Background and Objectives: Radial keratotomy is one of the current techniques in correction of myopia which has high prevalence in general population. The main purpose of this study was to evaluate changes in pattern and profile of corneal topography before, one week and third months after surgery. Secondary aims of this study were to record the subjective complaints and their correlation with topographic changes after surgery. Materials and Methods: In a clinical trial, comparison of corneal topography before and after RK was done in 50 eyes of 26 patients from 19/3/1997 to 20/9/2001. In all patients, routine eye examinations were performed before surgery along with determination of pattern and profile of corneal topographies (asphericity coefficient). Surgery were done under topical anesthesia with 0.2 mm diamond knife. Incision technique was as the American method with present standard nomograms. Corneal topography in first week and third months after surgery was done with special attention to central optical zone (COZ) pattern, presence of multifocality and asphericity coefficient. Patient’s complaints also were recorded.Results: The mean age of patients was 29 (18-60) years. 74% out of patients were male and 26% female. The mean duration of follow up was 10.5 months. The most common patterns of topography before surgery were asymmetric bow-tie (44%), symmetric bow-tie (40%), and spheric (8%). Corneal profile was prolate in 92% and spheric in 8% of cases. No case of oblate profile was found before surgery. Prevalent corneal patterns after surgery were regular polygonal (circular or elliptic) in 50% , Band like in 22%, and split in 28% of cases. Corneal multifocality was found in 38% of cases after surgery. Corneal profile was oblate in 94% and prolate in 6% of cases.Conclusion: Radial keratotomy induces various changes in corneal pattern and profile after surgery. Increased corneal asphericity and switching from prolate to oblate profile were noted. Multifocality in central flat zone can increase uncorrected visual acuity without considerable optical complications. Split pattern of central optic zone can cause diurnal fluctuation of vision.

In this article we investigate filters of cozero sets for real-valued continuous functions, calledcoz-filters. Much is known for z-ultrafilters and their correspondence with maximal ideals of C (X). Similarly, a correspondence will be established betweencoz-ultrafilters and minimal prime ideals of C (X). We will further notice various properties of coz-ultrafilters in relation toP-spaces and F-spaces. In the last two sections, the collection of cozultrafilters will be topologized, and then compared to the hull-kernel and the inverse topologies placed on the collection of minimal prime ideals of C (X) and general lattice-ordered groups.

When several and very different treatment modalities exist for one ailment, it usually means that none of them is generally effective or superior to others. Central retinal vein occlusion (CRVO) is a condition for which various types of management have been proposed.However, the only standard care suggested by the Central Vein Occlusion Study Group (CVOSG) is panretinal photocoagulation when the condition is complicated by iris neovascularization.

In this article we introduce the concepts of minimal prime z-, lter, essential z-, lter and r-, lter. We investigate and study the be-havior of minimal prime z-, lters and compare them with minimal prime ideals and coz-ultra, lters. We show that X is a P-space if and only if every , xed prime z-, lter is minimal prime. It is observed that if X is a @-space then X is a P-space if and only if Z[Mf ] is an r-, lter, for every f 2 C(X). The collection of all minimal prime z-, lters will be topologized and it is proved that the space of minimal prime z-, lters is homeomorphic with the space of coz-ultra, lters. Finally, it is obtained several properties and relations between the space of minimal prime z-, lters and the space of minimal prime ideals in C(X).

Central retinal vein occlusion (CRVO) occurs at the scleral outlet where the optic nerve, central retinal artery, and central retinal vein enter the eye; therefore it may be considered a "compartment syndrome" which is defined as a neurovascular compression within this confined space of scleral outlet resulting in tissue ischemia and dysfunction. Transvitreal optic neurotomy (TON) is a new surgical technique advocated for treatment of CRVO. By this procedure and providing surgical relaxation of the scleral outlet, clearing of macular edema and interaretinal hemorrhage and improved retinal blood flow may reestablish. TON may be a beneficial surgical procedure for patients with severs CRVO, via decompressing the scleral outlet and by that affecting the optic nerve and the blood supply. In addition to scleral ring relaxation, other postulated mechanisms of effect in TON include development of opticociliary vessels and increased perfusion into pre-existing opticociliary vessels. Preliminary results of TON for CRVO have demonstrated encouraging results; however these results need to be reconfirmed in a randomized clinical trial.

‎In this article‎, ‎we first introduce the concept of $z$-sets in the ring $ \mathcal{R}(L)$ of real-valued continuous functions on a completely regular frame $L$‎, ‎and give some properties of them‎. ‎Let $S^{-1}_{\mathcal{F}}\mathcal{R}(L)$ denote‎ ‎the ring of fractions of the ring $ \mathcal{R}(L)$‎, ‎where ${\mathcal{F}}$ is a ${\mathrm{coz}}$-filter on $L$ and‎ ‎$S_{\mathcal{F}}$ is a multiplicatively closed subset related to ${\mathcal{F}}$‎. ‎We show that $S^{-1}_{\mathcal{F}}\mathcal{R}(L)$‎ ‎may be realized as the direct limits of the subrings $\mathcal{R}(A)$‎, ‎where‎ ‎$A\in‎ \{‎\mathfrak{o}_L\big({\mathrm{coz}}(\alpha)\big)‎ ‎\colon \alpha\in S_{\mathcal{F}}\}$‎. ‎Also‎, ‎we show that ${\mathrm{Q_{cl} }}\mathcal{R}(L)=\mathcal{R}(L)$, ‎if and only if‎ ‎$\mathcal{R}(L)$ is a special saturated ring‎.