Surgical solution for presbyopia?
Small-aperture corneal inlay for the correction of presbyopia: 3-year follow-up.
Seyeddain O, Hohensinn M, Riha W, et al. J Cataract Refract Surg. 2012; 38:35-45
This prospecitve, non-randomized, non-comparative cohort study examined the three-year postoperative safety and efficacy outcomes of the Acufocus corneal inlay for presbyopia. Thirty-two naturally emmetropic presbyopic patients were selected to have the inlay implanted into the non-dominant eye. At three years compared to preoperatively, the mean uncorrected near visual acuity (UNVA) improved from J6 to J1 and the mean unaided intermediate visual acuity (UIVA) improved from 20/40 to 20/25. At three years, 97% of eyes had UNVA of J3 or better and 91% had UIVA of 20/32 or better. All patients achieved unaided distance visual acuity (UDVA) of 20/32 or better, with a mean of 20/20. Nine eyes (28.3%) lost one line of corrected distance VA (CDVA), one eye (3.1%) lost more than two lines (3.8 lines), and three eyes (9.3%) gained one line. At three years, 15.6% of patients reported severe night vision problems. Preoperatively, 87.5% of patients reported dependence on reading glasses compared to 6.3% at three years. No inlays were removed and there were no inflammatory reactions observed.
I’m now old enough to know how horrible presbyopia can be. Corneal inlays are a possible solution but one that at this point I would not be rushing to have done. Indeed the cornea is intuitively the wrong place to treat presbyopia. Proponents will argue that this is old data and that modifications already made to the device and technique will improve the results. One would hope so. No one would accept these outcomes from any other surgical procedure. The concept of dominant eye is flawed, the view through a pinhole is not the same as through a lens and the rate of severe night vision problems is simply unacceptable. Local Australasian experience is that 25% of patients get no benefit. The ultimate solution for presbyopia remains elusive.
Cosmetic conjunctivectomy complications
Complications of cosmetic wide conjunctivectomy combined with postsurgical mitomycin C application.
Rhiu S, Shim J, Kim EK, et al. Cornea. 2012; 31:245-252
This retrospective review of the medical records of 48 consecutive patients receiving cosmetic wide conjunctivectomy with postsurgical topical mitomycin C (MMC) aims to raise awareness about the risk of severe complications following this treatment. The results of the review show that 91.67% (44/48) of treated patients developed complications following the treatment. Twenty-two patients developed chronic conjunctival epithelial defects; nineteen patients developed scleral thinning with calcified plaques, two without; fifteen patients developed fibrovascular conjunctival adhesion at the muscle insertion site; eleven patients developed chronic dysfunctional tear syndrome; ten developed avascular zones; nine developed diplopia; five developed abnormal vessel growth; three developed lymphangiectasis; one developed adhesions of Tenon’s capsule and the conjunctiva at the extraocular muscle insertion site; and one developed extraocular muscle fibre exposure. Three patients had to undergo strabismus surgery for incomitant esotropia. Eight patients had to undergo calcified plaque removal because of severe progression of the calcification. Five patients had to undergo conjunctival flap operation because of severe progressive scleral thinning.
I include this review because eye ‘whitening’ is a hot topic in some countries and may come up here. This treatment essentially achieves a white eye by destroying episcleral and conjunctival vessels. It probably also destroys goblet cells and limbal stem cells.
This paper comes as no surprise to pterygium surgeons. In simple terms MMC is very damaging if applied to bare sclera. It may limit pterygium regrowth if applied after a free conjunctival graft has healed and is very useful in glaucoma surgery and in the treatment of OSSN.
Corneal thickness and IOP correction
The effect of thin, thick, and normal corneas on Goldmann intraocular pressure measurements and correction formulae in individual eyes.
