Topical tacrolimus in high-risk corneal transplants.

PURPOSE: The purpose of this study was to assess the use of topical tacrolimus ointment in preventing rejection in high-risk corneal grafts, when added to the standard immunosuppressive regimen. METHODS: We conducted an observational, retrospective study using clinical data of high-risk patients subjected to penetrating keratoplasty, who were treated with topical tacrolimus ointment 0.2 mg/g twice a day plus topical dexamethasone 0.1 mg/ml 6 id and compared it with a similar control group treated with topical dexamethasone 0.1 mg/ml 6 id alone. High-risk status was attributed to patients with previous ipsilateral corneal graft failure, two or more quadrants with corneal neovascularization or an infectious or inflammatory corneal disease. RESULTS: We analysed 53 patients in the trial group versus 53 patients in the control group, with similar age, baseline diagnosis and risk factors, and median follow-up times of 30 and and 24 months, respectively. Survival analysis showed a higher graft survival rate at all follow-up periods for patients treated with topical tacrolimus (p < 0.01). No adverse reactions were reported. DISCUSSION: This study shows that topical tacrolimus ointment increases the survival rate of the graft if added to the previous topical steroid regimen in high-risk patients. CONCLUSION: Topical tacrolimus is safe and effective in prolonging graft survival in high-risk patients.

The influence of personality on the quality of vision after multifocal intraocular lens implantation.

OBJECTIVE: To assess the possible correlation between patients' personality traits and subjective perception of quality of vision (QoV), after multifocal intraocular lens (mIOL) implantation. METHODS: patients who had bilateral implantation of a non-diffractive X-WAVE or a trifocal lens were assessed 6 months postoperatively. Patients answered the NEO-Five Factor Inventory (NEO-FFI-20) questionnaire ("Big Five five-factor personality model") to examine their personality. Six months following surgery, patients were asked to fill a QoV questionnaire where they graded the frequency of 10 common visual symptoms. Primary outcomes were to evaluate the correlation between personality scores and the reported frequency of visual disturbances. RESULTS: The study comprised 20 patients submitted to bilateral cataract surgery, 10 with a non-diffractive X-WAVE lens (AcrySof® IQ Vivity) and 10 with a trifocal lens (AcrySof® IQ PanOptix). Mean age was 60.23 (7.06) years. Six months following surgery, patients with lower scores of conscientiousness and extroversion reported a higher frequency of visual disturbances (blurred vision, P = .015 and P = .009, seeing double images P = .018 and P = .006, and having difficulties focusing, P = .027 and P = .022, respectively). In addition, patients with high neuroticism scores had more difficulty focusing (P = .033). CONCLUSIONS: In this study, personality traits such as low conscientiousness and extroversion and high neuroticism significantly influenced QoV perception 6 months after bilateral multifocal lens implantation. Patients' personality questionnaires could be a useful preoperative assessment test to a mIOL.

Comparison of outcomes between cross-linking plus topoguided excimer laser ablation and intrastromal corneal ring segments for keratoconus.

OBJECTIVE: To compare cross-linking (CXL) plus topography-guided photorefractive keratectomy (t-PRK) and intrastromal corneal ring segments (ICRS) in keratoconus patients, at 12 months of follow-up. METHODS: This was a longitudinal, retrospective multi-center study. We included a referred sample of 154 eyes from 149 patients with grade I-III Amsler-Krümeich keratoconus with insufficient corrected-distance visual acuity (CDVA). In group 1 (CXL plus t-PRK, 87 eyes), another possible indication for surgery was evidence of progression. Group 2 (ICRS, 67 eyes) included only eyes with paracentral keratoconus (thinnest point at the inferotemporal quadrant) with coincident axes, and evidence of stabilization was required. A subgroup analysis was performed regarding the disease topographic phenotype. At 12 months postoperatively, visual, refractive, and topographic outcomes were evaluated. RESULTS: Comparison of the outcomes between CXL plus t-PRK (group 1) and ICRS (group 2) showed similar improvements in CDVA (in group 1, CDVA improved 0.18 logMAR, and in group 2 0.12 logMAR, P = .18) and K2 (-2,45 [6.46] D in group 1 and -2.13 [1.67] D in group 2, P = .34) The improvement in cylinder power was greater in group 2 (-2.37 [2.07] D in group 2 versus -1.18 [2.63] D in group 1, P = .003); group 1 had a higher decrease in Kmax (- 3.26 [3.64] versus-1.74 [2.67], P = .001). CONCLUSIONS: Both CXL plus t-PRK and ICRS were equally effective in improving CDVA and topographic parameters in a similar group of keratoconus patients at 12 months.

