Andy C. O. Cheng

Surgical Anatomy of the Chinese Orbit

Purpose: To describe the metric measurements and normal anatomic variants in Chinese bony orbits. Methods: Orbital osteology was studied in 194 orbits from 97 Chinese skulls. Morphologic observations and metric measurements were made to elucidate the variations of the orbital bony anatomy and to localize important fissures and foramina within the orbit. Sexual dimorphism and side asymmetry of orbital features were analyzed. Results were then compared with data from other populations. Results: The details of the orbital osteology in Chinese are described. Most orbital features show anatomic variations in terms of their existence, quantity, and location. Anatomic variants including quadruple and extrasutural posterior ethmoidal foramen are described for the first time. Side asymmetry and sexual dimorphism (male larger than female) are demonstrated in some orbital features. Compared with white and American populations, orbital measurements are generally smaller in Chinese, probably related to their smaller orbital size. Conclusions: The Chinese orbital osteology demonstrates considerable variability. The newly described anatomic variants found on the posterior ethmoidal foramen may affect surgical procedures related to the medial orbital wall. Sexual dimorphism and ethnic variations of the orbital bony anatomy may affect surgical approach to orbital diseases in different populations.

Quality of Reporting of Key Methodological Items of Randomized Controlled Trials in Clinical Ophthalmic Journals

Purpose: To evaluate the reporting quality of key methodological items in randomized controlled trials (RCTs) in four general clinical ophthalmology journals.Methods: The reporting of 11 key methodological items in RCTs published in American Journal of Ophthalmology, Archives of Ophthalmology, British Journal of Ophthalmology and Ophthalmology in the year 2005 was assessed. Results : Sixty-seven eligible RCTs were assessed and the mean number of items reported was 6.3 per RCT. No significant difference in the mean number of items reported was found between the four journals (P = 0.20). The most frequently reported item was ethics approval and informed consent (97.0%), followed by masking status (85.1%), description of withdrawals (76.1%), adverse events (73.1%), and intention-to-treat analysis (71.6%). Details on sequence generation, randomization restriction, allocation concealment, allocation implementation, patient flow diagrams, and sample size calculation were reported in < 50% of the RCTs assessed. Both sample size and page length of the RCTs correlated with the number of methodological items reported (P = 0.024 and P = 0.008, respectively). Conclusions: Similar to other specialties, rooms for improvement exist in the reporting of key methodological items of RCTs in clinical ophthalmic journals. Stricter adoption of the CONSORT statement might enhance the reporting quality of RCTs in ophthalmic journals.

Quantitative assessment of optic nerve head morphology and retinal nerve fibre layer in non- arteritic anterior ischaemic optic neuropathy with optical coherence tomography and confocal scanning laser ophthalmoloscopy

Background/aims: To compare the optic disc parameters between patients with non-arteritic anterior ischaemic optic neuropathy (NAION) and normal controls, using optical coherence tomography (OCT) and Heidelberg Retinal Tomograph III (HRT), and to evaluate the structure–function relationship in NAION eyes. Methods: Both eyes of 22 patients with typical unilateral NAION of ⩾6 months’ duration and 52 eyes from 52 randomly selected normal subjects underwent Humphrey visual field (HVF) examination and measurement of optic disc and retinal nerve fibre layer thickness (RNFLT). Results: For the NAION-affected eyes, NAION fellow eyes and normal controls, the ocular magnification-corrected OCT disc areas were respectively 1.849 (SD 0.343) mm2, 1.809 (0.285) mm2 and 1.964 (0.386) mm2; the cup areas were 0.246 (0.187) mm2, 0.172 (0.180) mm2 and 0.469 (0.332) mm2. On HRT, the disc areas were 2.11 (0.38) mm2, 2.06 (0.40) mm2 and 2.16 (0.42) mm2; and the cup areas were 0.28 (0.34) mm2, 0.25 (0.18) mm2 and 0.48 (0.32) mm2. On both OCT and HRT, the cup areas and cup–disc area ratios (CDAR) of both eyes of NAION patients were significantly smaller than controls (p⩽0.01), but the disc areas were not (p⩾0.21). There was a significant correlation between HVF mean deviation and OCT RNFLT (r = 0.44, p = 0.04) but not with HRT RNFLT (p = 0.30) in NAION-affected eyes. Conclusion: NAION patients have smaller optic cups and CDARs in both eyes compared with controls. A larger sample size is necessary to demonstrate if disc size affects the risk of developing NAION. The NAION-affected eyes’ OCT RNFLT correlated with HVF mean deviation but the HRT RNFLT did not.

