Evaluation of choroidal thickness and choroidal vascularity index in patients with Crimean-Congo hemorrhagic fever.

PURPOSE: This study aimed to compare choroidal thickness parameters between patients diagnosed with Crimean-Congo hemorrhagic fever (CCHF) and healthy individuals using spectral domain optical coherence tomography. METHODS: The right eyes of 27 individuals diagnosed with CCHF and 27 healthy subjects were included in this study. CCHF cases were assessed based on a history of tick bites and hospitalization. Choroidal thickness was measured using enhanced depth imaging optical coherence tomography. Measurements of choroidal thickness were taken at 5 different points, including the subfoveal quadrant and the fovea up to 2000 µm with 1000 µm intervals in the temporal and nasal quadrants. Choroidal vascular index (CVI) was calculated as the ratio of luminal area (LA) to total choroidal area (TCA) at the macula's total area and at 1500 µm from the center (CVI and CVI1500). RESULTS: Choroidal thickness in the CCHF group was found to be thicker in each quadrant compared to the control group, with the subfoveal and nasal quadrants showing significantly greater thickness. TCA, stromal area, and LA were significantly higher in the CCHF group, while no significant difference was observed in CVI and CVI1500. CONCLUSION: The findings of this study suggest that CCHF disease may have an impact on the choroidal structure.

A safe and successful capsulorhexis technique for the intumescent cataracts; modified two-stage continuous curvilinear capsulorhexis.

BACKGROUND: Capsulorhexis is the most important step in intumescent cataract due to the high risk of radial extension of the capsular tear during the cataract surgery. The aim of this study is to present modified the two-stage capsulorhexis technique for intumescent cataract. MATERIALS AND METHODS: The two-stage capsulorhexis technique was used in this study. A small size capsulorhexis approximately 1.5-2 mm diameter was created in the first stage. Liquefied cortex was aspirated with a 25 G cannula to equalize anterior chamber pressure and intracapsular pressure after the small size capsulorhexis. In the second stage, a 5-6 mm capsulorhexis size was performed for a safe phacoemulsification. RESULTS: A total of 73 consecutive patients with intumescent cataract were evaluated in this study. There were 39 male cases and 34 female cases. Mean age was 66 years ± 8 (between 53 and 84 years). A well centered complete continuous curvilinear capsulorhexis approximately 5-6 mm size was achieved in 72 of 73 cases (98.6%). Peripheral extension of capsulorhexis occurred in one eye during the second stage capsulorhexis. In this case, the capsule was cut with Vannas scissors and the capsulorhexis was completed. The rest of surgery was continued with a standard procedure and in-the-bag IOL implantation was done. CONCLUSIONS: This technique facilitates the creation of a safe capsulorhexis compared to the one-stage capsulorhexis technique. Surgeons may consider this technique to perform a safe phacoemulsification in the intumescent cataracts.

Choroidal thickness changes in post-COVID-19 cases.

PURPOSE: The current study aimed to evaluate the effects of the coronavirus disease 2019 (COVID-19) on choroidal thickness using enhanced depth imaging optical coherence tomography. METHODS: This study evaluated the right eyes from 41 post-COVID-19 cases (Group 1) and 41 healthy subjects (Group 2). Choroidal thickness was measured using enhanced depth imaging optical coherence tomography. Post-COVID-19 cases were evaluated within 1 month after a diagnosis of COVID-19. Two experienced ophthalmologists measured the choroidal thickness at the subfovea, temporal, and nasal quadrants at 500-µm intervals up to 1500 µm from the fovea at seven different points. Moreover, central macular thickness and ganglion cell layer thickness were measured via OCT, after which both two groups were compared. RESULTS: Group 1 showed a significantly thicker choroid compared to Group 2 at the subfovea, 500 µm temporal to the fovea, 500 and 1000 µm nasal to the fovea (p=0.011, p=0.043, p=0.009, and p=0.019, respectively). Although other areas measured were also thicker in Group 1, the difference was not significant (p>0.05). Moreover, no significant difference in the central macular thickness and ganglion cell layer thickness were observed between the groups (p>0.05). CONCLUSION: Choroidal thickness was increased in post-COVID-19 patients, which might be related to inflammation associated with the pathogenesis of COVID-19.

