Corneal Changes in Neurosurgically Induced Neurotrophic Keratitis

Research

Original Investigation | CLINICAL SCIENCES Corneal Changes in Neurosurgically Induced Neurotrophic Keratitis

Alessandro Lambiase, MD, PhD; Marta Sacchetti, MD, PhD; Alessandra Mastropasqua, MD; Stefano Bonini, MD

IMPORTANCE Neurotrophic keratitis (NK) represents a sight-threatening complication after trigeminal impairment. To our knowledge, the duration for which trigeminal injury may affect corneal structures and function has not been investigated previously.

OBJECTIVE To describe the long-term clinical, morphological, and functional outcomes of NK after neurosurgical trigeminal damage.

DESIGN, SETTING, AND PARTICIPANTS Observational case series performed at a corneal and ocular surface diseases referral center in 2010. Eight consecutive patients with monolateral NK from 1 to 19 years after neurosurgery and 20 age- and sex-matched healthy participants were included.

MAIN OUTCOMES AND MEASURES Complete eye examination, tear film function tests, corneal staining, and Cochet-Bonnet esthesiometry were performed. The number and density of corneal nerves, number of hyperreflective keratocytes, and corneal epithelial, endothelial, and keratocyte cell densities were evaluated by in vivo slit scanning confocal microscopy. Clinical and morphological data were compared with the contralateral unaffected eyes and with the eyes of healthy control participants.

RESULTS All patients showed superficial punctate keratitis and dry eye in the NK eye and a healthy contralateral eye. Decreased corneal sensitivity was observed in all affected eyes (mean [SD], 2.0 [1.9] mm in the affected eyes vs 5.8 [0.3] mm in the contralateral unaffected eyes; P = .01) and was related to decreased subbasal nerve length (P = .04; R = 0.895). Corneal epithelial and endothelial cell densities were significantly decreased and the number of hyperreflective keratocytes was significantly increased in NK eyes compared with contralateral unaffected eyes and with the eyes of healthy participants. A longer duration of NK was associated with lower endothelial cell density (P = .046; R = −0.715).

CONCLUSIONS AND RELEVANCE Corneal morphology and function were impaired even years after neurosurgical trigeminal damage, suggesting that assessment of tear film and corneal sensitivity as well as in vivo confocal microscopy examination should be performed in all patients with trigeminal impairment.

Author Affiliations: Department of Ophthalmology, University of Rome, Campus Bio-Medico, Rome, Italy (Lambiase, Mastropasqua, Bonini); Ospedale San Raffaele di Milano, Istituto di Ricovero e Cura a Carattere Scientifico, Milan, Italy (Sacchetti). Corresponding Author: Stefano Bonini, MD, Department of Ophthalmology, University of Rome, Campus Bio-Medico, Via Alvaro del JAMA Ophthalmol. 2013;131(12):1547-1553. doi:10.1001/jamaophthalmol.2013.5064 Portillo, 200, 00128 Rome, Italy Published online October 24, 2013. ([email protected]).

