Spontaneous chronic corneal epithelial defects in dogs: a review

Spontaneous chronic corneal epithelial defects (SCCEDs) in dogs are typically found in middle-aged dogs of all breeds. These epithelial defects may be present for weeks to months, particularly if left untreated or if treated inappropriately. Typical histopathological findings include loss of the corneal epithelial basement membrane and formation of a superficial, acellular, hyalinized zone in the stroma. Together, these histological abnormalities lead to delayed wound healing and poor epithelial adhesion. Epithelial debridement, anterior stromal puncture, grid keratotomy, and superficial keratectomy are the most common treatment options applied to the defects. Procedures that address the stromal changes present generally have a higher success rate than epithelial debridement alone.     

Thermal cautery of the cornea for treatment of spontaneous chronic corneal epithelial defects in dogs and horses

A thermal cautery technique was used to treat spontaneous chronic corneal epithelial defects (SCCEDs) in 9 eyes of 8 dogs and 2 eyes of 2 horses. Animals were sedated, and a topical anesthetic was applied. A handheld thermal cautery unit was then used to make multiple, small (< or = 1 mm in diameter), superficial burns throughout the affected area. The cautery unit was applied just until the slightest degree of contraction of the collagen fibrils was observed. After the stromal bed of the defect was treated, a rim of epithelium that extended approximately 1 mm around the denuded stroma was also subjected to thermal cautery. Following surgery, a contact lens was placed in dogs but not in horses, and the eye was treated with broad-spectrum antimicrobial ophthalmic solutions. Defects in all 11 eyes healed with minimal scarring; mean time to healing in dogs was 2.1 weeks (range, 2 to 3 weeks). The defect healed in 1 week in 1 horse and in 2 weeks in the other. Many therapeutic options are available for the treatment of SCCEDs. Procedures such as epithelial debridement and anterior stromal puncture have been shown to have a high rate of success. In cases for which these less invasive procedures fail, our results suggest that thermal cautery may be a reasonable alternative to previously described treatments for SCCEDs in dogs and horses prior to more invasive procedures such as superficial keratectomy.     

Basic fibroblast growth factor stimulates epithelial cell growth and epithelial wound healing in canine corneas

Objective  To evaluate the effect of basic fibroblast growth factor (bFGF) on the proliferation of canine corneal epithelial cells and epithelial wound healing.
Animal studied  Canine corneal epithelial cells from the corneas of euthanized dogs and corneal epithelial wounds on one eye from each of 24 dogs.
Procedures  The proliferation of corneal epithelial cells in vitro was measured using the methylthiazolyl-tetrazolium (MTT) assay. A corneal wound on one eye of each dog was made with a corneal trephine (6 mm diameter). Four concentrations of bFGF, 0, 100, 500, and 1000 ng/mL, were applied to the affected eyes of dogs, t.i.d. Fluorescein staining was used to assess closure of the corneal epithelial wound.
Results  The addition of bFGF resulted in a significant increase in epithelial proliferation at 24 h after culture, except 1 ng/mL bFGF. Cells with all bFGF treatments proliferated significantly at 48 and 96 h compared to those in the non-bFGF group. bFGF at a concentration of 10 ng/mL promoted cell proliferation maximally. The wound healing rate in the bFGF-treated groups was greater than that in the control. All corneal wounds in bFGF-treated corneas closed by day 7, whereas two of six corneal wounds in the control showed poor healing. None of the eyes developed corneal clouding or neovascularization during the experiment.
Conclusions  Basic fibroblast growth factor accelerated the proliferation of canine epithelial cells and effectively promoted corneal epithelial wound healing.     

