Reduction In Anterior Chamber Depth Research Articles

Beyond the Blur: Clinical Outcomes of Nd: YAG Laser Posterior Capsulotomy Intraocular Pressure, Refraction, Anterior Chamber Depth, and Macular Thickness

Background: Nd: YAG laser posterior capsulotomy is a commonly performed procedure to treat posterior capsular opacification following cataract surgery. While the procedure is known to effectively improve visual acuity, its potential impact on Intraocular Pressure (IOP), refraction, Anterior Chamber Depth (ACD), and macular thickness remains a subject of debate. This study aims to investigate the effects of Nd: YAG laser posterior capsulotomy on these ocular parameters. Methods: This study was designed as a prospective analysis conducted at a tertiary eye care center on patients who underwent Nd: YAG laser posterior capsulotomy between January 2020 and December 2020. Preoperative and postoperative measurements of IOP, refraction, ACD, and macular thickness were collected and compared. Statistical analyses were performed using paired t-tests, and p-values<0.05 were considered statistically significant. Results: A total of 30 eyes from 25 patients (mean age, 65.4±8.2 years) were included in the analysis. Following Nd: YAG laser posterior capsulotomy, the mean IOP from 15.2±2.3 mmHg to 17.0±2.7 mmHg (p<0.001). The refractive status showed a mean myopic shift of -0.35±0.16 diopters (p<0.001,). Additionally, there was a statistically significant reduction in ACD from 3.15±0.42 mm to 2.90±0.37 mm (p=0.003,). However, there was no statistically significant change in macular thickness after the procedure (p=0.287). Conclusion: Nd: YAG laser posterior capsulotomy leads to a mild but statistically significant increase in IOP and a small myopic shift in refraction. Additionally, the procedure results in a decrease in ACD but does not significantly affect macular thickness. Ophthalmologists should consider these effects when performing Nd: YAG laser posterior capsulotomy and carefully monitor patients postoperatively.

Clinical Outcomes of Nd: YAG Laser Posterior Capsulotomy: Impact on Intraocular Pressure, Refraction, Anterior Chamber Depth, and Macular Thickness

Background: Nd: YAG laser posterior capsulotomy is a commonly performed procedure to treat posterior capsular opacification following cataract surgery. While the procedure is known to effectively improve visual acuity, its potential impact on intraocular pressure (IOP), refraction, anterior chamber depth (ACD), and macular thickness remains a subject of debate. This study aims to investigate the effects of Nd: YAG laser posterior capsulotomy on these ocular parameters. Methods: This study was designed as a prospective analysis conducted at a tertiary eye care center on patients who underwent Nd: YAG laser posterior capsulotomy at a tertiary eye care center between January 2020 and December 2020. Preoperative and postoperative measurements of IOP, refraction, ACD, and macular thickness were collected and compared. Statistical analyses were performed using paired t-tests, and p-values <0.05 were considered statistically significant. Results: A total of 30 eyes from 25 patients (mean age, 65.4 ± 8.2 years) were included in the analysis. Following Nd: YAG laser posterior capsulotomy, the mean intraocular pressure (IOP) increased from 15.2 ± 2.3 mmHg to 17.0 ± 2.7 mmHg (p < 0.001). The refractive status showed a mean myopic shift of -0.35 ± 0.16 diopters (p < 0.001,). Additionally, there was a statistically significant reduction in anterior chamber depth (ACD) from 3.15 ± 0.42 mm to 2.90 ± 0.37 mm (p = 0.003,). However, there was no significant change in macular thickness after the procedure (p = 0.287). Conclusion: Nd: YAG laser posterior capsulotomy leads to a mild but statistically significant increase in IOP and a small myopic shift in refraction. Additionally, the procedure results in a decrease in ACD but does not significantly affect macular thickness. Ophthalmologists should consider these effects when performing Nd: YAG laser posterior capsulotomy and carefully monitor patients postoperatively.

Differences in corneal and anterior segment morphology between diabetic vs. healthy children and adolescents: a systematic review and meta-analysis.