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he cornea is the most densely innervated human tis- rosurgical damage to the trigeminal nerve as well as their con- sue. Corneal sensory nerves provide protective and tro- tralateral unaffected eyes were included in the study. Twenty T phic support to the cornea by regulating corneal epi- eyes of 20 healthy subjects (mean [SD] age, 53 [15] years; 15 fe- thelium integrity, proliferation, and wound healing.1,2 male, 5 male) were also included as a control group. Experimental and clinical data have clearly demonstrated that The diagnosis of NK was based on the history of trigemi- the impairment of corneal sensitive nerve function induces nal damage after neurosurgical interventions for brain neo- functional and morphological changes of the corneal epithe- plasia associated with ipsilateral corneal hypoesthesia or an- lium, leading to epithelial defects with poor tendency to spon- esthesia. taneous healing.1-3 In humans, injury of the trigeminal nerve All patients underwent evaluation for best spectacle- leads to a decrease or absence of corneal sensation and to de- corrected visual acuity as well as complete eye examination. velopment of neurotrophic keratitis (NK).1,2 This condition is Mechanical corneal sensation was measured at the cen- characterized by impairment of corneal sensitivity, corneal epi- tral cornea with the Cochet-Bonnet esthesiometer (Luneau thelial changes ranging from superficial punctate keratopa- Ophtalmologie). This uses nylon monofilaments that have a thy to corneal ulcer and perforation, stromal scarring, neovas- diameter of 0.027 mm (Toray Industries, Inc), range from 0 to cularization, tear function impairment, and decreased blink 6 cm in length, and apply different pressures to the cornea, reflex. shortening in steps of 1.0 cm if a positive response is not ob- Currently, corneal changes observed in NK are consid- tained. If a positive response is obtained, the thread is ad- ered a consequence of epithelial breakdown, but some evi- vanced by 0.5 cm. The longest filament length resulting in a dence suggests that corneal nerve damage may also induce positive response was considered the corneal sensitivity thresh- changes of keratocytes and corneal endothelium. In fact, the old, which was verified twice.2 recent introduction of in vivo corneal confocal microscopy Tear function was evaluated by the Schirmer I and break-up (IVCM) has allowed for investigation of the entire corneal struc- time tests.13 Corneal fluorescein staining was graded from 0 ture including epithelium, subbasal nerve plexus, kerato- to 5 according to the Oxford scale.13 cytes, and endothelium in healthy and pathological human In vivo slit scanning confocal microscopy examination corneas.4,5 Specifically, decreased corneal sensation in dia- (Confoscan 4; Nidek Technologies) was performed bilaterally betic patients was associated with decreased subbasal nerve in the central cornea of all subjects with a 40×/0.75 objective and basal epithelium density as well as changes in corneal stro- lens. All Confoscan 4 examinations were performed by the mal keratocytes and endothelium.6-8 Patients with herpes sim- same operator (M.S.) using a Z-ring and an internal fixation tar- plex virus keratitis also showed a relationship between de- get to stabilize images. Eyes were anesthetized with 1 drop of creased corneal sensation and changes in subbasal nerve plexus oxybuprocaine hydrochloride,0.4% (benoxinate hydrochlo- and endothelium morphology.9-11 This evidence suggests that ride). The objective lens of the microscope was disinfected with alteration of corneal sensitivity may affect all corneal struc- isopropyl alcohol (70% vol/vol, with swabs). Then, a large drop tures; however, both diabetic keratitis and herpes simplex vi- of Viscotears liquid gel (Carbomer 940; Novartis Pharma) was rus keratitis result from a combination of different mecha- applied to the tip of the lens as an immersion substance. Full- nisms including decreased innervation and metabolic, thickness automated scanning mode with a 5-μm scan step was immune, and cytopathic effects. used during each examination. Each image represents a coro- In this study, we evaluated corneal structures by IVCM in nal section of approximately 425 × 320 μm with magnifica- patients with monolateral NK after neurosurgical trigeminal tion of ×500 and a lateral resolution of 1 μm/pixel. Corneal damage to assess long-term changes of corneal sensitivity and thickness was assessed and a minimum of 3 representative im- morphology. ages were evaluated for superficial and basal epithelium, subbasal nerve plexus, superficial and deep stromal layer, and endothelium.4,5 Methods Two masked observers evaluated the confocal images (M.S. and A.M.). The epithelial, stromal, and endothelial cells were This study was performed in accordance with the Declaration manually counted using Adobe Photoshop 6.0 software (Adobe of Helsinki. The study was approved by the institutional re- Systems). All the cells were counted within a 0.05-mm2 frame view board of the University of Rome, Campus Bio-Medico, and to calculate the cell density, which was expressed as the num- written informed consent was obtained from the patients and ber of cells per square millimeter. Nerve density was assessed healthy volunteers before examinations were performed. by measuring the total length of the nerve fibers in microm- Inclusion criteria were the diagnosis of monolateral NK at eters per frame. Main nerve trunks were defined as the total stage 1 after neurosurgery1,2 and a corneal scarring grade of 0.5 number of main nerve trunks in 1 image after analyzing the im- or lower according to the Fantes scale.12 Exclusion criteria were ages anterior and posterior to the analyzed image to confirm the presence of diabetes mellitus, previous intraocular sur- that these did not branch from other nerves. Nerve branch- gery, history of ocular trauma, herpetic keratitis, and/or other ing was defined as the total number of nerve branches in 1 ocular-associated diseases, use of topical treatments with the image.14 Tortuosity and reflectivity were classified according exception of ocular lubricants, and use of contact lenses. to criteria described by Oliveira-Soto and Efron.15 Eight eyes of 8 consecutive patients (mean [SD] age, 49 [18] Statistical analysis was performed using Wilcoxon rank test years; 6 female, 2 male) with monolateral NK caused by neu- and Mann-Whitney U test to assess differences between groups.

