Best Disease: Global Mutations Review, Genotype-Phenotype Correlation, and Prevalence Analysis in the Israeli Population.

Purpose: To review all reported disease-causing mutations in BEST1, perform genotype-phenotype correlation, and estimate disease prevalence in the Israeli population. Methods: Medical records of patients diagnosed with Best disease and allied diseases from nine Israeli medical centers over the past 20 years were collected, as were clinical data including ocular findings, electrophysiology results, and retina imaging. Mutation detection involved mainly whole exome sequencing and candidate gene analysis. Demographic data were obtained from the Israeli Bureau of Statistics (January 2023). A bibliometric study was also conducted to gather mutation data from online sources. Results: A total of 134 patients were clinically diagnosed with Best disease and related conditions. The estimated prevalence of Best disease was calculated to be 1 in 127,000, with higher rates among Arab Muslims (1 in 76,000) than Jews (1 in 145,000). Genetic causes were identified in 76 individuals (57%), primarily showing autosomal-dominant inheritance due to BEST1 mutations (58 patients). Critical conserved domains were identified consisting of a high percentage of dominant missense mutations, primarily in transmembrane domains and the intracellular region (Ca2+ binding domain) of the BEST1 protein. Conclusions: This study represents the largest cohort of patients with Best disease reported in Israel and globally. The prevalence in Israel is akin to that in Denmark but is lower than that in the United States. Critical conserved domains within the BEST1 protein are pivotal for normal functioning, and even minor missense alterations in these areas lead to a dominant disease manifestation. Genetic testing is indispensable as the gold standard for Best disease diagnosis due to the variable clinical presentation of the disease.

Refractive predictive errors using Barrett II, Hoffer-Q, and SRKT formulae for pediatric IOL implantation.

PURPOSE: To compare the accuracy of the Barrett II universal (BU II) formula, Hoffer-Q, and SRKT formulae following lensectomy and IOL implantation in a large pediatric cohort. METHODS: Retrospective study of children who underwent lensectomy and IOL implantation between 2015 and 2023 at Hadassah-Hebrew University Medical Center, Jerusalem, Israel. RESULTS: One hundred and fifty-one eyes of 104 children aged 6.0 ± 3.9 years were included. The mean prediction error (PE) was - 0.08 ± 1.54 diopters (D) with BU II, 0.24 ± 1.46 D with Hoffer-Q, and 0.71 ± 1.92 D with SRKT (P = 0.10). In eyes with axial length (AL) < 22 mm, BU II and Hoffer-Q had a smaller PE than SRKT (P = 0.024). In eyes with AL ≥ 22 mm, BU II had a smaller PE than Hoffer-Q (P = 0.048). In children 24 months or older at surgery, BU II had a smaller PE than SRKT and Hoffer-Q (P = 0.012). However, in younger children, no difference was found between the formulae (P = 0.61). For mean k-values ≥ 44.5 D, BU II and Hoffer-Q had a smaller PE than SRKT (P = 0.002). An absolute prediction error < 1.0 D was obtained with BU II in 66% of eyes and SRKT in 35% (P = 0.01). CONCLUSIONS: The BU II formula performed well with a small prediction error. No significant difference in PE was detected overall between the formulae. However, only BU II demonstrated a stable prediction error at varying axial lengths, K-readings, and ages. As the biometric parameters of the developing eye change with growth, the BU II formula offers a reliable and stable option for pediatric IOL calculation.

Enhanced S-Cone Syndrome Masquerading as TORCH in an Infant and a Toddler.

PURPOSE: To report two cases masquerading as TORCH but eventually diagnosed with Enhanced S-cone Syndrome (ESCS). METHODS: Descriptive case report. RESULTS: Case 1: A ten-month-old boy presented with high hypermetropia, strabismus and bilateral chorioretinal pigmented scars with a history of cat scratch of his mother during pregnancy. He was treated for suspected toxoplasma retinitis. Choroidal neovascular membranes (CNV) were diagnosed bilaterally and treated with intravitreal bevacizumab. Genetic testing showed homozygote mutation in NR2E3 gene. Case 2: A two-year old girl presented with bilateral high hypermetropia and strabismus. Funduscopy revealed extrafoveal chorioretinal lesions and surrounding subretinal fibrosis. An elevated titer of anti-toxocara IgG antibodies was detected and managed accordingly. LE CNV was diagnosed and treated with intravitreal bevacizumab. Genetic testing disclosed homozygote mutation in NR2E3. CONCLUSION: Ocular manifestations in ESCS can be reminiscent to TORCH. CNV may develop with an incidence of 15%. We report the youngest patient with ESCS-associated CNV.

