Methodology and Rationale for Ophthalmic Examinations in the Seventh and Eighth Korea National Health and Nutrition Examination Surveys (2017–2021)

This report provides a detailed description of the methodology for ophthalmic examinations according to the Korea National Health and Nutrition Examination Survey (KNHANES) VII and VIII (from 2017 to 2021). The KNHANES is a nationwide survey which has been performed since 1998 in representatives of whole Korean population. During the KNHANES VII and VIII, in addition to the ophthalmic questionnaire, intraocular pressure measurement, visual field test, auto refractometry, axial length and optical coherence tomography measurements were included. This new survey will provide not only provide normative and pathologic ophthalmic data including intraocular pressure, refractive error, axial length, visual field and precise measurement of anterior segment, macula and optic nerve with optical coherence tomography, but also a more accurate diagnosis for major adult blindness diseases, including age-related macular degeneration, diabetic retinopathy, glaucoma, and other ocular diseases, for the national Korean population.

Effects of Trabecular Meshwork Width and Schlemm’s Canal Area on Intraocular Pressure Reduction in Glaucoma Patients

Purpose@#To evaluate the effects of baseline trabecular meshwork (TM) and Schlemm’s canal (SC) microstructures on intraocular pressure (IOP) reduction amount in treatment-naïve patients with primary open-angle glaucoma (POAG). @*Methods@#A total 69 eyes of POAG patients who had not been treated with IOP-lowering agent were enrolled in this retrospective study. The patients had been prescribed topical IOP-lowering agent and used it for 1 year. The morphologic features of the TM and SC were collected using anterior segment module of spectral-domain optical coherence tomography with enhanced depth imaging at baseline. Images of the nasal and temporal corneoscleral limbus were obtained with serial horizontal enhanced depth imaging B-scans and TM width and SC area were measured in each scan. We investigated the effects of baseline TM and SC microstructures on IOP reduction amount. @*Results@#The baseline IOP of 69 glaucomatous eyes was 17.9 ± 3.8 mmHg, and the mean amount of IOP reduction was 3.5 ± 2.1 mmHg after 1 year. Mean TM widths of nasal and temporal sector were 470.33 ± 80.05 and 479.74 ± 79.59 μm, respectively. SC area was measured as 4,818.50 ± 1,464.28, 4,604.23 ± 1,567.73 μm2 at nasal sector and temporal sector, respectively. The correlation analysis revealed a positive correlation between SC area and average amount of IOP reduction, indicating that the larger baseline SC area, the greater the IOP drop with topical IOP-lowering agents. However, no correlation was found between TM width and IOP lowering amount in patients with POAG. @*Conclusions@#The baseline SC area showed positive correlation with the IOP reduction amount in patients with POAG. This finding suggests that the SC area can be a clinical parameter to predict the IOP reduction amount before using IOP-lowering agents in POAG patient.

Methodology and Rationale for Ophthalmic Examinations in the Seventh and Eighth Korea National Health and Nutrition Examination Surveys (2017–2021)

This report provides a detailed description of the methodology for ophthalmic examinations according to the Korea National Health and Nutrition Examination Survey (KNHANES) VII and VIII (from 2017 to 2021). The KNHANES is a nationwide survey which has been performed since 1998 in representatives of whole Korean population. During the KNHANES VII and VIII, in addition to the ophthalmic questionnaire, intraocular pressure measurement, visual field test, auto refractometry, axial length and optical coherence tomography measurements were included. This new survey will provide not only provide normative and pathologic ophthalmic data including intraocular pressure, refractive error, axial length, visual field and precise measurement of anterior segment, macula and optic nerve with optical coherence tomography, but also a more accurate diagnosis for major adult blindness diseases, including age-related macular degeneration, diabetic retinopathy, glaucoma, and other ocular diseases, for the national Korean population.

