Optic Disc Dimensions Research Articles

Study on relationship between intraocular pressure and hyperthyroidism

Thyroid-associated ophthalmopathy (TAO) represents a persistent autoimmune inflammatory condition impacting various ocular components, including orbital fat (OF), extraocular muscles (EOMs), the eyeball, and associated eye structures. This disorder is closely associated with autoimmune thyroid pathology. A body of research has indicated an elevated susceptibility to heightened intraocular pressure (IOP) and glaucoma among individuals with thyroid-related ailments. Nonetheless, certain studies have expressed reservations about affirming these conclusions. Furthermore, there exists a diversity of viewpoints regarding the optimal approaches for managing elevated IOP in TAO patients afflicted with ocular hypertensionA prospective research investigation was undertaken within the Department of Ophthalmology at a Tertiary Care Teaching Hospital, spanning a duration of 12 months. The techniques employed for the diagnosis of open-angle glaucoma (OAG) have been comprehensively outlined. Goldmann applanation tonometry was utilized to determine intraocular pressure (IOP). Employing a Zeiss FF3 fundus camera, a series of dilated stereoscopic 300-color retinal and optic disc images were captured. The evaluation of optic disc photographs was conducted by one of two evaluators, both of whom remained masked to the study's particulars, employing a customized protocol. In order to ascertain optic disc dimensions, adjustments for camera magnification were performed, accounting for the spherical equivalent refraction of each individual eye.A total of 90 patients were examined. Of the 90 cases, male preponderance was noted. Among 90 patients, 20 (22.2%) were hyperthyroid, 61 (67.8%) were hypothyroid, and 9 (10%) patients were euthyroid. In our study shows the frequency of different symptoms among the study group. Most of the patients came with complaint itching of (27.8%). The second most common symptom was foreign body sensation (21.1%). In this study shows the different types of signs among these two groups. In hyperthyroid lid, retraction was more common (12%). In hypothyroid lid, edema was more common (18.5%). Frequency of dry eye syndrome in patients with TD was present; 29 (26.4%) patients had dry eye disease. Among 90 patients, proptosis was present in 4 patients had proptosis. Most of the patients were myopic.Our results imply the potential link between intraocular pressure (IOP) and thyroid-related disorders, particularly in individuals undergoing thyroxine treatment. Conducting further comprehensive investigations to explore and substantiate this prospective association is advisable.

Choroidal Abnormalities in Pediatric NF1: A Cohort Natural History Study.

Simple SummaryChoroidal abnormalities (CAs) have recently been introduced as one of the criteria for the diagnosis of neurofibromatosis type 1 (NF1). The aim of the present study was to assess the natural history of CAs in a large pediatric population affected by NF1, evaluating, on a long-term follow-up, CAs progression both in number and dimensions. To avoid bias due to the growing process of the eye, the CAs dimensions were normalized for the optic disc size. Our study demonstrated, in 99 eyes of 53 pediatric patients, an increase in the number, area and perimeter of CAs. The present study thus provides evidence that, in NF1 pediatric patients, CAs change with time, increasing both in number and dimensions, independently from the physiological growth of the eye. While the increase of the CAs number occurs particularly at an earlier age, the increase in the CAs dimensions is a slow process that remains constant during childhood.The purpose of this study was to assess the long-term natural history of choroidal abnormalities (CAs) in a large pediatric neurofibromatosis type 1 (NF1) population, quantifying their progression in number and dimensions. Pediatric patients (<16 years old) affected by NF1 with a minimum follow-up of 3 years with at least one CA in one eye were consecutively recruited. Near-infrared (NIR) imaging was performed to identify CAs, which were quantified in number and size. The CAs area and perimeter were normalized for the optic disc dimensions to avoid possible bias related to the growing process of the eye. Ninety-nine eyes of 53 patients were evaluated. The CAs number, area and perimeter significantly increased during follow-up (p < 0.0001 for each parameter). The patient age at baseline was inversely correlated with the CAs number over time (coefficient = −0.1313, p = 0.0068), while no correlation was found between the patient age and CAs progression in size. In conclusion, we provide evidence that, in NF1 pediatric patients, CAs change over time, increasing both in number and dimensions, independently from the physiological growth of the eye. While the increase of the CAs number occurs particularly at an earlier age, the increase in the CAs dimensions is a slow process that remains constant during childhood.

Optic disc morphometry using spectral domain optical coherence tomography in a Nigerian population.

