification of Encephalitozoon cuniculi (E. cuniculi) as a possible causative agent for cataracts and uveitis in cats. Methods Within a 12‐month study period, cats that were presented with focal anterior cortical or mature cataract and secondary uveitis underwent a complete ophthalmic examination, complete blood count, serum biochemistry, serologic tests for E. cuniculi and tests for feline immunodeficiency virus (FIV), feline infectious peritonitis (FIP), feline leukemia virus (FeLV) and Toxoplasma gondii (T. gondii). PCR for DNA detection of E. cuniculi and T. gondii as well as cytologic examination of aqueous humor after paracentesis and phacoemulsified lens material were also performed. In addition histopathologic examination of the resected anterior lens capsule and attached lens epithelial cells was performed. Serologic testing for antibodies against E. cuniculi was also performed in 100 ophthalmologically healthy cats. Results Eleven (19 eyes) European shorthair cats with a median age of 3.5 years were included. Nine of 11 cats had bilateral cataracts, with 12/19 eyes having focal anterior cortical cataracts and 7/19 eyes having mature cataracts. In 14/19 eyes anterior uveitis was present. All cats had a positive antibody titer (1:80–1:10 000) for E. cuniculi. Encephalitozoon cuniculi DNA was detected by PCR and sequencing in 18/19 lenses and in 10/19 aqueous samples. Five tentative positive results were detected by cytologic examination. Spores were detected in 15/19 samples of lens material with histopathologic staining. Only 2/100 ophthalmologically healthy cats showed a positive antibody titer for E. cuniculi. Conclusion Encephalitozoon cuniculi is a cause of focal anterior cortical cataract and anterior uveitis in cats.     

Morphologic alterations in the anterior lens capsule of canine eyes with cataracts

OBJECTIVE: To examine the morphologic changes in the anterior lens capsule and lens epithelium of canine eyes with cataracts. SAMPLE POPULATION: Anterior lens capsules from the eyes of 25 dogs with cataracts and from an additional 10 canine globes with lenses subjectively assessed to be normal. PROCEDURE: Thickness of each anterior lens capsule was measured by use of a digital microscopic camera and imaging software. All 25 capsules from eyes with cataracts were submitted for light microscopy; 4 were also submitted for electron microscopy. RESULTS: Thickness of the anterior lens capsule increased with age for the normal lenses and the lenses with cataracts; the change with age was similar for both groups. Light microscopy revealed fibrous metaplasia of lens epithelial cells in 7 of 25 anterior lens capsules with focal thickenings of the posterior aspect of the capsule. Electron microscopy revealed deposition of collagen and basement membrane-like material by fibroblast-like cells. CONCLUSIONS: Results indicate that thickness of the anterior lens capsule in dogs increases with age and that this increase in thickness is not significantly different between normal lenses and lenses with cataracts. In addition, epithelial cells from lenses with cataracts may undergo metaplasia to form plaques composed of fibrous tissue and ectopic basement membrane produced by epithelial cells.     

Inheritance of cataracts and primary lens luxation in Jack Russell Terriers

OBJECTIVE: To characterize heritability and mode of inheritance of cataracts and primary lens luxation in Jack Russell Terriers. ANIMALS: 872 Jack Russell Terriers from which buccal epithelial cells were collected and phenotypes for cataracts and lens luxation were determined and an additional 1,898 Jack Russell Terriers without phenotypic information used to complete pedigree relationships and that were included in the analyses. PROCEDURES: Narrow-sense heritabilities and genetic correlation for cataracts and lens luxation were modeled by use of threshold analysis, whereas complex segregation analysis was used to characterize mode of inheritance. For the analyses, dogs < 6 years old, unless confirmed as having cataracts or lens luxation, were classified as an unknown phenotype. The possible involvement of an HSF4 mutation in cataracts was determined by DNA sequencing. RESULTS: Cataracts and primary lens luxation were highly heritable and genetically correlated, and neither was controlled by a single gene. Cataracts were not associated with an HSF4 mutation. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of the data indicated that concerted selection against both cataracts and primary lens luxation when choosing breeding animals can be used to improve ocular health in Jack Russell Terriers.     

Prevalence of Ocular Disorders in an Indian Population of Horses

The objective of this clinical study was to report the prevalence of ocular disorders in a large population of horses from the Indian army. Both eyes of 500 horses were examined using a direct ophthalmoscope and by a transillumination procedure. Intraocular pressures were measured in several study horses. Fluorescein dye, Schirmer tear test, and menace testing were performed when indicated. Corneal culture swabs were collected from horses affected with corneal ulcers found on ophthalmoscopic examination. A total of 100 horses were found to be affected with some form of ocular disorder. The eye problems recorded were congenital eye lid disorders (2%) and included a subcutaneous cyst in the lower eye lid and slit in upper eye lid; conjunctivitis (12%); chronic interstitial keratitis (30%); a parasite in the anterior chamber (1%), which was however not removed for genus and species identification; phthisis bulbi (1%); uveitis (24%); glaucoma (13%); cataracts (3%); unilateral retinal hemorrhage (1%); luxation of cataractous lens (3%); posterior synechia (2%); and corneal ulceration (8%). Pseudomonas spp was the most common bacteria identified in horses affected with corneal ulceration. Vision-threatening ocular disorders are high in Indian army horses; this is a cause of major concern for the rider and the horse and, therefore, it is important to include ocular examination in horses as part of a routine and complete physical examination.     

ACUTE DIFFUSE MYCOTIC PNEUMONIA IN A 7-MONTH-OLD COLT

A 7-month-old Quarter horse colt developed acute diarrhea, laminitis, bilateral uveitis, and severe respiratory distress after intramuscular injection with a bacterial vaccine. Thoracic radiographs revealed diffuse unstructured, nodular interstitial, and peribronchial opacities throughout the lung. Despite intensive supportive therapy, the colt became progressively hypoxemic and died. At postmortem examination, severe multifocal to coalescing hemorrhagic, necrotizing fibrinous pneumonia was found. Histologic study revealed numerous branched septate fungal hyphae diffusely distributed throughout the lung parenchyma. Fungal culture of lung tissue grew Aspergillus fumigatus. This report presents the radiographic, clinical, and pathologic features of acute mycotic pneumonia in horses.