Effects of Trabecular Meshwork Width and Schlemm’s Canal Area on Intraocular Pressure Reduction in Glaucoma Patients

Purpose@#To evaluate the effects of baseline trabecular meshwork (TM) and Schlemm’s canal (SC) microstructures on intraocular pressure (IOP) reduction amount in treatment-naïve patients with primary open-angle glaucoma (POAG). @*Methods@#A total 69 eyes of POAG patients who had not been treated with IOP-lowering agent were enrolled in this retrospective study. The patients had been prescribed topical IOP-lowering agent and used it for 1 year. The morphologic features of the TM and SC were collected using anterior segment module of spectral-domain optical coherence tomography with enhanced depth imaging at baseline. Images of the nasal and temporal corneoscleral limbus were obtained with serial horizontal enhanced depth imaging B-scans and TM width and SC area were measured in each scan. We investigated the effects of baseline TM and SC microstructures on IOP reduction amount. @*Results@#The baseline IOP of 69 glaucomatous eyes was 17.9 ± 3.8 mmHg, and the mean amount of IOP reduction was 3.5 ± 2.1 mmHg after 1 year. Mean TM widths of nasal and temporal sector were 470.33 ± 80.05 and 479.74 ± 79.59 μm, respectively. SC area was measured as 4,818.50 ± 1,464.28, 4,604.23 ± 1,567.73 μm2 at nasal sector and temporal sector, respectively. The correlation analysis revealed a positive correlation between SC area and average amount of IOP reduction, indicating that the larger baseline SC area, the greater the IOP drop with topical IOP-lowering agents. However, no correlation was found between TM width and IOP lowering amount in patients with POAG. @*Conclusions@#The baseline SC area showed positive correlation with the IOP reduction amount in patients with POAG. This finding suggests that the SC area can be a clinical parameter to predict the IOP reduction amount before using IOP-lowering agents in POAG patient.

Effect of Head Position and Tube Entry on Corneal Endothelial Cells in Patients with Glaucoma Drainage Implants: A Cross-sectional Study

Purpose@#To investigate the effect of head tilt on the tube position of the Ahmed glaucoma valve (AGV) implanted in patients with glaucoma and to assess how the head tilt-induced alterations of tube parameters and the level of tube entry influence corneal endothelial cell density (ECD). @*Methods@#A total of 29 eyes of 26 patients with AGV implantation were included. Tube-cornea distance, tube-cornea angle, and intracameral tube length were measured using anterior segment optical coherence tomography in three different head positions (neutral, 30° temporalward tilt, and 30° nasalward tilt). The tube entry was assessed using static gonioscopy. ECD was measured using specular microscopy before and after surgery. @*Results@#The mean tube-cornea distance, tube-cornea angle, and intracameral tube length (neutral: 0.87 ± 0.39 mm, 30.56 ± 5.89˚, and 3.10 ± 0.82 mm, respectively) decreased with head tilts (temporalward: 0.82 ± 0.39 mm, 29.27 ± 5.82˚, and 3.04 ± 0.82 mm, respectively; nasalward: 0.83 ± 0.40 mm, 29.61 ± 6.04˚, and 3.05 ± 0.81 mm, respectively; all p < 0.01). The multivariate analyses found age and the tube insertion level to be associated with postoperative changes in the central ECD (p = 0.039 and 0.013, respectively), and the postoperative follow-up period and tube insertion level to be associated with the difference between the inferonasal and superotemporal ECDs (p = 0.034 and 0.007, respectively). @*Conclusions@#Mild alterations of head positions induced changes in the intracameral tube positions of AGV implants; nevertheless, it did not significantly affect ECD loss. However, the eyes with tubes inserted anteriorly to Schwalbe’s line may be more susceptible to corneal ECD loss.

Effect of Head Position and Tube Entry on Corneal Endothelial Cells in Patients with Glaucoma Drainage Implants: A Cross-sectional Study

