Retinal phakomatosis and Von Hippel-Lindau peripheral capillary hemangioblastoma: proposal for staged surgery.

PURPOSE: Retinal capillary hemangioblastoma (RCH) is present in about half of the carriers of the VHL (von Hippel-Lindau) gene mutation and can lead to the evolution of blindness. Herewith is a proposal for surgical intraretinal feeder vessel ligature to induce ischemia the phakoma and to resolve the exudative secondary retinal detachment, with satisfying results at the 6 months follow-up end point. METHODS: The patient underwent a chandelier-assisted 23 G pars plana vitrectomy with valved trocars. A bimanual transretinal ligature of the hemangioblastoma's feeder vessel was performed, followed by localized endolaser to ablate the surrounding retina and capillaries, and a Polydimethylsiloxane 1000 (PDMS 1000) final tamponade. After 3 months, exchange PDMS/air/balanced salt solution (BSS), phacoemulsification, and in-the-bag intraocular lens (IOL) implantation were performed. RESULTS: At sixth month, fundus fluorescein angiography (FFA) showed a significant reduction of blood flow in the phakoma. Final best-corrected visual acuity (BCVA) was 6/6 (9 lines gain obtained compared to the baseline time). CONCLUSIONS: This surgical technique seems to be effective and promising for the treatment of VHL retinal capillary hemangioblastomas and their related retinal complications.

Excess Absorbance as a Novel Approach for Studying the Self-Aggregation of Vital Dyes in Liquid Solution.

In the present paper, a simple method for analyzing the self-aggregation of dyes in a solution by a UV-visible absorption measurements is proposed. The concept of excess absorbance is introduced to determine an equation whose coefficients determine the parameters of the aggregation equilibrium. The computational peculiarities of the model are first discussed theoretically and then applied to sodium fluorescein in polar protic and aprotic solvents, as well as in aqueous solutions of methylene blue, which is a cationic dye. Although the experimental responses are very different, the model appears to work equally well in both cases. The model reveals that the trimer is the most likely configuration in both solvents. Furthermore, aggregation is strongly favored for the protic solvent. Interestingly, the model establishes that in aqueous solutions of methylene blue, the tetramer is the predominant form, which has long been assumed and recently demonstrated with sophisticated computational techniques.

Intraocular Lens Power Calculation Without Corneal Parameters: A New Option.

OBJECTIVES: To compare different methods in calculating the corneal radius (R) to be used in case of intraocular lens power calculations when it is immeasurable. METHODS: The right eyes of 1,960 patients were randomly divided into 2 equal groups. The first group of right eyes (group A) was divided in three groups according to the axial length (AL) (≤21.99 mm, between 22 and 24.99 mm, and ≥25 mm). In these groups, the correlation between the AL and the corneal radius (R) provided three different regression formulas. The second group of right eyes (group B) was used to test the following methods of estimating the R: the regression formulas determined from group A, formula from Logan et al., formula from Stenström, the mean R calculated from group A, and the fellow eye group B. A Student paired T test was used for the statistical evaluation. RESULTS: In case of AL≤21.99, the best results have been obtained with the fellow eye R, followed by either the regression formula or the mean R from group A (mean=0.00±0.09 mm, P=0.94, mean=0.05±0.21 mm, P=0.05, mean=0.05±0.22 mm, P=0.08, respectively). In case of AL between 22 and 24.99 mm, the best results have been obtained with the fellow eye R, followed by either the regression formula or the mean R from group A (mean=-0.01±0.09 mm, P=0.38, mean=0.01±0.21 mm, P=0.12, mean=0.01±0.24 mm, P=0.18, respectively). In case of AL≥25 mm, the best results have been obtained with the fellow eye R, followed by either the regression formula or the mean R from group A (mean=-0.003±0.08 mm, P=0.94 mean=-0.004±0.25 mm, P=0.85, mean=-0.004±0.25 mm, P=0.85, respectively). CONCLUSIONS: The new calculated regression formulas seem to represent a reliable method to calculate the R when it is undetectable, as in case of corneal dystrophies.

Biometric Parameters and Corneal Astigmatism: Differences Between Male and Female Eyes.