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Table 1. Clinical and Demographic Characteristics of the Patients With Neurotrophic Keratitis Included in the Study

Patient No. Characteristic 123456 7 8 Age, y 38 52 42 61 32 69 77 25 Sex M F F F M F F F Disease for Acoustic Meningioma Acoustic Chondroma Meningioma Meningioma Meningioma Meningioma neurosurgery neuroma neuroma Time from trigemi- 65771 8 719 nal damage, y Duration of NK, y 5 5 5 5 1 7 7 18 Previous NK Tarsorrhaphy CL CL AMT Autologous Tarsorrhaphy Tarsorrhaphy, Tarsorrhaphy treatments serum, CL CL Symptoms Mild redness Mild dryness None Visual None Visual Mucous None impairment impairment secretion Lagophthalmos Mild Absent Moderate Absent Absent Absent Moderate Mild BCVA, decimal units 0.7 0.8 0.8 0.3 0.6 0.4 0.7 0.8 Central corneal sen- 10400 3 4 4 sitivity threshold, cm Break-up time, s 8 5 4 2 6 7 2 6 Schirmer test, mm/5 >10 9 3 7 >10 7 >10 >10 min Oxford score 1 1 1 2 1 2 1 3

Abbreviations: AMT, amniotic membrane transplantation; BCVA, best-corrected visual acuity; CL, contact lens; NK, neurotrophic keratitis.

Spearman ρ test was used to correlate clinical, demographic, No significant correlations were observed between cor- and morphological parameters. We used SPSS version 18 sta- neal sensitivity and the tear function test and corneal stain- tistical software (SPSS Inc). P < .05 was considered statisti- ing results (P = .52 and P = .20, respectively), while the higher cally significant. corneal sensitivity was significantly correlated with a longer historyofNK(P = .048; R = 0.712). Results of IVCM evaluations are showed in Table 2.Eyes Results with NK showed a significant decrease of superficial and basal epithelial cell densities when compared with both contralat- Clinical characteristics of the patients are summarized in eral unaffected eyes (mean [SD] superficial epithelial cell den- Table 1. At the inclusion, all patients showed a stage 1 mono- sity, 1068 [567] vs 1877 [490] cells/mm2, respectively; P = .047; lateral NK according to criteria described by Mackie1 with mild mean [SD] basal epithelial cell density, 3241 [600] vs 4366 [794] to severe superficial punctate keratitis and were being treated cells/mm2, respectively; P =.04)(Figure 1) and with healthy only with preservative-free artificial tears. All contralateral eyes eyes of control participants (mean [SD] superficial epithelial showed absence of pathological changes and normal corneal cell density, 2145 [401] cells/mm2; P = .04; mean [SD] basal epi- sensitivity, Schirmer test results, and break-up times. thelial cell density, 5732 [1358] cells/mm2; P = .004). Patients underwent neurosurgery in the past 1 to 19 years Subbasal nerves were also significantly reduced as com- (mean [SD], 7.5 [5] years) and were diagnosed as having NK from pared with both contralateral unaffected eyes (mean [SD] num- 1 to 24 months after neurosurgery. All patients also had a his- ber of nerve trunks, 1.0 [1.2] vs 4.4 [1.1], respectively; P = .04; tory of corneal ulcer 1 to 18 years (mean [SD], 6.6 [5] years) af- and mean [SD] total nerve length, 1814 [2614] vs 11 606 [5175] ter the onset of NK. Four patients had damage of the seventh μm/mm2, respectively; P =.04)(Figure 2) and healthy eyes cranial nerve with mild facial hemipalsy (Table 1). (mean [SD] number of nerve trunks, 4.5 [0.9]; P = .003; mean All affected eyes showed a significant decrease in me- [SD] total nerve length, 15 250 [2440] μm/mm2; P = .001). In chanical corneal sensitivity evaluated by Cochet-Bonnet es- NK eyes, the lower subbasal nerve length directly correlated thesiometry when compared with the contralateral unaf- with lower corneal sensitivity values (P = .04; R = 0.895). fected eye (mean [SD], 2.0 [1.9] vs 5.8 [0.3] mm, respectively; The number of hyperreflective keratocytes was signifi- P = .01). Fluorescein staining demonstrated mild to severe epi- cantly increased in NK eyes when compared with contralat- theliopathy in NK eyes compared with unaffected eyes (mean eral unaffected eyes (mean [SD], 4.0 [2.2] vs 1.5 [2.2] hyperre- [SD]Oxfordscore,1.6[0.7]vs0,respectively;P < .001). Eyes flective keratocytes/frame, respectively; P = .04) and with with NK also showed a significant decrease in break-up time healthy eyes (mean [SD], 1.2 [1.2] hyperreflective keratocytes/ compared with contralateral unaffected eyes (mean [SD], 5.0 frame; P =.02)(Figure 3). [2.0] vs 7.5 [2.3] seconds, respectively; P = .004), while Schirmer Interestingly, corneal endothelial cell density was signifi- test results were not significantly different between the con- cantly reduced in NK eyes when compared with both contra- tralateral and pathological eyes (P = .66). lateral unaffected eyes (mean [SD], 2187 [582] vs 3059 [352]