Purpose@#To investigate the effect of head tilt on the tube position of the Ahmed glaucoma valve (AGV) implanted in patients with glaucoma and to assess how the head tilt-induced alterations of tube parameters and the level of tube entry influence corneal endothelial cell density (ECD). @*Methods@#A total of 29 eyes of 26 patients with AGV implantation were included. Tube-cornea distance, tube-cornea angle, and intracameral tube length were measured using anterior segment optical coherence tomography in three different head positions (neutral, 30° temporalward tilt, and 30° nasalward tilt). The tube entry was assessed using static gonioscopy. ECD was measured using specular microscopy before and after surgery. @*Results@#The mean tube-cornea distance, tube-cornea angle, and intracameral tube length (neutral: 0.87 ± 0.39 mm, 30.56 ± 5.89˚, and 3.10 ± 0.82 mm, respectively) decreased with head tilts (temporalward: 0.82 ± 0.39 mm, 29.27 ± 5.82˚, and 3.04 ± 0.82 mm, respectively; nasalward: 0.83 ± 0.40 mm, 29.61 ± 6.04˚, and 3.05 ± 0.81 mm, respectively; all p < 0.01). The multivariate analyses found age and the tube insertion level to be associated with postoperative changes in the central ECD (p = 0.039 and 0.013, respectively), and the postoperative follow-up period and tube insertion level to be associated with the difference between the inferonasal and superotemporal ECDs (p = 0.034 and 0.007, respectively). @*Conclusions@#Mild alterations of head positions induced changes in the intracameral tube positions of AGV implants; nevertheless, it did not significantly affect ECD loss. However, the eyes with tubes inserted anteriorly to Schwalbe’s line may be more susceptible to corneal ECD loss.

Adherence to Preservative-Free Dorzolamide/Timolol Fixed Combination Assessed by Counting the Unused Single-Dose Units

PURPOSE: To investigate the actual adherence to treatment with preservative-free dorzolamide-timolol fixed combination (DTFC) eyedrops of primary open-angle glaucoma (POAG) patients by counting the number of unused single-dose units of DTFC. METHODS: This study included 34 POAG patients newly prescribed with preservative-free DTFC eyedrops (formulated in single-dose units). The enrolled patients were asked to bring the unused DTFC units on their next visit after 2 weeks of treatment with DTFC. On their second visit, they were asked to complete a questionnaire regarding the self-reported adherence and the number of unused DTFC single-dose units was counted. The actual adherence (%) was calculated by dividing the expected number of used DTFC units by the actual number of used DTFC units. The correlation between the self-reported adherence and the measured adherence was assessed. RESULTS: Twenty-nine (93.5%) patients answered they adhered to the medication by more than 90% and 2 (6.5%) answered they instilled the eyedrops at 80-90% of the dosing schedule. However, after counting the unused DTFC single-dose units, 9 (29.0%) patients showed an actual adherence of <90%. Moreover, the actual adherence of 3 (9.7%) patients was <60%. Unexpectedly, 4 (12.9%) patients showed the actual adherence exceeding 100% (196%, 1 patient; 107-132%, 3 patients). CONCLUSIONS: We demonstrated a large difference between the self-reported and the actual adherence to treatment by counting the unused single-dose units of eyedrops. Preservative-free topical anti-glaucoma medications (formulated in single-dose units) provide clinicians an opportunity to assess the actual adherence of glaucoma patients by counting the unused units of eyedrops.

Characteristics of the Gray Optic Disc Crescent and Associated Factors

PURPOSE: To investigate the characteristics of the gray optic disc crescent and associated factors. METHODS: We retrospectively reviewed stereo fundus photographs of 590 glaucoma patients and 273 non-glaucoma patients. An experienced investigator evaluated the presence or absence of the gray crescent (a crescent-shaped, slate-gray pigmentation on the periphery of the neuroretinal rim) which is entirely inside the scleral crescent. Correlations with age, gender, refractive error, disc diameters, and the presence of glaucoma or peripapillary atrophy were also analyzed. RESULTS: Out of 863 patients, the gray crescent was observed in 166 patients and was found in 19.0% of glaucoma patients and 19.8% of non-glaucoma patients. The gray crescent was most often located temporally (30.1%) and most frequently occurred within only 1 quadrant (63.9%). The prevalence of the gray crescent was not correlated with refractive error (p = 0.61) or the occurrence of glaucomatous optic neuropathy (p = 0.25), but was significantly related to peripapillary atrophy (p < 0.001) and the horizontal diameter of the optic disc (p = 0.001). CONCLUSIONS: The gray optic disc crescent is a common finding within a glaucomatous or non-glaucomatous eye and factors significantly related to occurrence of the gray crescent include peripapillary atrophy and the horizontal diameter of the optic disc. Patients with gray crescent require special attention when the optic disc is examined.