PURPOSE: To evaluate the gender-related differences in demographic and ocular biometric trends in a defined population presenting for consultation within the Italian public health system and to collect data of several ocular parameters at different stages of life, highlighting the differences between females and males. PATIENTS AND METHODS: In this retrospective study, keratometry, corneal astigmatism, and axial eye length of 729 patients (729 eyes; mean age: 58±21 years; range: 18-96 years) were evaluated using partial coherence interferometry. Statistical evaluation was performed utilizing a paired t-test and R2 analysis. RESULTS: In females (396 eyes of 396 patients), mean keratometry ranged between 40.59-47.78 D (44.27±1.36 D), corneal astigmatism ranged between 0-3.82 D (1.13±0.74 D), and axial length ranged between 20.5-31.32 mm (24.07±1.74 mm). In males (333 eyes of 333 patients), mean keratometry ranged between 38.5-46.95 D (43.54±1.35 D; p<0.001), corneal astigmatism ranged between 0.1-3.97 D (1.15±0.79; p=0.75), and axial length ranged between 20.41-31.21 mm (24.57±1.78 mm; p<0.001). Both genders presented a shorter axial length in advanced age. Elderly males presented a higher percentage of against-the-rule astigmatism. CONCLUSION: Females may have steeper corneas and shorter eyes. A trend toward axial length reduction with age was observed in both genders. This finding is probably due to the difference in growth between generations, as the new ones have an higher size than the old ones.

How many aqueous humor outflow pathways are there?

The aqueous humor (AH) outflow pathways definition is still matter of intense debate. To date, the differentiation between conventional (trabecular meshwork) and unconventional (uveoscleral) pathways is widely accepted, distinguishing the different impact of the intraocular pressure on the AH outflow rate. Although the conventional route is recognized to host the main sites for intraocular pressure regulation, the unconventional pathway, with its great potential for AH resorption, seems to act as a sort of relief valve, especially when the trabecular resistance rises. Recent evidence demonstrates the presence of lymphatic channels in the eye and proposes that they may participate in the overall AH drainage and intraocular pressure regulation, in a presumably adaptive fashion. For this reason, the uveolymphatic route is increasingly thought to play an important role in the ocular hydrodynamic system physiology. As a result of the unconventional pathway characteristics, hydrodynamic disorders do not develop until the adaptive routes cannot successfully counterbalance the increased AH outflow resistance. When their adaptive mechanisms fail, glaucoma occurs. Our review deals with the standard and newly discovered AH outflow routes, with particular attention to the importance they may have in opening new therapeutic strategies in the treatment of ocular hypertension and glaucoma.

Can We Use the Fellow Eye Biometric Data to Predict IOL Power?

PURPOSE: To study the correlation between right (RE) and left eye (LE) keratometry readings (K) and axial lengths (AL) in a population-based sample of normal subjects. METHODS: In a cross-sectional retrospective study conducted at S. Giuseppe Moscati Hospital, Avellino, Italy, 4516 eyes of 2258 patients with a mean age of 67 ± 16.36 years (range 18-96 years) were included. Partial coherence interferometry data obtained in right (RE) and left (LE) eyes were analyzed and correlated. RESULTS: The average K was 44.01 ± 1.50 diopters (D) (range 39.09-49.89 D) in the RE and 44.04 ± 1.53 D (range 39.63-51.89 D) in the LE (p = 0.0075). 4.5% of the patients (101) presented with differences in the corneal power ≥ 1 D, corresponding to a difference of roughly 1 D in the IOL power. The average AL was 23.89 ± 1.77 mm (range 19.09-35.15 mm) in the RE and 23.84 ± 1.68 mm (range 19.23-35.04 mm) in the LE (p = 0.0018). 19.2% of the patients (433) presented with differences in the AL ≥ 0.4 mm, corresponding to a difference of roughly 1 D in the IOL power. CONCLUSIONS: In calculating the IOL power, we must be aware of these results when we measure the fellow eye to validate the measurements in the first eye. In the case of postcataract refractive error, the outcome could be used for the second eye only when symmetric biometric findings are present.

Some physicochemical remarks on spontaneous emulsification of vitreal tamponades.

The importance of gravitational instability in determining the emulsification of vitreal tamponades is discussed. Theoretical results and numerical simulations indicate that the spontaneous formation of water-silicon oil is a rare event and that the very low concentration of surface active agents cannot justify the systematic formation of emulsions. The gravitational instabilities seem to play the main role. Our theoretical results seem in agreement with the experimental evidences; furthermore they indicate a future research line for the improvement of endotamponades. Indeed, the use of biodegradable antifoam may avoid the formation of bubbles and delay the formation of emulsions.

Prevalence of corneal astigmatism before cataract surgery in Caucasian patients.

