Deepta Ghate

Correlations between parameters of aqueous humor dynamics and the influence of central corneal thickness

PURPOSE The individual parameters of aqueous humor dynamics may influence each other to maintain intraocular pressure (IOP) homeostasis. Central corneal thickness (CCT) is known to be associated with onset and progression of glaucoma and can potentially influence the individual parameters of aqueous humor dynamics that maintain IOP. This study investigates the correlation between parameters of aqueous humor dynamics and the influence of CCT in healthy volunteers and compares it with the correlations seen in patients with ocular hypertension. METHODS Aqueous humor dynamics (aqueous flow, outflow facility, and uveoscleral outflow), IOP, and pachymetry data from 94 healthy ocular normotensive (ONT) volunteers and 63 ocular hypertensive (OHT) patients was analyzed retrospectively. Linear correlations between individual aqueous humor dynamics parameters and pachymetry were evaluated using scatter plots and the Spearman correlation coefficient where appropriate. RESULTS In both groups, a significant (P < 0.05) negative correlation was found between corneal thickness and aqueous flow (ONT, R(2) = 0.14; OHT, R(2) = 0.10) and between corneal thickness and uveoscleral outflow (ONT and OHT, R(2) = 0.10). A significant (P < 0.05) positive correlation was found between aqueous flow and outflow facility (ONT, R (2) = 0.24; OHT, R(2) = 0.10). In healthy controls, but not OHT patients, a significant (P < 0.001) positive correlation was found between aqueous flow and uveoscleral outflow (R(2) = 0.15). CONCLUSIONS Thicker corneas may be associated with lower aqueous production and lower uveoscleral outflow. The interplay between parameters of aqueous humor dynamics suggests possible autoregulatory mechanisms in the eye. OHT may differ from ONT subjects in their inability to increase the uveoscleral outflow with increases in aqueous inflow.

Optic nerve morphology as marker for disease severity in cerebral palsy of perinatal origin

BACKGROUND It is difficult to predict the neurologic outcome and ambulatory status in children with perinatal neurologic insult until 2-5years age. This study aims to correlate clinical optic nerve head (ONH) findings-cupping, pallor and hypoplasia, with gestational period and neurologic (motor) outcomes in patients with cerebral palsy (CP) from perinatal insults. METHODS 54 consecutive patients with CP from perinatal insults were enrolled. Patients with intraocular disease, retinopathy of prematurity and hydrocephalus were excluded. ONH was labeled as pale, hypoplastic or large cup (cup/disc ratio≥0.5) if 2 ophthalmologists independently agreed after an ophthalmoscopic examination. Inter-rater reliability was excellent. RESULTS Mean age at examination was 10.98±6.49years; mean gestational period was 33.26±4.78weeks. Abnormal ONH (pallor, cupping or hypoplasia) was seen in 38/54 (70%) patients. Of patients with pallor (n=17), 88% were quadriplegic and 82% non-ambulatory. Mean cup/disc ratio was 0.45±0.22; 50% patients had large cup. Multivariate logistic regression models showed that disc pallor was associated with non-ambulatory status (OR: 21.7; p=0.003) and quadriplegia (OR: 12.8; p=0.03). Large cup was associated with age at examination (OR 1.15; p=0.03). Cup/disc ratio showed positive correlation with age at examination (Pearsons r=0.39; p=0.003). There was no significant association of ONH parameters with gestational age. CONCLUSION Clinically observed ONH changes (pallor, cupping and hypoplasia) are common in CP. Presence of ONH pallor serves as an indicator for poor motor outcome in patients who develop CP from perinatal causes and should prompt early referral for rehabilitation.