To assess morphological optic disc dimensions using spectral-domain optical coherence tomography (OCT) in a Nigerian population. Good quality SD-OCT scans of the optic disc of 147 eyes of 88 participants were selected, enrolled, and retrospectively reviewed. All subjects had optic nerve head and retinal nerve fibre layer OCT imaging, as well as analysis, done using the Topcon 3D OCT-1 Maestro®. The age, sex, and some OCT-generated optic disc dimensions namely disc area (DA), vertical disc diameter (VDD), horizontal disc diameter (HDD) were retrieved from the database and analyzed. The mean age of the study subjects was 52.6±20.9 years with a range of 8-90 years; male to female ratio was 1:1.3. The right eye and left eye accounted for 75 and 72 of the 147 scans respectively. The mean DA, VDD, and HDD were 2.54 ± 0.48 mm2, 1926.5 ± 189.6 μm and 1673.9 ± 173.9 μm, respectively. Males had significantly larger DA than females (2.56 ± 0.53 mm2 vs 2.51 ± 0.44 mm2, p = 0.043). The mean DA and VDD of eyes of subjects aged 21-40 years were significantly higher compared to subjects aged 60 years and more (p = 0.008 and 0.001, respectively). The mean optic disc area and diameters are larger than those reported in similar studies involving blacks and other races. The mean disc area reduces with increasing age.

Fundus changes in high myopic Kashmiri population

Background: High myopia (defined as myopia of -6D or more) is one of the main causes of visual impairment worldwide. High myopia is always accompanied by pathological structural changes such as axial elongation, posterior staphyloma, lacquer crack formation, thinning of the retina and choroid, and choroidal neovascularization.&#x0D; Aims and Objectives: The purpose of this study was to examine the fundus changes in eyes with high myopia.&#x0D; Materials and Methods: All study participants underwent dilated fundus examination and fundus photography. Myopia-related macular (posterior staphyloma, lacquer cracks, Fuchs spot, myopic chorioretinal atrophy, and myopic choroidal neovascularization)and optic disc (optic nerve head tilt,optic disc dimensions, and peripapillary atrophy) changes were evaluated.&#x0D; Results: Statistical analysis was performed to evaluate fundus changes in eyes with high myopia. Data analysis included 107 eyes of 57 patients.Mean ± SE was 12.07 ± 3.184D in eyes with high myopia. Mean ± AL was 26.68± 1.577mm in eyes with high myopia. The mean age was 28.54 ± 9.44 years(14-50 years). Fundus changes were: Temporal crescent in 56 (52.33%) eyes, tessellated fundus appearance in 52(48.59%) eyes, lacquer cracks in 40 (37.38%) eyes, tilted disc in 30 (28%) eyes, lattice degeneration in 20(18.69%) eyes, posterior staphyloma in 20(18.69%) eyes, focal chorioretinal atrophy in 3 (2.8%) eyes. CNV in 2 (1.86%)eyes and retinal hole in 1(1%) eye.&#x0D; Conclusions: Tessellated fundus and temporal crescent were the most common fundus findings among Kashmiri population with high myopia. In this population, lacquer cracks and tilted disc were also common, while CNV and retinal holes were rare.

Quantitative automated circumpapillary microvascular density measurements: a new angioOCT-based methodology.

To develop a new methodology to detect glaucoma damage based on circumpapillary microvascular density (cpmVD) as measured by optical coherence tomography angiography (angioOCT). AngioOCT scans from a random eye of 40 healthy subjects (aged 63 ± 14 years) and 82 glaucoma patients (aged 66 ± 9 years with an average visual field loss of -7.8 ± 6.5 dB) were used to develop a new angioOCT evaluation methodology. Optic disc-centred 3 × 3 mm images were collected (Angioplex®, Zeiss Cirrus 5000 HD-OCT). An annular area with an inner radius of 1.16 mm and outer radius of 1.44 mm was chosen as the region of interest (ROI), with cpmVD calculated through lower envelope modulation avoiding the influence of the major retinal vessels. Additionally, the cpmVD and the microvascular density (mVD), stratified by sectors, were compared with the respective retinal nerve fibre layer (RNFL) thickness. A significantly lower cpmVD was observed in the glaucoma group, for all visual field sectors (p < 0.001), when comparing to the healthy group. The inferior and superior mVD sectors showed the largest differences between groups. Moreover, glaucoma was linked to a reduction of cpmVD variation when compared to the healthy group. Lastly, a comparison between two healthy subgroups showed that the method is not biased by the presence of slight movement artefacts, optic disc dimensions and vessel crowding (p > 0.05). The presented open-source methodology provides a robust quantitative analysis of the 360˚ mVD. It shows that cpmVD, and mVD sectors measured by angioOCT, can be used in everyday glaucoma practice.

