Which presbyopia-correcting IOL is best?
Comparison of through-focus image sharpness across five presbyopia-correcting intraocular lenses.
Pepose JS, Wang D and Altmann GE. Am J Ophthalmol. 2012; 154:20-28
This paper compared the through-focus image sharpness of the Crystalens AO (AO), Crystalens HD (HD), aspheric ReSTOR +4 (R4), aspheric ReSTOR +3 (R3), and Tecnis Multifocal Acrylic (TMF) IOLs using a model eye and digital image capture for combinations of pupil diameter and object vergence. Image sharpness was scored objectively. Results showed that the AO IOL had the best distance image sharpness for all pupil diameters. The TMF IOL showed the best near image sharpness for all pupil diameters, and consistent distance and near image sharpness across pupil diameters. The R4 and HD distance image sharpness was similar with a 5mm pupil. The TMF distance image sharpness was better than the HD, R3 and R4 with a 6mm pupil. The R3 did not improve image sharpness at intermediate distance compared to the R4. The R3 near and distance image sharpness was worse compared to the R4. As pupil diameter increased, the R3 and R4 IOLs demonstrated better distance and poorer near image sharpness. The study concludes that the different IOL designs offer different image sharpness at various distances and pupil sizes. This information could be helpful when selecting the most appropriate presbyopia-correcting IOL for individual patients.
At the recent Australasian Society of Cataract and Refractive Surgeons conference in Queenstown delegates reported using multifocal IOLs in up to 80% of all cataract operations! Multifocal IOLs have come of age.
This is a lab bench study but it does highlight that using presbyopia-correcting IOLs involves tradeoffs between factors such as image quality at any given distance or pupil diameter, night glare, depth of focus, contrast sensitivity and so on. Clinical studies give somewhat different results but the paper illustrates that understanding each patient’s visual needs and careful patient selection are paramount for good outcomes.
Do hot compresses damage the cornea?
The role of heat in rubbing and massage-related corneal deformation.
McMonnies CW, Korb DR and Blackie CA. Cont Lens Ant Eye. 2012; 35:148-154
This review looks at the role of raised corneal temperature in the development of rubbing or massage-related corneal deformation. Eyelid massage is often prescribed in cases of meibomian gland dysfunction (MGD), chalazion, dacryocystoceles etc, and the treatment is often combined with the application of warm compresses or other forms of heat. There are reports of rubbing-induced corneal deformation in the literature. Lid massage itself has been shown to elevate corneal temperature via heat transfer from the lids to the cornea and prevention of heat dissipation that normally occurs under open-eye conditions. Massage is known to cause transient corneal astigmatism and temporary visual blur, while 45deg warm compresses have been shown to induce transient visual blur without significant corneal topographical change. The mechanism by which massage and elevated corneal temperature induces deformation may be biomechanical effects on the corneal collagen structure, enzymatic effects, effects of transient IOP elevation, or compound trauma if the cornea is not allowed to recover between massage periods. The review concludes that there is a risk of corneal deformation in patients whose management involves heat or ocular massage, and that these patients may require screening and monitoring for corneal deformation with corneal topography, and careful tutoring in modified ocular massage techniques to minimize the risk of corneal deformation.
This paper reminds us that every treatment, no matter how ‘natural’ can have side effects. It makes sense to be careful when prescribing heat for patients at high risk of corneal deformation (keratoconus/corneal graft/patients with corneal thinning etc) and make sure that they do not use very hot temperatures for prolonged periods.
Automated MGD treatment – better than manual therapy?
A single LipiFlow Thermal Pulsation System treatment improves meibomian gland function and reduces dry eye symptoms for 9 months.
Greiner JV. Curr Eye Res. 2012; 37(4):272-278
This study investigated the effect of a single 12-minute LipiFlow Thermal Pulsation System treatment on the signs of meibomian gland dysfunction (MGD) and dry eye symptoms from baseline (pre-treatment) and at one month and nine months post-treatment. The LipiFlow device simultaneously applies heat and pulsatile pressure to the eyelid surfaces to encourage meibomian gland expression. The Ocular Surface Disease Index (OSDI) and Standard Patient Evaluation for Eye Dryness (SPEED) questionaires were used to evaluate patient symptoms; the dry eye test (DETTM) was used to measure tear break-up time (TBUT); and a standardised diagnostic expression technique was used to evaluate meibomian gland function at baseline, 1 month and 9 months post-treatment. Results showed that symptom scores improved significantly at 1 month post-treatment (p<0.0001) and were maintained at 9 months post-treatment. TBUT was 4.8 + 3.2 at baseline and significantly improved at 1 month (9.6 + 7.6; p<0.001) and maintained at 9 months with no significant regression (7.1 + 5.6). Meibomian gland secretion scores improved significantly from baseline (4.4 + 4.0) to 1 month post-treatment (11.3 + 6.2; p<0.0001) and this was maintained at 9 months with no significant regression (11.7 + 5.9). The study concludes that a single 12-minute LipiFlow treatment offers up to 9 months of sustained improvement in meibomian gland function, TBUT and dry eye symptoms that is not currently offered with other dry eye treatments. My comment:
Despite widespread use, there’s limited proven effectivity in the treatment of MGD with warm compresses, especially in severe forms of the disease. Repeated manual expression of the glands by an optometrist/ophthalmologist or self-expression can be beneficial, but it’s time-consuming and also difficult to quantify a “safe” level of compressive force to use on the eyelids.
