Comparative evaluation of corneal and limbal epithelial thickness in brachycephalic dogs with and without corneal diseases using spectral domain optical coherence tomography.

OBJECTIVE: To evaluate alterations in epithelial thickness during corneal degeneration, corneal pigmentation, and additional features observed through spectral-domain optical coherence tomography (SD-OCT) in brachycephalic dogs. ANIMALS AND PROCEDURES: The study used 55 eyes from 49 brachycephalic dogs that underwent OCT-containing ophthalmic examinations. The examined eyes were classified into corneal degeneration, corneal pigmentation, and normal groups according to corneal lesions. For each eye, corneal epithelial thickness (CET) in the central cornea and maximum limbal epithelial thickness (maxLET) in 4 quadrants of limbus (superior, inferior, nasal, and temporal) were measured from OCT images. Additional abnormal findings on OCT images, including irregular epithelium, subepithelial hyperreflectivity, and conjunctivochalasis, were also recorded. RESULTS: The corneal degeneration group had significantly thinner nasal and temporal maxLETs than that of the normal group (p < .001). In the central corneal OCT image of the corneal degeneration group, an irregular epithelium was observed in 70.6% and subepithelial hyperreflectivity in 82.4%, both of which were significantly higher than the normal group (p < .001). In a comparative analysis, the nasal, temporal, and inferior maxLETs were significantly thinner in the corneal pigmentation group than those in the normal group (p < .001, p < .001, and p = .01, respectively). CONCLUSIONS: Morphological changes in the limbal epithelium were observed in dogs with corneal degeneration and corneal pigmentation. LET reduction could be associated with their pathogenesis and would be valuable as an additional parameter for corneal diseases.

Topical 1% cyclosporine eyedrops for the treatment of crystalline corneal dystrophy in dogs.

Background: Crystalline corneal dystrophy (CCD) is the most common type of corneal lipidic deposition in dogs. CCD is a primary metabolic disorder of the corneal fibroblast featuring an accumulation of extracellular and intracellular lipid deposits. Corneal lipid deposits create a corneal opacity and modify the interfibrillar collagen distance, inducing light scattering. Corneal vascularization is not usually associated with the disease, but, in case of chronicity, cell death may produce inflammation, and new corneal vessels are developed. To the best of the authors' knowledge, this is the first report of a medical approach for CCD treatment in veterinary medicine. Aim: To evaluate the efficacy of topical 1% cyclosporine eyedrops (1% CsA) for the treatment of CCD in dogs. Methods: Medical records of dogs with CCD were retrospectively reviewed (2009-2020). Corneal opacification description (COD) [size (mm), depth, and opacification degree (0-3)] was evaluated at 0, 3, 6, 9, 12, and 15 months postinitial diagnosis. Dogs were classified into three groups: the control group (G0), the group receiving topical 1% CsA once per day (G1), and the group receiving topical 1% CsA twice daily (G2). Results: Ninety-two client-owned dogs (163 eyes) of different breeds, ages, and gender fulfilled the inclusion criteria. When compared to G0, where the eyes significantly increased COD (p < 0.001), G1 and G2 significantly decreased COD (p < 0.001). In fact, the probability of reducing COD was about three times higher in G2 than in G1, being nearly the same for the right [odds ratio (OR) = 2.94; 95% confidence interval (95% CI) = 0.55-15.78] and left eye (OR = 2.92; 95% CI = 0.49-17.26). In addition, for each additional month of treatment in G2, the probability of reducing COD increased significantly (OR = 1.12; 95%CI = 1.00-1.26 for the right eye and OR = 1.16; 95%CI = 1.02-1.32 for the left eye). Conclusion: Long-term treatment with topical 1% CsA eyedrops significantly improved CCD in dogs, being the probability of reducing COD higher when applying the treatment twice daily.

Disseminated idiopathic lipid keratopathy in a normolipemic cat.

