Nasal Anterior Chamber Angle Research Articles

Observational and non-interventional study to evaluate angle parameters of patients with or without the diagnosis of glaucoma

Purpose: The aim of the study was to assess the different parameters of anterior chamber angle (AA) with anterior segment optical coherence tomography (OCT) in patients with or without the diagnosis of glaucoma. Methods: A cross-sectional and observation study of angle parameters for clinically diagnosed, undiagnosed, and suspected patients of angle closure was done. Patients with glaucoma suspect not having angle closure were also included in the study. AAs (nasal and temporal), AC depth (ACD), AC area (ACA), and central corneal thickness (CCT) were assessed using Cirrus high-definition optical coherence tomography. Results: Total 349 eyes of 178 patients with mean age of 41.31 ± 13.61 years were analyzed. One hundred and six of them were female (59.55%) and 72 were male (40.45%). The mean values of CCT were 540.85 ± 39.99 µm, 536.44 ± 41.25 µm; ACD were 2.37 ± 0.5 mm, 2.45 ± 0.4 mm, ACA were 17.04 ± 5.20 mm2, 17.48 ± 4.47 mm2, and AC width were 11.10 ± 0.45 mm, 14.13 ± 0.39 mm for the right and left eyes, respectively. The mean AA for the right and left eyes were nasal 22.23° ± 14.57°, 24.14° ± 14.10°; temporal 25.18° ± 14.13°, 25.88° ± 13.55°, respectively. Conclusion: The nasal AA was found to be significantly narrower than the temporal angle in both right and left eyes; and the angle asymmetry increases with increasing age.

Changes in corneal high order aberrations and anterior chamber parameters following scleral fixated intraocular lens implantation

BackgroundTo evaluate the change in corneal high order aberrations (HOAs) and anterior chamber parameters following scleral fixation in aphakic patients using the Scheimpflug camera system. MethodsThis retrospective study included patients who were aphakic after phacoemulsification surgery and underwent scleral-fixed intraocular lens (SF-IOL) implantation with Z suture technique between 2010 and 2022. Preoperative and postoperative best corrected visual acuity (BCVA), anterior segment parameters and corneal aberrations were evaluated with a combined Scheimpflug-Placido disk corneal topography device (Sirius Costruzione Strumenti Oftalmici, Florence, Italy). The following values were recorded: Simulated keratometry (SimK), flat meridian (K1), steep meridian (K2), iridocorneal angle (ICA), temporal anterior chamber angle (T-ACA), nasal anterior chamber angle (N-ACA), horizontal anterior chamber diameter (HACD), anterior chamber volume (ACV), corneal volume (CV), total Root Mean Square (RMS), high order aberrations (HOAs), spherical aberration, coma, trefoil, quadrifoil, and secondary astigmatism. ResultsThe study included 31 eyes of 31 patients (mean age: 63.00 ± 19.41 years, 17 males/14 females). Postoperative BCVA was better than preoperative BCVA (p = 0.012). Postoperatively, there was a statistically significant increase in ACV and CV values and a statistically significant decrease in K2 (p = 0.009, p = 0.032, p = 0.015). Preoperative T-ACA and preoperative and postoperative ACV were negatively correlated with postoperative intraocular pressure (r=-0.427 p = 0.033, r=-0.406 p = 0.032 and r=-0.561 p = 0.001). There were statistically significant postoperative increases in corneal RMS, trefoil and HOAs for 3 mm pupil diameter (p = 0.0177, p = 0.001, p = 0.031) and in corneal RMS, trefoil and quadrifoil aberrations for 6 mm pupil diameter (p = 0.033, p = 0.001, p = 0.001). ConclusionsIn conclusion, SF-IOL implantation with Z-suture technique used for visual rehabilitation of aphakic patients may affect visual quality by increasing corneal HOAs while improving visual acuity.

Changes in anterior chamber dimensions following small incision lenticule extraction (SMILE).

