Caustics and wavefronts produced by multiple refraction-reflections through plane-parallel plates.

We study the formation of caustics and wavefronts produced by multiple refraction-reflections through a plane-parallel transparent plate, assuming a point source placed at an arbitrary position along the optical axis. The caustic surfaces are obtained by using the envelope's method. Subsequently, the wavefronts are directly related to the involutes, which are associated with the envelopes for all the rays. Hence by using the Malus-Dupin theorem, we obtain their respective wavefronts produced by multiple refraction-reflections through a plane-parallel transparent plate. On the other hand, we implement Huygens' principle to obtain the wavefronts leaving the plate after undergoing multiple reflections inside the plate, which we have called zero-distance phase wavefronts. Finally, we establish the correspondence between the wavefronts obtained by Huygens' principle and the involutes associated with caustic surfaces; they are brought in coincidence assuming parallel curves from each other.

Temporal Approach, Digitally Assisted Phacovitrectomy in a Patient with Severe Kyphosis due to Axial Spondyloarthritis.

PURPOSE: To describe a temporal approach, digitally assisted phacovitrectomy in a patient with severe kyphosis due to axial spondyloarthritis. Case Report. A 70-year-old male patient with proliferative diabetic retinopathy with vitreous hemorrhage and cataract and ankylosing spondylitis with severe kyphosis. A temporal approach, digitally assisted 25 G phacovitrectomy was performed with a Constellation platform and the NGENUITY visualization system. The Trendelenburg position was utilized. CONCLUSION: A temporal approach, digitally assisted phacovitrectomy may be used in select cases of severe kyphosis with positive outcomes.

Primary Cancer Sites and Clinical Features of Choroidal Metastasis in Mexican Patients.

PURPOSE: To describe the primary cancer sites and clinical features of choroidal metastasis in Mexican patients. METHODS: This was a retrospective, observational, and multi-center study. Data were recollected from 6 ophthalmological hospitals in Mexico from patients with choroidal metastasis diagnosed from 2000 to 2018. RESULTS: Seventy-eight patients were studied: 43 were female and 35 were male. Mean age at presentation was 57.6 years. Overall, primary cancer sites were: 1) breast: 27 cases (34.6%); 2) lung: 19 cases (24.3%); 3) unknown: 8 cases (10.2%); 4) gastrointestinal: 7 cases (8.9%); 5) renal: 5 cases (6.4%); 6) testicular: 3 cases (3.8%); 7) ovary: 3 Cases (3.8%); 8) prostate: 2 cases (2.5%); 9) thyroid: 2 cases (2.5%); 10) carcinoid: 1 case (1.2%); and 11) multiple myeloma: 1 case (1.2%). Divided by gender, for women, the main three sites were: breast, unknown, and ovary. For men, the main three sites were: lung, gastrointestinal, and testicular. Oldest cases were breast cancer (87 and 85 years); youngest cases were testicular (23 and 25 years). Solitary lesions were observed in 56 cases (71.7%); multiple lesions were observed in 22 cases (28.2%). Forty-two cases had a white or yellowish color, while 6 cases presented an orange color. CONCLUSION: Primary cancer sites and clinical features of choroidal metastasis in Mexican patients show important differences from other populations previously studied, mainly the presence of a higher proportion of gastrointestinal and renal cancer, as well as higher incidence of ovarian and testicular cancer. These types of cancer, although not as common as breast or lung, need to be taken into account when studying Mexican patients living abroad.

Oxymetazoline: reduction of subconjunctival hemorrhage incidence after intravitreal injections.

OBJECTIVE: Subconjunctival hemorrhage (SCH) is an important minor side effect that might affect patient compliance to antivascular endothelial growth factor (anti-VEGF) intravitreal injection treatment (IVI). We sought to compare SCH incidence and pain score responses after topical oxymetazoline in naïve patients undergoing a single IVI of ranibizumab for diabetic macular edema. METHODS: Prospective, randomized, double-blinded, single centre study. One hundred two patients naïve to anti-VEGF were assigned to receive either topical oxymetazoline or placebo 30 minutes before IVI. SCH incidence and area were measured by slit lamp 24 hours after, and pain was evaluated 5 minutes and 24 hours after. RESULTS: SCH incidence was reported on 72% in control group versus 51% in oxymetazoline group (p = 0.037). Mean size of SCH was 16.82 mm2 in control group versus 12.55 mm2 in oxymetazoline group (p = 0.394). Prevalence of local pain in the overall study population was 60%. No significant statistical difference was achieved between groups 5 minutes or 24 hours after IVI in either pain scale evaluation. CONCLUSION: Administration of topical oxymetazoline 30 minutes before IVI is a single, harmless, cost-effective intervention that decreases the incidence of subconjunctival hemorrhage. This may considerably improve patient treatment satisfaction and promote compliance to IVI therapy.