OBJECTIVE: To report a case of idiopathic lipid keratopathy in a normolipemic cat. ANIMAL STUDIED: A 10-year-old neutered female European domestic cat. RESULTS: A cat was evaluated for bilateral white corneal deposits. Slit-lamp examination revealed multiple, well-defined, round, stromal, cream-colored deposits of different sizes associated with generalized superficial corneal vascularization. Blood lipids were normal, and no history of travel to tropical locations or ocular trauma was present. Topical betamethasone/gentamicin 0.1% suspension q 12 hours did not result in any improvement of clinical appearance after one week. Tomography following the initial therapy revealed dense, hyperreflective deposits with posterior shadowing in the anterior and mid stroma of both corneas. A four-week course of itraconazole 0.01% ophthalmic cream was prescribed q 12 hours with no improvement. Four months after the initial examination, a diagnostic superficial keratectomy and amniotic membrane implantation were performed. Histopathological analysis showed membrane bound vacuoles with infiltration of foamy macrophages suggesting a diagnosis of primary lipidosis. The post-surgical period was unremarkable, and ten days later, the patient was re-examined. Opacification from a corneal leukoma was observed in the excision site with mild fibrotic tissue. Two months post-keratectomy, no further changes were detected in the cornea, and the patient was managed only with topical lubricant. CONCLUSIONS: To our knowledge, this is the first report of idiopathic corneal lipidosis in a cat and may be considered as a differential diagnosis of corneal disease in felines.

Multimodal ocular imaging of known and novel corneal stromal disorders in dogs.

BACKGROUND: Imaging features obtained with Fourier-domain optical coherence tomography (FD-OCT) and in vivo confocal microscopy (IVCM) for corneal stromal disorders have been sparsely reported in dogs. This case report is a compilation of imaging features for three cases of different stromal disorders of the canine cornea which have not yet been reported elsewhere. CASE PRESENTATION: Lipid deposition in case 1 appeared as needle-shaped hyperreflective lines along the collagen lamellae, which correlated histologically with lipid clefts. In case 2, glycosaminoglycan accumulation by mucopolysaccharidosis type 1 caused diffuse stromal hyperreflectivity and depletion of keratocytes on IVCM and was associated with secondary corneal degeneration presumed to be calcium deposition. In case 3, posterior corneal stromal opacities in the absence of ocular inflammation were identified. Hyperreflective particles were scattered in the middle and posterior corneal stroma on FD-OCT. With IVCM, hyperreflective deposits were identified within keratocytes and the number of enlarged keratocytes containing hyperreflective deposits increased towards the posterior stroma. The bilateral, non-inflammatory nature and unique appearance with IVCM is most consistent with a posterior stromal dystrophy reminiscent of pre-Descemet corneal dystrophy described in humans. CONCLUSIONS: In vivo multimodal corneal imaging facilitated instantaneous microstructural analysis and may be valuable in the differential diagnosis of corneal stromal disorders in veterinary clinical practice. The non-specific nature of imaging findings occurs in some conditions such as mucopolysaccharidosis, thus in vivo corneal imaging should be complemented with other gold standard methods of definitive diagnosis.

Topical Ethylenediaminetetraacetic acid (EDTA) administration following corneal diamond burr keratotomy for calcareous corneal degeneration in canines.

OBJECTIVE: To evaluate the outcomes of canine patients diagnosed with corneal ulceration associated with presumed calcareous corneal degeneration (CCD) that were treated with diamond burr keratotomy (DBK) and ongoing postoperative topical 3% or 4% Ethylenediaminetetraacetic acid (EDTA). PROCEDURES: Retrospective assessment of CCD cases treated with ongoing topical EDTA following DBK between 2011 and 2020 at Veterinary Ophthalmic Referrals. Descriptive statistics of the study population were assessed, and a survival analysis was performed using R statistical software. RESULTS: A total of 51 eyes from 41 dogs were assessed, with small terrier breeds overrepresented (27/41, 65.9%). Median age of dogs at the time of diagnosis was 14.3 years (range 8-17.2 years). Following DBK, the median time to commencement of topical EDTA was 11 days (range 0-28 days). Cases were followed for a median duration of 216 days (range 42-1379 days). Corneal ulceration recurred in 7/51 (13.7%) eyes at a median duration of 80 days (range 63-156 days). The probability of recurrence of corneal ulceration associated with CCD at 12 months was 15.6% (95% CI: 4.1-25.7%). A second DBK procedure followed by ongoing topical EDTA was performed in 4/7 (57.1%) of the recurred eyes. These retreated eyes had no further recurrence recorded and a median follow-up time of 401 days (range 120-858 days). CONCLUSION: Ongoing topical EDTA following DBK is an effective adjunct treatment method for CCD with reduced rates of recurrence of CCD-associated corneal ulceration when compared to published rates of recurrence when treated with DBK alone.

Applications of in vivo confocal microscopy in the management of infectious keratitis in veterinary ophthalmology.