To evaluate the changes in anterior chamber dimensions including horizontal anterior chamber diameter (HACD), anterior chamber depth (ACD), and iridocorneal angle (ICA) following small incision lenticule extraction (SMILE) using Scheimpflug-Placido disk tomographer (Sirius). The records of the 73 eyes of 47 patients who received SMILE for myopia and myopic astigmatism were retrospectively reviewed. Preoperative and 6-month postoperative measurements of central corneal thickness (CCT), HACD, ACD, ICA, nasal anterior chamber angle (nACA), and temporal anterior chamber angle (tACA) were obtained by tomography, and compared with paired t-tests. Pearson's correlation and linear regression tests were used to evaluate the relationship between these parameters. The CCT, HACD, and ACD values decreased significantly at 6-month postoperatively (p < 0.05 for all). ICA, nACA, and tACA showed no statistically significant difference postoperatively (p = 0.54, p = 0.118, and p = 0.255, respectively). Pearson's correlation analysis confirms negative relationship between Δ-HACD and Δ-tACA (r = -0.475, p < 0.01), and a loose negative relationship between change in ACD and change in ICA (r = -0.282, p = 0.016). Age and Δ-tACA were found as predictive parameters for Δ-HACD and, Δ-ICA was a predictor for Δ-ACD. While HACD and ACD decreased significantly, there was no significant change in ICA, nACA and tACA. Changes in HACD and ACD should be considered in terms of subsequent surgeries after SMILE.

Evaluation of the effects of duloxetine treatment on anterior segment parameters by optical coherence tomography.

To evaluate the effects of Duloxetine on anterior segment parameters and intraocular pressure (IOP) in open angle eyes. 38 eyes of 38 patients with fibromyalgia who had open or wide open angles according to the Shaffer classification. Anterior segment optic coherence tomography was performed before and after (month 3) Duloxetine treatment. IOP, central corneal thickness (CCT), corneal endothelial cell density (CECD) and anterior chamber depth (ACD) were also recorded and evaluated. No statistically significant difference was determined in IOP, CCT and CECD (p > 0.05). However, a statistically significant decrease was determined in both the temporal and nasal anterior chamber angle, angle opening distance, nasal trabecular-iris space area and ACD values between the baseline and month 3 (p < 0.001). We think that the short term use of Duloxetine does not lead to clinically significant changes despite their statistically significant effects on the anterior chamber parameters.

Изменения иридо-хрусталиковой диафрагмы на фоне трех загрузочных интравитреальных инъекций anti-VEGF препарата

Purpose. To use anterior segment optical coherence tomography (AS-OCT) to evaluate the lens-iris diaphragm after intravitreal injections (IVI) of anti-vascular endothelial growth factor (anti-VEGF). Material and methods. Twenty patients scheduled for IVI of anti-VEGF for the treatment of neovascular age-related macular degeneration (NVAMD) were enrolled in this study. All patients underwent a standard ophthalmological examination and AS-OCT. Intraocular pressure (IOP) was measured before IVI, after 1 minute, 30 minutes and after 3 hours. Results. The average thickness of the lens was 5.65 ± 0.7 mm. The mean anterior chamber (AC) depth before IVI was 2.584 ± 0.33 mm, one month after the 1 st IVI was 2.563 ± 0.34 mm, one month after the 3 rd IVI was 2.543 ± 0.34 mm; there was a significant decrease in the size of the AC depth after three injections by an average of 0.0409 ± 0.03 mm (p &lt; 0.05), and a lower AC depth was associated with a greater rise in IOP immediately after the injection ( = 0,412, p &lt; 0,05). There is significant narrowing of the temporal and nasal anterior chamber angle in the meridian 0–180° before the treatment and one month after three loading doses (p &lt; 0,05). Conclusions. After three loading IVI, there are significant changes in the lens-iris diaphragm were observed in patients with NVAMD according to AS-OCT data. It is necessary to analyse long-term results in a larger sample of patients to further study the mechanisms of increased IOP after IVI. Keywords: anti-VEGF drugs, intravitreal injection, intraocular pressure, lens-iris diaphragm.

Distribution of anterior chamber angle measurements in South African young adults: an optical coherence tomography study

Assessment of anterior chamber angle (ACA) variables is important to screen, diagnose and monitor ocular anomalies. Even though data on ACA variables, such as angle-opening distance taken at 500µm (AOD500) and trabecular-iris angle (TIA), are available in the literature, limited information is available about these variables in African sub-populations. The purpose of this study is to describe the distribution of ACA measurements (AOD500 and TIA) in a South African young adult population. In this cross-sectional study, 700 young adults were recruited from a university student population using two-stage random sampling. The Optovue iVue 100 optical coherence tomographer was used to measure the ACA variables. The distribution of the AOD500 and TIA measurements was analysed using descriptive and inferential statistics. Data from only the right eyes were analysed because the ACA measurements in the two eyes showed high levels of interocular symmetry. The measurements for the nasal and temporal ACAs were asymmetrically distributed (p < 0.001). The median AOD500 measurements in the nasal and temporal angles were 539µm and 542µm, respectively. The median TIA measurements were similar (~ 36°) in the two horizontal angles. The temporal ACA measurements were slightly higher than the nasal ACA measurements. Females had higher median ACA measurements than males (p ≥ 0.029). The ACA measurements in South African young adults resemble non-Gaussian curves. The ACA measurements are different from that reported in other sub-populations worldwide and most participants had ACA measurements associated with non-occludable ACAs.