Variable phenotype of Knobloch syndrome due to biallelic COL18A1 mutations in children.

PURPOSE: Knobloch syndrome is a rare, recessively inherited disorder classically characterized by high myopia, retinal detachment, and occipital encephalocele. Our aim is to report the clinical and genetic findings of four Israeli children affected by Knobloch syndrome. METHODS: Retrospective study of four patients diagnosed with Knobloch syndrome, who underwent full ophthalmic examination, electroretinography, and neuroradiologic imaging. Genetic analysis included whole exome sequencing (WES) and Sanger sequencing. RESULTS: The four patients included in this study had high myopia and nystagmus at presentation. Ocular findings included vitreous syneresis, macular atrophy, macular coloboma, and retinal detachment. One child had iris transillumination defects and an albinotic fundus, initially leading to an erroneous clinical diagnosis of albinism. Electroretinography revealed a marked cone-rod pattern of dysfunction in all four children. Brain imaging demonstrated none to severe occipital pathology. Cutaneous scalp changes were present in three patients. WES analysis, confirmed by Sanger sequencing revealed COL18A1 biallelic null mutations in all affected individuals, consistent with autosomal recessive inheritance. CONCLUSIONS: This report describes variable features in patients with Knobloch syndrome, including marked lack of eye pigment similar to albinism in one child, macular coloboma in two children as well as advanced cone-rod dysfunction in all children. One patient had normal neuroradiologic findings, emphasizing that some affected individuals have isolated ocular disease. Awareness of this syndrome, with its variable phenotype may aid early diagnosis, monitoring for potential complications, and providing appropriate genetic counseling.

Ophthalmology practice during the COVID-19 pandemic.

OBJECTIVE: To present an established practice protocol for safe and effective hospital-setting ophthalmic practice during the coronavirus disease 2019 (COVID-19) pandemic. METHODS AND ANALYSIS: Literature was reviewed to identify articles relevant to COVID-19 pandemic and ophthalmology. The following keywords were used: COVID-19, SARS-CoV-2 and telemedicine, combined with eye, ophthalmology, conjunctivitis and tears. Data were extracted from the identified manuscripts and discussed among subspecialists to obtain consensus evidence-based practice. RESULTS: A protocol for ophthalmic practice in the era of COVID-19 pandemic was established. The protocol covered patient screening, clinic flow, required personal protective equipment and modifications of ophthalmic equipment for improved safety. CONCLUSION: Important literature emerged with respect to the practice of ophthalmology in the era of COVID-19. An evidence-based ophthalmic practice protocol was established and should be modified in the future to accommodate new insights on the COVID-19 pandemic.

Pediatric Acquired and Progressive Retinal Nerve Fiber Layer Myelination Following Idiopathic Intracranial Hypertension.

Few anecdotal reports have documented new onset and progression of myelination of the retinal nerve fiber layer. The authors report the unusual onset and progression of acquired myelination of the retinal nerve fiber layer in two children, following the diagnosis of presumed idiopathic intracranial hypertension. The nosologic relationship between myelination of the retinal nerve fiber layer and idiopathic intracranial hypertension is unclear and requires elucidation by further studies. [J Pediatr Ophthalmol Strabismus. 2019;56:e57-e59.].

An Ashkenazi Jewish founder mutation in CACNA1F causes retinal phenotype in both hemizygous males and heterozygous female carriers.

Background: Mutations in CACNA1F have been mainly associated with X-linked incomplete congenital stationary night blindness (icCSNB). Variable phenotypic expression in females was reported in some families. We report here three non-related Ashkenazi Jewish families originating in Eastern Europe, that included males and a many affected females, initially diagnosed with variable retinal phenotypes.Materials and Methods: Whole exome sequencing (WES), Sanger sequencing and microsatellite haplotyping were used for genetic analysis. Complete ophthalmologic examination was performed including visual acuity, refraction, colour vision, slit-lamp, fundoscopy and electroretinography (ERG).Results: We identified four affected males, showing moderate visual impairment, and seven female carriers, six of them presenting mild to moderate visual impairment. Infantile nystagmus was found in all affected males and in 5/7 females. Nyctalopia and myopia were common in both males and females. Initial clinical differential diagnosis included cone-dystrophy, cone-rod dystrophy, cone-dystrophy with supernormal rod response or CSNB based on ERG results. WES and Sanger sequencing revealed a previously described missense mutation c.2225T>G; p.(F742C) in CACNA1F (NM_001256789.2) in all three families, encompassed by a shared haplotypeConclusions: Our data suggests that p.(F742C) in CACNA1F is an X-linked founder mutation in Ashkenazi Jews originating in Eastern Europe. This mutation causes a mild-to-moderate icCSNB phenotype, expressed in most female carriers. A targeted test for this variant in suspected patients may initiate diagnostic analysis. Our results highlight the relevance of WES in the clinic, allowing fast and accurate diagnosis for unclear and variable clinical phenotype and in pedigrees with multiple possible inheritance patterns.