In vivo confocal microscopy (IVCM) is a relatively new ocular imaging technique that permits morphological and quantitative assessment of the living cornea on the cellular level. The applications for IVCM in clinical ophthalmology are numerous and diverse. There are several advantages inherent to IVCM over standard diagnostic techniques currently used to confirm a diagnosis of infectious keratitis in veterinary ophthalmology. With IVCM, images can be viewed in real-time providing immediate diagnostic information. Traumatic corneal sampling techniques are avoided, and the procedure can be repeated as frequently as is clinically indicated without risk of corneal tissue damage. Both superficial and deep corneal lesions can be evaluated by IVCM in an atraumatic fashion. Microorganism viability is not required for their detection and specialized diagnostic laboratory assay procedures are not necessary. Many larger infectious agents can be directly identified within corneal lesions by IVCM, including fungi and parasites such as Acanthamoeba spp. In other situations, such as bacterial infectious crystalline keratopathy, the biological systems associated with the microorganism can be detected within the cornea. The current resolution of IVCM is inadequate to directly visualize some corneal infectious agents, such as herpesviruses, but host responses and virus-infected epithelial cells can be identified. This review summarizes the current knowledge and applications of IVCM in the management of infectious keratitis in veterinary ophthalmology, including its use in animals with bacterial, fungal, parasitic, and viral keratitis.

A Retrospective Study of Corneal Endothelial Dystrophy in Dogs (1991-2014).

PURPOSE: To retrospectively evaluate the clinical data, diagnostic tests, treatments, and outcomes for dogs with corneal endothelial dystrophy (CED) and determine risk factors for CED when compared with a canine reference population. METHODS: Medical records of 99 dogs (1991-2014) diagnosed with CED at the University of California Davis Veterinary Medical Teaching Hospital were reviewed and compared with 458,680 dogs comprising the general hospital population during the study period. Retrieved data included signalment, examination findings, diagnoses, treatments, and outcomes associated with CED. The exact Pearson χ2 test or exact Kruskal-Wallis test was used to compare parameters between the groups. Progression of corneal edema was assessed using 3 independent Kaplan-Meier curves, identifying clinically significant changes in corneal opacity. RESULTS: Boston terriers, German wirehaired pointers, and Dachshunds were overrepresented in the CED-affected group, whereas Labradors were underrepresented. Dogs older than 11 years were overrepresented in the CED-affected group, whereas intact dogs were underrepresented. Surgical intervention was performed (n = 11) based on the severity of disease and secondary complications from CED. Median time to progression of corneal edema was 1) 368 days when an at-risk eye initially without edema developed edema at a subsequent visit, 2) 701 days when there was progression from mild to marked corneal edema, and 3) 340 days when there was progression from focal to diffuse corneal edema. CONCLUSIONS: Many CED-affected dogs progress over months to years without surgical intervention, making dogs with CED a useful model for studying genetic predispositions and development of novel therapeutics for Fuchs endothelial corneal dystrophy.

Comparison of automated vs manual analysis of corneal endothelial cell density and morphology in normal and corneal endothelial dystrophy-affected dogs.

OBJECTIVE: To determine the efficacy of automated imaging software of the Nidek ConfoScan 4 confocal biomicroscope at analyzing canine corneal endothelial cell density and morphology in health and disease, by comparing to a manual analysis method. ANIMAL STUDIED: Nineteen eyes of 10 dogs were evaluated and include three Beagles, three Jack Russell Terriers, and four miscellaneous breeds. Twelve clinically normal and seven eyes affected with corneal endothelial dystrophy (CED) were scanned and analyzed. PROCEDURES: Endothelial cell density (ECD), mean and standard deviation (SD) of cell area, percent polymegathism, mean and SD of the number of cell sides, and percent pleomorphism were calculated using automated and manual methods for each scan. RESULTS: The automated analysis showed significantly greater ECD in comparison with the manual frame method due to misidentification of cell domains in CED-affected dogs. No significant differences in ECD were observed between normal and CED-affected dogs in automated analysis, while CED-affected dogs showed significantly lower ECD in manual frame method and planimetry. Using both automated and manual methods, CED-affected dogs showed greater variability of cell area or the number of cell sides than normal dogs. CONCLUSION: The automated imaging software is unable to accurately identify cell borders in CED-affected dogs resulting in inaccurate estimates of ECD. Thus, manual analysis is recommended for use in clinical trials assessing adverse events associated with novel medical treatments and/or surgical procedures.

