Corneal Sensation after DSAEK

Changes in Corneal Sensation, Epithelial Damage, and Tear Function after Descemet Stripping Automated Endothelial Keratoplasty

Hirayama Y, Satake Y, Hirayama M, et al. Cornea 2013; 32:1255-1259

This prospective study aimed to compare ocular surface changes in 31 eyes of 28 patients following Descemet stripping automated endothelial keratoplasty (DSAEK) to those in 15 disease-matched eyes of 15 patients following penetrating keratoplasty (PKP). Main outcome measures were corneal epithelial integrity by fluorescein staining score, corneal sensation by Cochet-Bonnet aesthesiometry, and tear function by Schirmer test, tear clearance test, tear function index, and tear break-up time.

Results showed a significantly higher postoperative fluorescein staining score in the PKP group compared to the DSAEK group (P=0.02). Postoperative corneal sensation was significantly better in the DSAEK group compared to the PKP group (P<0.01). Corneal sensation was significantly improved following DSAEK compared to preoperatively (P=0.02). No statistically significant change was found in tear function before and after surgery in either group, and no significant differences were found between the groups after surgery.The authors conclude that, compared to PKP, DSAEK preserves corneal sensation and epithelial damage is less severe; and that the preservation of corneal sensation may contribute to early recovery of visual function and long-term maintenance of ocular surface health after DSAEK.My comment:

Why have corneal specialists in New Zealand enthusiastically adopted lamellar transplantation, and DSAEK in particular? You will be aware by now of some significant disadvantages – dislocation of the donor button, final BCVAs not quite so good as penetrating grafts (due to interface scarring) and higher failure rates. Our enthusiasm is based on the real advantages – faster recovery times, dramatically better postoperative refractions, fewer patients needing RGPs to get good vision, no sutures, a much stronger globe etc. These are very important, particularly in elderly patients. This paper demonstrates a further advantage and one we intuitively know. The ocular surface is better. DSAEK will never replace PK and DMEK may in time replace DSAEK but transplanting just the component that has failed is the future.


Chill out to reduce itching

Effectiveness of Nonpharmacologic Treatments for Acute Seasonal Allergic Conjunctivitis

Bilkhu PS, Wolffsohn JS, Naroo SA, et al. Ophthalmology 2014; 121:72-78

It is often suggested that artificial tears (ATs) and cold compress (CC) can be used as treatment options for acute seasonal allergic conjunctivitis (SAC), but the authors of this study could not find any evidence relating to the efficacy of it in scientific literature. This randomised, masked clinical trial of 18 subjects investigated the use of artificial tears and cold compresses, alone or in combination, in the relief of acute SAC, and whether they are as effective as, or could enhance, topical antiallergy medication. An environmental chamber was used to control the exposure of the subjects to grass pollen in order to stimulate an ocular allergic reaction. Treatment was with ATs, 5 minutes of CC, ATs combined with CC, or no treatment, applied randomly at each visit. 11 of the patients also had epinastine hydrochloride (EH) applied alone or in conjunction with CC, or saline control. EH is a topical antihistamine-mast cell stabiliser for the treatment of SAC. Main outcome measures were bulbar conjunctival hyperaemia, ocular surface temperature, and ocular symptoms repeated before and every 10 minutes after treatment for one hour. Results showed that all main outcome measures improved faster with nonpharmacologic treatments compared with no treatment (P<0.05). ATs combined with CC reduced hyperaemia more than other treatments (P<0.05). The treatment effect of EH was enhanced by combining it with CC (P<0.001). CC combined with ATs or EH lowered the antigen-raised ocular surface temperature to less than the pre-exposure baseline. ATs instillation alone, and ATs or EH combined with CC, significantly reduced ocular surface temperature (P<0.05). CC combined with ATs or EH had a similar cooling effect (P>0.05). At all measurement intervals, both EH and EH combined with CC reduced symptoms more effectively than with ATs or CC alone or in combination.

The study concludes that treatment with ATs combined with CC shows a therapeutic effect on the signs and symptoms of stimulated allergic conjunctivitis, and is more effective than EH alone. EH combined with CC was the only treatment to reduce symptoms to baseline within one hour of antigenic challenge.