Acute retinal pigment epitheliitis: a case presentation and literature review / Epitelite pigmentar retiniana aguda: apresentação de caso e revisão da literatura

ABSTRACT Acute retinal pigment epitheliitis (ARPE) is an idiopathic, self-limiting inflammatory retinal disorder that particularly affects healthy young individuals. The characteristic fundoscopic appearance of the acute retinal pigment epitheliitis includes a fine pigment stippling surrounded by a yellow-white hypopigmented halos in the macula. Although the exact pathogenesis of the disease remains unknown, some reports have suggested a relationship between a viral infection and acute retinal pigment epitheliitis. Acute retinal pigment epitheliitis is a rare disorder, and only single case reports or case series are found in the literature. The clinical and demographic characteristics of patients with this disease are not fully understood because of its rarity. In this study, we searched the literature to collect clinical and demographic features of the reported cases. We detail the characteristics of acute retinal pigment epitheliitis were pointed and discuss the pathogenesis of the disease.(AU)

RESUMO A epitelite pigmentar retiniana aguda (EPRA) é uma doença inflamatória idiopática e autolimitada da retina, que afeta especialmente indivíduos jovens e saudáveis. À fundoscopia, a aparência característica dessa entidade é de um pontilhado fino do pigmento, cercado de halos hiperpigmentados branco-amarelados na mácula. A patogênese exata da doença ainda é desconhecida, mas alguns relatos apontam uma relação entre epitelite pigmentar retiniana aguda e infecções virais. A epitelite pigmentar retiniana aguda é uma condição rara e na literatura há apenas relatos de casos individuais ou séries de casos. As características clínicas e demográficas da doença não são totalmente compreendidas, devido à sua raridade. Para este relato, foi feita uma busca na literatura para coletar os dados clínicos e demográficos dos casos relatados. Finalmente, são apontadas as características da epitelite pigmentar retiniana aguda e discute-se a patogênese da doença.(AU)

An Evaluation of the Relationship between Retinal Nerve Fiber Thickness, Cochlear Nerve Thickness, the Level of Tinnitus, and Hearing Loss in Unilateral Tinnitus Patients.

BACKGROUND: In this study, optic coherence tomography (OCT) examination was performed to check whether there was any interaction between ophthalmic axonal structures in unilateral tinnitus patients, and the relationship between optic nerve thickness and cochlear nerve thickness was evaluated. OBJECTIVE: The aim of the study was to evaluate the relatioship between hearing loss, tinnitus, and nerve thicknesses. STUDY DESIGN: Prospective study. SETTING: Tertiary referral university hospital. PATIENTS: The study included 88 patients with unilateral tinnitus, for which no organic cause could be found in physical examination, psychiatric evaluation, or with imaging methods. Study groups were formed of the tinnitus side and control groups were formed of the healthy side as follows: Group 1 (Non-tinnitus side normal hearing values - n = 30), Group 2 (non-tinnitus side minimal hearing loss - n = 27), Group 3 (non-tinnitus side moderate hearing loss - n = 31), Group 4 (tinnitus side normal hearing values - n = 25), Group 5 (tinnitus side minimal hearing loss - n = 25), and Group 6 (tinnitus side moderate hearing loss - n = 38). INTERVENTION: Retinal nerve fiber layer (RNFL) thickness was evaluated with OCT, and the cochlear nerve cross-sectional area was evaluated with MRI. MAIN OUTCOME MEASURES: RNFL measurements were taken with OCT from the subfoveal area (RNFL-SF) and 1.5 mm temporal to the fovea (RNFL-T µm) and nasal (RNFL-N µm) sectors. On MRI, 3 measurements were taken along the nerve from the cerebellopontine angle as far as the internal auditory canal, and the mean value of these 3 measurements was calculated. RESULTS: When the groups were evaluated in respect of cochlear nerve thickness, a significant difference was seen between Group 1 and both the groups with hearing loss and the tinnitus groups. In the subgroup analysis, a statistically significant difference was determined between Group 1 and Groups 3, 4, 5, and 6 (p = 0.013, p = 0.003, p < 0.001, and p < 0.001, respectively). When the groups were evaluated in respect of the RNFL-SF (µm), RNFL-T (µm), and RNFL-N (µm) values, the differences were determined to be statistically significant (p < 0.001 for all). In the correlation analysis, a negative correlation was determined between hearing loss and cochlear nerve diameter (r: -0.184, p = 0.014), and RNFL-N (r: -0.272, p < 0.001) and between tinnitus and cochlear nerve diameter (r: -0.536, p < 0.001), and RNFL-T (r: -0.222, p < 0.009). CONCLUSION: The study results clearly showed a relationship between cochlear nerve fiber thickness and hearing loss and the severity of tinnitus in cases with unilateral tinnitus and that there could be neurodegenerative factors in the disease etiology. A similar relationship seen with the RNFL supports the study hypothesis.