Homozygous stop-gain variant in LRRC32, encoding a TGFß receptor, associated with cleft palate, proliferative retinopathy, and developmental delay.

The transforming growth factor-beta (TGFß) signaling pathway is essential for palatogenesis and retinal development. Glycoprotein A repetitions predominant (GARP), encoded by LRRC32, is a TGFß cell surface receptor that has been studied primarily in the context of cellular immunity. We identified a homozygous stop-gain variant in LRRC32 (c.1630C>T; p.(Arg544Ter)) in two families with developmental delay, cleft palate, and proliferative retinopathy. Garp-null mice have palate defects and die within 24 h after birth. Our study establishes LRRC32 as a candidate disease-associated gene in humans and lends further support to the role of the TGFß pathway in palatogenesis and retinal development.

Nitric oxide secretion in human conjunctival fibroblasts is inhibited by alpha linolenic acid.

PURPOSE: It is known that both human conjunctival fibroblasts (HCF) and corneal epithelial (HCE) cells contribute to the inflammatory process in the ocular surface by releasing inflammatory cytokines. In addition, nitric oxide (NO) has an important role in inflammatory responses in the ocular surface. In the present study, we aimed to characterize the capacity of these cells to release nitric oxide in response to cytokines and Lipopolysaccharide (LPS), and show that Alpha-linoleic acid (ALA) inhibits these responses. METHODS: HCF, HCE cells, peripheral blood mononuclear cells (PBMCs) and co-culture of HCF and PBMC were treated with different combinations of inflammatory inducers, including interleukin)IL- (6, tumor necrosis factors (TNF)-α, interferon (IFN)- γ and IL-1ß and LPS. Nitrite levels were measured in cell supernatants with and without ALA by the Griess reaction test at 24, 48 and 72 h respectively. Expression of nitric oxide synthase 2 (NOS-2) was evaluated by real-time PCR. RESULTS: All cytokine combinations had an inducible effect on nitrite secretion in HCF, PBMC and co-cultured PBMC and HCF, but not in HCE cells. Treatment with a combination of IL-6, LPS, TNF-α, IFN- γ and IL-1ß induced the highest nitrite secretion (2.91 fold, P < 0.01) as compared to cells incubated in medium alone. nitrite secretion was reduced by 38.9 % (P < 0.05) after treatment with ALA alone. Co-culturing PBMC with HCF with and without ALA treatment demonstrated similar results in nitrite level as,compared to PBMC alone. In addition, ALA significantly decreased NOS-2 expression in HCF by 48.9 % (P < 0. 001) after 72 h. CONCLUSIONS: The decrease in nitrite release and inhibition of NOS-2 expression indicate that ALA may have an anti-inflammatory effect both on HCF and on peripheral immune cells. This indicates that ALA may serve as a potent anti-inflammatory agent in ocular surface inflammation.

Ophthalmologic Findings in H Syndrome: A Unique Diagnostic Clue.

BACKGROUND: H syndrome is an autosomal recessive histiocytosis with multisystemic involvement caused by mutations in the SLC29A3 gene. The term H syndrome was coined to denote the major clinical findings which include hyperpigmentation, hypertrichosis, hearing loss, hepatosplenomegaly, hypogonadism, hyperglycemia/diabetes mellitus and hallux valgus/flexion contractures. Almost 100 individuals affected with this disorder have been reported, however, a thorough evaluation of the ophthalmologic features of H syndrome has not yet been performed. MATERIALS AND METHODS: Ophthalmic examination of a 50-year-old male with H syndrome. Mutation analysis of SLC29A3 was also performed in this patient. RESULTS: Ophthalmic findings included; shallow orbits with exorbitism, bilateral pterygium, limbal thickening, corneal arcus and cortical cataract. We also review ophthalmologic findings in previously reported H syndrome patients. CONCLUSIONS: The presence of dilated lateral scleral vessels, corneal arcus and shallow orbits should raise the suspicion of H syndrome, especially when seen in young age.