My comment:

When a patient has an attack of acute allergic conjunctivitis they benefit from the instillation of any eyedrop, be it lubricant or anti-allergy, and the effect seems to be more than just ‘rinsing’. A number of ocular allergy studies have shown that ATs may have a ‘drug effect’ because ATs physically reduce the binding of allergens to the ocular surface. In this study, after an hour of treatment with AT combined with CC, most patients fell into the “hardly troubled at all” category. Even though pharmacologic therapy combined with CC was more effective, most patients will find almost as much relief from the use of just ATs combined with CC. For many people less is more –artificial tears rule! Patients with allergies should have some in the fridge.


Does the capsulorrhexis impact the outcome?

Effect of Centration and Circularity of Manual Capsulorrhexis on Cataract Surgery Refractive Outcomes.

Okada M, Hersh D, Paul E, van der Straaten D. Ophthalmology 2013; :1-8. Article in press.

This prospective, observational study of 113 eyes from 108 patients undergoing routine phacoemulsification cataract surgery with manual continuous curvilinear capsulorrhexis aimed to determine if postoperative refractive outcome is related to centration or circularity of the capsulorrhexis. One month and one year post surgery patients were refracted then digital retroillumination photographs were obtained and the capsulorrhexis parameters were analyzed using computer software. The main outcome measures were postoperative spherical equivalent (SE) deviation from predicted refraction and postoperative spectacle cylinder.

Results showed that at one month, mean capsulorrhexis circularity index was 0.83+0.01mm and mean decentration was 0.30+0.14mm. At both one month and one year there was no significant correlation between any of the refractive outcomes and either circularity or decentration. An association was found between capsulorrhexis decentration and change in postoperative SE from one month to one year: in eyes with more than 0.4mm decentration 56% had a change in SE of more than 0.25D compared with 30% having the same change in eyes with 0.4mm or less decentration (P=0.04). In eyes with incomplete capsulorrhexis-optic overlap, 60% had a change in spectacle cylinder of more than 0.50D from one month to one year, compared with 15% of eyes with complete overlap (P=0.004)

The authors conclude that at one year postoperative refraction was not related to centration or circularity of the manual capsulorrhexis, but that decentration of more than 0.4mm was asociated with a 0.25D change in SE; and that incomplete capsulorrhexis-optic overlap was associated with a 0.50D change in spectacle cylinder from one month to one year.

My comment:

Optometrists are increasingly being asked to consider whether their patients should be referred to a surgeon performing femtosecond laser-assisted cataract surgery (FLACS) as opposed to standard phacoemulsification. One of the selling points of FLACS is that it can create a perfect capsulorrhexis. This study does not compare outcomes between the two methods of creating the capsulorrhexis, but it does illustrate the fact that manual capsulorrhexis results in a high degree of capsulorrhexis circularity and very predictable and stable refractive outcomes. A perfect rhexis on the day is no guarantee it will still be circular in the months and years to come. As more research is published comparing the two methods we will gain a clearer picture as to whether or not any real advantage is gained from laser-assisted as opposed to manual cataract surgery IN THE LONG TERM.


Topical 0.05% Cyclosporine A for VKC

Tear Cytokine Levels in Vernal Keratoconjunctivitis: The Effect of Topical 0.05% Cyclosporine A Therapy

Oray M and Toker E. Cornea 2013; 32:1149-1154

This prospective, nonrandomized, noncontrolled and nonmasked study (due to the unethical nature of placebo treatment of a group of children in the active phase of VKC) looked at 21 patients with active VKC and 15 healthy volunteers. Treatment was with topical 0.05% cyclosporine A (Restasis; Allergan). Signs and symptoms were scored on the day of study enrollment, at month one and month three. Tear and serum samples were collected before treatment and at month three to measure a variety of interleukins, eotaxin, tumour necrosis factor alpha (TNFa), and interferon gamma (IFN-g).

