The quantitative assessment of alterations in lens transparency after transconjunctival 27-gauge microincision vitrectomy surgery.

PurposeTo evaluate the baseline and post-vitrectomy lens densitometry values by a Scheimpflug camera in eyes with epiretinal membrane that were treated with 27-G microincision vitrectomy surgery (MIVS) without tamponade and to compare the results with those in fellow healthy eyes.Patients and methodsProspective case series. The lens densitometry measurements of 24 patients, who underwent 27-G MIVS without any tamponade for the treatment of epiretinal membrane, were taken preoperatively and on the first week, first month, and third month postoperatively with Pentacam HR-Scheimpflug imaging system.ResultsThe mean lens densitometry values at Zone 1 and average lens densitometry values significantly increased in the study eyes on the first month when compared with the preoperative values (P=0.011, P=0.033, respectively). Additionally, there were statistically significant differences regarding the mean lens densitometry values of Zone 1 and Zone 2, and also average lens densitometry values between the preoperative and third month postoperative values (P=0.003, P=0.021, P=0.009, respectively). However, the densitometry values of fellow eyes were similar at preoperatively and all the postoperative follow-up periods (P>0.05 for all).ConclusionsThis study suggests that 27-G MIVS might cause post-surgical lens density changes even in early postoperative months and vitreous may play an important role in protecting the transparency of the lens.

Crab claw pattern on corneal topography: pellucid marginal degeneration or inferior keratoconus?

PurposeTo evaluate the topographic, tomographic, and densitometric properties of patients with pellucid marginal degeneration (PMD) and inferior keratoconus.Patients and methodsRetrospective, comparative case series. Forty-seven eyes of 32 patients with crab claw patterns were identified from 2751 patients with corneal ectasia. They were divided into two groups, inferior keratoconus and PMD, based on clinical findings. The topographic, tomographic, and densitometric measurements were analyzed.ResultsPMD was detected in 11 eyes of eight patients (mean age 50.2±11.1 years), and inferior keratoconus was detected in 36 eyes of 24 patients (mean age 34.7±10.1 years). The control group consisted of 40 patients (33.1±4.6 years). The thinnest corneal point and maximum anterior and posterior elevation points were located lower in the PMD than in the inferior keratoconus (P<0.01). In the PMD, all deviation indices were higher than the controls (P<0.01), whereas the deviation indices, except Dt (P=0.960), were lower than the inferior keratoconus (P<0.01). The densitometry values of PMD were significantly higher than those of the controls in all zones and layers (P<0.01) and significantly higher than the densitometry values of inferior keratoconus in the 6-10 and 10-12 mm zones (P<0.05).ConclusionThere is a higher probability of a patient with crab claw pattern on the topography of having inferior keratoconus than having PMD. Therefore, analyzing only the anterior corneal surface is not sufficient in differential diagnosis. Tomographic and densitometric evaluations may facilitate the differential diagnosis.