Endothelial keratoplasty for corneal endothelial dystrophy in a dog.

OBJECTIVE: To assess the efficacy of an endothelial keratoplasty procedure at defined intervals to 1 year postoperatively for the treatment of corneal endothelial dystrophy (CED) in a canine patient. PROCEDURE: A dog diagnosed with CED with progressive corneal edema underwent an endothelial keratoplasty. The patient was examined pre- and postoperatively with slit lamp biomicroscopy and ultrasonic pachymetry. RESULTS: Mean central corneal thickness (CCT) measured with pachymetry was >1400 µm preoperatively and decreased postoperatively to 725 µm. The transplanted donor tissue became transparent 2 weeks postoperatively and incorporated with the recipient cornea. The graft remained transparent throughout the duration of the postoperative period evaluated in this study (2 weeks postoperatively to 1 year). The canine patient was comfortable pre- and postoperatively. CONCLUSIONS: Endothelial keratoplasty is a potential therapeutic option for canine cases with progressive corneal thickening due to CED. As this is a single case study, further investigation into the use of endothelial keratoplasty to treat CED is warranted. Moreover, canine patients with CED might serve as a surgical model for human patients with Fuchs' Endothelial Corneal Dystrophy.

Early postoperative results of Descemet's stripping endothelial keratoplasty in six dogs with corneal endothelial dystrophy.

OBJECTIVE: To describe and assess the clinical outcome and intraoperative and postoperative complications of Descemet's stripping endothelial keratoplasty (DSEK) in the treatment of canine corneal endothelial dystrophy. ANIMALS STUDIED: Six dogs (six eyes) diagnosed with progressive corneal edema resulting from abnormal dystrophic endothelial cells underwent Descemet's stripping endothelial keratoplasty. PROCEDURES: Six patients underwent Descemet's stripping endothelial keratoplasty (DSEK). The patients were examined preoperatively and postoperatively at 24 hours, 7 days, 1, 2, and 3 months after surgery. Corneal edema and ultrasonic pachymetry were evaluated preoperatively and postoperatively. The positions of DSEK grafts were evaluated 3 months after surgery using optical coherence tomography. Intraoperative and postoperative complications were noted. RESULTS: The degree of corneal edema and corneal thickness improved postoperatively in all the patients (n = 6). Fibrin was encountered intraoperatively in one out of the six eyes (1/6) and postoperatively in two out of the six eyes (2/6). One out of the six DSEK grafts was partially scrolled (1/6). Secondary ocular hypertension was observed in one out of the six eyes (1/6). Corneal vascularization was encountered in four out of six patients (4/6). CONCLUSIONS: Descemet's stripping endothelial keratoplasty is an effective surgical treatment option for corneal endothelial dystrophy in dogs. Corneal edema resolved and corneal thickness reduced significantly. The early postoperative results are encouraging. Further investigation is warranted to document any long-term complications and to study the longevity of the transplanted grafts.

Phenotype of macular corneal dystrophy in Labrador Retrievers: A multicenter study.

OBJECTIVE: To describe the phenotype of canine macular corneal dystrophy (MCD) including the clinical presentation, multimodal ocular imaging, histopathology, and ultrastructural analysis in ten Labrador Retrievers. PROCEDURE: Multicentered data collection. RESULTS: Labrador Retrievers affected by MCD were presented between the age of 4.5 and 6 years of age with a history of cloudy eyes and/or visual impairment. Findings on ophthalmic examination included a diffuse haze of the corneal stroma and multiple, well-demarcated, off-white to yellow-brown, punctate corneal opacities heterogeneous in size. Corneal vascularization developed in most dogs as the disease progressed. Disease progression was associated with increased density of the corneal haze as well as increased number and size of the focal opacities and dogs developed significant visual impairment. Spectral domain-optical coherence tomography revealed multifocal hyper-reflective regions within the stroma. In vivo confocal microscopy revealed marked alterations in reflectivity throughout the entire stroma. Normal keratocytes could not be identified in affected areas. Histopathology showed stromal collagen fibers separated by acidophilic granular material on hematoxylin and eosin stain. The material stained with periodic acid-Schiff and colloidal iron stain but not with Masson trichrome stain, confirming the accumulation of glycosaminoglycans. On electron microscopic ultrastructural examination, keratocytes presented with vacuolated rough endoplasmic reticulum and multiple electron dense cytoplasmic inclusions. In areas keratocytes appeared ruptured, with cell organelles and proteinaceous material grouped together between collagen fibers. CONCLUSION: MCD in Labrador Retrievers has similarities with the human counterpart of the condition and is an important differential diagnosis in dogs with corneal disease.