Patient-reported burden and overall impact of dry eye disease across eight European countries: a cross-sectional web-based survey.

OBJECTIVE: Dry eye disease (DED) is a multifactorial disease involving the tears and ocular surface. It impacts a patient's quality of life (QoL) and ability to perform daily activities. This study assessed the burden of self-reported DED among adults in eight European countries. DESIGN: Online cross-sectional survey. SETTING: General population in France, Italy, Germany, Greece, the Netherlands, Portugal, Spain and Sweden. PARTICIPANTS: Adults aged ≥18 years with (n=6084) and without (n=6161) self-reported DED were recruited via emails and screened. MAIN OUTCOME MEASURES: All participants completed National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ-25) and EuroQol-5 Dimension-5 Level Questionnaire (EQ-5D-5L). All DED participants completed the Eye Dryness Score (EDS) Visual Analogue Scale, and Ocular Comfort Index and Work Productivity and Activity Impairment Questionnaire: Specific Health Problem questionnaires. In addition, half of the respondents with DED completed Survey A (Impact of Dry Eye on Everyday Life) and the other half completed Survey B (Standard Patient Evaluation of Eye Dryness Questionnaire) and Dry Eye Questionnaire-5. RESULTS: Participants with self-reported DED had lower functional vision and lower overall health status than participants without self-reported DED as measured by the NEI-VFQ and EQ-5D-5L, respectively.Increasing self-reported DED severity as measured by the EDS was shown to correspond with worse symptom severity/frequency, lower functional vision, higher impact on work productivity, daily activities and QoL. CONCLUSION: This study showed that patients' reported burden of self-reported DED was similar across the eight European countries. Those with self-reported DED reported lower health status and functional vision compared to those without self-reported DED and these parameters worsen with increasing disease severity.

Surgical Management of Bilateral Limbal Stem Cell Deficiency.

At the age of 43 years-old, a man was left with bilateral limbal stem cell deficiency after an ocular alkaline burn with lime, which resulted in corneal opacification. After multiple unsuccessful surgical attempts to restore vision, including penetrating keratoplasties and Boston keratoprosthesis, visual acuity was counting fingers in the left eye. At 73 years of age, the patient underwent another surgery in his left eye. Cauterization of neovessels and removal of the vascular pannus were followed by partial excision of Tenon's capsule. Penetrating keratoplasty was followed by an intrastromal injection of anti-VEGF (vascular endothelial growth factor), and the ocular surface was covered with amniotic membrane. Postoperatively, the graft was clear with no signs of inflammation; vision improved to 20/50 and remained stable throughout the following two years. Herein we describe some adjunctive procedures that might have delayed failure and rejection of the corneal graft. This case demonstrates the difficulties in treating bilateral limbal stem cell deficiency in a tertiary eye care center with no capacity to perform stem cell therapy.

Two-Photon Imaging for Non-Invasive Corneal Examination.

Two-photon imaging (TPI) microscopy, namely, two-photon excited fluorescence (TPEF), fluorescence lifetime imaging (FLIM), and second-harmonic generation (SHG) modalities, has emerged in the past years as a powerful tool for the examination of biological tissues. These modalities rely on different contrast mechanisms and are often used simultaneously to provide complementary information on morphology, metabolism, and structural properties of the imaged tissue. The cornea, being a transparent tissue, rich in collagen and with several cellular layers, is well-suited to be imaged by TPI microscopy. In this review, we discuss the physical principles behind TPI as well as its instrumentation. We also provide an overview of the current advances in TPI instrumentation and image analysis. We describe how TPI can be leveraged to retrieve unique information on the cornea and to complement the information provided by current clinical devices. The present state of corneal TPI is outlined. Finally, we discuss the obstacles that must be overcome and offer perspectives and outlooks to make clinical TPI of the human cornea a reality.