To compare corneal and anterior segment morphology among children and adolescents with and without diabetes. PubMed, Embase and Scopus databases were systematically searched. Studies that were observational in design were considered. Included studies should have been done in young children and/or adolescents and compared relevant outcomes of interest based on the diabetic status. The outcomes of interest were related to corneal morphology, morphology of lens, as well as important characteristics of anterior segment such as depth, pupillary diameter, intra-ocular pressure and axial length. The pooled effect sizes were reported as weighted mean difference (WMD). STATA software was used for statistical analysis. The meta-analysis included 17 studies. Diabetic children had lower corneal endothelial cell density (cells/mm2) (WMD -215.7, 95% CI: -406.5, -24.9), higher central corneal thickness (µm) (WMD 12.66, 95% CI: 5.47, 19.84), higher lenticular thickness (mm) (WMD 0.25, 95% CI: 0.13, 0.36) and density (WMD 3.02, 95% CI: 2.23, 3.81) than non-diabetic children. The anterior chamber depth (mm) (WMD -0.17, 95% CI: -0.24, -0.09) and pupillary diameter (mm) (WMD -0.61, 95% CI: -1.12, -0.10) was significantly reduced in diabetic children, compared to non-diabetic children. No differences in the corneal curvature, corneal diameter, spherical equivalent, intra-ocular pressure, axial length, tear film breakup time and Schirmer test were noted among diabetic and non-diabetic children. Significant structural changes in cornea and lens along with reduction in anterior chamber depth and pupillary diameter were found. These morphological changes may be indication for early and prompt management and underscore the need for more advanced ophthalmological evaluation techniques, in addition to routine examination.

Parasympathetic innervation of emmetropization

Emmetropization is affected by the temporal parameters of visual stimulation and the spectral composition of light, as well as by autonomic innervation. The goal of the current experiments is to test the hypothesis that different types of visual stimulation interact with ocular innervation in the process of emmetropization. For that, selective lesions of the autonomic nervous system were performed in chickens: involving transection of parasympathetic input to the eye from either the ciliary ganglion, innervating accommodation and pupil responses (CGX; n = 32), or pterygopalatine ganglion, innervating choroidal blood vessels and cornea (PPGX; n = 26). After 1 week of recovery, chicks were exposed to sinusoidally modulated light (3 days, 2 Hz, 680 lux) that was either achromatic (black to white [RGB], or black to yellow [RG]), or chromatic (blue to yellow [B/Y] or red to green [R/G]). Exposure to light stimulation was followed by ocular biometry (Lenstar and a Hartinger refractometer). Surgical conditions revealed a small reduction in anterior chamber depth with CGX but no other significant changes in ocular biometry/refraction under standard light conditions. With RGB achromatic stimulation, CGX eyes produced an effect on ocular components, with a further reduction in anterior chamber depth and an increase in vitreous chamber depth, while RG stimulation showed no effect. No effect was detected in PPGX under both achromatic protocols. With chromatic stimulation, CGX with R/G modulation increased eye length, while PPGX with B/Y modulation decreased eye length. We conclude that the two different types of parasympathetic innervations have antagonistic effects on eye growth and the anterior eye when challenged with the appropriate stimulus, with possible implications for the role of choroidal blood flow in emmetropization.

Anterior chamber depth measurement before and after photorefractive keratectomy. Comparison between IOLMaster and Pentacam.

an accurate measurement of anterior chamber depth (ACD) both in eyes that underwent corneal refractive surgery (CRS) and in eyes that did not, can be crucial, as in case of intraocular lens (IOL) calculation in eyes that need to undergo cataract extraction, or during the evaluation of glaucomatous patients. The aim of this nonrandomized retrospective case series was to measure anterior chamber depth (ACD) before and after photorefractive keratectomy (PRK), comparing a rotating Scheimplfug camera (RSC) and a partial coherence interferometer (PCI). 125 right eyes of 125 patients were examined. ACD was measured with RSC and a PCI preoperatively and 1, 3 and 6 months postoperatively. The results were analyzed using Friedman and ANOVA test for repeated measures, Wilcoxon test, Pearson and Bland-Altmann correlation. Both instruments showed an ACD decrease after CRS. The mean preoperative difference in ACD between the two instruments was 0.11 ± 0.11 (range: -0.07 mm to 0.73 mm) (p < 0.05) (r = 0.92). The mean difference in ACD reduction between the two instruments was: 0.08 ± 0.11 (range: -0.35 to 0.39 mm) (p < 0.05, r = 0.93) at 1 month; 0.13 ± 0.11 (range: -0.09 mm to 0.48 mm) (p < 0.05, r = 0.93) at 3 months; 0.14 ± 0.15 (range: -0.16 to 0.82 mm) (p < 0.05) (r = 0.87), at 6 months. The ACD decrease shown with both instruments suggests the presence of anterior segment remodeling after PRK. RSC measurements were larger than PCI ones, both before and after PRK.