Expression and activation of toll-like receptor 3 and toll-like receptor 4 on human corneal epithelial and conjunctival fibroblasts.

BACKGROUND: Toll-like receptors (TLRs) are recognized as important contributors to the initiation and modulation of the inflammatory response in the eye. This study investigated the precise expression patterns and functionality of TLRs in human corneal epithelial cells (HCE) and in conjunctival fibroblasts (HCF). METHODS: The cell surface expression of TLRs 2-4, TLR7 and TLR9 in HCE and HCF was examined by flow cytometry with or without stimulation with lipopolysaccharide (LPS) or polyinosinic:polycytidylic acid (poly I:C). The mRNA expression of the TLRs was determined by real-time PCR. The protein content levels of interleukin (IL)-6, IL-8, IL-1ß and tumor necrosis factor-α (TNF-α) were measured in HCE and HCF using multiplex fluorescent bead immunoassay (FBI). RESULTS: The surface expression of TLR3 and TLR4 was detected on both HCE and HCF. Following incubation with LPS, the percentage of HCE cells staining for TLR4 decreased from 10.18% to 0.62% (P < 0.001). Incubation with poly I:C lowered the percentage of HCE cells positive for TLR3 from 10.44% to 2.84% (P < 0.001). The mRNA expression of TLRs2, 4, 7 and 9 was detected in HCE only. Activation of HCE with LPS complex elicited protein secretion up to 4.51 ± 0.85-fold higher levels of IL-6 (P < 0.05), 2.5 ± 0.36-fold IL-8 (P > 0.05), 4.35 ± 1.12-fold IL-1ß (P > 0.05) and 29.35 ± 2.3-fold TNFα (P < 0.05) compared to cells incubated in medium. CONCLUSIONS: HCF and HCE both express TLRs that respond to specific ligands by increasing cytokine expression. Following activation, the surface expression of TLR3 and TLR4 on HCE is decreased, thus creating a negative feedback loop, mitigating the effect of TLR activation.

Congenital cytomegalovirus infection and Wiskott-Aldrich syndrome successfully treated with unrelated cord blood transplantation.

We report a successful umbilical cord blood transplantation (UCBT) in an 8-month male with Wiskott-Aldrich syndrome (WAS) and congenital cytomegalovirus (CMV) infection. The child presented at 3 months of age with symptomatic thrombocytopenia and CMV infection. Despite appropriate antiviral treatment no rise in the platelet count was observed. Genetic analysis confirmed the diagnosis of WAS. The clinical course was complicated by severe CMV retinitis with bilateral retinal hemorrhages and renal vasculitis. He underwent unrelated UCBT resulting in a rapid resolution of autoimmunity and thrombocytopenia.

Identification of three novel plasminogen (PLG) gene mutations in a series of 23 patients with low PLG activity.

Inherited severe hypoplasminogenaemia is a multisystemic disorder leading to deficient extravascular fibrinolysis. As a clinical consequence wound healing capacity of mucous membranes is markedly impaired leading to ligneous conjunctivitis and several other manifestations. Here we report the molecular genetic and clinical findings on 23 new cases with severe hypoplasminogenaemia. Homozygous or compound-heterozygous mutations in the plasminogen (PLG) gene were found in 16 of 23 patients (70%), three of which were novel mutations reported here for the first time (C166Y, Y264S, IVS10-7T/G). Compared to 79 previously published cases, clinical manifestations of the current group of patients showed higher percentages of ligneous periodontitis, congenital hydrocephalus, and involvement of the female genital tract. In contrast, involvement of the gastrointestinal or urogenital tract was not observed in any of the cases. Patients originated to a large extent (61%) from Turkey and the Middle East, and showed a comparably frequent occurrence of consanguinity of affected families and a greater female to male ratio than was derived from previous reports in the literature. Individual treatment of ligneous conjunctivitis included topical plasminogen or heparin eye drops, topical or systemic fresh frozen plasma, and surgical removal of ligneous pseudomembranes, mostly with modest or transient efficacy. In conclusion, the present study underscores the broad range of clinical manifestations in PLG-deficient patients with a trend to regional differences. Transmission of genetic and clinical data to the recently established Plasminogen Deficiency Registry should help to determine the prevalence of the disease and to develop more efficient treatment strategies.