Acute retinal pigment epitheliitis: a case presentation and literature review.

Acute retinal pigment epitheliitis (ARPE) is an idiopathic, self-limiting inflammatory retinal disorder that particularly affects healthy young individuals. The characteristic fundoscopic appearance of the acute retinal pigment epitheliitis includes a fine pigment stippling surrounded by a yellow-white hypopigmented halos in the macula. Although the exact pathogenesis of the disease remains unknown, some reports have suggested a relationship between a viral infection and acute retinal pigment epitheliitis. Acute retinal pigment epitheliitis is a rare disorder, and only single case reports or case series are found in the literature. The clinical and demographic characteristics of patients with this disease are not fully understood because of its rarity. In this study, we searched the literature to collect clinical and demographic features of the reported cases. We detail the characteristics of acute retinal pigment epitheliitis were pointed and discuss the pathogenesis of the disease.

Repeatability, Reproducibility and Agreement of Central Corneal Thickness Measurements by Two Noncontact Pachymetry Devices.

This study was designed to assess the repeatability, reproducibility, and agreement of Noncontact Pachymetry (NPC) (Topcan TRK-2P) and the non-contact optical low coherence reflectometer (Lenstar LS 900) devices for measuring Central Corneal Thickness (CCT) of healthy corneas. A total of 82 healthy volunteers were evaluated. The first observer used both the TopconTRK-2P and Lenstar 900 devices while the second observer only used the TopconTRK-2P for the measurements. The measurements with either device were repeated three times for each patient, consecutively. The central corneal thickness measurements with the Topcon TRK-2P revealed mean ± Standard Deviation (SD) values of 553.1 ± 36.1 micrometer (µm) for the first observer and 552.3 ± 35.9µm for the second observer and the mean ± SD of CCT was 537.3 ± 34.8µm with the Lenstar 900. The difference between the CCT measurements of the observers using the Topcon TRK-2P (P = 0.142) was insignificant. However, significantly lower measurements were found with the Lenstar 900 compared with the Topcon TRK-2P (P ˂ 0.001). The central corneal thickness measurements obtained by the Topcon TRK-2P were found to have high repeatability for both observers with a lower SD, less than 1% Coefficient of Variation (CV) and higher than 0.99 Intra-Class Correlation Coefficient (ICC) (Observer 1: 3.77 SD, 0.68 CV and 0.995 ICC; the second observer: 3.58 SD, 0.65 CV and 0.995 ICC). There was an excellent inter-observer reproducibility between the two observers for Topcon TRK-2P with 2.71 SD, 0.49 CV, and 0.994 ICC. The Bland-Altman plot showed high agreement between the two devices. These results suggest that the TopconTRK-2P is a reliable device for evaluating CCT in healthy corneas compared with Lenstar 900.

YKL-40 expression in pterygium: a potential role in the pathogenesis.

PURPOSE: The aim of the study was to evaluate whether YKL-40 (chitinase 3-like 1 protein) plays a role in pterygium pathogenesis. METHODS: We included 42 primary pterygium patients and 24 control subjects with normal bulbar conjunctiva in the study. The pterygium patients were classified into the atrophic, fleshy, and intermediate groups according to the Tan classification. We then surgically removed the primary nasal pterygium and normal bulbar conjunctiva from the patients and immunohistochemically investigated YKL-40 expression. RESULTS: YKL-40 expression was statistically significantly higher in the epithelial, endothelial, and stromal cells of the pterygium tissues than in the control tissues (P = 0.009, P = 0.003, P = 0.002, respectively). There was no significant correlation between the pterygium subgroups and YKL-40 expression (P > 0.05). CONCLUSIONS: We believe YKL-40 may play a significant role in pterygium pathogenesis.

The Effects of Uncomplicated Cataract Surgery on Retinal Layer Thickness.