Evaluation of anterior segment parameters in pars plana vitrectomy and silicone oil injection

Purpose The aim of this study was to compare the changes in anterior segment parameters induced by pars plana vitrectomy (PPV) and silicone oil injection in phakic and pseudophakic eyes.Patients and methods This is a prospective comparative study that included 40 eyes with rhegmatogenous retinal detachment that underwent vitrectomy and silicone oil injection. They were divided equally into two groups. Group 1 included phakic eyes and group 2 included pseudophakic eyes. Anterior segment parameters were documented by using a CSO Camera (Costruzione Strumenti Oftalmici) before and 1 month after surgery. The changes in the following parameters were compared between the two groups: anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), central corneal thickness (CCT), corneal volume (CV), horizontal anterior chamber diameter, and surgically induced astigmatism.Results At 1 month postoperatively, in group 1, there was a significant decrease in the mean of ACA and ACV as compared with the preoperative values (P=0.024 and 0.011, respectively). In group 2, there was a significant decrease in the 1-month postoperative mean of ACD, ACA, and ACV as compared with the preoperative values (P=0.021, <0.0001 and 0.015, respectively) and a significant increase in the mean of CCT and CV values (P<0.0001 and 0.002, respectively). In group 2, there was more reduction in ACD, less reduction in ACA, and higher increase in CCT and CV as compared with group 1 (P=0.021, 0.001, <0.0001, and 0.023, respectively).Conclusion The presence of the crystalline lens acts as a barrier which decreases the changes in the anterior segment parameters and improves the functional outcome following PPV and silicone oil injection as compared with pseudophakia. Therefore, it may be useful to stabilize the anterior segment in patients with PPV and silicone oil injection.

Variation of accommodative process and anterior chamber parameters in diabetic patients

PurposeChronic hyperglycemia is responsible for vascular and neurodegenerative retinal changes in diabetic patients. However, other eye structures have been also associated with changes, such as corneal biomechanics and lens thickness.The author's objective was to analyze the accommodative process – crystalline structural change and pupillary diameter based on Anterior Segment Optical Coherence Tomography (AS‐OCT).MethodsProspective case‐control study. The anterior chamber parameters were studied using AS‐OCT. The monocular accommodative process was obtained with different Dioptric Powers (0 D, 2.5 D, 5 D and 7 D – lens integrated in the OCT software) in both controlled photopic and scotopic conditions. 2 groups have been analyzed: group 1 with type 2 diabetic patients and group 2 with healthy‐controls. Measurements of anterior chamber depth (ACD), lens vault (LV), pupillary diameter (PD) and iris thickness (IT) were obtained.ResultsA total of 71 patients were evaluated (group 1 − n = 36; group 2 – n = 35). The mean age was 69.15 ± 5.55 years. Diabetic patients have showed the basal highest LV and lowest ACD values, with statistically significance (p &lt; 0.05). In highest accommodative power, group 2 has experimented a significant reduction in ACD, ACA and PD (p &lt; 0.05). The LV change has not proved important in the process. Group 1 has showed a significant response in scotopic conditions, even with a lower response with the highest accommodative stimuli compared to group 2.ConclusionsThe accommodative process is impaired in diabetic patients, with a significant difference in pupillary response more than in lens vault. This could be important to explain the importance of the anterior segment of crystalline in accommodation. Further studies will be necessary to clarify the DM effects on these parameters.

Distribution of axial length, anterior chamber depth, and corneal curvature in an aged population in South China.

