[Distinctive features of phacoemulsification in previously vitrectomized eyes]

The review presents the main pathogenetic mechanisms of cataract development in an avitic eye as well as anatomical and functional changes of the eye in the state of avitria. The authors have also analyzed distinctive behavior of such eyes during phacoemulsification and surgical techniques used to answer specific avitreal phenomena.

Optical biometry features in silicon oil filled eyes

Background. The article presents results of axial length (AL) measurement in eyes filled with silicone oil and in those without silicone oil with IOLMaster and Lenstar LS 900 optical biometry methods. Materials and methods. The anteroposterior axis was measured in 27 eyes of 27 patients with silicone oil tamponade after surgical treatment of several vitreoretinal conditions. Using IOLMaster, the AL of eyes without silicone oil tamponade varied from 21.99 mm to 29.38 mm, Lenstar LS 900 biometry gave results from 21.96 mm to 29.41 mm. Results. According to data obtained and to their distribution, all cases were divided into 2 groups: I group — eyes with AL less than 23.63 mm, and II group — eyes with AL more than 23.63 mm. In the group II, the disparity of consecutive measurements was reliable and amounted to 0.28 ± 0.46 mm (р = 0.024) for IOLMaster and 0.23 ± 0.44 mm (р = 0.029) for Lenstar LS 900. Conclusion. So AL values at IOLMaster and Lenstar LS 900 biometry of silicone oil filled eyes may significantly overestimate the real ones when exceeding 23.63 mm. In case of simultaneous phacoemulsification with IOL implantation, this could lead to hypermetropic shift of postoperative refraction. Lenstar LS 900 measurement error in silicon oil filled eyes is less than that of IOLMaster, thus making the first biometry method preferable. In eyes with AL shorter than 23.63 mm, the measurement difference was not reliable, thus the biometry accuracy in silicone oil filled “short” eyes becomes higher.

Phacoemulsification in Previously Vitrectomized Patients: An Analysis of the Surgical Results in 100 Eyes as well as the Factors Contributing to the Cataract Formation

Purpose

To evaluate the safety and effectiveness of phacoemulsification with clear corneal incision in previously vitrectomized patients as well as factors affecting the development time and type of cataract occurring after pars plana vitrectomy (PPV).

Methods

The authors conducted a prospective study of 100 consecutive eyes of patients who developed a cataract after PPV. Three groups were established based on the underlying vitreoretinal pathology. The main outcome measurements were intraoperative and postoperative complications and changes in best-corrected visual acuity (BCVA).

Results

The median interval between PPV and phacoemulsification was 11.5 months. Patients with proliferative diabetic retinopathy required phacoemulsification earlier (p=0.018). Posterior subcapsular cataracts developed more frequently in patients <50 years (73.7%, p=0.000) and affected those who underwent vitrectomy primarily for complicated retinal detachment (48.8%, p=0.046). Intraoperative complications included posterior capsular tears (4%), luxated nucleus into vitreous (2%), and zonular dialysis (5%). Postoperative complications were vitreous hemorrhage (6%), retinalredetachment (4%), pupillary synechiae (6%), ocular hypertension (4%), and Seidel phenomenon (3%). Posterior Nd:YAG laser capsulotomy was required in 44% of eyes. BCVA was improved in 85% of cases at the end of follow-up (median, 15.5 months). Twenty-one patients with one functioning eye (61.9%) demonstrated visual improvement compared with 79 patients with bilateral vision (91.1%; p=0.003).

Conclusions

The technique allows stable improvement in BCVA through long follow-ups. It is more risky than in nonvitrectomized eyes. The visual results after phacoemulsification in vitrectomized eyes seem to be limited by retinal comorbidity and surgical complications.

[Intraocular lens power calculation in silicone-filled eyes]

AIM

to evaluate the accuracy of different modified methods for axial length (AL) measurement in silicone-filled eyes.

MATERIAL AND METHODS

The study was conducted in a group of 60 patients (60 eyes) with silicone oil tamponade (Oxane 1300 cst). Axial length measurements were taken using IOL Master optical coherence biometry ('silicone-filled eye' mode) and modified A-scan ultrasound biometry (velocity of ultrasound passing through the vitreous body set at 980 m/s and 1000 m/s). After phacoemulsification and silicone oil removal, AL measurements were repeated on same devices switched to standard pseudophakia modes. The results were then compared to those obtained in modified modes before the surgery.

RESULTS

Preoperative axial lengths measured by A-scan at 980 m/s tended to be 0-1.5 mm (the median of 0.52 mm) shorter than those obtained after silicone oil removal. With 1000 m/s ultrasound velocity the error was much less--from 0 to 0.5 mm (the median of 0.15 mm). As for preoperative ALs by IOL Master in the 'silicone-filled eye' mode, they were 0-1.2 mm (the median of 0.3 mm) longer than postoperative ones.

CONCLUSIONS

In cases of impossibility or inaccessibility of optical biometry, measurements taken with an A-scan device set at 1000 m/s are sufficient. The true AL of an eye with silicone oil tamponade falls somewhere between the values obtained with 1000 m/s ultrasound and IOL Master in the 'silicone-filled eye' mode.