Anterior Segment Optical Coherence Tomography in the Early Management of Microbial Keratitis: A Cross-Sectional Study.

INTRODUCTION: Infectious keratitis is an important cause of visual loss. The purpose of this study was to investigate anterior segment optical coherence tomography patterns in infectious keratitis and evaluate the role of this tool in the early management of this disorder. MATERIAL AND METHODS: In this cross-sectional study, we included patients with proven infectious keratitis, either by culture or therapeutic trial. Subjects underwent baseline anterior segment optical coherence tomography (Spectralis® anterior segment module, Heidelberg Engineering, Germany) performed by the same operator. We used anterior segment optical coherence tomography vertical and horizontal raster default scans with 6.0 mm scan lines. RESULTS: Twenty-five patients (14 men and 11 women) were included. The most common risk factors identified were ocular trauma (11 cases) and contact lens wear (7 cases). Fifteen patients presented bacterial infection; three, fungal infection; two parasitic infection; and five cases presented a negative microbiological culture. Anterior segment optical coherence tomography depicted nine distinct morphological patterns. DISCUSSION: Anterior segment optical coherence tomography allows the depth of corneal involvement to be assessed. When the only patterns identified were hyperreflective stromal lesion and stromal edema, the visual outcome was better. Cystic spaces were present in severe bacterial keratitis. CONCLUSION: Anterior segment optical coherence tomography can complement biomicroscopy, allowing for a better characterization of corneal involvement at presentation that can help in staging and providing useful prognostic information.

Introdução: As queratites infeciosas são uma causa importante de perda da acuidade visual. O objetivo deste estudo foi investigar padrões das queratites infeciosas na tomografia de coerência ótica do segmento anterior e avaliar o seu papel na orientação precoce desta patologia. Material e Métodos: Neste estudo transversal, incluímos doentes com queratite infeciosa comprovada, por cultura microbiológica ou prova terapêutica. Os doentes foram submetidos a tomografia de coerência ótica do segmento anterior na baseline (Spectralis® anterior segment module, Heidelberg Engineering, Germany) executados pelo mesmo operador. Adquiriram-se cortes verticais e horizontais de 6,0 mm com tomografia de coerência ótica spectral domain. Resultados: Foram incluídos 25 doentes (14 homens e 11 mulheres). Os fatores de risco mais comummente identificados foram o trauma ocular (11 casos) e o uso de lentes de contato (sete casos). Quinze doentes apresentaram infeção bacteriana, três infeção fúngica, dois infeção parasitária e cinco casos apresentaram culturas microbiológicas negativas. Distinguiram-se nove padrões morfológicos na tomografia de coerência ótica do segmento anterior. Discussão: A tomografia de coerência ótica do segmento anterior permite avaliar a profundidade do envolvimento corneano na queratite infeciosa. Quando os únicos padrões identificados eram a lesão estromal hiper-refletiva e edema estromal o outcome visual foi melhor. Os espaços quísticos observaram-se nas queratites bacterianas graves. Conclusão: A tomografia de coerência ótica do segmento anterior permite complementar a biomicroscopia, melhorar o estadiamento e fornecer informação prognóstica útil nas queratites infeciosas.

Considerações sobre o glaucoma facomórfico. Diagnóstico e tratamento / Phacomorphic glaucoma. Diagnose and treatment

RESUMO Os AA fazem considerações sobre clínica, diagnóstico e tratamento do Glaucoma Facomórfico, e ilustram com a apresentação e discussão em quatro pacientes.

ABSTRACT The AA present Phacomorphic Glaucoma discussing the clinic presentation, diagnose and treatment of the disease in four patients.

Neurotrophic Keratopathy: Therapeutic Approach Using a Novel Matrix Regenerating Agent.