PURPOSE: Our aim was to assess changes in the total retinal thickness (TRT), total retinal volume (TRV), and retinal layer thickness after uncomplicated cataract surgery. METHODS: A total of 32 eyes of 32 patients who had undergone uncomplicated phacoemulsification surgery and intraocular lens implantation in one eye were enrolled. Effective phacoemulsification time (EPT) and total energy (TE) were recorded. Thickness and TRV were measured using optical coherence tomography. Data were collected preoperatively and at postoperative day 1, 7, 30, 90, and 180. RESULTS: The study results showed a decrease in TRT, TRV, and most retinal layer thicknesses at the first postoperative day visit and then increasing at week 1, and months 1 and 3, and then relatively decreasing at month 6 although not returning to preoperative levels. The least affected layers were the retinal pigment epithelium and outer plexiform layer. There was a positive correlation between EPT and TE and ganglion cell layer in a 1 mm circle and inner nuclear layer in a 1-3 mm circle (p < 0.05). CONCLUSION: The results suggest that long-term follow-up of more than 6 months is necessary after cataract surgery to see whether total retinal and segmental values return to preoperative levels. This study was registered with Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12618000763246.

Endocan Overexpression in Pterygium.

PURPOSE: The aim of this study was to evaluate the possible role of endocan in the pathogenesis of pterygium. METHODS: The study was conducted on 33 patients with primary pterygium and 20 control subjects with normal bulbar conjunctiva. Patients with pterygium were graded into 3 groups as atrophic, fleshy, and intermediate, according to the Tan classification. Primary nasal pterygia and normal bulbar conjunctivas were surgically removed. Endocan expression was immunohistochemically investigated. RESULTS: Endocan expression in epithelial and endothelial cells was statistically significantly higher in pterygium tissues than control tissues (P = 0.001). No significant correlation was observed between pterygium classification groups and endocan expression in both epithelial and endothelial cells (P > 0.05). CONCLUSIONS: The results suggest that endocan may have a role in the pathogenesis of pterygium.

Choroidal thickness in psoriasis.

Our aim was to compare the choroidal thickness in psoriasis patients and age- and gender-matched healthy volunteers. A total of 38 psoriasis cases and 38 age- and gender-matched controls were evaluated. The left eye was evaluated in all subjects. The choroidal thicknesses were measured at the subfovea and horizontally across the fovea at 500-µm intervals using enhanced depth imaging spectral domain optical coherence tomography. The points of measurement were 1500 µm temporal and nasal to the fovea. Choroidal thicknesses in psoriasis patients were thicker than those in the controls, but these differences were not statistically significant (P > 0.05). A positive correlation was present between the duration of disease and choroidal thickness at certain measurement points, but there was no significant correlation between the Psoriasis Area and Severity Index score and choroidal thickness. There was no significant difference between psoriasis patients and healthy controls in terms of choroidal thickness. However, choroidal thickness was associated with disease duration.

Evaluation of Serum Superoxide Dismutase Activity, Malondialdehyde, and Zinc and Copper Levels in Patients With Keratoconus.

PURPOSE: The aim of this study was to evaluate the relationship between antioxidant superoxide dismutase (SOD) enzyme activity, malondialdehyde (MDA) as a lipid peroxidation marker, and some trace elements such as zinc (Zn) and copper (Cu) levels in patients with keratoconus. METHODS: A total of 58 patients with keratoconus and 53 control subjects with similar age and sex were evaluated in this study. The modified Krumeich keratoconus classification was used to divide the patients into 4 stages. Serum SOD activity, MDA, and zinc and copper levels were compared between the patient and control groups. RESULTS: The median serum SOD activity, MDA, and Zn and Cu levels were 27.2 (42.4-13.7) U/mL, 10.2 (11.9-8.5) nmol/mL, 87.9 (104.6-76.5) µmol/L, and 103.2 (117.9-90.3) µmol/L in the keratoconus group and 26.2 (32.5-14.4) U/mL, 8.8 (11.4-7.1) nmol/mL, 100.5 (121.1-81.8) µmol/L, and 98.4 (120.3-83.4) µmol/L in the control group, respectively. There was a statistically significant difference between the MDA and Zn levels of the keratoconus group and control subjects but not between the respective SOD activities or Cu levels (P = 0.016, P = 0.031, P = 0.440, and P = 0.376, respectively). We found no significant difference between the keratoconus group stages for serum SOD activity, serum MDA, and Zn and Cu levels (P > 0.05), and there was also no significant correlation between the keratoconus group stages and serum SOD activity, serum MDA, and Zn and Cu levels (P > 0.05). CONCLUSIONS: There is imbalance in the systemic oxidant/antioxidant status where Zn deficiency also plays a role in patients with keratoconus.