Effect of topical administration of epidermal growth factor on healing of corneal epithelial defects in horses

OBJECTIVE-To characterize healing of corneal epithelial defects in horses and to evaluate the ability of epidermal growth factor (EGF) to modulate rate of corneal epithelial healing in horses. SAMPLE POPULATION: 20 eyes in 12 adult horses. PROCEDURE: Corneal epithelial wounds were created by mechanically debriding the limbus. Corneal healing was recorded for 3 treatment groups: 50 microg of EGF/ml (n = 5 eyes), 5 microg of EGF/ml (7), and PBS solution (8). Corneal healing was recorded once daily after instillation of fluorescein stain by use of photography and calculating the area of the wound, using imaging software. RESULTS: After corneal debridement, re-epithelialization was rapid and progressed in a linear fashion for the first 5 to 7 days after surgery in all groups. After that period, rates of healing decreased. A profound increase in the degree of inflammation, neovascularization, melanosis, and scarring was observed in eyes treated with the high dose of EGF (50 microg/ml), but there was not a statistical difference in mean healing time or in mean decrease in radius during the linear phase between the control and either EGF treatment groups. However, for all 8 horses in which both eyes were debrided, the first eye healed significantly faster than the second eye, regardless of treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Beneficial effects of topical administration of a high dose of EGF for acceleration of healing of corneal defects in eyes of horses are outweighed by the intensity of the associated inflammatory response.     

Efficacy of two chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects and ulcerative keratitis associated with bullous keratopathy in dogs

OBJECTIVE: To determine the efficacy of two antimicrobial-chondroitin sulfate ophthalmic solutions in the therapy of spontaneous chronic corneal epithelial defects (SCCED) and ulcerative keratitis associated with bullous keratopathy in dogs. ANIMALS STUDIED: Eighty dogs with SCCED and 14 dogs with ulcerative keratitis associated with bullous keratopathy. PROCEDURE: Following manual debridement of nonadherent epithelium, dogs were treated topically with a chondroitin sulfate ophthalmic solution containing either tobramycin or ciprofloxacin. Patients were re-evaluated at 2-week intervals for 4 weeks. RESULTS: After 2 weeks of treatment, 53.6% of eyes with SCCED and 17.6% of eyes with ulcerative keratitis associated with bullous keratopathy had healed. After 4 weeks of treatment, 81.0% of eyes with SCCED and 23.5% of eyes with ulcerative keratitis associated with bullous keratopathy had healed. There were no statistically significant differences in healing percentages between the tobramycin-chondroitin sulfate solution treatment groups and the ciprofloxacin-chondroitin sulfate solution treatment groups. Two dogs with SCCED, one treated with the tobramycin-chondroitin sulfate solution and the other treated with the ciprofloxacin-chondroitin sulfate solution, developed sterile corneal stromal abscesses during the study. CONCLUSIONS: Topical therapy with an antimicrobial-chondroitin sulfate ophthalmic solution combined with manual debridement of nonadherent epithelium compares favorably with other published medical and surgical therapies for SCCED; however, these compounds are only equivocally more effective than therapy with manual debridement alone. These solutions appear to be ineffective in the treatment of ulcerative keratitis associated with bullous keratopathy. The significance of the two cases of corneal stromal abscessation is unknown at this time and warrants further investigation.     

Management of spontaneous chronic corneal epithelial defects (SCCEDs) in dogs with diamond burr debridement and placement of a bandage contact lens

Objective To describe the outcome of canine spontaneous chronic corneal epithelial defects (SCCED) treated with diamond burr debridement (DBD) and bandage contact lens placement (BCL). Animal studied Forty eyes of 36 dogs presenting to a single private practice. Procedures A retrospective review of medical records was performed. Cases were eligible for inclusion if they were newly diagnosed with SCCED by a veterinary ophthalmologist and treated with DBD/BCL. All patients received a complete ocular examination followed by DBD using a battery‐powered, handheld motorized burr (Algerbrush^®, Alger Equipment Company, Lago Vista, TX, USA). A BCL was placed post‐debridement in all patients. Data were analyzed for sex, age, breed, duration of clinical signs prior to DBD; number of debridements required before healing was achieved; contact lens retention, complications attributed to DBD, and additional surgical interventions were required to achieve healing. Results The median time to first recheck examination was 7 days (IQR 7–9 days) with 28/40 (70%) of cases healed at this examination. The mean time to second recheck examination was 15.5 ± 5.5 days with 37/40 (92.5%) healed by this examination. The median time to final recheck examination was 19 days (IQR 18–35.5 days) with a range of 18–52 days. All cases resolved by the third and final recheck examination. A second DBD/BCL was performed in 5/40 (12.5%) of cases. The BCL retention rate was 95% over all examination time points. No case required a keratectomy or other surgical intervention to achieve healing. The only complication observed was one case of suspected bacterial keratitis post‐DBD/BCL. Conclusions Results suggest that DBD/BCL is safe and effective for treatment of canine SCCED.     