PURPOSE: To evaluate the efficacy and tolerance of a new matrix-regenerating agent (RGTA), Cacicol®, a polymer that mimics heparan sulfates bound to extracellular matrix proteins, avoiding its proteolysis, to treat neurotrophic keratopathy (NK). METHODS: Uncontrolled prospective clinical study performed between January 2014 and May 2016. Twenty-five patients (25 eyes) with corneal neurotrophic ulcers, nonresponsive to at least 2 weeks of conservative therapy, were treated with Cacicol, instilled once/twice a week. During follow-up, slit-lamp examination, anterior segment photography, fluorescein-dye testing, and best-corrected visual acuity were analyzed. Ulcer evolution was evaluated using image analysis software (ImageJ®) and healing defined as decrease of the corneal ulcer area. An independent observer measured ulcer area. RESULTS: All patients had complete corneal healing within an average of 4.13 ± 2.32 weeks. Mean ulcer area decreased significantly (P = 0.001) from 16.51% ± 18.56% (1st day) to 8.68% ± 11.25% at the 7th day and to 4.73% ± 10.75% at the 14th day. Compared with day 1, mean ulcer area decreased 60.24% after 7 days (P = 0.001), 54.92% after 14 days (P = 0.059), and 83.00% after 21 days (P = 0.003). Two cases of recurrence (8.0%) were registered. No systemic or local side effects were noticed. CONCLUSIONS: The new regenerating agent, Cacicol, represents an effective and safe therapy to treat NK.

Fusarium dimerum Species Complex (Fusarium penzigii) Keratitis After Corneal Trauma.

We report a case of a keratitis associated with a Fusarium penzigii-a Fusarium dimerum species complex (FDSC)-in a 81-year-old woman after a corneal trauma with a tree branch. At patient admittance, slit lamp biomicroscopy revealed an exuberant chemosis, an inferior corneal ulcer with an associated inflammatory infiltrate, a central corneal abscess, bullous keratopathy and posterior synechiae. Corneal scrapes were obtained for identification of bacteria and fungi, and the patient started antibiotic treatment on empirical basis. Few days later, the situation worsened with the development of hypopyon. By that time, Fusarium was identified in cultures obtained from corneal scrapes and the patient started topical amphotericin B 0.15 %. Upon the morphological identification of the Fusarium as a FDSC, and since there was no clinical improvement, the treatment with amphotericin B was suspended and the patient started voriconazole 10 mg/ml, eye drops, hourly and voriconazole 200 mg iv, every 12 h for 1 month. The hypopyon resolved and the inflammatory infiltrate improved, but the abscess persisted at the last follow-up visit. The molecular identification revealed that the FDSC was a F. penzigii.

Contact lenses as drug controlled release systems: a narrative review / As lentes de contacto como sistema de libertação controlada de fármacos: uma revisão narrativa

ABSTRACT Topically applied therapy is the most common way to treat ocular diseases, however given the anatomical and physiological constraints of the eye, frequent dosing is required with possible repercussions in terms of patient compliance. Beyond refractive error correction, contact lenses (CLs) have, in the last few decades emerged as a potential ophthalmic drug controlled release system (DCRS). Extensive research is underway to understand how to best modify CLs to increase residence time and bioavailability of drugs within therapeutic levels on the ocular surface.These devices may simultaneously correct ametropia and have a role in managing ophthalmic disorders that can hinder CL wear such as dry eye, glaucoma, ocular allergy and cornea infection and injury. In this narrative review the authors explain how the ocular surface structures determine drug diffusion in the eye and summarize the strategies to enhance drug residence time and bioavailability. They synthesize findings and clinical applications of drug soaked CLs as DCRS combined with delivery diffusion barriers, incorporation of functional monomers, ion related controlled release, molecular imprinting, nanoparticles and layering. The authors draw conclusions about the impact of these novel ophthalmic agents delivery systems in improving drug transport in the target tissue and patient compliance, in reducing systemic absorption and undesired side effects, and discuss future perspectives.