Park SJK, Ang GS, Nicholas S, Wells AP. Ophthalmol. 2012; 119:443-449
This retrospective case series examined 289 patients who attended a specialist glaucoma practice and aimed to evaluate the usefulness of the central corneal thickness (CCT)-based correction formulae for stratified CCT groups. Both normal subjects and those with confirmed glaucomatous optic neuropathy were included. IOP was measured using the Pascal dynamic contour tonometer (PDCT) as the reference standard, Goldmann applanation tonometry (GAT) and the Ocular Response Analyzer (ORA; Reichert Corp, Buffalo, NY). GAT readings were adjusted for CCT using four different correction formulae, stratified into thin, intermediate and thick CCT groups and discrepancies between GAT and CCT-corrected GAT were evaluated. All IOP measurements were compared against PDCT IOP measurements using Bland-Altman analysis. Average PDCT IOP values measured about 2.2 mmHg higher than GAT. The GAT IOP readings demonstrated poor agreement with PDCT IOP (+ 4.7 mmHg; 95% limits of agreement). Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), and adjustment of GAT IOP with CCT-based formulae resulted in even poorer agreement (+ 5.1 to 6.7 mmHg; 95% limits of agreement). This gave a 26% to 39% risk of making an erroneous IOP adjustment of 20% or more at all levels of CCT, with the greatest risk in the patients with thicker corneas (CCT > 568μm). PDCT is considered the closest measure we have to intracameral IOP. The authors conclude that CCT may be useful in population studies but CCT-based correction formulae should not be applied to individuals.
There is widespread belief that overestimation of IOP by GAT in patients with thicker corneas may result in unnecessary treatment, while underestimation of IOP by GAT in patients with thinner corneas may result in treatment delay. PDCT claims to measure IOP independent of corneal structural properties, whereas GAT assumes certain corneal structural properties.
This study showed that the correlation between PDCT and GAT was poor, and even worse if IOP was adjusted for CCT, particularly in those with thicker corneas. The results from this study showed that adjusting GAT IOP in patients with thicker corneas may underestimate actual IOP, leading to delayed treatment.
As the paper below reminds us IOP is the least reliable measure of ‘glaucoma’.
Does adjusting IOP improve POAG prediction?
Adjusting intraocular pressure for central corneal thickness does not improve prediction models for primary open-angle glaucoma.
Brandt JD, Gordon MO, Gao F, et al. Ophthalmol. 2012:119:437-442
This study is a re-analysis of the baseline prediction model for the development of POAG from the Ocular Hypertension Treatment Study (OHTS) substituting IOP adjusted for central corneal thickness (CCT) using five different correction formulae for unadjusted IOP. It examined the data of 1433 participants with a separate Cox proportional hazards model using IOP adjusted for CCT for each of the five formulae. Each model was run including and excluding CCT. The predictive accuracy of each model was assessed using the c-statistic and calibration chi-square. The results demonstrated that c-statistics for prediction models that used adjusted IOP ranged from 0.75-0.77 for the formulas. This is similar to the original baseline prediction model (0.77) that did not adjust IOP for CCT. Baseline IOP was statistically significant in all models, adjusted for CCT or not. This study concludes that the calculation of individual risk for developing POAG in ocular hypertension is simpler and equally accurate using IOP and CCT as measured, rather than applying an adjustment formula to correct IOP for CCT.
This paper adds weight to the argument that CCT itself is a risk factor for POAG, as it acts as a “biomarker for structural or physical factors involved in the pathogenesis of POAG”. So while CCT should be considered when assessing POAG risk, it is not necessarily the influence of CCT on IOP measurement we should be concerned about, but rather we should be considering CCT a risk factor in itself.
The authors direct us to a glaucoma risk calculator at http://ohts.wustl.edu/risk which is available as a free download and allows a five year risk of developing POAG to be calculated from age, IOP, CCT, VCDR (vertical cup-to-disc ratio) and PSD (pattern standard deviation).
Intraocular lenses for presbyopia correction: past, present, and future.
Lichtinger A and Rootman DS. Curr Opin Ophthalmol. 2012; 23: 40-46.
Current understanding of conventional outflow dysfunction in glaucoma.
Stamer WD and Acott TS. Curr Opin Ophthalmol. 2012; 23:135-143.
Femtosecond phacoemulsification: the business and the medicine.
Uy HS, Edwards K, and Curtis N. Curr Opin Ophthalmol. 2012; 23: 33-39.