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Table 2. Results of In Vivo Confocal Microscopy Evaluations in Patients Table 2. Results of In Vivo Confocal Microscopy Evaluations in Patients With Monolateral Neurotrophic Keratitis Compared With Contralateral With Monolateral Neurotrophic Keratitis Compared With Contralateral Unaffected Eyes and With Eyes of Healthy Participants Unaffected Eyes and With Eyes of Healthy Participants (continued)

P P Variable Mean (SD) Value Variable Mean (SD) Value Central corneal thickness, μm Beadlike formations, No./frame Contralateral eyes 530 (56) Contralateral eyes 7.4 (6.0) NK eyes 560 (93) .28a NK eyes 2.5 (3.1) .14a Healthy eyes 551 (71) .39b Healthy eyes 5.9 (3.2) .28b Superficial epithelial cell density, Nerve branching, No./frame cells/mm2 Contralateral eyes 2.7 (3.0) Contralateral eyes 1877 (490) NK eyes 0.3 (0.6) .03a NK eyes 1068 (567) .047a Healthy eyes 3.1 (2.5) .03b Healthy eyes 2145 (401) .04b Endothelial cell density, cells/mm2 Basal epithelial cell density, cells/mm2 Contralateral eyes 3059 (352) Contralateral eyes 4366 (794) NK eyes 2187 (582) .01a NK eyes 3241 (600) .04a Healthy eyes 2960 (323) .004b b Healthy eyes 5732 (1358) .004 Abbreviation: NK, neurotrophic keratitis. Anterior stromal cell density, a Comparing NK eyes vs contralateral unaffected eyes (Wilcoxon rank test). cells/mm2 b Comparing NK eyes vs healthy eyes (Mann-Whitney U test). Contralateral eyes 949 (243) NK eyes 990 (274) .60a Healthy eyes 894 (250) .43b cells/mm2, respectively; P = .01) and with healthy eyes (mean Hyperreflective keratocytes, [SD], 2960 [323] cells/mm2; P = .004) (Figure 4A-C). Eyes with No./frame NK showed a significant correlation between the longer du- Contralateral eyes 1.5 (2.2) ration of NK and the lower endothelial cell density (P = .046; a NK eyes 4.0 (2.2) .04 R = −0.715) (Figure 4D). b Healthy eyes 1.2 (1.2) .02 No significant difference in all morphological parameters Posterior stromal cell density, were observed in the subgroup of patients with both NK and cells/mm2 lagophthalmos. Contralateral eyes 859 (107) NK eyes 885 (238) .88a Healthy eyes 750 (145) .41b Nerve trunks, No. Discussion Contralateral eyes 4.4 (1.1) In this study, we demonstrated that trigeminal nerve damage NK eyes 1.0 (1.2) .04a induces long-term corneal functional and morphological Healthy eyes 4.5 (0.9) .003b changes. All patients with NK showed decreased corneal sen- Total nerve length sitivity, superficial punctate keratitis, and dry eye associated μm/mm2 with corneal epithelium, nerve, keratocyte, and endothe- Contralateral eyes 11 606 (5175) lium alterations as demonstrated by IVCM. Our study confirmed that the impairment of corneal sen- NK eyes 1814 (2614) .04a sitivity in patients with NK is related to a significant impair- Healthy eyes 15 250 (2440) .001b ment of subbasal nerve plexus. Similar associations between μm/Frame impairment of corneal sensitivity and nerve morphology Contralateral eyes 1549 (690) changes have been previously demonstrated in patients with a NK eyes 242 (348) .04 diabetes, dry eye, pseudoexfoliation syndrome, and herpes b Healthy eyes 2035 (325) .001 simplex virus keratitis and after refractive surgery.6,9,16-19 Nerve tortuosity score Other long-term changes in NK, such as decreased epithe- Contralateral eyes 1.7 (0.5) lial and increased hyperreflective keratocyte cell densities, were NK eyes 0.5 (0.6) .15a detected by IVCM. It is generally accepted that corneal sen- Healthy eyes 1.6 (0.6) .25b sory nerves play a key role in maintaining the vitality, metabo- 2 Nerve reflectivity score lism, and replenishment of corneal epithelial cells. The lower Contralateral eyes 1.5 (1.6) epithelial cell density in NK eyes may result from the decreased subbasal nerve supply; however, a pathological ef- NK eyes 0.8 (1.0) .27a fect on the epithelium from the associated dry eye cannot be Healthy eyes 1.5 (0.5) .16b excluded.20,21 In fact, loss of corneal sensation is known to lead (continued) to tear and blink reflex dysfunction and to the development