PURPOSE: To analyze and quantify the pattern of corneal astigmatism in patients awaiting cataract surgery to provide information for cataract surgeons and intraocular lens (IOL) manufacturers and to establish the demand for toric IOLs in a hospital. METHODS: This cross-sectional retrospective study evaluated keratometric (K) values measured by partial coherence interferometry (IOLMaster) in cataract surgery candidates, who were then analyzed and correlated by age and axial length (AL) ranges. RESULTS: The study evaluated the K values in 757 eyes of 380 patients with a mean age of 71.9 ± 10.2 years (range 33-96 years). The mean corneal astigmatism was 1.02 ± 0.69 D (range 0.06-4.57 D). It was 1 D or higher in 316 (41.74%) eyes. The mean AL was 23.56 ± 1.35 mm (range 20.53-31.86 mm). CONCLUSIONS: Our study shows that roughly 50% of the eyes have more than 1 D of astigmatism. The results can help hospitals plan and analyze the amount and costs of using toric IOLs in patients with corneal astigmatism.

Sutureless human sclera donor patch graft for Ahmed glaucoma valve.

PURPOSE: To report the safety and effectiveness of a sutureless human sclera donor patch graft covering the subconjunctival portion of glaucoma drainage implant tube to prevent its erosion throughout the overlying conjunctiva. METHODS: This was a prospective pilot study. Fifteen eyes of 15 consecutive patients not responsive to medical and to not-implant surgical glaucoma treatment underwent Ahmed glaucoma valve (AGV) implant surgery with sutureless human sclera donor patch graft. The surgical procedure included AVG implant placed 8 mm behind the corneal limbus and fixed to the sclera with two 9-0 black nylon sutures. The tube was passed through the scleral tunnel, parallel to the corneal limbus, and shortened at the desired length. The anterior part of the tube was covered with human donor scleral graft and kept in place with fibrin glue (Tissue Coll) under the conjunctiva. Examinations were scheduled at baseline and then at 1 week and 1, 3, 6, and 12 months after surgery. RESULTS: At 12-month follow-up, the best-corrected visual acuity did not significantly improve from baseline 0.78+/-1.2 logMAR, whereas mean intraocular pressure significantly decreased from preoperative values of 29.8 (SD 8.4) mmHg. In all cases, the scleral patch was found in place at each check during the follow-up period. No conjunctival erosion over the AGV tube nor sign of endophthalmitis was recorded at any time during the follow-up period. CONCLUSIONS: AVG implant surgery with sutureless human sclera donor patch graft represents an effective and relatively safe surgical procedure for complicated glaucomas, avoiding conjunctival erosions over the AGV tube.

E-PTFE (Gore-Tex) implant with or without low-dosage mitomycin-C as an adjuvant in penetrating glaucoma surgery: 2 year randomized clinical trial.

PURPOSE: To test the expanded polytetrafluoroethylene (ePTFE) as a new adjuvant in trabeculectomy. METHODS: Consecutive glaucoma surgical inpatients were observed at the Department of Ophthalmology of Palermo University. Sixty patients (60 eyes) were randomly assigned to undergo trabeculectomy (T), trabeculectomy with mitomycin-C (TMMC), with ePTFE (TG) or with mitomycin-C and ePTFE (TGMMC). Postoperative visits were scheduled at 24 hr, 7 days, 1, 3, 6, 12, 18 and 24 months. Complete success and qualified success were assessed at two target intraocular pressure (IOP) levels -< or =21 and < or =17 mmHg - by Kaplan-Meier curves. RESULTS: The postoperative IOP reduction was significant (P < 0.01) at the endpoint in all groups, with a mean IOP of 16.9 (+/-2.9), 16.2 (+/-2.7), 15.3 (+/-3.4) and 15.2 (+/-4.3) mmHg in T, TMMC, TG and TGMMC eyes, respectively. No intergroup difference was found at either IOP targets. The Kaplan-Meier curves relating to either the < or =21 mmHg or the < or =17 mmHg target IOP did not show significant intergroup differences for complete and qualified success rate. When ePTFE was used, a trend favouring the medium-term survival rate was noted. No adverse reaction to the ePTFE was present, and no membrane extrusion or conjuctival erosion were noted in any cases. Hypotony was significantly more frequent (P = 0.035) in groups without ePTFE. Moreover, the late MMC-related complications were more frequent when MMC was applied. CONCLUSION: Expanded polytetrafluoroethylene implant in trabeculectomy is well tolerated and could act as a filtration modulating device. Therefore, it is useful in reducing early hypotony-related complications and contributes to attaining medium-term IOP control that is comparable to the low-dosage MMC.