Characterization and localization of the supraorbital and frontal exits of the supraorbital nerve in Chinese: an anatomic study.

Purpose: To elucidate the characteristics and location of the supraorbital and frontal exits of the supraorbital nerve in Chinese skulls and to compare these findings with other ethnic populations. Methods: The anatomy of the supraorbital nerve exits was studied in 97 adult Chinese skulls (194 orbits). The characteristics and location of the supraorbital nerve exits were determined. Analyses were performed to compare differences between sexes and sides. Data were then compared with those of the other populations. Results: Supraorbital exits were found in all 194 orbits. Among these, 89 (45.9%) were foramina. Frontal exits were found in 69 of the 194 (35.6%) orbits in which 18 were foramina (9.3%). The location of the supraorbital exits showed a skewed distribution toward the medial aspect of the superior orbital rim. The median distance between the supraorbital exits and the facial midline was 24.56 mm. Eighty percent of the supraorbital exits lay between 20.77 mm and 30.52 mm from the facial midline. The mean frontal exit was 7.02 mm medial to the supraorbital exits. Compared with other populations, a higher proportion of Chinese have foramina above the superior orbital rim as the exits for the supraorbital neurovascular bundle. The location of the supraorbital nerve exit is highly variable in all studied populations. Conclusions: In a significant proportion of Chinese, the supraorbital nerve exits are located toward the medial aspect of and above the superior orbital rim. Extra care should be taken during dissection around this region to avoid damage to the supraorbital nerve.

Eyes or subjects: Are ophthalmic randomized controlled trials properly designed and analyzed?

OBJECTIVE In ophthalmic randomized controlled trials (RCTs), each subject may have 2 potential data points (i.e., eyes) contributing to the clinical trial. Hence, various study designs may arise requiring different statistical tools. This study aimed to assess the appropriateness of study design, statistical tools used, and reporting of results in ophthalmic RCTs. DESIGN A systematic review of 69 ophthalmic RCTs. METHODS The study design, sample size calculation, statistical analysis, and reporting methodology of all RCTs published in 4 major general clinical ophthalmology journals in 2009 were assessed. MAIN OUTCOME MEASURES The study design of each article under review is evaluated. RESULTS The most common study design was a one-eye design (48%). Within this group, only half described the method of selecting the study eye, among which 5 chose the study eye by random selection. In the remaining trials, there were paired-eye design (13%), subject design (19%), and two-eye design (19%). Among the 13 two-eye design studies, 4 allocated both eyes of the subject to the same group, 4 allocated the eyes to different groups, and 4 did not restrict the allocation. None of these studies adjusted for the clustering effect in sample size calculation. Only 5 studies used statistical methods adjusting for nonindependence. CONCLUSIONS There is currently substantial heterogeneity in the quality among published ophthalmic RCTs in terms of proper use of study design, sample size calculation, randomization method, and statistical tools. Future ophthalmic researchers are suggested to consult a statistician and to follow some guidelines such as the CONSORT statement when performing an RCT to improve further the quality of clinical trial.

Limited nasal septoplasty by ophthalmologists during endonasal dacryocystorhinostomy: is it safe?

Purpose: Significant deviated nasal septum (DNS) may preclude the performance of endonasal dacryocystorhinostomy (DCR). The purpose of this study was to investigate the outcomes of limited nasal septoplasty in tackling signficant DNS performed by trained ophthalmologists during endonasal DCR. Methods: In this retrospective interventional case series, the records of all patients requiring limited nasal septoplasty for significant DNS during endonasal DCR at 2 tertiary ophthalmic centers in Hong Kong during January 2006 to December 2007 were reviewed. Surgical outcomes, demographic factors, and intraoperative and postoperative details were recorded and analyzed. Results: A total of 25 septoplasties were performed in 25 patients (total of 28 DCR). After the nasal septoplasty, all nasal cavities had better exposure of the surgical site allowing completion of the endonasal DCR. At the latest follow-up, the anatomical and functional success rates of the endonasal DCR were both 96.4% (27/28). In one patient, septoplasty was complicated by asymptomatic mucosal adhesion between the lateral nasal wall and the nasal septum. Conclusions: In the hands of trained ophthalmic lacrimal surgeons, limited nasal septoplasty is an effective and safe procedure during endonasal DCR, allowing better exposure of the surgical field in patients with significant DNS.