Simplified Method to Measure the Peripapillary Choroidal Thickness Using Three-dimensional Optical Coherence Tomography

PURPOSE: To evaluate a simplified method to measure peripapillary choroidal thickness using commercially available, three-dimensional optical coherence tomography (3D-OCT). METHODS: 3D-OCT images of normal eyes were consecutively obtained from the 3D-OCT database of Korea University Medical Center On the peripapillary images for retinal nerve fiber layer (RNFL) analysis, choroidal thickness was measured by adjusting the segmentation line for the retinal pigment epithelium to the chorioscleral junction using the modification tool built into the 3D-OCT image viewer program. Variations of choroidal thickness at 12 sectors of the peripapillary area were evaluated. RESULTS: We were able to measure the peripapillary choroidal thickness in 40 eyes of our 40 participants, who had a mean age of 41.2 years (range, 15 to 84 years). Choroidal thickness measurements had strong inter-observer correlation at each sector (r = 0.901 to 0.991, p < 0.001). The mean choroidal thickness was 191 +/- 62 microm. Choroidal thickness was greatest at the temporal quadrant (mean +/- SD, 210 +/- 78 microm), followed by the superior (202 +/- 66 microm), nasal (187 +/- 64 microm), and inferior quadrants (152 +/- 59 microm). CONCLUSIONS: The measurement of choroidal thickness on peripapillary circle scan images for RNFL analysis using the 3D-OCT viewing program was highly reliable and efficient.

Comparison and Repeatability of Anterior Segment Parameters Obtained by Galilei and Slit-lamp Optical Coherence Tomography

PURPOSE: To evaluate the repeatability and comparability of anterior chamber depth (ACD) and central corneal thickness (CCT) measurements obtained by Galilei dual Scheimpflug analyzer (Ziemer, Port, Switzerland) and slit-lamp optical coherence tomography (SL-OCT; Heidelberg Engineering, Dossenheim, Germany). METHODS: ACD and CCT were measured by Galilei and SL-OCT in 68 eyes of 68 healthy young subjects. Each measurement was performed 3 times by a single examiner, and the repeatability of 3 consecutive measurements was analyzed. ACD and CCT measurements were compared between the 2 devices. RESULTS: Both Galilei and SL-OCT showed high repeatability (ICCs > or = 0.994) for ACD and CCT measurements. The mean ACD and CCT measured by Galilei were greater than SL-OCT measurements by 0.11 +/- 0.09 mm and 14.01 +/- 7.38 microm, respectively. The 95% limit of agreement values for ACD and CCT measurements were 0.36 mm, 27.66 microm, respectively, and were highly correlated (correlation coefficients > or = 0.89, p < 0.001). CONCLUSIONS: Although the repeatability of each device was high, ACD and CCT obtained by Galilei and SL-OCT were significantly different. These differences should be considered when interpreting ACD and CCT measurements obtained by the 2 devices.

Atypical Acute Syphilitic Posterior Placoid Chorioretinitis

A 48-year-old man presented with visual dimness in the right eye that had developed 2 weeks previously. Dilated fundus examination showed few vitreous cells and numerous yellow, placoid lesions in both eyes. His right eye had more severe serous retinal detachment involving the macula. Fluorescein angiography demonstrated early irregular hypofluorescence with late staining in the areas of the yellow placoid lesions. He started a regimen of 60 mg of oral prednisone daily. Two weeks later, a serologic fluorescent treponemal antigen absorption test was positive for Ig G and Ig M. He was referred to an infectious disease specialist for antibiotic therapy. A week later, he returned, having stayed on prednisone only and not having taken the internist's antibiotic prescription. Meanwhile, the chorioretinitis in his right eye, which had initially been at a more advanced stage, was resolved with the use of steroids. The chorioretinitis in his left eye, which was aggravated at an earlier stage, ultimately recovered. Our case had atypical courses such that one eye improved and the other worsened during the same steroid treatment period. This result was inconsistent with that of previous reports showing that oral steroid influences the clinical course of acute syphilitic posterior placoid chorioretinitis.