Effect of iStent Trabecular Micro-Bypass device on outflow system morphology

Purpose: Rigorous clinical testing has established that Schlemm’s canal cross-sectional area (SC-CSA) is reduced in glaucomatous eyes. However, to date, it is unclear whether trabecular bypass procedures impact the morphology of the proximal aqueous outflow tract, or if the introduction of a local region of low outflow resistance adversely affects SC-CSA elsewhere, specifically presenting as SC diminution. This study quantifies changes in the morphology of the distal outflow pathway after iStent Trabecular Micro-Bypass stent (Glaukos Corp, Laguna Hills, CA, USA) implantation in living eyes by anterior segment optical coherence tomography (OCT).&#x0D; Design: This was a prospective observational study.&#x0D; Subjects: This study included six patients (eight eyes) with primary-open angle glaucoma.&#x0D; Methods: Patients underwent iStent placement in the nasal anterior chamber angle quadrant. OCT imaging was obtained of both nasal and temporal eye quadrants before and after surgery. For each SC parameter, an average of ten consecutive, evenly spaced measurements were manually obtained over a 1 mm segment of SC on FIJI ImageJ. Linear mixed effects modeling quantified the effect of the iStent on these parameters.&#x0D; Main outcome measures: Main outcome measures were changes in SC-CSA, inner-to-outer wall distance (IOD), and trabecular meshwork (TM) thickness following iStent placement.&#x0D; Results: Following iStent placement, total SC-CSA increased an average of 1,039.12 μm2 (P = 0.05). Individually, there were no significant changes in SC-CSA in the nasal or temporal quadrants. Total SC-IOD and nasal SC-IOD increased an average of 2.35 μm (P = 0.01) and 2.96 μm (P = 0.04), respectively. There were no significant changes in temporal quadrant SC-IOD. There were no significant changes in TM thickness in either quadrant.&#x0D; Conclusions: Implantation of the iStent Trabecular Micro-Bypass stent significantly increases SC-IOD in the nasal quadrant at the location of implant, with no evidence of SC diminution in the temporal quadrant. It remains unclear how these observations relate to the surgical efficacy of trabecular bypass procedures.

Medium-term Anatomical Results of Laser Peripheral Iridoplasty: An Anterior Segment Optical Coherence Tomography Study.

AimTo evaluate by anterior segment optical coherence tomography (AS-OCT) the medium-term (mean duration 3.2 years) anatomical changes in the anterior chamber angle (ACA) after laser peripheral iridoplasty.Materials and methodsThis is a longitudinal, retrospective case series of 31 eyes of 31 patients with primary angle-closure suspicion, primary angle closure (PAC), or primary angle-closure glaucoma (PACG) who underwent laser peripheral iridoplasty. All patients had persistent iridotrabecular contact (ITC) despite the presence of a patent peripheral iridotomy (PI). An AS-OCT was performed in dark conditions before and after laser iridoplasty. Quadrants of ITC, intraocular pressure (IOP), and the AS-OCT parameters of the temporal and nasal ACAs were measured and analyzed.ResultsPrior to iridoplasty, the average number of quadrants of ITC was 3.3. At the first postiridoplasty visit (mean duration 6.8 weeks), this reduced to 1.7 quadrants but increased to 1.9 by the final follow-up visit (mean duration 3.2 years). Twenty-five patients (80.1%) had less ITC at the first postlaser visit increasing to 27 (87.1%) patients by the final visit. Two (6.5%) required a second iridoplasty, while 3 (9.7%) required cataract surgery. All parameters of angle width showed a statistically significant increase in magnitude. All patients maintained IOP ≥ 21 mm Hg throughout the follow-up period.ConclusionIridoplasty is a useful adjunct in widening the ACA, particularly in those with persistent angle closure after iridotomy but with no cataract. While not successful in all patients, it can act as a temporizing measure to widen the drainage angle until such time that cataract surgery can be performed.Clinical significanceLaser peripheral iridoplasty can be used as an adjunct in angle-closure glaucoma patients with no cataract.How to cite this article: Hooshmand J, Leong JCY, O’Connor J, Ang GS, Wells AP. Medium-term Anatomical Results of Laser Peripheral Iridoplasty: An Anterior Segment Optical Coherence Tomography Study. J Curr Glaucoma Pract 2017;11(3):113-119.