RESUMO A forma mais frequente de aplicação terapêutica em oftalmologia consiste na instilação de gotas oculares, mas dadas as limitações anatómicas e fisiológicas do olho, é necessária dosagem frequente com possível repercussão na adesão do paciente à terapêutica. Nas últimas décadas, as lentes de contacto (CLs) têm surgido como um potencial sistema de libertação controlada de fármacos na superfície ocular (DCRS) para correção do erro refrativo. Está em curso uma extensa investigação para entender a melhor forma de modificar as CLs, de modo a aumentar o tempo de residência e a biodisponibilidade do medicamento na superfície ocular dentro de níveis terapêuticos. Ao corrigirem a ametropia, estes dispositivos poderão simultaneamente desempenhar um papel na gestão de perturbações oftalmológicas, tais como a síndrome do olho seco, glaucoma, alergia ocular e infecção corneana, que podem comprometer o porte seguro e confortável das CLs. Nesta revisão narrativa, os autores explicam como as estruturas da superfície ocular determinam a difusão de fármacos no olho e sintetizam as estratégias para aumentar a permanência e biodisponibilidade dos mesmos. Em seguida, apresentam os resultados e as aplicações clínicas das CLs embebidas em fármacos, como DCRS, através da incorporação de barreiras de difusão, de monómeros funcionais, da liberação controlada por iões, da impressão molecular, de nanopartículas e pelo processo camada sobre camada. Os autores concluem avaliando o impacto destes novos sistemas de entrega de agentes farmacológicos ao melhorar o seu transporte no tecido alvo, reduzindo a sua absorção sistémica e os seus efeitos colaterais indesejáveis, e discutem perspectivas futuras.

Anterior Chamber Epithelial Cyst After Uneventful Deep Anterior Lamellar Keratoplasty.

PURPOSE: To report the case of an anterior chamber epithelial cyst after uncomplicated deep anterior lamellar keratoplasty (DALK) treated with a tissue-sparing surgical technique. METHODS: A 35-year-old female patient underwent DALK in her OS because of stage IV keratoconus. The surgery was uneventful, and 3 months postoperatively, best-corrected visual acuity (BCVA) was 20/25. By the sixth postoperative month, a cystic iris lesion was noticed. The lesion grew progressively larger, and BCVA dropped to 20/63 in OS. Cyst excision was performed. RESULTS: No complications possibly related to the surgery were observed. Two years later, BCVA was 20/25 in OS, and there were no signs of cyst recurrence. Histopathological examination of the lesion showed an epithelial implantation cyst. CONCLUSIONS: An anterior chamber epithelial cyst is a sight-threatening condition that may occur after DALK. In selected cases, a conservative surgical approach is an effective treatment option, conveying excellent functional and anatomical outcomes.

Endogenous endophthalmitis secondary to erysipelas.

A 64-year-old woman with chronic right arm lymphoedema presented with progressive and painful vision loss in the right eye following diagnosis of erysipelas in the ipsilateral arm. Visual acuity was light perception. Biomicroscopy revealed marked conjunctival injection, decreased corneal transparency and an inflammatory mass in the anterior chamber, which precluded fundoscopy. The ocular ultrasonography features were consistent with acute endophthalmitis, and the patient was admitted to the hospital. A systemic evaluation, including complete physical examination, echocardiography and blood tests, ruled out other sources of infection besides the cutaneous site. Blood cultures were positive for group A Streptococcus. A diagnosis of unilateral acute endophthalmitis due to group A Streptococcus bacteraemia secondary to erysipelas was made and successfully treated with optimal medical care, including prompt intravitreal and systemic antibiotic administration. Despite resolution of the infectious process, visual acuity did not improve.

Combined use of a femtosecond laser and a microkeratome in obtaining thin grafts for Descemet stripping automated endothelial keratoplasty: an eye bank study.

PURPOSE: To evaluate the use of a femtosecond laser combined with a microkeratome in the preparation of posterior corneal disks for Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS: This experimental study involved ultrathin DSAEK tissue preparation of 22 donor corneas unsuitable for transplantation. The first cut was performed with an Intralase® FS60 laser and the second cut with a Moria CBm 300-µm microkeratome. The thickness of the first cut was modified for each cornea to obtain a final graft thickness of less than 110 µm. Precut and postcut central pachymetry were performed with an ultrasonic pachymeter. Central endothelial cell density (ECD) was calculated before and 24 hours after tissue preparation. RESULTS: Final graft thickness was 105.0 ± 26.1 (SD) µm (range 65-117). The mean microkeratome head cut thickness was 324.5 ± 10.9 µm (range 310-345). Precut and postcut ECDs averaged 2250 ± 222 and 2093 ± 286 cells/mm2, respectively, representing 6.9% of cell loss. No corneas were perforated. CONCLUSION: Femtosecond FS60 lasers and Moria CBm 300-µm microkeratomes can be used sequentially to prepare consistently thin DSAEK grafts with no irregular cuts or cornea perforations.