Optic Nerve Head in Central Retinal Vein Occlusion by Spectral-Domain OCT

To evaluate the morphology of optic nerve head by spectral-domain optical coherence tomography (SD-OCT) in patients with unilateral central retinal vein occlusion (CRVO). In 39 consecutive patients with unilateral CRVO and 39 healthy controls, morphologic parameters of optic nerve head were assessed in both eyes by Spectralis SD-OCT using a custom radial B-scan pattern. The length of Bruch membrane opening (BMO) was measured in OCT scans, and optic disc diameters (DD) were assessed in infrared fundus photographs. Axial length was determined by IOLMaster. The BMO length was measured in all eyes with CRVO, while DD was not assessed in 9 eyes (27.3%) that had undefined disc margins. Compared to healthy controls (mean BMO length 1,511 ± 79 μm, mean disc diameter 1,521 ± 77 μm), in eyes with CRVO with defined disc margins (n = 28 [71.8%]), no significant difference was found in BMO length and DD (1,473 ± 118 μm and 1,516 ± 104 μm, respectively). Eyes with CRVO with undefined disc margins had lower BMO length (1,289 ± 61 μm [-14.7%], p = 0.001); also, in fellow eyes, these patients had lower BMO length and DD. In all groups, no significant difference was seen between BMO and DD. A correlation was found between axial length and BMO length and disc diameter (both p<0.001). Most of the eyes with CRVO had normal optic disc diameter, but about 25% of patients with CRVO have reduced optic disc dimensions.

Myopia-Related Fundus Changes in Singapore Adults With High Myopia

To examine the pattern of myopia-related macular and optic disc changes in Singapore adults with high myopia (spherical equivalent ≤-6.00 diopters). Asian adults with high myopia from 3 population-based surveys. Adults 40 years and older (n= 359) with high myopia were pooled from 3 population-based surveys in Singapore Asians: (1) the Singapore Prospective Study Program (SP2, n= 184); (2) the Singapore Malay Eye Study (SiMES, n= 98); and (3) the Singapore Indian Eye Study (SINDI, n= 77). All study participants underwent standardized refraction and fundus photography, and SiMES and SINDI subjects also completed ocular biometry measurements. Myopia-related macular (posterior staphyloma, lacquer cracks, Fuchs spot, myopic chorioretinal atrophy, and myopic choroidal neovascularization) and optic disc (optic nerve head tilt, optic disc dimensions, and peripapillary atrophy) changes were evaluated. The most common myopia-related macular finding in adults with high myopia was staphyloma (23%), followed by chorioretinal atrophy (19.3%). There were few cases of lacquer crack (n= 6, 1.8%), T-sign (n=6, 1.8%), retinal hemorrhage (n= 3, 0.9%), active myopic choroidal neovascularization (n= 3, 0.9%), and no case of Fuchs spot. The most common disc finding associated with high myopia was peripapillary atrophy (81.2%), followed by disc tilt (57.4%). Staphyloma and chorioretinal atrophy increased in prevalence with increasing age, increasing myopic refractive error, and increasing axial length (all P < .001). Ethnicity comparisons demonstrated the highest proportion of staphyloma (P= .04) among Malays, the highest proportion of peripapillary atrophy (P= .01) and disc tilt (P < .001) among Chinese, and the largest cup-to-disc ratio (P<.001) among Indians. Staphyloma and chorioretinal atrophy lesions were the most common fundus findings among Asian adults with high myopia. In this population, tilted discs and peripapillary atrophy were also common, while choroidal neovascularization and Fuchs spot were rare. In contrast with Singapore teenagers, in whom tilted disc and peripapillary atrophy were common while staphyloma and chorioretinal atrophy were rare, pathologic myopia appears to be dependent on the duration of disease and, thus, ageofthe individual.

Optic Disc Dimensions and Cup-Disc Ratios among Healthy South Indians: The Chennai Glaucoma Study