Anterior Segment Optical Coherence Tomography Changes to the Anterior Chamber Angle in the Short-term following Laser Peripheral Iridoplasty.

ABSTRACTPurpose: To evaluate, by anterior segment optical coherence tomography (AS-OCT), the changes in the anterior chamber angle during the short-term postoperative period after diode laser peripheral iridoplasty (LPI).Methods: Retrospective, observational study of consecutive primary angle closure suspect, primary angle closure, or primary angle closure glaucoma patients who underwent LPI. These patients had persistent iridotrabecular contact despite the presence of a patent peripheral iridotomy.The AS-OCT images of the temporal and nasal anterior chamber angles in dark conditions before and after LPI were ana lyzed. The main outcome measures were changed in AS-OCT parameters such as trabecular-iris angle (TIA), angle opening distance (AOD), trabecular-iris space area (TISA), trabecular-iris contact length (TICL), iris thickness (IT), and maximum iris bow height (MIBH). Secondary outcome para meters included intraocular pressure (IOP) and postlaser complications.Results: Images of 14 eyes of 14 patients were assessed. The mean time from LPI to the follow-up AS-OCT scan was 6 ± 3 weeks. The IT did not alter significantly after LPI, but there were significant increases in the TIA, AOD and TISA, as well as a significant decrease in TICL and MIBH. There were no significant postlaser complications. There was a small decrease in mean IOP from 17.1 ± 4.0 mm Hg to 14.8 ± 4.6 mm Hg (p = 0.014).Conclusion: Based on AS-OCT imaging, LPI resulted in significant angle widening and iris profile fattening during the short-term postoperative period in eyes with persistent angle closure despite the presence of a patent peripheral iridotomy.How to cite this article: Leong JCY, O'Connor J, Ang GS, Wells AP. Anterior Segment Optical Coherence Tomography Changes to the Anterior Chamber Angle in the Short-term following Laser Peripheral Iridoplasty. J Current Glau Prac 2014;8(1):1-6.

Pentacam anterior chamber parameters in young and middle‐aged Chinese

BackgroundThe aim was to compare the anterior segment of two groups of Chinese using the Pentacam system.MethodsFifty young (median age 21-years) and 50 middle‐aged (median age 46-years) subjects with equal numbers of males and females had their axial length measured with the IOL Master. Their axial anterior chamber depth, anterior chamber volume and temporal and nasal anterior chamber angles were measured using the Pentacam and comparisons were made between the two groups.ResultsBoth groups shared similar axial lengths (unpaired t‐test: p = 0.37) but young subjects had significantly deeper anterior chamber by 11 per cent (3.60 ± 0.40-mm) compared with middle‐aged subjects (3.24 ± 0.34-mm) (analysis of variance: p < 0.001). The anterior chamber volume was significantly greater in young subjects by 24 per cent (200.12 ± 35.59-mm3) than the middle‐aged subjects (161.03 ± 37.79-mm3). The associations of anterior chamber depth and anterior chamber volume with axial length were significant (R2 from 0.16 to 0.50) and similar in both groups. Young subjects had wider anterior chamber angles (mean differences: 4.60° and 6.07° at temporal and nasal, respectively) than middle‐aged subjects. Among middle‐aged subjects, females had significantly shorter axial length but anterior chamber depths were similar between the two sexes. Females had significantly smaller anterior chamber volumes.ConclusionsMiddle‐aged subjects had more crowded anterior chambers than young subjects with similar axial lengths. Anterior chamber volume may be a more sensitive parameter to reveal this difference than a linear measurement of the anterior chamber depth.