Topical treatment of non-healing corneal epithelial ulcers in dogs with aminocaproic acid

The potential efficacy of topical epsilon-aminocaproic acid, an antiplasmin agent, in the treatment of persistent corneal epithelial defects was evaluated in a study of the medical records of 44 dogs, in which 51 eyes had been diagnosed with a corneal epithelial defect lasting more than 10 days, with no apparent underlying cause. At an initial examination all the affected eyes had had non-adherent epithelium removed. Thirty-four of the eyes in 28 dogs examined between January 2000 and March 2003 were also treated by the topical application of a solution of 35.7 mg/ml ophthalmic aminocaproic acid three times a day; the other 17 eyes in 16 dogs treated between October 1997 and March 1999 had received only topical treatment with gentamicin in addition to the debridement. Both groups were assessed clinically at weekly intervals for a maximum of three weeks. The two groups had approximately the same breed distribution, and there were no statistically significant differences between them in terms of their age, sex, affected side or duration of the corneal erosions. After three weeks, 32 of the 34 eyes treated with aminocaproic acid (94.1 per cent) had been cured, compared with seven of the 17 eyes treated with gentamicin (41.2 per cent) (P=0.0001). No adverse drug reactions were reported.     

A novel herpesvirus associated with chronic superficial keratitis and proliferative conjunctivitis in a great horned owl (Bubo virginianus)

An adult great‐horned owl (Bubo virginianus; GHOW) presented with a history of recurrent corneal ulceration of the right eye (OD). Findings included ulcerative superficial keratitis, proliferative conjunctivitis, and iris pigmentary changes. The ulcer was initially nonresponsive to medical therapy, but showed rapid and appropriate healing following diamond burr debridement. Proliferative conjunctivitis markedly improved following topical antiviral therapy with cidofovir 1%, interferon alpha 2B ophthalmic solutions, and oral l ‐lysine. Histopathologic evaluation of a conjunctival biopsy revealed epithelial features suspicious for viral cytopathic changes and intranuclear structures suspicious for viral inclusions, suggestive of a possible viral‐induced papillomatous conjunctivitis. A novel alphaherpesvirus, referred to as Strigid Herpesvirus 1 (StrHV1), was identified using PCR and gene sequencing. This case represents a new clinical manifestation of a previously unreported herpesvirus in the GHOW. Identification of the herpes virus was critical to administration of appropriate therapy and resolution of the conjunctivitis, and corneal epithelial debridement promoted resolution of the chronic corneal epithelial defect.     

Superficial, nonhealing corneal ulcers in horses: 23 cases (1989-2003)

Objective To characterize superficial, nonhealing corneal ulcers in the horse and to assess the affect of age, breed, sex, inciting cause of the ulcer, and treatment on healing time of these ulcers. Design Retrospective study. Animals Twenty‐three horses with superficial, nonhealing corneal ulcerations. Procedure Medical records from 1989 to 2003 of horses diagnosed with superficial, nonhealing corneal ulcers were reviewed. Signalment, duration of clinical signs, ophthalmic abnormalities, treatment and response to treatment were recorded. Horses were treated, in addition to medical therapy, using debridement, debridement and grid keratotomy, superficial keratectomy, and superficial keratectomy with conjunctival graft placement. Results Mean age ± SD of horses was 13.7 ± 5.8 years. The mean time of presence of the corneal ulceration was 38.9 ± 21.3 days. Mean time to complete re‐epithelialization of the corneal ulcers after treatment was 20 ± 14.7 days. Horses treated with debridement alone, grid keratotomy and superficial keratectomy healed in a mean time of 15.3 ± 14.6 days, 16 ± 12.6 days, and 22.8 ± 6.7 days, respectively. Conclusions and clinical relevance Horses treated with a single debridement at initial evaluation healed in a significantly shorter time period than horses treated with grid keratotomy or superficial keratectomy. The latter two procedures may be beneficial in the treatment of nonhealing ulceration in horses, but the results of this study suggest that these procedures should only be performed following failure of the ulcer to heal after epithelial debridement.     