Purpose: To present optic disc and cup dimensions, cup-disc ratios (CDRs) and asymmetry among healthy South Indians, and their associations with ocular and systemic variables.Methods: A total of 623 healthy phakic participants of the Chennai Glaucoma Study underwent complete eye examinations including optic disc stereo-photography. Planimetry was performed under stereo-viewing conditions. The morphological type of cupping (no cups, steep cups, partly sloping and fully sloping cups) was identified based on a modification of the classification by Jonas et al. The associations of planimetric measures (optic disc area, cup area and vertical cup-disc ratio [VCDR]) with age, gender, height, intraocular pressure, refraction, astigmatism, axial length and corneal thickness as explanatory variables were examined. The associations of asymmetries in the above planimetric measures with age, gender and asymmetries of the above explanatory variables were examined.Results: Mean optic disc and cup areas were 2.82 ± 0.52 mm2 and 0.53 ± 0.39 mm2. Mean CDR was 0.36 ± 0.18. Men had larger discs (P = 0.03). Cup area and VCDR revealed significant associations with disc area (P <0.0001) and type of cupping (P < 0.0001). Mean disc and cup area asymmetries were 0.19 ± 0.16 mm2 and 0.15 ± 0.15 mm2. Mean VCDR asymmetry was 0.07 ± 0.08 mm2. Cup area and VCDR asymmetries showed significant associations with disc area asymmetry (P < 0.0001, both) and asymmetry in the presence or absence of physiological cupping, i.e. subjects with physiological cupping in one eye and no cupping in the other (P < 0.0001, both).Conclusions: We present normative optic disc, cup and VCDR measures and asymmetries among healthy South Indians. We demonstrated the dependence of VCDR on the morphological type of cupping.

Heritability of optic disc diameters: a twin study

To assess the relative influence of genetic and environmental factors on optic disc size and cup/disc ratio in healthy eyes. A sample of 55 monozygotic and 50 dizygotic healthy twin pairs aged 20-46, all having the same sex within pairs (47 pairs were male) had optic discs measured from colour fundus photographs according to the Wisconsin Protocol. Structural equation modelling was used to estimate the relative contribution of genetic and environmental factors to the phenotype. Disc dimensions did not vary significantly by age or sex. After adjusting for age and sex, additive genetic factors (i.e. heritability) explained 77% (95% CI: 65-85%) of variation of vertical disc diameters, whereas estimated unshared environmental effect was 23% (95% CI: 15-35%). For vertical cup diameters, heritability accounted for 70% (95% CI: 55-80%) and environmental factors 30% (95% CI: 20-45%). For cup/disc ratio, additive genetic and unshared environmental factors explained 66% (95% CI: 48-77%) and 34% (95% CI: 23-52%) of the variations, respectively. In this healthy twin sample, we found that three quarters of the variations in vertical optic disc and optic cup diameters were attributable to genetic influence.

Iris colour, optic disc dimensions, degree and progression of glaucomatous optic nerve damage

To evaluate whether iris colour influences size and shape of the optic nerve head and risk for glaucoma progression. The hospital-based observational study included 1973 eyes of 1012 Caucasian subjects with ocular hypertension or chronic open-angle glaucoma. For all patients, colour stereo optic disc photographs were evaluated, and corneal pachymetry and achromatic perimetry were performed. Main outcome measures were optic nerve head parameters, the development or progression of visual field defects and iris colour. In most of the study groups, size of the optic disc, neuroretinal rim, alpha zone and beta zone of parapapillary atrophy, retinal vessel diameter and central corneal thickness did not differ significantly between eyes with blue, green, brown and mixed iris colour. In the normal-pressure glaucoma group, neuroretinal rim area was smallest in the population with mixed-coloured eyes and largest in the group of eyes with brown irides (P = 0.001 after correction for inter-eye dependency and multiple testing). For the ocular hypertensive subjects and glaucoma patients with follow-up examinations, the rate of development or progression of glaucomatous visual field loss was not significantly associated with iris colour (P = 0.060). In Caucasian subjects, iris colour does not have a major association with the size of the optic nerve head structures, central corneal thickness and retinal arterial diameter. In Caucasian patients with ocular hypertension or chronic open-angle glaucoma, an influence of iris colour on the risk for development or progression of glaucomatous visual field defects could not be confirmed.

Keratometry, Optic Disc Dimensions, and Degree and Progression of Glaucomatous Optic Nerve Damage

To evaluate whether keratometric readings as a measure of corneal shape are associated with optic disc dimensions and with the degree and rate of perimetric progression of chronic open-angle glaucoma or ocular hypertension. The hospital-based observational study included 1826 eyes of 936 patients with ocular hypertension, patients with chronic open-angle glaucoma, or normal individuals. For 733 ocular hypertensive or glaucomatous eyes, follow-up examinations were performed with a mean follow-up time of 58.0+/-34.7 months. Observation procedures were keratometry, morphometric optic disc analysis, tonometry, and perimetry. In the normal study group, area of the neuroretinal rim, alpha zone and beta zone of parapapillary atrophy, and retinal vessel diameter were not significantly associated with keratometric readings. In the entire study population, the optic disc area was significantly (P<0.001; r=-0.27) correlated with low keratometric readings as expressed in diopters. Keratometric readings were significantly (P<0.001 adjusted for age, intraocular pressure, baseline damage, and corneal asphericity) smaller in the normal-pressure glaucoma group than in the normal study group and in the groups with ocular hypertension or primary and secondary open-angle glaucoma. Rate of perimetric progression was not significantly associated with low keratometric readings, either in simple or in multiple Cox regression analysis, controlling for baseline damage, ocular hypertension, age, corneal asphericity, and intraocular pressure. Large optic disc area is statistically significantly, but clinically weakly, correlated with low keratometric readings (diopters). In Caucasian individuals with ocular hypertension and patients with chronic open-angle glaucoma, the rate of development or progression of glaucomatous visual field defects is not significantly associated with keratometric readings.