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Figure 1. Corneal Basal Epithelial Cell Density

A B C 6000

2 5000

4000 a

3000

2000 Basal Epithelial 1000 Cell Density, Cells/mm Cell Density, 0 Neurotrophic Contralateral Keratitis Eyes Unaffected Eyes

Corneal basal epithelial cell density was significantly decreased in neurotrophic C, Error bars indicate standard deviation. keratitis (A) when compared with contralateral unaffected eyes (B and C). aP =.04.

Figure 2. Corneal Subbasal Nerve Length

A B C

2 18 000 16 000 14 000 12 000 10 000 8000 6000 a 4000 2000

Total Nerve Length, μm/mm Total 0 Neurotrophic Contralateral Keratitis Eyes Unaffected Eyes

Corneal subbasal nerve length was significantly decreased in neurotrophic C, Error bars indicate standard deviation. keratitis (A) when compared with contralateral unaffected eyes (B and C). aP =.04.

Figure 3. Hyperreflective Keratocytes

A B C 7 a 6 5 4 3

No./Frame 2 1

Hyperreflective Keratocytes, Hyperreflective 0 Neurotrophic Contralateral Keratitis Eyes Unaffected Eyes

The number of hyperreflective keratocytes was significantly increased in (B and C). C, Error bars indicate standard deviation. neurotrophic keratitis (A) when compared with contralateral unaffected eyes aP =.04.

of corneal epithelial damage due to a consequent loss of key importance of ocular sensory innervation on survival of the trophic neural factors supplied in tears. In line with this hy- human corneal endothelium. In fact, while in rabbits the in- pothesis, our patients with NK had a decreased tear break-up nervation of the endothelium is well described, in humans no time associated with punctate keratopathy.2,22,23 evidence of nerve to endothelium interaction has been In patients with NK, the presence of increased hyperre- reported.24 Sensory nerve impairment may result in changes flective keratocytes, a common finding following corneal in- in aqueous humor and in the corneal microenvironment that jury, infection, or inflammation, demonstrates that the dis- ultimately lead to a loss of trophic factors critical to endothe- ease is still ongoing even years after the neurosurgical lial cell function and survival.25 Previous studies have shown trigeminal injury.4 an impairment of the endothelium pump function in pa- A surprising novel finding was a decrease in endothelial tients with NK, and decreased endothelial cell density was de- cell density in NK eyes. This gives a new perspective on the scribed in patients with herpes simplex virus keratitis, pseu-

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Figure 4. Corneal Endothelial Cell Density