Qualitative tear film and conjunctival goblet cell assessment of cats with corneal sequestra

OBJECTIVES: To evaluate the tear film qualitatively and conjunctival goblet cell numbers in cats with and without corneal sequestra. ANIMALS STUDIED AND PROCEDURES: This was a prospective evaluation of 11 cats with corneal sequestra and 14 control eyes that were either the contralateral normal eye when the sequestrum was unilateral or from control cats of similar age with no ocular disease. All cats in this study were examined by a veterinary ophthalmologist. The ophthalmic examinations included a neuro-ophthalmic evaluation, Schirmer tear tests, fluorescein staining, tear film break-up times, applanation tonometry, biomicroscopy, and indirect ophthalmoscopy. The palpebral conjunctiva at the dorsal nasal, ventral nasal, dorsal temporal and ventral temporal fornices were biopsied after topical anesthetic was applied to the cornea and conjunctiva. The conjunctival biopsies were fixed in formalin and sectioned routinely and stained with hematoxylin and eosin, and periodic acid-Schiff. These slides were examined by light microscopy by a blinded examiner. Goblet cell numbers were compared to conjunctival basal epithelial cell numbers by region. The goblet cell numbers by region from the eyes with sequestra was statistically compared to those from eyes without sequestra, with a student's paired t-test. Conjunctival swabs were collected from the cats with corneal sequestra and submitted for polymerase chain reaction for Herpes felis, Chlamydia psiitticia, and Mycoplasma felis. The corneal sequestra were removed by surgical keratectomy and fixed and stained routinely, and examined by light microscopy. RESULTS: No neurologic abnormalities were detected in any of the cats. The Schirmer tear tests (eyes with sequestra 14+/-5.1 mm/min; normal eyes 15+/-6.8 mm/min) and intraocular pressures (eyes with sequestra 21+/-6.6; normal eyes 22+/-5.8) were within normal reference ranges for cats. Biomicroscopic examinations revealed varied sizes and depths of brown- and amber-colored corneal sequestra. No abnormalities were noted on indirect ophthalmoscopic examinations. The tear film break-up time was 21 s (+/-12) for the normal eyes (n=14) and 14 s (+/-13) in eyes with corneal sequestra (n=11). The average goblet/epithelial cell ratios by region for the normal eyes and the eyes with sequestra respectively were 0.66, 0.56 for the dorsal nasal fornix, 0.68, 0.57 for the ventral nasal fornix, 0.63, 0.48 for the temporal dorsal fornix, and 0.55, 0.49 for the temporal ventral fornix. There were no significant differences in tear film break-up times and goblet cell numbers in eyes with corneal sequestra and those without sequestra. Three conjunctival swabs from two of 11 cats with sequestra were positive with PCR for Herpes felis virus. These included one cat with bilateral sequestra and one cat with unilateral corneal sequestrum. CONCLUSIONS: The pathogenesis of feline corneal sequestra does not appear to be linked primarily to abnormal goblet cell numbers, qualitative tear film abnormalities, and accelerated tear film break-up time.     

Density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses

OBJECTIVE: To determine density of corneal endothelial cells and corneal thickness in eyes of euthanatized horses. SAMPLE POPULATION: 52 normal eyes from 26 horses. PROCEDURE: Eyes were enucleated after horses were euthanatized. Eyes were examined to determine that they did not have visible ocular defects. Noncontact specular microscopy was used to determine density of corneal endothelial cells. Corneal thickness was measured, using ultrasonic pachymetry or specular microscopy. RESULTS: Mean density of corneal endothelial cells was 3,155 cells/mm2. Cell density decreased with age, but sex did not affect cell density. Values did not differ significantly between right and left eyes from the same horse. Cell density of the ventral quadrant was significantly less than cell density of the medial and temporal quadrants. Mean corneal thickness was 893 microm. Sex or age did not affect corneal thickness. Dorsal and ventral quadrants were significantly thicker than the medial and temporal quadrants and central portion of the cornea. We did not detect a correlation between corneal thickness and density of endothelial cells in normal eyes of horses. CONCLUSIONS AND CLINICAL RELEVANCE: Density of corneal endothelial cells decreases with age, but corneal thickness is not affected by age or sex in normal eyes of horses. The technique described here may be useful for determining density of endothelial cells in the cornea of enucleated eyes. This is clinically relevant for analyzing corneal donor tissue prior to harvest and use for corneal transplantation.     