Results showed that at the end of months one and three there was a statistically significant decrease in signs and symptoms (P<0.0001). VKC patients had significantly higher levels of Tear IL-2, sIL-2R, IL-9, IL-17, IFN-g and eotaxin compared to control patients (P<0.05), and also tended to have higher levels of IL-3, IL-4, IL-5 and TNFa. Compared to before treatment, there was a significant reduction in tear levels of IL-4, IL-5, IL-17, TNFa, IFN-g, and eotaxin (P<0.05). There was also a tendency to lower levels of IL-2 and sIL-2R compared to before treatment.The study concludes that topical 0.05% cyclosporine A is effective in the treatment of VKC and likely achieves its therapeutic effect by decreasing the local production of some inflammatory mediators in tears.My comment:

VKC is a terrible disease. Patients are primarily children and young adults who need treatment for many years. Steroids are often required and any agent that is ‘steroid-sparing’ is welcome. For a while we used 0.5-2.0% cyclosporine specially prepared as an oil-based solution by a compounding pharmacy. It was expensive and had side effects of lid skin maceration, blurring, burning and stinging. This study shows that commercially available Restasis is effective, and this is consistant with our clinical experience in New Zealand. The down side is that it too is expensive as we need to import it from Australia and it takes two months to determine the clinical effectiveness.


New findings for an old disease

New Findings for an Old Disease: Morphological Studies on Pseudoexfoliation Syndrome-Related Keratopathy and Binocular Asymmetry

Zheng X. Cornea 2013; 32(Suppl):S84-S90

This paper reviews previous studies that examined the morphology of the cornea in pseudoexfoliation syndrome (PEX) and the anatomical differences between PEX and the contralateral eye in unilateral PEX, and normal age- and gender-matched control eyes.

In one of the studies, in vivo confocal microscopy (IVCM) was used to determine cell densities in different corneal layers of unilateral PEX eyes and their clinically normal contralateral eyes, comparing the results to normal control eyes. Nerve densities and tortuosity in the subbasal layer were also analysed, correlating morphological changes to corneal sensitivity in the eyes with PEX. PEX eyes had decreased corneal cell density and significantly decreased density of the subbasal nerve plexus with increased tortuousity compared to normal control eyes. Pleomorphisms and polymegathisms of endothelial cells were imaged. The morphological changes were similar in contralateral PEX eyes and correlated to decreased corneal sensitivity in PEX eyes.

Anterior segment ocular coherence tomography (AS-OCT) was used to study the anterior segment morphology of PEX eyes and clinically normal contralateral eyes in unilateral PEX, and normal control eyes, analysing images taken under light and dark conditions to measure pupillary dilation and constriction, angle morphology and iris configuration. PEX eyes were shown to have a significantly shallower anterior chamber and decreased anterior chamber angle during light-induced pupillary constriction.

Noncontact IVCM was also used to observe PEX material on the lens surface and pupillary border of eyes with unilateral PEX. Results showed that the iridolenticular contact distance (ILCD) was significantly greater in PEX eyes compared to contralateral eyes.

The results of a small-scale Japanese national survey on the etiology of patients with bullous keratopathy who underwent keratoplasty from 2008 to 2010 were also discussed. The survey showed increased incidence of PEX endotheliopathy as the cause of unknown bullous keratopathy.

The paper concludes that PEX keratopathy involves all corneal layers and that morphological changes of the anterior chamber may contribute to PEX progression and that contralateral PEX eyes were at a subclinical stage of the PEX process. They also conclude from the survey that PEX endotheliopathy is responsible for an increased incidence of bullous keratopathy in Japan.

My comment:

This interesting paper adds to the existing body of knowledge about PEX and provides the first evidence that subbasal nerve abnormalities are responsible for decreased corneal sensitivity in PEX. The identified morphological changes occurring in PEX may prove to be valuable in the early diagnosis and prognosis of PEX patients, and AS-OCT has the potential to aid in this in a clinical setting. Given that PEX can result in glaucoma, the anatomical changes that occur suggest that cataract surgery could aid in the prevention or slowing of progression of pseudoexfoliative glaucoma. Cataract surgery may therefore be indicated in cases of PEX, despite the risks of cataract surgery in the presence of PEX-weakened lens zonules.