Late-onset occult cerebrospinal fluid leakage after orbital exenteration.

Orbital exenteration can be complicated by cerebrospinal fluid leakage, mostly during surgery. Late-onset cerebrospinal fluid leakage that occurs years after the initial orbital exenteration is rare. The authors report a case of cerebrospinal fluid leakage that occurred 4 years after orbital exenteration that was not due to tumor recurrence. The leakage was managed successfully by the application of cyanoacrylate tissue glue. No complication was encountered.

The Pathogenesis of Nonarteritic Anterior Ischemic Optic Neuropathy.

AbstractAlthough nonarteritic anterior ischemic optic neuropathy (NAION) is known to occur as a result of ischemic insult to the anterior portion of the optic nerve, its etiology and pathogenesis remain elusive. Because NAION is a nonfatal condition, acute, postmortem histopathologic analysis has never been undertaken. Animal models of NAION have been created with the use of an iodinated derivative of fluorescein, rose bengal. When rose bengal is stimulated with the use of a frequency-doubled neodymium-Yttrium aluminium garnet (YAG) laser diode, vascular endothelial damage may be induced in a precise and focal manner, within the anterior optic nerve. Primate and nonprimate animal models of NAION differ from the human pattern of NAION in the duration of the disease course, as well as the anatomy. The rat lamina cribrosa contains a differing connective tissue structure, which may result in a differing pathogenesis of ischemic insult. Optic disk swelling resolves within 5 days in rats and 14 days in primates; in humans, it is known to persist for up to 6 weeks. Animal models have nonetheless enabled a deeper understanding of the underlying pathologic processes in NAION.

Ophthalmic Randomized Controlled Trials Reports: The Statement of the Hypothesis

PURPOSE To evaluate whether the ophthalmic randomized controlled trials (RCTs) were designed properly, their hypotheses stated clearly, and their conclusions drawn correctly. DESIGN A systematic review of 206 ophthalmic RCTs. METHODS The objective statement, methods, and results sections and the conclusions of RCTs published in 4 major general clinical ophthalmology journals from 2009 through 2011 were assessed. The clinical objective and specific hypothesis were the main outcome measures. RESULTS The clinical objective of the trial was presented in 199 (96.6%) studies and the hypothesis was specified explicitly in 56 (27.2%) studies. One hundred ninety (92.2%) studies tested superiority. Among them, 17 (8.3%) studies comparing 2 or more active treatments concluded equal or similar effectiveness between the 2 arms after obtaining insignificant results. There were 5 noninferiority studies and 4 equivalence studies. How the treatments were compared was not mentioned in 1 of the noninferiority studies. Two of the equivalence studies did not specify the equivalence margin and used tests for detecting difference rather than confirming equivalence. CONCLUSIONS The clinical objective commonly was stated, but the prospectively defined hypothesis tended to be understated in ophthalmic RCTs. Superiority was the most common type of comparison. Conclusions made in some of them with negative results were not consistent with the hypothesis, indicating that noninferiority or equivalence may be a more appropriate design. Flaws were common in the noninferiority and equivalence studies. Future ophthalmic researchers should choose the type of comparison carefully, specify the hypothesis clearly, and draw conclusions that are consistent with the hypothesis.

Sub-Tenon's block versus topical anaesthesia for cataract surgery.

We read with great interest the article by Ruschen et al comparing patient satisfaction during cataract surgery with sub-Tenon’s block (STB) versus topical anaesthesia (TOP).1 The authors concluded that in the setting of day case cataract surgery, patients reported significantly higher satisfaction scores with STB than TOP. We would like to raise two issues for discussion. Firstly, the lower satisfaction score in the TOP group may only reflect a suboptimal TOP that was given in the current study and may not be generalisable to other …