Corneal anatomical differences in the aetiology of chronic superficial keratitis

The apparently normal corneas of 14 diseased eyes of German shepherd dogs (GSDs) were shown to possess very thin epithelial layers on microscopy. Normal corneas of 38 GSDs and 113 dogs of various breeds and crossbred animals were compared for epithelial thickness, structure of corneal stroma and corneal strength. Due to lower values for these criteria found in the GSDs they are considered to play an important role in the aetiology of chronic superficial keratitis.     

Autogenous lamellar corneal grafting in dogs

Lamellar, autogenous, corneal grafts were performed on 9 clinically normal dogs (1 eye in each of 2 dogs and both eyes in each of 7 dogs) and 7 dogs with corneal disease (1 eye in each dog). Nylon, polyglycolic acid, polyglactin 910, and polydioxanone suture materials were used in 8-0 to 10-0 sizes. The eyes of the normal dogs were examined weekly for up to 16 weeks; corneal endothelium was reestablished in all eyes by 6 weeks after surgery. The eyes of the dogs with corneal disease were reexamined periodically for up to 9 months. Twenty-two of 23 (95.7%) grafts were considered successful in that they were translucent, and the dogs were able to see after surgery. The suture materials that caused the least tissue reaction were nylon and polyglactin 910. This procedure is indicated for chronic descemetoceles and other perforating corneal disease. It has the advantage of rapidly resolving severe corneal disease, with a high degree of success.     

Results of grid keratotomy, superficial keratectomy and debridement for the management of persistent corneal erosions in 92 dogs

Ninety-two cases of persistent corneal erosions in dogs were analyzed for breed, gender, age and which eye was affected. The results of the treatment of 92 persistent corneal erosions in dogs by superficial keratectomy (SK), grid keratotomy (GK), or debridement with a sterile dry cotton swab are presented. These techniques gave better rates of healing than have been previously reported. All cases of persistent corneal erosions healed in this study. However, it must be noted that three cases treated with debridement only failed to heal after several treatments and were eventually treated with SK. After one procedure 80 out of 92 (87%) had healed. After one procedure, 63% of cases treated with debridement healed, 100% of cases treated with SK healed, and 85% of cases treated with GK healed. At the first postoperative visit, 88% (21/24 cases) of ulcers treated by SK had healed, and 75% (39/52 cases) of ulcers treated by GK had healed. Only 25% of the persistent corneal erosions had healed at the first visit after debridement. All 24 cases of persistent corneal erosions treated with SK healed after one treatment in a mean +/- SD of 9.3 +/- 3.9 days (median of 7 days). Fifty-two cases were managed with GK; 44 (83%) of these healed with one procedure and eight cases required a second GK procedure to resolve. A mean +/- SD of 13.4 +/- 5.1 days (median of 11.5 days) following GK was required for the persistent corneal erosions to heal. Nineteen cases were initially managed by debridement with a dry cotton swab under local anesthesia. Sixteen out of these 19 debridement cases healed (giving an overall healing rate of 84%) in a mean +/- SD time of 23.4 +/- 11.1 days (median 21.5). There were three cases that did not heal with debridement. These cases were debrided at 10-20 day intervals for 30-60 days, and were then treated with SK. Two of these cases healed within 7 days, the other case required 18 days to heal. Sixty-three per cent of persistent corneal erosions treated with debridement healed after one procedure; however, only four out of 19 cases (21%) were healed at the first revisit. Complications were rare: corneal edema occurred in two cases following multiple GK, and excessive granulation tissue in one case was managed with a SK. There was the occurrence of an ulcer adjacent to the surgery site in four cases, two cases following GK and two cases following SK.     