BackgroundOcular biometry is important for preoperative assessment in cataract and anterior segment surgery. The purpose of this study was to investigate normative ocular biometric parameters and their associations in an older Chinese population.MethodsThis was a cross-sectional observational study. From 2013 to 2014, we recruited inhabitants aged 50 years or older in Guangzhou, China. Among 1,117 participants in the study, data from 1,015 phakic right eyes were used for analyses. Ocular parameters including axial length (AL), anterior chamber depth (ACD), and corneal curvature (K) were measured using an IOL Master.ResultsThe mean AL, ACD, and K were 23.48 mm [95 % confidence interval (CI), 23.40–23.55], 3.03 mm (CI, 3.01–3.05), and 44.20 mm (CI, 44.11–44.29), respectively. A mean reduction in ACD with age was observed (P = 0.002) in male subjects but not in female subjects (P = 0.558). Male subjects had significantly longer ALs (23.68 mm versus 23.23 mm, P < 0.001), deeper ACDs (3.13 mm versus 2.95 mm, P < 0.001), and flatter Ks (43.85D versus 44.50 D, P < 0.001) than female subjects. Eyes with axial elongation had a flatter cornea (r = −0.437, P < 0.001) and a deeper anterior chamber (r = 0.652, p < 0.001). The ACD was correlated with K (r = −0.266, P < 0.001).ConclusionsThese data provide normative values for AL, ACD, and K using the IOL Master for a population in South China. The AL in this Chinese cohort was greater than that observed in the Singaporean Chinese but smaller than that observed in Malaysia and for Caucasians. The Chinese have a shallower ACD than some other racial groups. Age and sex were the most consistent predictors of ocular biometry in the older population from South China.

Influence of Gravity on Ocular Lens Position.

We determined whether human ocular lens position is influenced by gravity. Anterior chamber depth (ACD) and lens thickness (LT) were determined with a Haag-Streit Lenstar LS900 for right eyes of participants in two age groups, with a young group of 13 participants aged 18 to 21 years (mean, 21 years; SD, 1 year) and an older group of 10 participants aged 50 to 63 years (mean, 58 years; SD, 4 years). There were two sessions for each participant separated by at least 48 hours, with one session for the usual upright head position and one session for a downwards head position. In a session, testing was done for minimum accommodation followed by testing at maximum accommodation. A drop of 2% pilocarpine nitrate was instilled, and testing was repeated after 30 minutes under minimum and maximum accommodation conditions. Gravity, manipulated through head posture, affected ACD for young adult and older adult groups but mean effects were only small, ranging from 0.04 to 0.12 mm, and for the older group required the instillation of an accommodation-stimulating drug. Gravity had a weakly significant effect on LT for the young group without accommodation or a drug, but the effect was small at 0.04 ± 0.06 mm (mean ± SD, P = 0.04). There is a small but real effect of gravity on crystalline lens position, manifested as reduction in ACD at high levels of accommodative effort with the head in a downwards position. This provides evidence of the ability of zonules to slacken during strong accommodation.

Anterior Segment Changes Produced in Response to Long-Term Overnight Orthokeratology

Purpose: To evaluate the effect of overnight orthokeratology (OK) on anterior chamber depth (ACD), posterior radius of corneal curvature (PRCC) and axial length (AL) over one year.Methods: In this prospective longitudinal study, measurements were made in 34 right eyes of 34 subjects at baseline, 15 days, 1 and 12 months after starting OK treatment. ACD and PRCC measurements were obtained using a Pentacam system and AL was measured using an IOL-Master. ACD and PRCC were measured along the horizontal and vertical meridians at 1 mm intervals. These measurements were expressed as the distance from the center in the nasal (N), temporal (T), superior (S) and inferior (I) directions.Results: A significant reduction in ACD was observed in both meridians during treatment. PRCC flattened significantly in the (T) direction after 15 d (1 mm, p < 0.05), at the corneal center after 15 d (p < 0.01), in the (T) direction after 1 month (1 mm, p < 0.05), in the (S) direction after 12 months (1 mm p < 0.05), in the (N) direction after 12 months (1 mm p < 0.05), in the (N) and (T) directions after 12 months (3 mm, p < 0.05) and in the (T) direction after 12 months (4 mm p < 0.05), at the corneal center after 12 months (p < 0.01). AL was significantly reduced during treatment (p < 0.05).Conclusions: A long period of OK reduces ACD and AL and changes PRCC.