Strabismus surgery outcome among children and young adults with Down syndrome.

PURPOSE: To evaluate postoperative alignment after strabismus surgery in children with Down syndrome. METHODS: A retrospective analysis of 15 consecutive cases of children with Down syndrome who underwent surgery for strabismus between 1990 and 2008. Follow-up was at least 6 months (range, 0.5-16 years). RESULTS: All children underwent surgery for esotropia. The mean preoperative angle of deviation was 37.6Delta. Of the 15 children, 14 underwent surgical procedure for strabismus according to standard surgical tables. Surgical success (within 10Delta of orthophoria) was achieved in 12 of 14 children (85.7%). The remaining 2 children (14.3%) had residual esotropia. CONCLUSIONS: Good surgical motor outcomes were achieved in children with Down syndrome after strabismus surgery following standard surgical tables. The tendency toward overcorrection reported in children with central nervous system disorders was not observed in our study. We suggest use of the same surgical calculations as used in children with normal development when treating children with Down syndrome and esotropia.

[Association between iris color and ciliary body pigmentation: possible implications for cyclophotoablation treatment].

BACKGROUND: Cyclophotoablation for glaucoma treatment is dependent on the amount of laser energy absorbed by the ciliary body and related to the degree of its pigmentation. Iris color may be assessed by observing the eye, but it is unknown whether it correlates with ciliary body pigmentation. AIM: We evaluated whether ciliary pigmentation correlates with iris color. METHODS: The pigmented epithelium of the ciliary processes of 31 enucleated eyes was qualitatively scored for six histological parameters and correlated with iris color. RESULTS: The dark iris group (n = 19) had significantly increased histological parameters of pigmentation such as aggregation of melanosomes, compared to the light iris group (n = 12) (p < 0.01). CONCLUSION: Iris color correlates with ciliary pigmentation and may serve as one of the factors determining laser power needed for cyclophotoablation.

Iontophoretic treatment of experimental pseudomonas keratitis in rabbit eyes using gentamicin-loaded hydrogels.

PURPOSE: To evaluate the efficacy of iontophoresis using a hydrogel probe containing gentamicin for the treatment of Pseudomonas keratitis in the rabbit cornea. METHODS: Five groups (Groups 1-5) of 8 rabbits each were infected by injecting Pseudomonas aeruginosa into their corneas. Three dosings of corneal iontophoresis were performed, at intervals of 3.5 hours, using soft disposable gentamicin-loaded hydroxyethyl methacrylate hydrogel discs mounted on a portable iontophoretic device. Groups 1 and 2 were treated with corneal iontophoresis for 60 seconds and a current of 0.5 and 0.2 mA. Groups 3 and 4 were treated with hydrogel loaded with 0.9% NaCl solution, using a current of 0.2 mA and mock iontophoresis. Group 5 was treated with eye drops of 1.4% gentamicin every hour for 8 hours. One and a half hours after the last treatment, the animals were killed, and the corneas were excised and cultured for P. aeruginosa count after 24-hour incubation. RESULTS: After iontophoretic treatment of gentamicin with a current of 0.5 mA (Group 1), the logarithmic value of Pseudomonas colony-forming units (CFUs) was 2.96 +/- 0.45. After lower current iontophoretic treatment (Group 2), the logarithmic Pseudomonas count was 5.25 +/- 0.54 CFUs. At the control groups (Groups 3-5), the Pseudomonas counts were found to be much higher, 7.62 +/- 0.28, 7.22 +/- 0.29, and 6.29 +/- 0.45 CFUs, respectively. CONCLUSION: A short iontophoretic treatment using gentamicin-loaded hydrogels has potential clinical value in treating corneal infections.

Expression and activation of STAT3 in ischemia-induced retinopathy.