Corneal esthesiometry in the healthy horse

Objective To determine corneal sensitivity in healthy adult horses in order to establish reference values. Animals studied One hundred eyes of 50 healthy adult horses. Procedure Corneal sensitivity was determined by evaluating the corneal touch threshold (CTT) in five different corneal regions using a Cochet‐Bonnet esthesiometer. Results Comparing CTT values (in mm filament length) of the five prescribed corneal regions revealed regional variations in corneal sensitivity, with the central region (21.15 ± 6.23 mm) being the most sensitive, followed by the nasal (20.75 ± 5.14 mm), temporal (20.70 ± 5.37 mm), ventral (20.15 ± 5.88 mm) and dorsal (15.85 ± 3.70 mm) region. However, differences between the central, nasal, temporal and ventral regions were not statistically significant, whereas the dorsal region was significantly (P < 0.0001) less sensitive compared to the other regions. Division of the horses into three age groups revealed an insignificant decrease in corneal sensitivity with age in the nasal, temporal, ventral and central region, and an insignificant increase with age in the dorsal region. Correlation of corneal sensitivity with age was statistically significant in the central, ventral and temporal region. No statistically significant difference in the CTT was found between left and right eyes and between males and females. Conclusions CTT values in 100 eyes of 50 healthy adult horses evaluated with a Cochet‐Bonnet esthesiometer generated reference values. Reference values are necessary to determine alterations of corneal sensation accompanying various eye diseases or systemic diseases.     

The Cryosurgical Treatment of Pigmentary Keratitis in Dogs An Experimental and Clinical Study

Forty normal dogs were exposed to double freezes of a 1 cm diameter area of their central corneas using a liquid nitrogen spray. Postoperative sequelae and final histopathologic results were evaluated. All eyes suffered epithelial damage and developed corneal edema, but dogs followed for 3 weeks returned to a normal or near normal condition. Nine clinical cases of pigmentary keratitis were subsequently treated by cryosurgery. The complications following this technique were similar to those seen in the experimental dogs. Reduction in corneal pigmentation and improvement of vision occurred in all cases.     

Effect of three treatment protocols on acute ocular hypertension after phacoemulsification and aspiration of cataracts in dogs

Objective  To compare the effect of topical latanoprost, intracameral carbachol, or no adjunctive medical therapy on the development of acute postoperative hypertension (POH) and inflammation after routine phacoemulsification and aspiration (PA) of cataracts in dogs.
Design  Retrospective study.
Procedures  Dogs received either one drop of topical 0.005% latanoprost (21 dogs, 39 eyes), an intracameral injection of 0.3 mL of 0.01% carbachol (15 dogs, 30 eyes), or no adjunctive therapy (46 dogs, 90 eyes) immediately following PA of cataract(s). Intraocular pressure (IOP) was measured in all dogs 2 and 4 h after surgery. IOP was measured and aqueous flare assessed at 8 am the day after surgery.
Results  Carbachol-treated dogs had significantly higher mean IOP (33.2 ± SD 20.8 mmHg) 2 h after surgery than dogs receiving no adjunctive therapy (22.0 ± SD 14.1 mmHg) ( P  =  0 .049). There were no significant differences in IOP among groups at any other time point. There were no significant differences in number of POH episodes between dogs treated with carbachol (47%), latanoprost (29%), or dogs that received no adjunctive therapy (33%). There were no significant differences in mean aqueous flare grade between eyes treated with latanoprost (1.7 ± SD 0.4) or carbachol (1.4 ± SD 0.6), and eyes that received no adjunctive therapy (1.7 ± SD 0.4).
Conclusions  Topical 0.005% latanoprost or intracameral injection of 0.3 mL of 0.01% carbachol after PA in dogs did not reduce POH or increase intraocular inflammation compared to dogs not receiving adjunctive therapy after PA of cataracts.     