Corneal collagen cross-linking following superficial keratectomy as treatment for corneal endothelial cell dystrophy in dogs: Preliminary clinical study.

OBJECTIVE: To describe the outcome of corneal collagen cross-linking (CXL) combined with superficial keratectomy (SK) as treatment for corneal edema due to corneal endothelial dystrophy (CED) in dogs. ANIMALS STUDIED: Four eyes of four dogs (3 Shih Tzus and 1 English Cocker Spaniel) with corneal edema due to CED were treated with SK and CXL. Two were males, and two were females. PROCEDURE: Depending on corneal thickness, 500-700 µm of edematous cornea was removed by SK. Next, CXL was performed by irradiating the cornea with UVA (365 nm) at 3 mW/cm² irradiance for 30 min after soaking with 0.1% riboflavin in 20% dextran every three minutes for 30 minutes. One drop of riboflavin was instilled every three minutes during irradiation. Slit lamp biomicroscopy and optical coherence tomography were used to examine the cornea during the follow-up period. RESULTS: The corneas had focal to diffuse edema, and the average corneal thickness was 1553 (1282-1900) µm. All corneas showed a significantly reduced corneal thickness and regained marked transparency immediately after treatment; however, the opacity increased as the corneal thickness increased during the follow-up period. Corneal vascularization (n = 4) disappeared within a month. Corneal pigmentation (n = 1) and bullae (n = 1) were observed. All cases showed marked reduction in corneal thickness; however, transparency was improved in only one case. CONCLUSION: Collagen cross-linking with SK has the potential to reduce the corneal thickness in CED cases; however, a lasting clinically significant improvement of corneal transparency seems unlikely. As the added benefit of CXL to the SK procedure is unclear based on the results of this study, combined treatment of CXL and SK for the treatment of corneal edema caused by CED is currently not recommended in dogs.

A Carbohydrate Sulfotransferase-6 (CHST6) gene mutation is associated with Macular Corneal Dystrophy in Labrador Retrievers.

PURPOSE: To locate and identify variants associated with macular corneal dystrophy (MCD) in Labrador Retriever (LR) dogs, in the candidate gene carbohydrate sulfotransferase-6 (CHST6). METHODS: The single coding exon of canine CHST6 was sequenced in one affected LR with MCD and one control LR clinically clear of ocular disease. A further 71 control LR with unknown clinical status were sequenced for the putative causal variant in CHST6. A TaqMan SNP genotyping assay was developed and used to screen an additional 84 dogs (five affected LR and 79 clinically clear LR). Finally, the variant was screened in a third cohort of 89 unrelated LR with unknown clinical status to estimate its allele frequency in the population of LR in the United Kingdom. RESULTS: A single nucleotide polymorphism (SNP) was identified within the coding exon of CHST6, resulting in a missense mutation (c.814C>A, p.R272S). All six LR affected with MCD were homozygous for the mutant allele, while 140/151 control LR were homozygous for the wild-type allele and 11/151 were heterozygous for the mutation, indicating an association with MCD (P < 10-5 ). The mutant allele was present in the unrelated LR cohort at a frequency of 0.017, suggesting carrier and affection rates of 3.3% and 0.028%, respectively. CONCLUSIONS: A missense mutation in the CHST6 gene is strongly associated with autosomal recessive MCD in the LR.

Corneal dystrophy in Friesian horses may represent a variant of pellucid marginal degeneration.

OBJECTIVE: To describe the clinical presentation, treatment, and outcome of a corneal dystrophy in Friesian horses and to analyze affected horses' pedigrees to investigate its heritability. ANIMALS: Nine Friesians with bilateral disease were identified. PROCEDURE: Retrospective medical record review was used to identify Friesian horses exhibiting bilateral symmetric corneal lesions. Variables identified from medical records included patient sex and age at diagnosis; location, depth and size of corneal lesions; medical and surgical therapy instituted; and visual outcome. A four-generation pedigree for each included horse was used to construct a combined pedigree. RESULTS: The nine included horses had an average age at diagnosis of the first eye of 10.7 years, with males (8/9) significantly more frequently affected than females (1/9), P = 0.012. Lesions were inferior and averaged 5 mm in diameter. Depth ranged from superficial facets to perforations, which developed in nine of 18 eyes. Eight of nine perforations were surgically repaired, with seven of eight repaired eyes visual at last follow-up. All nine eyes that had not perforated remained visual. All affected horses shared a common ancestor within six generations. CONCLUSIONS: This form of corneal dystrophy in Friesian horses, characterized by bilateral symmetric stromal loss, appears to be progressive but responds well to surgical repair, occurs more frequently in males, may have a genetic component in Friesian horses, and may be a variant of pellucid marginal degeneration.