Anterior segment morphometry and intraocular pressure change after uneventful phacoemulsification

To evaluate the changes in anterior segment morphometry and intraocular pressure (IOP) with 3D rotating Scheimpflug camera-topography system after uneventful phacoemulsification. Materials and methods: In 56 eyes of 54 patients, anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), and central corneal thickness (CCT) were measured with the Sirius 3D Rotating Scheimpflug camera-topography system preoperatively and 1 month after surgery. IOP was measured with applanation tonometer. The preoperative and postoperative results were compared. Results: Preoperative and postoperative anterior segment parameters were as follows: ACD 2.7 ± 0.4 and 3.5 ± 0.3 mm, ACV 143.6 ± 48.8 and 192.4 ± 59.5 mm3, nasal ACA 42.3 ± 8.4° and 53.0 ± 4.5°, temporal ACA 36.9 ± 11.9° and 45.8 ± 13.2° (P < 0.001). CCT, iris diameter, and pupil diameter changes were not statistically significant (P > 0.05). Mean axial length (AL) was 23.4 ± 0.8 mm. The IOP and corrected IOP were 14.6 ± 3.5 and 14.5 ± 3.9 preoperatively and 10.4 ± 2.4 and 10.0 ± 3.3 mmHg postoperatively (P < 0.001). There was not a correlation between AL and IOP, ACD, ACV, or ACA, and no correlation was found between IOP change and ACD, ACV, or ACA (P > 0.05). Conclusion: Measurements confirm that after uneventful phacoemulsification, IOP decreases while ACD, ACV, and ACA increase. Preoperative AL and IOP changes did not correlate with ACD, ACV, and ACA.

Pentacam sensitivity and specificity in detecting occludable angles

To assess the sensitivity and specificity of Pentacam measurements in detection of occludable angles and to provide cutoff values. Observational, single-center, cross-sectional study on 64 Caucasian eyes: 28 (43.7%) primary narrow angles or primary angle-closure glaucoma, and 36 (56.2%) controls: all subjects were evaluated and classified by gonioscopy (Shaffer classification). The following measurements have been considered: superior and inferior anterior chamber angle (ACA), temporal and nasal ACA, anterior chamber depth (ACD) using 5 value representation (central, superior, inferior, nasal, temporal), and anterior chamber volume (ACV). Validity of Pentacam parameters to detect patients in Shaffer 0 or I class was assessed by receiver operating characteristic (ROC) curves analysis; cutoffs were chosen as to maximize sensitivity and specificity. All the considered Pentacam measures were statistically different between the 2 groups (p<0.0001). All Shaffer grade groups differed in all parameters (p<0.001), except for grade 0 and I, which did not differ in any. Area under the curve ROC analysis revealed high discriminant power of all Pentacam measures: ACA = 0.94; ACD = 0.91; ACD central = 0.89; and ACV = 0.89. Chosen cutoff values (ACA = 22.4°; ACD = 1.12 mm; ACD central = 1.93 mm; ACV = 84 mm3) allowed correct classification of narrow angles. The study pointed out a high power of Pentacam AVA, ACV, and ACD in detecting occludable angles. Pentacam is simple to use, reliable, and noncontact, provides parameters in a short period, and represents a possible screening tool.

Dynamic Analysis of Iris Configuration with Anterior Segment Optical Coherence Tomography

To evaluate dynamic changes in iris configuration and their association with anterior chamber angle width by using anterior segment optical coherence tomography (ASOCT). Forty-six normal subjects with open angles and 40 with narrow angles (Shaffer grade < or =2 in three or more quadrants during dark room gonioscopy) were analyzed. The dynamic ASOCT dark-light changes of iris bowing were captured with real-time video recording and nasal iris bowing, nasal anterior chamber angle, and pupil diameter were measured in serial image frames selected from the video capture. The associations between iris bowing, iris thickness, anterior chamber depth (ACD), age, anterior chamber angle, and pupillary diameter measurements were evaluated with univariate and multivariate regression analyses. The relationship between iris bowing and pupil diameter was largely linear, with three dynamic patterns observed: (1) convex-to-convex (iris remains convex in dark and light); (2) concave-to-convex (iris changes from concave to convex from light to dark); and (3) concave-to-concave (iris remains concave in dark and light). All the subjects with narrow angles had convex-to-convex anatomy, although 43% of the subjects with open angles also demonstrated this pattern. These individuals were older and had shorter axial length (both with P < 0.001). Older age (r = -0.352, P = 0.001), smaller ACD (r = 0.382, P < 0.001), and smaller difference in angle opening distance in light and dark (r = 0.472, P < 0.001) were associated with smaller differences in iris bowing in the light and dark. ACD and iris bowing were independently associated with anterior chamber angle width. Independent of ACD, iris bowing is an important biometric parameter that determines angle width. Investigation of iris dynamics may offer a new perspective in understanding the risk and mechanism of primary angle closure.