The Water-Drinking Test Revisited: An Analysis of Test Results in Subjects with Glaucoma

ABSTRACT Purpose: The Water-Drinking Test (WDT) has been shown to predict the diurnal IOP change. This study evaluates the factors that may affect the WDT results. Methods: This study was conducted on 203 glaucoma patients who had undergone trabeculectomy (53) or tube surgery (31), or had a medically controlled open-angle (82) or closed-angle (37) glaucoma. IOP was measured at baseline and then every 15 minutes over a one-hour period after drinking water. The main outcome measures were IOP change (increase in IOP from baseline) at all measurement time points, IOP peak (highest IOP after drinking water), IOP fluctuation (difference between IOP peak and baseline), and assessing the association of these IOPs with a patient’s demographic and management modalities. Results: The mean age of the participants was 54±18 years, and 113 (56%) were male. Female patients showed greater IOP fluctuation than males (7.28 vs. 5.92 mm Hg; P=0.016), and a greater IOP peak (22.7 vs. 20.1 mm Hg; P=0.001). The observed associations between gender and IOP changes were only significant in <50 years. IOP at 60 minutes was greater in tube than trabeculectomy (5.6 vs. 3.1 mm Hg; P=0.007). The number of topical medications showed a direct independent association with IOP changes (P<0.001). Compared to other classes of topical medications, latanoprost showed lower WDT-IOP profile (P=0.0003). Conclusions: WDT-IOP change was diminished in subjects on latanoprost, and was greater in females <50 years, and those on greater number of medications.

Intracranial Pressure Influences the Behavior of the Optic Nerve Head

In this work, the biomechanical responses of the optic nerve head (ONH) to acute elevations in intracranial pressure (ICP) were systematically investigated through numerical modeling. An orthogonal experimental design was developed to quantify the influence of ten input factors that govern the anatomy and material properties of the ONH on the peak maximum principal strain (MPS) in the lamina cribrosa (LC) and postlaminar neural tissue (PLNT). Results showed that the sensitivity of ONH responses to various input factors was region-specific. In the LC, the peak MPS was most strongly dependent on the sclera thickness, LC modulus, and scleral canal size, whereas in the PLNT, the peak MPS was more sensitive to the scleral canal size, neural tissue modulus, and pia mater modulus. The enforcement of clinically relevant ICP in the retro-orbital subarachnoid space influenced the sensitivity analysis. It also induced much larger strains in the PLNT than in the LC. Moreover, acute elevation of ICP leads to dramatic strain distribution changes in the PLNT, but had minimal impact on the LC. This work could help to better understand patient-specific responses, to provide guidance on biomechanical factors resulting in optic nerve diseases, such as glaucoma, papilledema, and ischemic optic neuropathy, and to illuminate the possibilities for exploiting their potential to treat and prevent ONH diseases.

Vision related quality of life in spinocerebellar ataxia

OBJECTIVE Spinocerebellar ataxia (SCA) leads to abnormal ocular motility and alignment. The objective of this study was to quantitatively assess vision, ocular motility and alignment and its impact on vision related quality of life (VRQOL) in SCA. METHODS Nineteen genetically diagnosed SCA subjects (11 SCA type 3, 3 SCA type 1 and 5 SCA type 6) participated at two university centers. All subjects completed the National Eye Institute Visual Function Questionnaire (NEI-VFQ), 10-Item Neuro-Ophthalmic Supplement (NOS), scale for assessment and rating of ataxia (SARA) and ophthalmic examination. Twelve subjects seen at one of the 2 sites underwent quantitative ocular motility and alignment assessment. RESULTS Composite scores for NEI-VFQ (mean 76.3±13) and NOS (mean 65.2±16.8) were significantly decreased in SCA subjects. NEI-VFQ subscale scores were decreased for general, near, distance and peripheral vision and driving. SCA patients had decreased low contrast sensitivity, stereoacuity and multiple ocular motility defects which included gaze limitation (9/12), nystagmus (5/12), distance esophoria (11/12), near exophoria (12/12) and receded near point of convergence. A significant negative correlation was noted between composite scores and distance convergence fusional amplitude. CONCLUSION VRQOL is significantly decreased in SCA compared to normal population. All SCA patients should be screened for visual disability and referred for neuro-ophthalmic assessment promptly.

Influence of intracranial pressure on the lamina Cribrosa

Glaucoma is an eye disease related with vision field loss. Although previous study has investigated the influence of intraocular pressure (IOP) on the glaucoma damage to the lamina cribrosa (LC), the intracranial pressure’s (ICP) effect on the LC has never been elucidated. The goal of this work is to determine the effect of ICP on the LC.Copyright