Pericardium Plug in the Repair of the Corneoscleral Fistula After Ahmed Glaucoma Valve Explantation

We report four cases in which a pericardium (Tutoplast(R)) plug was used to repair a corneoscleral fistula after Ahmed Glaucoma Valve (AGV) explantation. In four cases in which the AGV tube had been exposed, AGV explantation was performed using a pericardium (Tutoplast(R)) plug to seal the defect previously occupied by the tube. After debridement of the fistula, a piece of processed pericardium (Tutoplast(R)), measured 1 mm in width, was plugged into the fistula and secured with two interrupted 10-0 nylon sutures. To control intraocular pressure, a new AGV was implanted elsewhere in case 1, phaco-trabeculectomy was performed concurrently in case 2, cyclophotocoagulation was performed postoperatively in case 3 and anti-glaucomatous medication was added in case 4. No complication related to the fistula developed at the latest follow-up (range: 12~26 months). The pericardium (Tutoplast(R)) plug seems to be an effective method in the repair of corneoscleral fistulas resulting from explantation of glaucoma drainage implants.

Peripheral Anterior Synechiae and Ultrasound Biomicroscopic Parameters in Angle-Closure Glaucoma Suspects

PURPOSE: To investigate the correlation between peripheral anterior synechia (PAS) and the quantitative anterior chamber angle parameters measured by ultrasound microscopy (UBM) in angle-closure glaucoma suspect (ACGS) eyes. METHODS: Eyes were defined ACGS as having occludable angles and intraocular pressure less than 21 mm Hg without glaucomatous optic nerve head. The gonioscopic criteria for ACGS were the trabecular meshwork invisible in 3 or more quadrants of the entire angle and the angular width less than 20 degrees by Shaffer classification. Twenty-seven eyes of 20 patients underwent anterior chamber angle and ciliary body imaging with UBM. Angle opening distance (AOD500), angle recess area (ARA), trabecular-ciliary process distance (TCPD) and trabecular-iris angle (TIA) were measured from the UBM images at each quadrant. RESULTS: The AOD500, ARA, and TIA were not significantly different between the eyes with PAS (9 eyes) and without PAS (18 eyes) at each quadrant. However, the TCPD was significantly shorter in the superior quadrant when compared with the eyes without PAS (mean: 405.3+/-70.9 micrometer vs 536.4+/-140.5 micrometer) (p<0.05). CONCLUSIONS: The results suggest that the shorter distance from trabecular meshwork to ciliary body or the anterior placement of ciliary process may play a role in the development of PAS in ACGS eyes.

Axial Length and Proliferative Diabetic Retinopathy

PURPOSE: This study was conducted to investigate the relationship between axial length(AL) and proliferative diabetic retinopathy(PDR). METHODS: We reviewed the medical charts of the nondiabetic patients who had undergone cataract surgery and diabetic patients who had undergone vitrectomy or cataract surgery at Korea University Kuro Hospital between January, 1998 and July, 2000. Eyes with previous ocular surgery or other severe ocular disease were excluded from the analysis. Eyes with axial length greater than 24 mm were also excluded. The eyes were divided into 4 groups: Non-DM group, nondiabetic; Non-DR group, diabetic without retinopathy; NPDR group, with nonproliferative diabetic retinopathy; and PDR group, with proliferative diabetic retinopathy. Each group contained 42 eyes which were matched for age and sex. RESULTS: The AL values of each group were compared. The mean AL of the PDR group(22.2+/-0.8 mm) was significantly shorter than each of the other groups: Non-DM group(23.1+/-0.7 mm, p<0.05); Non-DR group(22.9+/-0.9 mm, p<0.05); NPDR group(22.8+/-0.8 mm, p<0.05). Within the PDR group, the eyes that had received preoperative panretinal photocoagulation(27 eyes, mean: 22.0+/-1.1 mm) showed a shorter AL than those that had not(15 eyes, mean: 22.7+/-0.8 mm), which was not statistically significant(P=0.08, t-test). CONCLUSION: The results suggest that a shorter axial length may be associated with severe proliferative diabetic retinopathy.

Treatment of Recalcitrant Orbital Implant Exposure using Upper Tarsoconjunctival Flap

PURPOSE: This study is to report a case of recalcitrant exposure of Medpor(R) orbital implant which required the use of an upper eyelid tarsoconjunctival flap. METHOD: A six year-old female patient presented with re-exposure of Medpor(R) orbital implant after 2 previous dermis grafts had failed. The downgrown conjunctival epithelial tissues were cryocoagulated. A fornix-based tarsoconjunctival flap was fashioned from the upper lid, inverted and placed over the sclera-covered exposed implant. After placement of a conformer, tarsorrhapy was done. The flap was divided with release of tarsorrhapy as a second stage procedure 4 weeks after the primary surgery. RESULT: The previously exposed implant remained covered and no other complication was observed during a one-year follow-up period. CONCLUSION: Upper tarsoconjunctival flap may be an excellent surgical method in treatment of recurrent exposure of orbital implants refractory to conventional therapies.