Use of thermokeratoplasty for treatment of ulcerative keratitis and bullous keratopathy secondary to corneal endothelial disease in dogs: 13 cases (1994-2001).

OBJECTIVE: To evaluate the outcome of thermokeratoplasty for treatment of ulcerative keratitis and bullous keratopathy secondary to corneal endothelial disease in dogs. DESIGN: Retrospective study. ANIMALS: 13 dogs. PROCEDURES: Medical records from 1994 to 2001 for dogs evaluated because of ulcerative keratitis and bullous keratopathy and treated with thermokeratoplasty were reviewed. RESULTS: There were 7 spayed females, 5 castrated males, and 1 sexually intact male, ranging from 6 to 16 years of age. Ten dogs had endothelial degeneration, and 3 dogs had breed-related endothelial dystrophy. All dogs had bullous keratopathy, characterized by microbullae formation that was detected via biomicroscopy. Recurrent or nonhealing corneal ulcers were detected unilaterally in 5 dogs and bilaterally in 8 dogs. Mean +/- SD duration from thermokeratoplasty until ulcerations were healed for all dogs was 2.2 +/- 1.1 weeks. All dogs that underwent thermokeratoplasty for nonhealing corneal ulceration secondary to endothelial disease and corneal edema had epithelial wound healing and resolution of corneal ulceration. Mean duration of treatment (ie, topical treatment required until resolution of ulceration) was significantly less after thermokeratoplasty than duration of treatment (with multiple treatments) prior to referral. CONCLUSIONS AND CLINICAL RELEVANCE: It may be necessary to perform thermokeratoplasty of the entire cornea to prevent recurrence of ulcerations in areas that have not been treated with thermokeratoplasty.

Corneal dystrophy in the dog and cat.

Two types of epithelial dystrophy have been described in dogs, one each in the Boxer and Shetland Sheepdog breeds, both of which can be associated with corneal erosions. Medical therapy is recommended when erosions or tear film abnormalities are present. Stromal dystrophies documented in dogs appear to be a primary lipid deposition in various layers of the stroma, depending on the breed. Stromal dystrophies seldom lead to loss of vision, but vision loss has been observed in middle aged Airedale Terriers and aged Siberian Huskies. Treatment is usually unnecessary. The dog demonstrates two types of endothelial dystrophy, one of which (posterior polymorphous dystrophy in the American Cocker Spaniel) does not lead to corneal edema. Endothelial dystrophy observed in the Boston Terrier, Chihuahua, and other breeds is associated with progressive corneal edema, which can lead to bullous keratopathy and corneal erosions. Stromal and endothelial dystrophies, both of which are associated with rapid progression of corneal edema, occur rarely in the cat. Treatment of dystrophies with progressive corneal edema is symptomatic and palliative.

Corneal dystrophy in Fischer 344 rats.

A spontaneous degenerative lesion of the cornea resembling calcific band keratopathy in man has been observed in 10-15% of the F-344 rats (aged 35-300 days) purchased from a private vendor's closed breeding colony. The lesion appears clinically as punctuate to linear superficial corneal opacities located in the interpalpebral fissure of one or both eyes. Occasional roughening, bleb formation, or pitting of the corneal surface resembling superficial ulcers may be observed. The lesion occurs in both sexes. It is rarely associated with inflammation or irritation. Histologically, it consists of mineral deposits along the epithelial basement membrane and Bowman's space, some of which are large enough to disrupt or destroy portions of the basilar epithelium. Energy dispersive X-ray analysis of the deposits proved them to be composed of calcium and phosphorus. Electron microscopic examination revealed a variety of extracellular laminated and crystalline arrays similar to those seen in humans with band keratopathy. The etiology of the lesion is as yet undetermined. A genetic-associated susceptibility due to hypercalcemia may be involved.