Vergence analysis reveals the influence of axial distances on accommodation with age and axial ametropia

Despite numerous investigations, the aetiology and mechanism of accommodation and presbyopia remains equivocal. Using Gaussian first-order ray tracing calculations, we examine the contribution that ocular axial distances make to the accommodation response. Further, the influence of age and ametropia are also considered. The data show that all changes in axial distances during accommodation reduce the accommodation response, with the reduction in anterior chamber depth contributing most to this overall attenuation. Although the total power loss due to the changes in axial distances remained constant with increasing age, hyperopes exhibited less accommodation than myopes. The study, therefore, enhances our understanding of biometric accommodative changes and demonstrates the utility of vergence analysis in the assessment of accommodation.

Effect of a Suction Device for Femtosecond Laser on Anterior Chamber Depth and Crystalline Lens Position Measured by OCT

To investigate the position and stability of the crystalline lens after application of a suction device containing a contact lens and a vacuum unit for the treatment of presbyopia using a femtosecond laser. Twenty presbyopic (44.4+/-4.3 years) and 5 pre-presbyopic patients (31.6+/-3.8 years) were included. The anterior chamber depth, along with the position of the lens, was investigated before and after application of the suction device with optical coherence tomography (Visante OCT; Carl Zeiss Meditec AG). The type of suction device is routinely used for femtosecond LASIK with the VisuMax laser (Carl Zeiss Meditec AG). In both groups, there was a reduction in anterior chamber depth of approximately 700 microm due to the suction device, and the anterior chamber depth achieved was stable. The maximum variation was 160 microm. At the periphery of the crystalline lens, there were movements up to 310 microm axially and 470 microm laterally. The study proves that once the suction device has been applied, the crystalline lens is stable enough to undergo presbyopic laser therapy. However, the reduction in anterior chamber depth induced by the suction device showed significant individual variation. The exact position of the lens should therefore be measured immediately before laser surgery.

Assessing the accuracy of Orbscan II post‐LASIK: apparent keratectasia is paradoxically associated with anterior chamber depth reduction in successful procedures – response

Clinical & Experimental OphthalmologyVolume 34, Issue 1 p. 95-95 Assessing the accuracy of Orbscan II post-LASIK: apparent keratectasia is paradoxically associated with anterior chamber depth reduction in successful procedures – response Gerard Cairns PhD, Gerard Cairns PhD Department of Ophthalmology, University of Auckland, Auckland, New ZealandSearch for more papers by this authorCharles NJ McGhee PhD FRANZCO, Charles NJ McGhee PhD FRANZCO Department of Ophthalmology, University of Auckland, Auckland, New ZealandSearch for more papers by this author Gerard Cairns PhD, Gerard Cairns PhD Department of Ophthalmology, University of Auckland, Auckland, New ZealandSearch for more papers by this authorCharles NJ McGhee PhD FRANZCO, Charles NJ McGhee PhD FRANZCO Department of Ophthalmology, University of Auckland, Auckland, New ZealandSearch for more papers by this author First published: 01 February 2006 https://doi.org/10.1111/j.1442-9071.2006.01160.xRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume34, Issue1January 2006Pages 95-95 RelatedInformation

Assessing the accuracy of Orbscan II post-LASIK: apparent keratectasia is paradoxically associated with anterior chamber depth reduction in successful procedures - comment.

Assessing the accuracy of Orbscan II post-LASIK: apparent keratectasia is paradoxically associated with anterior chamber depth reduction in successful procedures - comment.