PURPOSE: Signal transducer and activator of transcription protein-3 (STAT3) is a transcription factor that participates in many biological processes, including tumor angiogenesis. The expression and activation of Stat3 in the mouse model of ischemia-induced retinal neovascularization was investigated to evaluate the possible role of STAT3 in retinal vascular disease. METHODS: Retinal neovascularization was induced in mice pups by exposure to hyperoxia. Gene microarrays were used to identify genes whose expression in the retina is altered at postnatal day (P)12 and P18. The relative levels of Stat3 mRNA were determined by semiquantitative RT-PCR. Stat3 protein levels and the levels of the activated form of Stat3 (pStat3) at P12, P15, P18, and P22 were determined by immunoblot analysis. Stat3 and pStat3 were demonstrated by immunofluorescence in retinal sections at P12, P15, and P18. RESULTS: In a series of microarray experiments, increased Stat3 mRNA levels in the retina were detected at P18. This result was validated by RT-PCR and demonstrated that Stat3 and pStat3 protein levels also increase during the development of neovascularization. Stat3 partially colocalized with blood vessels at the peak of neovascularization. pStat3 colocalized completely with blood vessels in both experimental samples and age-matched controls. pStat3 staining increased notably in the neovascular vessels at P15 and P18 and was more strongly associated with the epiretinal vessels than with inner retinal vessels. It was not detected in larger blood vessels, such as those of the optic nerve. CONCLUSIONS: The level of Stat3 expression increased, and pStat3 was observed in association with retinal neovascularization. Activated Stat3 was preferentially localized to neovascular retinal vessels. These data suggest that STAT3 may have a role in proliferative retinopathy.

Forty years of changing indications in penetrating keratoplasty in Israel.

PURPOSE: To examine the leading indications for keratoplasty and identify the changing trends in the past 40 years in Israel. METHODS: Pathology reports of all penetrating keratoplasties (PKPs) performed at Hadassah-Hebrew University Hospital from 1961 to 2000 were reviewed. We evaluated the indications for keratoplasty in each decade between the years 1961 and 2000. RESULTS: During the 40-year period, a total of 1681 PKPs were performed. Keratoconus (n = 478, 28.4%) was the most common indication, followed by graft failure (n = 226, 13.4%), pseudophakic corneal edema (PCE) (n = 142, 8.4%), herpetic infections (n = 125, 7.4%), nonherpetic infections (n = 114, 6.8%), scarring (n = 113, 6.7%), and trauma (n = 110, 6.5%). The 7 groups account for approximately 77.5% of all keratoplasties performed. Ocular infections were the most common indications before 1970 and have been declining ever since. Keratoconus became the leading indication in the past 30 years. In the past decade, of 663 keratoplasties, keratoconus was the most common indication (56, 38.6%) followed by graft failures/rejections and PCE (the second most common indication between the years 1981 and 1990). CONCLUSIONS: Keratoconus was the leading indication for keratoplasty in our series. There was a decreasing trend in PK for ocular herpetic infections during the decades. The rate of PCE decreased while failed graft became the second most common indication for PKP during the past decade.

Iontophoresis-gentamicin delivery into the rabbit cornea, using a hydrogel delivery probe.

PURPOSE: To evaluate the efficacy of penetration of gentamicin into the cornea of rabbits using iontophoresis with a hydrogel-gentamicin containing probe. METHODS: Eight of 10 groups (groups 3-10) of 6 rabbits (one eye per rabbit), underwent corneal iontophoresis using soft stable hydroxyethyl methacrylate hydrogel discs (80% water content) loaded with gentamicin sulphate which were mounted on an iontophoresis probe. The studied current intensities were 0, 0.1, 0.3 and 0.6 mAmp, and the durations of iontophoresis were 10 and 60 sec. Two control groups received 1.4% topical drops of gentamicin every 5 min for 1 hr (group 1) or sub-conjunctival injection of 10 mg gentamicin (group 2). Following sacrifice, aqueous humour was taken, corneas were excised, and gentamicin concentration was determined in aqueous humour and cornea samples. RESULTS: Post-iontophoresis, the concentration of gentamicin in the corneas ranged from high (88.60 +/- 38.64 microg ml(-1)) to very low (0.10 +/- 0.89 microg ml(-1)). Both the control groups and those rabbits treated with current intensity of 0.1 mAmp or greater obtained therapeutic gentamicin levels in the corneas. Use of iontophoresis for 60 sec or current intensity greater than 0.1 mAmp obtained corneal gentamicin levels not different from sub-conjunctival injection. Application of current intensity of 0.1 mAmp or greater gave corneal gentamicin concentrations comparable to topical application of the drug, except when 0.6 mAmp were used for 60 sec (p = 0.05). Increasing current intensity or duration of iontophoresis significantly increased (p = 0.001 for both) gentamicin penetration into the cornea. Current intensity had more influence (Beta2 = 0.40) than duration (Beta2 = 0.13) on drug penetration. A significant interaction was found between the duration of iontophoresis and the current intensity. Very small or no concentrations of the drug were discovered in the anterior chambers of rabbits. CONCLUSIONS: Iontophoresis using hydrogel-gentamicin probe may deliver therapeutic concentrations of gentamicin into the cornea.