The LipiFlow device is attractive as it ensures a constant eyelid temperature, sheilds the cornea from heat and exerts an even pressure on the meibomian glands. In contrast to manual expression it treats both the upper and lower eyelids. It certainly appears to be an effective treatment but at this point in time is still very costly and time-consuming as it’s a device designed to be used in a professional setting.
I still like manual expression with cilia forceps as it allows me to assess what is in each meibomian gland, how much force to apply to each part of the lid (e.g. long and gentle pressure is generally best when secretions are most waxy) and most importantly when to stop. In general it takes about 3 minutes to do both lower lids. In some patients we use the Blephasteam device for 10 minutes before manual expession to soften the meibomian gland secretions. I do find it hard to believe that a single LipiFlow treatment could provide sustained relief for nine months. My patients with moderate and severe MGD usually come in every 4 -8 weeks.
Faster, safer relief for chronic dry eye sufferers?
Efficacy of combined 0.05% cyclosporine and 1% methylprednisolone treatment for chronic dry eye.
Byun Y, Kim T, Kwon SM, Seo KY, et al. Cornea. 2012; 31:509-513
This study aimed to compare the efficacy of topical cyclosporine 0.05% (tCsA) and combined treatment with 1% methylprednisolone acetate for the treatment of moderate-to-severe chronic dry eye of 44 patients who had not responded to conventional treatment. 21 of these (Group 1) were given the steroid and tCsA for the initial 3 weeks, and tCsA only thereafter; 23 (Group 2) were given tCsA only. Before treatment and at 1, 2 and 3 months after treatment symptom scores, tear break-up time (TBUT), Schirmer scores and corneal and conjunctival fluorescein staining were assessed. Before treatment and at 3 months after treatment proinflammatory factors, interleukin-6 (IL-6) and interleukin-8 (IL-8) concentrations were measured in the tears. Results showed a significant improvement at 1 month compared to baseline in group 1 (all P<0.001), and the same with a few exceptions in group 2 (P = 0.002 on Schirmer, P = 0.267 on corneal staining). Greater improvements in symptom scores, Schirmer scores, and corneal staining were observed for group 1 compared to group 2 at 1 month (P < 0.001, P = 0.039, P = 0.01 respectively). There were no significant differences between group 1 and 2 in TBUT and conjunctival staining (P = 0.277 and P = 0.254 respectively) at 1 month. Symptom relief was achieved in a shorter time interval for group 1 compared to group 2. Both groups showed decreased IL-6 and IL-8 concentrations at 3 months compared to baseline (P < 0.05), but the between-group difference was not significant. The study concludes that tCsA appears to be a safe and effective treatment for moderate to severe dry eye and that symptom relief and improved signs may be achieved faster for these patients with the short-term addition of topical steroid to their tCsA treatment regime. My comment:
This is a great study that confirms what most external disease specialists already know. Tear dysfunction is often associated with ocular surface inflammation even if the eye is white. I always prescribe a short course of steroids, typically Predsol Minims, to assess if inflammation is present. Patients who improve usually also respond to Restasis although it can take a few months to have an effect. This delay, together with the high cost in New Zealand, may affect compliance with initial therapy. Continuing steroid treatment while the cyclosporine takes effect is a very wise strategy. In the end you use less steroid overall.
What do contact lenses do to your eyelids?
Long term effects of the daily wear of senofilcon A silicone hydrogel contact lenses on eyelid tissues.
Gillon M & Maissa C. Cont Lens Ant Eye. 2012;35: 112-117
This prospective study investigated the effect of two years of wear of Acuvue Oasys with Hydraclear Plus (Senofilcon A) on the eyelid physiology of current contact lens wearers, lapsed wearers and neophytes. 90 subjects enrolled in the study, of which 64 completed the study. Results for current non-wearers showed significantly lower lid hyperaemia (p < 0.001) and no difference in papillae (p = 0.078) after two years of wear compared to baseline. For established current wearers , both lid hyperaemia (p < 0.001) and papillae (p = 0.001) were significantly lower after two years of wear compared to baseline. The study concludes that senofilcon A worn on a daily wear, fortnightly replacement basis either does not change, or may slightly improve, the physiology of eyelid tissues. My comment:
I’ve included this paper because I want to highlight that everything we do to the external ocular surface and anterior segment has the potential to drive changes in the eyelid. LASIK, corneal transplants and contact lens wear are all common causes.
The authors point out that most studies that have found contact lens-induced eyelid changes have investigated extended wear of the lenses, yet daily wear of contact lenses is the most common modality. We also have to remember that although all silicon hydrogel contact lenses contain silicon, they also all consist of different materials, modulus, design, surface treatments and so on, and so we can expect every different silicon hydrogel contact lens to have different effects on the lid tissues. Senofilcon A is a low modulus contact lens with a low coefficient of friction on-eye so the studies results cannot necessarily be extrapolated to other silicon hydrogel contact lenses. The paper seems to show that Oasys lenses do not damage eyelid tissues, but may in fact improve some aspects of eyelid physiology. Too good to be true? The study was supported by Johnson & Johnson Vision Care, Inc. Always good to stay a little cynical!
The lid wiper contains goblet cells and goblet cell crypts for ocular surface lubrication during the blink.
Knop N, Korb DR, Blackie CA and Knop E. Cornea. 2012; 31:668-679.