Assessing the accuracy of Orbscan II post‐LASIK: apparent keratectasia is paradoxically associated with anterior chamber depth reduction in successful procedures

To establish a relationship between the forward protrusion of the cornea (keratectasia), following successful LASIK, and anterior chamber depth. One hundred and fifteen eyes of 59 patients who had undergone Zyoptix LASIK and 39 eyes of 21 patients who had undergone PlanoScan LASIK at the Eye Institute, Centre for Refractive Surgery, Remuera, Auckland, New Zealand, were included in the study. The results of Orbscan II acquisitions, taken before and 8.3 weeks +/- 4.0 (mean +/- standard deviation) following the procedure, were analysed to determine the amount of forward protrusion of the central 2 mm diameter of the posterior surface. The apparent keratectasia was then related to the Orbscan II anterior chamber depth (ACD) measurement in a linear mixed model analysis that included 'right or left eye', 'sex', 'type of LASIK procedure', 'change in pachymetry', 'postoperative pachymetry', 'change in anterior corneal curvature', 'postoperative anterior corneal curvature', 'planned ablation depth' and 'time until follow-up' as factors and covariates. The mean +/- SD amount of keratectasia determined by Orbscan II was 22.8 +/- 26.8 microm for the Zyoptix group and 16.9 +/- 24.6 microm for the PlanoScan group. The reduction in depth of the anterior chamber was 14.7 +/- 79.3 microm for the Zyoptix group and 18.2 +/- 68.8 microm for the PlanoScan group. The mixed model analysis demonstrated strong relationships with postoperative pachymetry and change in anterior corneal curvature (P < 0.001 and P < 0.001, respectively). Furthermore, the statistical model showed a marked significant difference in the Orbscan II assessment of keratectasia and change in ACD (P < 0.001). Using the Orbscan II device, the forward protrusion of the posterior corneal surface appears to coincide with a paradoxical reduction in depth of the anterior chamber. Although the keratectasia found in this study is accompanied by thin postoperative corneas and larger central pachymetry change, the contradictory decrease in anterior chamber depth creates uncertainty of measurement, and of ectasia as a mechanism of regression.

Ultrasound biomicroscopic changes during accommodation in eyes with accommodating intraocular lenses

To document ciliary body constriction and movement with the Crystalens AT-45 intraocular lens (IOL) (eyeonics) using ultrasound biomicroscopy. Eye Clinic, Department of Neurological and Visual Sciences, University of Verona, Verona, Italy. Patients with no preexisting ocular conditions other than cataract who agreed to return for follow-up were considered. Twenty eyes of 14 patients with a best corrected visual acuity of 5/10 or worse and a refractive error (spherical equivalent) of +/-1.0 diopter (D) had implantation of a Crystalens AT-45 accommodating IOL. Six patients had bilateral implantation. Ultrasound biomicroscopy was performed postoperatively at 1 and 6 months. Before and during accommodation, the anterior chamber depth (ACD) was measured to assess the endothelium-IOL distance and measure the scleral-ciliary process angle to determine whether there was anterior rotation of the ciliary body. The uncorrected distance acuity, best corrected distance acuity, uncorrected near acuity, distance corrected near acuity, best corrected near acuity, and accommodative amplitude were determined. Analysis was done to determine whether there was a correlation between the accommodative amplitude and the percentage variation in the ACD and scleral-ciliary process angle. All surgical procedures were uneventful. The mean uncorrected distance acuity at 1 month was 0.8 +/- 0.14 (SD) and remained stable at 6 months. Three of 20 eyes (15%) and 8 of 20 eyes (40%) had a Jaeger acuity of J1 and J3, respectively, without additional power correction. During accommodation, the mean reduction in ACD was 0.32 +/- 0.16 mm at 1 month and 0.33 +/- 0.25 mm at 6 months. The mean narrowing of the scleral-ciliary process angle was 4.32 +/- 1.87 degrees at 1 month and 4.43 +/- 1.85 degrees at 6 months. There was a correlation between accommodative amplitude and a decrease in the ACD (r=0.404) and a decrease in scleral-ciliary process angle (r=0.773). Anterior displacement of the Crystalens IOL and corresponding anterior rotation of the ciliary body occurred during near vision. The IOL displacement and rotation were proportional to the accommodation capacity.

Ferrara intrastromal corneal ring segments for severe keratoconus.