Measurement of corneal sensitivity in 20 ophthalmologically normal alpacas

Objective To determine corneal sensitivity in 20 healthy adult alpacas (40 eyes) in order to establish reference values. Design Prospective study. Animals Twenty healthy, adult alpacas. Procedures Corneal sensitivity was determined by the corneal touch threshold (CTT) using a Cochet‐Bonnet esthesiometer. Five different regions of the cornea were evaluated (nasal, ventral, lateral, dorsal, and central). Results Corneal touch threshold values (in mm filament length) obtained from five corneal regions demonstrated varying corneal sensitivities. The central region (34.5 ± 7.1 mm) was the most sensitive, followed by the ventral (29.5 ± 7.2 mm), medial (29.3 ± 7.3 mm), dorsal (25.6 ± 6.3 mm), and lateral (21.8 ± 5.7 mm) regions. All pairwise comparisons of regional differences were statistically significant (P < 0.05), except for the comparison between the ventral and medial regions (P = 0.88). Evaluation of the CCT while controlling for age (2–5 years vs. 6–10 years) demonstrated an increased CTT with an increasing age for the central, ventral, medial and lateral regions. A decrease in the CTT of the dorsal region was noted with increasing age. Conclusion and Clinical Relevance Corneal touch threshold values in 40 eyes of 20 healthy adult alpacas were determined using a Cochet‐Bonnet esthesiometer. This study demonstrated the central corneal region to be most sensitive. Values obtained may serve as reference values in subsequent studies.     

Evaluation of matrix metalloproteinase concentrations in precorneal tear film from dogs with Pseudomonas aeruginosa-associated keratitis

OBJECTIVE: To evaluate the changes in concentrations of matrix metalloproteinase (MMP)-2 and MMP-9 in the precorneal tear film of dogs with Pseudomonas aeruginosa-associated keratitis during corneal healing and stromal remodeling. ANIMALS: 10 dogs with unilateral P aeruginosa-associated keratitis and 10 clinically normal dogs. PROCEDURES: Precorneal tear film samples were collected from both eyes of 10 dogs with unilateral P aeruginosa-associated keratitis on the day of admission to the hospital and then at various time points until complete healing of the cornea was achieved. Precorneal tear film samples were also collected from both eyes of 10 clinically normal adult dogs (control group). Concentrations of MMP-2 and MMP-9 in precorneal tear film samples from each group were determined via gelatin zymography for comparison. RESULTS: The proteolytic processes in the ulcerated eyes decreased as corneal healing progressed. On the day of admission, concentrations of latent and active forms of MMP-2 and MMP-9 in ulcerated eyes were significantly higher than values in the contralateral unaffected eyes in dogs with P aeruginosa-associated keratitis; concentrations of latent MMP-2 and MMP-9 were also greater than control group values. Concentrations of latent and active forms of MMP-2 and MMP-9 in the healed eyes of dogs with P aeruginosa-associated keratitis were significantly lower than concentrations in the ulcerated eyes on the day of admission. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that reduction of precorneal tear film concentrations of MMPs by use of proteinase inhibitors may be effective in the treatment of dogs with P aeruginosa-associated keratitis.     

Nonhealing corneal ulcers in cats: 29 cases (1991-1999)

OBJECTIVE: To compare mean healing times after debridement, debridement with grid keratotomy, and superficial keratectomy in cats with nonhealing corneal ulcers. DESIGN: Retrospective study. ANIMALS: 29 cats with 36 nonhealing corneal ulcers. PROCEDURE: Medical records of cats with nonhealing corneal ulcers were reviewed. Signalment, duration of clinical signs, ophthalmic abnormalities, and response to various treatment protocols were recorded. RESULTS: Mean age of affected cats was 7 years, 8 months. Affected breeds included domestic shorthair (17 cats), Persian (9), Himalayan (2), and Siamese (1). Clinical signs were evident for approximately 2 weeks prior to referral. Both eyes were affected in 4 cats. Mean healing time of ulcers treated with superficial debridement was 30 days. Mean healing time of ulcers treated with superficial debridement and grid keratotomy was 42 days. Superficial keratectomy was performed on 2 eyes and resulted in a healing time of 2 weeks. Formation of a corneal sequestrum was evident in 2 of 21 eyes treated with superficial debridement. Formation of a corneal sequestrum was evident in 4 of 13 eyes treated with superficial debridement and grid keratotomy. CONCLUSIONS AND CLINICAL RELEVANCE: Brachycephalic cats appear to be predisposed to developing nonhealing corneal ulcers. The combination of superficial debridement and grid keratotomy did not decrease mean healing time of nonhealing ulcers, compared with superficial debridement alone. Grid keratotomy may predispose cats with corneal ulcers to develop a corneal sequestrum.