Femtosecond laser and microkeratome-assisted Descemet stripping endothelial keratoplasty: first clinical results.

AIM: To perform Descemet stripping automated endothelial keratoplasty (DSAEK) using a novel technique to obtain very thin (<100 µm) posterior corneal disks. METHODS: Twenty five DSAEK grafts were prepared with two sequential cuts: the first cut, of variable thickness, was made with a femtosecond laser and the second with a 300 µm microkeratome head. Spectacle corrected visual acuity, endothelial cell density evaluation with specular microscopy and anterior segment optical coherence tomography to measure central and peripheral graft thickness was performed preoperatively and postoperatively at 1, 3 and 6 months. RESULTS: There were no irregular cuts or perforations during tissue preparation. Central graft thickness was 79.6 µm (SD ± 14.5; range 54-98) and 69.3 µm (SD ± 14.2; range 49-96) at 3 and 6 months. Corrected distance visual acuity improved from 0.91 logMAR preoperatively to 0.11 logMAR at 6 months. Donor endothelial cells averaged 2675 cells/mm(2) preoperatively and 1729 cells/mm(2) at 6 months. There were no graft detachments. CONCLUSIONS: This new technique consistently yielded very thin grafts (<100 µm), excellent visual acuity results and good endothelial cell counts. No donor tissue was wasted.

Evaluation of treatment with cysteamine eyedrops for cystinosis with confocal microscopy.

PURPOSE: The purpose of this study was to evaluate the efficacy of cysteamine eyedrops 0.1136% (new formulation, now stable at room temperature without the need for refrigeration for up to 2 months) for the treatment of cystine crystals in the cornea using slit lamp biomicroscopy and confocal microscopy. METHODS: A 20-year-old woman with infantile cystinosis, with a history of kidney transplantation at age 10, was studied. She applied cysteamine eyedrops (0.1136%) 10 times a day (a new formulation, now stable at room temperature without the need for refrigeration for up to 2 months, was prepared for compassionate use). The density of the cystine crystals in the cornea was evaluated using slit lamp biomicroscopy and confocal microscopy (Heidelberg Retina Tomograph 2 equipped with the Rostock Module for the Cornea). RESULTS: The deposits were absent in the surface epithelium and basal cells of the central cornea before and after treatment. We found crystals mainly in the anterior and medium stroma; they had various shapes; were intracellular, rectangular, or fusiform; and showed hyperreflectivity. The posterior stroma showed lower density of the crystals. No deposits in the endothelium were found. Therapy with cysteamine eyedrops reduced the density of the crystals and lessened the photophobia. CONCLUSION: Confocal microscopy is a valuable technique to study cystine crystals of the cornea in vivo. Cysteamine eyedrops appear to be very useful in the treatment of these crystals, especially for photophobic complaints.

Femtosecond laser versus mechanical microkeratomes for flap creation in laser in situ keratomileusis and effect of postoperative measurement interval on estimated femtosecond flap thickness.

PURPOSE: To prospectively compare laser in situ keratomileusis (LASIK) flaps created with a femtosecond laser or a mechanical microkeratome and analyze the effect of the postoperative measurement interval on estimated femtosecond flap thickness using ultrasound (US) pachymetry. SETTING: Department of Ophthalmology, University Hospital of Coimbra, and Coimbra Surgical Centre, Coimbra, Portugal. METHODS: Flaps were created with a Hansatome Zero Compression microkeratome (Group 1), Zyoptix XP keratome (Group 2), or IntraLase 60 kHz femtosecond laser (Groups 3 and 4). Flap thickness was determined by intraoperative US pachymetry immediately after flap creation in Groups 1, 2, and 3. In Group 4, pachymetry was performed 20 minutes after the laser treatment. The main outcome measures were flap thickness and deviation from the target value. RESULTS: Eighty patients had LASIK for myopia or myopic astigmatism. The mean flap thickness was 149.1 microm +/- 24.9 (SD) in Group 1, 124.7 +/- 23.8 microm in Group 2, 143.1 +/- 18.4 microm in Group 3, and 115.5 +/- 12.5 microm in Group 4. The difference in flap thickness between Group 3 and Group 4 was statistically significant (P<.01). The flap thickness deviation from the target value was 22.8 microm in Group 1, 19.0 microm in Group 2, 26.1 microm in Group 3, and 10.4 microm in Group 4. CONCLUSIONS: Results indicate that the time of measurement after femtosecond affects the estimated flap thickness. Waiting 20 minutes after laser treatment permitted easier separation and may eliminate the effect of variable corneal dehydration on flap measurement by subtraction pachymetry.