Systemic Prolidase Activity and Oxidative Stress in Keratoconus.

AIM: Our aim was to evaluate the serum prolidase activity, total antioxidant capacity (TAC) and total oxidant status (TOS) in patients with keratoconus. MATERIAL AND METHOD: A total 69 keratoconus patients and 72 control subjects with similar age and gender were evaluated within the scope of this study. The keratoconus group was divided into four stages with the modified Krumeich classification. Serum prolidase activity, TAC and TOS were measured and compared between the patient and control groups. RESULTS: The median serum prolidase enzyme activity value was 528.3 (684.1-416.7) U/L in the keratoconus group and 606.2 (812.9-482.3) U/L in the control group. The difference between the groups was statistically significant (p = 0.027). The median TAC value was 1.24 (1.37-1.05) mmol/L in the keratoconus group and 1.29 (1.38-1.18) mmol/L in the control group. The median TOS value was 2 (4-1) µmol/L in the keratoconus group and 3 (4-2) µmol/L in the control group. There was no statistically significant difference between the two groups in terms of TAC or TOS (p = 0.113 and p = 0.366, respectively). There was a positive correlation between TAC and TOS in keratoconus group but not in the control group (r = 0.670, p = 0.001 and r = 0.141, p = 0.241, respectively). No significant relationship was seen between the keratoconus group stages and serum prolidase activity, TAS or TOS (p = 0.894, p = 0.155 and p = 0.381, respectively). CONCLUSION: In conclusion, a significant relationship was found between decreased serum prolidase activity and keratoconus but there was no significant relationship between keratoconus and serum TAC or TOS.

The prevalence of exfoliation syndrome in Turkey.

PURPOSE: To investigate the prevalence of the exfoliation syndrome and its relationship with ocular and cardiovascular diseases in the Central Anatolia region of Turkey. METHODS: This cross-sectional and population-based study was conducted at the Sivas Province among the population aged 40 years and over. The diagnosis of XFS was made when exfoliative material was found on the anterior lens capsule or iris on slit-lamp examination. The subjects were divided into an XFS group and a non-XFS group according to the presence of exfoliative material, and the groups were compared for the presence of glaucoma, cataract, age-related macular degeneration, phacodonesis, hypertension, diabetes mellitus, coronary artery disease, smoking and alcohol-use frequency. RESULTS: XFS was present in 63 subjects consisting of 42 males (8.0%) and 21 females (3.6%) for an overall rate of 5.7% (95% CI: 0.054-0.060). Once we adjusted the values for age, we found a statistically significant relationship of increased age and male gender with the presence of XFS (p = 0.001, p = 0.027, respectively). The relationship between XFS and glaucoma, cataract and phacodonesis was found to be statistically significant (p = 0.001). No relationship was found between exfoliation syndrome and hypertension, diabetes mellitus and coronary artery disease. CONCLUSION: The prevalence of exfoliation syndrome was 5.7% in this population-based study. There was a statistically significant relationship between XFS and advancing age and male gender.

The frequency of exfoliation syndrome in the central anatolia region of Turkey.

Aim. The aim of this study was to investigate the frequency of exfoliation syndrome in the Central Anatolia region of Turkey and to evaluate its relationship with cardiovascular and ocular diseases. Methods. Patients over the age of 45 years who presented to the clinic were included in the study. All cases underwent a comprehensive ophthalmology examination. Exfoliation syndrome was diagnosed with the presence of exfoliative material on the lens anterior capsule or iris on slit lamp examination. The patients were divided into two groups as the exfoliation syndrome group and nonexfoliation syndrome group according to the presence of exfoliative material. Results. Exfoliative material was found in one or both eyes of 212 of the 2103 patients (10.1%) evaluated within the scope of the study. A significant relationship was found between exfoliation syndrome and increasing age and male gender. A significant relationship was found between exfoliation syndrome and glaucoma, cataracts, age-related macular degeneration, and phacodonesis. While no relationship was found between exfoliation syndrome and hypertension or diabetes mellitus, a significant relationship was found with coronary artery disease. Conclusion. The unilateral or bilateral exfoliation syndrome frequency was 10.1% in this hospital-based study. A statistically significant relationship was found between exfoliation syndrome and advancing age, gender, and coronary artery disease.