Clinical Results of Laser In Situ Keratomileusis Using Different Types of Excimer Laser: LaserScan LSX(R) versus OmniMed II(R)

PURPOSE: This study was retrospectively conducted to evaluate the clinical results of consecutive 167 myopic eyes of 117 patients undergoing laser in situ keratomileusis(LASIK) for myopia with either of the two excimer lasers, which differ in the method of laser delivery: flying spot scanning versus broad beam. METHODS: According to the laser used, the treated eyes were divided into two groups: Group I, 84 eyes of 58 patients with LaserScan LSX(R)(Lasersight Inc., USA); Group II, 83 eyes of 59 patients with OmniMed II(R)(Summit, USA). Each patient had been followed up for more than 6 months after surgery. Only single procedure outcomes were included. Mean preoperative spherical equivalents(SE) were -5.67+/-1.79 D(range:-1.50~-9.75 D) in group I and -6.40+/-1.79 D(range:-3.50~-9.75 D) in group II. RESULTS: At postoperative 6 months, mean uncorrected visual acuity increased to 0.94 in group I and 0.88 in group II. Uncorrected visual acuity of 20/40 or better occurred in 100% of group I and 96.4% of group II, and of 20/20 or better, in 57.2% and 48.2%, respectively. No eye in either group lost more than 1 line of best-corrected visual acuity. Mean SEs at postoperative 6 months were -0.28+/-0.50 D in group I and -0.55+/-0.60 D in group II(P<0.05). Manifest SEs were within +/-1.00 D in 97.6% of group I and 84.3% of group II, and +/-0.50 D in 73.8% and 60.2%, respectively. Intra- or postoperative complications were subconjunctival hemorrhage(4 eyes, group I; 5 eyes, group II), Sands of Sahara syndrome(7 eyes, group I; 5 eyes, group II), epithelial ingrowth(1 eye, group II only) and infectious keratitis(1 eye, group II only). No case had a central island or irregular astigmatism postoperatively. CONCLUSIONS: Our study suggests that LASIK using the LaserScan LSX(R)excimer effectively reduces myopia compared with OmniMed II(R). However, its predictability decreased as the attempted correction increased. LASIK for myopia less than -10 D with the LaserScan LSX(R)provided satisfactory refractive results that compare well with other reports in the literature.

Consecutive Esotropia after Surgical Correction of Intermittent Exotropia

Intentional overcorrection is recommended immediately after surgery of intermittent exotropia for its superior long-term prognosis. However, esotropia can develop in 6~15%, especially in children less than 4 years of age, and bring about the problems such as diplopia, suppression, decreased vision and impaired binocular single vision. The purpose of this study is to evaluate the factors possibly associated with its occurrence. A retrospective study was conducted on the 22 patients with consecutive esotropia, which had developed after surgical correction of intermittent exotropia. They underwent unilateral or bilateral medial rectus muscle recession for correction of esotropia. The mean angle of exodeviation before intermittent exotropia surgery was 30.0+/-5.2 PD(prism diopters)(23~40 PD). The mean angle of esodeviation at surgery for consecutive esotropia was 24.1+/-10.3 PD(10~55 PD). Before surgery of intermittent exotropia, 13 of the 16 patients(81.3%)had showed lateral incomitancy. No significant difference was found between age at surgery and consecutive esotropia. High AC/A ratio had been present preoperatively in only one patient. No patient showed A-V pattern preoperatively. Out of the 17 patients who had undergone bilateral lateral rectus recessions for intermittent exotropia, 10(58.8%) patients had either lateral rectus muscle recessed by 7.5 mm or more. Four of the 5 patients(80%)had a medial rectus resected by 5 mm or more. This study suggests that consecutive esotropia after intermittent exotropia surgery can develop more likely in the patients who have had lateral incomitancy, excessive recession of lateral rectus muscle by 7.5 mm or more, or excessive resection of medial rectus muscle by 5 mm or more.