Intrastromal Ferrara ring segments were inserted in eyes with severe keratoconus to evaluate safety and efficacy of this procedure. Intrastromal Ferrara ring segments were placed in 36 eyes of 35 patients with severe keratoconus, who were evaluated after 12 months of follow-up. All patients had highly disabling visual acuity, contact lens intolerance, and a previous indication for penetrating keratoplasty. Statistical analysis included preoperative and postoperative uncorrected visual acuity, best spectacle-corrected visual acuity, manifest refraction, anterior chamber depth, keratometry, and pachymetry. No patient had a loss of visual acuity. Uncorrected visual acuity improved in 28 eyes (77.78%) and best spectacle-corrected visual acuity improved in 29 eyes (80.56%). Spherical equivalent refraction decreased from -7.29 +/- 3.12 D to -4.80 +/- 3.04 D at 12 months after Ferrara intrastromal ring segment implantation. Corneal topography and ultrasound biomicroscopy showed corneal flattening, demonstrated by thinning of the central cornea and a reduction in anterior chamber depth. Segment decentration occurred in one eye (2.7%), asymmetric positioning of the segments in two eyes (5%), inadequate depth in two eyes (5%), migration of the segments in two eyes (5%), segment extrusion in five eyes (13.8%), conjunctivitis in one eye (2.7%), bacterial keratitis in one eye (2.7%), and hydrops in one eye (2.7%). With these early results, Ferrara intrastromal ring segments appear to be an alternative for the treatment of severe keratoconus.

Reduction in Anterior Chamber Depth Following Scleral Buckling Procedures

SummaryA reduction in anterior chamber depth was observed in 10 of 25 patients in whom scleral buckling was performed as a surgical treatment for retinal detachment. In one case this reduction was enough to precipitate angle closure glaucoma. Pre‐operative assessment of the drainage angle and the anterior chamber depth is necessary for the recognition of predisposed individuals.

Ocular dimensions and the heredity of open-angle glaucoma.

It has long been recognized that heredity plays a part in the aetiology of glaucoma. In open-angle glaucoma an autosomal recessive inheritance has been suggested (Waardenburg, 1949), but in the majority of families reported in which a high prevalence has been found, an autosomal dominant transmission seems apparent (Miller and Paterson, I962; Fransois, Heintz-de Bree, and Tripathi, I966; Francois and Heintz-de Bree, I966; FranSois, i966). The penetrance of the dominant gene appears, however, to be highly variable; Fransois and Heintz-de Bree (i966) noted a 98 per cent. penetrance in some families but admitted that in many others the penetrance was very low. On the other hand, Armaly, Monstavicius, and Sayegh (i968) suggested a multifactorial aetiology for the condition. A similar controversy exists in regard to the aetiology of angle-closure glaucoma. The influence of ocular dimensions in the aetiology of angle-closure glaucoma is well established (Priestley-Smith, 1883; Rosengren, I950; Tornquist, 1956; Lowe, I970; Storey and Phillips, 1971). Tomlinson and Leighton (1973) have considered the role of ocular dimensions in the heredity of angle-closure glaucoma in an attempt to define the importance ofindividual dimensions in the aetiology and heredity of the condition. Their results, which may favour a multifactorial determination, were discussed in the light of conflicting views concerning the heredity of that form of glaucoma. The influence ofocular dimensions on the aetiology ofopen-angle glaucoma is apparently not as great as it is in angle-closure glaucoma, but there is some evidence to show that the myopic eye may be particularly sensitive to raised intraocular pressure. Perkins and Jay (I960) reported that 22 per cent. of 205 patients with open-angle glaucoma over the age of 50 years were myopic; under the age of 50 the incidence of myopia was 37-8 per cent. A high incidence ofopen-angle glaucoma in myopic patients has been observed by Weekers, Lavergne, and Prijot (1958) and by Diaz-Dominguez (I96I, I966). A relationship between myopia and a high response of ocular tension to topical corticosteroids also appears to exist (Podos, Becker, and Morton, i966). T6rnquist and Broden (I958) and Tomlinson and Leighton (1972) have observed that eyes with open-angle glaucoma have significantly shallower anterior chambers than normal eyes. This may be a contributory factor to the development of open-angle glaucoma, as Francois, Rabaey, Neetens, and Evens (I958) found the reduction in anterior chamber depth to have more effect on the outflow of aqueous humour from the eye than any other factor considered. An investigation was carried out in which certain ocular dimensions were measured in patients with open-angle glaucoma and in their first-degree relatives. A similarity in these dimensions between the patients and relatives may explain an increased liability to the