Inter-observer agreement in clinical optic disc measurement using a modified 60 D lens.

To assess the inter-observer agreement of the measurement of optic disc dimensions by two observers using a modified 60 dioptre (D) fundus examination lens. The vertical disc and cup diameters of 29 eyes were measured by two independent observers using a 60 D lens modified by incorporation of a 0.1 millimetre scale graticule. The vertical cup/disc ratio was calculated. Inter-observer agreement was assessed by calculation of the inter-observer differences and by the weighted kappa statistic. The two observers showed good agreement for the measurement of disc diameter (mean difference -0.04; range -0.04, 0.2) and for cup diameter (mean difference -0.03; range 0.3, 0.2). Closer agreement for the vertical cup/disc ratio was achieved (mean kappa 0.96; 95% confidence limits 0.90, 1.0). The 95% confidence limit for the mean inter-observer difference in cup/disc ratio was 0.11, suggesting that a change of > 0.1 in the assessment of the cup/disc ratio by this technique is significant at the 5% level. High inter-observer agreement of optic disc measurement can be achieved with this technique. The method has the potential to improve the clinical evaluation of the optic disc and the precision and accuracy of the clinical measurement of other fundal structures.

Ophthalmoscopic Measurement of the Optic Disc

The authors evaluated whether the optic disc dimensions can be measured directly by ophthalmoscopy without the use of a fundus camera or special ophthalmoscope. The horizontal and vertical disc diameters were measured ophthalmoscopically in 158 eyes of 95 subjects using a standard Goldmann three-mirror contact lens and a commercial slit lamp with adjustable length of the beam. The refractive error ranged from -7.25 to 3.5 diopters. Based on these direct measurements, the authors calculated the disc area by applying a modified formula for an ellipse, where area = pi/4 x the horizontal diameter x the vertical diameter. Additionally, the authors determined by planimetry the diameters and area of the disc on color photographs after correcting the ocular and photographic magnification. The values of the disc diameters as determined by photography were x1.27 larger than those measured with the Goldmann contact lens. Taking into account this constant correction factor of 1.27 for all eyes examined, the disc diameters, as measured by the Goldmann lens, varied by 0.11 +/- 0.06 mm or 5.8% +/- 3.5% from the values measured on the photographs. This error decreased slightly (P = 0.04) with increasing disc size. It was independent of the refractive error. The calculated disc area based on the ophthalmoscopically determined disc diameters differed by 9.4% +/- 6.6% from the disc area as measured by planimetry on the photographs. For clinical purposes, the optic disc and other structures of the posterior fundus can be measured by ophthalmoscopy using a Goldmann contact lens and a slit lamp with adjustable beam length. The optic disc area can be calculated by the formula: horizontal disc diameter x vertical disc diameter x pi/4.

Size of the optic nerve scleral canal and comparison with intravital determination of optic disc dimensions.

Diameters, area, and form of the optic nerve scleral canal were measured in 107 freshly enucleated, unfixed, human donor eyes. Macrophotographs of the sectioned posterior fundus pole were provided with a millimeter scale and evaluated planimetrically. They revealed a surprising variation: area: 2.59 +/- 0.72 mm2 (minimum 0.68 mm2, maximum 4.42 mm2); minimal diameter: 1.67 +/- 0.72 mm; maximal diameter: 1.92 +/- 0.32 mm. The mean form factor was 0.92 +/- 0.11 and the quotient of minimal to maximal diameter 0.86 +/- 0.11, indicating a slightly oval nearly round form. The coefficients of variation of the method's reproducibility were 0.005 for intraobserver and 0.02 for interobserver determination. The size values of these optic nerve scleral canals were not significantly (Wilcoxon-Mann-Whitney test) different from than those of 100 unselected optic discs that had been determined intravitally using Littmann's method. This indicates the reliability of Littmann's method for the intravital measurement of the optic nerve head in absolute dimensions.