A B

C D

2 4000 20 3500 3000 a 15 Corneal endothelial cell density was 2500 significantly decreased in 2000 10 neurotrophic keratitis (A) when compared with contralateral 1500 NK Duration, y NK Duration, 5 unaffected eyes (B and C). C, Error 1000 bars indicate standard deviation. D, 500 The lower endothelial cell density was 0 0 related to the longer duration of Endothelial Cell Density, Cells/mm Cell Density, Endothelial Neurotrophic Contralateral 0 500 1000 1500 2000 2500 3000 neurotrophic keratitis (NK). R2 Keratitis Eyes Unaffected Eyes Endothelial Cell Density, Cells/mm2 linear = 0.565. aP = .01.

doexfoliation syndrome, and diabetes—all conditions cluded only patients with surgically induced trigeminal damage characterized by decreased corneal sensitivity and subbasal and monolateral NK in this study to avoid interindividual vari- plexus changes.6,9,10,18,26-28 These data suggest that impair- ability and comorbidities, the strength of this study is limited ment of corneal sensory nerves induces a prompt alteration by the small number of patients. A larger trial with long-term of endothelial function as demonstrated by previous studies follow-up should be performed to confirm this hypothesis. but also loss of cells over time.26 Lower endothelial cell den- In conclusion, this study demonstrated that impairment sity was also related to a longer duration of NK, suggesting that of corneal sensory nerves induces anatomical changes of all impairment of corneal sensory nerves induces immediate func- layers of the cornea and that NK never completely resolves. tional and long-lasting morphological alterations of endothe- In vivo corneal confocal microscopy analysis confirmed the lial cells. Since there is no evidence that human endothelial presence of active pathological changes involving all corneal cells divide under normal circumstances, endothelial cell den- structures, including endothelial cell loss, suggesting that IVCM sity may be a useful marker for the evaluation of long-term al- should be performed for better long-term management of pa- terations due to loss of trophic support. Although we in- tients with NK.

ARTICLE INFORMATION Critical revision of the manuscript for important effect of sensory denervation. AMA Arch Submitted for Publication: March 5, 2013; final intellectual content: Lambiase, Sacchetti, Bonini. Ophthalmol. 1954;52(1):46-57. revision received May 2, 2013; accepted May 8, Statistical analysis: Lambiase, Sacchetti, 4. Niederer RL, McGhee CN. Clinical in vivo 2013. Mastropasqua. confocal microscopy of the human cornea in health Administrative, technical, or material support: and disease. Prog Retin Eye Res. 2010;29(1):30-58. Published Online: October 24, 2013. Mastropasqua. doi:10.1001/jamaophthalmol.2013.5064. Study supervision: Lambiase, Bonini. 5. Patel DV, McGhee CN. In vivo confocal microscopy of human corneal nerves in health, in Author Contributions: Drs Lambiase and Sacchetti Conflict of Interest Disclosures: None reported. had full access to all of the data in the study and ocular and systemic disease, and following corneal surgery: a review. Br J Ophthalmol. take responsibility for the integrity of the data and REFERENCES the accuracy of the data analysis. Drs Lambiase and 2009;93(7):853-860. Sacchetti contributed equally to this study. 1. Mackie IA. Neuroparalytic keratitis. In: 6. Rosenberg ME, Tervo TM, Immonen IJ, Müller Study concept and design: Lambiase, Sacchetti, Fraunfelder F, Roy FH, Meyer SM, eds. Current LJ, Grönhagen-Riska C, Vesaluoma MH. Corneal Bonini. Ocular Therapy. Philadelphia, PA: WB Saunders; structure and sensitivity in type 1 diabetes mellitus. Acquisition of data: Lambiase, Sacchetti, 1995:452-454. Invest Ophthalmol Vis Sci. 2000;41(10):2915-2921. Mastropasqua. 2. Bonini S, Rama P, Olzi D, Lambiase A. 7. Tavakoli M, Quattrini C, Abbott C, et al. Corneal Analysis and interpretation of data: Lambiase, Neurotrophic keratitis. Eye (Lond). confocal microscopy: a novel noninvasive test to Sacchetti. 2003;17(8):989-995. diagnose and stratify the severity of human diabetic Drafting of the manuscript: Lambiase, Sacchetti, 3. Sigelman S, Friedenwald JS. Mitotic and neuropathy. Diabetes Care. 2010;33(8):1792-1797. Mastropasqua. wound-healing activities of the corneal epithelium:

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