FIT biopsy for conjunctival squamous cell carcinoma with extensive intraocular invasion

Dear Editor, Ocular surface squamous neoplasia (OSSN) [conjunctival intraepithelial neoplasia, carcinoma in situ, and invasive squamous cell carcinoma (SCC)] are the most common conjunctival malignancy in the United States, occurring with the incidence of 0.03 cases per 100,000 persons. While OSSN can be locally aggressive, intraocular involvement is infrequent [1, 2]. Histopathologic confirmation of intraocular invasion can be obtained through various diagnostic techniques. Herein, we present a patient with extensive intraocular involvement by SCC, diagnosed with the aid of biopsy with a 25-gauge aspiration-cutter [Finger iridectomy technique (FIT)]. A 73-year-old woman presented with a white, vascular, dome-shaped, nasal limbal lesion, which extended onto adjacent inferonasal right cornea (Fig. 1a). A high-frequency ultrasound biomicroscopy showed no anterior chamber involvement [3]. Excisional biopsy with cryotherapy was performed. Histopathology showed well-differentiated keratinizing SCC (Fig. 1b), with approximately 40% Ki67 proliferation marker labelling index, extending to lateral, but not to deep surgical margins. The patient underwent a course of topical mitomycin-C (0.02%) and was followed closely. Two months after the surgery the epithelial tumour recurred in the region adjacent to the primary site, and the patient had a second course of mitomycin-C. A month later, she presented complaining of pain in her eye. Marked enlargement of conjunctival tumour was noted, associated with increased intraocular pressure, anterior chamber cells, and a mass in the nasal anterior chamber angle (Fig. 2a). The intraocular lesion was biopsied using the FIT. Briefly, A 25-gauge aspiration-cutter (vitrector) was introduced under sodium hyaluronate 1% and through a 1-mm peripheral clear corneal incision. Aspiration (600 mmHg) cutting (300 cpm) was performed to obtain specimens for cytology and histopathology. The detailed methodology of this technique is described in the referenced text [4]. Cytopathologic evaluation of biopsy material revealed dysplastic keratinizing squamous cells and tissue consistent with intraocular invasion by SCC (Fig. 2b). In the course of the next several weeks, the patient developed increasing right eye pain, vitreous debris, and serous retinal detachment. She was advised to undergo orbital exenteration for local tumour control. Histopathologic evaluation of the orbital exenteration specimen revealed well-differentiated SCC. The tumour cells involved the anterior orbit, entered the eye via anterior emissary canals, and infiltrated the anterior chamber angle, Graefes Arch Clin Exp Ophthalmol (2008) 246:467–469 DOI 10.1007/s00417-007-0712-4

Anterior eye focusing of peripheral ultraviolet and visible radiation albedo

Concern about short‐ and long‐term ultraviolet radiation (particularly UVB) damage to the eye has led to increased research in this area. Numerous studies have confirmed the pathogenic enhancing roles of reflected ultraviolet (UV) and visible radiation in our environment. There is concern that conventional sunglasses do not protect the eye adequately from reflected rays (albedo), especially on the lateral aspect, from behind and from below. Using eye models and computer ray tracing methods, the pathways of oblique rays incident at the temporal peripheral cornea have been plotted by Maloof, Ho and Coroneo.1 These rays are refracted and focused and theoretically can result in up to 20 times the concentration of incident irradiance at the nasal anterior chamber angle and nasal equatorial cortex of the crystalline lens. The purpose of this study was to determine the limits of angular subtense of the incident peripheral light which is refracted in this manner in human subjects and to investigate the relation between corneal shape and certain ocular parameters to the limits. A statistically significant positive correlation was found between temporal entrance angle and anterior chamber depth (r = 0.70, P< 0.0006). The entrance angle ranged from 15 degrees to 30 degrees and was located 10 degrees to 45 degrees posterior to the coronal plane. Our results support Maloof and colleagues' predictions for the implication of focused peripheral UV and high intensity visible radiation in the pathogenesis of pterygium and cortical cataract and emphasise the need for lateral eye protection in conditions of high ultraviolet albedo.