The frequency of pseudoexfoliation syndrome in the middle Black Sea region of Turkey.

PURPOSE: To assess the frequency of pseudoexfoliation syndrome (PEX) and evaluate its association with specific ocular diseases in patients attending the Department of Ophthalmology at Gaziosmanpasa University Hospital. METHODS: A prospective study was conducted at the Gaziosmanpasa University Hospital between December 2007 and December 2008. A total of 831 subjects aged 45 or above attending the general ophthalmic clinics were recruited for this study. Each patient underwent complete ophthalmic assessment, including ocular history, visual acuity testing, slit-lamp examination, applanation tonometry, gonioscopy, and fundus examination. RESULTS: Of the 831 subjects, 12.2% had PEX. Pseudoexfoliation was bilateral in 74.2% of cases, significantly associated with cataract, glaucoma, age-related macular degeneration (AMD), and phacodenesis. Of the patients with PEX, 43.6% had cataract, 6.9% had glaucoma, 7.9% had AMD, and 0.9% had phacodenesis. In addition, 9.8% had cataract + glaucoma, 13.7% had cataract + phacodenesis, and 17.8% had all of them. The prevalence of PEX had a tendency to increase with age but had no sex predilection. CONCLUSIONS: The study findings enhance our knowledge of PEX in Anatolia, particularly in the Middle Black Sea region.

Increased central corneal thickness in children with cerebral palsy.

PURPOSE: To evaluate central corneal thickness (CCT) values in children with cerebral palsy (CP). METHODS: Sixty-seven children with CP and 58 healthy control children (125 children total) were enrolled into the study. The CCT value was measured by ultrasound pachymetry. The consecutive measurements were taken from the center of the cornea of each eye. RESULTS: In the CP group, the mean CCT value was 568.46 +/- 31.94 microm in the right eye and 568.01 +/- 32.50 microm in the left eye. In the control group, the mean CCT value was 549.53 +/- 26.16 microm in the right eye and 549.62 +/- 27.58 microm in the left eye. The CCT value was significantly higher in the CP group than in the control group for both eyes (P < 0.001). There was no statistically significant difference between the right and left eyes of children with CP and intellectual disability (ID) and those with CP and no ID (P = 0.344 and 0.076, respectively). CONCLUSIONS: Children with CP had an increased CCT compared with healthy control subjects. There was however no significant difference in CCT values between the children with and without ID in our CP group.

Comparison of dose-related ocular side effects during systemic isotretinoin administration.

PURPOSE: To compare the effects of high- (Group 1) and low-dose (Group 2) isotretinoin treatments for acne vulgaris on lacrimal functions and other ocular complications. METHODS: Twenty-six patients receiving high-dose (>0.5 mg/kg per day) systemic isotretinoin treatment and 25 patients treated with low-dose systemic isotretinoin (<0.5 mg/kg per day) underwent complete ophthalmologic assessment of both eyes before treatment, at days 45 and 90 of treatment, and 1 month after the completion of treatment, together with a microbiologic evaluation of conjunctival flora, tear film break-up time (BUT), and anesthetized Schirmer test of the right eye of each patient. RESULTS: When the results of the anesthetized Schirmer test for Groups 1 and 2 were compared (pretreatment, days 45 and 90 of treatment, and 1 month after treatment), there was no statistically significant difference between the groups (p > 0.05). Although BUT did not differ significantly between the two groups before treatment (p >0.05), there was a statistically significant decrease in BUT in Group 1 when compared with Group 2 at days 45 and 90 of treatment (p <0.05). One month after the completion of treatment, there was no difference in BUT between the two groups (p >0.05). No difference in Staphylococcus aureus colonization was detected between the two groups at days 45 and 90 of treatment (p >0.05). CONCLUSIONS: During systemic isotretinoin treatment, eye dryness was related to the dose used, at least during the period of treatment. Conversely, the rate of conjunctival S aureus colonization was unrelated to the dose of isotretinoin.