Diabetes and corneal cell densities in humans by in vivo confocal microscopy.

PURPOSE: Diabetes is accompanied by an increased autofluorescence of the cornea, probably because of accumulation of advanced glycation end products (AGEs). The pathogenic mechanism is still unknown. This study aimed to quantify differences in corneal cell densities between diabetic patients and healthy controls. METHODS: The left cornea of 15 patients with non-insulin-dependent diabetes mellitus (NIDDM) with level of retinopathy 20 according to the Early Treatment of Diabetic Retinopathy Study (ETDRS) and of 15 healthy controls were examined by noninvasive in vivo confocal microscopy in an observational prospective study. The cell densities in 6 corneal layers were determined along the optical axis of the cornea by using stereologic methods. RESULTS: The average cell density per unit area in the superficial and basal epithelium and the endothelial layer was 725 +/- 171, 5950 +/- 653, and 2690 +/- 302 cells/mm in controls and 815 +/- 260, 5060 +/- 301, and 2660 +/- 364 cells/mm in diabetic patients. The cell density per unit volume in the anterior, mid-, and posterior stroma was 26,300 +/- 4090, 19,390 +/- 3120, and 25,700 +/- 3260 cells/mm in controls and 27,560 +/- 3880, 21,930 +/- 2110, and 25,790 +/- 3090 cells/mm in patients with diabetes. In both groups, the density in the midstroma was significantly lower than in both the anterior stroma and the posterior stroma (P < 0.02). The cell density in the basal layer of diabetic patients was significantly lower than in healthy controls (-15.0%, P < 0.0004). In the other layers, no significant differences between both groups (P > 0.07) were observed. CONCLUSIONS: The lower basal cell density found in patients with diabetes may result from a combination of different mechanisms including decreased innervation at the subbasal nerve plexus, basement membrane alterations, and higher turnover rate in basal epithelial cells. The lower cell density in the midstroma of diabetic patients and healthy controls may be attributed in part to differences in oxygen concentration in the stromal layers (depths). Changes in cellular density did not seem to be responsible for the increased autofluorescence in diabetes.

Corneal cell density measurement in vivo by scanning slit confocal microscopy: method and validation.

PURPOSE: Method and validation of a technique to quantify cell density in vivo in 6 corneal layers with a scanning slit confocal microscope (SSCM). METHOD: A confocal image of a small volume in a corneal layer is registered on videotape. Cells or nuclei according to a layer classification are counted manually using an unbiased frame. Surface cell density is calculated from an image on the screen, and volumetric density is obtained using stereological methods. RESULTS: Image distortion on the screen is less than 3%. The classification of a cell layer is verified by determining the position of the measurement volume in the cornea. Validation of density measurements is performed by comparing confocal results with those obtained by histology. The difference between the two methods varies from -24.1% (posterior stroma) to +16.4% (basal layer). Intersession and intrasession repeatability are 8.3 and 5.8%, respectively. The cell density (mean +/- SD) in 20 healthy controls in the superficial, basal and endothelial layers was 759 +/- 162, 5,817 +/- 632 and 2,743 +/- 285 cells.mm(-2) (surface), and in the anterior, mid and posterior stroma 28,616 +/- 3,081, 19,578 +/- 4,421 and 26,073 +/- 5,962 cells.mm(-3) (volumetric). These results are in accordance with those of other investigators. CONCLUSIONS: The SSCM can produce repeatable quantitative measurements of corneal cell density in conscious humans.